Multiple novel nonsynonymous CYP2B6 gene polymorphisms in Caucasians:: Demonstration of phenotypic null alleles
Multiple novel nonsynonymous CYP2B6 gene polymorphisms in Caucasians:: Demonstration of phenotypic null alleles
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DOI：
10.1124/jpet.104.068973
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发表时间：
2004-10-01
影响因子：
3.5
通讯作者：
Zanger, UM
中科院分区：
文献类型：
--
作者：
Lang, T;Klein, K;Zanger, UM
人微粒体细胞色素 P450（CYP2B6）参与多种临床重要药物的生物转化。通过对选定的白种人 DNA 样本中人类 CYP2B6 基因编码区的完整序列分析，我们鉴定了五个新的错义突变 62A > T（外显子 1 中的 Q21L）、136A > G（外显子 1 中的 M46V）、12820G > A（外显子 2 中的 G99E）、13076G > A（外显子 3 中的 R140Q）和21388T > A（外显子 8 中的 I391N）。还观察到最近描述但功能未表征的变体 13072A > G (K139E)。单倍型分析表明存在至少六个编码蛋白质变体 CYP2B6.10 (Q21L、R22C)、CYP2B6.11 (M46V)、CYP2B6.12 (G99E)、CYP2B6.13 (K139E、Q172H、K262R)、CYP2B6.14 ( R140Q) 和 CYP2B6.15 (I391N)。 COS-1 细胞中的异源表达揭示了 CYP2B6.1（野生型）和 CYP2B6.10 的 CYP2B6 脱辅基蛋白和安非他酮羟化酶活性水平相当，而所有其他变体均表现出表达和/或功能降低。尽管存在残留蛋白质，但 M46V、G99E 和 I391N 三个氨基酸变化导致几乎无法测量（M46V）或无法检测（G99E 和 I391N）的酶活性。 K139E的改变导致蛋白质表达完全消失；结果，没有检测到任何功能。重组杆状病毒在昆虫细胞中的表达证实了这些结果，并证明这些蛋白质变体中实际上不存在掺入的血红素。在白种人研究人群中，四种极低或无效活性变体 M46V、G99E、K139E 和 I391N 的集体等位基因频率为 2.6%。这些数据进一步深入了解 CYP2B6 的遗传变异性，并证明该基因中存在表型无效等位基因。
The human microsomal cytochrome P450, CYP2B6, is involved in the biotransformation of several clinically important drugs. By complete sequence analysis of the human CYP2B6 gene coding regions in selected Caucasian DNA samples, we identified the five novel missense mutations 62A > T (Q21L in exon 1), 136A > G (M46V in exon 1), 12820G > A (G99E in exon 2), 13076G > A (R140Q in exon 3), and 21388T > A (I391N in exon 8). The recently described but functionally uncharacterized variant 13072A > G (K139E) was also observed. Haplotype analysis indicated the presence of at least six novel alleles that code for the protein variants CYP2B6.10 (Q21L, R22C), CYP2B6.11 ( M46V), CYP2B6.12 ( G99E), CYP2B6.13 ( K139E, Q172H, K262R), CYP2B6.14 ( R140Q), and CYP2B6.15 ( I391N). Heterologous expression in COS-1 cells revealed comparable levels of CYP2B6 apoprotein and bupropion hydroxylase activity for CYP2B6.1 (wild type) and CYP2B6.10, whereas all other variants exhibited reduced expression and/or function. The three amino acid changes M46V, G99E, and I391N resulted in almost unmeasurable ( M46V) or undetectable ( G99E and I391N) enzyme activity, despite the presence of residual protein. The K139E change led to completely abolished protein expression; as a consequence, no function was detected. Expression in insect cells by recombinant baculoviruses confirmed these results and demonstrated the virtual absence of incorporated heme in these protein variants. The collective allele frequency of the four very low or null activity variants M46V, G99E, K139E, and I391N was 2.6% in a Caucasian study population. These data provide further insight into the genetic variability of CYP2B6 and demonstrate the existence of phenotypic null alleles in this gene.