Rapid cytochrome c release, activation of caspases 3, 6, 7 and 8 followed by Bap31 cleavage in HeLa cells treated with photodynamic therapy

FEBS Letters

Hunt, David W.C¹  Jiang, Huijun¹  McManus, Bruce M³  Carthy, Chris M¹  Shore, Gordon C²  Granville, David J¹ 

[1] QLT PhotoTherapeutics Inc., 520 West 6th Avenue, Vancouver, BC V5Z 4H5, Canada;Department of Biochemistry, McIntyre Medical Sciences Building, McGill University, Montreal, Que. H3G 1Y6, Canada;Department of Pathology and Laboratory Medicine, St. Paul's Hospital-University of British Columbia, 1081 Burrard Street, Vancouver, BC V6Z 1Y6, Canada

关键词: Apoptosis;    Photodynamic therapy;    Benzoporphyrin derivative monoacid ring A;    Caspase;    Cytochrome c;    Mitochondrion;   

DOI  :  10.1016/S0014-5793(98)01193-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Photodynamic therapy (PDT) is a clinical approach that utilizes light-activated drugs for the treatment of a variety of pathologic conditions. The initiating events of PDT-induced apoptosis are poorly defined. It has been shown for other pro-apoptotic stimuli that the integral endoplasmic reticulum protein Bap31 is cleaved by caspases 1 and 8, but not by caspase-3. Further, a 20 kDa Bap31 cleavage fragment is generated which can induce apoptosis. In the current report, we sought to determine whether Bap31 cleavage and generation of p20 is an early event in PDT-induced apoptosis. The mitochondrial release of cytochrome c, involvement of caspases 1, 2, 3, 4, 6, 7, 8, and 10 and the status of several known caspase substrates, including Bap31, were evaluated in PDT-treated HeLa cells. Cytochrome c appeared in the cytosol immediately following light activation of the photosensitizer benzoporphyrin derivative monoacid ring A. Activation of caspases 3, 6, 7, and 8 was evident within 1–2 h post PDT. Processing of caspases 1, 2, 4, and 10 was not observed. Cleavage of Bap31 was observed at 2–3 h post PDT. The caspase-3 inhibitor DEVD-fmk blocked caspase-8 and Bap31 cleavage suggesting that caspase-8 and Bap31 processing occur downstream of caspase-3 activation in PDT-induced apoptosis. These results demonstrate that release of mitochondrial cytochrome c into the cytoplasm is a primary event following PDT, preceding caspase activation and cleavage of Bap31. To our knowledge, this is the first example of a chemotherapeutic agent inducing caspase-8 activation and demonstrates that caspase-8 activation can occur after cytochrome c release.

【 授权许可】

Unknown