title: Molecular and functional characterization of the melastatin-related cation channel TRPM3.
abstract: Proteins of the mammalian TRP (transient receptor potential) family form a heterogenous group of cation channels important for cellular Ca2+ signaling and homeostasis. Here we present the full-length sequence of TRPM3, a member of the melastatin-like subfamily (TRPM) of TRP channels. TRPM3 expression was found in human kidney and brain. HEK293 cells transiently transfected with TRPM3 showed a constitutive Ca2+ and Mn2+ entry. Whole-cell patch clamp experiments confirmed the spontaneous activity of TRPM3 and revealed permeability ratios PCa/PNa of 1.57 and PNa/PCs of 0.75. In cell-attached patches, spontaneous inward and outward currents were observed. At negative membrane potentials and in the presence of either 140 mm Cs+, 140 mm Na+, or 100 mm Ca2+ in the pipette solution, the single channel conductance levels were 133, 83, and 65 pS, respectively. The Ca2+ entry in TRPM3-expressing HEK293 cells increased during treatment with hypotonic extracellular solution. The reduction of extracellular osmolarity was accompanied by cell swelling, suggesting volume-regulated activity of TRPM3. From its function and expression in human kidney, we propose a role of TRPM3 in renal Ca2+ homeostasis.
authors.affiliation: Institut für Pharmakologie, Universitätsklinikum Benjamin Franklin, Freie Universität Berlin, Thielallee 69-73, Berlin 14195, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Grimm
authors.forename: Robert
authors.initials: R
authors.lastname: Kraft
authors.forename: Sophie
authors.initials: S
authors.lastname: Sauerbruch
authors.forename: Günter
authors.initials: G
authors.lastname: Schultz
authors.forename: Christian
authors.initials: C
authors.lastname: Harteneck
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry* / Q000378:metabolism*; D002412:Cations; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002586:Cesium / Q000494:pharmacology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D006706:Homeostasis; D006801:Humans; D007473:Ion Channels / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins; D018408:Patch-Clamp Techniques; D010957:Plasmids / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013050:Spectrometry, Fluorescence; D050053:TRPM Cation Channels; D014018:Tissue Distribution; D014162:Transfection
chemical_list: D015220:Calcium Channels; D002412:Cations; D018076:DNA, Complementary; D007473:Ion Channels; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D050053:TRPM Cation Channels; C492059:TRPM1 protein, human; C475667:TRPM3 protein, human; D002586:Cesium; D008345:Manganese; D002118:Calcium