Id Family of Transcription Factors and Vascular Lesion Formation
http://www.100md.com
《动脉硬化血栓血管生物学》
From the Cardiovascular Division, Department of Internal Medicine and the Cardiovascular Research Center, University of Virginia, Charlottesville, Va.
ABSTRACT
Vascular smooth muscle cell (VSMC) modulation to a de-differentiated phenotype and proliferation are key components of vascular lesion formation. Understanding how these processes are regulated is essential to understanding the progression of vascular diseases such as atherosclerosis and in-stent restenosis. The Id family of helix-loop-helix (HLH) transcription factors has emerged as important regulators of cellular growth and differentiation. Recent published findings have implicated the Id proteins as important regulators of growth and phenotypic modulation in VSMC and in the vascular response to injury. In this review, we summarize what is known regarding how the Id proteins function to control cellular growth and differentiation and their role in vascular lesion formation.
The Id family of helix-loop-helix transcription factors has recently been implicated as regulators of growth and phenotypic modulation in VSMC and in the vascular response to injury. We summarize what is known about the functional role of Id proteins in controlling cellular growth and differentiation and vascular lesion formation.
Key Words: helix-loop-helix motifs ? muscle, smooth, vascular ? proliferation ? differentiation
Introduction
Understanding VSMC biology is important for understanding the vasculoproliferative disorders (such as in-stent restenosis, vein graft failure, and transplant arteriopathy) and atherosclerosis. In the vasculoproliferative disorders, vessel wall injury results in the release of cytokines and mitogens, such as IL-1, thrombin, PDGF, FGF, Ang II, and transforming growth factor-? from platelets, inflammatory cells, and cells within the vessel wall.1–5 These potent factors can induce normally quiescent VSMC in the vessel wall to modulate to a less differentiated phenotype, re-enter the cell cycle, proliferate, migrate, and secrete extracellular matrix, contributing to neointimal formation.6
In atherosclerosis, lipid deposition with subsequent macrophage infiltration initiates a similar, although less accelerated, cascade of events. Accumulation of phenotypically modulated VSMC within fatty streaks over time leads to progression to fibrous plaques that may become occlusive to the vascular lumen.7,8 However, matrix secretion by VSMC late in atherosclerotic plaque development appears to increase plaque stability and thus protect against rupture and thrombosis—the cause of most acute coronary syndromes—so that VSMC may have both deleterious and protective roles in atherosclerosis.7,9,10 Therefore, a further understanding of the mechanisms regulating the phenotypic modulation and growth of VSMC may provide important insights that could lead to the development of strategies to limit the VSMC accumulation leading to neointimal formation and enhance VSMC proliferation and matrix production to stabilize advanced atherosclerotic plaques.
Regulated gene expression is essential for the maintenance of normal vessel structure and function and, not surprisingly, the expression of multiple genes is altered in the vasculoproliferative disorders and atherosclerosis. Recent comprehensive reviews broadly summarize regulation of gene transcription in the vessel wall and in VSMC and suggest that transcriptional modulation of genes involved in cholesterol and fatty acid metabolism, inflammation, and cell cycle progression may hold promise as favorable therapeutic approaches to limit atherosclerosis and the vascular response to injury.11,12 Transcription factors implicated in regulating these processes (such as the sterol responsive element-binding protein , nuclear factor kappa B, E2F, and others) and their target genes (low-density lipoprotein receptor, adhesion molecules, cytokines, and cell cycle proteins) are known.11 However, the transcription factors and mechanisms that link phenotypic modulation and growth regulation in VSMC are poorly understood. Several classes of transcription factors are known or likely to be involved in the regulation of VSMC differentiation and, in some instances, proliferation.13 Notably, the HLH class of transcription factors is able to modulate both the expression of VSMC-specific and cell cycle regulatory genes. Subsequent studies provide evidence implicating the Id (Inhibitor of DNA binding) class of HLH factors as regulators of growth and differentiation in VSMC and during vascular lesion formation.14,15 Thus, the focus of this review is on summarizing what is known regarding the role of the HLH proteins, particularly the Id factors, in regulating these processes in VSMC and during lesion formation. First, however, we briefly overview transcription factor classes and HLH factor involvement in the vasculature.
HLH Transcription Factors
Transcription factors can be broadly categorized into 4 superclasses—those containing basic domains (superclass 1), those containing zinc-coordinated DNA binding domains (superclass 2), those containing helix-turn-helix domains (superclass 3), and ?-scaffold factors (superclass 4). In the vasculature, transcription factors from all 4 superclasses are expressed and contribute to vessel homeostasis. Transcription factors in superclass 1 can be further divided based on what specific motif(s) are present. One example is a basic HLH motif. Transcription factors containing the basic HLH (bHLH) motif all share a highly conserved HLH region, which mediates protein–protein interactions, as well as a basic DNA binding domain. bHLH factors activate transcription by forming homodimers or heterodimers that bind CANNTG consensus sequences, termed E-boxes, in the promoter region of responsive genes.
There are >240 HLH proteins identified; thus, a classification scheme based on tissue distribution, DNA-binding specificities, and dimerization capabilities has been devised.16 Class I HLH factors (known as E proteins) are bHLH factors that are expressed in many tissues including VSMC.17,18 E proteins such as E12, E47, HEB, and E2–2 can form homodimers or heterodimers with class II bHLH factors. Heterodimerization with class II bHLH proteins leads to activation of cell type-specific genes and cellular differentiation. Class II HLH proteins are tissue-restricted factors including MyoD and NeuroD.19,20 Factors belonging to this class (such as eHAND, dHAND, and capsulin/epicardin)21–23 have been implicated in the regulation of VSMC differentiation, although their specific target genes in VSMC are unknown. Class III HLH factors have a leucine zipper adjacent to the HLH motif (bHLH-LZ) and include c-Myc, E2F, and SREBP. Antisense-mediated c-Myc inhibition is capable of inhibiting VSMC growth and neointimal formation in response to injury in a rabbit and porcine model.24,25 E2F inhibition using "decoy" double-stranded oligonucleotides that contain consensus E2F binding sites reduced VSMC proliferation and lesion formation in response to balloon injury in porcine and rat arteries, as well as in response to vein grafting in rabbits and humans.26–28 SREBP mediates cholesterol-induced effects on gene transcription in VSMC.29 Class IV HLH proteins including Mad, Max, and Mxi dimerize with Myc and regulate Myc function.30,31 The Id class of HLH proteins (class V) lacks the basic DNA-binding domain and are dominant-negative regulators of class I and class II bHLH proteins.32 The role of Id in the vasculature is discussed in detail in later sections. Class VI HLH factors contain a proline in their basic region and include the Drosophila proteins Hairy and Enhancer of split. Cardiovascular HLH factor 1 (CHF1) is an HLH protein closely related to Hairy, although there is a substitution of glycine for proline in the basic region. CHF1 is expressed in differentiated VSMC and in the developing aorta, although specific VSMC targets of CHF1 are unknown.33 Lastly, the class VII HLH proteins contain a bHLH-Per-Arnt-Sim (bHLH-PAS) domain. bHLH-PAS factors implicated in VSMC and in vascular disease include hypoxia-inducible factor 1, which regulates expression of plasminogen activator inhibitor-1 and vascular endothelial growth factors in VSMC,34 and the clock proteins that regulate vascular circadian gene expression.35
Id Proteins
Id proteins consist of 4 members (Id1–4) that belong to the class V HLH family of transcription factors. Unlike bHLH factors, the Id (Inhibitor of DNA binding) proteins lack the basic DNA binding region altogether. Id proteins form inactive heterodimers with ubiquitously expressed class I bHLH factors and thus act as dominant-negative inhibitors of bHLH function (Figure 1). Whereas class I HLH factors are the primary target of Id proteins, Id also regulates class II HLH factor function because (with few exceptions) class II factors are incapable of forming homodimers and preferentially heterodimerize with class I E proteins36. Class I and class II HLH factors regulate the transcription of cell cycle genes,37–42 and class II factors also regulate the expression of cell type-specific genes and the differentiated phenotype.43–45 Thus, the Id proteins are likely candidates to mediate the cross-talk between pathways that regulate growth and pathways that regulate the differentiated phenotype in VSMC.
Figure 1. Principal mechanism of Id action. A, Transactivation of an E-box containing promoter by a bHLH dimer. Heterodimers of bHLH transcription factors interact via HLH dimerization motifs. These dimers bind to consensus sites present in the promoter regions of responsive genes by virtue of their basic DNA binding domains. Binding to consensus sites, termed E-boxes, functions to recruit transcriptional coactivators, activating transcription. B, Inhibition of bHLH transactivation by Id proteins. Id proteins form heterodimers with bHLH factors. Because Id proteins lack basic DNA-binding motifs, the resulting Id-bHLH dimer is unable to bind DNA and cannot activate transcription. Thus, the Id proteins function principally as dominant-negative transcriptional regulators.
In addition to the common HLH domain that mediates Id dimerization, each Id protein has unique features that may regulate specific functional roles. Id2, Id3, and Id4, but not Id1, contain a consensus cdk2 phosphorylation site in their N-terminus and are phosphorylated by cyclin-cdk2 complexes, an event that alters the specificity of Id2 and Id3 in blocking bHLH dimers from binding E-box sequences in vitro.46,47 Phosphorylation of Id2 is required for transcriptional inhibition of p21Cip1 and cell cycle entry in VSMC.47 Furthermore, the C-terminal regions of the Id proteins differ dramatically (Figure 2). This is especially important because alterations in the C-termini of Id proteins have been shown to regulate protein stability and dominant-negative function.48,49 Two Id members, Id1 and Id3, have alternatively spliced isoforms. In rats these alternative isoforms, termed Id1.25 and Id3a, are found in cardiac and VSMCs. Interestingly, Id1.25 and Id3a appear to be generated by intron retention, resulting in alternative message products encoding unique C-termini.17,49 Id proteins can also dimerize with the class III bHLH-LZ protein SREBP50 and transcription factors that do not contain an HLH domain such as the ETS-domain factors,51 MIDA1,52 PAX-domain factors,53 and pRb.54,55 The specific role of domains within the Id proteins and their role in mediating Id partner specificity are poorly understood.
Figure 2. The Id family of proteins. Shown are the peptide sequences of the Id family members. The HLH dimerization motif, highly conserved among family members, is boxed in green. The N-terminal cdk-2 phosphorylation site present in Id2, Id3, Id3a, and Id4 is boxed in red. Unique C-terminal sequences generated by intron retention in Id1 and Id3 are boxed in blue.
