Transactivation of inducible nitric oxide synthase gene by Kruppel-like factor 6 regulates apoptosis during influenza A virus infection.
Influenza A virus (flu) is a respiratory tract pathogen causing high morbidity and mortality among the human population. NO is a cellular mediator involved in tissue damage through its apoptosis of target cells and resulting enhancement of local inflammation. Inducible NO synthase (iNOS) is involved in the production of NO following infection. Although NO is a key player in the development of exaggerated lung disease during flu infection, the underlying mechanism, including the role of NO in apoptosis during infection, has not been reported. Similarly, the mechanism of iNOS gene induction during flu infection is not well defined in terms of the host transactivator(s) required for iNOS gene expression. In the current study, we identified Kruppel-like factor 6 (KLF6) as a critical transcription factor essential for iNOS gene expression during flu infection. We also underscored the requirement for iNOS in inducing apoptosis during infection. KLF6 gene silencing in human lung epithelial cells resulted in the drastic loss of NO production, iNOS promoter-specific luciferase activity, and expression of iNOS mRNA following flu infection. Chromatin immunoprecipitation assay revealed a direct interaction of KLF6 with iNOS promoter during in vitro and in vivo flu infection of human lung cells and mouse respiratory tract, respectively. A significant reduction in flu-mediated apoptosis was noted in KLF6-silenced cells, cells treated with iNOS inhibitor, and primary murine macrophages derived from iNOS knockout mice. A similar reduction in apoptosis was noted in the lungs following intratracheal flu infection of iNOS knockout mice.
Department of Microbiology and Immunology, The University of Texas Health Science Center, San Antonio, TX 78229, USA.
Victoria
V
Mgbemena
Jesus A
JA
Segovia
Te-Hung
TH
Chang
Su-Yu
SY
Tsai
Garry T
GT
Cole
Chiung-Yu
CY
Hung
Santanu
S
Bose
D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D020868:Gene Silencing / Q000276:immunology; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D052247:Nitric Oxide Synthase Type II / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D009976:Orthomyxoviridae Infections / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D011401:Promoter Regions, Genetic / Q000276:immunology; D011518:Proto-Oncogene Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation / Q000235:genetics / Q000276:immunology*
D051017:Apoptosis Regulatory Proteins; C105465:KLF6 protein, human; C491358:Klf6 protein, mouse; D000075723:Kruppel-Like Factor 6; D051741:Kruppel-Like Transcription Factors; D011518:Proto-Oncogene Proteins; D052247:Nitric Oxide Synthase Type II