Perturbation of the expression of the catalytic subunit C alpha of cyclic AMP-dependent protein kinase inhibits TCR-triggered secretion of IL-2 by T helper hybridoma cells

Abstract

The role of cAMP-dependent protein kinase (PKA) in the regulation of TCR-triggered IL-2 secretion was studied by transfecting T hybridoma cells with cDNA encoding the inhibitory regulatory subunit (RI alpha) of PKA with mutations in cAMP-binding sites (RI alpha(m)) or by pretreating T cells with catalytic subunit-alpha (C alpha) antisense mRNA oligonucleotides. Transfected RI alpha(m) was expected to compete with endogenous regulatory subunits and to irreversibly inactivate the catalytic subunit in RI alpha(m)-C alpha complexes. It was shown that C alpha and RI alpha are the major PKA subunits in T cells, thereby justifying the choice of RI alpha(m) and C alpha antisense oligos to modulate PKA activity in T lymphocytes. Perturbation of the expression of PKA subunits by RI alpha(m) resulted in transfectants with 1) no changes in basal PKA activity but inhibited cAMP-inducible PKA activity or 2) inhibited basal PKA activity but unaffected cAMP-inducible PKA activity. Transfectants with inhibited basal PKA activity had changed (inhibited) levels of TCR-triggered IL-2 production. The anti-C alpha antisense mRNA oligomers also inhibited basal PKA activity and TCR-triggered production of IL-2. The experiments described here and recently reported studies of the effects of C alpha inactivation on CTL effector functions and IFN-gamma secretion suggest that basal PKA activity could be required for the propagation of TCR-triggered signals needed for lymphokine secretion by T cells.