title: Involvement of proapoptotic Bcl-2 family members in parthenolide-induced mitochondrial dysfunction and apoptosis.
abstract: Parthenolide is a sesquiterpene lactone responsible for the bioactivities of Feverfew. Besides its potent anti-inflammatory effect, this compound has recently been reported to induce apoptosis in cancer cells, possibly through mitochondrial dysfunction. In the present study, we attempted to examine parthenolide-mediated cell death signaling pathway by focusing on the involvement of Bcl-2 family members. Using a human colorectal cancer cell line COLO205, we first demonstrated that parthenolide acted through the cell death receptor pathway to activate caspase 8. Following caspase 8 activation, Bid, a proapoptotic Bcl-2 member, was cleaved and this cleavage then triggered Bax conformational changes and Bax translocation from cytosol to mitochondrial membrane. Meanwhile, another proapoptotic protein, Bak, was up-regulated and oligomerized on the mitochondrial membrane. All these alterations were found to be prerequisite for the subsequent release of proapopototic mitochondrial proteins, including cytochrome c and Samc, in parthenolide-treated cells. Moreover, selective inhibition of caspase 8 activity by a synthetic caspase inhibitor (IETD-FMK) or overexpression of a viral protein (CrmA) suppressed the cleavage of Bid, conformational changes of Bax, cytochrome c release, and apoptosis. Therefore, the proapoptotic Bcl-2 family members are important mediators relaying the cell death signaling elicited by parthenolide from caspase 8 to downstream effector caspases such as caspase 3, and eventually to cell death.
authors.affiliation: Department of Community, Occupational and Family Medicine, Faculty of Medicine (MD3), National University of Singapore, 16 Medical Drive, Singapore 117597.
authors.forename: Siyuan
authors.initials: S
authors.lastname: Zhang
authors.forename: Choon-Nam
authors.initials: CN
authors.lastname: Ong
authors.forename: Han-Ming
authors.initials: HM
authors.lastname: Shen
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D053181:Caspase 8; D020169:Caspases / Q000494:pharmacology; D015179:Colorectal Neoplasms / Q000473:pathology; D019254:Genes, bcl-2 / Q000235:genetics*; D006801:Humans; D008928:Mitochondria / Q000187:drug effects* / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000494:pharmacology*; D012717:Sesquiterpenes / Q000494:pharmacology*; D015398:Signal Transduction; D020903:Tanacetum parthenium / Q000737:chemistry; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2; D012717:Sesquiterpenes; C002669:parthenolide; C505530:CASP8 protein, human; D053181:Caspase 8; D020169:Caspases