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

Abstract

SummaryHere, 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 a1 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 a1 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 a1 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.

Oxidative stress–dependent phosphorylation activates ZNRF1 to induce neuronal/axonal degeneration

“…For example, the E3 ligase Itch protein alters its catalytic activity through a conformational change by c-Jun amino-terminal kinase-mediated phosphorylation, which induces the disruption of an intramolecular inhibitory interaction ( Gallagher et al, 2006 ). The phosphorylation of ZNRF2, another member of the ZNRF protein family, influences its interaction with the substrate, the 14–3-3 protein, and its association with intracellular membranes ( Hoxhaj et al, 2012 ). In this context, the phosphorylation of ZNRF2 at serine 19, which is located outside the zinc finger region responsible for substrate binding, releases ZNRF2 from the plasma membrane to the cytosol, resulting in decreased catalytic activity.…”

Common variants in or near ZNRF1, COLEC12, SCYL1BP1 and API5 are associated with diabetic retinopathy in Chinese patients with type 2 diabetes

“…ZNRF1 encodes an E3 ubiquitin-protein ligase that plays a role in neuralcell differentiation. It has been reported to interact with tubulin, promote Wallerian degeneration and regulate Na + /K + ATPase [25][26][27]. COLEC12 encodes a member of the C-lectin family.…”

The E3 ubiquitin ligase ZNRF2 is a substrate of mTORC1 and regulates its activation by amino acids

“…Our previous study showed that the E3 ubiquitin ligase ZNRF2 is an enzyme tethered to intracellular membranes, via an N-myristoyl moiety, where it ubiquitylates the Na + /K + ATPase pump ( Hoxhaj et al, 2012 ). ZNRF2 is robustly phosphorylated on Ser19, Ser82 and Ser145 in response to growth factors, phorbol ester (PMA) and forskolin.…”