The Four-and-a-half LIM Domain Protein 2 Regulates Vascular Smooth Muscle Phenotype and Vascular Tone

In response to vascular injury, differentiated vascular smooth muscle cells (vSMCs) undergo a unique process known as “phenotype modulation,” transitioning from a quiescent, “contractile” phenotype to a proliferative, “synthetic” state. We have demonstrated previously that the signaling pathway of bone morphogenetic proteins, members of the transforming growth factor β family, play a role in the induction and maintenance of a contractile phenotype in human primary pulmonary artery smooth muscle cells. In this study, we show that a four-and-a-half LIM domain protein 2 (FHL2) inhibits transcriptional activation of vSMC-specific genes mediated by the bone morphogenetic protein signaling pathway through the CArG box-binding proteins, such as serum response factor and members of the myocardin (Myocd) family. Interestingly, FHL2 does not affect recruitment of serum response factor or Myocd, however, it inhibits recruitment of a component of the SWI/SNF chromatin remodeling complex, Brg1, and RNA polymerase II, which are essential for the transcriptional activation. This is a novel mechanism of regulation of SMC-specific contractile genes by FHL2. Finally, aortic rings from homozygous FHL2-null mice display abnormalities in both endothelial-dependent and -independent relaxation, suggesting that FHL2 is essential for the regulation of vasomotor tone. In response to vascular injury, differentiated vascular smooth muscle cells (vSMCs) undergo a unique process known as “phenotype modulation,” transitioning from a quiescent, “contractile” phenotype to a proliferative, “synthetic” state. We have demonstrated previously that the signaling pathway of bone morphogenetic proteins, members of the transforming growth factor β family, play a role in the induction and maintenance of a contractile phenotype in human primary pulmonary artery smooth muscle cells. In this study, we show that a four-and-a-half LIM domain protein 2 (FHL2) inhibits transcriptional activation of vSMC-specific genes mediated by the bone morphogenetic protein signaling pathway through the CArG box-binding proteins, such as serum response factor and members of the myocardin (Myocd) family. Interestingly, FHL2 does not affect recruitment of serum response factor or Myocd, however, it inhibits recruitment of a component of the SWI/SNF chromatin remodeling complex, Brg1, and RNA polymerase II, which are essential for the transcriptional activation. This is a novel mechanism of regulation of SMC-specific contractile genes by FHL2. Finally, aortic rings from homozygous FHL2-null mice display abnormalities in both endothelial-dependent and -independent relaxation, suggesting that FHL2 is essential for the regulation of vasomotor tone. Unlike skeletal and cardiac muscle cells, vSMCs 2The abbreviations used are: vSMC, vascular smooth muscle cell; BMP, bone morphogenetic protein; PASMC, pulmonary artery smooth muscle cell; 10T½, C3H10T½ cell; TGF, transforming growth factor; IPAH, idiopathic pulmonary arterial hypertension; SMA, smooth muscle α-actin; SRF, serum response factor; FHL2, four-and-a-half LIM domain protein 2; PAH, pulmonary arterial hypertension; FBS, fetal bovine serum; siRNA, small interference RNA; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; CNN1, smooth muscle calponin; DAPI, 4′, 6-diamidino-2-phenylindole; ChIP, chromatin immunoprecipitation; Ach, acetylcholine; SNP, S-nitroprusside; qRT, quantitative reverse transcriptase; GFP, green fluorescent protein; siCtr, control siRNA; pol II, polymerase II; CTGF, connective tissue growth factor; WT, wild type; KO, knockout; IP, immunoprecipitation; Myocd, myocardin. never terminally differentiate, but are capable of transitioning to a synthetic phenotype characterized by decreased vSMC marker gene expression, increased matrix deposition, and responsiveness to signals that lead to increased migration and growth (1Owens G.K. Kumar M.S. Wamhoff B.R. Physiol. Rev. 2004; 84: 767-801Crossref PubMed Scopus (2598) Google Scholar). This plasticity is crucial for the normal development of vessels, homeostasis of blood pressure, and repair of injury, but it also contributes to the development of various vascular pathologies. Therefore, it is critical to understand the signaling pathways that modulate the phenotype of vSMCs to develop agents that can regulate aberrant vSMC responses in diseased vessels. Recently we demonstrated that the BMP signaling pathway plays an important role in the phenotype modulation of PASMCs. Activation of the BMP pathway is required not only for maintenance of the contractile phenotype in PASMCs, but also for induction of vSMC marker gene expression in non-SMCs, such as mouse mesenchymal C3H10T½ (10T½) cells (2Chan M.C. Nguyen P.H. Davis B.N. Ohoka N. Hayashi H. Du K. Lagna G. Hata A. Mol. Cell Biol. 2007; 27: 5776-5789Crossref PubMed Scopus (109) Google Scholar, 3Lagna G. Ku M.M. Nguyen P.H. Neuman N.A. Davis B.N. Hata A. J. Biol. Chem. 2007; 282: 37244-37255Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar, 4Davis B.N. Hilyard A.C. Lagna G. Hata A. Nature. 2008; 454: 56-61Crossref PubMed Scopus (1123) Google Scholar). BMPs are the largest group in the TGF β superfamily of growth factors and play a crucial role in various physiological processes (5Attisano L. Wrana J.L. Science. 2002; 296: 1646-1647Crossref PubMed Scopus (1134) Google Scholar, 6Heldin C.H. Miyazono K. ten Dijke P. Nature. 1997; 390: 465-471Crossref PubMed Scopus (3348) Google Scholar, 7Massagué J. Annu. Rev. Biochem. 1998; 67: 753-791Crossref PubMed Scopus (3987) Google Scholar). During embryonic development, the BMP pathway participates in the induction of ventral mesoderm, cardiac myogenesis, and vasculogenesis (8Hogan B.L.M. Genes Dev. 1996; 10: 1580-1594Crossref PubMed Scopus (1722) Google Scholar). Heterozygous mutations in the gene encoding BMPRII, the type II subunit of the BMP receptor, were identified in patients with both familial and sporadic idiopathic pulmonary arterial hypertension (IPAH) (9Machado R.D. Pauciulo M.W. Thomson J.R. Lane K.B. Morgan N.V. Wheeler L. Phillips 3rd, J.A. Newman J. Williams D. Galie N. Manes A. McNeil K. Yacoub M. Mikhail G. Rogers P. Corris P. Humbert M. Donnai D. Martensson G. Tranebjaerg L. Loyd J.E. Trembath R.C. Nichols W.C. Am. J. Hum. Genet. 2001; 68: 92-102Abstract Full Text Full Text PDF PubMed Scopus (464) Google Scholar, 10Thomson J.R. Machado R.D. Pauciulo M.W. Morgan N.V. Humbert M. Elliott G.C. Ward K. Yacoub M. Mikhail G. Rogers P. Newman J. Wheeler L. Higenbottam T. Gibbs J.S. Egan J. Crozier A. Peacock A. Allcock R. Corris P. Loyd J.E. Trembath R.C. Nichols W.C. J. Med. Genet. 2000; 37: 741-745Crossref PubMed Google Scholar). IPAH is characterized by elevated pulmonary vascular resistance and pulmonary arterial pressure with increased muscularization of small arteries, thickening or fibrosis of the intima, and presence of plexiform lesions and leads to right ventricular heart failure (11Rubin L.J. Rich S. Primary Pulmonary Hypertension. Marcel Dekker, Inc., New York1997: 19-55Google Scholar, 12Runo J.R. Loyd J.E. Lancet. 2003; 361: 1533-1544Abstract Full Text Full Text PDF PubMed Scopus (464) Google Scholar). Loss of expression of either the type I or type II subunits of the BMP receptor has been observed in sporadic and secondary forms of PAH (13Du L. Sullivan C.C. Chu D. Cho A.J. Kido M. Wolf P.L. Yuan J.X. Deutsch R. Jamieson S.W. Thistlethwaite P.A. N. Engl. J. Med. 2003; 348: 500-509Crossref PubMed Scopus (338) Google Scholar, 14Atkinson C. Stewart S. Upton P.D. Machado R. Thomson J.R. Trembath R.C. Morrell N.W. Circulation. 2002; 105: 1672-1678Crossref PubMed Scopus (513) Google Scholar, 15Zhang S. Fantozzi I. Tigno D.D. Yi E.S. Platoshyn O. Thistlethwaite P.A. Kriett J.M. Yung G. Rubin L.J. Yuan J.X. Am. J. Physiol. 2003; 285: L740-L754Crossref PubMed Scopus (212) Google Scholar). Transgenic mice expressing a catalytically inactive BMPRII mutant in SMC are predisposed to develop PAH in response to different stimuli (16Beppu H. Ichinose F. Kawai N. Jones R.C. Yu P.B. Zapol W.M. Miyazono K. Li E. Bloch K.D. Am. J. Physiol. 