title: HIV type 1 Tat inhibits tumor necrosis factor alpha-induced repression of tumor necrosis factor receptor p55 and amplifies tumor necrosis factor alpha activity in stably tat-transfected HeLa Cells.
abstract: The human immunodeficiency virus type 1 (HIV-1) Tat protein is a key regulatory protein in the HIV-1 replication cycle. Tat interacts with cellular transcriptional factors and cytokines, such as tumor necrosis factor (TNF-alpha), and alters the expression of a variety of genes in HIV-1-infected and noninfected cells. To further elucidate the mechanisms by which HIV-1 Tat amplifies the activity of TNF-alpha, we transfected the HIV-1 tat gene into an epithelial (HeLa) cell line. We observed that Tat-expressing cells had increased NF-kappa B-dependent trans-activational activity due to enhanced NF-kappa B--DNA binding in response to TNF-alpha treatment. Tumor necrosis factor receptor (TNFR) p55 was the prominent receptor, as neutralizing antibodies to TNFR p55, but not to TNFR p75, blocked TNF-alpha-mediated NF-kappa B activation. Furthermore, tat-transfected cells were more sensitive to TNF-alpha-induced cytotoxicity and only the neutralizing antibodies to TNFR p55 completely protected the cells. To determine whether TNFR p55 was involved in amplification of cellular response to TNF-alpha by HIV-1 Tat, we investigated the effect of TNF-alpha on TNFR p55 expression in the tat-transfected cells. TNF-alpha treatment resulted in a reduction in both TNFR p55 mRNA and protein levels in the control cells but not in the tat-transfected cells as determined with Northern blot and Western blot analyses, respectively. Our results indicate that HIV-1 Tat may inhibit TNF-alpha-induced repression of TNFR p55 and thereby amplify TNF-alpha activity in these stably transfected cells.
authors.affiliation: Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health and Science, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
authors.forename: C
authors.initials: C
authors.lastname: Chiao
authors.forename: T
authors.initials: T
authors.lastname: Bader
authors.forename: J E
authors.initials: JE
authors.lastname: Stenger
authors.forename: W
authors.initials: W
authors.lastname: Baldwin
authors.forename: J
authors.initials: J
authors.lastname: Brady
authors.forename: J C
authors.initials: JC
authors.lastname: Barrett
mesh_terms: D015703:Antigens, CD / Q000378:metabolism*; D015153:Blotting, Western; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D047888:Receptors, Tumor Necrosis Factor, Type I; D015533:Transcriptional Activation; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism* / Q000494:pharmacology; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D015703:Antigens, CD; D015696:Gene Products, tat; D016328:NF-kappa B; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha; D054322:tat Gene Products, Human Immunodeficiency Virus