51
|
Why boys will be boys: two pathways of fetal testicular androgen biosynthesis are needed for male sexual differentiation. Am J Hum Genet 2011; 89:201-18. [PMID: 21802064 DOI: 10.1016/j.ajhg.2011.06.009] [Citation(s) in RCA: 185] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Revised: 06/15/2011] [Accepted: 06/22/2011] [Indexed: 01/17/2023] Open
Abstract
Human sexual determination is initiated by a cascade of genes that lead to the development of the fetal gonad. Whereas development of the female external genitalia does not require fetal ovarian hormones, male genital development requires the action of testicular testosterone and its more potent derivative dihydrotestosterone (DHT). The "classic" biosynthetic pathway from cholesterol to testosterone in the testis and the subsequent conversion of testosterone to DHT in genital skin is well established. Recently, an alternative pathway leading to DHT has been described in marsupials, but its potential importance to human development is unclear. AKR1C2 is an enzyme that participates in the alternative but not the classic pathway. Using a candidate gene approach, we identified AKR1C2 mutations with sex-limited recessive inheritance in four 46,XY individuals with disordered sexual development (DSD). Analysis of the inheritance of microsatellite markers excluded other candidate loci. Affected individuals had moderate to severe undervirilization at birth; when recreated by site-directed mutagenesis and expressed in bacteria, the mutant AKR1C2 had diminished but not absent catalytic activities. The 46,XY DSD individuals also carry a mutation causing aberrant splicing in AKR1C4, which encodes an enzyme with similar activity. This suggests a mode of inheritance where the severity of the developmental defect depends on the number of mutations in the two genes. An unrelated 46,XY DSD patient carried AKR1C2 mutations on both alleles, confirming the essential role of AKR1C2 and corroborating the hypothesis that both the classic and alternative pathways of testicular androgen biosynthesis are needed for normal human male sexual differentiation.
Collapse
|
52
|
Mutations of human cytochrome P450 reductase differentially modulate heme oxygenase-1 activity and oligomerization. Arch Biochem Biophys 2011; 513:42-50. [PMID: 21741353 DOI: 10.1016/j.abb.2011.06.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 06/14/2011] [Accepted: 06/16/2011] [Indexed: 01/26/2023]
Abstract
Genetic variations in POR, encoding NADPH-cytochrome P450 oxidoreductase (CYPOR), can diminish the function of numerous cytochromes P450, and also have the potential to block degradation of heme by heme oxygenase-1 (HO-1). Purified full-length human CYPOR, HO-1, and biliverdin reductase were reconstituted in lipid vesicles and assayed for NADPH-dependent conversion of heme to bilirubin. Naturally-occurring human CYPOR variants queried were: WT, A115V, Y181D, P228L, M263V, A287P, R457H, Y459H, and V492E. All CYPOR variants exhibited decreased bilirubin production relative to WT, with a lower apparent affinity of the CYPOR-HO-1 complex than WT. Addition of FMN or FAD partially restored the activities of Y181D, Y459H, and V492E. When mixed with WT CYPOR, only the Y181D CYPOR variant inhibited heme degradation by sequestering HO-1, whereas Y459H and V492E were unable to inhibit HO-1 activity suggesting that CYPOR variants might have differential binding affinities with redox partners. Titrating the CYPOR-HO-1 complex revealed that the optimal CYPOR:HO-1 ratio for activity was 1:2, lending evidence in support of productive HO-1 oligomerization, with higher ratios of CYPOR:HO-1 showing decreased activity. In conclusion, human POR mutations, shown to impact P450 activities, also result in varying degrees of diminished HO-1 activity, which may further complicate CYPOR deficiency.
