Comparison of phorbol ester/calcium ionophore and phytohemagglutinin-induced signaling in human T lymphocytes. Demonstration of interleukin 2-independent transferrin receptor gene expression.
The proliferation of human T lymphocytes is regulated, in part, by the coordinated expression of genes encoding T cell growth factor (interleukin 2 (IL-2), IL-2 receptors, and transferrin receptors (TFR). We examined the time course of accumulation of mRNA for these genes in T cells stimulated with the phorbol ester, phorbol 12,13-dibutyrate (PDB) and the calcium ionophore, ionomycin, and compared their expression to T cells stimulated with phytohemagglutinin. In cells treated with PDB/ionomycin, maximum expression was observed at 3 hr for IL-2 mRNA and at 6 hr for TFR mRNA, whereas the level of IL-2 receptor mRNA reached a peak 24 to 48 hr after stimulation. In phytohemagglutinin-stimulated T cells IL-2 mRNA was detectable within 3 hr but peaked later at 12 hr; the level of IL-2 receptor mRNA similarly peaked 24 to 48 hr later. Accumulation of TFR mRNA in phytohemagglutinin-stimulated T cells, however, was not detectable at 6 hr and reached a peak only between 12 to 24 hr. The early accumulation of TFR mRNA in PDB/ionomycin-stimulated T cells seemed, in part, independent of the interaction of IL-2 with its own receptor, because TFR mRNA was detectable as early as 1 hr after stimulation and addition of cycloheximide before addition of PDB/ionomycin did not abolish the PDB/ionomycin-induced accumulation of TFR mRNA. In addition, either PDB or ionomycin used alone induced the expression of TFR mRNA but not IL-2 mRNA. These results indicated that the combination of PDB/ionomycin accelerated the expression of IL-2 and TFR genes in T cells compared to phytohemagglutinin and triggered an IL-2-independent pathway for the induction of TFR mRNA.
D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004357:Drug Synergism; D004987:Ethers / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D007158:Immunologic Techniques; D007376:Interleukin-2 / Q000235:genetics; D015759:Ionomycin; D008213:Lymphocyte Activation / Q000187:drug effects*; D015240:Phorbol 12,13-Dibutyrate; D010703:Phorbol Esters / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D011971:Receptors, Immunologic / Q000235:genetics; D015375:Receptors, Interleukin-2; D011990:Receptors, Transferrin / Q000235:genetics* / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*; D013997:Time Factors; D014168:Transferrin / Q000502:physiology*
D004987:Ethers; D007376:Interleukin-2; D010703:Phorbol Esters; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D011990:Receptors, Transferrin; D014168:Transferrin; D015240:Phorbol 12,13-Dibutyrate; D015759:Ionomycin; D003513:Cycloheximide