Ids and the Cell Cycle
Id expression is upregulated after mitogen stimulation in a variety of cell types, and ectopic Id expression can promote cellular proliferation.38,55,56 However, whereas the Ids can all promote growth, and the general dominant-negative paradigm of Id function is common among family members, accumulating evidence indicates that the specific roles of these proteins in regulating growth are not redundant.55,56 Antisense inhibition of any 1 of the 4 Ids is sufficient to abrogate serum-stimulated proliferation in fibroblasts.56
Regulation of cell cycle progression represents a major means whereby the Id proteins affect cellular growth, and the specific mechanisms whereby this is accomplished are beginning to be elucidated. One major mechanism involves the regulation of cyclin-dependent kinase (cdk) inhibitors, including p16INK4, p21Cip1, and p27Waf1. The cdk inhibitors modulate the formation and/or function of cyclin–cdk complexes that regulate progression of the cell cycle.57 Expression of p21Cip1 and p27Waf1 is elevated in terminally differentiated cells, and ectopic expression of p16INK4, p21Cip1, and p27Waf1 results in cell-cycle arrest and a decrease of cellular growth in a variety of cell types, including VSMC.42,58,59 The promoter regions of p16INK4 and p21Cip1 contain multiple E-boxes, and several bHLH factors, including E47, are capable of stimulating p16INK4 and p21Cip1 transcription.37–39 Consistent with this paradigm, Id1, Id2, and Id3 can inhibit p21Cip1 and p16INK4 transcription in fibroblasts and VSMC.15,37,55 Therefore, by acting as dominant-negative transcriptional regulators of cyclin-dependent kinase inhibitors, the Ids can promote entry into the cell cycle and stimulate cellular growth.
A second mechanism whereby Id proteins promote cellular growth appears to be specific to Id2 and involves inactivation of the retinoblastoma protein (pRb). E2F, a transcription factor that activates a variety of genes required for cell cycle progression, is normally inactive by virtue of its association with pRb. Phosphorylation of pRb by cyclin/cdk complexes causes dissociation of the pRb/E2F complex, releasing E2F and allowing for cell cycle progression.57 Id2 (but not Id1 or Id3) is also able to promote complex dissociation, leading to enhanced cell cycle progression, via an interaction between the HLH region of Id2 and the pocket domain of pRb.54,55
Ids Mediate Mitogen-Induced VSMC Growth
Accumulating evidence suggests that the Id proteins are mediators of several mitogenic factors involved in VSMC growth. Such factors act generally through receptor tyrosine kinases to stimulate classical mitogenic pathways, eg, the mitogen-activated protein kinase (MAPK) pathway.60 Receptor tyrosine kinase stimulation by PDGF or serum increases both Id expression and VSMC growth.56,61 Further, activation of protein kinase C or Ras is capable of upregulating Id3 expression, whereas this effect is blocked by either Ras or MAPK inhibition.62
Receptor tyrosine kinase-mediated MAPK activation results in increased transcription of early growth response gene product 1 (Egr-1). Egr-1 is upregulated in vivo in restenotic and atherosclerotic lesions, and Egr-1 inhibition reduces formation of both types of lesions in vivo.63–67 Interestingly, Egr-1 enhances expression of Id3 message, providing a link between mitogen or injury-induced Egr-1 and Id expression.68 Another immediate–early response gene, c-Myc, activates Id2 transcription. c-Myc is also upregulated after vascular injury, with c-Myc inhibition attenuating VSMC proliferation in vitro and restenosis in rat and porcine models of angioplasty.24 c-Myc has recently been shown to bind the Id2 promoter and upregulate Id2 message levels. Of importance, Id2 is required for the mitogenic effects of c-Myc, because cells from Id2–/– mice, but not wild-type controls, are unresponsive to c-Myc simulation.69
Angiotensin II (Ang II) is another VSMC mitogen. Ang II acts through AT1 angiotensin receptors to induce reactive oxygen species (ROS) production and growth in the VSMC.70 ROS act as signaling molecules, mediating the mitogenic effects of Ang II via activation of mitogenic pathways, including the MAPK cascade. Ang II is also capable of stimulating receptor tyrosine phosphorylation and activation of the MAPK pathway.61 Ang II is released after vascular injury, promotes VSMC growth and proliferation, and the mitogenic properties of Ang II have been shown to contribute to atherogenesis.71–73 Mueller et al have recently identified Id3 as a message that is upregulated, in a MAPK-dependent manner, in cultured VSMC treated with Ang II.74,75 VSMCs treated with Ang II or ROS also displayed increased cell number and cell-cycle entry, and these effects were abrogated by Id3 antisense inhibition. Further, Ang II/ROS treatment decreased expression of p21Cip1 4 hours after treatment, coincident with Id3 induction.74 Thus, regulation of Id3 expression appears to be an important, indeed necessary, mechanism by which Ang II stimulates VSMC growth.
The Ids and VSMC Differentiation
In addition to their growth-promoting properties, the Id proteins can also act as negative regulators of cellular differentiation. Ectopic expression of Id proteins inhibits cellular differentiation in several cell line models, including myoblasts, epithelial cells, pre-adipocytes, and osteosarcoma cells, and expression of Id genes is significantly reduced on terminal differentiation of a variety of cell types, including myoblasts.55,76–80 Id proteins likely regulate differentiation via functional antagonism of bHLH factors well-characterized as promoters of cellular differentiation, such as MyoD and NeuroD.81
Modulation of VSMC phenotype, notably alteration of the VSMC differentiated state, is a hallmark of vascular lesion formation in both the vasculoproliferative disorders and the development of atherosclerosis.82 The primary function of differentiated VSMC is to contract; thus, expression of SM-specific contractile proteins, such as SM -actin, is commonly used as an indicator of VSMC differentiation. Strong evidence for HLH involvement in the regulation of VSMC differentiation includes data published by Kumar et al, demonstrating that consensus bHLH DNA binding sites (E-boxes) are essential for SM -actin promoter activation in vivo.14 Although several bHLH factors, including E12, E47, dHAND, and HES-2, are in fact expressed in VSMC, it is unclear whether these are involved in regulating VSMC differentiation in vivo.21,83–85 In vitro, ectopic expression of bHLH factors can drive SM -actin expression in VSMC; importantly, coexpression of Id2 or Id3 abrogates this effect.14 It is therefore intriguing to think that the de-differentiation of VSMC after injury is mediated by the Id proteins. In vivo expression of VSMC differentiation markers, including SM -actin, decreases after vascular injury at time points coincident with upregulation of Id2 and Id3.82 Therefore, the Id proteins are likely important mediators of the differentiated state of VSMC during lesion formation, although this has not yet been directly addressed.
Id Expression During Vascular Lesion Formation
Given that the Ids regulate VSMC growth and differentiation, it is not surprising that Id proteins have been implicated as modulators of vascular lesion development. Most of the in vivo data to date involve Id3. Id3 message expression in the vessel wall is significantly increased after balloon endothelial denudation in a rat carotid injury model. Id3, expressed at low levels in normal vessels, is increased within 3 days of injury and remains high through 14 days postinjury, corresponding to the time of peak VSMC proliferation and lesion development.17,86 In addition, Nickening et al have recently shown that Id3 protein expression is also induced in vivo after wire injury of mouse carotid arteries, further implicating Id3 involvement in the vascular proliferative response to mechanical injury.75
In contrast to Id3, intron-containing Id3a message is absent from normal vessels and quiescent VSMC is strongly induced after balloon injury in rats and remains high through 28 days after injury. Interestingly, the human homologue of Id3a, Id3L, is expressed in advanced human atherosclerotic plaques, particularly in regions rich in VSMC (Figure 3).17 Moreover, gene delivery of Id3a, found to induce apoptosis and inhibit Id3 expression in VSMC, reduced the neointima-to-media ratio in response to balloon endothelial denudation in rats by 55%.15
Figure 3. Id3L mRNA is expressed in human carotid atherosclerotic plaques. In situ hybridization of a representative human carotid endarterectomy specimen with use of digoxigenin-labeled antisense Id3L riboprobe reveals Id3L mRNA expression in discreet areas within the specimens (A). No staining is seen in a contigu-ous section of this specimen hybridized with the corresponding sense probe (B). Immunohistochemical staining of a contiguous section with a monoclonal antibody against smooth muscle -actin (C, D ) reveals positive diaminobenzidine (brown) staining in areas of Id3L mRNA staining (hematoxylin counterstain).
Id2 expression is also modulated in vivo in a rat carotid injury model. Normally absent from the vessel wall, Id2 protein expression is induced by 6 days after balloon injury and remains high through 14 days. Like Id3, Id2 expression corresponds to peak cellular growth in the developing lesion. Id2 expression is declining by 28 days postinjury and is not seen in fully developed lesions.87 Expression of Id1 and Id4 in the vasculature has not yet been examined.
Id Involvement in Angiogenesis
Interesting in vivo data regarding Id function in the vasculature have recently been published by Lyden et al. This group generated Id3–/– Id1–/– double-knockout mice for developmental studies, but the mice are nonviable. They die in utero at E12.5 because of vascular abnormalities, which lead to intracranial hemorrhage. Results in earlier embryos demonstrated that the Id1–Id3 double-knockout mice have premature withdrawal of neuroblasts from the cell cycle and expression of neural-specific differentiation markers. However, Id1+/– Id3–/– mice were viable. An unexpected but exciting finding was that these mice had a marked attenuation of tumor vascularization and angiogenesis, providing the first in vivo evidence that the presence of Id3 is critical to the vasculature.88 These results are particularly relevant because angiogenesis is a process involving extensive VSMC migration, matrix secretion, and proliferation—themes held in common with the vascular response to injury—and is a critical process in atherosclerotic lesion progression.89–92
Summary
There is clear evidence that the Id proteins regulate VSMC growth and differentiation, key components of the vasculoproliferative disorders. Ids act to inhibit expression of genes that inhibit cell cycle progression, as well as genes specific for differentiated VSMC. Thus, Id proteins provide an important link between these 2 processes in the vasculature. Id expression is upregulated in developing restenotic lesions and is an important player in the signaling cascades activated by mitogens released after vascular injury.
The work reviewed provides evidence that Id proteins are key regulators of VSMC biology; however, important questions regarding the role of Ids in vascular disease remain unanswered. How are expression and function of the Id proteins coordinately regulated in VSMC in response to injury? What are the other important cell cycle factors regulated by Id proteins? Do the Id proteins regulate other processes in VSMC such as migration or matrix production? What bHLH factors do Id proteins regulate in VSMC and in the vessel wall? Do Id deletions or mutations alter susceptibility to vascular disease? Clearly, much further research in this area is needed, because a more complete understanding of how Id proteins regulate VSMC growth and differentiation and vascular lesion formation is essential to elucidating the molecular mechanisms of lesion development.
Acknowledgments
This review was supported by National Institutes of Health grants T32HL007284 (S.T.F.), RO1 HL062522, and PO1 HL55798 (C.A.M.). We thank Drs Gary Owens and Amy Tucker for helpful comments on the manuscript.
References
Hart CE, Kraiss LW, Vergel S, Gilbertson D, Kenagy R, Kirkman T, Crandall DL, Tickle S, Finney H, Yarranton G, Clowes AW. PDGF? receptor blockade inhibits intimal hyperplasia in the baboon. Circulation. 1999; 99: 564–569.