2004; 287: L1241-L1247Crossref PubMed Scopus (174) Google Scholar, 17Long L. MacLean M.R. Jeffery T.K. Morecroft I. Yang X. Rudarakanchana N. Southwood M. Trembath R.C. Morrell N.W. PubMed Scopus Google Scholar). that BMP signaling plays an essential role in normal homeostasis of vascular cells and in the of IPAH A. Biol. PubMed Scopus Google Scholar). is of BMP signaling pulmonary hypertension but not BMP is to modulate the phenotype of from the pulmonary and N. Davis and A. vSMC-specific contractile genes smooth muscle smooth muscle and a the or J.A. Wamhoff B.R. S. T. G.K. J. PubMed Scopus Google Scholar, J.M. J. Mol. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar). CArG the factor SRF, identified and for to serum to the of are known to modulate and for the CArG of the family, such as Myocd, and are of and have been to expression of vSMC marker genes J.A. Wamhoff B.R. S. T. G.K. J. PubMed Scopus Google Scholar, J.M. J. Mol. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar, J. J.M. J. Mol. 2002; Full Text PDF PubMed Google Scholar). that BMP signaling of and and the expression of vSMC-specific genes through the CArG G. Ku M.M. Nguyen P.H. Neuman N.A. Davis B.N. Hata A. J. Biol. Chem. 2007; 282: 37244-37255Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar). has been that the LIM domain and are also in the regulation of vSMC marker and as that and to activation of SMC genes in cardiac J. S. A. 2007; PubMed Scopus Google Scholar). forms a with SRF, to the CArG and gene as a of L.J. J.M. 2008; PubMed Scopus Google Scholar). FHL2 known as or is also a FHL2 with both and and plays a role in modulation of various such as and M. S. T. M. Cell Mol. PubMed Scopus Google Scholar). FHL2 is in cardiac cells and in the heart in C.C. M.M. 1998; PubMed Scopus Google but of expression were in the M. S. T. M. Cell Mol. PubMed Scopus Google Scholar, J.S. J.M. Am. J. Physiol. 2008; PubMed Scopus Google Scholar). has been that of the FHL2 gene is in an G. C. J.M. P. F. R. M. A. Mol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). FHL2 induction of and G. C. J.M. P. F. R. M. A. Mol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). In this we the role of FHL2 in vSMC phenotype that patients with PAH mutations of the domain of BMPRII an important role of the domain in the BMP signaling FHL2 by BMPRII domain as we show that FHL2 to the with BMP and the transcriptional activation of vSMC-specific contractile genes in PASMCs. We that FHL2 does not recruitment of SRF, or of to the CArG but inhibits recruitment of the chromatin remodeling SWI/SNF protein and RNA polymerase aortic from FHL2-null mice are to that the essential role of FHL2 in the regulation of vascular and contractile responses mediated by contractile such as BMP Cell were in with fetal bovine serum primary pulmonary artery smooth muscle cells were from and were in and used in this are: FHL2 or or or human and were from and and human FHL2 the and a were cells with as G. Ku M.M. Nguyen P.H. Neuman N.A. Davis B.N. Hata A. J. Biol. Chem. 2007; 282: 37244-37255Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar, G. Nguyen P.H. Hata A. Am. J. Physiol. PubMed Scopus Google Scholar). and or were and by of of to the cells RNA small interference RNA human FHL2 and from and mouse FHL2 is with a used as a were by G. Ku M.M. Nguyen P.H. Neuman N.A. Davis B.N. Hata A. J. Biol. Chem. 2007; 282: 37244-37255Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar, G. Nguyen P.H. Hata A. Am. J. Physiol. PubMed Scopus Google Scholar). were as G. Ku M.M. Nguyen P.H. Neuman N.A. Davis B.N. Hata A. J. Biol. Chem. 2007; 282: 37244-37255Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar). were by the through by for mouse FHL2 and human FHL2 human glyceraldehyde-3-phosphate human SMA, and were S. Fantozzi I. Tigno D.D. Yi E.S. Platoshyn O. Thistlethwaite P.A. Kriett J.M. Yung G. Rubin L.J. Yuan J.X. Am. J. Physiol. 2003; 285: L740-L754Crossref PubMed Scopus (212) Google Scholar, A. J. Lagna G. E. A. J. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). of with mutations in CArG and were from G. K. L. and J. J.E. I. G.K. 1998; PubMed Scopus Google Scholar, J.M. J.A. J. Biol. Chem. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar, L. P. Dev. Biol. 1997; PubMed Scopus Google Scholar, G.K. 84: PubMed Scopus Google Scholar). previously A. J. Lagna G. E. A. J. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). of the with cells were and with or for in were a with or cells were and in a or and to or and with observed by with secondary and secondary as K. Hata A. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). chromatin from a with and PubMed Scopus Google Scholar). with either II or or as a for the mouse gene and gene were previously G. Ku M.M. Nguyen P.H. Neuman N.A. Davis B.N. Hata A. J. Biol. Chem. 2007; 282: 37244-37255Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar, J. J. Biol. Chem. 2008; Full Text Full Text PDF PubMed Scopus Google Scholar). matrix as P. P. Phillips J.A. Mol. Biol. Google Scholar). with or control were in by for the from the the cells to the and the of E.S. J. 2008; PubMed Scopus Google Scholar). the of from the the and demonstrated as of the the of were with mouse aortic rings were and in as previously P. M. Med. 2003; PubMed Scopus Google Scholar, R. M. M. K. S. A. 2008; 105: PubMed Scopus Google Scholar). responses to were in vascular and mice in response to with in the of to to of rings were by a with of or and relaxation, rings were as WT, rings were of vSMCs from artery were from and were from which to phenotype by and for of vSMCs were and from a of from mice are of in with were group were by or of and were with the and the are with We to by a We used the of BMPRII domain or of domain in IPAH, which to the domain as and a mouse embryonic the from the with the domain encoding a FHL2 to with the domain suggesting a of FHL2 in of FHL2 and BMPRII in cells. expression encoding mouse FHL2 cells with expression encoding FHL2 and BMPRII by by FHL2 and BMPRII decreased we FHL2 with BMPRII the by the BMPRII receptor FHL2 in with BMPRII the mutant BMPRII to which is the not to FHL2 the that FHL2 with BMPRII the through with the We also the of FHL2 to with a mutant of BMPRII in IPAH, to with an in an FHL2 and that the of the and is not for FHL2 of FHL2 in human primary pulmonary artery smooth muscle cells and of FHL2 observed a however, FHL2 in the to G. C. J.M. P. F. R. M. A. Mol. 2004; Full Text Full Text PDF PubMed Scopus Google that BMP of FHL2, by of a of FHL2 to the We have previously that BMP signaling vSMC-specific genes in both mouse C3H10T½ (10T½) and cells through activation of the pathway and the pathway and a phenotype G. Ku M.M. Nguyen P.H. Neuman N.A. Davis B.N. Hata A. J. Biol. Chem. 2007; 282: 37244-37255Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar). Therefore, we the role of FHL2 the transcriptional activation of vSMC genes in cells. the of smooth muscle or smooth muscle which a CArG were with of FHL2 expression FHL2 the activation of vSMC in a mutant which is in critical of the CArG not by FHL2 Interestingly, FHL2 not affect the of the gene a known of the pathway A. J. Lagna G. E. A. J. 2000; Full Text Full Text PDF PubMed Scopus Google suggesting that the of FHL2 is to vSMC-specific genes an of FHL2 vSMC-specific gene of FHL2 by vSMC-specific gene expression in human primary vSMC, PASMCs. were with encoding FHL2 or that induction of vSMC and to in cells with control cells with the FHL2 the gene in protein expression by in the role of FHL2 in the activation of vSMC FHL2 by of in PASMCs. that FHL2 expression to in with cells with control of FHL2, both the and expression of vSMC genes elevated with cells increased of protein by by were in aortic not the of vSMC genes by of FHL2 by expression of a BMP receptor type suggesting that this is BMP signaling that FHL2 is a of transcriptional activation of vSMC role of FHL2 in the regulation of contractile response of vSMCs as a of in contractile gene expression by the P. P. Phillips J.A. Mol. Biol. Google Scholar, E.S. J. 2008; PubMed Scopus Google Scholar). has been previously that the of of can by of or in response to contractile such as in vSMCs E.S. J. 2008; PubMed Scopus Google Scholar). with or control were in and with for the of from the the and demonstrated as the of the the of In control cells, the of from to suggesting that of cells through increased expression of contractile