Apoptosis modulatory activities of transiently expressed Bcl-2: Roles in cytochrome c release and Bax regulation

Q. Hou, E. Cymbalyuk, S. C. Hsu, M. Xu, Yi Te Hsu

Research output: Contribution to journalArticlepeer-review

56 Scopus citations


Bcl-2 and Bcl-XL are pro-survival members of the Bcl-2 family. These proteins have been shown to antagonize the pro-apoptotic activity of Bax and promote cell survival through blocking Bax translocation from the cytosol to mitochondria and by preventing the release of cytochrome c. However, it has been recently reported that transiently expressed Bcl-2 unexpectedly leads to significant cell toxicity. To study this intriguing phenomenon, we have carried out further analyses into the properties of transiently expressed Bcl-2. We found that various isoforms of human and different species of Bcl-2 were equally capable of inducing apoptosis. In addition, we discovered that transient expression of Bcl-2, unlike its pro-survival homolog Bcl-X L, can lead to the release of cytochrome c from mitochondria and that the resulting cell death can be inhibited by caspase and calpain inhibitors. Moreover, we have shown that unlike the pro-apoptotic protein Bid, the toxicity associated with the transient expression of Bcl-2 occurs independent of the activity of the endogenous Bax. Finally, we found that in spite of its intrinsic toxicity, transiently expressed Bcl-2 is fully capable of blocking the ectopically expressed Bax from localizing to mitochondria. Taken together, these studies demonstrate that transiently expressed Bcl-2 displays opposing functional properties.

Original languageEnglish (US)
Pages (from-to)617-629
Number of pages13
Issue number6
StatePublished - Dec 2003

All Science Journal Classification (ASJC) codes

  • Pharmacology
  • Pharmaceutical Science
  • Clinical Biochemistry
  • Cell Biology
  • Biochemistry, medical
  • Cancer Research


  • Apoptosis
  • Bax
  • Bcl-2
  • Bcl-X
  • Mitochondria


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