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

The cell membrane large conductance voltage-dependent 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 β 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 antiestrogen-activated Maxi Cl– currents, suggesting that VDAC forms the plasma membrane Maxi Cl– channel or a part thereof.