title: Identification of chelerythrine as an inhibitor of BclXL function.
abstract: The identification of small molecule inhibitors of antiapoptotic Bcl-2 family members has opened up new therapeutic opportunities, while the vast diversity of chemical structures and biological activities of natural products are yet to be systematically exploited. Here we report the identification of chelerythrine as an inhibitor of BclXL-Bak Bcl-2 homology 3 (BH3) domain binding through a high throughput screening of 107,423 extracts derived from natural products. Chelerythrine inhibited the BclXL-Bak BH3 peptide binding with IC50 of 1.5 micro m and displaced Bax, a BH3-containing protein, from BclXL. Mammalian cells treated with chelerythrine underwent apoptosis with characteristic features that suggest involvement of the mitochondrial pathway. While staurosporine, H7, etoposide, and chelerythrine released cytochrome c from mitochondria in intact cells, only chelerythrine released cytochrome c from isolated mitochondria. Furthermore BclXL-overexpressing cells that were completely resistant to apoptotic stimuli used in this study remained sensitive to chelerythrine. Although chelerythrine is widely known as a protein kinase C inhibitor, the mechanism by which it mediates apoptosis remain controversial. Our data suggest that chelerythrine triggers apoptosis through a mechanism that involves direct targeting of Bcl-2 family proteins.
authors.affiliation: Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore 117609, Republic of Singapore.
authors.forename: Shing-Leng
authors.initials: SL
authors.lastname: Chan
authors.forename: Mei Chin
authors.initials: MC
authors.lastname: Lee
authors.forename: Kuan Onn
authors.initials: KO
authors.lastname: Tan
authors.forename: Lay-Kien
authors.initials: LK
authors.lastname: Yang
authors.forename: Alex S Y
authors.initials: AS
authors.lastname: Lee
authors.forename: Horst
authors.initials: H
authors.lastname: Flotow
authors.forename: Nai Yang
authors.initials: NY
authors.lastname: Fu
authors.forename: Mark S
authors.initials: MS
authors.lastname: Butler
authors.forename: Doel D
authors.initials: DD
authors.lastname: Soejarto
authors.forename: Antony D
authors.initials: AD
authors.lastname: Buss
authors.forename: Victor C
authors.initials: VC
authors.lastname: Yu
mesh_terms: D000470:Alkaloids; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D053119:Benzophenanthridines; D003574:Cytochrome c Group / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D015870:Gene Expression; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D018716:Molecular Mimicry; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010617:Phenanthridines / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D019311:Staurosporine / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
chemical_list: D000470:Alkaloids; D000970:Antineoplastic Agents; C494772:BAK1 protein, human; C494826:BAX protein, human; C494811:BCL2L1 protein, human; D053119:Benzophenanthridines; D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D010617:Phenanthridines; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D005047:Etoposide; C016299:chelerythrine; D019311:Staurosporine