THE C-JUN N-TERMINAL KINASE CASCADE PLAYS A ROLE IN STRESS-INDUCED APOPTOSIS IN JURKAT CELLS BY UP-REGULATING FAS LIGAND EXPRESSION

T lymphocytes undergo apoptosis in response to cellular stress, includ ing UV exposure and gamma irradiation, However, the mechanism by which stress stimuli induce apoptosis is not well understood, While stress stimuli induce the activation of the c-Jun N-terminal kinase (JNK) pat hway, it is not clear whether the JNK cascade is activated as a result of cell death or whether the cascade participates in inducing apoptos is, Using a Jurkat T cell line transfected with dominant active (DA)-m itogen-activated protein kinase kinase kinase (MEKK1) in a tetracyclin e-regulated expression system, we found that expression of DA-MEKK1 re sults in the apoptosis of Jurkat cells in parallel with prolonged JNK activation, Moreover, DA-MEKK1 induced Fas ligand (FasL) fell surface and mRNA expression, as well as FasL promoter activation, Interference with Fas/FasL interaction prevented DA-MEKK1-mediated apoptosis, In c omparing the effect of different stress stimuli to DA-MEKK1, we found that UV, gamma irradiation, and anisomycin prolonged JNK activation in parallel with FasL expression and onset of cell death, In addition, t hese stimuli also enhance cell surface expression of FasL, Interferenc e with Fas/FasL interactions inhibited anisomycin but not UV-or gamma irradiation-induced apoptosis, Our data show that while the JNK pathwa y contributes to stress-induced apoptosis in T lymphocytes by regulati ng FasL expression, not all stress stimuli use the same cell death pat hway.