G Protein and β-arrestin signaling bias at the ghrelin receptor.

Abstract

The G protein-coupled ghrelin receptor GHSR1a is a potential pharmacological target for treating obesity and addiction because of the critical role ghrelin plays in energy homeostasis and dopamine-dependent reward. GHSR1a enhances growth hormone release, appetite, and dopamine signaling through G(q/11), G(i/o), and G(12/13) as well as β-arrestin-based scaffolds. However, the contribution of individual G protein and β-arrestin pathways to the diverse physiological responses mediated by ghrelin remains unknown. To characterize whether a signaling bias occurs for GHSR1a, we investigated ghrelin signaling in a number of cell-based assays, including Ca(2+) mobilization, serum response factor response element, stress fiber formation, ERK1/2 phosphorylation, and β-arrestin translocation, utilizing intracellular second loop and C-tail mutants of GHSR1a. We observed that GHSR1a and β-arrestin rapidly form metastable plasma membrane complexes following exposure to an agonist, but replacement of the GHSR1a C-tail by the tail of the vasopressin 2 receptor greatly stabilizes them, producing complexes observable on the plasma membrane and also in endocytic vesicles. Mutations of the contiguous conserved amino acids Pro-148 and Leu-149 in the GHSR1a intracellular second loop generate receptors with a strong bias to G protein and β-arrestin, respectively, supporting a role for conformation-dependent signaling bias in the wild-type receptor. Our results demonstrate more balance in GHSR1a-mediated ERK signaling from G proteins and β-arrestin but uncover an important role for β-arrestin in RhoA activation and stress fiber formation. These findings suggest an avenue for modulating drug abuse-associated changes in synaptic plasticity via GHSR1a and indicate the development of GHSR1a-biased ligands as a promising strategy for selectively targeting downstream signaling events.

• Authors: Tama Evron, Sean M Peterson, Nikhil M Urs, Yushi Bai, Lauren K Rochelle, Marc G Caron, Larry S Barak
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 289 Issue 48 Pg. 33442-55 (Nov 28 2014) ISSN: 1083-351X [Electronic] United States
• PMID: 25261469 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)
• Copyright: © 2014 by The American Society for Biochemistry and Molecular Biology, Inc.

Chemical References

• AVPR2 protein, human
• Arrestin
• Receptors, Ghrelin
• Receptors, Vasopressin
• MAPK1 protein, human
• Mitogen-Activated Protein Kinase 1
• Mitogen-Activated Protein Kinase 3
• GTP-Binding Proteins

Topics

• Arrestin (genetics, metabolism)
• GTP-Binding Proteins (genetics, metabolism)
• HEK293 Cells
• Humans
• MAP Kinase Signaling System (physiology)
• Mitogen-Activated Protein Kinase 1 (genetics, metabolism)
• Mitogen-Activated Protein Kinase 3 (genetics, metabolism)
• Neuronal Plasticity (physiology)
• Protein Stability
• Protein Structure, Secondary
• Protein Transport (physiology)
• Receptors, Ghrelin (genetics, metabolism)
• Receptors, Vasopressin (genetics, metabolism)