Wang X, Romanic AM, Yue TL, Feuerstein GZ, Ohlstein EH. Expression of interleukin-1?, interleukin-1 receptor, and interleukin-1 receptor antagonist mRNA in rat carotid artery after balloon angioplasty. Biochem Biophys Res Com. 2000; 271: 138–143.
Hatton MW, Moar SL, Richardson M. Deendothelialization in vivo initiates a thrombogenic reaction at the rabbit aorta surface. Correlation of uptake of fibrinogen and antithrombin III with thrombin generation by the exposed subendothelium. Am J Pathol. 1989; 135: 499–508.
Ferns GA, Raines EW, Sprugel KH, Motani AS, Reidy MA, Ross R. Inhibition of neointimal smooth muscle accumulation after angioplasty by an antibody to PDGF. Science. 1991; 253: 1129–1132.
Lindner V, Reidy MA. Proliferation of smooth muscle cells after vascular injury is inhibited by an antibody against basic fibroblast growth factor. Proc Natl Acad Sci U S A. 1991; 1988: 3739–3743.
Dzau VJ, Braun-Dullaeus RC, Sedding DG. Vascular proliferation and atherosclerosis: new perspectives and therapeutic strategies. Nat Med. 2002; 8: 1249–1256.
Lafont A, Libby P. The smooth muscle cell: sinner or saint in restenosis and the acute coronary syndromes? J Am Coll Cardiol. 1998; 32: 283–285.
Mosse PR, Campbell GR, Wang ZL, Campbell JH. Smooth muscle phenotypic expression in human carotid arteries. I. Comparison of cells from diffuse intimal thickenings adjacent to atheromatous plaques with those of the media. Lab Invest. 1985; 53: 556–562.
Braganza DM, Bennett MR. New insights into atherosclerotic plaque rupture. Postgrad Med J. 2001; 77: 94–98.
Lusis AJ. Atherosclerosis. Nature. 2000; 407: 233–241.
de Nigris F, Lerman LO, Napoli C. New insights in the transcriptional activity and coregulator molecules in the arterial wall. Int J Cardiol. 2002; 86: 153–168.
Walsh K, Takahashi A. Transcriptional regulation of vascular smooth muscle cell phenotype. Z Kardiol. 2001; 90 (suppl 3): 12–16.
Kumar MS, Owens GK. Combinatorial control of smooth muscle-specific gene expression. Arterioscler Thromb Vasc Biol. 2003; 23: 737–747.
Kumar MS, Hendrix JA, Johnson AD, Owens GK. Smooth muscle -actin gene requires two E-boxes for proper expression in vivo and is a target of class I basic helix-loop-helix proteins. Circ Res. 2003; 92: 840–847.
Forrest ST, Barringhaus KG, Perlegras D, Hammarskjold ML, McNamara CA. Intron retention generates a novel Id3 isoform that inhibits vascular lesion formation. J Biol Chem. 2004; 279: 32897–32903.
Murre C, Bain G, van Dijk MA, Engel I, Furnari BA, Massari ME, Matthews JR, Quong MW, Rivera RR, Stuiver MH. Structure and function of helix-loop-helix proteins. Biochim Biophys Acta. 1994; 1218: 129–135.
Matsumura ME, Li F, Berthoux L, Wei B, Lobe DR, Jeon C, Hammarskjold ML, McNamara CA. Vascular injury induces posttranscriptional regulation of the Id3 gene: cloning of a novel Id3 isoform expressed during vascular lesion formation in rat and human atherosclerosis. Arterioscler Thromb Vasc Biol. 2001; 21: 752–758.
Massari ME, Murre C. Helix-loop-helix proteins: regulators of transcription in eucaryotic organisms. Mol Cell Biol. 2000; 20: 429–440.
Lau LF, Nathans D. Identification of a set of genes expressed during the G0/G1 transition of cultured mouse cells. EMBO J. 1985; 4: 3145–3151.
Shi Y, O’Brien JE Jr, Ala-Kokko L, Chung W, Mannion JD, Zalewski A. Origin of extracellular matrix synthesis during coronary repair. Circulation. 1997; 95: 997–1006.
Yamagishi H, Olson EN, Srivastava D. The basic helix-loop-helix transcription factor, dHAND, is required for vascular development. J Clin Invest. 2000; 105: 261–270.
Hollenberg SM, Sternglanz R, Cheng PF, Weintraub H. Identification of a new family of tissue-specific basic helix-loop-helix proteins with a two-hybrid system. Mol Cell Biol. 1995; 15: 3813–3822.
Hidai H, Bardales R, Goodwin R, Quertermous T, Quertermous EE. Cloning of capsulin, a basic helix-loop-helix factor expressed in progenitor cells of the pericardium and the coronary arteries. Mech Dev. 1998; 73: 33–43.
Kipshidze N, Iversen P, Keane E, Stein D, Chawla P, Skrinska V, Shankar LR, Mehran R, Chekanov V, Dangas G, Komorowski R, Haudenschild C, Khanna A, Leon M, Keelan MH, Moses J. Complete vascular healing and sustained suppression of neointimal thickening after local delivery of advanced c-myc antisense at six months follow-up in a rabbit balloon injury model. Cardiovasc Radiat Med. 2002; 3: 26–30.
Kipshidze N, Keane E, Stein D, Chawla P, Skrinska V, Shankar LR, Khanna A, Komorowski R, Haudenschild C, Iversen P, Leon MB, Keelan MH, Moses J. Local delivery of c-myc neutrally charged antisense oligonucleotides with transport catheter inhibits myointimal hyperplasia and positively affects vascular remodeling in the rabbit balloon injury model. Catheter Cardiovasc Interv. 2001; 1954: 247–256.
Nakamura T, Morishita R, Asai T, Tsuboniwa N, Aoki M, Sakonjo H, Yamasaki K, Hashiya N, Kaneda Y, Ogihara T. Molecular strategy using cis-element ‘decoy’ of E2F binding site inhibits neointimal formation in porcine balloon-injured coronary artery model. Gene Ther. 2002; 1909: 488–494.
Aoki M, Morishita R, Matsushita H, Hayashi S, Nakagami H, Yamamoto K, Moriguchi A, Kaneda Y, Higaki J, Ogihara T. Inhibition of the p53 tumor suppressor gene results in growth of human aortic vascular smooth muscle cells. Potential role of p53 in regulation of vascular smooth muscle cell growth. Hypertension. 1999; 34: 192–200.
Morishita R, Gibbons GH, Horiuchi M, Ellison KE, Nakama M, Zhang L, Kaneda Y, Ogihara T, Dzau VJ. A gene therapy strategy using a transcription factor decoy of the E2F binding site inhibits smooth muscle proliferation in vivo. Proc Natl Acad Sci U S A. 1995; 92: 5855–5859.
Llorente-Cortes V, Otero-Vinas M, Sanchez S, Rodriguez C, Badimon L. Low-density lipoprotein upregulates low-density lipoprotein receptor-related protein expression in vascular smooth muscle cells: possible involvement of sterol regulatory element binding protein-2-dependent mechanism. Circulation. 2002; 106: 3104–3110.
Ayer DE, Lawrence QA, Eisenman RN. Mad-Max transcriptional repression is mediated by ternary complex formation with mammalian homologs of yeast repressor Sin3. Cell. 1995; 80: 767–776.
Ayer DE, Kretzner L, Eisenman RN. Mad: a heterodimeric partner for Max that antagonizes Myc transcriptional activity. Cell. 1993; 72: 211–222.
Benezra R, Davis RL, Lockshon D, Turner DL, Weintraub H. The protein Id: a negative regulator of helix-loop-helix DNA binding proteins. Cell. 1990; 61: 49–59.
Chin MT, Maemura K, Fukumoto S, Jain MK, Layne MD, Watanabe M, Hsieh CM, Lee ME. Cardiovascular basic helix loop helix factor 1, a novel transcriptional repressor expressed preferentially in the developing and adult cardiovascular system. J Biol Chem. 2000; 275: 6381–6387.
Gorlach A, Diebold I, Schini-Kerth VB, Berchner-Pfannschmidt U, Roth U, Brandes RP, Kietzmann T, Busse R. Thrombin activates the hypoxia-inducible factor-1 signaling pathway in vascular smooth muscle cells: Role of the p22(phox)-containing NADPH oxidase. Circ Res. 2001; 89: 47–54.
Curtis AM, Seo SB, Westgate EJ, Rudic RD, Smyth EM, Chakravarti D, FitzGerald GA, McNamara P. Histone acetyltransferase-dependent chromatin remodeling and the vascular clock. J Biol Chem. 2004; 279: 7091–7097.
Murre C, McCaw PS, Vaessin H, Caudy M, Jan LY, Jan YN, Cabrera CV, Buskin JN, Hauschka SD, Lassar AB. Interactions between heterologous helix-loop-helix proteins generate complexes that bind specifically to a common DNA sequence. Cell. 1989; 58: 537–544.
Prabhu S, Ignatova A, Park ST, Sun XH. Regulation of the expression of cyclin-dependent kinase inhibitor p21 by E2A and Id proteins. Mol Cell Biol. 1997; 17: 5888–5896.
Peverali FA, Ramqvist T, Saffrich R, Pepperkok R, Barone MV, Philipson L. Regulation of G1 progression by E2A and Id helix-loop-helix proteins. EMBO J. 1994; 13: 4291–4301.
Pagliuca A, Gallo P, De Luca P, Lania L. Class A helix-loop-helix proteins are positive regulators of several cyclin-dependent kinase inhibitors’ promoter activity and negatively affect cell growth. Cancer Res. 2000; 60: 1376–1382.
Zhao F, Vilardi A, Neely RJ, Choi JK. Promotion of cell cycle progression by basic helix-loop-helix E2A. Mol Cell Biol. 2001; 21: 6346–6357.
Guo K, Wang J, Andres V, Smith RC, Walsh K. MyoD-induced expression of p21 inhibits cyclin-dependent kinase activity upon myocyte terminal differentiation. Mol Cell Biol. 1995; 15: 3823–3829.
Halevy O, Novitch BG, Spicer DB, Skapek SX, Rhee J, Hannon GJ, Beach D, Lassar AB. Correlation of terminal cell cycle arrest of skeletal muscle with induction of p21 by MyoD. Science. 1995; 267: 1018–1021.
Choi J, Costa ML, Mermelstein CS, Chagas C, Holtzer S, Holtzer H. MyoD converts primary dermal fibroblasts, chondroblasts, smooth muscle, and retinal pigmented epithelial cells into striated mononucleated myoblasts and multinucleated myotubes. Proc Natl Acad Sci U S A. 1990; 87: 7988–7992.
Lassar AB, Buskin JN, Lockshon D, Davis RL, Apone S, Hauschka SD, Weintraub H. MyoD is a sequence-specific DNA binding protein requiring a region of myc homology to bind to the muscle creatine kinase enhancer. Cell. 1989; 58: 823–831.
French BA, Chow KL, Olson EN, Schwartz RJ. Heterodimers of myogenic helix-loop-helix regulatory factors and E12 bind a complex element governing myogenic induction of the avian cardiac -actin promoter. Mol Cell Biol. 1991; 11: 2439–2450.
