Activation of T-cells by bryostatins: induction of the IL-2 receptor gene transcription and down-modulation of surface receptors.
Bryostatins are macrocyclic lactones isolated from the marine bryozoan Bugula neritina. They are currently evaluated for putative antineoplastic activity. Bryostatins bind and activate protein kinase C (PK-C), the cellular receptor for the phorbol ester, and elicit PK-D-dependent cellular functions. Such functions include the expression of the interleukin-2 receptor (IL-2R). Northern blot hybridization with a human IL-2R and an IL-2 cDNA showed that bryostatin 1 (bryo 1), like the phorbol ester, PMA, activates the IL-2R gene. Activation with bryo 1 or PMA in the presence of a calcium ionophore, A23187, increased IL-2 message. These findings indicate that calcium mobilization is necessary for bryo 1 or PMA induced IL-2 gene expression. Unlike PMA, bryo 1 did not cause a vigorous proliferative response of T-lymphocytes unless A23187 was added to the cultures. A bryostatin congener, bryo 13, was inactive in the above assays. Short-term treatment of T-cells with bryo 1 and PMA resulted in an equivalent down-regulation of surface CD3 and CD4 receptors without affecting the CD8 receptor. Bryo 1 or PMA mediated expression of surface IL-2R and T-cell proliferation induced by bryo 1 or PMA were sensitive to inhibition by the PK-C antagonists staurosporine (Sts) and H-7. In contrast, CD4 and CD3 down-regulation were resistant to H-7, but could be blocked by Sts, although the Sts concentration required to block bryo 1 or PMA-induced down-modulation was 2.5-fold higher than required to inhibit IL-2R expression and T-cell proliferation. These results indicate that bryostatins activate T-cell through PK-C.
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Johns Hopkins School of Medicine, Baltimore, Maryland.
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Adler
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May
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Hess
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D000954:Antigens, Surface / Q000276:immunology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D054713:Bryostatins; D017252:CD3 Complex / Q000276:immunology; D015704:CD4 Antigens / Q000276:immunology; D015536:Down-Regulation; D015870:Gene Expression; D006801:Humans; D007783:Lactones / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects*; D018942:Macrolides; D011493:Protein Kinase C / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D015375:Receptors, Interleukin-2 / Q000235:genetics; D013268:Stimulation, Chemical; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000954:Antigens, Surface; D000970:Antineoplastic Agents; D054713:Bryostatins; D017252:CD3 Complex; D015704:CD4 Antigens; D007783:Lactones; D018942:Macrolides; D011948:Receptors, Antigen, T-Cell; D015375:Receptors, Interleukin-2; C046785:bryostatin 1; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate