title: Polycyclic aromatic hydrocarbon o-quinones inhibit the activity of the catalytic fragment of protein kinase C.
abstract: Polycyclic aromatic hydrocarbons (PAHs) require metabolic activation to exert their carcinogenic effects. PAH trans-dihydrodiol proximate carcinogens are oxidized by aldo-keto reductases (AKRs) to their corresponding reactive and redox-active o-quinones which may have the properties of initiators and promoters. To determine whether these o-quinones target protein kinase C (PKC), their effects on human recombinant PKCalpha and PKCdelta and the catalytic fragment of rat brain PKC were determined. Naphthalene-1,2-dione (NP-1,2-dione), benzo[a]pyrene-7,8-dione (BP-7,8-dione), and 7,12-dimethylbenz[a]anthracene-3,4-dione (DMBA-3,4-dione) potently inhibited (IC(50) values 3-5 microM) the basal and stimulated activity of the holoenzymes PKCalpha and PKCdelta in a dose-dependent manner. Inhibition of PKC by BP-7,8-dione was observed irrespective of whether PKCalpha activity was stimulated with phorbol 12-myristate 13-acetate (PMA), phosphatidylserine (PS), or Ca(2+) or whether PKCdelta was stimulated with phorbol 12-myristate 13-acetate (PMA) or phosphatidylserine (PS), suggesting that the inhibition was not cofactor-specific. All three quinones inhibited the catalytic fragment of PKC in vitro, yielding identical IC(50) values (3-5 microM), indicating that they interact with the catalytic domain of PKC rather than the cofactor/activator sites. In contrast, no effect on either the holoenzyme or the catalytic fragment was observed with the corresponding PAH trans-dihydrodiols, indicating that inhibition was o-quinone-specific. Irreversible inhibition of the catalytic fragment of PKC was observed since activity could not be restored by dialysis, suggesting that arylation of the fragment had occurred. NP-1,2-dione and BP-7,8-dione also suppressed PKC activity in human breast cancer MCF-7 cell lysates which express PKCalpha, -beta, -delta, -epsilon, -iota, and -lambda isozymes. These data suggest that PAH o-quinones, generated by AKRs, may affect cellular signaling through suppression of the activity of PKC isoforms.
authors.affiliation: Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6084, USA.
authors.forename: Deshan
authors.initials: D
authors.lastname: Yu
authors.forename: Marcelo G
authors.initials: MG
authors.lastname: Kazanietz
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Harvey
authors.forename: Trevor M
authors.initials: TM
authors.lastname: Penning
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000494:pharmacology; D001580:Benzopyrenes / Q000494:pharmacology; D001711:Biotransformation; D020134:Catalytic Domain / Q000187:drug effects*; D004101:Dihydroxydihydrobenzopyrenes / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D020035:Holoenzymes / Q000378:metabolism; D006801:Humans; D009281:Naphthalenes / Q000494:pharmacology; D009284:Naphthols / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D010446:Peptide Fragments / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011809:Quinones / Q000737:chemistry / Q000494:pharmacology*; D013347:Subcellular Fractions / Q000187:drug effects / Q000201:enzymology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology
chemical_list: D001580:Benzopyrenes; D004101:Dihydroxydihydrobenzopyrenes; D004791:Enzyme Inhibitors; D020035:Holoenzymes; D009281:Naphthalenes; D009284:Naphthols; D010446:Peptide Fragments; D011084:Polycyclic Aromatic Hydrocarbons; D011809:Quinones; C107171:naphthalene-1,2-dione; C017228:benzo(a)pyrene 7,8-dihydrodiol; D015127:9,10-Dimethyl-1,2-benzanthracene; C076588:benzo(a)pyrene-7,8-dione; C042334:1,2-dihydroxy-1,2-dihydronaphthalene; D011493:Protein Kinase C