Voltage-dependent anion channels are dispensable for mitochondrial-dependent cell death

Abstract

Voltage-dependent anion channels (VDACs) have been implicated as essential mediators of mitochondrial-dependent cell death by functioning as a channel-forming unit within the mitochondrial permeability transition (MPT) pore and the target of Bcl-2 family members. Here we report the effects of deletion of the 3 mammalian Vdac genes on mitochondrial-dependent cell death. Mitochondria from Vdac1-, Vdac3-, and Vdac1/Vdac3-null mice exhibited a Ca 2+ and oxidative stress-induced MPT that was indistinguishable from wildtype mitochondria. Similarly, Ca 2+ and oxidative-stress-induced MPT and cell death was unaltered or even exacerbated in fibroblasts lacking VDAC1, VDAC2, VDAC3, VDAC1/3, and VDAC1/2/3. Wildtype and Vdac-deficient mitochondria and cells also exhibited equivalent cytochrome c release, caspase cleavage, and cell death in response to Bax and Bid activation. These results indicate that VDACs are dispensable for both MPT and Bcl-2 family member-driven cell death.Mitochondria are intracellular organelles that mediate high-energy phosphate production, fatty acid metabolism, porphyrin synthesis, ion homeostasis and apoptotic and necrotic cell death. Apoptotic cell death is mediated by both the "extrinsic" pathway; consisting of death receptor signaling constituents, as well as the "intrinsic" pathway; consisting of pro-death Bcl-2 family members functioning at the level of the mitochondria and endoplasmic reticulum (1). Mitochondria are also critically involved in necrotic cell death following Ca 2+ overload, hypoxia, and oxidative damage, leading to swollen or ruptured mitochondria. The MPT pore, a protein complex that spans both the outer and inner mitochondrial membranes, is considered the mediator of this event and has been hypothesized to minimally consist of the VDAC in the outer membrane, the adenine nucleotide translocase (ANT) in the inner membrane, and cyclophilin-D in the matrix (2-4).The VDAC is comprised of a family of evolutionarily conserved ion channels that are the most abundant proteins in the outer mitochondrial membrane. The physiologic function of VDACs is to control the movement of adenine nucleotides, NADH, and other metabolites across the outer membrane (5,6). However, VDACs have also been proposed to possess a pathological function as mediators of mitochondrial-dependent cell death through formation of the permeability pore (7,8). In addition, VDACs have been proposed to be essential binding partners for pro-apoptotic Bcl-2 family members (9-12), combining to form protein-permeable Here we assessed whether MPT was altered in Vdac1-, Vdac3-, and Vdac1/Vdac3-null mice. Western blotting of cardiac lysates from these mice showed the complete lack of the respective VDAC protein in each line without compensatory alterations in the other VDAC isoforms (Fig. 1a). There were also no significant changes in ANT and cyclophilin D, two other putative components of the MPT pore (Fig. 1a). Cardiac mitochondria isolated from wildtype, Vdac1-, Vdac3-, and Vdac1/Vdac3-null mice were assessed for...

Anoikis: an emerging hallmark in health and diseases

“…An adjuvant role of the voltage-dependent anion channels in membrane permeabilization has also been reported [9,10]. Disruption of OMM leads to the release of cytochrome c, which forms the 'apoptosome' with caspase-9 and the apoptosis protease activating factor (APAF).…”

Multiple Pathways to the Same End: Mechanisms of Myonuclear Apoptosis in Sarcopenia of Aging

“…This finding underlines the major role postulated for CyPD in the formation of the mPTP, and suggests a higher susceptibility to mPTP opening at an older age. Indeed, it was demonstrated that mPTP formation and apoptotic cell death could still occur in the absence of either ANT [57] or VDAC [58]. In contrast, overexpression of CyPD induced mitochondrial swelling and spontaneous cardiac apoptosis, whereas mice lacking cardiac CyPD were protected from ischemia/reperfusion-induced cell death [59].…”

Mitochondria and aging: A role for the mitochondrial transition pore?

“…Many proteins were thought to form the core of the pore across the mitochondrial membrane but they have been successively ruled out by genetic modulation. This is the case for the voltage‐dependent anion channel (VDAC) and the translocator protein (TSPO) in the outer membrane (Baines, Kaiser, Sheiko, Craigen, & Molkentin, 2007; Kokoszka et al., 2004). Recent data propose a role for ATP synthase as the major component of a multiproteic complex (Bernardi, Rasola, Forte, & Lippe, 2015).…”