Differential regulation of endosomal GPCR/β-arrestin complexes and trafficking by MAPK

Abstract

β-Arrestins are signaling adaptors that bind to agonist-occupied G protein-coupled receptors (GPCRs) and target them for endocytosis; however, the mechanisms regulating receptor/β-arrestin complexes and trafficking in endosomes, remain ill defined. Here we show, in live cells, differential dynamic regulation of endosomal bradykinin B2 receptor (B2R) complexes with eitherβ-arrestin-1 or -2. We find a novel role for MAPK in the B2R/β-arrestin-2 complex formation, receptor trafficking and signaling mediated by an ERK1/2 regulatory motif in the hinge domain of the ratβ-arrestin-2 (PET178P), but not ratβ-arrestin- 1 (PER177P). While the ERK1/2 regulatory motif is conserved between rat and mouse β-arrestin-2, it is surprisingly not conservedinhumanβ-arrestin-2(PEK178P). However, mutation of lysine 178 to threonine is sufficient to confer MAPK sensitivity to the humanβ-arrestin-2. Furthermore, substitution for a phosphomimetic residue in both the rat and the human β-arrestin-2 (T/K178D) significantly stabilizes B2R/β-arrestin complexes in endosomes, delays receptor recycling to the plasma membrane and maintains intracellular MAPK signaling. Similarly, the endosomal trafficking ofβ2-adrenergic, angiotensin II type 1 and vasopressin V2 receptors was altered by the β-arrestin-2 T178D mutant. Our findings unveil a novel subtype specificmodeof MAPK-dependent regulation of β-arrestins in intracellular trafficking and signaling of GPCRs, and suggest differential endosomal receptor/β-arrestin- 2 signaling roles among species.