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

The role of cAMP-dependent protein kinase (PKA) in the regulation of T CR-triggered IL-2 secretion was studied by transfecting T hybridoma ce lls with cDNA encoding the inhibitory regulatory subunit (RI alpha) of PKA with mutations in cAMP-binding sites (RI alpha m) or by pretreati ng T cells with catalytic subunit-alpha (C alpha) antisense mRNA oligo nucleotides. Transfected RI alpha m was expected to compete with endog enous regulatory subunits and to irreversibly inactivate the catalytic subunit in RI alpha m-C alpha complexes. It was shown that C alpha an d RI alpha are the major PKA subunits in T cells, thereby justifying t he choice of RI alpha m and C alpha antisense oligos to modulate PKA a ctivity in T lymphocytes. Perturbation of the expression of PKA subuni ts by RI alpha m resulted in transfectants with 1) no changes in basal PKA activity but inhibited cAMP-inducible PKA activity or 2) inhibite d basal PKA activity but unaffected cAMP-inducible PKA activity, Trans fectants with inhibited basal PKA activity had changed (inhibited) lev els of TCR-triggered IL-2 production, The anti-C alpha antisense mRNA oligomers also inhibited basal PKA activity and TCR-triggered producti on of IL-2. The experiments described here and recently reported studi es of the effects of C alpha inactivation on CTL effector functions an d IFN-gamma secretion suggest that basal PKA activity could be require d for the propagation of TCR-triggered signals needed for lymphokine s ecretion by T cells.