GPCR-G Protein-β-Arrestin Super-Complex Mediates Sustained G Protein Signaling

• Published in: Cell 2016-08, Vol.166 (4), p.907-919
• Main Authors: Thomsen, Alex R.B., Plouffe, Bianca, Cahill, Thomas J., Shukla, Arun K., Tarrasch, Jeffrey T., Dosey, Annie M., Kahsai, Alem W., Strachan, Ryan T., Pani, Biswaranjan, Mahoney, Jacob P., Huang, Liyin, Breton, Billy, Heydenreich, Franziska M., Sunahara, Roger K., Skiniotis, Georgios, Bouvier, Michel, Lefkowitz, Robert J.
• Format: Article
• Language: English
• Subjects: beta-Arrestins - chemistry; beta-Arrestins - metabolism; Bioluminescence Resonance Energy Transfer Techniques; Cyclic AMP - metabolism; electron microscopy; endosomes; Endosomes - metabolism; G-protein coupled receptors; GTP-Binding Protein alpha Subunits, Gs - metabolism; HEK293 Cells; Humans; Microscopy, Confocal; Microscopy, Electron; Multiprotein Complexes; phosphorylation; plasma membrane; Receptors, G-Protein-Coupled - agonists; Receptors, G-Protein-Coupled - antagonists & inhibitors; Receptors, G-Protein-Coupled - chemistry; Receptors, G-Protein-Coupled - metabolism; serine; Signal Transduction; threonine
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/j.cell.2016.07.004

Classically, G protein-coupled receptor (GPCR) stimulation promotes G protein signaling at the plasma membrane, followed by rapid β-arrestin-mediated desensitization and receptor internalization into endosomes. However, it has been demonstrated that some GPCRs activate G proteins from within internalized cellular compartments, resulting in sustained signaling. We have used a variety of biochemical, biophysical, and cell-based methods to demonstrate the existence, functionality, and architecture of internalized receptor complexes composed of a single GPCR, β-arrestin, and G protein. These super-complexes or “megaplexes” more readily form at receptors that interact strongly with β-arrestins via a C-terminal tail containing clusters of serine/threonine phosphorylation sites. Single-particle electron microscopy analysis of negative-stained purified megaplexes reveals that a single receptor simultaneously binds through its core region with G protein and through its phosphorylated C-terminal tail with β-arrestin. The formation of such megaplexes provides a potential physical basis for the newly appreciated sustained G protein signaling from internalized GPCRs. [Display omitted] •Some GPCRs simultaneously interact with both G protein and β-arrestin (βarr)•In these “megaplexes,” G protein binds to the receptor transmembrane core•Concurrent with G protein coupling, βarr binds to the receptor C-terminal tail•G protein activation within megaplexes occurs from internalized compartments Megaplexes containing a GPCR simultaneously engaged with a G protein and β-arrestin sustain G protein signaling following internalization into endosomes.