of FHL2 by the of to in with control cells and decreased the to small but observed cells and cells in the presence of that FHL2 plays a role in the regulation of in the contractile response in mechanism of of FHL2 in the regulation of SMC gene expression that BMP signaling of the that vSMC gene through to CArG in with in cells G. Ku M.M. Nguyen P.H. Neuman N.A. Davis B.N. Hata A. J. Biol. Chem. 2007; 282: 37244-37255Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar). We FHL2 the of of however, observed in the presence or of FHL2 We the of FHL2 the transcriptional activation of a vSMC-specific gene by of the family. the CArG with a of or and of FHL2 expression in cells. with for a activation of observed of of the as previously G. Ku M.M. Nguyen P.H. Neuman N.A. Davis B.N. Hata A. J. Biol. Chem. 2007; 282: 37244-37255Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar, S. S. X. J.A. Mol. Cell Biol. PubMed Scopus Google Scholar, Li S. D. L. G. J.A. A. S. A. 2002; PubMed Scopus Google Scholar). the and the mediated by or were by FHL2 in a that FHL2 the of with the that FHL2 in the we that FHL2 inhibits the protein in the a of with the CArG or transcriptional activation. understand the mechanism of of recruitment of CArG box-binding proteins, we which are to the BMP has previously been demonstrated that Brg1, a component of the SWI/SNF chromatin remodeling complex, is to the and plays a critical role in transcriptional activation J. S. A. 2007; PubMed Scopus Google Scholar, M. H. J. J. Biol. Chem. 2007; 282: Full Text Full Text PDF PubMed Scopus Google Scholar). expression to the as as of were in right suggesting that is essential for the transcriptional activation of by We to a recruitment of Brg1, RNA polymerase II SRF, and to the previously SRF, which to the CArG BMP to the green G. Ku M.M. Nguyen P.H. Neuman N.A. Davis B.N. Hata A. J. Biol. Chem. 2007; 282: 37244-37255Abstract Full Text Full Text PDF PubMed Scopus (139) Google Scholar). and pol II, as as were to the as as BMP and the of and decreased pol II for to with FHL2 the recruitment of or to the CArG of the cells with or FHL2 were to FHL2 not the of or recruitment to the CArG Interestingly, increased expression of FHL2 elevated the of recruitment of to the This that FHL2 transcriptional activation of by component of the protein with the CArG such as recruitment of to the by in the presence of FHL2 and with Brg1, recruitment of pol II in the presence of FHL2 pol II and of recruitment by FHL2 is FHL2 not affect recruitment to connective tissue growth factor gene J. J. Biol. Chem. 2008; Full Text Full Text PDF PubMed Scopus Google that FHL2 inhibits transcriptional activation of SMC-specific genes by the recruitment of and pol in cells and in we vSMC cells from the of or demonstrated that expression of and elevated in cells, and observed with the both and were elevated in vSMCs with vSMCs Unlike of protein not by Finally, were to of recruitment of pol II in and the of expression in vSMCs of recruitment of pol II to the both the and the in with that recruitment of pol II to the SMC is by FHL2 in vSMCs of is in FHL2-null for endothelial-dependent to of aortic rings from mice of aortic rings in response to of aortic rings from mice for to of aortic rings from mice FHL2 has a physiological role in the regulation of vasomotor of vessels, we from FHL2 mice or mice and the responses of aortic rings to an endothelial-dependent that and SNP, a that vSMC mice are and development, in heart and is normal J.M. Li X. J.A. R. Williams Circulation. 2001; PubMed Scopus Google Scholar). arterial of rings were with suggesting that of FHL2 endothelial-dependent arterial however, the of in from mice Unlike the responses to both and rings to a vSMC that from FHL2-null mice are to both endothelial-dependent and -independent that FHL2 plays an essential role in the regulation of vasomotor tone. of vSMC phenotype is critical for maintenance of vascular In the of the of vSMCs to undergo phenotype plays an important role repair of and the development of is known the and signals this In this we that FHL2 is a critical of induction of the contractile phenotype in FHL2 identified as a protein in heart C.C. M.M. 1998; PubMed Scopus Google Scholar). FHL2 expression also demonstrated in the and in vSMCs from different M. S. T. M. Cell Mol. PubMed Scopus Google a that a role of FHL2 in the we show that FHL2 can induction of CArG vSMC through a mechanism of We that FHL2 does not or to the CArG in the This mechanism of of FHL2 is in with a that FHL2 inhibits recruitment of to the CArG by from G. C. J.M. P. F. R. M. A. Mol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). demonstrated that is to to a CArG in the presence of FHL2 by in G. C. J.M. P. F. R. M. A. Mol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). is that a mutant of which is in the used in the G. C. J.M. P. F. R. M. A. Mol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). Therefore, we that a of domain of lead to of to the CArG in which leads to a different in with in with a that FHL2 recruitment of both a protein and pol II to the of have that the recruitment and of pol II by in the S. S. D. T. F. A. D. C. J. J. Genes Dev. PubMed Scopus Google Scholar, A. F. L. R. J. A.J. J.L. M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, F. M. J. Med. PubMed Scopus Google Scholar). that is required for recruitment of of the such as pol II, to the of the vSMC genes by in the to the CArG is that FHL2 of factors the and inhibits of pol II, of pol II by of domain of pol II, or of the by of pol are to the mechanism of of pol II recruitment by FHL2. is also known that the recruitment of that such as and Therefore, it is that FHL2 required for activation of vSMC has been that is to vSMC gene the LIM only protein which LIM J. S. A. 2007; PubMed Scopus Google Scholar). with through an LIM domain J. S. A. 2007; PubMed Scopus Google which has with the LIM of FHL2, it is that FHL2 with for to and from to vSMC gene is known that the expression of vSMC-specific but not protein genes such as both of genes in the mechanism by which the of genes is it has been that recruitment of the protein is critical for activation of vSMC-specific but not genes M. H. J. J. Biol. Chem. 2007; 282: Full Text Full Text PDF PubMed Scopus Google Scholar). mechanism FHL2 inhibits recruitment to vSMC-specific recruitment of or SRF, a for the FHL2 the expression of vSMC genes but not In to in a in that FHL2 expression in that have the to the repair process S. J.M. L. C. J. T. H. A. H. J. R. R. J. Cell Biol. 2007; PubMed Scopus Google Scholar). embryonic from FHL2-null mice decreased and S. J.M. L. C. J. T. H. A. H. J. R. R. J. Cell Biol. 2007; PubMed Scopus Google Scholar). This is in with a that FHL2 and protein by from the pathway J.S. J.M. Am. J. Physiol. 2008; PubMed Scopus Google Scholar). We that is or in a mechanism in PASMCs. We also protein expression in and vSMCs cells by and not in in cells Therefore, we that the role of FHL2 in vSMC gene regulation is and FHL2 through with proteins, it is that FHL2 has different in various or expression of protein increased expression of of the proteins, in from human PAH patients and PAH mice G. M. S. R. J. K. A. F. O. L. N. Circulation. 2008; PubMed Scopus Google Scholar). and FHL2 and of the protein it is that FHL2 as as to the of PAH by to and or through modulation of regulation of contractile genes G. M. S. R. J. K. A. F. O. L. N. Circulation. 2008; PubMed Scopus Google Scholar). Finally, we demonstrated that aortic rings from FHL2-null mice resistance to suggesting that FHL2 is a of vasomotor tone. is to that a of vasomotor from elevated contractile gene expression in vSMCs in response to contractile such as BMP is to that FHL2-null mice in and blood A. Neuman and A. and that of or of expression mutations of in the contractile such as protein and the of protein signaling to vascular as as hypertension of R. M. M. K. S. A. 2008; 105: PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar). We a that hypertension in FHL2-null mice from however, it is to that in vasomotor play a role in of blood In that FHL2 is in vascular phenotype which is to the regulation of vascular We R. and R. S. Williams for the FHL2-null We M. F. and A. for in the mouse We also members of the Hata for critical and of the with