Regulation of cytochrome P4501B1 (CYP1B1) in mouse embryo fibroblast (C3H10T1/2) cells by protein kinase C (PKC).
The effects of co-treatment of C3H10T1/2 (10T1/2) cells with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 12-O-tetradecanoylphorbol-13-acetate (TPA) on the expression of the novel cytochrome P4501B1 (CYP1B1) were investigated. As monitored by CYP1B1-catalyzed 7,12-dimethylbenzanthracene (DMBA) metabolism, TPA suppressed basal and TCDD-induced DMBA metabolism in a concentration-dependent manner, with a maximum inhibitory concentration of 100 nM. The suppression of CYP1B1 catalytic activity occurred at two time points during which protein kinase C (PKC) was activated and down-regulated in these cells as judged by analyses of cellular PKC content and PKC-inhibitor (chelerythrine chloride)-influenced suppression of CYP1B1 catalytic activity. Experiments in which TCDD and benzanthracene (BA)-induced DMBA metabolism were monitored in PKCbeta1-overexpressing 10T1/2 cells revealed that the suppression of CYP1B1 activity is a consequence of cellular PKC elevation. This suppression phenomenon could be accounted for by PKC-mediated suppression of TCDD-induced CYP1B1 mRNA and apoprotein and of nuclear translocation of the Ah-receptor. In contrast, the mitogen-activated protein kinase (MAPK) proteins ERKs 1 and 2 were stimulated by TCDD under conditions in which PKC was activated. Collectively, our results suggest that PKC participates in the regulation of CYP1B1 in 10T1/2 cells, positively by directly suppressing the Ah-receptor signaling pathway, followed by an indirect or negative activation of the MAPK signaling pathway.
Ikegwuonu
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FI
Department of Pharmacology, University of Wisconsin Medical School, Madison 53706, USA.
Christou
M
M
Jefcoate
C R
CR
D015127:9,10-Dimethyl-1,2-benzanthracene / Q000378:metabolism; D000470:Alkaloids; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D053119:Benzophenanthridines; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002478:Cells, Cultured; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D004622:Embryo, Mammalian; D004789:Enzyme Activation; D004790:Enzyme Induction; D005786:Gene Expression Regulation; D051379:Mice; D008809:Mice, Inbred C3H; D010617:Phenanthridines; D000072317:Polychlorinated Dibenzodioxins; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D013755:Tetradecanoylphorbol Acetate
D000470:Alkaloids; D053119:Benzophenanthridines; D010617:Phenanthridines; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D015127:9,10-Dimethyl-1,2-benzanthracene; D003577:Cytochrome P-450 Enzyme System; C016299:chelerythrine; D001189:Aryl Hydrocarbon Hydroxylases; C585498:Cyp1b1 protein, mouse; D065633:Cytochrome P-450 CYP1B1; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D013755:Tetradecanoylphorbol Acetate