Cyclosporin A inhibits T cell receptor-induced interleukin-2 synthesis of human T lymphocytes by selectively preventing a transmembrane signal transduction pathway leading to sustained activation of a protein kinase C isoenzyme, protein kinase C-beta.
Stimulation of human peripheral blood lymphocytes via T cell receptor/CD3 complex resulted in a bimodal activation of protein kinase(s) C (PKC). Within 10 min of stimulation PKC-alpha was translocated to, and thus activated in, the plasma membranes of human lymphocytes, followed by a fast dissociation of this isotype from the plasma membrane. This short term activation and translocation PKC-alpha proved to be cyclosporin A (CsA) insensitive. After 90 min of stimulation PKC-beta was translocated to and remained bound to the plasma membranes for up to 4 h. Preincubation of human lymphocytes with 200 ng/ml CsA specifically and completely abolished the sustained activation of PKC-beta. Neither the phorbol ester-induced direct activation of PKC nor the specific activity of the plasma membrane-bound enzyme was influenced by CsA, suggesting that a signal transduction pathway leading to sustained activation of PKC-beta was influenced by the immunosuppressive agent. In fact, CsA inhibited, in a concentration-dependent manner, the activation of lysophosphatid acyltransferase-catalyzed elevated incorporation of cis-polyunsaturated fatty acids into plasma membrane phospholipids. While interleukin-2 (IL-2) synthesis and cellular proliferation were completely inhibited by 200 ng/ml CsA in BMA 030- or BMA 031-stimulated cells, expression of high-affinity IL-2 receptors was not influenced by the immunosuppressive drug. These results suggest that synthesis and expression of high-affinity IL-2 receptors might be regulated by a signal-transducing pathway involving activation and translocation of PKC-alpha. Lysophosphatid acyltransferase-catalyzed incorporation of cis-polyunsaturated fatty acids might represent another mechanism of signal transduction implicated in the activation and translocation of PKC-beta, which is specifically inhibited by CsA. Neutralization of PKC-beta by introducing anti-PKC-beta antibodies prevented IL-2 synthesis and proliferation in stimulated human lymphocytes. The results suggest a possible link between activation of PKC-beta and regulation of IL-2 synthesis in activated human lymphocytes. Thus, inhibition of the activation and translocation of PKC-beta by CsA may result in inhibition of IL-2 gene expression in human lymphocytes.
Szamel
M
M
Institute of Molecular Pharmacology, Medical School Hannover, FRG.
Bartels
F
F
Resch
K
K
D000818:Animals; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis*; D007527:Isoenzymes / Q000378:metabolism*; D008213:Lymphocyte Activation / Q000187:drug effects; D008563:Membrane Lipids / Q000378:metabolism; D051379:Mice; D010743:Phospholipids / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects*; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism
D005231:Fatty Acids, Unsaturated; D007376:Interleukin-2; D007527:Isoenzymes; D008563:Membrane Lipids; D010743:Phospholipids; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D016572:Cyclosporine; D011493:Protein Kinase C