Role of G protein ‐coupled receptor kinases (GRKs) in β2‐adrenoceptor‐mediated glucose uptake

AbstractTruncation of the C-terminal tail of the β2-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 β2-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 β2-ARs were generated and receptor affinity for [3H]-CGP12177A and density of binding sites determined together with the affinity of isoprenaline and BRL37344. Following receptor activation by β2-AR agonists, cAMP accumulation, GLUT4 translocation, [3H]-2-deoxyglucose uptake, and β2-AR internalization were measured. Bioluminescence resonance energy transfer was used to investigate interactions between β2-AR and β-arrestin2 or between β2-AR and GRK2. Glucose uptake after siRNA knockdown or GRK inhibitors was measured in response to β2-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 β2-AR agonists occurred in CHO-GLUT4myc cells expressing β2-ARs lacking GRK or GRK/PKA phosphorylation sites as well as in cells expressing the wild-type β2-AR. However, β2-ARs lacking phosphorylation sites failed to recruit β-arrestin2 and did not internalize. GRK2 knock-down or GRK2 inhibitors decreased isopren...
Source: Pharmacology Research and Perspectives - Category: Drugs & Pharmacology Authors: Tags: ORIGINAL ARTICLE Source Type: research