Basic fibroblast growth factor antagonizes transforming growth factor-beta1-induced smooth muscle gene expression through extracellular signal-regulated kinase 1/2 signaling pathway activation.
OBJECTIVE
Transforming growth factor-beta1 (TGFbeta1) and fibroblast growth factor (FGF) families play a pivotal role during vascular development and in the pathogenesis of vascular disease. However, the interaction of intracellular signaling evoked by each of these growth factors is not well understood. The present study was undertaken to examine the molecular mechanisms that mediate the effects of TGFbeta1 and basic FGF (bFGF) on smooth muscle cell (SMC) gene expression.


RESULTS
TGFbeta1 induction of SMC gene expression, including smooth muscle protein 22-alpha (SM22alpha) and smooth muscle alpha-actin, was examined in the pluripotent 10T1/2 cells. Marked increase in these mRNA levels by TGFbeta1 was inhibited by c-Src-tyrosine kinase inhibitors and protein synthesis inhibitor cycloheximide. Functional studies with deletion and site-directed mutation analysis of the SM22alpha promoter demonstrated that TGFbeta1 activated the SM22alpha promoter through a CC(A/T-rich)6GG (CArG) box, which serves as a serum response factor (SRF)-binding site. TGFbeta1 increased SRF expression through an increase in transcription of the SRF gene. In the presence of bFGF, TGFbeta1 induction of SMC marker gene expression was significantly attenuated. Transient transfection assays showed that bFGF significantly suppressed induction of the SM22alpha promoter-driven luciferase activity by TGFbeta1, whereas bFGF had no effects on the TGFbeta1-mediated increase in SRF expression and SRF:DNA binding activity. Mitogen-activated protein kinase kinase-1 (MEK1) inhibitor PD98059 abrogated the bFGF-mediated suppression of TGFbeta1-induced SMC gene expression.


CONCLUSIONS
Our data suggest that bFGF-induced MEK/extracellular signal-regulated kinase signaling plays an antagonistic role in TGFbeta1-induced SMC gene expression through suppression of the SRF function. These data indicate that opposing effects of bFGF and TGFbeta1 on SMC gene expression control the phenotypic plasticity of SMCs.
Kawai-Kowase
Keiko
K
Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, 3-Maebashi, Gunma, Japan.
Sato
Hiroko
H
Oyama
Yuko
Y
Kanai
Hiroyoshi
H
Sato
Mahito
M
Doi
Hiroshi
H
Kurabayashi
Masahiko
M
D000199:Actins / Q000096:biosynthesis / Q000235:genetics; D000818:Animals; D001011:Aorta; D002135:Calcium-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004247:DNA / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000502:physiology; D051379:Mice; D008809:Mice, Inbred C3H; D008840:Microfilament Proteins / Q000096:biosynthesis / Q000235:genetics; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000502:physiology*; D009124:Muscle Proteins / Q000096:biosynthesis / Q000235:genetics; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D016297:Mutagenesis, Site-Directed; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011485:Protein Binding; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology; D027602:Serum Response Element / Q000187:drug effects; D026362:Serum Response Factor / Q000378:metabolism / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D014158:Transcription, Genetic / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D053773:Transforming Growth Factor beta1; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D000096985:Calponins
D000199:Actins; D002135:Calcium-Binding Proteins; D003513:Cycloheximide; D004247:DNA; D016222:Fibroblast Growth Factor 2; D048369:MAP Kinase Kinase 1; D008840:Microfilament Proteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D009124:Muscle Proteins; D047428:Protein Kinase Inhibitors; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D011994:Recombinant Proteins; D026362:Serum Response Factor; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D019061:src-Family Kinases; D000096985:Calponins; C508961:Tgfb1 protein, mouse; C508962:Tgfb1 protein, rat; C051615:transgelin; C482127:Map2k1 protein, mouse