Figure 8

Figure 8. Restoration of SR-mitochondria Ca²⁺ transfer in permeabilized HL-1 cardiomyocytes. (A) Knockdown of the endogenous mVDAC2 in HL-1 cells significantly reduced SR-mitochondria Ca²⁺ transfer after addition of caffeine (arrowhead) from ΔF/F₀ = 0.18 ± 0.01 (n = 84) to 0.12 ± 0.01 (n = 83) while a scrambled siRNA control did not affect Ca²⁺ transfer (0.20 ± 0.02, n = 21). (B) Wild-type zVDAC2 restored mitochondrial Ca²⁺ uptake to 0.27 ± 0.02 (n = 36), well above mVDAC2 knockdown cells. Overexpression of zVDAC2^E73Q restored mitochondrial Ca²⁺ uptake to only 0.18 ± 0.02 (n = 39), which is significantly lower compared to wild-type zVDAC2. (C) Conversely, zVDAC3 did not restore mitochondrial Ca²⁺ uptake in mVDAC2 knockdown cells (0.12 ± 0.01, n = 54), while VDAC3^Q73E restored mitochondrial Ca²⁺ uptake to ΔF/F₀ = 0.20 ± 0.02, (n = 50). Arrowheads indicate injection of 10 mM caffeine. Statistical analysis was performed using Kruskal-Wallis test with Dunn’s post-hoc test.