title: Direct modulation of TRPM4 and TRPM3 channels by the phospholipase C inhibitor U73122.
abstract: Signalling through phospholipase C (PLC) controls many cellular processes. Much information on the relevance of this important pathway has been derived from pharmacological inhibition of the enzymatic activity of PLC. We found that the most frequently employed PLC inhibitor, U73122, activates endogenous ionic currents in widely used cell lines. Given the extensive use of U73122 in research, we set out to identify these U73122-sensitive ion channels.
  
  
  
  We performed detailed biophysical analysis of the U73122-induced currents in frequently used cell lines.
  
  
  
  At concentrations required to inhibit PLC, U73122 modulated the activity of transient receptor potential melastatin (TRPM) channels through covalent modification. U73122 was shown to be a potent agonist of ubiquitously expressed TRPM4 channels and activated endogenous TRPM4 channels in CHO cells independently of PLC and of the downstream second messengers PI(4,5)P2 and Ca(2+) . U73122 also potentiated Ca(2) (+) -dependent TRPM4 currents in human Jurkat T-cells, endogenous TRPM4 in HEK293T cells and recombinant human TRPM4. In contrast to TRPM4, TRPM3 channels were inhibited whereas the closely related TRPM5 channels were insensitive to U73122, showing that U73122 exhibits high specificity within the TRPM channel family.
  
  
  
  Given the widespread expression of TRPM4 and TRPM3 channels, these actions of U73122 must be considered when interpreting its effects on cell function. U73122 may also be useful for identifying and characterizing TRPM channels in native tissue, thus facilitating the analysis of their physiology.
authors.affiliation: Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Leitner
authors.affiliation: Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany.
authors.forename: Niklas
authors.initials: N
authors.lastname: Michel
authors.affiliation: Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Behrendt
authors.affiliation: Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany.
authors.forename: Marlen
authors.initials: M
authors.lastname: Dierich
authors.affiliation: Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Dembla
authors.affiliation: Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany.
authors.forename: Bettina U
authors.initials: BU
authors.lastname: Wilke
authors.affiliation: Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany.
authors.forename: Maik
authors.initials: M
authors.lastname: Konrad
authors.affiliation: Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany.|Department of Ophthalmology, University of Bonn, Bonn, Germany.
authors.forename: Moritz
authors.identifier: 0000-0002-4416-3421
authors.initials: M
authors.lastname: Lindner
authors.affiliation: Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Oberwinkler
authors.affiliation: Institute of Physiology and Pathophysiology, Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany.
authors.forename: Dominik
authors.initials: D
authors.lastname: Oliver
mesh_terms: D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004963:Estrenes / Q000008:administration & dosage / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D015394:Molecular Structure; D011760:Pyrrolidinones / Q000008:administration & dosage / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D050053:TRPM Cation Channels / Q000819:agonists* / Q000378:metabolism; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D004963:Estrenes; D011760:Pyrrolidinones; D050053:TRPM Cation Channels; C475667:TRPM3 protein, human; C437888:TRPM4 protein, human; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D010738:Type C Phospholipases