Activation of the Ca2+-sensing receptor stimulates the activity of the epithelial Ca2+ channel TRPV5

Cell Calcium. 2009 Apr;45(4):331-9. doi: 10.1016/j.ceca.2008.12.003. Epub 2009 Jan 20.

Abstract

The extracellular Ca(2+)-sensing receptor (CaR) is a key-player in plasma Ca(2+) homeostasis. It is essentially expressed in the parathyroid glands and along the kidney nephron. The distal convoluted tubules (DCT) and connecting tubules (CNT) in the kidney are involved in active Ca(2+) reabsorption, but the function of the CaR has remained unclear in these segments. Here, the Ca(2+)-selective Transient Receptor Potential Vanilloid-subtype 5 channel (TRPV5) determines active Ca(2+) reabsorption by forming the apical entry gate. In this study we show that the CaR and TRPV5 co-localize at the luminal membrane of DCT/CNT. Furthermore, by patch-clamp and Fura-2-ratiometric measurements we demonstrate that activation of the CaR leads to elevated TRPV5-mediated currents and increases intracellular Ca(2+) concentrations in cells co-expressing TRPV5 and CaR. Activation of CaR initiated a signaling cascade that activated phorbol-12-myristate-13-acetate (PMA)-insensitive protein kinase C (PKC) isoforms. Importantly, mutation of two putative PKC phosphorylation sites, S299 and S654, in TRPV5 prevented the stimulatory effect of CaR activation on channel activity, as did a dominant negative CaR construct, CaR(R185Q). Interestingly, the activity of TRPV6, TRPV5' closest homologue, was not affected by the activated CaR. We conclude that activation of the CaR stimulates TRPV5-mediated Ca(2+) influx via a PMA-insensitive PKC isoform pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Cell Polarity / drug effects
  • Epithelial Cells / cytology
  • Epithelial Cells / drug effects
  • Epithelial Cells / enzymology
  • Epithelial Cells / metabolism*
  • Humans
  • Ion Channel Gating*
  • Isoenzymes / metabolism
  • Kidney Tubules, Distal / cytology
  • Kidney Tubules, Distal / drug effects
  • Kidney Tubules, Distal / metabolism
  • Mice
  • Mutant Proteins / metabolism
  • Phosphorylation / drug effects
  • Protein Kinase C / metabolism
  • Protein Transport / drug effects
  • Rabbits
  • Receptors, Calcium-Sensing / metabolism*
  • Signal Transduction / drug effects
  • TRPV Cation Channels / metabolism*
  • Tetradecanoylphorbol Acetate / pharmacology

Substances

  • Isoenzymes
  • Mutant Proteins
  • Receptors, Calcium-Sensing
  • TRPV Cation Channels
  • TRPV5 protein, human
  • Protein Kinase C
  • Tetradecanoylphorbol Acetate