Protein kinase activity-dependent inhibition of urokinase-type plasminogen activator gene transcription by cyclic AMP in human pre-B lymphoma cell line RC-K8

Abstract

We investigated the effects of cAMP on the urokinase-type plasminogen activator (uPA) production in human pre-B lymphoma cell line RC-K8 that is consistently secreting uPA in the conditioned medium. Both Bt 2cAMP and PGE1 inhibited the uPA accumulation in a dose-dependent manner. Northern blot analysis and nuclear run-on assay revealed that uPA gene transcription was repressed by Bt 2cAMP and the repression was negated by inhibition of de novo protein synthesis by cycloheximide. Pretreatment with H89 (N-[2-(p-bromocinnamyl-amino) ethyl]-5-isoquinoline sulfonamide), a specific cAMP-dependent protein kinase (PKA) inhibitor, strongly inhibited both the PKA activation and the supression of uPA mRNA accumulation induced by cAMP. H85 (N-[2-(N-formyl-p-chlorocinnamyl-amino) ethyl]-5-isoquinoline sulfonamide), which closely resembles H89 in its chemical structure but is not a selective inhibitor of PKA, showed little effect on the regulation of uPA gene regulation by Bt 2cAMP. 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.