title: Regulation of TRPV1 ion channel by phosphoinositide (4,5)-bisphosphate: the role of membrane asymmetry.
abstract: Membrane asymmetry is essential for generating second messengers that act in the cytosol and for trafficking of membrane proteins and membrane lipids, but the role of asymmetry in regulating membrane protein function remains unclear. Here we show that the signaling lipid phosphoinositide 4,5-bisphosphate (PI(4,5)P2) has opposite effects on the function of TRPV1 ion channels depending on which leaflet of the cell membrane it resides in. We observed potentiation of capsaicin-activated TRPV1 currents by PI(4,5)P2 in the intracellular leaflet of the plasma membrane but inhibition of capsaicin-activated currents when PI(4,5)P2 was in both leaflets of the membrane, although much higher concentrations of PI(4,5)P2 in the extracellular leaflet were required for inhibition compared with the concentrations of PI(4,5)P2 in the intracellular leaflet that produced activation. Patch clamp fluorometry using a synthetic PI(4,5)P2 whose fluorescence reports its concentration in the membrane indicates that PI(4,5)P2 must incorporate into the extracellular leaflet for its inhibitory effects to be observed. The asymmetry-dependent effect of PI(4,5)P2 may resolve the long standing controversy about whether PI(4,5)P2 is an activator or inhibitor of TRPV1. Our results also underscore the importance of membrane asymmetry and the need to consider its influence when studying membrane proteins reconstituted into synthetic bilayers.
authors.affiliation: Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington 98195-7290 and.
authors.forename: Eric N
authors.initials: EN
authors.lastname: Senning
authors.affiliation: Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington 98195-7290 and.
authors.forename: Marcus D
authors.initials: MD
authors.lastname: Collins
authors.affiliation: Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington 98195-7290 and; Laboratory of Biophysics of Ion Channels, Department of General Physiology of the Nervous System, Bogomoletz Institute of Physiology, International Center for Molecular Physiology, 01024 Kyiv, Ukraine.
authors.forename: Anastasiia
authors.initials: A
authors.lastname: Stratiievska
authors.affiliation: Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington 98195-7290 and.
authors.forename: Carmen A
authors.initials: CA
authors.lastname: Ufret-Vincenty
authors.affiliation: Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington 98195-7290 and. Electronic address: seg@uw.edu.
authors.forename: Sharona E
authors.initials: SE
authors.lastname: Gordon
mesh_terms: D000982:Antipruritics / Q000494:pharmacology; D002211:Capsaicin / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000235:genetics / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D000982:Antipruritics; D019269:Phosphatidylinositol 4,5-Diphosphate; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; D002211:Capsaicin
keywords: Ion Channels; Membrane; Membrane Lipids; PI(4,5)P2; Phosphoinositides; Phospholipid; TRPV1