title: Activation of the Ca2+-sensing receptor stimulates the activity of the epithelial Ca2+ channel TRPV5.
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.
authors.affiliation: Department of Physiology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors.forename: Catalin N
authors.initials: CN
authors.lastname: Topala
authors.forename: Joost P H
authors.initials: JP
authors.lastname: Schoeber
authors.forename: Lydia E
authors.initials: LE
authors.lastname: Searchfield
authors.forename: Daniela
authors.initials: D
authors.lastname: Riccardi
authors.forename: Joost G J
authors.initials: JG
authors.lastname: Hoenderop
authors.forename: René J M
authors.initials: RJ
authors.lastname: Bindels
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D016764:Cell Polarity / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D015640:Ion Channel Gating; D007527:Isoenzymes / Q000378:metabolism; D007686:Kidney Tubules, Distal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D050505:Mutant Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D011817:Rabbits; D044169:Receptors, Calcium-Sensing / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D050916:TRPV Cation Channels / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D007527:Isoenzymes; D050505:Mutant Proteins; D044169:Receptors, Calcium-Sensing; D050916:TRPV Cation Channels; C492239:TRPV5 protein, human; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate