Encoding the β-Arrestin Trafficking Fate of Ghrelin Receptor GHSR1a: C-Tail-Independent Molecular Determinants in GPCRs

• DOI: 10.1021/acsptsci.9b00018
• Publication Date: 2019-06-03T20:26:44Z
• Authors: Krisztian Toth; Karim Nagi; Lauren M. Slosky; Lauren Rochelle; Caroline Ray; Suneet Kaur; Sudha K. Shenoy; Marc G. Caron; Larry S. Barak
• Keywords: Arrestin; Rhodopsin-like receptors; CCR1

G-protein-coupled receptors (GPCRs) can bias signaling through distinct biochemical pathways that originate from G-protein/receptor and β-arrestin/receptor complexes. Receptor conformations supporting β-arrestin engagement depend on multiple receptor determinants. Using ghrelin GHR1a, we demonstrate by bioluminescence resonance energy transfer fluorescence microscopy a critical role for its second intracellular loop 2 (ICL2) domain in stabilizing β-arrestin/GHSR1a core interactions determining trafficking fate. We validate our findings ICL2 gain- loss-of-function experiments assessing ubiquitin-dependent internalization of the CC chemokine receptor, CCR1. Like all CXC subfamily receptors, CCR1 lacks proline residue found consensus rhodopsin-family GPCRs. Our study indicates ICL2, C-tail determinants, orthosteric binding pocket regulates complex stability are sufficient to encode broad repertoire fates observed GPCRs, suggesting they provide essential elements regulating large fraction bias.