title: Selective inhibition of cyclic AMP-dependent protein kinase by isoquinoline derivatives.
abstract: A large series of isoquinoline derivatives was synthesised including derivatives of isoquinoline, isoquinolino[3,4-c]furazan, 1,2-dihydro-1-oxoisoquinoline, 6-oxopyrimido[1,2-d]isoquinoline, benzo[c][1,8]-naphthyridine, pyrazino[2,3-c]isoquinoline and benzimidazo[2,1-a]isoquinoline as well as further structurally related isoquinoline derivatives and pyrido-2,3-furazans. Representatives of all of these classes of isoquinolines are potent and selective inhibitors of the cyclic AMP-dependent protein kinase (PKA) catalytic subunit (cAK) from rat liver. The most effective cAK inhibitors are a series of 1,3-di-substituted and 1,3,4-tri-substituted isoquinolines (IC50 values 30-50 nM) (compounds A1, A2, A3, A4 and A5) and 2-ethylcarboxy-3-amino-5,6-dihydro-6-oxobenzo[c] [1,8]naphthyridine (E1) (IC50 0.08 microM). Compounds A1-A5 inhibit cAK in a fashion that is competitive with respect to ATP as substrate. The isoquinoline inhibitors A1-A5 are ineffective or very poor inhibitors of wheat embryo Ca(2+)-dependent protein kinase (CDPK) and rat brain Ca(2+)-dependent protein kinase C (PKC), chicken gizzard myosin light chain kinase (MLCK) and potato tuber cyclic nucleotide-binding phosphatase (Pase). E1 is a moderately effective inhibitor of CDPK and PKC (IC50 values 30 and 61 microM, respectively). The bisisoquinoline-1(2H)-one compound B7 inhibits cAK, CDPK, PKC and MLCK (IC50 values 8, 95, 24 and 7 microM, respectively) as does J1 [2-(p-bromophenyl)pyrrolo-[2,3-c]isoquinoline-5(4H)-one] (IC50 values 2, 50, 44 and 7 microM, respectively). The very potent isoquinoline-derived cAK inhibitors found here involve substitution of the N-containing isoquinoline ring system and these inhibitors show high specificity for cAK.
authors.affiliation: School of Biochemistry, La Trobe University, Bundoora, Victoria, Australia.
authors.forename: Z X
authors.initials: ZX
authors.lastname: Lu
authors.forename: N H
authors.initials: NH
authors.lastname: Quazi
authors.forename: L W
authors.initials: LW
authors.lastname: Deady
authors.forename: G M
authors.initials: GM
authors.lastname: Polya
mesh_terms: D000818:Animals; D002645:Chickens; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007546:Isoquinolines / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D009219:Myosin-Light-Chain Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D013329:Structure-Activity Relationship
chemical_list: D004791:Enzyme Inhibitors; D007546:Isoquinolines; D017868:Cyclic AMP-Dependent Protein Kinases; D009219:Myosin-Light-Chain Kinase