A Novel Muscle-Specific β1 Integrin Binding Protein (Mibp) That Modulates Myogenic Differentiation

Myogenesis is regulated by cell adhesion receptors, including integrins of the beta1 family. We report the identification of a novel muscle-specific beta1 integrin binding protein (MIBP). MIBP binds to the membrane-proximal cytoplasmic region shared by beta1A and beta1D integrins, and the binding occurs in vivo as well as in vitro. Furthermore, we show that MIBP is abundantly expressed by C2C12 myogenic cells before fusion, and the expression of MIBP is dramatically downregulated during subsequent differentiation. Finally, we show that overexpression of MIBP in C2C12 cells resulted in a suppression of fusion and terminal differentiation, suggesting that MIBP may play a key role in controlling the progression of muscle differentiation.