Extracellular HIV-1 Tat protein activates phosphatidylinositol 3- and Akt/PKB kinases in CD4+ T lymphoblastoid Jurkat cells.
The biological basis for the pleiotropic activity of extracellular human immunodeficiency virus (HIV)-1 Tat protein on lymphoid T cell survival is not well understood. We have here demonstrated that the addition in culture of 0.1-10 nM Tat protein to 36-h serum-starved lymphoblastoid Jurkat T cells rapidly stimulates the catalytic activity of phosphatidylinositol 3-kinase (PI 3-K). The peak of activation was observed 30 min after Tat addition. Extracellular Tat also stimulated the catalytic activity of the Akt/PKB kinase, a major target of PI 3-K lipid products. Pretreatment of serum-starved Jurkat cells with 100 nM wortmannin (WT) or 10 microM LY294002, two unrelated pharmacological inhibitors of PI 3-K, markedly suppressed the catalytic activity of both PI 3-K and Akt/PKB in Jurkat cells. Moreover, at low concentrations (0.1-1 nM), extracellular Tat showed a small but reproducible protection of Jurkat cells from apoptosis induced by serum deprivation (p < 0.05), while the combination of Tat plus 100 nM WT significantly (p < 0.05) increased the percentage of apoptosis with respect to cells left untreated or treated with Tat alone. Taken together, these data suggest that the anti-apoptotic activity of low concentrations of Tat protein on Jurkat cells is mediated by a PI 3-kinase/Akt pathway.
Borgatti
P
P
Institute of Human Anatomy, University of Ferrara, Italy.
Zauli
G
G
Colamussi
M L
ML
Gibellini
D
D
Previati
M
M
Cantley
L L
LL
Capitani
S
S
D064413:3-Phosphoinositide-Dependent Protein Kinases; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D015496:CD4-Positive T-Lymphocytes / Q000201:enzymology* / Q000821:virology; D004789:Enzyme Activation / Q000187:drug effects; D005110:Extracellular Space / Q000201:enzymology / Q000821:virology*; D015696:Gene Products, tat / Q000502:physiology*; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000187:drug effects; D018613:Microscopy, Confocal; D019869:Phosphatidylinositol 3-Kinases / Q000302:isolation & purification / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt
D064413:3-Phosphoinositide-Dependent Protein Kinases; D015696:Gene Products, tat; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; C494918:AKT1 protein, human; C578562:PDPK1 protein, human