External Ca2+regulates polycystin-2 (TRPP2) cation currents in LLC-PK1 renal epithelial cells.
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+(1.2mM), decreased by 30.2% in zero (nominal) Ca2+and conversely, increased by 38% in high external Ca2+(6.2mM). 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.
Alberta Diabetes Institute, Department of Pharmacology, University of Edmonton, Alberta, Canada.
Xiao Qing
XQ
Dai
Laboratorio de Canales Iónicos, CONICET, Cátedra de Biofísica y Bioestadística, Facultad de Odontología, UBA, Buenos Aires, Argentina.
Paula L
PL
Perez
Nephrology Division, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA.
Gonzalo
G
Soria
Laboratorio de Canales Iónicos, CONICET, Cátedra de Biofísica y Bioestadística, Facultad de Odontología, UBA, Buenos Aires, Argentina.
Noelia
N
Scarinci
Laboratorio de Canales Iónicos, CONICET, Cátedra de Biofísica y Bioestadística, Facultad de Odontología, UBA, Buenos Aires, Argentina.
Mariano
M
Smoler
Nephrology Division, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA.
D Cristian
DC
Morsucci
Molecular Biology and Biochemistry Core Facility, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada.
Kunimasa
K
Suzuki
Laboratorio de Canales Iónicos, CONICET, Cátedra de Biofísica y Bioestadística, Facultad de Odontología, UBA, Buenos Aires, Argentina.
María Del Rocío
MDR
Cantero
Nephrology Division, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA; Laboratorio de Canales Iónicos, CONICET, Cátedra de Biofísica y Bioestadística, Facultad de Odontología, UBA, Buenos Aires, Argentina. Electronic address: hcantiello@yahoo.com.ar.
Horacio F
HF
Cantiello
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D013552:Swine; D050396:TRPP Cation Channels / Q000378:metabolism*
D050396:TRPP Cation Channels; D002118:Calcium
Ca(2+) sensing receptor; Polycystin-2; TRP channels; TRPP2