Role of G protein-coupled receptor kinases (GRKs) in β 2 -adrenoceptor-mediated glucose uptake

• Published in: Pharmacology research & perspectives 2024-02, Vol.12 (1), p.e1176
• Main Authors: Ham, Seungmin, Mukaida, Saori, Sato, Masaaki, Keov, Peter, Bengtsson, Tore, Furness, Sebastian, Holliday, Nicholas D, Evans, Bronwyn A, Summers, Roger J, Hutchinson, Dana S
• Format: Article
• Language: English
• Subjects: Animals; beta adrenoceptor; G-Protein-Coupled Receptor Kinases; Glucose - metabolism; glucose uptake; GRK2; Isoproterenol - pharmacology; Rats; Receptors, Adrenergic; Receptors, G-Protein-Coupled
• ISSN: 2052-1707; 2052-1707
• DOI: 10.1002/prp2.1176

Truncation of the C-terminal tail of the β -AR, transfection of βARKct or over-expression of a kinase-dead GRK mutant reduces isoprenaline-stimulated glucose uptake, indicating that GRK is important for this response. We explored whether phosphorylation of the β -AR by GRK2 has a role in glucose uptake or if this response is related to the role of GRK2 as a scaffolding protein. CHO-GLUT4myc cells expressing wild-type and mutant β -ARs were generated and receptor affinity for [ H]-CGP12177A and density of binding sites determined together with the affinity of isoprenaline and BRL37344. Following receptor activation by β -AR agonists, cAMP accumulation, GLUT4 translocation, [ H]-2-deoxyglucose uptake, and β -AR internalization were measured. Bioluminescence resonance energy transfer was used to investigate interactions between β -AR and β-arrestin2 or between β -AR and GRK2. Glucose uptake after siRNA knockdown or GRK inhibitors was measured in response to β -AR agonists. BRL37344 was a poor partial agonist for cAMP generation but displayed similar potency and efficacy to isoprenaline for glucose uptake and GLUT4 translocation. These responses to β -AR agonists occurred in CHO-GLUT4myc cells expressing β -ARs lacking GRK or GRK/PKA phosphorylation sites as well as in cells expressing the wild-type β -AR. However, β -ARs lacking phosphorylation sites failed to recruit β-arrestin2 and did not internalize. GRK2 knock-down or GRK2 inhibitors decreased isoprenaline-stimulated glucose uptake in rat L6 skeletal muscle cells. Thus, GRK phosphorylation of the β -AR is not associated with isoprenaline- or BRL37344-stimulated glucose uptake. However, GRKs acting as scaffold proteins are important for glucose uptake as GRK2 knock-down or GRK2 inhibition reduces isoprenaline-stimulated glucose uptake.