Hara E, Hall M, Peters G. Cdk2-dependent phosphorylation of Id2 modulates activity of E2A-related transcription factors. EMBO J. 1997; 16: 332–342.
Deed RW, Hara E, Atherton GT, Peters G, Norton JD. Regulation of Id3 cell cycle function by Cdk-2-dependent phosphorylation. Mol Cell Biol. 1997; 17: 6815–6821.
Chen B, Han BH, Sun XH, Lim RW. Inhibition of muscle-specific gene expression by Id3: requirement of the C-terminal region of the protein for stable expression and function. Nucleic Acids Res. 1997; 25: 423–430.
Springhorn JP, Singh K, Kelly RA, Smith TW. Posttranscriptional regulation of Id1 activity in cardiac muscle. Alternative splicing of novel Id1 transcript permits homodimerization. J Biol Chem. 1994; 269: 5132–5136.
Moldes M, Boizard M, Liepvre XL, Feve B, Dugail I, Pairault J. Functional antagonism between inhibitor of DNA binding (Id) and adipocyte determination and differentiation factor 1/sterol regulatory element-binding protein-1c (ADD1/SREBP-1c) trans-factors for the regulation of fatty acid synthase promoter in adipocytes. Biochem J. 1999; 344: t-80.
Yates PR, Atherton GT, Deed RW, Norton JD, Sharrocks AD. Id helix-loop-helix proteins inhibit nucleoprotein complex formation by the TCF ETS-domain transcription factors. EMBO J. 1999; 18: 968–976.
Shoji W, Inoue T, Yamamoto T, Obinata M. MIDA1, a protein associated with Id, regulates cell growth. J Biol Chem. 1995; 270: 24818–24825.
Roberts EC, Deed RW, Inoue T, Norton JD, Sharrocks AD. Id Helix-Loop-Helix Proteins Antagonize Pax Transcription Factor Activity by Inhibiting DNA Binding. Mol Cell Biol. 2001; 21: 524–533.
Lasorella A, Iavarone A, Israel MA. Id2 specifically alters regulation of the cell cycle by tumor suppressor proteins. Mol Cell Biol. 1996; 16: 2570–2578.
Iavarone A, Garg P, Lasorella A, Hsu J, Israel MA. The helix-loop-helix protein Id-2 enhances cell proliferation and binds to the retinoblastoma protein. Genes Dev. 1994; 8: 1270–1284.
Barone MV, Pepperkok R, Peverali FA, Philipson L. Id proteins control growth induction in mammalian cells. Proc Natl Acad Sci U S A. 1994; 91: 4985–4988.
Sherr CJ, Roberts JM. CDK inhibitors: positive and negative regulators of G1-phase progression. Genes Dev. 1999; 13: 1501–1512.
Tanner FC, Boehm M, Akyurek LM, San H, Yang ZY, Tashiro J, Nabel GJ, Nabel EG. Differential effects of the cyclin-dependent kinase inhibitors p27(Kip1), p21(Cip1), and p16(Ink4) on vascular smooth muscle cell proliferation. Circulation. 2000; 101: 2022–2025.
Yang ZY, Simari RD, Perkins ND, San H, Gordon D, Nabel GJ, Nabel EG. Role of the p21 cyclin-dependent kinase inhibitor in limiting intimal cell proliferation in response to arterial injury. Proc Natl Acad Sci U S A. 1996; 93: 7905–7910.
Heldin CH, Westermark B. Mechanism of action and in vivo role of platelet-derived growth factor. Physiol Rev. 1999; 79: 1283–1316.
Linseman DA, Benjamin CW, Jones DA. Convergence of angiotensin II and platelet-derived growth factor receptor signaling cascades in vascular smooth muscle cells. J Biol Chem. 1995; 270: 12563–12568.
Bain G, Cravatt CB, Loomans C, Alberola-Ila J, Hedrick SM, Murre C. Regulation of the helix-loop-helix proteins, E2A and Id3, by the Ras- ERK MAPK cascade. Nat Immunol. 2001; 2: 165–171.
Khachigian LM, Lindner V, Williams AJ, Collins T. Egr-1-induced endothelial gene expression: a common theme in vascular injury. Science. 1996; 271: 1427–1431.
McCaffrey TA, Fu C, Du B, Eksinar S, Kent KC, Bush H Jr, Kreiger K, Rosengart T, Cybulsky MI, Silverman ES, Collins T. High-level expression of Egr-1 and Egr-1-inducible genes in mouse and human atherosclerosis. J Clin Invest. 2000; 105: 653–662.
Lowe HC, Fahmy RG, Kavurma MM, Baker A, Chesterman CN, Khachigian LM. Catalytic oligodeoxynucleotides define a key regulatory role for early growth response factor-1 in the porcine model of coronary in-stent restenosis. Circ Res. 2001; 89: 670–677.
Harja E, Bucciarelli LG, Lu Y, Stern DM, Zou YS, Schmidt AM, Yan SF. Early growth response-1 promotes atherogenesis: mice deficient in early growth response-1 and apolipoprotein E display decreased atherosclerosis and vascular inflammation. Circ Res. 2004; 94: 333–339.
Santiago FS, Lowe HC, Kavurma MM, Chesterman CN, Baker A, Atkins DG, Khachigian LM. New DNA enzyme targeting Egr-1 mRNA inhibits vascular smooth muscle proliferation and regrowth after injury. Nat Med. 1999; 5: 1264–1269.
Bettini M, Xi H, Milbrandt J, Kersh GJ. Thymocyte Development in Early Growth Response Gene 1-Deficient Mice. J Immunol. 2002; 169: 1713–1720.
Lasorella A, Noseda M, Beyna M, Yokota Y, Iavarone A. Id2 is a retinoblastoma protein target and mediates signalling by Myc oncoproteins. Nature. 2000Oct 5; 407: 592–598.
Griendling KK, Ushio-Fukai M. Reactive oxygen species as mediators of angiotensin II signaling. Regul Pept. 2000; 91: 21–27.
Badimon JJ, Fuster V, Chesebro JH, Badimon L. Coronary atherosclerosis. A multifactorial disease. Circulation. 1993; 87 (3 Suppl): II3–II16.
The HOPE (Heart Outcomes Prevention Evaluation) Study: the design of a large, simple randomized trial of an angiotensin-converting enzyme inhibitor (ramipril) and vitamin E in patients at high risk of cardiovascular events. The HOPE study investigators. Can J Cardiol. 1996; 12: 127–137.
Eto H, Biro S, Miyata M, Kaieda H, Obata H, Kihara T, Orihara K, Tei C. Angiotensin II type 1 receptor participates in extracellular matrix production in the late stage of remodeling after vascular injury. Cardiovasc Res. 2003; 59: 200–211.
Mueller C, Baudler S, Welzel H, Bohm M, Nickenig G. Identification of a novel redox-sensitive gene, Id3, which mediates angiotensin II-induced cell growth. Circulation. 2002; 105: 2423–2428.
Nickenig G, Baudler S, Muller C, Werner C, Werner N, Welzel H, Strehlow K, Bohm M. Redox-sensitive vascular smooth muscle cell proliferation is mediated by GKLF and Id3 in vitro and in vivo. FASEB J. 2002; 16: 1077–1086.
Kreider BL, Benezra R, Rovera G, Kadesch T. Inhibition of myeloid differentiation by the helix-loop-helix protein Id. Science. 1992; 255: 1700–1702.
Jen Y, Weintraub H, Benezra R. Overexpression of Id protein inhibits the muscle differentiation program: in vivo association of Id with E2A proteins. Genes Dev. 1992; 6: 1466–1479.
Desprez PY, Hara E, Bissell MJ, Campisi J. Suppression of mammary epithelial cell differentiation by the helix-loop-helix protein Id-1. Mol Cell Biol. 1995; 15: 3398–3404.
Atherton GT, Travers H, Deed R, Norton JD. Regulation of cell differentiation in C2C12 myoblasts by the Id3 helix-loop-helix protein. Cell Growth Differ. 1996; 7: 1059–1066.
Moldes M, Lasnier F, Feve B, Pairault J, Djian P. Id3 prevents differentiation of preadipose cells. Mol Cell Biol. 1997; 17: 1796–1804.
Norton JD. ID helix-loop-helix proteins in cell growth, differentiation and tumorigenesis. J Cell Sci. 2000; 113: 3897–3905.
Owens GK. Regulation of differentiation of vascular smooth muscle cells. Physiol Rev. 1995; 75: 487–517.
Inaba T, Gotoda T, Ishibashi S, Harada K, Ohsuga JI, Ohashi K, Yazaki Y, Yamada N. Transcription factor PU. 1 mediates induction of c-fms in vascular smooth muscle cells: a mechanism for phenotypic change to phagocytic cells. Mol Cell Biol. 1996; 16: 2264–2273.
Roberts VJ, Steenbergen R, Murre C. Localization of E2A mRNA expression in developing and adult rat tissues. Proc Natl Acad Sci U S A. 1993; 90: 7583–7587.
Ishibashi M, Sasai Y, Nakanishi S, Kageyama R. Molecular characterization of HES-2, a mammalian helix-loop-helix factor structurally related to Drosophila hairy and Enhancer of split. Eur J Biochem. 1993; 215: 645–652.
Clowes AW, Reidy MA, Clowes MM. Kinetics of cellular proliferation after arterial injury. I. Smooth muscle growth in the absence of endothelium. Lab Invest. 1983; 49: 327–333.
Matsumura ME, Lobe DR, McNamara CA. Contribution of the helix-loop-helix factor Id2 to regulation of vascular smooth muscle cell proliferation. J Biol Chem. 2001.
Lyden D, Hattori K, Dias S, Costa C, Blaikie P, Butros L, Chadburn A, Heissig B, Marks W, Witte L, Wu Y, Hicklin D, Zhu Z, Hackett NR, Crystal RG, Moore MA, Hajjar KA, Manova K, Benezra R, Rafii S. Impaired recruitment of bone-marrow-derived endothelial and hematopoietic precursor cells blocks tumor angiogenesis and growth. Nat Med. 2001; 7: 1194–1201.
Moulton KS, Heller E, Konerding MA, Flynn E, Palinski W, Folkman J. Angiogenesis inhibitors endostatin or TNP-470 reduce intimal neovascularization and plaque growth in apolipoprotein E-deficient mice. Circulation. 1999; 99: 1726–1732.
Boyle JJ, Wilson B, Bicknell R, Harrower S, Weissberg PL, Fan TP. Expression of angiogenic factor thymidine phosphorylase and angiogenesis in human atherosclerosis. J Pathol. 2000; 192: 234–242.
Moulton KS, Vakili K, Zurakowski D, Soliman M, Butterfield C, Sylvin E, Lo KM, Gillies S, Javaherian K, Folkman J. Inhibition of plaque neovascularization reduces macrophage accumulation and progression of advanced atherosclerosis. Proc Natl Acad Sci U S A. 2003; 100: 4736–4741.
