PKC and PKA are antagonistic partners in the NF-AT transactivation pathway of primary mouse CD3 T lymphocytes

We here investigate the crosstalk of PKC and PKA signaling during primary CD3 T-lymphocyte activation using pharmacologic inhibitors and activators in combination with our established panel of PKC isotype–deficient mouse T cells in vitro. PKC and PKA inversely affect the CD3/ CD28-induced IL-2 expression, whereas other PKC isotypes are dispensable in this signaling pathway. Gene ablation of PKC selectively results in a profound reduction of IL-2 production; however, complete abrogation of IL-2 production in these PKC / T cells was achieved only by simultaneous coactivation of the cAMP/PKA pathway in CD3 T cells. Conversely, the reduced IL-2 production in PKC inhibitor–treated T cells can be rescued by inhibition of the cAMP/PKA pathway in wild-type but not in PKC / T cells. Mechanistically, the cAMP/PKA and PKC pathways converge at the level of NF-AT, as shown by DNA binding analysis. The combined increase in PKA and decrease in PKC activity leads to an enhanced inhibition of nuclear NF-AT translocation. This PKC /PKA crosstalk significantly affects neither the NFB, the AP-1, nor the CREB pathways. Taken together, this opposite effect between the positive PKC and the negative cAMP/ PKA signaling pathways appears rate limiting for NF-AT transactivation and IL-2 secretion responses of CD3 T lymphocytes. (Blood. 2006;107:4841-4848)