Figure 3. Calpain inhibitor I and siRNA against calpain 1 inhibit VDAC1-ΔC formation.

(A) HeLa cells were incubated for 24 h in serum-free medium with or without 150 μM CoCl₂ and in the absence or presence of the indicated concentration of calpain inhibitor I (CI). VDAC1-ΔC levels were analyzed by immunoblotting (see C). (B) Immunoblotting of cells incubated in 1% O₂ in the absence or presence of CI. (C) Quantification of VDAC1-ΔC levels from (A, full circles) and (B, empty circles) is presented, relative to β-actin levels. (D) HeLa cells were treated under hypoxic conditions (1% O₂) for 48 h with 50 or 100 nM of si-RNA against calpain-1 (si-Calp-1) or calpain-2 (si-Calp-2) and analyzed for VDAC1, VDAC1(ΔC), calpain-1 and calpin-2 levels by immunoblotting using specific antibodies. (E) Quantitative analysis of VDAC1 levels from three similar experiments as in (D). (F) Quantitative analysis of calpain-1 (black bars) and calpain-2 (grey bars) levels. The results are the mean ± SE from five similar experiments as in (A). ^*P ≤ .0.01, ^**P ≤ .001; ^***P ≤ .0001.