FIGURE 4.
VDAC 1, 2, and 3 isoforms have different sensitivity to blockade by tubulin. Double knockdowns of VDAC isoforms were performed in all possible combinations in HepG2 cells, and the remaining VDAC isoform was isolated and inserted into lipid bilayers. In A, normalized average conductance, G/Gmax, is plotted versus applied voltage for the three VDAC isoforms in the absence of tubulin. In B, tubulin (10 nm) was added to both sides of the membrane, which increased VDAC voltage-induced closure and decreased minimum conductance at > ± 40 mV for VDAC1 and 2 but did not affect VDAC3. In C, normalized conductance at −50 mV was plotted for all VDAC isoforms at tubulin concentrations of 10 nm and 50 nm, as indicated. *, p < 0.001 compared with no tubulin from 3–6 experiments for each group.