Moulton KS. Plaque angiogenesis: its functions and regulation. Cold Spring Harb Symp Quant Biol. 2002; 67: 471–482.(Scott Forrest; Coleen McN)
ABSTRACT
Vascular smooth muscle cell (VSMC) modulation to a de-differentiated phenotype and proliferation are key components of vascular lesion formation. Understanding how these processes are regulated is essential to understanding the progression of vascular diseases such as atherosclerosis and in-stent restenosis. The Id family of helix-loop-helix (HLH) transcription factors has emerged as important regulators of cellular growth and differentiation. Recent published findings have implicated the Id proteins as important regulators of growth and phenotypic modulation in VSMC and in the vascular response to injury. In this review, we summarize what is known regarding how the Id proteins function to control cellular growth and differentiation and their role in vascular lesion formation.
The Id family of helix-loop-helix transcription factors has recently been implicated as regulators of growth and phenotypic modulation in VSMC and in the vascular response to injury. We summarize what is known about the functional role of Id proteins in controlling cellular growth and differentiation and vascular lesion formation.
Key Words: helix-loop-helix motifs ? muscle, smooth, vascular ? proliferation ? differentiation
Introduction
Understanding VSMC biology is important for understanding the vasculoproliferative disorders (such as in-stent restenosis, vein graft failure, and transplant arteriopathy) and atherosclerosis. In the vasculoproliferative disorders, vessel wall injury results in the release of cytokines and mitogens, such as IL-1, thrombin, PDGF, FGF, Ang II, and transforming growth factor-? from platelets, inflammatory cells, and cells within the vessel wall.1–5 These potent factors can induce normally quiescent VSMC in the vessel wall to modulate to a less differentiated phenotype, re-enter the cell cycle, proliferate, migrate, and secrete extracellular matrix, contributing to neointimal formation.6
In atherosclerosis, lipid deposition with subsequent macrophage infiltration initiates a similar, although less accelerated, cascade of events. Accumulation of phenotypically modulated VSMC within fatty streaks over time leads to progression to fibrous plaques that may become occlusive to the vascular lumen.7,8 However, matrix secretion by VSMC late in atherosclerotic plaque development appears to increase plaque stability and thus protect against rupture and thrombosis—the cause of most acute coronary syndromes—so that VSMC may have both deleterious and protective roles in atherosclerosis.7,9,10 Therefore, a further understanding of the mechanisms regulating the phenotypic modulation and growth of VSMC may provide important insights that could lead to the development of strategies to limit the VSMC accumulation leading to neointimal formation and enhance VSMC proliferation and matrix production to stabilize advanced atherosclerotic plaques.
Regulated gene expression is essential for the maintenance of normal vessel structure and function and, not surprisingly, the expression of multiple genes is altered in the vasculoproliferative disorders and atherosclerosis. Recent comprehensive reviews broadly summarize regulation of gene transcription in the vessel wall and in VSMC and suggest that transcriptional modulation of genes involved in cholesterol and fatty acid metabolism, inflammation, and cell cycle progression may hold promise as favorable therapeutic approaches to limit atherosclerosis and the vascular response to injury.11,12 Transcription factors implicated in regulating these processes (such as the sterol responsive element-binding protein , nuclear factor kappa B, E2F, and others) and their target genes (low-density lipoprotein receptor, adhesion molecules, cytokines, and cell cycle proteins) are known.11 However, the transcription factors and mechanisms that link phenotypic modulation and growth regulation in VSMC are poorly understood. Several classes of transcription factors are known or likely to be involved in the regulation of VSMC differentiation and, in some instances, proliferation.13 Notably, the HLH class of transcription factors is able to modulate both the expression of VSMC-specific and cell cycle regulatory genes. Subsequent studies provide evidence implicating the Id (Inhibitor of DNA binding) class of HLH factors as regulators of growth and differentiation in VSMC and during vascular lesion formation.14,15 Thus, the focus of this review is on summarizing what is known regarding the role of the HLH proteins, particularly the Id factors, in regulating these processes in VSMC and during lesion formation. First, however, we briefly overview transcription factor classes and HLH factor involvement in the vasculature.
HLH Transcription Factors
Transcription factors can be broadly categorized into 4 superclasses—those containing basic domains (superclass 1), those containing zinc-coordinated DNA binding domains (superclass 2), those containing helix-turn-helix domains (superclass 3), and ?-scaffold factors (superclass 4). In the vasculature, transcription factors from all 4 superclasses are expressed and contribute to vessel homeostasis. Transcription factors in superclass 1 can be further divided based on what specific motif(s) are present. One example is a basic HLH motif. Transcription factors containing the basic HLH (bHLH) motif all share a highly conserved HLH region, which mediates protein–protein interactions, as well as a basic DNA binding domain. bHLH factors activate transcription by forming homodimers or heterodimers that bind CANNTG consensus sequences, termed E-boxes, in the promoter region of responsive genes.
There are >240 HLH proteins identified; thus, a classification scheme based on tissue distribution, DNA-binding specificities, and dimerization capabilities has been devised.16 Class I HLH factors (known as E proteins) are bHLH factors that are expressed in many tissues including VSMC.17,18 E proteins such as E12, E47, HEB, and E2–2 can form homodimers or heterodimers with class II bHLH factors. Heterodimerization with class II bHLH proteins leads to activation of cell type-specific genes and cellular differentiation. Class II HLH proteins are tissue-restricted factors including MyoD and NeuroD.19,20 Factors belonging to this class (such as eHAND, dHAND, and capsulin/epicardin)21–23 have been implicated in the regulation of VSMC differentiation, although their specific target genes in VSMC are unknown. Class III HLH factors have a leucine zipper adjacent to the HLH motif (bHLH-LZ) and include c-Myc, E2F, and SREBP. Antisense-mediated c-Myc inhibition is capable of inhibiting VSMC growth and neointimal formation in response to injury in a rabbit and porcine model.24,25 E2F inhibition using "decoy" double-stranded oligonucleotides that contain consensus E2F binding sites reduced VSMC proliferation and lesion formation in response to balloon injury in porcine and rat arteries, as well as in response to vein grafting in rabbits and humans.26–28 SREBP mediates cholesterol-induced effects on gene transcription in VSMC.29 Class IV HLH proteins including Mad, Max, and Mxi dimerize with Myc and regulate Myc function.30,31 The Id class of HLH proteins (class V) lacks the basic DNA-binding domain and are dominant-negative regulators of class I and class II bHLH proteins.32 The role of Id in the vasculature is discussed in detail in later sections. Class VI HLH factors contain a proline in their basic region and include the Drosophila proteins Hairy and Enhancer of split. Cardiovascular HLH factor 1 (CHF1) is an HLH protein closely related to Hairy, although there is a substitution of glycine for proline in the basic region. CHF1 is expressed in differentiated VSMC and in the developing aorta, although specific VSMC targets of CHF1 are unknown.33 Lastly, the class VII HLH proteins contain a bHLH-Per-Arnt-Sim (bHLH-PAS) domain. bHLH-PAS factors implicated in VSMC and in vascular disease include hypoxia-inducible factor 1, which regulates expression of plasminogen activator inhibitor-1 and vascular endothelial growth factors in VSMC,34 and the clock proteins that regulate vascular circadian gene expression.35
Id Proteins
Id proteins consist of 4 members (Id1–4) that belong to the class V HLH family of transcription factors. Unlike bHLH factors, the Id (Inhibitor of DNA binding) proteins lack the basic DNA binding region altogether. Id proteins form inactive heterodimers with ubiquitously expressed class I bHLH factors and thus act as dominant-negative inhibitors of bHLH function (Figure 1). Whereas class I HLH factors are the primary target of Id proteins, Id also regulates class II HLH factor function because (with few exceptions) class II factors are incapable of forming homodimers and preferentially heterodimerize with class I E proteins36. Class I and class II HLH factors regulate the transcription of cell cycle genes,37–42 and class II factors also regulate the expression of cell type-specific genes and the differentiated phenotype.43–45 Thus, the Id proteins are likely candidates to mediate the cross-talk between pathways that regulate growth and pathways that regulate the differentiated phenotype in VSMC.
Figure 1. Principal mechanism of Id action. A, Transactivation of an E-box containing promoter by a bHLH dimer. Heterodimers of bHLH transcription factors interact via HLH dimerization motifs. These dimers bind to consensus sites present in the promoter regions of responsive genes by virtue of their basic DNA binding domains. Binding to consensus sites, termed E-boxes, functions to recruit transcriptional coactivators, activating transcription. B, Inhibition of bHLH transactivation by Id proteins. Id proteins form heterodimers with bHLH factors. Because Id proteins lack basic DNA-binding motifs, the resulting Id-bHLH dimer is unable to bind DNA and cannot activate transcription. Thus, the Id proteins function principally as dominant-negative transcriptional regulators.
In addition to the common HLH domain that mediates Id dimerization, each Id protein has unique features that may regulate specific functional roles. Id2, Id3, and Id4, but not Id1, contain a consensus cdk2 phosphorylation site in their N-terminus and are phosphorylated by cyclin-cdk2 complexes, an event that alters the specificity of Id2 and Id3 in blocking bHLH dimers from binding E-box sequences in vitro.46,47 Phosphorylation of Id2 is required for transcriptional inhibition of p21Cip1 and cell cycle entry in VSMC.47 Furthermore, the C-terminal regions of the Id proteins differ dramatically (Figure 2). This is especially important because alterations in the C-termini of Id proteins have been shown to regulate protein stability and dominant-negative function.48,49 Two Id members, Id1 and Id3, have alternatively spliced isoforms. In rats these alternative isoforms, termed Id1.25 and Id3a, are found in cardiac and VSMCs. Interestingly, Id1.25 and Id3a appear to be generated by intron retention, resulting in alternative message products encoding unique C-termini.17,49 Id proteins can also dimerize with the class III bHLH-LZ protein SREBP50 and transcription factors that do not contain an HLH domain such as the ETS-domain factors,51 MIDA1,52 PAX-domain factors,53 and pRb.54,55 The specific role of domains within the Id proteins and their role in mediating Id partner specificity are poorly understood.
Figure 2. The Id family of proteins. Shown are the peptide sequences of the Id family members. The HLH dimerization motif, highly conserved among family members, is boxed in green. The N-terminal cdk-2 phosphorylation site present in Id2, Id3, Id3a, and Id4 is boxed in red. Unique C-terminal sequences generated by intron retention in Id1 and Id3 are boxed in blue.
