PROTEIN-KINASE ACTIVITY-DEPENDENT INHIBITION OF UROKINASE-TYPE PLASMINOGEN-ACTIVATOR GENE-TRANSCRIPTION BY CYCLIC-AMP IN HUMAN PRE-B LYMPHOMA CELL-LINE RC-K8

We investigated the effects of cAMP on the urokinase-type plasminogen activator (uPA) production in human pre-B lymphoma cell line RC-K8 tha t is consistently secreting uPA in the conditioned medium. Both Bt(2)c AMP and PGE1 inhibited the uPA accumulation in a dose-dependent manner . Northern blot analysis and nuclear run-on assay revealed that uPA ge ne transcription was repressed by Bt,cAMP and the repression was negat ed by inhibition of de novo protein synthesis by cycloheximide. Pretre atment with H89 (N-[2(p-bromocin-namyl-amino) ethyl]-5-isoquinoline su lfonamide), a specific cAMP-dependent protein kinase (PKA) inhibitor, strongly inhibited both the PKA activation and the supression of uPA m RNA accumulation induced by cAMP. H85 (N-[2-(N-formyl-p-chlorocinnamyl -amino) ethyl]-5-isoquinoline sulfonamide), which closely resembles H8 9 in its chemical structure but is not a selective inhibitor of PKA, s howed little effect on the regulation of uPA gene regulation by Bt(2)c AMP. These results suggest that cAMP represses uPA gene transcription in human pre-B lymphoma cells through PKA pathway and in which de novo protein synthesis is required.