VDAC1 selectively transfers apoptotic Ca2+ signals to mitochondria

Voltage-dependent anion channels (VDACs) are expressed in three isoforms, with common channeling properties and different roles in cell survival. We show that VDAC1 silencing potentiates apoptotic challenges, whereas VDAC2 has the opposite effect. Although all three VDAC isoforms are equivalent in allowing mitochondrial Ca2+ loading upon agonist stimulation, VDAC1 silencing selectively impairs the transfer of the low-amplitude apoptotic Ca2+ signals. Co-immunoprecipitation experiments show that VDAC1, but not VDAC2 and VDAC3, forms complexes with IP3 receptors, an interaction that is further strengthened by apoptotic stimuli. These data highlight a non-redundant molecular route for transferring Ca2+ signals to mitochondria in apoptosis.