MRC Protein Phosphorylation Unit, James Black Centre, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.
J Cell Sci. 2012 Oct 1;125(Pt 19):4662-75. doi: 10.1242/jcs.110296. Epub 2012 Jul 13.
Here, we describe a phosphorylation-based reverse myristoyl switch for mammalian ZNRF2, and show that this E3 ubiquitin ligase and its sister protein ZNRF1 regulate the Na(+)/K(+) pump (Na(+)/K(+)ATPase). N-myristoylation localizes ZNRF1 and ZNRF2 to intracellular membranes and enhances their activity. However, when ZNRF2 is phosphorylated in response to agonists including insulin and growth factors, it binds to 14-3-3 and is released into the cytosol. On membranes, ZNRF1 and ZNRF2 interact with the Na(+)/K(+)ATPase α1 subunit via their UBZ domains, while their RING domains interact with E2 proteins, predominantly Ubc13 that, together with Uev1a, mediates formation of Lys63-ubiquitin linkages. ZNRF1 and ZNRF2 can ubiquitylate the cytoplasmic loop encompassing the nucleotide-binding and phosphorylation regions of the Na(+)/K(+)ATPase α1 subunit. Ouabain, a Na(+)/K(+)ATPase inhibitor and therapeutic cardiac glycoside, decreases ZNRF1 protein levels, whereas knockdown of ZNRF2 inhibits the ouabain-induced decrease of cell surface and total Na(+)/K(+)ATPase α1 levels. Thus, ZNRF1 and ZNRF2 are new players in regulation of the ubiquitous Na(+)/K(+)ATPase that is tuned to changing demands in many physiological contexts.
在这里，我们描述了一种基于磷酸化的哺乳动物 ZNRF2 的反向豆蔻酰开关，并表明这种 E3 泛素连接酶及其姐妹蛋白 ZNRF1 调节钠（+）/钾（+）泵（Na（+）/K（+）ATPase）。ZNRF1 和 ZNRF2 的豆蔻酰化将它们定位在内质网膜上，并增强其活性。然而，当 ZNRF2 响应包括胰岛素和生长因子在内的激动剂而被磷酸化时，它会与 14-3-3 结合并释放到细胞质中。在膜上，ZNRF1 和 ZNRF2 通过其 UBZ 结构域与 Na（+）/K（+）ATPase α1 亚基相互作用，而其 RING 结构域与 E2 蛋白相互作用，主要是 Ubc13，它与 Uev1a 一起介导 Lys63-泛素连接的形成。ZNRF1 和 ZNRF2 可以泛素化包含 Na（+）/K（+）ATPase α1 亚基核苷酸结合和磷酸化区域的细胞质环。哇巴因，一种 Na（+）/K（+）ATPase 抑制剂和治疗性强心苷，降低 ZNRF1 蛋白水平，而 ZNRF2 的敲低抑制哇巴因诱导的细胞表面和总 Na（+）/K（+）ATPase α1 水平的降低。因此，ZNRF1 和 ZNRF2 是调节在许多生理环境中适应变化需求的普遍存在的 Na（+）/K（+）ATPase 的新成员。
