| 1. |
- Los, Marek Jan, et al.
(author)
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Requirement of an Ice/Ced-3 Protease for Fas/Apo-1-Mediated Apoptosis
- 1995
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 375:6526, s. 81-83
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Journal article (peer-reviewed)abstract
- THE Fas/APO-1 receptor is one of the major regulators of apoptosis(1-7). We report here that Fas/APO-1-mediated apoptosis requires the activation of a new class of cysteine proteases, including interleukin-1 beta-converting enzyme (ICE)(8-10) which are homologous to the product of the Caenorhabditis elegans cell-death gene ced-3 (refs 11, 12). Triggering of Fas/APO-1 rapidly stimulated the proteolytic activity of ICE. Overexpression of ICE, achieved by electroporation and microinjection, strongly potentiated Fas/APO-1-mediated cell death. In addition, inhibition of ICE activity by protease inhibitors, as well as by transient expression of the pox virus-derived serpin inhibitor CrmA or an antisense ICE construct, substantially suppressed Fas/APO-1-triggered cell death. We conclude that activation of ICE or an ICE-related protease is a critical event in Fas/APO-1-mediated cell death.
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| 2. |
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| 3. |
- Los, Marek Jan, et al.
(author)
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Hydrogen-Peroxide as a Potent Activator of T-Lymphocyte Functions
- 1995
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In: European Journal of Immunology. - : Wiley. - 0014-2980 .- 1521-4141. ; 25:1, s. 159-165
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Journal article (peer-reviewed)abstract
- During inflammatory processes infiltrating cells produce large amounts of reactive oxygen intermediates (ROI). Increasing evidence suggests that ROI besides being cytotoxic may act as important mediators influencing various cellular and immunological processes. In this study, we have investigated the effects of hydrogen peroxide on several aspects of lymphocyte activation. In ESb-L T lymphoma cells, micromolar concentrations of hydrogen peroxide rapidly induced activation of the transcription factor NF-kappa B, whereas DNA-binding activity of the transcription factor AP-1 was virtually not affected. In addition, hydrogen peroxide induced early gene expression of interleukin-2 (IL-2) and the IL-2 receptor alpha chain. The stimulation of IL-2 expression was found to be conferred by a kappa B-like cis-regulatory region within the IL-2 gene promoter. In contrast to these activating effects, addition of hydrogen peroxide was largely inhibitory on cell proliferation which is consistent with a general requirement of thiol compounds for lymphocyte proliferation. However, hydrogen peroxide significantly increased T cell proliferation when applied for a short period under reducing conditions. These data indicate that ROI may act as an important competence signal in T lymphocytes inducing early gene expression as well as cell proliferation.
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| 4. |
- Los, Marek Jan, et al.
(author)
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Il-2 Gene-Expression and Nf-Kappa-B Activation Through Cd28 Requires Reactive Oxygen Production by 5-Lipoxygenase
- 1995
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In: EMBO Journal. - 0261-4189 .- 1460-2075. ; 14:15, s. 3731-3740
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Journal article (peer-reviewed)abstract
- Activation of the CD28 surface receptor provides a major costimulatory signal for T cell activation resulting in enhanced production of interleukin-2 (IL-2) and cell proliferation. In primary T lymphocytes we show that CD28 ligation leads to the rapid intracellular formation of reactive oxygen intermediates (ROIs) which are required for CD28-mediated activation of the NF-kappa B/CD28-responsive complex and IL-2 expression. Delineation of the CD28 signaling cascade was found to involve protein tyrosine kinase activity, followed by the activation of phospholipase Az and 5-lipoxygenase. Our data suggest that lipoxygenase metabolites activate ROI formation which then induce IL-2 expression via NF-KB activation. These findings should be useful for therapeutic strategies and the development of immunosuppressants targeting the CD28 costimulatory pathway.
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| 5. |
- Los, Marek Jan, et al.
(author)
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Inhibition of Activation of Transcription Factor Ap-1 by Cd28 Signaling
- 1994
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In: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 302, s. 119-123
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Journal article (peer-reviewed)abstract
- Co-stimulation of T-lymphocytes by T-cell receptor (TcR) occupancy and activation of the CD28 surface molecule results in enhanced proliferation and interleukin 2 (IL-2) production. The increase in IL-2 gene expression triggered by CD28 involves a KB-like sequence in the 5'-regulatory region of the IL-2 promoter, called CD28-responsive element. Stimulation of T-cells by agonistic anti-CD28 antibodies in conjunction with phorbol 12-myristate 13-acetate (PMA)- or TcR-derived signals induces the enhanced activation of the transcription factor NF-B-K. Here we report that CD28 engagement, however, exerts opposite effects on the transcription factor AP-1. Whereas anti-CD28 together with PMA increased the DNA binding and trans-activation activity of NF-B-K, PMA-induced activation of AP-1 was significantly suppressed. The inhibitory effect exerted by anti-CD38 was observed at the level of DNA binding as well as in functional reporter-gene assays. These results suggest that the two transcription factors are independently regulated and may perform different functions during T-cell activation.
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| 6. |
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| 7. |
- Westendorp, Mo, et al.
(author)
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Hiv-1 Tat Potentiates Tnf-Induced Nf-Kappa-B Activation and Cytotoxicity
- 1995
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In: EMBO Journal. - 0261-4189 .- 1460-2075. ; 14:3, s. 546-554
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Journal article (peer-reviewed)abstract
- This study demonstrates that human immunodeficiency virus type 1 (HTV-1) Tat protein amplifies the activity of tumor necrosis factor (TNF), a cytokine that stimulates HTV-1 replication through activation of NF-kappa B. In HeLa cells stably transfected with the HIV-1 tat gene (HeLa-tat cells), expression of the Tat protein enhanced both TNF-induced activation of NF-kappa B and TNF-mediated cytotoxicity. A similar potentiation of TNF effects was observed in Jurkat T cells and HeLa cells treated with soluble Tat protein, TNF-mediated activation of NF-kappa B and cytotoxicity involves the intracellular formation of reactive oxygen intermediates. Therefore, Tat-mediated effects on the cellular redox state were analyzed. In both T cells and HeLa cells HIV-1 Tat suppressed the expression of Mn-dependent superoxide dismutase (Mn-SOD), a mitochondrial enzyme that is part of the cellular defense system against oxidative stress. Thus, Mn-SOD RNA protein levels and activity were markedly reduced in the presence of Tat. Decreased Mn-SOD expression was associated with decreased levels of glutathione and a lower ratio of reduced:oxidized glutathione. A truncated Tat protein (Tat(1-72)), known to transactivate the HIV-1 long terminal repeat (LTR), no longer affected Mn-SOD expression, the cellular redox state or TNF-mediated cytotoxicity. Thus, our experiments demonstrate that the C-terminal region of HIV-1 Tat is required to suppress Mn-SOD expression and to induce pro-oxidative conditions reflected by a drop in reduced glutathione (GSH) and the GSH:oxidized GSH (GSSG) ratio. They further imply a distinct mechanism of Mn-SOD suppression as compared,vith HIV-1 LTR transactivation by Tat. Taken together, our data suggest that Tat expressed in HIV-1-infected cells and Tat taken up by non-infected cells modulates TNF activity by altering the cellular redox state. These findings may be relevant for HIV-1 replication and for T cell depletion in acquired immune deficiency syndrome.
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