HIV-1 Tat potentiates TNF-induced NF-kappa B activation and cytotoxicity by altering the cellular redox state.
This study demonstrates that human immunodeficiency virus type 1 (HIV-1) Tat protein amplifies the activity of tumor necrosis factor (TNF), a cytokine that stimulates HIV-1 replication through activation of NF-kappa B. In HeLa cells stably transfected with the HIV-1 tat gene (HeLa-tat cells), expression of the Tat protein enhanced both TNF-induced activation of NF-kappa B and TNF-mediated cytotoxicity. A similar potentiation of TNF effects was observed in Jurkat T cells and HeLa cells treated with soluble Tat protein. TNF-mediated activation of NF-kappa B and cytotoxicity involves the intracellular formation of reactive oxygen intermediates. Therefore, Tat-mediated effects on the cellular redox state were analyzed. In both T cells and HeLa cells HIV-1 Tat suppressed the expression of Mn-dependent superoxide dismutase (Mn-SOD), a mitochondrial enzyme that is part of the cellular defense system against oxidative stress. Thus, Mn-SOD RNA protein levels and activity were markedly reduced in the presence of Tat. Decreased Mn-SOD expression was associated with decreased levels of glutathione and a lower ratio of reduced:oxidized glutathione. A truncated Tat protein (Tat1-72), known to transactivate the HIV-1 long terminal repeat (LTR), no longer affected Mn-SOD expression, the cellular redox state or TNF-mediated cytotoxicity. Thus, our experiments demonstrate that the C-terminal region of HIV-1 Tat is required to suppress Mn-SOD expression and to induce pro-oxidative conditions reflected by a drop in reduced glutathione (GSH) and the GSH:oxidized GSH (GSSG) ratio.(ABSTRACT TRUNCATED AT 250 WORDS)
Division of Immunogenetics, German Cancer Research Center, Heidelberg.
M O
MO
Westendorp
V A
VA
Shatrov
K
K
Schulze-Osthoff
R
R
Frank
M
M
Kraft
M
M
Los
P H
PH
Krammer
W
W
Dröge
V
V
Lehmann
D000163:Acquired Immunodeficiency Syndrome / Q000209:etiology; D015536:Down-Regulation; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism*; D005978:Glutathione / Q000032:analysis; D015497:HIV-1 / Q000254:growth & development / Q000378:metabolism* / Q000472:pathogenicity; D006367:HeLa Cells; D006801:Humans; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism*; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000032:analysis; D017382:Reactive Oxygen Species; D013329:Structure-Activity Relationship; D013482:Superoxide Dismutase / Q000096:biosynthesis* / Q000235:genetics; D013489:Suppression, Genetic; D013601:T-Lymphocytes; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D054322:tat Gene Products, Human Immunodeficiency Virus
D015696:Gene Products, tat; D016328:NF-kappa B; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D054322:tat Gene Products, Human Immunodeficiency Virus; D013482:Superoxide Dismutase; D005978:Glutathione