Phosphatidylinositol 3-kinase activity is not essential for CD28 costimulatory activity in Jurkat T cells: studies with a selective inhibitor, wortmannin
✍ Scribed by Yiling Lu; Catherine A. Phillips; James M. Trevillyan
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 681 KB
- Volume
- 25
- Category
- Article
- ISSN
- 0014-2980
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✦ Synopsis
The interaction of CD28 with its counter-receptor, B7-1 (CD 80), on antigenpresenting cells induces a co-signal in T cells required to promote antigendependent interleukin-2 (IL-2) production and to prevent clonal anergy. CD28 stimulation causes both protein-tyrosine kinase and phosphatidylinositol3kinase (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 CD28induced tyrosine phosphorylation of the putative pllO 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 p ~) inhibits cellular PU-K activity by 90 % with complete inhibition achieved at 10 p ~. The inhibitory effect of wortmannin on cellular PD-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.