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Insulin induces IRS2-dependent and GRK2-mediated β2AR internalization to attenuate βAR signaling in cardiomyocytes
Qin Fu1, Bing Xu2, Dippal Parikh2
1Department of Pharmacology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China; Department of Pharmacology, University of California at Davis, CA 95616, United States.
Abstract:
The counter-regulatory effects of insulin and catecholamines on carbohydrate and lipid metabolism are well studied, whereas the details of insulin regulation of β adrenergic receptor (βAR) signaling pathway in heart remain unknown. Here, we characterize a novel signaling pathway of insulin receptor (IR) to G protein-coupled receptor kinase 2 (GRK2) in the heart. Insulin stimulates recruitment of GRK2 to β2AR, which induces β2AR phosphorylation at the GRK sites of serine 355/356 and subsequently β2AR internalization. Insulin thereby suppresses βAR-induced cAMP-PKA activities and contractile response in neonatal and adult mouse cardiomyocytes. Deletion of insulin receptor substrate 2 (IRS2) disrupts the complex of IR and GRK2, which attenuates insulin-mediated β2AR phosphorylation at the GRK sites and β2AR internalization, and the counter-regulation effects of insulin on βAR signaling. These data indicate the requirements of IRS2 and GRK2 for insulin to stimulate counter-regulation of βAR via β2AR phosphorylation and internalization in cardiomyocytes.
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