Akt2（蛋白激酶 Bβ）稳定了 ATP7A，一种细胞外超氧化物歧化酶的铜转运蛋白，在血管平滑肌中：2 型糖尿病中限制内皮功能障碍的新机制。
Akt2 (Protein Kinase B Beta) Stabilizes ATP7A, a Copper Transporter for Extracellular Superoxide Dismutase, in Vascular Smooth Muscle: Novel Mechanism to Limit Endothelial Dysfunction in Type 2 Diabetes Mellitus.
机构信息
From the Vascular Biology Center (V.S., Z.B., D.S., M.U.-F., T.F.), Department of Pharmacology and Toxicology (V.S., T.F.), Department of Medicine (Cardiology) (Z.B., M.U.-F.), and Department of Surgery (V.S.P.), Medical College of Georgia at Augusta University; Departments of Medicine (Cardiology) and Pharmacology (V.S., T.F.), Department of Pharmacology (M.N.O., J.P.O., M.U.-F.), Center for Cardiovascular Research (V.S., J.P.O., M.U.-F., T.F.), Department of Physical Therapy (S.A.P.), and Department of Biochemistry and Molecular Genetics (N.H.), University of Illinois at Chicago; Department of Medicine and Physiology, University of Arizona, Tucson (A.M.), Jesse Brown Veterans Affairs Medical Center, Chicago, IL (V.S., T.F.); and Charlie Norwood Veterans Affairs Medical Center, Augusta, GA (V.S., T.F.).
出版信息
Arterioscler Thromb Vasc Biol. 2018 Mar;38(3):529-541. doi: 10.1161/ATVBAHA.117.309819. Epub 2018 Jan 4.
OBJECTIVE
Copper transporter ATP7A (copper-transporting/ATPase) is required for full activation of SOD3 (extracellular superoxide dismutase), which is secreted from vascular smooth muscle cells (VSMCs) and anchors to endothelial cell surface to preserve endothelial function by scavenging extracellular superoxide. We reported that ATP7A protein expression and SOD3 activity are decreased in insulin-deficient type 1 diabetes mellitus vessels, thereby, inducing superoxide-mediated endothelial dysfunction, which are rescued by insulin treatment. However, it is unknown regarding the mechanism by which insulin increases ATP7A expression in VSMCs and whether ATP7A downregulation is observed in T2DM (type2 diabetes mellitus) mice and human in which insulin-Akt (protein kinase B) pathway is selectively impaired.
APPROACH AND RESULTS
Here we show that ATP7A protein is markedly downregulated in vessels isolated from T2DM patients, as well as those from high-fat diet-induced or db/db T2DM mice. Akt2 (protein kinase B beta) activated by insulin promotes ATP7A stabilization via preventing ubiquitination/degradation as well as translocation to plasma membrane in VSMCs, which contributes to activation of SOD3 that protects against T2DM-induced endothelial dysfunction. Downregulation of ATP7A in T2DM vessels is restored by constitutive active Akt or PTP1B (protein-tyrosine phosphatase 1B-deficient) T2DM mice, which enhance insulin-Akt signaling. Immunoprecipitation, in vitro kinase assay, and mass spectrometry analysis reveal that insulin stimulates Akt2 binding to ATP7A to induce phosphorylation at Ser1424/1463/1466. Furthermore, SOD3 activity is reduced in Akt2 vessels or VSMCs, which is rescued by ATP7A overexpression.
CONCLUSION
Akt2 plays a critical role in ATP7A protein stabilization and translocation to plasma membrane in VSMCs, which contributes to full activation of vascular SOD3 that protects against endothelial dysfunction in T2DM.
目的
铜转运体 ATP7A（铜转运/ATP 酶）对于 SOD3（细胞外超氧化物歧化酶）的完全激活是必需的，SOD3 从血管平滑肌细胞（VSMCs）分泌，并锚定在内皮细胞表面，通过清除细胞外超氧化物来维持内皮功能。我们报道，胰岛素缺乏的 1 型糖尿病血管中 ATP7A 蛋白表达和 SOD3 活性降低，从而诱导超氧化物介导的内皮功能障碍，这可通过胰岛素治疗得到挽救。然而，胰岛素如何增加 VSMCs 中的 ATP7A 表达以及在胰岛素-Akt（蛋白激酶 B）途径选择性受损的 T2DM（2 型糖尿病）小鼠和人中是否观察到 ATP7A 下调尚不清楚。
方法和结果
在这里，我们显示从 T2DM 患者以及高脂肪饮食诱导或 db/db T2DM 小鼠分离的血管中，ATP7A 蛋白明显下调。胰岛素激活的 Akt2（蛋白激酶 Bβ）通过防止泛素化/降解以及向 VSMCs 的质膜易位来促进 ATP7A 的稳定，这有助于 SOD3 的激活，从而防止 T2DM 引起的内皮功能障碍。通过组成型激活 Akt 或 PTP1B（蛋白酪氨酸磷酸酶 1B 缺陷型）T2DM 小鼠可恢复 T2DM 血管中 ATP7A 的下调，从而增强胰岛素-Akt 信号传导。免疫沉淀、体外激酶测定和质谱分析表明，胰岛素刺激 Akt2 与 ATP7A 结合，以诱导 Ser1424/1463/1466 磷酸化。此外，Akt2 血管或 VSMCs 中的 SOD3 活性降低，通过过表达 ATP7A 可得到挽救。
结论
Akt2 在 VSMCs 中 ATP7A 蛋白的稳定和质膜易位中起关键作用，有助于血管 SOD3 的完全激活，从而防止 T2DM 中的内皮功能障碍。
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