Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
???displayArticle.abstract??? Cytochrome P450 family 1 (CYP1) includes four subfamilies of enzymes: CYP1A, CYP1B, CYP1C, and CYP1D. In many vertebrates, CYP1A, 1B, and 1C expression is induced by agonists of the aryl hydrocarbon receptor, including toxic contaminants such as chlorinated dioxins, coplanar chlorinated biphenyls, and polynuclear aromatic hydrocarbons. Assessed at the level of mRNA, protein, or enzyme activity, CYP1s (especially CYP1As) represent potent and popular biomarkers of contaminant exposure in aquatic vertebrates. Alkylated resorufins are synthetic substrates used to detect, quantify, and describe catalytic activities of cytochrome P450s. The ability to oxidize specific resorufin-based substrates can distinguish the catalytic activities of individual CYP1s. Xenopus laevis, the African clawed frog, is the most widely employed amphibian model in aquatic toxicology, yet the number, inducibility, and activities of CYP1s have not been systematically characterized in this species. Here we report the cloning of cDNAs encoding two new CYP1 family members, X. laevis CYP1B and CYP1C, along with an integrated assessment of the induction of alkyloxyuresorufin-O-dealkylase (AROD) activities and mRNA expression of four known X. laevis CYP1s: CYP1A6, CYP1A7, CYP1B, and CYP1C. Using XLK-WG, an X. laevis kidneyepithelial cell line, we determined that EROD (ethoxyresorufin substrate) and MROD (methoxyresorufin) were both induced 3000- to 5000-fold following 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) exposure up to 250 nM, while BROD (benzyloxyresorufin) and PROD (pentyloxyresorufin) activity was not detectable regardless of TCDD treatment. TCDD induced CYP1A6 and CYP1A7 mRNAs by 2-3 orders of magnitude, while CYP1B and CYP1C were unchanged. The more potent AHR agonist, FICZ (6-formylindolo[3,2-b]carbazole), induced CYP1B up to 10-fold at concentrations between 0.1 and 250 nM, while CYP1C induction was less than 3-fold. CYP1B mRNA showed the highest constitutive mRNA expression, 5- to 75-fold greater than the other CYP1 transcripts. Taken together, these results suggest that CYP1A6 and CYP1A7 perform the bulk of EROD and MROD activities we observed in these cells. The ability of each X. laevis CYP1 to catalyze oxidation of individual resorufin substrates remains to be determined. Correlating CYP1 mRNA and induced AROD activity is a significant step toward clarifying the biochemical meaning of these biomarkers and the roles of CYP1 enzymes in X. laevis. The cell culture approach represents an important complement to the long standing use of frog embryos and tadpoles in toxicological studies, providing a well suited model system for determining the molecular mechanisms underlying the regulation of these important biomarkers of contaminant exposure.
Burke,
Differential effects of phenobarbitone and 3-methylcholanthrene induction on the hepatic microsomal metabolism and cytochrome P-450-binding of phenoxazone and a homologous series of its n-alkyl ethers (alkoxyresorufins).
1983, Pubmed
Burke,
Differential effects of phenobarbitone and 3-methylcholanthrene induction on the hepatic microsomal metabolism and cytochrome P-450-binding of phenoxazone and a homologous series of its n-alkyl ethers (alkoxyresorufins).
1983,
Pubmed Burke,
Cytochrome P450 specificities of alkoxyresorufin O-dealkylation in human and rat liver.
1994,
Pubmed Crespi,
Development of a human lymphoblastoid cell line constitutively expressing human CYP1B1 cDNA: substrate specificity with model substrates and promutagens.
1997,
Pubmed Degitz,
Progress towards development of an amphibian-based thyroid screening assay using Xenopus laevis. Organismal and thyroidal responses to the model compounds 6-propylthiouracil, methimazole, and thyroxine.
2005,
Pubmed
,
Xenbase Diani-Moore,
Sunlight generates multiple tryptophan photoproducts eliciting high efficacy CYP1A induction in chick hepatocytes and in vivo.
2006,
Pubmed Fujita,
Molecular cloning and sequence analysis of cDNAs coding for 3-methylcholanthrene-inducible cytochromes P450 in Xenopus laevis liver.
1999,
Pubmed
,
Xenbase Garrison,
Species-specific recombinant cell lines as bioassay systems for the detection of 2,3,7,8-tetrachlorodibenzo-p-dioxin-like chemicals.
1996,
Pubmed Godard,
The new vertebrate CYP1C family: cloning of new subfamily members and phylogenetic analysis.
2005,
Pubmed Goldstone,
Cytochrome P450 1 genes in early deuterostomes (tunicates and sea urchins) and vertebrates (chicken and frog): origin and diversification of the CYP1 gene family.
2007,
Pubmed
,
Xenbase Goldstone,
Cytochrome P450 1D1: a novel CYP1A-related gene that is not transcriptionally activated by PCB126 or TCDD.
2009,
Pubmed Goldstone,
A revised evolutionary history of the CYP1A subfamily: gene duplication, gene conversion, and positive selection.
2006,
Pubmed Gotoh,
Substrate recognition sites in cytochrome P450 family 2 (CYP2) proteins inferred from comparative analyses of amino acid and coding nucleotide sequences.
1992,
Pubmed Gutleb,
Delayed effects of pre- and early-life time exposure to polychlorinated biphenyls on tadpoles of two amphibian species (Xenopus laevis and Rana temporaria).
