REGULATION OF APOPTOSIS OF INTERLEUKIN 2-DEPENDENT MOUSE T-CELL LINE BY PROTEIN-TYROSINE PHOSPHORYLATION AND POLYAMINES

We examined the effect of inhibitors of tyrosine kinase and tyrosine p hosphatase on DNA fragmentation, protein tyrosine phosphorylation, and polyamine metabolism in the murine T-cell line CTLL-2. When cells wer e exposed to herbimycin A, a specific inhibitor of tyrosine kinase (Ue hara et al., 1989, Biochem. Biophys. Res, Commun., 163:803-809), in th e presence of interleukin 2 (IL-2), DNA was degraded into oligonucleos omal fragments in a dose-dependent fashion. Genistein, another inhibit or of tyrosine kinase (Akiyama et al., 1987, J. Biol. Chem., 262:5592- 5596), had similar effects. Exposure of CTLL-2 cells to vanadate, a ty rosine phosphatase inhibitor, blocked with the DNA fragmentation induc ed by herbimycin A, Tyrosine phosphorylation of 55 Kd protein was inhi bited by herbimycin A, and the inhibition was reduced by vanadate. Orn ithine decarboxylase (ODC) activity decreased rapidly after herbimycin A was added to CTLL-2 cell cultures, while vanadate increased ODC act ivity. The exogenous addition of putrescine or spermine, but not that of spermidine, attenuated herbimycin A-induced DNA fragmentation. Thes e findings suggest that phosphorylation of tyrosine residues of 55 Kd protein prevents DNA fragmentation and that polyamines are involved in regulation of apoptosis. (C) 1995 Wiley-Liss, Inc.