The presence of HIV-1 Tat protein second exon delays fas protein-mediated apoptosis in CD4+ T lymphocytes: a potential mechanism for persistent viral production.
HIV-1 replication is efficiently controlled by the regulator protein Tat (101 amino acids) and codified by two exons, although the first exon (1-72 amino acids) is sufficient for this process. Tat can be released to the extracellular medium, acting as a soluble pro-apoptotic factor in neighboring cells. However, HIV-1-infected CD4(+) T lymphocytes show a higher resistance to apoptosis. We observed that the intracellular expression of Tat delayed FasL-mediated apoptosis in both peripheral blood lymphocytes and Jurkat cells, as it is an essential pathway to control T cell homeostasis during immune activation. Jurkat-Tat cells showed impairment in the activation of caspase-8, deficient release of mitochondrial cytochrome c, and delayed activation of both caspase-9 and -3. This protection was due to a profound deregulation of proteins that stabilized the mitochondrial membrane integrity, such as heat shock proteins, prohibitin, or nucleophosmin, as well as to the up-regulation of NF-κB-dependent anti-apoptotic proteins, such as BCL2, c-FLIPS, XIAP, and C-IAP2. These effects were observed in Jurkat expressing full-length Tat (Jurkat-Tat101) but not in Jurkat expressing the first exon of Tat (Jurkat-Tat72), proving that the second exon, and particularly the NF-κB-related motif ESKKKVE, was necessary for Tat-mediated protection against FasL apoptosis. Accordingly, the protection exerted by Tat was independent of its function as a regulator of both viral transcription and elongation. Moreover, these data proved that HIV-1 could have developed strategies to delay FasL-mediated apoptosis in infected CD4(+) T lymphocytes through the expression of Tat, thus favoring the persistent replication of HIV-1 in infected T cells.
Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Spain.
María Rosa
MR
López-Huertas
Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Spain.
Elena
E
Mateos
Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Spain.
María
M
Sánchez Del Cojo
Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, 28922 Alcorcón, Madrid, Spain.
Francisco
F
Gómez-Esquer
Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, 28922 Alcorcón, Madrid, Spain.
Gema
G
Díaz-Gil
Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Spain.
Sara
S
Rodríguez-Mora
Unidad de Proteómica, Centro Nacional de Investigaciones Cardiovasculares, 28029 Madrid, Spain.
Juan Antonio
JA
López
Unidad de Proteómica, Centro Nacional de Investigaciones Cardiovasculares, 28029 Madrid, Spain.
Enrique
E
Calvo
Health and Biomedical Informatics Research Unit, Melbourne Medical School, 3010 Melbourne, Australia.
Guillermo
G
López-Campos
Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Spain.
José
J
Alcamí
Unidad de Inmunopatología del SIDA, Centro Nacional de Microbiología, Instituto de Salud Carlos III, 28220 Majadahonda, Spain. Electronic address: mcoiras@isciii.es.
Mayte
M
Coiras
D017209:Apoptosis; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism / Q000821:virology*; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D005091:Exons; D005786:Gene Expression Regulation; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D019169:Jurkat Cells; D008928:Mitochondria / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D016328:NF-kappa B / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D020543:Proteome; D040901:Proteomics / Q000379:methods; D014162:Transfection; D019014:fas Receptor / Q000378:metabolism*; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000378:metabolism*
D016328:NF-kappa B; D020543:Proteome; D019014:fas Receptor; D054322:tat Gene Products, Human Immunodeficiency Virus; D045304:Cytochromes c; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9