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

• Published in: Cell calcium (Edinburgh) 2009-04, Vol.45 (4), p.331-339
• Main Authors: Topala, Catalin N, Schoeber, Joost P.H, Searchfield, Lydia E, Riccardi, Daniela, Hoenderop, Joost G.J, Bindels, René J.M
• Format: Article
• Language: English
• Subjects: Advanced Basic Science; 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; Tetradecanoylphorbol Acetate - pharmacology; TRPV Cation Channels - metabolism
• ISSN: 0143-4160; 1532-1991
• DOI: 10.1016/j.ceca.2008.12.003

Abstract The extracellular Ca2+ -sensing receptor (CaR) is a key-player in plasma Ca2+ 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 Ca2+ reabsorption, but the function of the CaR has remained unclear in these segments. Here, the Ca2+ -selective Transient Receptor Potential Vanilloid-subtype 5 channel (TRPV5) determines active Ca2+ 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 Ca2+ 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, CaRR185Q . 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 Ca2+ influx via a PMA-insensitive PKC isoform pathway.