Rhoa Gtpase Phosphorylated At Tyrosine 42 By Src Kinase Binds To Beta-Catenin And Contributes Transcriptional Regulation Of Vimentin Upon Wnt3a

In the Wnt canonical pathway, Wnt3A has been known to stabilize beta-catenin. In the non-canonical Wnt signaling pathway, Wnt is known to activate Rho GTPases. The correlation between canonical and non-canonical pathways by Wnt signaling, however, has not been well elucidated. Here, we identified that Wnt3A promoted superoxide generation, leading to Tyr42 phosphorylation of RhoA through activations of c-Src and Rho-dependent coiled coil kinase 2 (ROCK2) and phosphorylation of p47phox, a component of NADPH oxidase. Wnt3A also induced accumulation of beta-catenin along with activations of RhoA and ROCK1. Concurrently, ROCK1 was able to phosphorylate GSK-3 beta at Ser9, which phosphorylated Src at Ser51 and Ser492 residues, leading to Src inactivation through dephosphorylation of Tyr416 during the late period of Wnt3A treatment. Meanwhile, p-Tyr42 RhoA bound to beta-catenin via the N-terminal domain of beta-catenin, thereby leading to the nuclear translocation of p-Tyr42 RhoA/beta-catenin complex. Notably, p-Tyr42 RhoA as well as beta-catenin was associated with the promoter of Vim, leading to increased expression of vimentin. In addition, stomach cancer patients harboring higher expressed p-Tyr42 Rho levels revealed the much poorer survival probability. Therefore, we propose that p-Tyr42 RhoA is crucial for transcriptional regulation of specific target genes in the nucleus by binding to their promoters and involved in tumorigenesis.