Stable expression of human immunodeficiency virus type 1 Nef confers resistance against Fas-mediated apoptosis.
To investigate the effect of Nef on Fas-mediated apoptosis, we compared T cells, both population and subclones stably expressing Nef from HIV-1(NL432), with Nef(-) control cells. Fas-mediated apoptosis was significantly delayed in Nef(+) cells as determined by annexin V staining and the percentage of apoptotic cells was lower in all Nef-expressing cells than in the control cells by a maximum of 10-fold. Next we measured cell surface levels of Fas to test whether the delayed apoptosis in Nef(+) cells was due to reduced cell surface expression of Fas. We found that there was no significant difference in the surface level of Fas between the Nef(+) and Nef(-) cells. To further define the steps affected by Nef in the Fas signaling pathway, the activation of caspase-3 and caspase-8 was investigated. A reasonable correlation was found between the magnitude of apoptosis measured by annexin V staining and the enzymatic activity of caspase-3. The overall level of caspase-8 activity in Nef(+) cells was also lower than in Nef(-) cells, although the extent of inhibition was not as significant as seen for caspase-3. Overall, our results indicate that long-term stable expression of Nef, which mimicks persistent or latent infection in vivo, confers resistance against anti-Fas Ab-induced apoptosis through inhibition of caspase-3 and caspase-8 activation.
Yoon
K
K
Institute of Molecular Biology and Genetics, Seoul National University, Seoul 151-742, South Korea.
Jeong
J G
JG
Kim
S
S
D017304:Annexin A5; D000911:Antibodies, Monoclonal / Q000276:immunology; D017209:Apoptosis; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002999:Clone Cells; D005434:Flow Cytometry; D015693:Gene Products, nef / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015497:HIV-1 / Q000472:pathogenicity*; D006801:Humans; D019169:Jurkat Cells; D009154:Mutation; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism / Q000473:pathology / Q000821:virology*; D019014:fas Receptor / Q000032:analysis / Q000276:immunology / Q000502:physiology*; D054311:nef Gene Products, Human Immunodeficiency Virus
D017304:Annexin A5; D000911:Antibodies, Monoclonal; D015693:Gene Products, nef; D019014:fas Receptor; D054311:nef Gene Products, Human Immunodeficiency Virus; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases