Consequences of POR mutations and polymorphisms.
Consequences of POR mutations and polymorphisms.
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DOI：
10.1016/j.mce.2010.10.022
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发表时间：
2011-04-10
影响因子：
4.1
通讯作者：
Giacomini KM
中科院分区：
文献类型：
--
作者：
Miller WL;Agrawal V;Sandee D;Tee MK;Huang N;Choi JH;Morrissey K;Giacomini KM
P450氧化还原酶（POR）将电子从NADPH转运到所有微粒体细胞色素P450酶，包括类固醇生成P450c17、P450c21和P450aro。严重的POR突变A287 P（欧洲人）和R457 H（日本人）导致Antley-Bixler骨骼畸形综合征（ABS）加上类固醇生成受损（导致生殖器异常），但ABS的基础尚不清楚。我们已经表征了约40种POR变体的活性，表明基于P450c17活性的测定，而不是细胞色素c测定，与临床表型相关。人类POR基因是高度多态性的：A503V序列变异体，其使P450c17活性降低至约60%，在约28%的人类等位基因上发现。在-152位点的启动子多态性（约8%的亚洲人和约13%的高加索人）使转录活性降低一半。对35个POR突变体的筛选表明，大多数突变体缺乏P450c17或细胞色素c活性，也缺乏支持EOMCC的CYP1A2和CYP2C19代谢的活性（荧光非药物底物），尽管存在一些显著差异：Q153R导致ABS，与P450c17的活性约为野生型的30%，但与CYP1A2的活性为野生型的144%，与CYP2C19的活性为野生型的284%。POR变体对代谢近50%临床使用药物的CYP3A4的影响用多种临床相关药物底物进行了检查，表明A287 P和R457 H显著降低药物代谢，而A503 V则损害药物代谢。活性的程度可以随着所测定的药物底物而变化，因为药物可以影响P450的构象。POR可能是类固醇生成和药物代谢中遗传变异的重要贡献者。
P450 oxidoreductase (POR) transports electrons from NADPH to all microsomal cytochrome P450 enzymes, including steroidogenic P450c17, P450c21 and P450aro. Severe POR mutations A287P (in Europeans) and R457H (in Japanese) cause the Antley-Bixler skeletal malformation syndrome (ABS) plus impaired steroidogenesis (causing genital anomalies), but the basis of ABS is unclear. We have characterized the activities of ~40 POR variants, showing that assays based on P450c17 activities, but not cytochrome c assays, correlate with the clinical phenotype. The human POR gene is highly polymorphic: the A503V sequence variant, which decreases P450c17 activities to ~60%, is found on ~28% of human alleles. A promoter polymorphism (~8% of Asians and ~13% of Caucasians) at −152 reduces transcriptional activity by half. Screening of 35 POR variants showed that most mutants lacking activity with P450c17 or cytochrome c also lacked activity to support CYP1A2 and CYP2C19 metabolism of EOMCC (a fluorogenic non-drug substrate), although there were some remarkable differences: Q153R causes ABS and has ~30% of wild-type activity with P450c17 but had 144% of WT activity with CYP1A2 and 284% with CYP2C19. The effects of POR variants on CYP3A4, which metabolizes nearly 50% of clinically used drugs, was examined with multiple, clinically-relevant drug substrates, showing that A287P and R457H dramatically reduce drug metabolism, and that A503V variably impairs drug metabolism. The degree of activity can vary with the drug substrate assayed, as the drugs can influence the conformation of the P450. POR is probably an important contributor to genetic variation in both steroidogenesis and drug metabolism.