title: TRPC channel activation by extracellular thioredoxin.
abstract: Mammalian homologues of Drosophila melanogaster transient receptor potential (TRP) are a large family of multimeric cation channels that act, or putatively act, as sensors of one or more chemical factor. Major research objectives are the identification of endogenous activators and the determination of cellular and tissue functions of these channels. Here we show the activation of TRPC5 (canonical TRP 5) homomultimeric and TRPC5-TRPC1 heteromultimeric channels by extracellular reduced thioredoxin, which acts by breaking a disulphide bridge in the predicted extracellular loop adjacent to the ion-selectivity filter of TRPC5. Thioredoxin is an endogenous redox protein with established intracellular functions, but it is also secreted and its extracellular targets are largely unknown. Particularly high extracellular concentrations of thioredoxin are apparent in rheumatoid arthritis, an inflammatory joint disease that disables millions of people worldwide. We show that TRPC5 and TRPC1 are expressed in secretory fibroblast-like synoviocytes from patients with rheumatoid arthritis, that endogenous TRPC5-TRPC1 channels of the cells are activated by reduced thioredoxin, and that blockade of the channels enhances secretory activity and prevents the suppression of secretion by thioredoxin. The data indicate the presence of a previously unrecognized ion-channel activation mechanism that couples extracellular thioredoxin to cell function.
authors.affiliation: Institute of Membrane and Systems Biology, Garstang Building, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Shang-Zhong
authors.initials: SZ
authors.lastname: Xu
authors.forename: Piruthivi
authors.initials: P
authors.lastname: Sukumar
authors.forename: Fanning
authors.initials: F
authors.lastname: Zeng
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Amit
authors.initials: A
authors.lastname: Jairaman
authors.forename: Anne
authors.initials: A
authors.lastname: English
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Naylor
authors.forename: Coziana
authors.initials: C
authors.lastname: Ciurtin
authors.forename: Yasser
authors.initials: Y
authors.lastname: Majeed
authors.forename: Carol J
authors.initials: CJ
authors.lastname: Milligan
authors.forename: Yahya M
authors.initials: YM
authors.lastname: Bahnasi
authors.forename: Eman
authors.initials: E
authors.lastname: Al-Shawaf
authors.forename: Karen E
authors.initials: KE
authors.lastname: Porter
authors.forename: Lin-Hua
authors.initials: LH
authors.lastname: Jiang
authors.forename: Paul
authors.initials: P
authors.lastname: Emery
authors.forename: Asipu
authors.initials: A
authors.lastname: Sivaprasadarao
authors.forename: David J
authors.initials: DJ
authors.lastname: Beech
mesh_terms: D000818:Animals; D001172:Arthritis, Rheumatoid / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D004220:Disulfides / Q000737:chemistry / Q000378:metabolism; D004553:Electric Conductivity; D006801:Humans; D010084:Oxidation-Reduction / Q000187:drug effects; D018408:Patch-Clamp Techniques; D011817:Rabbits; D050052:TRPC Cation Channels / Q000819:agonists* / Q000737:chemistry / Q000378:metabolism*; D013879:Thioredoxins / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D004220:Disulfides; D050052:TRPC Cation Channels; C491780:TRPC5 protein, human; C096351:transient receptor potential cation channel, subfamily C, member 1; D013879:Thioredoxins