title: Distinct pharmacological and molecular properties of the acid-sensitive outwardly rectifying (ASOR) anion channel from those of the volume-sensitive outwardly rectifying (VSOR) anion channel.
abstract: Expressed by many cell types, acid-sensitive outwardly rectifying (ASOR) anion channels are known to be activated by extracellular acidification and involved in acidotoxic necrotic cell death. In contrast, ubiquitously expressed volume-sensitive outwardly rectifying (VSOR) anion channels are activated by osmotic cell swelling and involved in cell volume regulation and apoptotic cell death. Distinct inhibitors to distinguish ASOR from VSOR anion channels have not been identified. Although leucine-rich repeats containing 8A (LRRC8A) was recently found to be an essential component of VSOR anion channels, the possibility of an LRRC8 family member serving as a component of ASOR anion channels has not been examined. In this study, we explored the effects of 12 known VSOR channel inhibitors and small interfering RNA (siRNA)-mediated knockdown of LRRC8 family members on ASOR and VSOR currents in HeLa cells. Among these inhibitors, eight putative VSOR blockers, including 4-(2-butyl-6,7-dichlor-2-cyclopentylindan-1-on-5-yl) oxobutyric acid (DCPIB) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), were totally ineffective at blocking ASOR channel activity, whereas suramin, R-(+)-[(2-n-butyl-6,7-dichloro-2-cyclopentyl-2,3-dihydro-1-oxo-1H-inden-5-yl)oxy] acetic acid (DIOA), arachidonic acid, and niflumic acid were found to be effective ASOR anion channel antagonists. In addition, gene-silencing studies showed that no LRRC8 family members are essentially involved in ASOR anion channel activity, whereas LRRC8A is involved in VSOR anion channel activity in HeLa cells.
authors.affiliation: Japan Society for the Promotion of Science, Chiyoda-ku, Tokyo, 102-0083, Japan.|Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, 817-0180, Japan.|National Institute for Physiological Sciences, National Institutes of National Sciences, Okazaki, 444-8787, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Sato-Numata
authors.affiliation: Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, 817-0180, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Numata
authors.affiliation: Department of Physiology, School of Medicine, Fukuoka University, Fukuoka, 817-0180, Japan.
authors.forename: Ryuji
authors.initials: R
authors.lastname: Inoue
authors.affiliation: National Institute for Physiological Sciences, National Institutes of National Sciences, Okazaki, 444-8787, Japan. okada@soken.ac.jp.|SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa, 240-0193, Japan. okada@soken.ac.jp.
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Okada
mesh_terms: D000838:Anions / Q000378:metabolism; D016718:Arachidonic Acid / Q000494:pharmacology; D048429:Cell Size; D003517:Cyclopentanes / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007189:Indans / Q000494:pharmacology; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D049990:Membrane Transport Modulators / Q000494:pharmacology; D009544:Niflumic Acid / Q000494:pharmacology; D009579:Nitrobenzoates / Q000494:pharmacology
chemical_list: C443139:4-(2-butyl-6,7-dichlor-2-cyclopentyl-indan-1-one-5-yl)oxybutyric acid; D000838:Anions; D003517:Cyclopentanes; D007189:Indans; D007473:Ion Channels; C485976:LRRC8A protein, human; D008565:Membrane Proteins; D049990:Membrane Transport Modulators; D009579:Nitrobenzoates; C085057:4-nitro-2-(3-phenylpropylamino)benzoate; D016718:Arachidonic Acid; D009544:Niflumic Acid
keywords: ASOR; Anion channel blocker; Chloride channel; LRRC8 family; VSOR