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PIP2 activates TRPV5 and releases its inhibition by intracellular Mg2+ Lee J; Cha SK; Sun TJ; Huang CLJ Gen Physiol 2005[Nov]; 126 (5): 439-51The transient receptor potential type V5 channel (TRPV5) is a Ca2+-selective TRP channel important for epithelial Ca2+ transport. Intracellular Mg2+ causes a fast voltage-dependent block of the TRPV5 channel by binding to the selectivity filter. Here, we report that intracellular Mg2+ binding to the selectivity filter of TRPV5 also causes a slower reversible conformational change leading to channel closure. We further report that PIP2 activates TRPV5. Activation of TRPV5 by PIP2 is independent of Mg2+. Yet, PIP2 decreases sensitivity of the channel to the Mg2+-induced slow inhibition. Mutation of aspartate-542, a critical Mg2+-binding site in the selectivity filter, abolishes Mg2+-induced slow inhibition. PIP2 has no effects on Mg2+-induced voltage-dependent block. Thus, PIP2 prevents the Mg2+-induced conformational change without affecting Mg2+ binding to the selectivity filter. Hydrolysis of PIP2 via receptor activation of phospholipase C sensitizes TRPV5 to the Mg2+-induced slow inhibition. These results provide a novel mechanism for regulation of TRP channels by phospholipase C-activating hormones via alteration of the sensitivity to intracellular Mg2+.|Animals[MESH]|CHO Cells[MESH]|Cricetinae[MESH]|Dose-Response Relationship, Drug[MESH]|Electrophysiology[MESH]|Hydrolysis[MESH]|Ion Channel Gating/drug effects/physiology[MESH]|Kinetics[MESH]|Magnesium/metabolism/*pharmacology[MESH]|Membrane Potentials/physiology[MESH]|Models, Biological[MESH]|Patch-Clamp Techniques[MESH]|Phosphatidylinositol 4,5-Diphosphate/*metabolism[MESH]|Rabbits[MESH]|TRPV Cation Channels/*drug effects/metabolism[MESH]|Type C Phospholipases/metabolism[MESH] |
