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Hydrolysis of phosphatidylinositol 4,5-bisphosphate mediates calcium-induced inactivation of TRPV6 channels Thyagarajan B; Lukacs V; Rohacs TJ Biol Chem 2008[May]; 283 (22): 14980-7TRPV6 is a member of the transient receptor potential superfamily of ion channels that facilitates Ca(2+) absorption in the intestines. These channels display high selectivity for Ca(2+), but in the absence of divalent cations they also conduct monovalent ions. TRPV6 channels have been shown to be inactivated by increased cytoplasmic Ca(2+) concentrations. Here we studied the mechanism of this Ca(2+)-induced inactivation. Monovalent currents through TRPV6 substantially decreased after a 40-s application of Ca(2+), but not Ba(2+). We also show that Ca(2+), but not Ba(2+), influx via TRPV6 induces depletion of phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2) or PIP(2)) and the formation of inositol 1,4,5-trisphosphate. Dialysis of DiC(8) PI(4,5)P(2) through the patch pipette inhibited Ca(2+)-dependent inactivation of TRPV6 currents in whole-cell patch clamp experiments. PI(4,5)P(2) also activated TRPV6 currents in excised patches. PI(4)P, the precursor of PI(4,5)P(2), neither activated TRPV6 in excised patches nor had any effect on Ca(2+)-induced inactivation in whole-cell experiments. Conversion of PI(4,5)P(2) to PI(4)P by a rapamycin-inducible PI(4,5)P(2) 5-phosphatase inhibited TRPV6 currents in whole-cell experiments. Inhibiting phosphatidylinositol 4 kinases with wortmannin decreased TRPV6 currents and Ca(2+) entry into TRPV6-expressing cells. We propose that Ca(2+) influx through TRPV6 activates phospholipase C and the resulting depletion of PI(4,5)P(2) contributes to the inactivation of TRPV6.|Barium/metabolism[MESH]|Calcium Channels/*metabolism[MESH]|Calcium/metabolism[MESH]|Cell Line[MESH]|Humans[MESH]|Hydrolysis[MESH]|Inositol 1,4,5-Trisphosphate/metabolism[MESH]|Intestinal Absorption/physiology[MESH]|Intestinal Mucosa/metabolism[MESH]|Ion Transport/physiology[MESH]|Patch-Clamp Techniques[MESH]|Phosphatidylinositol 4,5-Diphosphate/*metabolism[MESH]|Substrate Specificity/physiology[MESH]|TRPV Cation Channels/*metabolism[MESH]|Type C Phospholipases/metabolism[MESH] |
