Chin Alfred C, Gao Zhe, Riley Andrew M, Furkert David, Wittwer Christopher, Dutta Amit, Rojas Tomas, Semenza Evan R, Felder Robin A, Pluznick Jennifer L, Jessen Henning J, Fiedler Dorothea, Potter Barry V L, Snyder Solomon H, Fu Chenglai
The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Tianjin Key Laboratory of Metabolic Diseases, Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, China.
Sci Adv. 2020 Oct 28;6(44). doi: 10.1126/sciadv.abb8542. Print 2020 Oct.
Sodium/potassium-transporting adenosine triphosphatase (Na/K-ATPase) is one of the most abundant cell membrane proteins and is essential for eukaryotes. Endogenous negative regulators have long been postulated to play an important role in regulating the activity and stability of Na/K-ATPase, but characterization of these regulators has been elusive. Mechanisms of regulating Na/K-ATPase homeostatic turnover are unknown. Here, we report that 5-diphosphoinositol 1,2,3,4,6-pentakisphosphate (5-InsP), generated by inositol hexakisphosphate kinase 1 (IP6K1), promotes physiological endocytosis and downstream degradation of Na/K-ATPase-α1. Deletion of IP6K1 elicits a twofold enrichment of Na/K-ATPase-α1 in plasma membranes of multiple tissues and cell types. Using a suite of synthetic chemical biology tools, we found that 5-InsP binds the RhoGAP domain of phosphatidylinositol 3-kinase (PI3K) p85α to disinhibit its interaction with Na/K-ATPase-α1. This recruits adaptor protein 2 (AP2) and triggers the clathrin-mediated endocytosis of Na/K-ATPase-α1. Our study identifies 5-InsP as an endogenous negative regulator of Na/K-ATPase-α1.
钠/钾转运三磷酸腺苷酶（Na/K-ATPase）是最丰富的细胞膜蛋白之一，对真核生物至关重要。长期以来，人们一直推测内源性负调节因子在调节Na/K-ATPase的活性和稳定性方面发挥重要作用，但这些调节因子的特性一直难以捉摸。调节Na/K-ATPase稳态周转的机制尚不清楚。在这里，我们报告由肌醇六磷酸激酶1（IP6K1）产生的5-二磷酸肌醇1,2,3,4,6-五磷酸（5-InsP）促进Na/K-ATPase-α1的生理性内吞作用和下游降解。IP6K1的缺失导致多种组织和细胞类型的质膜中Na/K-ATPase-α1富集两倍。使用一系列合成化学生物学工具，我们发现5-InsP与磷脂酰肌醇3-激酶（PI3K）p85α的RhoGAP结构域结合，以解除其与Na/K-ATPase-α1的相互作用。这招募衔接蛋白2（AP2）并触发网格蛋白介导的Na/K-ATPase-α1内吞作用。我们的研究确定5-InsP是Na/K-ATPase-α1的内源性负调节因子。
