External Ca2+ regulates polycystin-2 (TRPP2) cation currents in LLC-PK1 renal epithelial cells |
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Authors: | Xiao Qing Dai Paula L. Perez Gonzalo Soria Noelia Scarinci Mariano Smoler D. Cristian Morsucci Kunimasa Suzuki María del Rocío Cantero Horacio F. Cantiello |
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Affiliation: | 1. Alberta Diabetes Institute, Department of Pharmacology, University of Edmonton, Alberta, Canada;2. Nephrology Division, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA;3. Laboratorio de Canales Iónicos, CONICET, Cátedra de Biofísica y Bioestadística, Facultad de Odontología, UBA, Buenos Aires, Argentina;4. Molecular Biology and Biochemistry Core Facility, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada |
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Abstract: | Polycystin-2 (PC2, TRPP2) is a nonselective cation channel whose dysfunction is associated with the onset of autosomal dominant polycystic kidney disease (ADPKD). PC2 contributes to Ca2+ transport and cell signaling in renal epithelia and other tissues. Little is known however, as to the external Ca2+ regulation of PC2 channel function. In this study, we explored the effect of external Ca2+ on endogenous PC2 in wild type LLC-PK1 renal epithelial cells. We obtained whole cell currents at different external Ca2+ concentrations, and observed that the basal whole cell conductance in normal Ca2+(1.2 mM), decreased by 30.2% in zero (nominal) Ca2+ and conversely, increased by 38% in high external Ca2+(6.2 mM). The high Ca2+-increased whole cell currents were completely inhibited by either PC2 gene silencing, or intracellular dialysis with active, but not denatured by boiling, PC2 antibody. Exposure of cells to high Ca2+ was also associated with relocation of PC2 to the plasma membrane. To explore whether a Ca2+ sensing receptor (CaSR) was implicated in the external Ca2+ modulation of PC2 currents, we tested the effect of the CaSR agonists, spermine and the calcimimetic R-568, which largely mimicked the effect of high Ca2+ under Ca2+-free conditions. The CaSR agonist gentamicin also increased the PC2 currents in the presence of normal Ca2+. The presence of CaSR was confirmed by immunocytochemistry, which partially colocalized with the intracellular PC2 protein, in an external Ca2+-dependent manner. The data support a novel Ca2+ sensing mechanism for PC2 expression and functional regulation in renal epithelial cells. |
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Keywords: | TRP channels Polycystin-2 TRPP2 Correspondence to: Laboratorio de Canales Iónicos, CONICET, Cátedra de Biofísica y Bioestadística, Facultad de Odontología, UBA, Marcelo T. de Alvear 2142 16B, CABA 1122, Argentina. |
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