Artikel
The viral FLIP molecule K13 of human herpesvirus-8 induces manganese superoxide dismutase in endothelial cells and protects against superoxide-induced cell death
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Veröffentlicht: | 16. April 2008 |
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Introduction: Kaposi’s sarcoma (KS) is an endothelial tumor and human herpesvirus-8 (HHV-8) is the causative agent of this disease. HHV-8 encoded viral FLICE-inhibitory protein K13 is regarded as an important factor for the pathogenesis of KS. K13 is an inhibitor of cell death both by blocking receptor-induced death signaling and by up-regulation of cellular anti-apoptotic proteins. Both activities may protect infected cells from death induced by cytotoxic T-cells which infiltrate into KS lesions. However, it is not known how HHV-8-infected cells circumvent cell damage caused by oxidative stress in the inflammatory milieu of KS lesions.
Materials and methods: 2-D difference gel electrophoresis was performed with Cy3-labeled human endothelial cells stably expressing K13 and Cy5-labeled control cells. Fluorescence was quantified with a FLA-5000 laser scanner (Fuji).Cell Death and superoxide production was measured by flow cytometry with AnnexinV/propidium iodide and dihydroethidium labeling.Immunhistochemistry and confocal laser scanning microscopy was performed with a polyclonal MnSOD-specific antibody.
Results: With comparative proteome analysis we identified the mitochondrial anti-oxidant manganese superoxide dismutase (MnSOD) as a strongly induced protein by K13 in primary endothelial cells. MnSOD is a primary defense enzyme against oxidative stress. Congruously, superoxide production was inhibited in K13-expressing cells and these cells were protected against superoxide-induced death. In addition, the up-regulation of MnSOD was confirmed in HHV-8-infected HUVEC.
Conclusion: These findings link K13 to the inhibition of mitochondrial superoxide accumulation and reveal a novel strategy of cell death prevention by K13. The reduction of oxidative-induced cell damage in the aggressive milieu of KS lesions may be an important process in the pathogenesis of KS.