Cloning and Tissue Distribution of a Novel Human Cytochrome P450 of the CYP3A Subfamily, CYP3A43

doi:10.1006/bbrc.2001.4505

Biochemical and Biophysical Research Communications

Volume 281, Issue 5, 16 March 2001, Pages 1349-1355

https://doi.org/10.1006/bbrc.2001.4505 Get rights and content

Abstract

On the basis of the detection of an expressed sequence tag (‘EST’) similar to the human cytochrome P450 3A4 cDNA, we have identified a novel member of the human cytochrome P450 3A subfamily. The coding region is 1512-bp long and shares 84, 83, and 82% sequence identity on the cDNA level with CYP3A4, 3A5, and 3A7, respectively, with a corresponding amino acid identity of 76, 76, and 71%. Quantitative real time based mRNA analysis revealed CYP3A43 expression levels at about 0.1% of CYP3A4 and 2% of CYP3A5 in the liver, with significant expression in 70% of the livers examined. Gene specific PCR of cDNA from extrahepatic tissues showed, with the exception of the testis, only low levels of CYP3A43 expression. The CYP3A43 cDNA was heterologously expressed in yeast, COS-1 cells, mouse hepatic H2.35 cells and in human embryonic kidney (HEK) 293 cells, but in contrast to CYP3A4 which was formed in all cell types, no detectable CYP3A43 protein was produced. This indicates a nonfunctional protein or specific conditions required for proper folding. It is concluded that CYP3A43 mRNA is expressed mainly in liver and testis and that the protein would not contribute significantly to human drug metabolism.

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Although there is little information about the function of the rs15524 SNP or rs4646450 SNP, further investigations would provide more evidence help to elucidate the mechanisms by which the allele variants significantly affect the Tac pharmacokinetics. CYP3A4 was polymorphically expressed, while at least 40 SNPs have been identified to date [10]. Several CYP3A4 SNPs relating to Tac pharmacokinetics have been investigated in previous studies [13,23,24].
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^☆: A preliminary presentation of part of this paper has been made in an abstract at the 13th International meeting on Microsomes and Drug Oxidations, Stresa, Italy, July 10–14, 2000, Abstract No 354, p. 198.

^☆☆: The sequence reported in this paper has been deposited in GenBank under Accession No. AF337813.

^★: Abbreviations used: CYP, cytochrome P450; bp, base pair(s); PCR, polymerase chain reaction; EST, expressed sequence tag; huPO, human acidic ribosomal phosphoprotein; RACE, rapid amplification of cDNA ends.

¹: To whom correspondence should be addressed at Division of Molecular Toxicology, IMM, Karolinska Institutet, Box 210, SE-171 77 Stockholm, Sweden. Fax: +46-8-33 73 27. E-mail: [email protected].

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Regular ArticleCloning and Tissue Distribution of a Novel Human Cytochrome P450 of the CYP3A Subfamily, CYP3A43☆,☆☆,★

Abstract

J. Biol. Chem.

Arch. Biochem. Biophys.

Toxicology

Biochem. Biophys. Res. Commun.

Gene

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

Arch. Biochem. Biophys.

Clin. Pharmacokinet.

J. Pharmacol. Exp. Ther.

Biochemistry

J. Clin. Invest.

Regular Article
Cloning and Tissue Distribution of a Novel Human Cytochrome P450 of the CYP3A Subfamily, CYP3A43☆,☆☆,★