Voltage Gating of VDAC Is Regulated by Nonlamellar Lipids of Mitochondrial Membranes

Laboratory of Physical and Structural Biology and National Center for Medical Rehabilitation Research, NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 01/2007; 281(49):37496-506. DOI: 10.1074/jbc.M602548200
Source: PubMed


Evidence is accumulating that lipids play important roles in permeabilization of the mitochondria outer membrane (MOM) at the early stage of apoptosis. Lamellar phosphatidylcholine (PC) and nonlamellar phosphatidylethanolamine (PE) lipids are the major membrane components of the MOM. Cardiolipin (CL), the characteristic lipid from the mitochondrial inner membrane, is another nonlamellar lipid recently shown to play a role in MOM permeabilization. We investigate the effect of these three key lipids on the gating properties of the voltage-dependent anion channel (VDAC), the major channel in MOM. We find that PE induces voltage asymmetry in VDAC current-voltage characteristics by promoting channel closure at cis negative applied potentials. Significant asymmetry is also induced by CL. The observed differences in VDAC behavior in PC and PE membranes cannot be explained by differences in the insertion orientation of VDAC in these membranes. Rather, it is clear that the two nonlamellar lipids affect VDAC gating. Using gramicidin A channels as a tool to probe bilayer mechanics, we show that VDAC channels are much more sensitive to the presence of CL than could be expected from the experiments with gramicidin channels. We suggest that this is due to the preferential insertion of VDAC into CL-rich domains. We propose that the specific lipid composition of the mitochondria outer membrane and/or of contact sites might influence MOM permeability by regulating VDAC gating.

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    • "Although the response of multichannel VDAC conductance to decreasing voltage (channel opening) has been extensively studied (Colombini 1989; Mangan and Colombini 1987; Rostovtseva et al. 2006; Schein et al. 1976; Teijido et al. 2014; Zizi et al. 1995, 1998), as far as we are aware full hysteresis curves have never been published. We therefore studied the conductance of multichannel membranes in response to a voltage ramp (piecewise linear voltage vs. time). "
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    • "After VDAC channels were inserted and their parameters were monitored, tubulin was added to one or both sides of the membrane under constant stirring for 2 min. Current recordings were performed as described previously [49] using an Axopatch 200B amplifier (Axon Instruments, Inc., Foster City, CA) in the voltage clamp mode. Single-channel data were filtered by a low-pass 8-pole Butterworth filter (Model 9002, Frequency Devices, Inc., Haverhill, MA) at 15 kHz and directly saved into the computer memory with a sampling frequency of 50 kHz. "
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