Ids and the Cell Cycle
Id expression is upregulated after mitogen stimulation in a variety of cell types, and ectopic Id expression can promote cellular proliferation.38,55,56 However, whereas the Ids can all promote growth, and the general dominant-negative paradigm of Id function is common among family members, accumulating evidence indicates that the specific roles of these proteins in regulating growth are not redundant.55,56 Antisense inhibition of any 1 of the 4 Ids is sufficient to abrogate serum-stimulated proliferation in fibroblasts.56
Regulation of cell cycle progression represents a major means whereby the Id proteins affect cellular growth, and the specific mechanisms whereby this is accomplished are beginning to be elucidated. One major mechanism involves the regulation of cyclin-dependent kinase (cdk) inhibitors, including p16INK4, p21Cip1, and p27Waf1. The cdk inhibitors modulate the formation and/or function of cyclin–cdk complexes that regulate progression of the cell cycle.57 Expression of p21Cip1 and p27Waf1 is elevated in terminally differentiated cells, and ectopic expression of p16INK4, p21Cip1, and p27Waf1 results in cell-cycle arrest and a decrease of cellular growth in a variety of cell types, including VSMC.42,58,59 The promoter regions of p16INK4 and p21Cip1 contain multiple E-boxes, and several bHLH factors, including E47, are capable of stimulating p16INK4 and p21Cip1 transcription.37–39 Consistent with this paradigm, Id1, Id2, and Id3 can inhibit p21Cip1 and p16INK4 transcription in fibroblasts and VSMC.15,37,55 Therefore, by acting as dominant-negative transcriptional regulators of cyclin-dependent kinase inhibitors, the Ids can promote entry into the cell cycle and stimulate cellular growth.
A second mechanism whereby Id proteins promote cellular growth appears to be specific to Id2 and involves inactivation of the retinoblastoma protein (pRb). E2F, a transcription factor that activates a variety of genes required for cell cycle progression, is normally inactive by virtue of its association with pRb. Phosphorylation of pRb by cyclin/cdk complexes causes dissociation of the pRb/E2F complex, releasing E2F and allowing for cell cycle progression.57 Id2 (but not Id1 or Id3) is also able to promote complex dissociation, leading to enhanced cell cycle progression, via an interaction between the HLH region of Id2 and the pocket domain of pRb.54,55
Ids Mediate Mitogen-Induced VSMC Growth
Accumulating evidence suggests that the Id proteins are mediators of several mitogenic factors involved in VSMC growth. Such factors act generally through receptor tyrosine kinases to stimulate classical mitogenic pathways, eg, the mitogen-activated protein kinase (MAPK) pathway.60 Receptor tyrosine kinase stimulation by PDGF or serum increases both Id expression and VSMC growth.56,61 Further, activation of protein kinase C or Ras is capable of upregulating Id3 expression, whereas this effect is blocked by either Ras or MAPK inhibition.62
Receptor tyrosine kinase-mediated MAPK activation results in increased transcription of early growth response gene product 1 (Egr-1). Egr-1 is upregulated in vivo in restenotic and atherosclerotic lesions, and Egr-1 inhibition reduces formation of both types of lesions in vivo.63–67 Interestingly, Egr-1 enhances expression of Id3 message, providing a link between mitogen or injury-induced Egr-1 and Id expression.68 Another immediate–early response gene, c-Myc, activates Id2 transcription. c-Myc is also upregulated after vascular injury, with c-Myc inhibition attenuating VSMC proliferation in vitro and restenosis in rat and porcine models of angioplasty.24 c-Myc has recently been shown to bind the Id2 promoter and upregulate Id2 message levels. Of importance, Id2 is required for the mitogenic effects of c-Myc, because cells from Id2–/– mice, but not wild-type controls, are unresponsive to c-Myc simulation.69
Angiotensin II (Ang II) is another VSMC mitogen. Ang II acts through AT1 angiotensin receptors to induce reactive oxygen species (ROS) production and growth in the VSMC.70 ROS act as signaling molecules, mediating the mitogenic effects of Ang II via activation of mitogenic pathways, including the MAPK cascade. Ang II is also capable of stimulating receptor tyrosine phosphorylation and activation of the MAPK pathway.61 Ang II is released after vascular injury, promotes VSMC growth and proliferation, and the mitogenic properties of Ang II have been shown to contribute to atherogenesis.71–73 Mueller et al have recently identified Id3 as a message that is upregulated, in a MAPK-dependent manner, in cultured VSMC treated with Ang II.74,75 VSMCs treated with Ang II or ROS also displayed increased cell number and cell-cycle entry, and these effects were abrogated by Id3 antisense inhibition. Further, Ang II/ROS treatment decreased expression of p21Cip1 4 hours after treatment, coincident with Id3 induction.74 Thus, regulation of Id3 expression appears to be an important, indeed necessary, mechanism by which Ang II stimulates VSMC growth.
The Ids and VSMC Differentiation
In addition to their growth-promoting properties, the Id proteins can also act as negative regulators of cellular differentiation. Ectopic expression of Id proteins inhibits cellular differentiation in several cell line models, including myoblasts, epithelial cells, pre-adipocytes, and osteosarcoma cells, and expression of Id genes is significantly reduced on terminal differentiation of a variety of cell types, including myoblasts.55,76–80 Id proteins likely regulate differentiation via functional antagonism of bHLH factors well-characterized as promoters of cellular differentiation, such as MyoD and NeuroD.81
Modulation of VSMC phenotype, notably alteration of the VSMC differentiated state, is a hallmark of vascular lesion formation in both the vasculoproliferative disorders and the development of atherosclerosis.82 The primary function of differentiated VSMC is to contract; thus, expression of SM-specific contractile proteins, such as SM -actin, is commonly used as an indicator of VSMC differentiation. Strong evidence for HLH involvement in the regulation of VSMC differentiation includes data published by Kumar et al, demonstrating that consensus bHLH DNA binding sites (E-boxes) are essential for SM -actin promoter activation in vivo.14 Although several bHLH factors, including E12, E47, dHAND, and HES-2, are in fact expressed in VSMC, it is unclear whether these are involved in regulating VSMC differentiation in vivo.21,83–85 In vitro, ectopic expression of bHLH factors can drive SM -actin expression in VSMC; importantly, coexpression of Id2 or Id3 abrogates this effect.14 It is therefore intriguing to think that the de-differentiation of VSMC after injury is mediated by the Id proteins. In vivo expression of VSMC differentiation markers, including SM -actin, decreases after vascular injury at time points coincident with upregulation of Id2 and Id3.82 Therefore, the Id proteins are likely important mediators of the differentiated state of VSMC during lesion formation, although this has not yet been directly addressed.
Id Expression During Vascular Lesion Formation
Given that the Ids regulate VSMC growth and differentiation, it is not surprising that Id proteins have been implicated as modulators of vascular lesion development. Most of the in vivo data to date involve Id3. Id3 message expression in the vessel wall is significantly increased after balloon endothelial denudation in a rat carotid injury model. Id3, expressed at low levels in normal vessels, is increased within 3 days of injury and remains high through 14 days postinjury, corresponding to the time of peak VSMC proliferation and lesion development.17,86 In addition, Nickening et al have recently shown that Id3 protein expression is also induced in vivo after wire injury of mouse carotid arteries, further implicating Id3 involvement in the vascular proliferative response to mechanical injury.75
In contrast to Id3, intron-containing Id3a message is absent from normal vessels and quiescent VSMC is strongly induced after balloon injury in rats and remains high through 28 days after injury. Interestingly, the human homologue of Id3a, Id3L, is expressed in advanced human atherosclerotic plaques, particularly in regions rich in VSMC (Figure 3).17 Moreover, gene delivery of Id3a, found to induce apoptosis and inhibit Id3 expression in VSMC, reduced the neointima-to-media ratio in response to balloon endothelial denudation in rats by 55%.15
Figure 3. Id3L mRNA is expressed in human carotid atherosclerotic plaques. In situ hybridization of a representative human carotid endarterectomy specimen with use of digoxigenin-labeled antisense Id3L riboprobe reveals Id3L mRNA expression in discreet areas within the specimens (A). No staining is seen in a contigu-ous section of this specimen hybridized with the corresponding sense probe (B). Immunohistochemical staining of a contiguous section with a monoclonal antibody against smooth muscle -actin (C, D ) reveals positive diaminobenzidine (brown) staining in areas of Id3L mRNA staining (hematoxylin counterstain).
Id2 expression is also modulated in vivo in a rat carotid injury model. Normally absent from the vessel wall, Id2 protein expression is induced by 6 days after balloon injury and remains high through 14 days. Like Id3, Id2 expression corresponds to peak cellular growth in the developing lesion. Id2 expression is declining by 28 days postinjury and is not seen in fully developed lesions.87 Expression of Id1 and Id4 in the vasculature has not yet been examined.
Id Involvement in Angiogenesis
Interesting in vivo data regarding Id function in the vasculature have recently been published by Lyden et al. This group generated Id3–/– Id1–/– double-knockout mice for developmental studies, but the mice are nonviable. They die in utero at E12.5 because of vascular abnormalities, which lead to intracranial hemorrhage. Results in earlier embryos demonstrated that the Id1–Id3 double-knockout mice have premature withdrawal of neuroblasts from the cell cycle and expression of neural-specific differentiation markers. However, Id1+/– Id3–/– mice were viable. An unexpected but exciting finding was that these mice had a marked attenuation of tumor vascularization and angiogenesis, providing the first in vivo evidence that the presence of Id3 is critical to the vasculature.88 These results are particularly relevant because angiogenesis is a process involving extensive VSMC migration, matrix secretion, and proliferation—themes held in common with the vascular response to injury—and is a critical process in atherosclerotic lesion progression.89–92
Summary
There is clear evidence that the Id proteins regulate VSMC growth and differentiation, key components of the vasculoproliferative disorders. Ids act to inhibit expression of genes that inhibit cell cycle progression, as well as genes specific for differentiated VSMC. Thus, Id proteins provide an important link between these 2 processes in the vasculature. Id expression is upregulated in developing restenotic lesions and is an important player in the signaling cascades activated by mitogens released after vascular injury.
The work reviewed provides evidence that Id proteins are key regulators of VSMC biology; however, important questions regarding the role of Ids in vascular disease remain unanswered. How are expression and function of the Id proteins coordinately regulated in VSMC in response to injury? What are the other important cell cycle factors regulated by Id proteins? Do the Id proteins regulate other processes in VSMC such as migration or matrix production? What bHLH factors do Id proteins regulate in VSMC and in the vessel wall? Do Id deletions or mutations alter susceptibility to vascular disease? Clearly, much further research in this area is needed, because a more complete understanding of how Id proteins regulate VSMC growth and differentiation and vascular lesion formation is essential to elucidating the molecular mechanisms of lesion development.
Acknowledgments
This review was supported by National Institutes of Health grants T32HL007284 (S.T.F.), RO1 HL062522, and PO1 HL55798 (C.A.M.). We thank Drs Gary Owens and Amy Tucker for helpful comments on the manuscript.
References
Hart CE, Kraiss LW, Vergel S, Gilbertson D, Kenagy R, Kirkman T, Crandall DL, Tickle S, Finney H, Yarranton G, Clowes AW. PDGF? receptor blockade inhibits intimal hyperplasia in the baboon. Circulation. 1999; 99: 564–569.
Wang X, Romanic AM, Yue TL, Feuerstein GZ, Ohlstein EH. Expression of interleukin-1?, interleukin-1 receptor, and interleukin-1 receptor antagonist mRNA in rat carotid artery after balloon angioplasty. Biochem Biophys Res Com. 2000; 271: 138–143.
