Apoptosis is regulated by the VDAC1 N-terminal region and by VDAC oligomerization: release of cytochrome c, AIF and Smac/Diablo.
Mitochondria, central to basic life functions due to their generation of cellular energy, also serve as the venue for cellular decisions leading to apoptosis. A key protein in mitochondria-mediated apoptosis is the voltage-dependent anion channel (VDAC), which also mediates the exchange of metabolites and energy between the cytosol and the mitochondria. In this study, the functions played by the N-terminal region of VDAC1 and by VDAC1 oligomerization in the release of cytochrome c, Smac/Diablo and apoptosis-inducing factor (AIF) and subsequent apoptosis were addressed. We demonstrate that cells undergoing apoptosis induced by STS or cisplatin and expressing N-terminally truncated VDAC1 do not release cytochrome c, Smac/Diablo or AIF. Ruthenium red (RuR), AzRu, DIDS and hexokinase-I (HK-I), all known to interact with VDAC, inhibited the release of cytochrome c, Smac/Diablo and AIF, while RuR-mediated inhibition was not observed in cells expressing RuR-insensitive E72Q-VDAC1. These findings suggest that VDAC1 is involved in the release of not only cytochrome c but also of Smac/Diablo and AIF. We also demonstrate that apoptosis induction is associated with VDAC oligomerization, as revealed by chemical cross-linking and monitoring in living cells using Bioluminescence Resonance Energy Transfer. Apoptosis induction by STS, H2O2 or selenite augmented the formation of VDAC oligomers several fold. The results show VDAC1 to be a component of the apoptosis machinery and offer new insight into the functions of VDAC1 oligomerization in apoptosis and of the VDAC1 N-terminal domain in the release of apoptogenic proteins as well as into regulation of VDAC by anti-apoptotic proteins, such as HK and Bcl2.
Shoshan-Barmatz
Varda
V
Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel.
Keinan
Nurit
N
Abu-Hamad
Salah
S
Tyomkin
Dalia
D
Aram
Lior
L
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D051017:Apoptosis Regulatory Proteins; D001483:Base Sequence; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D051379:Mice; D024101:Mitochondrial Proteins / Q000378:metabolism; D008954:Models, Biological; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D050995:Voltage-Dependent Anion Channel 1 / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
C494829:AIFM1 protein, human; D051033:Apoptosis Inducing Factor; D051017:Apoptosis Regulatory Proteins; C412403:DIABLO protein, human; D017931:DNA Primers; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C494762:VDAC1 protein, human; C494763:Vdac1 protein, mouse; D045304:Cytochromes c; D050995:Voltage-Dependent Anion Channel 1