ZNRF2 is released from membranes by growth factors and with ZNRF1 regulates the Na+/K+ATPase

Abstract

Here we describe a phosphorylation-based reverse myristoyl switch for mammalian ZNRF2, and show that this E3 ubiquitin ligase and its sister ZNRF1 regulate the sodium/potassium pump (Na+/K+ATPase). N-myristoylation targets 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 with Uev1a specifies formation of Lys63-ubiquitin linkages. ZNRF1 and ZNRF2 can ubiquitylate the nucleotide-binding/phosphorylation region of Na+/K+ATPase α1. Ouabain, a Na+/K+ATPase inhibitor and therapeutic cardiac glycoside, decreases ZNRF1 protein levels, while 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 sodium/potassium pump that is tuned to changing demands in many physiological contexts.