Hatton MW, Moar SL, Richardson M. Deendothelialization in vivo initiates a thrombogenic reaction at the rabbit aorta surface. Correlation of uptake of fibrinogen and antithrombin III with thrombin generation by the exposed subendothelium. Am J Pathol. 1989; 135: 499–508.
Ferns GA, Raines EW, Sprugel KH, Motani AS, Reidy MA, Ross R. Inhibition of neointimal smooth muscle accumulation after angioplasty by an antibody to PDGF. Science. 1991; 253: 1129–1132.
Lindner V, Reidy MA. Proliferation of smooth muscle cells after vascular injury is inhibited by an antibody against basic fibroblast growth factor. Proc Natl Acad Sci U S A. 1991; 1988: 3739–3743.
Dzau VJ, Braun-Dullaeus RC, Sedding DG. Vascular proliferation and atherosclerosis: new perspectives and therapeutic strategies. Nat Med. 2002; 8: 1249–1256.
Lafont A, Libby P. The smooth muscle cell: sinner or saint in restenosis and the acute coronary syndromes? J Am Coll Cardiol. 1998; 32: 283–285.
Mosse PR, Campbell GR, Wang ZL, Campbell JH. Smooth muscle phenotypic expression in human carotid arteries. I. Comparison of cells from diffuse intimal thickenings adjacent to atheromatous plaques with those of the media. Lab Invest. 1985; 53: 556–562.
Braganza DM, Bennett MR. New insights into atherosclerotic plaque rupture. Postgrad Med J. 2001; 77: 94–98.
Lusis AJ. Atherosclerosis. Nature. 2000; 407: 233–241.
de Nigris F, Lerman LO, Napoli C. New insights in the transcriptional activity and coregulator molecules in the arterial wall. Int J Cardiol. 2002; 86: 153–168.
Walsh K, Takahashi A. Transcriptional regulation of vascular smooth muscle cell phenotype. Z Kardiol. 2001; 90 (suppl 3): 12–16.
Kumar MS, Owens GK. Combinatorial control of smooth muscle-specific gene expression. Arterioscler Thromb Vasc Biol. 2003; 23: 737–747.
Kumar MS, Hendrix JA, Johnson AD, Owens GK. Smooth muscle -actin gene requires two E-boxes for proper expression in vivo and is a target of class I basic helix-loop-helix proteins. Circ Res. 2003; 92: 840–847.
Forrest ST, Barringhaus KG, Perlegras D, Hammarskjold ML, McNamara CA. Intron retention generates a novel Id3 isoform that inhibits vascular lesion formation. J Biol Chem. 2004; 279: 32897–32903.
Murre C, Bain G, van Dijk MA, Engel I, Furnari BA, Massari ME, Matthews JR, Quong MW, Rivera RR, Stuiver MH. Structure and function of helix-loop-helix proteins. Biochim Biophys Acta. 1994; 1218: 129–135.
Matsumura ME, Li F, Berthoux L, Wei B, Lobe DR, Jeon C, Hammarskjold ML, McNamara CA. Vascular injury induces posttranscriptional regulation of the Id3 gene: cloning of a novel Id3 isoform expressed during vascular lesion formation in rat and human atherosclerosis. Arterioscler Thromb Vasc Biol. 2001; 21: 752–758.
Massari ME, Murre C. Helix-loop-helix proteins: regulators of transcription in eucaryotic organisms. Mol Cell Biol. 2000; 20: 429–440.
Lau LF, Nathans D. Identification of a set of genes expressed during the G0/G1 transition of cultured mouse cells. EMBO J. 1985; 4: 3145–3151.
Shi Y, O’Brien JE Jr, Ala-Kokko L, Chung W, Mannion JD, Zalewski A. Origin of extracellular matrix synthesis during coronary repair. Circulation. 1997; 95: 997–1006.
Yamagishi H, Olson EN, Srivastava D. The basic helix-loop-helix transcription factor, dHAND, is required for vascular development. J Clin Invest. 2000; 105: 261–270.
Hollenberg SM, Sternglanz R, Cheng PF, Weintraub H. Identification of a new family of tissue-specific basic helix-loop-helix proteins with a two-hybrid system. Mol Cell Biol. 1995; 15: 3813–3822.
Hidai H, Bardales R, Goodwin R, Quertermous T, Quertermous EE. Cloning of capsulin, a basic helix-loop-helix factor expressed in progenitor cells of the pericardium and the coronary arteries. Mech Dev. 1998; 73: 33–43.
Kipshidze N, Iversen P, Keane E, Stein D, Chawla P, Skrinska V, Shankar LR, Mehran R, Chekanov V, Dangas G, Komorowski R, Haudenschild C, Khanna A, Leon M, Keelan MH, Moses J. Complete vascular healing and sustained suppression of neointimal thickening after local delivery of advanced c-myc antisense at six months follow-up in a rabbit balloon injury model. Cardiovasc Radiat Med. 2002; 3: 26–30.
Kipshidze N, Keane E, Stein D, Chawla P, Skrinska V, Shankar LR, Khanna A, Komorowski R, Haudenschild C, Iversen P, Leon MB, Keelan MH, Moses J. Local delivery of c-myc neutrally charged antisense oligonucleotides with transport catheter inhibits myointimal hyperplasia and positively affects vascular remodeling in the rabbit balloon injury model. Catheter Cardiovasc Interv. 2001; 1954: 247–256.
Nakamura T, Morishita R, Asai T, Tsuboniwa N, Aoki M, Sakonjo H, Yamasaki K, Hashiya N, Kaneda Y, Ogihara T. Molecular strategy using cis-element ‘decoy’ of E2F binding site inhibits neointimal formation in porcine balloon-injured coronary artery model. Gene Ther. 2002; 1909: 488–494.
Aoki M, Morishita R, Matsushita H, Hayashi S, Nakagami H, Yamamoto K, Moriguchi A, Kaneda Y, Higaki J, Ogihara T. Inhibition of the p53 tumor suppressor gene results in growth of human aortic vascular smooth muscle cells. Potential role of p53 in regulation of vascular smooth muscle cell growth. Hypertension. 1999; 34: 192–200.
Morishita R, Gibbons GH, Horiuchi M, Ellison KE, Nakama M, Zhang L, Kaneda Y, Ogihara T, Dzau VJ. A gene therapy strategy using a transcription factor decoy of the E2F binding site inhibits smooth muscle proliferation in vivo. Proc Natl Acad Sci U S A. 1995; 92: 5855–5859.
Llorente-Cortes V, Otero-Vinas M, Sanchez S, Rodriguez C, Badimon L. Low-density lipoprotein upregulates low-density lipoprotein receptor-related protein expression in vascular smooth muscle cells: possible involvement of sterol regulatory element binding protein-2-dependent mechanism. Circulation. 2002; 106: 3104–3110.
Ayer DE, Lawrence QA, Eisenman RN. Mad-Max transcriptional repression is mediated by ternary complex formation with mammalian homologs of yeast repressor Sin3. Cell. 1995; 80: 767–776.
Ayer DE, Kretzner L, Eisenman RN. Mad: a heterodimeric partner for Max that antagonizes Myc transcriptional activity. Cell. 1993; 72: 211–222.
Benezra R, Davis RL, Lockshon D, Turner DL, Weintraub H. The protein Id: a negative regulator of helix-loop-helix DNA binding proteins. Cell. 1990; 61: 49–59.
Chin MT, Maemura K, Fukumoto S, Jain MK, Layne MD, Watanabe M, Hsieh CM, Lee ME. Cardiovascular basic helix loop helix factor 1, a novel transcriptional repressor expressed preferentially in the developing and adult cardiovascular system. J Biol Chem. 2000; 275: 6381–6387.
Gorlach A, Diebold I, Schini-Kerth VB, Berchner-Pfannschmidt U, Roth U, Brandes RP, Kietzmann T, Busse R. Thrombin activates the hypoxia-inducible factor-1 signaling pathway in vascular smooth muscle cells: Role of the p22(phox)-containing NADPH oxidase. Circ Res. 2001; 89: 47–54.
Curtis AM, Seo SB, Westgate EJ, Rudic RD, Smyth EM, Chakravarti D, FitzGerald GA, McNamara P. Histone acetyltransferase-dependent chromatin remodeling and the vascular clock. J Biol Chem. 2004; 279: 7091–7097.
Murre C, McCaw PS, Vaessin H, Caudy M, Jan LY, Jan YN, Cabrera CV, Buskin JN, Hauschka SD, Lassar AB. Interactions between heterologous helix-loop-helix proteins generate complexes that bind specifically to a common DNA sequence. Cell. 1989; 58: 537–544.
Prabhu S, Ignatova A, Park ST, Sun XH. Regulation of the expression of cyclin-dependent kinase inhibitor p21 by E2A and Id proteins. Mol Cell Biol. 1997; 17: 5888–5896.
Peverali FA, Ramqvist T, Saffrich R, Pepperkok R, Barone MV, Philipson L. Regulation of G1 progression by E2A and Id helix-loop-helix proteins. EMBO J. 1994; 13: 4291–4301.
Pagliuca A, Gallo P, De Luca P, Lania L. Class A helix-loop-helix proteins are positive regulators of several cyclin-dependent kinase inhibitors’ promoter activity and negatively affect cell growth. Cancer Res. 2000; 60: 1376–1382.
Zhao F, Vilardi A, Neely RJ, Choi JK. Promotion of cell cycle progression by basic helix-loop-helix E2A. Mol Cell Biol. 2001; 21: 6346–6357.
Guo K, Wang J, Andres V, Smith RC, Walsh K. MyoD-induced expression of p21 inhibits cyclin-dependent kinase activity upon myocyte terminal differentiation. Mol Cell Biol. 1995; 15: 3823–3829.
Halevy O, Novitch BG, Spicer DB, Skapek SX, Rhee J, Hannon GJ, Beach D, Lassar AB. Correlation of terminal cell cycle arrest of skeletal muscle with induction of p21 by MyoD. Science. 1995; 267: 1018–1021.
Choi J, Costa ML, Mermelstein CS, Chagas C, Holtzer S, Holtzer H. MyoD converts primary dermal fibroblasts, chondroblasts, smooth muscle, and retinal pigmented epithelial cells into striated mononucleated myoblasts and multinucleated myotubes. Proc Natl Acad Sci U S A. 1990; 87: 7988–7992.
Lassar AB, Buskin JN, Lockshon D, Davis RL, Apone S, Hauschka SD, Weintraub H. MyoD is a sequence-specific DNA binding protein requiring a region of myc homology to bind to the muscle creatine kinase enhancer. Cell. 1989; 58: 823–831.
French BA, Chow KL, Olson EN, Schwartz RJ. Heterodimers of myogenic helix-loop-helix regulatory factors and E12 bind a complex element governing myogenic induction of the avian cardiac -actin promoter. Mol Cell Biol. 1991; 11: 2439–2450.
Hara E, Hall M, Peters G. Cdk2-dependent phosphorylation of Id2 modulates activity of E2A-related transcription factors. EMBO J. 1997; 16: 332–342.
