RT Journal Article SR Electronic T1 FUNCTIONAL CHARACTERIZATION OF FIVE NOVEL CYP2C8 VARIANTS, G171S, R186X, R186G, K247R, AND K383N, FOUND IN A JAPANESE POPULATION JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 630 OP 636 DO 10.1124/dmd.105.003830 VO 33 IS 5 A1 Hiroyuki Hichiya A1 Toshiko Tanaka-Kagawa A1 Akiko Soyama A1 Hideto Jinno A1 Satoru Koyano A1 Noriko Katori A1 Erika Matsushima A1 Shigehisa Uchiyama A1 Hiroshi Tokunaga A1 Hideo Kimura A1 Narihiro Minami A1 Masaaki Katoh A1 Kenji Sugai A1 Yu-ichi Goto A1 Tomohide Tamura A1 Noboru Yamamoto A1 Yuichiro Ohe A1 Hideo Kunitoh A1 Hiroshi Nokihara A1 Teruhiko Yoshida A1 Hironobu Minami A1 Nagahiro Saijo A1 Masanori Ando A1 Shogo Ozawa A1 Yoshiro Saito A1 Jun-ichi Sawada YR 2005 UL http://dmd.aspetjournals.org/content/33/5/630.abstract AB 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 6α-hydroxylase activity, and intracellular localization. The prematurely terminated R186X variant was undetectable by Western blotting and inactive toward paclitaxel 6α-hydroxylation. The G171S, K247R, and K383N variants exhibited properties similar to those of the wild-type CYP2C8. Paclitaxel 6α-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. The American Society for Pharmacology and Experimental Therapeutics