title: Molecular determinant of sensing extracellular pH in classical transient receptor potential channel 5.
abstract: The classical transient receptor potential channel 5 (TRPC5) is a molecular candidate for nonselective cation channel (NSCC) activated by muscarinic receptor stimulation whereas extracellular pH inhibits or enhances NSCC activated by muscarinic receptor stimulation depending on extracellular cation compositions in native tissues. We investigated the effect of extracellular pH on TRPC5 and determined amino acid residues responsible for sensing extracellular pH. Extracellular acidosis inhibits TRPC5 with pKa of 6.24. Under 50 mM intracellular HEPES buffer condition, extracellular acidosis inhibits TRPC5 with pKa of 5.40. We changed titratable amino acids (C, D, E, H, K, R, Y) to nontitratable amino acids (A, N, Q, N, N, N, F) within pore region between transmembrane segments 5 and 6 in order to determine the residues sensing extracellular pH. Glutamate (at the position 543, 595, and 598), aspartate (at the position 548) and lysine (at the position 554) were responsible for sensing extracellular pH. The effect of extracellular pH in TRPC5 was also dependent on the composition of extracellular monovalent cations. In conclusion, TRPC5 is a molecular candidate for NSCC activated by muscarinic receptor stimulation, has glutamate amino acid residues responsible for sensing extracellular pH, and has a unique gating property depending on the composition of extracellular monovalent cations.
authors.affiliation: Center for Bio-Artificial Muscle and Department of Physiology, Seoul National University College of Medicine, 28 Yongon-Dong, Chongno-Gu, Seoul 110-799, Republic of Korea.
authors.forename: Min Ji
authors.initials: MJ
authors.lastname: Kim
authors.forename: Jae-Pyo
authors.initials: JP
authors.lastname: Jeon
authors.forename: Hyun Jin
authors.initials: HJ
authors.lastname: Kim
authors.forename: Byung Joo
authors.initials: BJ
authors.lastname: Kim
authors.forename: Young Mee
authors.initials: YM
authors.lastname: Lee
authors.forename: Han
authors.initials: H
authors.lastname: Choe
authors.forename: Ju-Hong
authors.initials: JH
authors.lastname: Jeon
authors.forename: Seon Jeong
authors.initials: SJ
authors.lastname: Kim
authors.forename: Insuk
authors.initials: I
authors.lastname: So
mesh_terms: D002460:Cell Line; D045604:Extracellular Fluid / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000502:physiology*; D007668:Kidney / Q000502:physiology*; D015336:Molecular Probe Techniques; D050052:TRPC Cation Channels / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D050052:TRPC Cation Channels; C491780:TRPC5 protein, human