title: Single-channel properties of a rat brain endoplasmic reticulum anion channel.
abstract: Many intracellular membranes contain ion channels, although their physiological roles are often poorly understood. In this study we incorporated single anion channels colocalized with rat brain endoplasmic reticulum (ER) ryanodine-sensitive Ca(2+)-release channels into planar lipid bilayers. The channels opened in bursts, with more activity at negative (cytoplasm-ER lumen) membrane potentials, and they occupied four open conductance levels with frequencies well described by the binomial equation. The probability of a protomer being open decreased from approximately 0.7 at -40 mV to approximately 0.2 at +40 mV, and the channels selected between different anions in the order PSCN > PNO3 > PBr > PCl > PF. They were also permeant to cations, including the large cation Tris+ (PTris/PCl = 0.16). Their conductance saturated at 170 pS in choline Cl. The channels were inactivated by 15 microM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and blocked with low affinity (KD of 1-100 microM) by anthracene-9-carboxylic acid, ethacrynic acid, frusemide (furosemide), HEPES, the indanyloxyacetic acid derivative IAA-94, 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB), and Zn2+. Unlike protein translocation pores, the channels were unaffected by high salt concentrations or puromycin. They may regulate ER Ca2+ release, or be channel components en route to their final cellular destinations. Alternatively, they may contribute to the fusion machinery involved in intracellular membrane trafficking.
authors.affiliation: Department of Biochemistry, University of Edinburgh, Scotland, United Kingdom.
authors.forename: A G
authors.initials: AG
authors.lastname: Clark
authors.forename: D
authors.initials: D
authors.lastname: Murray
authors.forename: R H
authors.initials: RH
authors.lastname: Ashley
mesh_terms: D000818:Animals; D000838:Anions; D002540:Cerebral Cortex / Q000502:physiology*; D002794:Choline / Q000494:pharmacology; D004553:Electric Conductivity; D004721:Endoplasmic Reticulum / Q000502:physiology*; D005260:Female; D007425:Intracellular Membranes / Q000502:physiology; D015640:Ion Channel Gating / Q000502:physiology*; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008051:Lipid Bilayers; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008861:Microsomes / Q000502:physiology*; D008962:Models, Theoretical; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000838:Anions; D007473:Ion Channels; D008051:Lipid Bilayers; D002794:Choline