Targeted Elimination of G Proteins and Arrestins Defines Their Specific Contributions to Both Intensity and Duration of G Protein-coupled Receptor Signaling.
journal contributionposted on 18.09.2019, 14:02 by E Alvarez-Curto, A Inoue, L Jenkins, SZ Raihan, R Prihandoko, AB Tobin, G Milligan
G protein-coupled receptors (GPCRs) can initiate intracellular signaling cascades by coupling to an array of heterotrimeric G proteins and arrestin adaptor proteins. Understanding the contribution of each of these coupling options to GPCR signaling has been hampered by a paucity of tools to selectively perturb receptor function. Here we employ CRISPR/Cas9 genome editing to eliminate selected G proteins (Gαq and Gα11) or arrestin2 and arrestin3 from HEK293 cells together with the elimination of receptor phosphorylation sites to define the relative contribution of G proteins, arrestins, and receptor phosphorylation to the signaling outcomes of the free fatty acid receptor 4 (FFA4). A lack of FFA4-mediated elevation of intracellular Ca2+ in Gαq/Gα11-null cells and agonist-mediated receptor internalization in arrestin2/3-null cells confirmed previously reported canonical signaling features of this receptor, thereby validating the genome-edited HEK293 cells. FFA4-mediated ERK1/2 activation was totally dependent on Gq/11 but intriguingly was substantially enhanced for FFA4 receptors lacking sites of regulated phosphorylation. This was not due to a simple lack of desensitization of Gq/11 signaling because the Gq/11-dependent calcium response was desensitized by both receptor phosphorylation and arrestin-dependent mechanisms, whereas a substantially enhanced ERK1/2 response was only observed for receptors lacking phosphorylation sites and not in arrestin2/3-null cells. In conclusion, we validate CRISPR/Cas9 engineered HEK293 cells lacking Gq/11 or arrestin2/3 as systems for GPCR signaling research and employ these cells to reveal a previously unappreciated interplay of signaling pathways where receptor phosphorylation can impact on ERK1/2 signaling through a mechanism that is likely independent of arrestins.
This work was supported by Biotechnology and Biological Sciences Research Council Grants BB/K019864/1 (to G. M.) and BB/K019856/1 (to A. B. T.) and PRESTO, Japan Science and Technology Agency (to A. I.). The authors declare that they have no conflicts of interest with the contents of this article.
CitationJournal of Biological Chemistry, 2016, 291 (53), pp. 27147-27159
Author affiliation/Organisation/COLLEGE OF LIFE SCIENCES/Biological Sciences/Molecular & Cell Biology
VersionVoR (Version of Record)
Published inJournal of Biological Chemistry
PublisherAmerican Society for Biochemistry and Molecular Biology
CRISPR/CasG proteinG protein-coupled receptor (GPCR)arrestincalcium intracellular releaseextracellular-signal-regulated kinase (ERK)fatty acidArrestinsCRISPR-Cas SystemsCalciumGTP-Binding Protein alpha Subunits, Gq-G11HEK293 CellsHumansMitogen-Activated Protein Kinase 1Mitogen-Activated Protein Kinase 3PhosphorylationReceptors, G-Protein-CoupledSignal Transduction