Cohn Heather Irina, Harris David M, Pesant Stephanie, Pfeiffer Michael, Zhou Rui-Hai, Koch Walter J, Dorn Gerald W, Eckhart Andrea D
Center for Translational Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Am J Physiol Heart Circ Physiol. 2008 Oct;295(4):H1695-704. doi: 10.1152/ajpheart.00564.2008. Epub 2008 Aug 22.
G protein-coupled receptor kinase 2 (GRK2) is a serine/theorinine kinase that phosphorylates and desensitizes agonist-bound G protein-coupled receptors. GRK2 is increased in expression and activity in lymphocytes and vascular smooth muscle (VSM) in human hypertension and animal models of the disease. Inhibition of GRK2 using the carboxyl-terminal portion of the protein (GRK2ct) has been an effective tool to restore compromised beta-adrenergic receptor (AR) function in heart failure and improve outcome. A well-characterized dysfunction in hypertension is attenuation of betaAR-mediated vasodilation. Therefore, we tested the role of inhibition of GRK2 using GRK2ct or VSM-selective GRK2 gene ablation in a renal artery stenosis model of elevated blood pressure (BP) [the two-kidney, one-clip (2K1C) model]. Use of the 2K1C model resulted in a 30% increase in conscious BP, a threefold increase in plasma norepinephrine levels, and a 50% increase in VSM GRK2 mRNA levels. BP remained increased despite VSM-specific GRK2 inhibition by either GRK2 knockout (GRK2KO) or peptide inhibition (GRK2ct). Although betaAR-mediated dilation in vivo and in situ was enhanced, alpha(1)AR-mediated vasoconstriction was also increased. Further pharmacological experiments using alpha(1)AR antagonists revealed that GRK2 inhibition of expression (GRK2KO) or activity (GRK2ct) enhanced alpha(1D)AR vasoconstriction. This is the first study to suggest that VSM alpha(1D)ARs are a GRK2 substrate in vivo.
G蛋白偶联受体激酶2（GRK2）是一种丝氨酸/苏氨酸激酶，可使与激动剂结合的G蛋白偶联受体磷酸化并使其脱敏。在人类高血压及该疾病的动物模型中，淋巴细胞和血管平滑肌（VSM）中GRK2的表达和活性会增加。使用该蛋白的羧基末端部分（GRK2ct）抑制GRK2，已成为恢复心力衰竭中受损的β-肾上腺素能受体（AR）功能并改善预后的有效工具。高血压中一个特征明确的功能障碍是βAR介导的血管舒张减弱。因此，我们在肾动脉狭窄高血压（BP）模型[双肾单夹（2K1C）模型]中测试了使用GRK2ct抑制GRK2或VSM选择性GRK2基因消融的作用。使用2K1C模型导致清醒BP升高30%，血浆去甲肾上腺素水平增加三倍，VSM中GRK2 mRNA水平增加50%。尽管通过GRK2基因敲除（GRK2KO）或肽抑制（GRK2ct）对VSM特异性抑制GRK2，但BP仍保持升高。尽管体内和原位βAR介导的舒张增强，但α（1）AR介导的血管收缩也增加。使用α（1）AR拮抗剂的进一步药理学实验表明，GRK2表达抑制（GRK2KO）或活性抑制（GRK2ct）增强了α（1D）AR血管收缩。这是第一项表明VSM中的α（1D）ARs在体内是GRK2底物的研究。
