Molecular Genetic Analysis of Human Herpes Virus 8-encoded Viral FLICE Inhibitory Protein-induced NF-κB Activation

• Published in: The Journal of biological chemistry 2003-12, Vol.278 (52), p.52406
• Main Authors: Hittu Matta, Qinmiao Sun, Gregory Moses, Preet M. Chaudhary
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M307308200

The human herpes virus 8 (HHV8)-encoded viral FLICE inhibitory protein (vFLIP), also known as K13, is known to activate the NF-κB pathway, a property not shared by other vFLIPs. Previous studies have demonstrated that HHV8 vFLIP K13 interacts with several cellular signaling proteins involved in NF-κB activation, such as receptor-interacting protein, NF-κB-inducing kinase, IκB kinase (IKK) 1, IKK2, and NF-κB essential modulator (NEMO). In this report we have used cell lines deficient in the above proteins to investigate the mechanism of NF-κB activation via HHV8 vFLIP K13. We demonstrate that receptor-interacting protein and NF-κB-inducing kinase are dispensable for vFLIP K13-induced NF-κB DNA binding and transcriptional activation. On the other hand, vFLIP K13-induced NF-κB DNA binding activity is significantly reduced, although not absent, in cells deficient in IKK1, IKK2, and NEMO. Furthermore, vFLIP K13-induced NF-κB transcriptional activity is only weakly present in IKK1-deficient cells and almost completely absent in those deficient in IKK2 and NEMO. HHV8 vFLIP K13-induced NF-κB activation in IKK1- and IKK2-deficient fibroblasts could be rescued by wild type but not by the kinase-inactive mutants of IKK1 and IKK2, respectively. Consistent with the above results, vFLIP K13-induced NF-κB activation could be effectively blocked by chemical inhibitors of the kinase activity of IKK1 and IKK2. Thus, a cooperative interaction of all three subunits of the IKK complex is required for maximal NF-κB activation via HHV8 vFLIP K13. Selective inhibitors of the IKK1 kinase activity may have a role in the treatment of disorders caused by abnormal NF-κB activation by HHV8 vFLIP K13.