RhoA signaling via serum response factor plays an obligatory role in myogenic differentiation.
Serum response factor (SRF) plays a central role during myogenesis, being required for the expression of striated alpha-actin genes. As shown here, the small GTPase RhoA-dependent activation of SRF results in the expression of muscle-specific genes, thereby promoting myogenic differentiation in myoblast cell lines. Co-expression of activated V14-RhoA and SRF results in an approximately 10-fold activation of the skeletal alpha-actin promoter in replicating myoblasts, while SRFpm1, a dominant negative SRF mutant, blocks RhoA dependent skeletal alpha-actin promoter activity. Serum withdrawal further potentiates RhoA- and SRF-mediated activation of alpha-actin promoter to about 30-fold in differentiated myotubes. In addition, the proximal SRE1 in the skeletal alpha-actin promoter is sufficient to mediate RhoA signaling via SRF. Furthermore, SRFpm1 and to a lesser extent dominant negative N19-RhoA inhibit myoblast fusion, postreplicative myogenic differentiation, and expression of direct SRF targets such as skeletal alpha-actin and indirect targets such as myogenin and alpha-myosin heavy chain. Moreover, RhoA also stimulates the autoregulatable murine SRF gene promoter in myoblasts, and the expression level of SRF is reduced in myoblasts overexpressing N19-RhoA. Our study supports the concept that RhoA signaling via SRF serves as an obligatory muscle differentiation regulatory pathway.
Wei
L
L
Department of Cell Biology, Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.
Zhou
W
W
Croissant
J D
JD
Johansen
F E
FE
Prywes
R
R
Balasubramanyam
A
A
Schwartz
R J
RJ
D000199:Actins / Q000235:genetics; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000502:physiology*; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology*; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D011401:Promoter Regions, Genetic; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics; D026362:Serum Response Factor; D015398:Signal Transduction; D015533:Transcriptional Activation; D020742:rhoA GTP-Binding Protein
D000199:Actins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D016760:Proto-Oncogene Proteins c-fos; D026362:Serum Response Factor; D019204:GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein