Nedd4 Mediates Agonist-dependent Ubiquitination, Lysosomal Targeting, and Degradation of the β₂-Adrenergic Receptor
Shenoy, Sudha K. | Xiao, Kunhong | Venkataramanan, Vidya | Snyder, Peter M. | Freedman, Neil J. | Weissman, Allan M.
Agonist-stimulated β₂-adrenergic receptor (β₂AR) ubiquitination is a major factor that governs both lysosomal trafficking and degradation of internalized receptors, but the identity of the E3 ubiquitin ligase regulating this process was unknown. Among the various catalytically inactive E3 ubiquitin ligase mutants that we tested, a dominant negative Nedd4 specifically inhibited isoproterenol-induced ubiquitination and degradation of the β₂AR in HEK-293 cells. Moreover, siRNA that down-regulates Nedd4 expression inhibited β₂AR ubiquitination and lysosomal degradation, whereas siRNA targeting the closely related E3 ligases Nedd4-2 or AIP4 did not. Interestingly, β₂AR as well as β-arrestin2, the endocytic and signaling adaptor for the β₂AR, interact robustly with Nedd4 upon agonist stimulation. However, β₂AR-Nedd4 interaction is ablated when β-arrestin2 expression is knocked down by siRNA transfection, implicating an essential E3 ubiquitin ligase adaptor role for β-arrestin2 in mediating β₂AR ubiquitination. Notably, β-arrestin2 interacts with two different E3 ubiquitin ligases, namely, Mdm2 and Nedd4 to regulate distinct steps in β₂AR trafficking. Collectively, our findings indicate that the degradative fate of the β₂AR in the lysosomal compartments is dependent upon β-arrestin2-mediated recruitment of Nedd4 to the activated receptor and Nedd4-catalyzed ubiquitination.Show more [+] Less [-]