Functional Characterization of Five Novel Cyp2c8 Variants, G171s, R186x, R186g, K247r, and K383n, Found in a Japanese Population

Abstract

ABSTRACT:Cytochrome P450 2C8 is one of the primary enzymes responsible for the metabolism of a wide range of drugs such as paclitaxel, cerivastatin, and amiodarone. We have sequenced the CYP2C8 gene from 201 Japanese subjects and found five novel nonsynonymous single nucleotide polymorphisms (SNPs): 511G>A (G171S), 556C>T (R186X; X represents the translational stop codon), 556C>G (R186G), 740A>G (K247R), and 1149G>T (K383N), with the allele frequency of 0.0025. The CYP2C8 variants were heterologously expressed in COS-1 cells and functionally characterized in terms of expression level, paclitaxel 6␣-hydroxylase activity, and intracellular localization. The prematurely terminated R186X variant was undetectable by Western blotting and inactive toward paclitaxel 6␣-hydroxylation. The G171S, K247R, and K383N variants exhibited properties similar to those of the wild-type CYP2C8. Paclitaxel 6␣-hydroxylase activity of the R186G transfectant was only 10 to 20% that of wild-type CYP2C8. Furthermore, the R186G variant displayed a lower level of protein expression in comparison to the wild type, which was restored by the addition of a proteasome inhibitor (MG-132; Z-Leu-Leu-Leu-aldehyde). The reduced CO-difference spectral analysis using recombinant proteins from an insect cell/baculovirus system revealed that the R186G variant has a minor peak at 420 nm in addition to the characteristic Soret peak at 450 nm, suggesting the existence of improperly folded protein. These results indicate that the novel CYP2C8 SNPs, 556C>T (R186X) and 556C>G (R186G), could influence the metabolism of CYP2C8 substrates such as paclitaxel and cerivastatin.

Discovery of a Novel Allelic Variant of CYP2C8, CYP2C8*11, in Asian Populations and Its Clinical Effect on the Rosiglitazone Disposition In Vivo

“…Allelic frequency of CYP2C8*11 was evaluated in the different ethnic populations and was found to be at 0.3% in Koreans (n ϭ 450), 0.14% in Chinese (n ϭ 348), and 0.5% in Vietnamese (n ϭ 100), but no subject with this novel variant was identified from 93 African-American and 100 white subjects ( Table 2). None of the Korean subjects had CYP2C8*7 and *8 (n ϭ 450), although these variants were reported to occur at low frequency (one individual each of 201 subjects) in Japanese populations (Hichiya et al, 2005) (Table 2). The haplotype map of the CYP2C8 locus was generated using Haploview (version 4.1) from 17 variants detected in the present studies, which resulted in one LD block (Fig.…”

A Long-Standing Mystery Solved: The Formation of 3-Hydroxydesloratadine Is Catalyzed by CYP2C8 But Prior Glucuronidation of Desloratadine by UDP-Glucuronosyltransferase 2B10 Is an Obligatory Requirement

“…Our results suggest that CYP2C8 and/or UGT2B10 polymorphism may be responsible for the poor metabolizer phenotype. A large number of CYP2C8 genetic polymorphisms have been identified, with CYP2C8*2, CYP2C8*3, CYP2C8*4, CYP2C8*8, and CYP2C8*14 alleles shown to have decreased functional activity (Dai et al, 2001;Bahadur et al, 2002;Hichiya et al, 2005;Gao et al, 2010;Hanioka et al, 2010;Jiang et al, 2011). However, little is currently known about UGT2B10 polymorphisms, although the UGT2B10*2 allele has been shown to correspond to a functional decrease in nicotine and cotinine glucuronide formation (Chen et al, 2007).…”

Structural and functional insights into CYP2C8.3: A genetic polymorph of cytochrome P450 2C8

“…To date, up to ten polymorphs of CYP2C8, designated as CYP2C8.2 to CYP2C8. 10 and an unclassified form temporarily named CYP2C8 P404A, have been reported [15][16][17][18]. CYP2C8.3, one of the most common variant alleles of CYP2C8 is expressed most commonly in Caucasians (allele frequency, 23%), and is quite rare in Black populations (allele frequency, 2%), and appears to be absent in the Japanese population.…”