Protein phosphorylation mediated by IL-2/IL-2 receptor beta-chain interaction.
We previously found that IL-2 rapidly induced protein phosphorylation of a 67-kDa (pp67) and four 63-kDa (pp63s) cellular proteins in various T cells. Here, we show that the IL-2-stimulated phosphorylation is mediated by the IL-2R beta-chain composed of the high affinity IL-2R, and induced by activation of Ca2+/phospholipid-dependent protein kinase C (PKC). The IL-2-stimulated phosphorylation was always observed in various T cell lines bearing high affinity IL-2R, but never observed in cells which express only low affinity IL-2R consisted of alpha-chain alone. When the expression of high affinity IL-2R was modified by anti-IL-2R mAb for reducing the affinity to 8- to 10-fold lower without affecting the sites of IL-2R, the effective dose of IL-2 on phosphorylation of pp67 increased 8 to 10 times. When cells were treated with pronase, approximately 95% sites of low affinity IL-2R were selectively decreased, but the IL-2 dose dependency for pp67 phosphorylation was little affected. These data exactly suggest that protein phosphorylation in response to IL-2 such as pp67 and pp63s, is mediated by high affinity but not low affinity IL-2R. Furthermore, the IL-2-stimulated phosphorylation of these proteins was also observed in MLA 144 cells which express only low affinity IL-2R consisting of beta-chain alone. In addition, various phorbol esters and tumor promoters, which activate PKC, were also demonstrated to induce the phosphorylation of a pp67 and pp63s in these T cell lines. Therefore, the present study suggests that IL-2/IL-2R beta-chain interaction triggers the phosphorylation of pp67 and pp63s, where the PKC may have an important role.
D000818:Animals; D000911:Antibodies, Monoclonal / Q000502:physiology; D002460:Cell Line; D006801:Humans; D006922:Hylobates; D007376:Interleukin-2 / Q000378:metabolism / Q000502:physiology*; D008970:Molecular Weight; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011402:Pronase / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism; D011971:Receptors, Immunologic / Q000276:immunology / Q000502:physiology*; D015375:Receptors, Interleukin-2; D013601:T-Lymphocytes / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D007376:Interleukin-2; D010750:Phosphoproteins; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D011493:Protein Kinase C; D011402:Pronase