Identification of a rat adrenal cytochrome P450 active in polycyclic hydrocarbon metabolism as rat CYP1B1. Demonstration of a unique tissue-specific pattern of hormonal and aryl hydrocarbon receptor-linked regulation.
Antibodies against a novel adrenocorticotropic hormone-inducible cytochrome P450 (P450RAP), responsible for polycyclic aromatic hydrocarbon metabolism in rat adrenal microsomes (Otto, S., Bhattacharyya, K.K., and Jefcoate, C.R. (1992) Endocrinology 131, 3067-3076), identified a cDNA clone encoding a partial cytochrome P450 sequence from a rat adrenal cDNA library. Rescreening a second cDNA library yielded several clones up to 5.0 kilobases (kb) encoding a 1629-base pair open reading frame. The deduced amino acid sequence (543 residues) matched completely with five peptides cleaved from P450RAP. The amino acid sequence of P450RAP is 92% identical to a 2,3,7,8-tetrachlorodibenzo-p-dioxin-inducible CYP1B1, cloned from mouse C3H10T1/2 (10T1/2) embryo fibroblast cells (Savas, U., Bhattacharyya, K. K., Christou, M., Alexander, D.L., and Jefcoate, C. R. (1994) J. Biol. Chem. 269, 14905-14911), which shows nearly the same characteristics in polycyclic aromatic hydrocarbon metabolism. The available 5'- and 3'-noncoding regions show, respectively, 93 and 83% sequence identity. We conclude that P450RAP protein is encoded by a rat CYP1B1 gene orthologous to the mouse CYP1B1 gene. Alignment of rat CYP1B1 amino acid sequences with rat CYP1A1 (39% identical) indicated eight regions of high identity for each (60-78%), interspersed by extensive regions of less than 30% similarity. The CYP1B1 cDNAs hybridize a 5.2-kb mRNA in rat adrenals, consistent with the length of the longest clones and the mRNA recognized in 10T1/2 cells. CYP1B1 mRNA was elevated by a 2-day adrenocorticotropic hormone treatment but much less than CYP11A1 (cytochrome P450 side chain cleavage) mRNA (2-fold versus 4-fold). The lower levels of the 5.2-kb mRNA in other steroidogenic cells (ovary) was consistent with the amount of immunodetectable CYP1B1 protein and, unlike the adrenal, expression in the ovary was stimulated 5-fold by beta-naphthoflavone, an aryl hydrocarbon receptor agonist, in parallel with CYP1A1 induction. In several other tissues (liver > lung > uterus >> kidney), CYP1B1 mRNA and protein were constitutively undetectable but highly induced by beta-naphthoflavone, although at much lower levels than CYP1A1. Rat CYP1B1, therefore, exhibits regulation through hormonal signaling and the aryl hydrocarbon receptor in a cell-specific manner.
Bhattacharyya
K K
KK
Department of Pharmacology, University of Wisconsin Medical School, Madison 53706, USA.
Brake
P B
PB
Eltom
S E
SE
Otto
S A
SA
Jefcoate
C R
CR
D000311:Adrenal Glands / Q000201:enzymology* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001483:Base Sequence; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D017931:DNA Primers; D006706:Homeostasis; D006801:Humans; D051379:Mice; D008861:Microsomes / Q000201:enzymology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D016133:Polymerase Chain Reaction; D051381:Rats; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
D017931:DNA Primers; D010446:Peptide Fragments; D018336:Receptors, Aryl Hydrocarbon; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; C585498:Cyp1b1 protein, mouse; C585499:Cyp1b1 protein, rat; D065633:Cytochrome P-450 CYP1B1