title: Genetic demonstration that the plasma membrane maxianion channel and voltage-dependent anion channels are unrelated proteins.
abstract: The maxianion channel is widely expressed in many cell types, where it fulfills a general physiological function as an ATP-conductive gate for cell-to-cell purinergic signaling. Establishing the molecular identity of this channel is crucial to understanding the mechanisms of regulated ATP release. A mitochondrial porin (voltage-dependent anion channel (VDAC)) located in the plasma membrane has long been considered as the molecule underlying the maxianion channel activity, based upon similarities in the biophysical properties of these two channels and the purported presence of VDAC protein in the plasma membrane. We have deleted each of the three genes encoding the VDAC isoforms individually and collectively and demonstrate that maxianion channel (approximately 400 picosiemens) activity in VDAC-deficient mouse fibroblasts is unaltered. The channel activity is similar in VDAC1/VDAC3-double-deficient cells and in double-deficient cells with the VDAC2 protein depleted by RNA interference. VDAC deletion slightly down-regulated, but never abolished, the swelling-induced ATP release. The lack of correlation between VDAC protein expression and maxianion channel activity strongly argues against the long held hypothesis of plasmalemmal VDAC being the maxianion channel.
authors.affiliation: Department of Cell Physiology, National Institute for Physiological Sciences, School of Life Science, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan. sabirov@nips.ac.jp
authors.forename: Ravshan Z
authors.initials: RZ
authors.lastname: Sabirov
authors.forename: Tatiana
authors.initials: T
authors.lastname: Sheiko
authors.forename: Hongtao
authors.initials: H
authors.lastname: Liu
authors.forename: Defeng
authors.initials: D
authors.lastname: Deng
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Okada
authors.forename: William J
authors.initials: WJ
authors.lastname: Craigen
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D015536:Down-Regulation; D004594:Electrophysiology; D005347:Fibroblasts / Q000378:metabolism; D017353:Gene Deletion; D020868:Gene Silencing; D051379:Mice; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D018272:Porins / Q000737:chemistry; D020033:Protein Isoforms; D034622:RNA Interference; D050995:Voltage-Dependent Anion Channel 1 / Q000235:genetics* / Q000378:metabolism; D050996:Voltage-Dependent Anion Channel 2 / Q000235:genetics* / Q000378:metabolism; D050994:Voltage-Dependent Anion Channels / Q000235:genetics* / Q000378:metabolism
chemical_list: D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D018272:Porins; D020033:Protein Isoforms; C494766:Vdac2 protein, mouse; C480078:Vdac3 protein, mouse; D050996:Voltage-Dependent Anion Channel 2; D050994:Voltage-Dependent Anion Channels; D000255:Adenosine Triphosphate; D050995:Voltage-Dependent Anion Channel 1