Cyclic AMP synergy with Ca2+ for production of IFN-gamma by a cytolytic T cell clone is post-transcriptional.
PGE2 or products increasing the intracellular concentration of cAMP (cAMP)i) had opposite effects on the induction of IFN-gamma in a CTL clone, depending on the inducing agent. Activation via the TCR was inhibited, whereas induction by the Ca2+ ionophore ionomycin was enhanced in the presence of agents increasing (cAMP)i. Synergy between Ca2(+)-dependent and cAMP-dependent pathways was independent of the activation of protein kinase C (PKC). Low levels of IFN-gamma mRNA could be detected transiently after induction with ionomycin alone, whereas simultaneous induction with agents increasing (cAMP)i led to enhanced levels of IFN-gamma mRNA detectable up to 12 h. No IFN-gamma mRNA was detected when the CTL were activated with (cAMP)i-increasing agents alone or with PKC-activating agents such as PMA, suggesting that the transcriptional activation of the IFN-gamma gene was strictly dependent on the Ca2(+)-mediated and cyclosporin A-dependent event. Analyses of IFN-gamma mRNA transcription by "run-on" experiments on nuclei isolated after activation of the CTL indicated that the Ca2+ signal alone induces maximal transcription of the IFN-gamma gene, which is not increased by either PKC activation or an increase in cAMP, but that further processing or stabilization of the IFN-gamma precursor or mature mRNA require an additional signal, provided either via a PKC or via a PKA activation pathway. The data also suggest that a combination of inflammatory products leading to an increase in (Ca2+)i and to an increase in (cAMP)i may bypass the usually stringent control of T cell activation by the TCR/CD3 complex.
Kaldy
P
P
Centre d'Immunologie INSERM-CNRS de Marseille-Luminy, France.
Schmitt-Verhulst
A M
AM
D000818:Animals; D015152:Blotting, Northern; D002118:Calcium / Q000494:pharmacology*; D002460:Cell Line; D000242:Cyclic AMP / Q000502:physiology*; D003524:Cyclosporins / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology; D004357:Drug Synergism; D015870:Gene Expression / Q000187:drug effects; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000096:biosynthesis* / Q000235:genetics; D015759:Ionomycin / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D011493:Protein Kinase C / Q000502:physiology; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects
D003524:Cyclosporins; D011948:Receptors, Antigen, T-Cell; D015759:Ionomycin; D007371:Interferon-gamma; D000242:Cyclic AMP; D011493:Protein Kinase C; D015232:Dinoprostone; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium