G protein-coupled receptor kinase 2, with β-arrestin 2, impairs insulin-induced Akt/endothelial nitric oxide synthase signaling in ob/ob mouse aorta.
In type 2 diabetes, impaired insulin-induced Akt/endothelial nitric oxide synthase (eNOS) signaling may decrease the vascular relaxation response. Previously, we reported that this response was negatively regulated by G protein-coupled receptor kinase 2 (GRK2). In this study, we investigated whether/how in aortas from ob/ob mice (a model of type 2 diabetes) GRK2 and β-arrestin 2 might regulate insulin-induced signaling. Endothelium-dependent relaxation was measured in aortic strips. GRK2, β-arrestin 2, and Akt/eNOS signaling pathway proteins and activities were mainly assayed by Western blotting. In ob/ob (vs. control [Lean]) aortas: 1) insulin-induced relaxation was reduced, and this deficit was prevented by GRK2 inhibitor, anti-GRK2 antibody, and an siRNA specifically targeting GRK2. The Lean aorta relaxation response was reduced to the ob/ob level by pretreatment with an siRNA targeting β-arrestin 2. 2) Insulin-stimulated Akt and eNOS phosphorylations were decreased. 3) GRK2 expression in membranes was elevated, and, upon insulin stimulation, this expression was further increased, but β-arrestin 2 was decreased. In ob/ob aortic membranes under insulin stimulation, the phosphorylations of Akt and eNOS were augmented by GRK2 inhibitor. In mouse aorta, GRK2 may be, upon translocation, a key negative regulator of insulin responsiveness and an important regulator of the β-arrestin 2/Akt/eNOS signaling, which is implicated in diabetic endothelial dysfunction.
Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University, Shinagawa-ku, Tokyo, Japan.
Kumiko
K
Taguchi
Takayuki
T
Matsumoto
Katsuo
K
Kamata
Tsuneo
T
Kobayashi
D000818:Animals; D001011:Aorta / Q000378:metabolism; D019390:Arrestins / Q000235:genetics; D054769:G-Protein-Coupled Receptor Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology; D008297:Male; D051379:Mice; D008820:Mice, Obese; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
C000605258:Arrb2 protein, mouse; D019390:Arrestins; D007328:Insulin; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; D052250:Nitric Oxide Synthase Type III; D051057:Proto-Oncogene Proteins c-akt; C496568:GRK2 protein, mouse; D054769:G-Protein-Coupled Receptor Kinase 2