VDAC3 gating is activated by suppression of disulfide-bond formation between the N-terminal region and the bottom of the pore

Abstract

The voltage-dependent anion channels (VDACs), VDAC1, VDAC2, and VDAC3, are pore-forming proteins that control metabolite flux between mitochondria and cytoplasm. VDAC1 and VDAC2 have voltage-dependent gating activity, whereas VDAC3 is thought to have weak activity. The aim of this study was to analyze the channel properties of all three human VDAC isoforms and to clarify the channel function of VDAC3. Bacterially expressed recombinant human VDAC proteins were reconstituted into artificial planar lipid bilayers and their gating activities were evaluated. VDAC1 and VDAC2 had typical voltage-dependent gating activity, whereas the gating of VDAC3 was weak, as reported. However, gating of VDAC3 was evoked by dithiothreitol (DTT) and S-nitrosoglutathione (GSNO), which are thought to suppress disulfide-bond formation. Several cysteine mutants of VDAC3 also exhibited typical voltage-gating. Our results indicate that channel gating was induced by reduction of a disulfide-bond linking the N-terminal region to the bottom of the pore. Thus, channel gating of VDAC3 might be controlled by redox sensing under physiological conditions.

The N-terminus of VDAC: Structure, mutational analysis, and a potential role in regulating barrel shape

“…In mammals, the three VDAC paralogues encode proteins of similar primary sequence (67-75% identity), and hVDAC1 [16] and hVDAC2 [17] fold into very similar 19-ß-strand barrels. [33].…”

“…hVDAC3 contains 6 cysteines. Two cysteine residues in the N-terminus (C2, C8) are able to cause pore restriction through disulphide bond formation with C122, leading the authors to present a model in which these bonds trap the N-terminus in the barrel, generating an ungated, low conductance pore depending on the redox state [31], implying that the conductance of hVDAC3 is responsive to redox state [33]. [62].…”

“…Models for gating of mammalian VDAC2 and VDAC3 are complicated by the presence of multiple cysteines in these proteins. VDAC3, which is predicted by MD simulations to exist in elliptical substates [59], forms very small, ungated pores [31], unless disulphide bond formation is prevented by treatment with a reducing agents [33]. hVDAC3 contains 6 cysteines.…”

VDAC as a Potential Target in Huntingtons Disease Therapy: The State of the Art

“…Moreover, the available data suggest that VDAC isoforms may be differently controlled by oxidative modification of cysteine residues. For example it has been shown for human VDAC3 that the cysteine residue modification might be crucial for its channel activity under physiological conditions [60].…”

“…Moreover, the available data suggest that VDAC isoforms may be differently controlled by oxidative modification of cysteine residues. For example it has been shown for human VDAC3 that the cysteine residue modification might be crucial for its channel activity under physiological conditions [60].The channel properties of VDAC were first reported in 1976 [61] and since that time have been extensively studied [33,36,62]. In a brief, VDAC reconstituted into artificial membranes displays only one fully (Figure 2).…”