University of Texas Southwestern Medical Center, Division of Digestive and Liver Diseases, Dallas, Texas 75390, USA.
J Biol Chem. 2012 Apr 6;287(15):12309-20. doi: 10.1074/jbc.M111.320465. Epub 2012 Jan 31.
Endothelial cell nitric-oxide (NO) synthase (eNOS), the enzyme responsible for synthesis of NO in the vasculature, undergoes extensive post-translational modifications that modulate its activity. Here we have identified a novel eNOS interactor, G-protein-coupled receptor (GPCR) kinase interactor-1 (GIT1), which plays an unexpected role in GPCR stimulated NO signaling. GIT1 interacted with eNOS in the endothelial cell cytoplasm, and this robust association was associated with stimulatory eNOS phosphorylation (Ser(1177)), enzyme activation, and NO synthesis. GIT1 knockdown had the opposite effect. Additionally, GIT1 expression was reduced in sinusoidal endothelial cells after liver injury, consistent with previously described endothelial dysfunction in this disease. Re-expression of GIT1 after liver injury rescued the endothelial phenotype. These data emphasize the role of GPCR signaling partners in eNOS function and have fundamental implications for vascular disorders involving dysregulated eNOS.
内皮细胞一氧化氮合酶（eNOS）是血管中合成一氧化氮的酶，它经历广泛的翻译后修饰，从而调节其活性。在这里，我们鉴定了一种新的 eNOS 相互作用蛋白，G 蛋白偶联受体激酶相互作用蛋白 1（GIT1），它在 GPCR 刺激的 NO 信号中发挥了意想不到的作用。GIT1 与内皮细胞质中的 eNOS 相互作用，这种强烈的相互作用与刺激的 eNOS 磷酸化（Ser(1177)）、酶激活和 NO 合成有关。GIT1 的敲低则产生相反的效果。此外，在肝损伤后，窦状内皮细胞中的 GIT1 表达减少，与该疾病中先前描述的内皮功能障碍一致。肝损伤后 GIT1 的再表达挽救了内皮表型。这些数据强调了 GPCR 信号伙伴在 eNOS 功能中的作用，对涉及失调的 eNOS 的血管紊乱具有根本意义。
