Interleukin-1-induced signaling in T-cells. Evidence for the involvement of phosphatases PP1 and PP2A in regulating protein kinase C-mediated protein phosphorylation and interleukin-2 synthesis.

Abstract

Binding of human recombinant interleukin-1 beta (IL-1 beta) to the cell surface receptors of EL-4 6.1 murine T-cells results in enhanced phosphorylation of several cellular proteins. Staurosporine abolished the enhanced phosphorylation in response to IL-1 for some of these proteins, suggesting that protein kinase C (PKC) was at least partially responsible. PKC-beta was translocated from the cytosol to the plasma membrane between 2 and 15 min after IL-1 binding. Activation of PKC-beta was enhanced by the protein phosphatase inhibitor okadaic acid. In fact, okadaic acid inhibited dephosphorylation of the PKC-specific peptide GS (Pro-Leu-Ser-Arg-Thr-Leu-Ser-Val-Ala-Ala-Lys-Lys). On the other hand, okadaic acid also led to elevation of IL-1-induced trans/autophosphorylation of PKC-beta. Accordingly, IL-1 induction of interleukin-2 synthesis was markedly enhanced by okadaic acid in EL-4 cells. These data suggest that activation of PKC-beta contributes to enhanced phosphorylation of cellular proteins in IL-1-treated cells and support the importance of protein phosphorylation and dephosphorylation in the regulation of IL-1-induced IL-2 synthesis in EL-4 6.1 T-cells.