Deed RW, Hara E, Atherton GT, Peters G, Norton JD. Regulation of Id3 cell cycle function by Cdk-2-dependent phosphorylation. Mol Cell Biol. 1997; 17: 6815–6821.
Chen B, Han BH, Sun XH, Lim RW. Inhibition of muscle-specific gene expression by Id3: requirement of the C-terminal region of the protein for stable expression and function. Nucleic Acids Res. 1997; 25: 423–430.
Springhorn JP, Singh K, Kelly RA, Smith TW. Posttranscriptional regulation of Id1 activity in cardiac muscle. Alternative splicing of novel Id1 transcript permits homodimerization. J Biol Chem. 1994; 269: 5132–5136.
Moldes M, Boizard M, Liepvre XL, Feve B, Dugail I, Pairault J. Functional antagonism between inhibitor of DNA binding (Id) and adipocyte determination and differentiation factor 1/sterol regulatory element-binding protein-1c (ADD1/SREBP-1c) trans-factors for the regulation of fatty acid synthase promoter in adipocytes. Biochem J. 1999; 344: t-80.
Yates PR, Atherton GT, Deed RW, Norton JD, Sharrocks AD. Id helix-loop-helix proteins inhibit nucleoprotein complex formation by the TCF ETS-domain transcription factors. EMBO J. 1999; 18: 968–976.
Shoji W, Inoue T, Yamamoto T, Obinata M. MIDA1, a protein associated with Id, regulates cell growth. J Biol Chem. 1995; 270: 24818–24825.
Roberts EC, Deed RW, Inoue T, Norton JD, Sharrocks AD. Id Helix-Loop-Helix Proteins Antagonize Pax Transcription Factor Activity by Inhibiting DNA Binding. Mol Cell Biol. 2001; 21: 524–533.
Lasorella A, Iavarone A, Israel MA. Id2 specifically alters regulation of the cell cycle by tumor suppressor proteins. Mol Cell Biol. 1996; 16: 2570–2578.
Iavarone A, Garg P, Lasorella A, Hsu J, Israel MA. The helix-loop-helix protein Id-2 enhances cell proliferation and binds to the retinoblastoma protein. Genes Dev. 1994; 8: 1270–1284.
Barone MV, Pepperkok R, Peverali FA, Philipson L. Id proteins control growth induction in mammalian cells. Proc Natl Acad Sci U S A. 1994; 91: 4985–4988.
Sherr CJ, Roberts JM. CDK inhibitors: positive and negative regulators of G1-phase progression. Genes Dev. 1999; 13: 1501–1512.
Tanner FC, Boehm M, Akyurek LM, San H, Yang ZY, Tashiro J, Nabel GJ, Nabel EG. Differential effects of the cyclin-dependent kinase inhibitors p27(Kip1), p21(Cip1), and p16(Ink4) on vascular smooth muscle cell proliferation. Circulation. 2000; 101: 2022–2025.
Yang ZY, Simari RD, Perkins ND, San H, Gordon D, Nabel GJ, Nabel EG. Role of the p21 cyclin-dependent kinase inhibitor in limiting intimal cell proliferation in response to arterial injury. Proc Natl Acad Sci U S A. 1996; 93: 7905–7910.
Heldin CH, Westermark B. Mechanism of action and in vivo role of platelet-derived growth factor. Physiol Rev. 1999; 79: 1283–1316.
Linseman DA, Benjamin CW, Jones DA. Convergence of angiotensin II and platelet-derived growth factor receptor signaling cascades in vascular smooth muscle cells. J Biol Chem. 1995; 270: 12563–12568.
Bain G, Cravatt CB, Loomans C, Alberola-Ila J, Hedrick SM, Murre C. Regulation of the helix-loop-helix proteins, E2A and Id3, by the Ras- ERK MAPK cascade. Nat Immunol. 2001; 2: 165–171.
Khachigian LM, Lindner V, Williams AJ, Collins T. Egr-1-induced endothelial gene expression: a common theme in vascular injury. Science. 1996; 271: 1427–1431.
McCaffrey TA, Fu C, Du B, Eksinar S, Kent KC, Bush H Jr, Kreiger K, Rosengart T, Cybulsky MI, Silverman ES, Collins T. High-level expression of Egr-1 and Egr-1-inducible genes in mouse and human atherosclerosis. J Clin Invest. 2000; 105: 653–662.
Lowe HC, Fahmy RG, Kavurma MM, Baker A, Chesterman CN, Khachigian LM. Catalytic oligodeoxynucleotides define a key regulatory role for early growth response factor-1 in the porcine model of coronary in-stent restenosis. Circ Res. 2001; 89: 670–677.
Harja E, Bucciarelli LG, Lu Y, Stern DM, Zou YS, Schmidt AM, Yan SF. Early growth response-1 promotes atherogenesis: mice deficient in early growth response-1 and apolipoprotein E display decreased atherosclerosis and vascular inflammation. Circ Res. 2004; 94: 333–339.
Santiago FS, Lowe HC, Kavurma MM, Chesterman CN, Baker A, Atkins DG, Khachigian LM. New DNA enzyme targeting Egr-1 mRNA inhibits vascular smooth muscle proliferation and regrowth after injury. Nat Med. 1999; 5: 1264–1269.
Bettini M, Xi H, Milbrandt J, Kersh GJ. Thymocyte Development in Early Growth Response Gene 1-Deficient Mice. J Immunol. 2002; 169: 1713–1720.
Lasorella A, Noseda M, Beyna M, Yokota Y, Iavarone A. Id2 is a retinoblastoma protein target and mediates signalling by Myc oncoproteins. Nature. 2000Oct 5; 407: 592–598.
Griendling KK, Ushio-Fukai M. Reactive oxygen species as mediators of angiotensin II signaling. Regul Pept. 2000; 91: 21–27.
Badimon JJ, Fuster V, Chesebro JH, Badimon L. Coronary atherosclerosis. A multifactorial disease. Circulation. 1993; 87 (3 Suppl): II3–II16.
The HOPE (Heart Outcomes Prevention Evaluation) Study: the design of a large, simple randomized trial of an angiotensin-converting enzyme inhibitor (ramipril) and vitamin E in patients at high risk of cardiovascular events. The HOPE study investigators. Can J Cardiol. 1996; 12: 127–137.
Eto H, Biro S, Miyata M, Kaieda H, Obata H, Kihara T, Orihara K, Tei C. Angiotensin II type 1 receptor participates in extracellular matrix production in the late stage of remodeling after vascular injury. Cardiovasc Res. 2003; 59: 200–211.
Mueller C, Baudler S, Welzel H, Bohm M, Nickenig G. Identification of a novel redox-sensitive gene, Id3, which mediates angiotensin II-induced cell growth. Circulation. 2002; 105: 2423–2428.
Nickenig G, Baudler S, Muller C, Werner C, Werner N, Welzel H, Strehlow K, Bohm M. Redox-sensitive vascular smooth muscle cell proliferation is mediated by GKLF and Id3 in vitro and in vivo. FASEB J. 2002; 16: 1077–1086.
Kreider BL, Benezra R, Rovera G, Kadesch T. Inhibition of myeloid differentiation by the helix-loop-helix protein Id. Science. 1992; 255: 1700–1702.
Jen Y, Weintraub H, Benezra R. Overexpression of Id protein inhibits the muscle differentiation program: in vivo association of Id with E2A proteins. Genes Dev. 1992; 6: 1466–1479.
Desprez PY, Hara E, Bissell MJ, Campisi J. Suppression of mammary epithelial cell differentiation by the helix-loop-helix protein Id-1. Mol Cell Biol. 1995; 15: 3398–3404.
Atherton GT, Travers H, Deed R, Norton JD. Regulation of cell differentiation in C2C12 myoblasts by the Id3 helix-loop-helix protein. Cell Growth Differ. 1996; 7: 1059–1066.
Moldes M, Lasnier F, Feve B, Pairault J, Djian P. Id3 prevents differentiation of preadipose cells. Mol Cell Biol. 1997; 17: 1796–1804.
Norton JD. ID helix-loop-helix proteins in cell growth, differentiation and tumorigenesis. J Cell Sci. 2000; 113: 3897–3905.
Owens GK. Regulation of differentiation of vascular smooth muscle cells. Physiol Rev. 1995; 75: 487–517.
Inaba T, Gotoda T, Ishibashi S, Harada K, Ohsuga JI, Ohashi K, Yazaki Y, Yamada N. Transcription factor PU. 1 mediates induction of c-fms in vascular smooth muscle cells: a mechanism for phenotypic change to phagocytic cells. Mol Cell Biol. 1996; 16: 2264–2273.
Roberts VJ, Steenbergen R, Murre C. Localization of E2A mRNA expression in developing and adult rat tissues. Proc Natl Acad Sci U S A. 1993; 90: 7583–7587.
Ishibashi M, Sasai Y, Nakanishi S, Kageyama R. Molecular characterization of HES-2, a mammalian helix-loop-helix factor structurally related to Drosophila hairy and Enhancer of split. Eur J Biochem. 1993; 215: 645–652.
Clowes AW, Reidy MA, Clowes MM. Kinetics of cellular proliferation after arterial injury. I. Smooth muscle growth in the absence of endothelium. Lab Invest. 1983; 49: 327–333.
Matsumura ME, Lobe DR, McNamara CA. Contribution of the helix-loop-helix factor Id2 to regulation of vascular smooth muscle cell proliferation. J Biol Chem. 2001.
Lyden D, Hattori K, Dias S, Costa C, Blaikie P, Butros L, Chadburn A, Heissig B, Marks W, Witte L, Wu Y, Hicklin D, Zhu Z, Hackett NR, Crystal RG, Moore MA, Hajjar KA, Manova K, Benezra R, Rafii S. Impaired recruitment of bone-marrow-derived endothelial and hematopoietic precursor cells blocks tumor angiogenesis and growth. Nat Med. 2001; 7: 1194–1201.
Moulton KS, Heller E, Konerding MA, Flynn E, Palinski W, Folkman J. Angiogenesis inhibitors endostatin or TNP-470 reduce intimal neovascularization and plaque growth in apolipoprotein E-deficient mice. Circulation. 1999; 99: 1726–1732.
Boyle JJ, Wilson B, Bicknell R, Harrower S, Weissberg PL, Fan TP. Expression of angiogenic factor thymidine phosphorylase and angiogenesis in human atherosclerosis. J Pathol. 2000; 192: 234–242.
Moulton KS, Vakili K, Zurakowski D, Soliman M, Butterfield C, Sylvin E, Lo KM, Gillies S, Javaherian K, Folkman J. Inhibition of plaque neovascularization reduces macrophage accumulation and progression of advanced atherosclerosis. Proc Natl Acad Sci U S A. 2003; 100: 4736–4741.
Moulton KS. Plaque angiogenesis: its functions and regulation. Cold Spring Harb Symp Quant Biol. 2002; 67: 471–482.(Scott Forrest; Coleen McN)