1999,
Pubmed
,
Xenbase Hahn,
Biomarkers and bioassays for detecting dioxin-like compounds in the marine environment.
2002,
Pubmed Hestermann,
Relative contributions of affinity and intrinsic efficacy to aryl hydrocarbon receptor ligand potency.
2000,
Pubmed Hoegg,
Phylogenetic timing of the fish-specific genome duplication correlates with the diversification of teleost fish.
2004,
Pubmed Hughes,
Evolution of duplicate genes in a tetraploid animal, Xenopus laevis.
1993,
Pubmed
,
Xenbase Jelaso,
Gene expression patterns predict exposure to PCBs in developing Xenopus laevis tadpoles.
2003,
Pubmed
,
Xenbase Jönsson,
Cytochrome p450 1 genes in birds: evolutionary relationships and transcription profiles in chicken and Japanese quail embryos.
2011,
Pubmed Jönsson,
New CYP1 genes in the frog Xenopus (Silurana) tropicalis: induction patterns and effects of AHR agonists during development.
2011,
Pubmed
,
Xenbase Jönsson,
Basal and 3,3',4,4',5-pentachlorobiphenyl-induced expression of cytochrome P450 1A, 1B and 1C genes in zebrafish.
2007,
Pubmed Kennedy,
Simultaneous measurement of cytochrome P4501A catalytic activity and total protein concentration with a fluorescence plate reader.
1994,
Pubmed Kubota,
Alkoxyresorufin (methoxy-, ethoxy-, pentoxy- and benzyloxyresorufin) O-dealkylase activities by in vitro-expressed cytochrome P450 1A4 and 1A5 from common cormorant (Phalacrocorax carbo).
2009,
Pubmed Laub,
Responsiveness of a Xenopus laevis cell line to the aryl hydrocarbon receptor ligands 6-formylindolo[3,2-b]carbazole (FICZ) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).
2010,
Pubmed
,
Xenbase Lavine,
Aryl hydrocarbon receptors in the frog Xenopus laevis: two AhR1 paralogs exhibit low affinity for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).
2005,
Pubmed
,
Xenbase Liu,
The effect of reciprocal active site mutations in human cytochromes P450 1A1 and 1A2 on alkoxyresorufin metabolism.
2004,
Pubmed Livak,
Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method.
2001,
Pubmed Martin,
Xgrip109: a gamma tubulin-associated protein with an essential role in gamma tubulin ring complex (gammaTuRC) assembly and centrosome function.
1998,
Pubmed
,
Xenbase Meyer,
From 2R to 3R: evidence for a fish-specific genome duplication (FSGD).
2005,
Pubmed Morrison,
Molecular cloning of CYP1A from the estuarine fish Fundulus heteroclitus and phylogenetic analysis of CYP1 genes: update with new sequences.
1998,
Pubmed Morrison,
Identification of cytochrome P-450 1A (CYP1A) genes from two teleost fish, toadfish (Opsanus tau) and scup (Stenotomus chrysops), and phylogenetic analysis of CYP1A genes.
1995,
Pubmed Oberg,
Identification of the tryptophan photoproduct 6-formylindolo[3,2-b]carbazole, in cell culture medium, as a factor that controls the background aryl hydrocarbon receptor activity.
2005,
Pubmed Okey,
An aryl hydrocarbon receptor odyssey to the shores of toxicology: the Deichmann Lecture, International Congress of Toxicology-XI.
2007,
Pubmed Råbergh,
Differential expression of two CYP1A genes in rainbow trout (Oncorhynchys mykiss).
2000,
Pubmed Rifkind,
Purification and biochemical characterization of two major cytochrome P-450 isoforms induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin in chick embryo liver.
1994,
Pubmed Rowatt,
ARNT gene multiplicity in amphibians: characterization of ARNT2 from the frog Xenopus laevis.
2003,
Pubmed
,
Xenbase Saitou,
The neighbor-joining method: a new method for reconstructing phylogenetic trees.
1987,
Pubmed Scornaienchi,
Functional differences in the cytochrome P450 1 family enzymes from zebrafish (Danio rerio) using heterologously expressed proteins.
2010,
Pubmed Sinclair,
Identification of CYP1A5 as the CYP1A enzyme mainly responsible for uroporphyrinogen oxidation induced by AH receptor ligands in chicken liver and kidney.
1997,
Pubmed Thompson,
The CLUSTAL_X windows interface: flexible strategies for multiple sequence alignment aided by quality analysis tools.
1997,
Pubmed Uno,
CYP1D1, pseudogenized in human, is expressed and encodes a functional drug-metabolizing enzyme in cynomolgus monkey.
2011,
Pubmed Van den Berg,
Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife.
1998,
Pubmed Verbrugge,
Catalytic and immunochemical properties of hepatic cytochrome P450 1A in three avian species treated with beta-naphthoflavone or isosafrole.
2001,
Pubmed Wincent,
The suggested physiologic aryl hydrocarbon receptor activator and cytochrome P4501 substrate 6-formylindolo[3,2-b]carbazole is present in humans.
2009,
Pubmed Zanette,
New cytochrome P450 1B1, 1C2 and 1D1 genes in the killifish Fundulus heteroclitus: Basal expression and response of five killifish CYP1s to the AHR agonist PCB126.
2009,
Pubmed
