title: Phosphatidylinositol 3-kinase activity is not essential for CD28 costimulatory activity in Jurkat T cells: studies with a selective inhibitor, wortmannin.
abstract: The interaction of CD28 with its counter-receptor, B7-1 (CD 80), on antigen-presenting cells induces a co-signal in T cells required to promote antigen-dependent interleukin-2 (IL-2) production and to prevent clonal anergy. CD28 stimulation causes both protein-tyrosine kinase and phosphatidylinositol3-kinase (PI3-K) activation, suggesting a possible role for these enzyme activities in CD28 co-signal transduction. Here, we investigate the effect of wortmannin, a selective and irreversible PI3-K inhibitor on CD28 co-signaling events in the Jurkat T cell line. Wortmannin added to cell cultures partially inhibits CD28-induced tyrosine phosphorylation of the putative p110 catalytic subunit of PI3-K, but does not block CD28-induced association of the p85 PI3-K regulatory subunit with the CD28 receptor. Wortmannin inhibits in a dose-dependent manner both total cellular PI3-K activity and CD28-induced receptor-associated PI3-K activity. Wortmannin (1 microM) inhibits cellular PI3-K activity by 90% with complete inhibition achieved at 10 microM. The inhibitory effect of wortmannin on cellular PI3-K activity is prolonged ( > 18 h), suggesting that the drug is not readily metabolized by Jurkat T cells. Wortmannin, at concentrations that blocked PI3-K activity, fails to inhibit the synergistic effect of CD28 on IL-2 secretion in the presence of phorbol 12-myristate 13-acetate and ionomycin. These data demonstrate that CD28-induced signaling events other than the activation of PI3-K catalytic activity contribute to the control of IL-2 secretion.
authors.affiliation: Department of Veterans Affairs Medical Center, Amarillo, TX.
authors.forename: Y
authors.initials: Y
authors.lastname: Lu
authors.forename: C A
authors.initials: CA
authors.lastname: Phillips
authors.forename: J M
authors.initials: JM
authors.lastname: Trevillyan
mesh_terms: D000730:Androstadienes / Q000494:pharmacology*; D018106:CD28 Antigens / Q000502:physiology*; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis; D019869:Phosphatidylinositol 3-Kinases; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000502:physiology*; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D018106:CD28 Antigens; D007376:Interleukin-2; D014443:Tyrosine; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011505:Protein-Tyrosine Kinases; D000077191:Wortmannin