title: PIP2 activates TRPV5 and releases its inhibition by intracellular Mg2+.
abstract: The 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+.
authors.affiliation: Department of Medicine and Charles and Jane Pak Center for Mineral Metabolism and Clinical Research, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Lee
authors.forename: Seung-Kuy
authors.initials: SK
authors.lastname: Cha
authors.forename: Tie-Jun
authors.initials: TJ
authors.lastname: Sun
authors.forename: Chou-Long
authors.initials: CL
authors.lastname: Huang
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D006868:Hydrolysis; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology*; D008564:Membrane Potentials / Q000502:physiology; D008954:Models, Biological; D018408:Patch-Clamp Techniques; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D011817:Rabbits; D050916:TRPV Cation Channels / Q000187:drug effects* / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D019269:Phosphatidylinositol 4,5-Diphosphate; D050916:TRPV Cation Channels; D010738:Type C Phospholipases; D008274:Magnesium