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Positive regulation of skeletal myogenesis by R-Ras
1Faculty of Bioscience, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama, Japan.
Abstract:
Most of the proteins in the Ras-family proteins, including Ras, Rap and TC21, have been reported to be strong inhibitors of skeletal myogenesis. Here we show that R-Ras, another member of this family, promotes terminal differentiation of C2C12 skeletal myoblasts. In contrast to Ras, which induced a markedly transformed phenotype of C2C12 cells, an activated mutant of R-Ras (R-RasQ87L) did not exhibit any inhibitory effect on the differentiation of C2C12 cells, but enhanced the formation of multinucleated myotubes. Although R-RasQ87L showed little effect on induction of two muscle-specific proteins, creatine kinase and myogenin, it prevented cell death during myoblast differentiation, probably through Akt activation and Bcl-xL induction. Motility of C2C12 cells, which may be involved in fusion of myoblasts, was also stimulated by R-RasQ87L. Furthermore, we observed a transient activation of endogenous R-Ras during differentiation of C2C12 cells. The ectopic expression of R-Ras GAP inhibited the differentiation. These results suggest that R-Ras has a positive effect on the terminal differentiation of myoblasts and may be involved in the program of skeletal myogenesis.
Insights
Ras homologated Ras (R-Ras) promotes skeletal myogenesis, unlike other Ras-family proteins. R-Ras enhances myoblast differentiation and survival, suggesting a positive role in muscle development.
Area of Science:
- Cell Biology
- Molecular Biology
- Muscle Development
Background:
- Ras-family proteins typically inhibit skeletal myogenesis.
- The specific role of R-Ras in muscle differentiation was previously unclear.
Purpose of the Study:
- To investigate the function of R-Ras in skeletal myoblast differentiation.
- To determine if R-Ras plays a positive or negative role in myogenesis.
Main Methods:
- Utilized C2C12 skeletal myoblast cell line.
- Expressed activated R-Ras mutant (R-RasQ87L) and R-Ras GTPase-activating protein (GAP).
- Assessed myotube formation, cell death, and expression of muscle-specific proteins.
Main Results:
- Activated R-Ras enhanced multinucleated myotube formation.
- R-Ras prevented cell death during differentiation, likely via Akt and Bcl-xL.
- R-Ras stimulated myoblast motility, potentially aiding fusion.
- Endogenous R-Ras activation was observed during differentiation.
- R-Ras GAP inhibited differentiation.
Conclusions:
- R-Ras positively regulates terminal differentiation of skeletal myoblasts.
- R-Ras is involved in the skeletal myogenesis program.
- R-Ras promotes myoblast survival and motility during differentiation.