Abstract |
The proapoptotic B-cell lymphoma (Bcl)-2 protein Bcl-x(S) encloses the Bcl-2 homology (BH) domains BH3 and BH4 and triggers apoptosis via the multidomain protein Bak, however, the mechanism remained elusive. For investigating Bcl-x(S) efficacy and pathways, an adenoviral vector was constructed with its cDNA under tetracycline-off control. Bcl-x(S) overexpression resulted in efficient apoptosis induction and caspase activation in melanoma cells. Indicative of mitochondrial apoptosis pathways, Bcl-x(S) translocated to the mitochondria, disrupted the mitochondrial membrane potential and induced release of cytochrome c, apoptosis-inducing factor and second mitochondria-derived activator of caspases. In melanoma cells, Bcl-x(S) resulted in significant Bak activation, and Bak knockdown as well as Bcl-x(L) overexpression abrogated Bcl-x(S)-induced apoptosis, whereas Mcl-1 (myeloid cell leukemia-1) knockdown resulted in a sensitization. With regard to the particular role of voltage-dependent anion channel 2 (VDAC2) for inhibition of Bak, we identified here a notable interaction between Bcl-x(S) and VDAC2 in melanoma cells, which was proven in reciprocal coimmunoprecipitation analyses. On the other hand, Bcl-x(S) showed no direct interaction with Bak, and its binding to VDAC2 appeared as also independent of Bak expression. Suggesting a new proapoptotic mechanism, Bcl-x(S) overexpression resulted in disruption of the VDAC2-Bak interaction leading to release of Bak. Further supporting this pathway, overexpression of VDAC2 strongly decreased apoptosis by Bcl-x(S). New proapoptotic pathways are of principle interest for overcoming apoptosis deficiency of melanoma cells.
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Authors | M Plötz, B Gillissen, A M Hossini, P T Daniel, J Eberle |
Journal | Cell death and differentiation
(Cell Death Differ)
Vol. 19
Issue 12
Pg. 1928-38
(Dec 2012)
ISSN: 1476-5403 [Electronic] England |
PMID | 22705850
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- Myeloid Cell Leukemia Sequence 1 Protein
- Proto-Oncogene Proteins c-bcl-2
- RNA, Small Interfering
- VDAC2 protein, human
- Voltage-Dependent Anion Channel 2
- bcl-2 Homologous Antagonist-Killer Protein
- bcl-X Protein
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Topics |
- Apoptosis
- Cell Line, Tumor
- HCT116 Cells
- Humans
- Melanoma
(metabolism, pathology)
- Myeloid Cell Leukemia Sequence 1 Protein
- Protein Binding
- Proto-Oncogene Proteins c-bcl-2
(antagonists & inhibitors, genetics, metabolism)
- RNA Interference
- RNA, Small Interfering
(metabolism)
- Voltage-Dependent Anion Channel 2
(metabolism)
- bcl-2 Homologous Antagonist-Killer Protein
(antagonists & inhibitors, genetics, metabolism)
- bcl-X Protein
(metabolism)
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