Molecular genetic analysis of human herpes virus 8-encoded viral FLICE inhibitory protein-induced NF-kappaB activation.
The human herpes virus 8 (HHV8)-encoded viral FLICE inhibitory protein (vFLIP), also known as K13, is known to activate the NF-kappaB 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-kappaB activation, such as receptor-interacting protein, NF-kappaB-inducing kinase, IkappaB kinase (IKK) 1, IKK2, and NF-kappaB essential modulator (NEMO). In this report we have used cell lines deficient in the above proteins to investigate the mechanism of NF-kappaB activation via HHV8 vFLIP K13. We demonstrate that receptor-interacting protein and NF-kappaB-inducing kinase are dispensable for vFLIP K13-induced NF-kappaB DNA binding and transcriptional activation. On the other hand, vFLIP K13-induced NF-kappaB DNA binding activity is significantly reduced, although not absent, in cells deficient in IKK1, IKK2, and NEMO. Furthermore, vFLIP K13-induced NF-kappaB 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-kappaB 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-kappaB 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-kappaB 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-kappaB activation by HHV8 vFLIP K13.
Matta
Hittu
H
Hamon Center for Therapeutic Oncology Research and Division of Hematology-Oncology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8593, USA.
Sun
Qinmiao
Q
Moses
Gregory
G
Chaudhary
Preet M
PM
D000818:Animals; D015153:Blotting, Western; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D017930:Genes, Reporter; D019288:Herpesvirus 8, Human / Q000378:metabolism*; D006801:Humans; D051550:I-kappa B Kinase; D019169:Jurkat Cells; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D015398:Signal Transduction; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics*
D004791:Enzyme Inhibitors; D016328:NF-kappa B; D014764:Viral Proteins; C481275:viral FLIP protein, Human herpesvirus 8; D004247:DNA; D008156:Luciferases; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; C505530:CASP8 protein, human; C505526:Casp8 protein, mouse; D053181:Caspase 8; D020169:Caspases