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Essential role of voltage-dependent anion channel in various forms of apoptosis in mammalian cells.

Shimizu S, Matsuoka Y, Shinohara Y, Yoneda Y, Tsujimoto Y - J. Cell Biol. (2001)

Bottom Line: Through direct interaction with the voltage-dependent anion channel (VDAC), proapoptotic members of the Bcl-2 family such as Bax and Bak induce apoptogenic cytochrome c release in isolated mitochondria, whereas BH3-only proteins such as Bid and Bik do not directly target the VDAC to induce cytochrome c release.When microinjected into cells, these anti-VDAC antibodies, but not control antibodies, also prevented Bax-induced cytochrome c release and apoptosis, whereas the antibodies did not prevent Bid-induced apoptosis, indicating that the VDAC is essential for Bax-induced, but not Bid-induced, apoptogenic mitochondrial changes and apoptotic cell death.Taken together, our data provide evidence that the VDAC plays an essential role in apoptogenic cytochrome c release and apoptosis in mammalian cells.

View Article: PubMed Central - PubMed

Affiliation: Osaka University Graduate School of Medicine, Biomedical Research Center, Department of Medical Genetics, Osaka 565-0871, Japan.

ABSTRACT
Through direct interaction with the voltage-dependent anion channel (VDAC), proapoptotic members of the Bcl-2 family such as Bax and Bak induce apoptogenic cytochrome c release in isolated mitochondria, whereas BH3-only proteins such as Bid and Bik do not directly target the VDAC to induce cytochrome c release. To investigate the biological significance of the VDAC for apoptosis in mammalian cells, we produced two kinds of anti-VDAC antibodies that inhibited VDAC activity. In isolated mitochondria, these antibodies prevented Bax-induced cytochrome c release and loss of the mitochondrial membrane potential (Deltapsi), but not Bid-induced cytochrome c release. When microinjected into cells, these anti-VDAC antibodies, but not control antibodies, also prevented Bax-induced cytochrome c release and apoptosis, whereas the antibodies did not prevent Bid-induced apoptosis, indicating that the VDAC is essential for Bax-induced, but not Bid-induced, apoptogenic mitochondrial changes and apoptotic cell death. In addition, microinjection of these anti-VDAC antibodies significantly inhibited etoposide-, paclitaxel-, and staurosporine-induced apoptosis. Furthermore, we used these antibodies to show that Bax- and Bak-induced lysis of red blood cells was also mediated by the VDAC on plasma membrane. Taken together, our data provide evidence that the VDAC plays an essential role in apoptogenic cytochrome c release and apoptosis in mammalian cells.

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Functional interaction of Bcl-2/Bcl-xL and Bax/Bak, but not Bid/Bik, with the VDAC. Bax/Bak directly opens the VDAC to induce cytochrome c release, while Bcl-2/Bcl-xL closes this channel. Bid/Bik does not interact with the VDAC, but probably has the ability to open an unidentified channel(s) that is involved in cytochrome c release. The VDAC is a component of the PT pore, which contains ANT and cyclophilin D (CyD) and would explain the concomitant induction of Δψ loss by Bax/Bak and inhibition of Bax/Bak-induced cytochrome c and Δψ loss by PT inhibitors. Bcl-2/Bcl-xL inhibits Bid/Bik-induced cytochrome c release, probably through heterodimerization with Bid/Bik or by closing an unidentified channel(s).
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Figure 8: Functional interaction of Bcl-2/Bcl-xL and Bax/Bak, but not Bid/Bik, with the VDAC. Bax/Bak directly opens the VDAC to induce cytochrome c release, while Bcl-2/Bcl-xL closes this channel. Bid/Bik does not interact with the VDAC, but probably has the ability to open an unidentified channel(s) that is involved in cytochrome c release. The VDAC is a component of the PT pore, which contains ANT and cyclophilin D (CyD) and would explain the concomitant induction of Δψ loss by Bax/Bak and inhibition of Bax/Bak-induced cytochrome c and Δψ loss by PT inhibitors. Bcl-2/Bcl-xL inhibits Bid/Bik-induced cytochrome c release, probably through heterodimerization with Bid/Bik or by closing an unidentified channel(s).

Mentions: It has previously been suggested that Bax induces cytochrome c release via two different mechanisms in isolated mitochondria: a mechanism that is accompanied by Δψ loss and is blocked by PT inhibitors such as cyclosporine A (Jürgensmeier et al. 1998; Marzo et al. 1998; Narita et al. 1998) or a mechanism that is not accompanied by Δψ loss and is resistant to PT inhibitors (Eskes et al. 1998; Finucane et al. 1999; Kluck et al. 1999), although it seems likely that the former mechanism is more physiologically relevant because Bax induces cytochrome c release together with Δψ loss in mammalian cells (Xiang et al. 1996; Marzo et al. 1998; Pastorino et al. 1998; Shimizu and Tsujimoto 2000; our unpublished observations). In the present study, our neutralizing anti-VDAC antibodies inhibited Bax-induced cytochrome c release that was largely PT inhibitor-sensitive. Importantly, the same antibodies inhibited Bax-induced cytochrome c release in the absence of Ca2+, that was PT inhibitor resistant. Thus, irrespective of PT dependence, Bax-induced cytochrome c release always requires the VDAC (Fig. 8). Accordingly, the likely scenario is that Bax triggers VDAC opening and cytochrome c release, leading to opening of inner membrane channel(s) such as ANTs via a mutual interaction that results in Δψ loss and the PT, which might subsequently induce another phase of cytochrome c release.


Essential role of voltage-dependent anion channel in various forms of apoptosis in mammalian cells.

Shimizu S, Matsuoka Y, Shinohara Y, Yoneda Y, Tsujimoto Y - J. Cell Biol. (2001)

Functional interaction of Bcl-2/Bcl-xL and Bax/Bak, but not Bid/Bik, with the VDAC. Bax/Bak directly opens the VDAC to induce cytochrome c release, while Bcl-2/Bcl-xL closes this channel. Bid/Bik does not interact with the VDAC, but probably has the ability to open an unidentified channel(s) that is involved in cytochrome c release. The VDAC is a component of the PT pore, which contains ANT and cyclophilin D (CyD) and would explain the concomitant induction of Δψ loss by Bax/Bak and inhibition of Bax/Bak-induced cytochrome c and Δψ loss by PT inhibitors. Bcl-2/Bcl-xL inhibits Bid/Bik-induced cytochrome c release, probably through heterodimerization with Bid/Bik or by closing an unidentified channel(s).
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Related In: Results  -  Collection

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Figure 8: Functional interaction of Bcl-2/Bcl-xL and Bax/Bak, but not Bid/Bik, with the VDAC. Bax/Bak directly opens the VDAC to induce cytochrome c release, while Bcl-2/Bcl-xL closes this channel. Bid/Bik does not interact with the VDAC, but probably has the ability to open an unidentified channel(s) that is involved in cytochrome c release. The VDAC is a component of the PT pore, which contains ANT and cyclophilin D (CyD) and would explain the concomitant induction of Δψ loss by Bax/Bak and inhibition of Bax/Bak-induced cytochrome c and Δψ loss by PT inhibitors. Bcl-2/Bcl-xL inhibits Bid/Bik-induced cytochrome c release, probably through heterodimerization with Bid/Bik or by closing an unidentified channel(s).
Mentions: It has previously been suggested that Bax induces cytochrome c release via two different mechanisms in isolated mitochondria: a mechanism that is accompanied by Δψ loss and is blocked by PT inhibitors such as cyclosporine A (Jürgensmeier et al. 1998; Marzo et al. 1998; Narita et al. 1998) or a mechanism that is not accompanied by Δψ loss and is resistant to PT inhibitors (Eskes et al. 1998; Finucane et al. 1999; Kluck et al. 1999), although it seems likely that the former mechanism is more physiologically relevant because Bax induces cytochrome c release together with Δψ loss in mammalian cells (Xiang et al. 1996; Marzo et al. 1998; Pastorino et al. 1998; Shimizu and Tsujimoto 2000; our unpublished observations). In the present study, our neutralizing anti-VDAC antibodies inhibited Bax-induced cytochrome c release that was largely PT inhibitor-sensitive. Importantly, the same antibodies inhibited Bax-induced cytochrome c release in the absence of Ca2+, that was PT inhibitor resistant. Thus, irrespective of PT dependence, Bax-induced cytochrome c release always requires the VDAC (Fig. 8). Accordingly, the likely scenario is that Bax triggers VDAC opening and cytochrome c release, leading to opening of inner membrane channel(s) such as ANTs via a mutual interaction that results in Δψ loss and the PT, which might subsequently induce another phase of cytochrome c release.

Bottom Line: Through direct interaction with the voltage-dependent anion channel (VDAC), proapoptotic members of the Bcl-2 family such as Bax and Bak induce apoptogenic cytochrome c release in isolated mitochondria, whereas BH3-only proteins such as Bid and Bik do not directly target the VDAC to induce cytochrome c release.When microinjected into cells, these anti-VDAC antibodies, but not control antibodies, also prevented Bax-induced cytochrome c release and apoptosis, whereas the antibodies did not prevent Bid-induced apoptosis, indicating that the VDAC is essential for Bax-induced, but not Bid-induced, apoptogenic mitochondrial changes and apoptotic cell death.Taken together, our data provide evidence that the VDAC plays an essential role in apoptogenic cytochrome c release and apoptosis in mammalian cells.

View Article: PubMed Central - PubMed

Affiliation: Osaka University Graduate School of Medicine, Biomedical Research Center, Department of Medical Genetics, Osaka 565-0871, Japan.

ABSTRACT
Through direct interaction with the voltage-dependent anion channel (VDAC), proapoptotic members of the Bcl-2 family such as Bax and Bak induce apoptogenic cytochrome c release in isolated mitochondria, whereas BH3-only proteins such as Bid and Bik do not directly target the VDAC to induce cytochrome c release. To investigate the biological significance of the VDAC for apoptosis in mammalian cells, we produced two kinds of anti-VDAC antibodies that inhibited VDAC activity. In isolated mitochondria, these antibodies prevented Bax-induced cytochrome c release and loss of the mitochondrial membrane potential (Deltapsi), but not Bid-induced cytochrome c release. When microinjected into cells, these anti-VDAC antibodies, but not control antibodies, also prevented Bax-induced cytochrome c release and apoptosis, whereas the antibodies did not prevent Bid-induced apoptosis, indicating that the VDAC is essential for Bax-induced, but not Bid-induced, apoptogenic mitochondrial changes and apoptotic cell death. In addition, microinjection of these anti-VDAC antibodies significantly inhibited etoposide-, paclitaxel-, and staurosporine-induced apoptosis. Furthermore, we used these antibodies to show that Bax- and Bak-induced lysis of red blood cells was also mediated by the VDAC on plasma membrane. Taken together, our data provide evidence that the VDAC plays an essential role in apoptogenic cytochrome c release and apoptosis in mammalian cells.

Show MeSH
Related in: MedlinePlus