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Characterization of cholix toxin-induced apoptosis in hela cells.
MedLine Citation:
PMID:  21903588     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Cholix toxin (Cholix) is a novel ADP-ribosylating cytotoxin produced by Vibrio cholerae, which utilizes eukaryotic elongation factor 2 as a substrate and acts by a mechanism similar to that of diphtheria toxin and Pseudomonas exotoxin A. First it was found that Cholix-treated HeLa cells exhibited caspase-dependent apoptosis, while intestinal cells such as Caco-2, HCT116, and RKO did not. Here we investigated Cholix-induced cell death signaling pathways in HeLa cells. Cholix-induced cytochrome c release into cytosol was initiated by specific conformational changes of pro-apoptotic Bak associated with Bax. Silencing of bak/bax genes or bak gene alone using siRNA significantly suppressed cytochrome c release and caspase-7 activation, but not activation of caspases-3 and -9. Although pretreatment with a caspase-8 inhibitor (Z-IETD-FMK) reduced Cholix-induced cytochrome c release and activation of caspases-3, -7, and -9, cytotoxicity was not decreased. Pretreatment with Z-YVAD-FMK, which inhibits caspase-1, -4, and -5, suppressed not only cytochrome c release, activation of caspase-3, -7, -8, or -9, and PARP cleavage, but also cytotoxicity, indicating that caspases-1, -4, and -5 activation is initiated at an early stage of Cholix-induced apoptosis and promotes caspase-8 activation. These results show that the inflammatory caspases (caspases-1, -4, and -5) and -8 are responsible for both mitochondrial signals and other caspase activation. In conclusion, we showed that Cholix-induced caspase activation plays an essential role in generation of apoptotic signals, which are mediated by both mitochondria-dependent and -independent pathways.
Authors:
Kohei Ogura; Kinnosuke Yahiro; Hiroyasu Tsutsuki; Sayaka Nagasawa; Shinji Yamasaki; Joel Moss; Masatoshi Noda
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-9-8
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  -     ISSN:  1083-351X     ISO Abbreviation:  -     Publication Date:  2011 Sep 
Date Detail:
Created Date:  2011-9-9     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Chiba University, Japan;
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