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 β2-Adernergic Receptor (β2AR). Using phosphomimetic variants, we identified pre-formed secondary structure elements, or short linear motif (SLiMs), that undergo specific conformational transitions upon phosphorylation. Of importance, such conformational transition favors arrestin-2 binding. Hence, our results suggest a model in which the cellular signaling specificity of GPCRs is encoded in the phosphorylation-dependent structuration of the C-terminal regions, which will subsequently modulate arrestin conformation and therefore GPCR:arrestin signaling outcomes.