title: Susceptibility of HIV-1-TAT transfected cells to undergo apoptosis. Biochemical mechanisms.
abstract: The effects of HIV-1 Tat protein on mitochondria membrane permeability and apoptosis were analysed in lymphoid cells. In this report we show that stable-transfected HIV-Tat cells are primed to undergo apoptosis upon serum withdrawal. This effect was observed in both the Jhan T cell line and the K562 cells, the latter expressing the bcr-abl chimeric gene, which confers resistance to apoptosis induced by different stimuli. Using a cytofluorimetric approach we have determined that serum withdrawal induces a disruption of the transmembrane mitochondrial potential (Deltapsim) followed by an increase of reactive oxygen species (ROS) and the subsequent DNA nuclear loss in K562-Tat cells but not in the K562-pcDNA cell line. These pre-apoptotic events were associated with the cleavage of the caspase-3, while the expression of Bcl-2, Bcl-XL and Bax proteins was not affected by the presence of Tat. Regardless of the steady state of the Bax protein, we found that in both K562 and K562-Tat cells, this protein is located in the nucleus, but after serum withdrawal its localization was mainly in the cytoplasm. The activity of caspase-3 detected in K562-Tat cells after serum withdrawal paralleled with the mitochondria permeability transition. Nevertheless, in Jhan-Tat cells the inhibition of this caspase with the specific inhibitor, z-DEVD-cmk, did not affect the disruption of the mitochondria potential induced by serum withdrawal. Interestingly, we found that HIV-Tat protein accumulates at the mitochondria in the K562-Tat cells cultured under low serum conditions, and this mitochondrial localization correlated with the Deltapsim disruption detected in these cells. In addition, HIV-1 Tat protein synergies with protoporphyrin IX (PPIX), a ligand of the mitochondrial benzodiazepine receptor, in the induction of apoptosis in both Jhan and K562 cells. Thus, HIV-1 Tat protein may induce apoptosis by a mechanism that involves mitochondrial PT and may contribute to the lymphocyte depletion seen in AIDS patients.
authors.affiliation: Departamento de Fisiología e Inmunología, Universidad de Córdoba, Facultad de Medicina, Avda. de Menéndez Pidal s/n, 14071 Córdoba, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Macho
authors.forename: M A
authors.initials: MA
authors.lastname: Calzado
authors.forename: L
authors.initials: L
authors.lastname: Jiménez-Reina
authors.forename: E
authors.initials: E
authors.lastname: Ceballos
authors.forename: J
authors.initials: J
authors.lastname: León
authors.forename: E
authors.initials: E
authors.lastname: Muñoz
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism; D015756:Genes, tat; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy / Q000473:pathology* / Q000821:virology*; D015458:Leukemia, T-Cell / Q000188:drug therapy / Q000473:pathology* / Q000821:virology*; D008564:Membrane Potentials; D008928:Mitochondria / Q000502:physiology; D009842:Oligopeptides / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011524:Protoporphyrins / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000821:virology; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: C494826:BAX protein, human; C494811:BCL2L1 protein, human; D061945:Caspase Inhibitors; D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D015696:Gene Products, tat; D009842:Oligopeptides; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011524:Protoporphyrins; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; C120992:benzyloxycarbonyl aspartyl-glutamyl-valyl-aspartyl-chloromethyl ketone; D054322:tat Gene Products, Human Immunodeficiency Virus; C028025:protoporphyrin IX; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases