Human RGS14 binds NHERF1 and regulates NPT2A‐mediated phosphate uptake: Disruption by genetic variants

Abstract

RGS14 is a multifunctional scaffolding protein that integrates G protein, MAPK and Ca++/CaM signaling pathways. Most of what we know about RGS14 comes from studies in rodent brain where it acts as a natural suppressor of synaptic plasticity and hippocampal‐based learning, though other studies implicate a role for RGS14 in myocardial remodeling. Recent genome‐wide association studies have implicated RGS14 in disordered phosphate metabolism, an effect of chronic kidney disease. The RGS14 gene is adjacent to SLC34A1 on human chromosome 5 that encodes the NPT2A sodium‐phosphate cotransporter, which mediates hormone‐sensitive phosphate resorption in renal proximal tubules. Therefore, the goal of these studies was to define a possible role for RGS14 in hormone‐sensitive phosphate transport. Human/primate RGS14 differ from rodent proteins by possessing a carboxy‐terminal extension encoding a Type I PDZ ligand (DSAL). Of note, several rare human mutations have been reported in this region of RGS14 located at residues 563 and 565, corresponding to positions −1 (A565S, A565V) and −3 (D563N, D563G) of the PDZ ligand. The family of PDZ adapter proteins assemble a variety of membrane‐associated proteins, including transporters, receptors, and ion channels, and signaling molecules in short‐lived functional units. The PDZ adapter NHERF1 is expressed in renal proximal tubules, and contains two PDZ domains (PDZ1 and PDZ2). NHERF1 binds the PDZ ligand carboxy tail of NPT2A to promote its phosphate uptake, and this NPT2A:NHERF1 complex is inhibited by parathyroid hormone (PTH) acting at the PTH1 receptor. Here we report that RGS14 is expressed in proximal and distal renal tubules of humans, and that RGS14 binds to NHERF1 via the PDZ2 domain. PTH inhibits NPT2A uptake of phosphate, and RGS14 blocks this action. Of the RGS14 genetic variants tested, D563N disrupted binding to NHERF1 and RGS14 actions on PTH‐sensitive phosphate uptake, whereas D563G, A565S and A565V were innocuous. Computational analysis and molecular dynamics modeling of NHERF1 PDZ binding to the RGS14 C‐terminal PDZ ligand define the structural determinants of this interaction. Taken together, our findings are consistent with the idea that RGS14 contributes to PTH‐sensitive phosphate transport in humans, and that RGS14 coding variants may cause disordered phosphate metabolism.Support or Funding InformationNational Institutes of Health (NIH) awards DK105811, DK111427 (PAF); NS037112, NS102652 (JRH).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.