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Activation of the Protein Kinase A Increases the DNA‐Binding and Transcriptional Activity of c‐Rel in T Cells
Author(s) -
LAHDENPOHJA N.,
HENTTINEN T.,
HURME M.
Publication year - 1996
Publication title -
scandinavian journal of immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.934
H-Index - 88
eISSN - 1365-3083
pISSN - 0300-9475
DOI - 10.1046/j.1365-3083.1996.d01-268.x
Subject(s) - jurkat cells , microbiology and biotechnology , electrophoretic mobility shift assay , protein kinase a , kinase , transcription factor , biology , protein subunit , transfection , phosphorylation , gene , biochemistry , t cell , immune system , immunology
Cyclic AMP (cAMP)‐dependent protein kinase A (PKA) is known to have both negative and positive effects on the activation mechanisms of T lymphocytes. The authors have analysed the effect of increased cAMP on the activation of NF‐κB transcription factor. This factor controls the expression of several genes (e.g. IL‐2 and IL‐2 receptor) involved in the activation and proliferation of T cells. The authors found that elevation of intracellular cAMP in Jurkat T leukaemia cells activated with phorbol ester (PDBu)/calcium ionophore (A23187) increased the DNA‐binding of NF‐κB as detected by the electrophoretic mobility shift assay (EMSA). Analysis of the subunit composition of the DNA‐binding complex indicated that the amount of c‐Rel was enhanced while RelA was decreased. Analysis of the effect of elevated cAMP on the degradation of IκB‐α and IκB‐β did not reveal an essential change in degradation kinetics of these inhibitor proteins. The elevation of cAMP did not increase the synthesis of c‐Rel, but it enhanced the nuclear localization of this protein. Transfection of Jurkat cells with a plasmid kB/TK10‐CAT indicated that the increased DNA‐binding of c‐Rel containing complexes seen in EMSA was also functional. These data imply that the strong and long‐lasting c‐Rel nuclear localization and DNA‐binding induced by protein kinase A is not due to increased c‐Rel synthesis or enhanced degradation of the IκB inhibitors. Therefore, a direct phosphorylation of the c‐Rel protein is the most plausible explanation for these observations. Taken together, these results suggest that cAMP is able to regulate the expression of NF‐κB‐dependent genes in T cells by modifying the composition and subunit activity of NF‐κB.