title: Inhibition of ClC-2 chloride channels by a peptide component or components of scorpion venom.
abstract: ClC chloride channels play essential roles in membrane excitability and maintenance of osmotic balance. Despite the recent crystallization of two bacterial ClC-like proteins, the gating mechanism for these channels remains unclear. In this study we tested scorpion venom for the presence of novel peptide inhibitors of ClC channels, which might be useful tools for dissecting the mechanisms underlying ClC channel gating. Recently, it has been shown that a peptide component of venom from the scorpion L. quinquestriatus hebraeus inhibits the CFTR chloride channel from the intracellular side. Using two-electrode voltage clamp we studied the effect of scorpion venom on ClC-0, -1, and -2, and found both dose- and voltage-dependent inhibition only of ClC-2. Comparison of voltage-dependence of inhibition by venom to that of known pore blockers revealed opposite voltage dependencies, suggesting different mechanisms of inhibition. Kinetic data show that venom induced slower activation kinetics compared to pre-venom records, suggesting that the active component(s) of venom may function as a gating modifier at ClC-2. Trypsinization abolished the inhibitory activity of venom, suggesting that the component(s) of scorpion venom that inhibits ClC-2 is a peptide.
authors.affiliation: School of Biology, Georgia Institute of Technology, 310 Ferst Drive, Atlanta, Georgia 30332-0230, USA.
authors.forename: C H
authors.initials: CH
authors.lastname: Thompson
authors.forename: D M
authors.initials: DM
authors.lastname: Fields
authors.forename: P R
authors.initials: PR
authors.lastname: Olivetti
authors.forename: M D
authors.initials: MD
authors.lastname: Fuller
authors.forename: Z R
authors.initials: ZR
authors.lastname: Zhang
authors.forename: J
authors.initials: J
authors.lastname: Kubanek
authors.forename: N A
authors.initials: NA
authors.lastname: McCarty
mesh_terms: D000818:Animals; D000090007:CLC-2 Chloride Channels; D002478:Cells, Cultured; D018118:Chloride Channels / Q000037:antagonists & inhibitors* / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010455:Peptides / Q000737:chemistry / Q000502:physiology*; D011817:Rabbits; D012604:Scorpion Venoms / Q000737:chemistry / Q000494:pharmacology*; D012605:Scorpions / Q000737:chemistry / Q000502:physiology; D014981:Xenopus
chemical_list: D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D010455:Peptides; D012604:Scorpion Venoms; D019005:Cystic Fibrosis Transmembrane Conductance Regulator