Phosphorylation motif dictates GPCR C-terminal domain conformation and arrestin interaction

Arrestin-dependent G protein-coupled receptor (GPCR) signaling pathway is regulated by the phosphorylation state of GPCR's C-terminal domain, but the molecular bases of arrestin:receptor interaction are to be further illuminated. Here we investigated the impact of phosphorylation on the conformational features of the C-terminal region from three rhodopsin-like GPCRs, the vasopressin V2 receptor (V2R), the growth hormone secretagogue or ghrelin receptor type 1a (GHSR), and the beta 2-adernergic receptor (beta 2AR). Using phosphomimetic variants, we identified pre-formed secondary structure elements, or short linear motifs (SLiMs), that undergo specific conformational transitions upon phosphorylation. Of importance, such conformational transitions appear to favor arrestin-2 binding. Hence, our results suggest a model in which the phosphorylation-dependent structuration of the GPCR C-terminal regions would modulate arrestin binding and therefore signaling outcomes in arrestin-dependent pathways.