From the Department of Pathology and Pathophysiology and Department of Cardiology, Sir Run Run Shaw Hospital (J.H., K.Z., H.C.), Zhejiang University School of Medicine, Hangzhou, China.
Department of Cardiology, Lishui Hospital, Zhejiang University School of Medicine, China. (C.C., C.Z.).
Arterioscler Thromb Vasc Biol. 2020 Jul;40(7):1705-1721. doi: 10.1161/ATVBAHA.120.314172. Epub 2020 Apr 9.
A decrease in nitric oxide, leading to vascular smooth muscle cell proliferation, is a common pathological feature of vascular proliferative diseases. Nitric oxide synthesis by eNOS (endothelial nitric oxide synthase) is precisely regulated by protein kinases including AKT1. ENH (enigma homolog protein) is a scaffolding protein for multiple protein kinases, but whether it regulates eNOS activation and vascular remodeling remains unknown. Approach and Results: ENH was upregulated in injured mouse arteries and human atherosclerotic plaques and was associated with coronary artery disease. Neointima formation in carotid arteries, induced by ligation or wire injury, was greatly decreased in endothelium-specific ENH-knockout mice. Vascular ligation reduced AKT and eNOS phosphorylation and nitric oxide production in the endothelium of control but not ENH-knockout mice. ENH was found to interact with AKT1 and its phosphatase PHLPP2 (pleckstrin homology domain and leucine-rich repeat protein phosphatase 2). AKT and eNOS activation were prolonged in VEGF (vascular endothelial growth factor)-induced ENH- or PHLPP2-deficient endothelial cells. Inhibitors of either AKT or eNOS effectively restored ligation-induced neointima formation in ENH-knockout mice. Moreover, endothelium-specific PHLPP2-knockout mice displayed reduced ligation-induced neointima formation. Finally, PHLPP2 was increased in the endothelia of human atherosclerotic plaques and blood cells from patients with coronary artery disease.
ENH forms a complex with AKT1 and its phosphatase PHLPP2 to negatively regulate AKT1 activation in the artery endothelium. AKT1 deactivation, a decrease in nitric oxide generation, and subsequent neointima formation induced by vascular injury are mediated by ENH and PHLPP2. ENH and PHLPP2 are thus new proatherosclerotic factors that could be therapeutically targeted.
一氧化氮（NO）的减少会导致血管平滑肌细胞增殖，这是血管增殖性疾病的共同病理特征。内皮型一氧化氮合酶（eNOS）合成的 NO 受到包括 AKT1 在内的多种蛋白激酶的精确调控。ENH（谜蛋白同源物）是多种蛋白激酶的支架蛋白，但它是否调节 eNOS 激活和血管重塑尚不清楚。
ENH 在受损的小鼠动脉和人类动脉粥样硬化斑块中上调，并与冠心病相关。内皮细胞特异性敲除 ENH 的小鼠，其颈动脉中的新生内膜形成（由结扎或线损伤诱导）大大减少。血管结扎减少了对照组内皮细胞中 AKT 和 eNOS 的磷酸化及 NO 的产生，但敲除 ENH 的内皮细胞中没有减少。发现 ENH 与 AKT1 及其磷酸酶 PHLPP2（pleckstrin 同源结构域和富含亮氨酸重复蛋白磷酸酶 2）相互作用。在 VEGF（血管内皮生长因子）诱导的 ENH 或 PHLPP2 缺陷型内皮细胞中，AKT 和 eNOS 的激活延长。AKT 或 eNOS 的抑制剂能有效恢复敲除 ENH 的小鼠中结扎诱导的新生内膜形成。此外，内皮细胞特异性敲除 PHLPP2 的小鼠显示结扎诱导的新生内膜形成减少。最后，人动脉粥样硬化斑块的内皮细胞和冠心病患者的血液细胞中 PHLPP2 增加。
ENH 与 AKT1 及其磷酸酶 PHLPP2 形成复合物，在内皮细胞中负调控 AKT1 的激活。血管损伤诱导的 AKT1 失活、NO 生成减少和随后的新生内膜形成由 ENH 和 PHLPP2 介导。因此，ENH 和 PHLPP2 是新的促动脉粥样硬化因子，可作为治疗靶点。
