title: The Ca2+-activated cation channel TRPM4 is regulated by phosphatidylinositol 4,5-biphosphate.
abstract: Transient receptor potential (TRP) channel, melastatin subfamily (TRPM)4 is a Ca2+-activated monovalent cation channel that depolarizes the plasma membrane and thereby modulates Ca2+ influx through Ca2+-permeable pathways. A typical feature of TRPM4 is its rapid desensitization to intracellular Ca2+ ([Ca2+]i). Here we show that phosphatidylinositol 4,5-biphosphate (PIP2) counteracts desensitization to [Ca2+]i in inside-out patches and rundown of TRPM4 currents in whole-cell patch-clamp experiments. PIP2 shifted the voltage dependence of TRPM4 activation towards negative potentials and increased the channel's Ca2+ sensitivity 100-fold. Conversely, activation of the phospholipase C (PLC)-coupled M1 muscarinic receptor or pharmacological depletion of cellular PIP2 potently inhibited currents through TRPM4. Neutralization of basic residues in a C-terminal pleckstrin homology (PH) domain accelerated TRPM4 current desensitization and strongly attenuated the effect of PIP2, whereas mutations to the C-terminal TRP box and TRP domain had no effect on the PIP2 sensitivity. Our data demonstrate that PIP2 is a strong positive modulator of TRPM4, and implicate the C-terminal PH domain in PIP2 action. PLC-mediated PIP2 breakdown may constitute a physiologically important brake on TRPM4 activity.
authors.affiliation: Department of Physiology, Campus Gasthuisberg, KU Leuven, Leuven, Belgium. bernd.nilius@med.kuleuven.ac.be
authors.forename: Bernd
authors.initials: B
authors.lastname: Nilius
authors.forename: Frank
authors.initials: F
authors.lastname: Mahieu
authors.forename: Jean
authors.initials: J
authors.lastname: Prenen
authors.forename: Annelies
authors.initials: A
authors.lastname: Janssens
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Owsianik
authors.forename: Rudi
authors.initials: R
authors.lastname: Vennekens
authors.forename: Thomas
authors.initials: T
authors.lastname: Voets
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D015640:Ion Channel Gating; D008969:Molecular Sequence Data; D009154:Mutation; D018408:Patch-Clamp Techniques; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000502:physiology*; D017434:Protein Structure, Tertiary; D043643:Receptor, Muscarinic M1 / Q000235:genetics / Q000502:physiology; D050053:TRPM Cation Channels / Q000235:genetics / Q000502:physiology*; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D019269:Phosphatidylinositol 4,5-Diphosphate; D043643:Receptor, Muscarinic M1; D050053:TRPM Cation Channels; C437888:TRPM4 protein, human; D010738:Type C Phospholipases; D002118:Calcium