Transforming growth factor-beta induction of smooth muscle cell phenotpye requires transcriptional and post-transcriptional control of serum response factor.
Transforming growth factor-beta induces a smooth muscle cell phenotype in undifferentiated mesenchymal cells. To elucidate the mechanism(s) of this phenotypic induction, we focused on the molecular regulation of smooth muscle-gamma-actin, whose expression is induced at late stages of smooth muscle differentiation and developmentally restricted to this lineage. Transforming growth factor-beta induced smooth muscle-gamma-actin protein, cytoskeletal localization, and mRNA expression in mesenchymal cells. Smooth muscle-gamma-actin promoter-luciferase reporter activity was enhanced by transforming growth factor-beta, and deletion analysis revealed that CArG box 2 in the promoter was necessary for this transcriptional activation. CArG motifs bind transcriptional activator serum response factor; gel shift analyses revealed increased binding of serum response factor-containing complexes to this site in response to transforming growth factor-beta, paralleled by increased serum response factor protein expression. Serum response factor expression was found to be up-regulated by transforming growth factor-beta via transcriptional activation of the gene and post-transcriptional regulation. Using mesenchymal cells stably transfected with wild type or dominant-negative serum response factor, we demonstrated that its expression is sufficient for induction of a smooth muscle phenotype in mesenchymal cells and is necessary for transforming growth factor-beta-mediated smooth muscle induction.
Hirschi
Karen K
KK
Department of Pediatrics, Center for Cell and Gene Therapy and Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas 77030, USA. khirsch@bcm.tmc.edu
Lai
Lihua
L
Belaguli
Narasimhaswamy S
NS
Dean
David A
DA
Schwartz
Robert J
RJ
Zimmer
Warren E
WE
D000199:Actins / Q000235:genetics; D000818:Animals; D002460:Cell Line; D003599:Cytoskeleton / Q000378:metabolism; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D009130:Muscle, Smooth / Q000166:cytology* / Q000187:drug effects / Q000502:physiology; D010641:Phenotype; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000235:genetics; D026362:Serum Response Factor / Q000235:genetics*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D000199:Actins; D012333:RNA, Messenger; D026362:Serum Response Factor; D016212:Transforming Growth Factor beta