Rock2 controls TGF beta signaling and inhibits mesoderm induction in zebrafish embryos

The Rho-associated serine/ threonine kinases Rock1 and Rock2 play important roles in cell contraction, adhesion, migration, proliferation and apoptosis. Here we report that Rock2 acts as a negative regulator of the TGF beta signaling pathway. Mechanistically, Rock2 binds to and accelerates the lysosomal degradation of TGF beta type I receptors internalized from the cell surface in mammalian cells. The inhibitory effect of Rock2 on TGF beta signaling requires its kinase activity. In zebrafish embryos, injection of rock2a mRNA attenuates the expression of mesodermal markers during late blastulation and blocks the induction of mesoderm by ectopic Nodal signals. By contrast, overexpression of a dominant negative form of zebrafish rock2a, dnrock2a, has an opposite effect on mesoderm induction, suggesting that Rock2 proteins are endogenous inhibitors for mesoderm induction. Thus, our data have unraveled previously unidentified functions of Rock2, in controlling TGF beta signaling as well as in regulating embryonic patterning.