Beta-arrestin 2 functions as a G-protein-coupled receptor-activated regulator of oncoprotein Mdm2

Oncoprotein MDM2 is a master negative regulator of the tumor suppressor p53 and has been recently shown to regulate the ubiquitination of beta-arrestin 2, an important adapter and scaffold in signaling of G-protein-coupled receptors (GPCRs). However, whether beta-arrestin 2 has any effect on the function of MDM2 is still unclear. Our current results demonstrated that the binding of MDM2 to beta-arrestin 2 was significantly enhanced by stimulation of GPCRs. Activation of GPCRs led to formation of a ternary complex of MDM2, beta-arrestin 2, and GPCRs and thus recruited MDM2 to GPCRs at plasma membrane. Moreover, the binding of beta-arrestin 2 to MDM2 suppressed the self-ubiquitination of MDM2 and consequently reduced the Mdm2-mediated p53 degradation and ubiquitination. Further experiments revealed that overexpression of beta-arrestin 2 enhanced the p53-mediated Apoptosis while suppression of endogenous beta-arrestin 2 expression by RNA interference technology considerably attenuated the p53-mediated Apoptosis. Our study thus suggests that beta-arrestin 2 may serve as a cross-talk linker between GPCR and p53 signaling pathways.