Thrombin has been shown to inhibit skeletal muscle differentiation. However, the mechanisms by which thrombin represses myogenesis remain unknown. Since the thrombin receptor couples to Gi, Gq/11 and G12, we examined which subunits of heterotrimeric guanine nucleotide-binding regulatory proteins (Gαi, Gαq/11, Gα12 or Gβγ) participate in the thrombin-induced inhibition of C2C12 myoblast differentiation. Gαi2 and Gα11 had no inhibitory effect on the myogenic differentiation. Gα12 prevented only myoblast fusion, whereas Gβγ inhibited both the induction of skeletal muscle-specific markers and the myotube formation. In addition, the thrombin-induced reduction of creatine kinase activity was blocked by the C-terminal peptide of β-adrenergic receptor kinase, which is known to sequester free Gβγ. These results suggest that the thrombin-induced inhibition of muscle differentiation is mainly mediated by Gβγ.
