Na +/H + exchange regulatory factor 1 is required for ROMK1 K + channel expression in the surface membrane of cultured M-1 cortical collecting duct cells

Biochem Biophys Res Commun. 2017 Jul 22;489(2):116-122. doi: 10.1016/j.bbrc.2017.05.104. Epub 2017 May 19.

Abstract

The ROMK1 K+ channel, a member of the ROMK channel family, is the major candidate for the K+ secretion pathway in the renal cortical collecting duct (CCD). ROMK1 possesses a PDZ domain-binding motif at its C-terminus that is considered a modulator of ROMK1 expression via interaction with Na+/H+ exchange regulatory factor (NHERF) 1 and NHERF2 scaffold protein. Although NHERF1 is a potential binding partner of the ROMK1 K+ channel, the interaction between NHERF1 and K+ channel activity remains unclear. Therefore, in this study, we knocked down NHERF1 in cultured M-1 cells derived from mouse CCD and investigated the surface expression and K+ channel current in these cells after exogenous transfection with EGFP-ROMK1. NHERF1 knockdown resulted in reduced surface expression of ROMK1 as indicated by a cell biotinylation assay. Using the patch-clamp technique, we further found that the number of active channels per patched membrane and the Ba2+-sensitive whole-cell K+ current were decreased in the knockdown cells, suggesting that reduced K+ current was accompanied by decreased surface expression of ROMK1 in the NHERF1 knockdown cells. Our results provide evidence that NHERF1 mediates K+ current activity through acceleration of the surface expression of ROMK1 K+ channels in M-1 cells.

Keywords: Cortical collecting duct; K(+) channel; M-1 cell; NHERF1; ROMK1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Membrane / metabolism*
  • Cells, Cultured
  • Kidney Tubules, Collecting / cytology*
  • Mice
  • Phosphoproteins / metabolism*
  • Potassium Channels, Inwardly Rectifying / genetics
  • Potassium Channels, Inwardly Rectifying / metabolism*
  • Sodium-Hydrogen Exchangers / metabolism*

Substances

  • Kcnj1 protein, mouse
  • Phosphoproteins
  • Potassium Channels, Inwardly Rectifying
  • Sodium-Hydrogen Exchangers
  • sodium-hydrogen exchanger regulatory factor