Plasma Membrane Voltage-dependent Anion Channel Mediates Antiestrogen-activated Maxi Cl– Currents in C1300 Neuroblastoma Cells

Abstract

The cell membrane large conductance voltagedependent chloride channel (Maxi Cl ؊ channel) has been recorded in different cell types following excision of membrane patches or stimulation by antiestrogens under whole-cell recording conditions. However, both its molecular nature and relevance to cell physiology await elucidation. Its electrophysiological properties resemble those of the voltage-dependent anion channel (VDAC) of the outer mitochondrial membrane. This observation has led to the controversial hypothesis that VDAC could be the molecular correlate of the plasma membrane Maxi Cl ؊ channel. We have investigated the cellular localization of VDAC and its relationship with the antiestrogen-activated Maxi Cl ؊ current in C1300 neuroblastoma cells. The presence of a plasma membrane VDAC was demonstrated by immunoblotting of membrane fractions with monoclonal antibodies against the VDAC and by reverse transcription-PCR using primers that hybridize to a VDAC sequence coding for an N-terminal leader peptide required for its plasma membrane sorting. Besides, VDAC colocalized with markers of plasma membrane lipid rafts (cholera toxin ␤ subunit) but not caveolin-1. Transfection of C1300 cells with an antisense oligonucleotide directed against the specific membrane leader sequence of VDAC markedly reduced both VDAC immunostaining and antiestrogenactivated Maxi Cl ؊ currents, suggesting that VDAC forms the plasma membrane Maxi Cl ؊ channel or a part thereof.

Opening of plasma membrane voltage-dependent anion channels (VDAC) precedes caspase activation in neuronal apoptosis induced by toxic stimuli

“…Taken together, the electrophysiological data ((1) large conductance of about 400 pS, (2) bell-shaped open probability curve, and (3) Cl À selectivity) suggest that the largeconductance channel in the plasma membrane described here is similar to the VDAC, normally present in the mitochondrial outer membrane. 13 Although there are certain differences between our observations and the reported properties of VDAC, [13][14][15][16][17][18][19] this variability may be ascribed to differences in experimental preparations and conditions. For instance, the difference in the (main state) conductance between cellular preparations and VDACs reconstituted in black lipid bilayer depends on different salt concentrations (140 mM vs 1 M).…”

The maxi-anion channel: a classical channel playing novel roles through an unidentified molecular entity

“…This hypothesis has received a great attention and considered to be an established concept in the field. Consistent with this idea, several groups have indeed reported the presence of VDAC protein in the plasma membrane of various cells [38,49,88,110, [110]. These authors identified an alternative first exon in the murine vdac1 gene that encodes a leader peptide at its N-terminus.…”

“…These biophysical properties are similar to those of the voltage-dependent anion channel (VDAC, also called porin) expressed in the outer membrane of mitochondria [150][151][152]. Therefore, it has been widely held that VDAC located in the plasma membrane (pl-VDAC) is the most likely candidate protein [38,45,46,49,88,110]. This hypothesis has received a great attention and considered to be an established concept in the field.…”

“…In the heart, maxianion channels were described in neonatal cardiac myocytes in primary culture [2,12,34,35] and freshly isolated adult ventricular cardiomyocytes [12]. In the nervous system, the maxi-anion channel activity was detected in embryonic Xenopus spinal neurons [36], demyelinated Xenopus axons [37], in neuroblastoma cell lines [3,[38][39][40][41][42][43][44] and in a hippocampal cell line [45,46]. In glia, maxi-anion channels were found in cultured Schwann cells from 1 to and in inside-out patches (filled circles).…”

ATP release from non-excitable cells

“…Okada has presented evidence that the maxi anion conductance (VDAC-like-VDACL) is a plasma membrane ATP-conductive pore in mammary cancer cells [70] and in macula densa cells [44], and follow-up work shows that this conductance is inhibited by internal arachidonic acid [71]. VDAC is a mitochondrial ATPpermeable membrane pore, but has been suggested also to be present in the plasma membrane as a specific splice variant (pl-VDAC-1) [72]. Interestingly, VADC-1 knockout mouse tissue shows reduced mechanically stimulated ATP release and, vice versa, overexpression of pl-VDAC-1 protein in fibroblasts leads to increased mechanically stimulated ATP release [73].…”