• Journal of Microbiology and Biotechnology
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• 제15권4호
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• pp.756-766
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• 2005

The signaling mechanism underlying aburatubolactam C-induced FasL upregulation was investigated in human Jurkat T cells. After treatment with aburatubolactam C, the src-family PTKs $p56^{lck}\;and\;p59^{fyn}$, and MAP kinases ERK2 and JNK1, were activated prior to FasL upregulation; Both $p56^{lck}\;and\;p59^{fyn}$ were directly activated 2.4- and 2.2-fold, respectively, in vitro by aburatubolactam C. The aburatubolactam C-induced cellular changes, including the activation of ERK2 and INK1, and FasL upregulation, were completely prevented by the PTK inhibitor genistein. The activation of protein kinase C (PKC$\delta,\;\epsilon\;and\;\mu$ was also induced following aburatubolactam C treatment. Although the activation of $p56^{lck}$ and tyrosine phosphorylation of the cellular proteins were not blocked by the PKC inhibitor GFl09203X, the activation of ERK2 was completely abrogated, along with a detectably enhanced JNK1 activation; FasL upregulation, and apoptosis. However, the FasL upregulation and apoptosis were significantly inhibited by the PKC activator PMA, with a remarkable increase in the ERK2 activation. The cytotoxic effect of aburatubolactam C was reduced in the presence of the anti-Fas neutralizing antibody ZB-4. Although ectopic expression of Bcl-2 failed to completely block the cytotoxicity of aburatubolactam C, it was clearly suppressed. The c-Fos mRNA expression was upregulated in a biphasic manner, where the second phasic expression overlapped with the FasL upregulation. Accordingly, these results demonstrate that aburatubolactam C-induced apoptosis is exerted, at least in part, by FasL upregulation dictated by activation of the PTK ($p56^{lck}\;and\;p59^{fyn}$) /JNKI pathway, which is negatively affected by the concurrent activation of the PKC/ERK2 pathway proximal to PTK activation.

• BMB Reports
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• 제31권4호
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• pp.355-363
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• 1998

MHC unrestricted, antigen nonspecific killing by $CD4^+$ T-cells against virally-infected target cells was induced following cross-linking of CD4 molecules. The cytotoxicity of antibody-activated $CD4^+$ T-cells was abolished by genistein (4',5,7-trihydroxyisoflavone), a protein tyrosine kinase (PTK) inhibitor, but not by H-7, a protein kinase C (PKC) inhibitor. Genisteintreated human or bovine peripheral blood $CD4^+$ T-cells lacked PTK activity and failed to kill virally-infected target cells even after cross-linking of CD4 molecules. The cross-linking of CD4 molecules did not induce effector cell proliferation or the transcription of TNF ${\beta}$. TNF ${\beta}$ synthesis was up-regulated by incubating antibody activated effector cells with bovine herpesvirus type 1 (BHV-1) infected D17 target cells. Anti-TNF ${\beta}$ antibody partially abrogated direct effector cell-mediated antiviral cytotoxicity. On the other hand, this antibody effectively neutralized antiviral activity of effector and target cell culture supernatants against BHV-1 infected D17 cells. The inhibition level of the antiviral activity by the antibody was dependent on effector and target cell ratio. These findings have importance to define the mechanisms of how CD4 cytotoxic cells control viral infection.