Involvement of both caspase-like proteases and serine proteases in apoptotic cell death induced by ricin, modeccin, diphtheria toxin, and pseudomonas toxin.
We investigated the involvement of caspases and serine proteases in apoptotic cell death induced by ricin, modeccin, diphtheria toxin, and Pseudomonas toxin in U937 cells. We found that caspase-3- and caspase-6-like activities, but not caspase-1-like activity, increased during toxin-induced apoptosis. Z-D-CH2-DCB, a caspase-like inhibitor, completely inhibited the generation of caspase-3- and caspase-6-like activities and blocked all features of apoptosis induced by toxins: nuclear morphological changes, DNA fragmentation, and cytotoxicity. However, three caspase-specific inhibitors, Ac-YVAD-CHO, Ac-DEVD-CHO, and Ac-VEID-CHO, had no effect, even though Ac-DEVD-CHO and Ac-VEID-CHO inhibited the increased caspase-3- and caspase-6-like activity, respectively. These results suggest that the generation of caspase-3- and caspase-6-like activities is redundant, and other caspases distinct from caspase-3 and -6 may be important in toxin-induced apoptosis. Furthermore, serine protease inhibitor, 3,4-dichloroisocoumarine (DCI), abolished the apoptotic cell death and DNA fragmentation caused by toxins, without affecting the increased caspase-3- and caspase-6-like activities. Our results suggest that multiple proteases with different preferences for apoptotic substrates participate in toxin-induced apoptotic death of U937 cells.
Komatsu
N
N
Division of Biochemistry, Faculty of Fisheries, Nagasaki University, Bunkyo-machi, Nagasaki, 852-8521, Japan.
Oda
T
T
Muramatsu
T
T
D036002:ADP Ribose Transferases; D017209:Apoptosis / Q000187:drug effects*; D001427:Bacterial Toxins; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004167:Diphtheria Toxin / Q000494:pharmacology*; D005098:Exotoxins / Q000494:pharmacology*; D006801:Humans; D037102:Lectins / Q000494:pharmacology*; D037121:Plant Lectins; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D054790:Ribosome Inactivating Proteins, Type 2; D012276:Ricin / Q000494:pharmacology*; D012697:Serine Endopeptidases / Q000378:metabolism*; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D003546:Cysteine Endopeptidases; D004167:Diphtheria Toxin; D005098:Exotoxins; D037102:Lectins; D037121:Plant Lectins; D011500:Protein Synthesis Inhibitors; D054790:Ribosome Inactivating Proteins, Type 2; D012276:Ricin; D012697:Serine Endopeptidases; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C016004:modeccin