Polyomavirus large T-antigen protects mouse cells from Fas-, TNF-alpha- and taxol-induced apoptosis.
Polyomavirus large T-antigen (PyLT-Ag), a nucleophosphoprotein essential for regulating viral gene expression, modulates the cell cycle by binding to the Rb tumor suppressor gene product. PyLT-Ag/Rb binding is essential for in vitro immortalization. However, the effect of PyLT-Ag on apoptosis has not been extensively studied. We have previously reported that FasR agonist antibodies (FasR(Ab)) treatment of Sertoli cells derived from transgenic mice expressing PyLT-Ag induces the growth arrest of these cells without concomitant apoptosis. Here we show that stable expression of PyLT-Ag in murine Sertoli TM4 and hybridoma NSO cell lines confers protection from FasR(Ab)-induced apoptosis. The protection was maintained up to 48 h when cells were grown continuously in the presence of FasR(Ab). Removal of the death stimulus after 24 h exposure was sufficient to allow full recovery of the PyLT-Ag expressing cells. The protective effect conferred by PyLT-Ag was associated with a delay in the sequential activation of caspase-8 and -3 after FasR(Ab) treatment. PyLT-Ag co-precipitated following immunoprecipitation of caspase-8 or FADD, both components of the DISC. Based on these results we suggest that PyLT-Ag directly impedes the recruitment or activation of caspase-8 by the FasR. PyLT-Ag expression in TM4 cells was also associated with protection from TNF-alpha- and taxol-induced apoptosis. In contrast, PyLT-Ag expression was not sufficient to confer protection from captothecin-induced apoptosis. Taken together, these results indicate that PyLT-Ag can be a potent inhibitor of Fas(R)(Ab)-, TNF-alpha- and taxol-induced apoptosis.
Rodier
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F
Centre de recherche CHUM, Hôpital Notre Dame and Institut du cancer de Montréal, 1560 rue Sherbrooke est, Montréal, Québec, Canada.
Bertrand
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R
Bossolasco
M
M
Mes-Masson
A M
AM
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000911:Antibodies, Monoclonal; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017209:Apoptosis; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D053200:Fas-Associated Death Domain Protein; D006825:Hybridomas; D007700:Kinetics; D046911:Macromolecular Substances; D008297:Male; D051379:Mice; D008954:Models, Biological; D017239:Paclitaxel / Q000494:pharmacology*; D012708:Sertoli Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D019014:fas Receptor / Q000276:immunology / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal; D000952:Antigens, Polyomavirus Transforming; D002352:Carrier Proteins; C505534:Fadd protein, mouse; D053200:Fas-Associated Death Domain Protein; D046911:Macromolecular Substances; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; C505409:Casp3 protein, mouse; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D017239:Paclitaxel