Forced expression of survivin-2B abrogates mitotic cells and induces mitochondria-dependent apoptosis by blockade of tubulin polymerization and modulation of Bcl-2, Bax, and survivin.
It has been previously shown that both survivin and the survivin splice variant survivin-2B are localized in mitochondria. Whereas the mechanism involved in blockade of mitochondria-mediated apoptosis by survivin has been extensively studied, the role of survivin-2B in regulation of apoptosis has not been well defined. In the present study, we report that in addition to mitochondria, survivin-2B is also localized in the microtubule organization center (MTOC) and, in contrast to other survivin isoforms (i.e. survivin and survivin-DeltaEx3), behaves as a proapoptotic molecule. We show that forced expression of survivin-2B blocks tubulin polymerization, ablates mitotic cells, and induces mitochondria-dependent apoptosis. The mitochondria-mediated apoptosis induced by survivin-2B was indicated by Smac release from mitochondria, activation of caspases 9 and 3, and loss of mitochondrial potential, while caspase-8 remained inactive. Further analysis of the mechanism for the mitochondria-associated events of apoptosis induced by forced expression of survivin-2B revealed down-regulation of the pro-survival factor Bcl-2 and up-regulation of the pro-apoptotic factor Bax in mitochondria, while the apoptosis-inducing factor (AIF) remains unchanged. Our studies further showed that taxol (paclitaxel) treatment of cancer cells not only up-regulates survivin but also down-regulates survivin-2B and that forced expression of survivin-2B sensitizes cells to taxol-induced cell growth inhibition and cell death, while silencing of endogenous survivin-2B transcripts by survivin-2B-specific siRNA made cells resistant to taxol treatment. These findings advance our current knowledge about survivin-2B and may help to develop novel approaches for cancer treatment.
Ling
Xiang
X
Department of Pharmacology and Therapeutics, Grace Cancer Drug Center, Roswell Park Cancer Institute, Buffalo, New York 14263.
Cheng
Qiuying
Q
Department of Pharmacology and Therapeutics, Grace Cancer Drug Center, Roswell Park Cancer Institute, Buffalo, New York 14263.
Black
Jennifer D
JD
Department of Pharmacology and Therapeutics, Grace Cancer Drug Center, Roswell Park Cancer Institute, Buffalo, New York 14263.
Li
Fengzhi
F
Department of Pharmacology and Therapeutics, Grace Cancer Drug Center, Roswell Park Cancer Institute, Buffalo, New York 14263. Electronic address: fengzhi.li@roswellpark.org.
D017209:Apoptosis; D053181:Caspase 8 / Q000502:physiology; D002460:Cell Line; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins / Q000032:analysis / Q000502:physiology*; D008928:Mitochondria / Q000502:physiology*; D008938:Mitosis; D009363:Neoplasm Proteins / Q000032:analysis / Q000502:physiology*; D017239:Paclitaxel / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis*; D000077022:Survivin; D014404:Tubulin / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000032:analysis*
C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D008869:Microtubule-Associated Proteins; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D000077022:Survivin; D014404:Tubulin; D051028:bcl-2-Associated X Protein; D053181:Caspase 8; D017239:Paclitaxel