Involvement of Ras and Ral in Chemotactic Migration of Skeletal Myoblasts

Abstract

In skeletal myoblasts, Ras has been considered to be a strong inhibitor of myogenesis. Here, we demonstrate that Ras is involved also in the chemotactic response of skeletal myoblasts. Expression of a dominant-negative mutant of Ras inhibited chemotaxis of C2C12 myoblasts in response to basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), and insulin-like growth factor 1 (IGF-1), key regulators of limb muscle development and skeletal muscle regeneration. A dominant-negative Ral also decreased chemotactic migration by these growth factors, while inhibitors for phosphatidylinositol 3-kinase and mitogen-activated protein kinase kinase (MEK) showed no effect. Activation of the Ras-Ral pathway by expression of an activated mutant of either Ras, the guanine-nucleotide dissociation stimulator for Ral, or Ral resulted in increased motility of myoblasts. The ability of Ral to stimulate motility was reduced by introduction of a mutation which prevents binding to Ral-binding protein 1 or phospholipase D. These results suggest that the Ras-Ral pathway is essential for the migration of myoblasts. Furthermore, we found that Ras and Ral are activated in C2C12 cells by bFGF, HGF and IGF-1 and that the Ral activation is regulated by the Ras- and the intracellular Ca²⁺-mediated pathways. Taken together, our data indicate that Ras and Ral regulate the chemotactic migration of skeletal muscle progenitors.

View correction statement:

Involvement of Ras and Ral in Chemotactic Migration of Skeletal Myoblasts

ACKNOWLEDGMENTS

We are grateful to Kenji Tago for the construction of pGEX-RasBD and to Martin McMahon and Akira Kikuchi for kindly providing the plasmids. We also thank Shin Mizutani, Kaoru Inouye, Koji Terada, Junji Yamauchi, Motoshi Nagao, and all the other members of our laboratory for helpful discussion.

This work was supported by grants 10680666 and 11160204 (to H.K.) from the Ministry of Education, Science, Sports and Culture of Japan and by Core Research for Evolutional Science and Technology (CREST) of the Japan Science and Technology Corporation (JST). Our laboratory at Tokyo Institute of Technology is supported by funds donated by Schering-Plough Corporation.