Collapse
|
53
|
Polusani SR, Kar R, Riquelme MA, Masters BS, Panda SP. Regulation of gap junction function and Connexin 43 expression by cytochrome P450 oxidoreductase (CYPOR). Biochem Biophys Res Commun 2011; 411:490-5. [PMID: 21726529 DOI: 10.1016/j.bbrc.2011.06.132] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Accepted: 06/18/2011] [Indexed: 11/28/2022]
Abstract
Cytochrome P450 oxidoreductase (CYPOR) is a microsomal electron-transferring enzyme containing both FAD and FMN as co-factors, which provides the reducing equivalents to various redox partners, such as cytochromes P450 (CYPs), heme oxygenase (HO), cytochrome b(5) and squalene monooxygenase. Human patients with severe forms of CYPOR mutation show bone defects such as cranio- and humeroradial synostoses and long bone fractures, known as Antley-Bixler-like Syndrome (ABS). To elucidate the role of CYPOR in bone, we knocked-down CYPOR in multiple osteoblast cell lines using RNAi technology. In this study, knock-down of CYPOR decreased the expression of Connexin 43 (Cx43), known to play a critical role in bone formation, modeling, and remodeling. Knock-down of CYPOR also decreased Gap Junction Intercellular Communication (GJIC) and hemichannel activity. Promoter luciferase assays revealed that the decrease in expression of Cx43 in CYPOR knock-down cells was due to transcriptional repression. Primary osteoblasts isolated from bone specific Por knock-down mice calvariae confirmed the findings in the cell lines. Taken together, our study provides novel insights into the regulation of gap junction function by CYPOR and suggests that Cx43 may play an important role(s) in CYPOR-mediated bone defects seen in patients.
Collapse
Affiliation(s)
- Srikanth R Polusani
- The University of Texas Health Science Center at San Antonio, Department of Biochemistry, San Antonio, TX 78229, United States
| | | | | | | | | |
Collapse
|
54
|
Keber R, Motaln H, Wagner KD, Debeljak N, Rassoulzadegan M, Ačimovič J, Rozman D, Horvat S. Mouse knockout of the cholesterogenic cytochrome P450 lanosterol 14alpha-demethylase (Cyp51) resembles Antley-Bixler syndrome. J Biol Chem 2011; 286:29086-29097. [PMID: 21705796 DOI: 10.1074/jbc.m111.253245] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Antley-Bixler syndrome (ABS) represents a group of heterogeneous disorders characterized by skeletal, cardiac, and urogenital abnormalities that have frequently been associated with mutations in fibroblast growth factor receptor 2 or cytochrome P450 reductase genes. In some ABS patients, reduced activity of the cholesterogenic cytochrome P450 CYP51A1, an ortholog of the mouse CYP51, and accumulation of lanosterol and 24,25-dihydrolanosterol has been reported, but the role of CYP51A1 in the ABS etiology has remained obscure. To test whether Cyp51 could be involved in generating an ABS-like phenotype, a mouse knock-out model was developed that exhibited several prenatal ABS-like features leading to lethality at embryonic day 15. Cyp51(-/-) mice had no functional Cyp51 mRNA and no immunodetectable CYP51 protein. The two CYP51 enzyme substrates (lanosterol and 24,25-dihydrolanosterol) were markedly accumulated. Cholesterol precursors downstream of the CYP51 enzymatic step were not detected, indicating that the targeting in this study blocked de novo cholesterol synthesis. This was reflected in the up-regulation of 10 cholesterol synthesis genes, with the exception of 7-dehydrocholesterol reductase. Lethality was ascribed to heart failure due to hypoplasia, ventricle septum, and epicardial and vasculogenesis defects, suggesting that Cyp51 deficiency was involved in heart development and coronary vessel formation. As the most likely downstream molecular mechanisms, alterations were identified in the sonic hedgehog and retinoic acid signaling pathways. Cyp51 knock-out mice provide evidence that Cyp51 is essential for embryogenesis and present a potential animal model for studying ABS syndrome in humans.
Collapse
Affiliation(s)
- Rok Keber
- Department of Animal Science, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Helena Motaln
- Department of Animal Science, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia; Department of Genetic Toxicology and Cancer Biology, National Institute of Biology, 1000 Ljubljana, Slovenia
| | - Kay D Wagner
- INSERM U907, Parc Valrose, Nice, France; Université de Nice, Sophia-Antipolis, Parc Valrose, Nice, France
| | - Nataša Debeljak
- Institute of Biochemistry, Centre for Functional Genomics and Bio-Chips, Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Minoo Rassoulzadegan
- Université de Nice, Sophia-Antipolis, Parc Valrose, Nice, France; Centre de Biochimie, INSERM U636, Parc Valrose, Nice, France
| | - Jure Ačimovič
- Institute of Biochemistry, Centre for Functional Genomics and Bio-Chips, Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Damjana Rozman
- Institute of Biochemistry, Centre for Functional Genomics and Bio-Chips, Faculty of Medicine, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Simon Horvat
- Department of Animal Science, Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia; National Institute of Chemistry, 1000 Ljubljana, Slovenia and.
| |
Collapse
|
55
|
Miller WL, Agrawal V, Sandee D, Tee MK, Huang N, Choi JH, Morrissey K, Giacomini KM. Consequences of POR mutations and polymorphisms. Mol Cell Endocrinol 2011; 336:174-9. [PMID: 21070833 PMCID: PMC4632974 DOI: 10.1016/j.mce.2010.10.022] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 10/29/2010] [Accepted: 10/30/2010] [Indexed: 01/23/2023]
Abstract
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.
Collapse
Affiliation(s)
- Walter L Miller
- Department of Pediatrics, University of California, San Francisco, San Francisco, CA 94143-0978, USA.
| | | | | | | | | | | | | | | |
Collapse
|
56
|
Tee MK, Huang N, Damm I, Miller WL. Transcriptional regulation of the human P450 oxidoreductase gene: hormonal regulation and influence of promoter polymorphisms. Mol Endocrinol 2011; 25:715-31. [PMID: 21393444 DOI: 10.1210/me.2010-0236] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
P450 oxidoreductase (POR) is the flavoprotein that acts as the obligatory electron donor to all microsomal P450 enzymes, including those involved in hepatic drug metabolism as well as three steroidogenic P450 enzymes. The untranslated first exon of human POR was located recently, permitting analysis of human POR transcription. Expression of deletional mutants containing up to 3193 bp of the human POR promoter in human adrenal NCI-H295A and liver Hep-G2 cells located the proximal promoter at -325/-1 bp from the untranslated exon. Common human POR polymorphisms at -208 and -173 had little influence on transcription, but the polymorphism at -152 reduced transcription significantly in both cell lines. EMSA and supershift assays identified binding of Smad3/Smad4 between -249 and -261 and binding of thyroid hormone receptor-β (TRβ) at -240/-245. Chromatin immunoprecipitation showed that Smad3, Smad4, TRα, TRβ, and estrogen receptor-α were bound between -374 and -149. Cotransfection of vectors for these transcription factors and POR promoter-reporter constructs into both cell types followed by hormonal treatment showed that T(3) exerts major tropic effects via TRβ, with TRα, estrogen receptor-α, Smad3, and Smad4 exerting lesser, modulatory effects. T(3) also increased POR mRNA in both cell lines. Thyroid hormone also is essential for rat liver POR expression but acts via different transcription factor complexes. These are the first data on human POR gene transcription, establishing roles for TRβ and Smad3/4 in its expression and indicating that the common polymorphism at -152 may play a role in genetic variation in steroid biosynthesis and drug metabolism.
Collapse
Affiliation(s)
- Meng Kian Tee
- Department of Pediatrics, University of California, San Francisco, San Francisco, California 94143-0978, USA
| | | | | | | |
Collapse
|
57
|
Idkowiak J, O'Riordan S, Reisch N, Malunowicz EM, Collins F, Kerstens MN, Köhler B, Graul-Neumann LM, Szarras-Czapnik M, Dattani M, Silink M, Shackleton CHL, Maiter D, Krone N, Arlt W. Pubertal presentation in seven patients with congenital adrenal hyperplasia due to P450 oxidoreductase deficiency. J Clin Endocrinol Metab 2011; 96:E453-62. [PMID: 21190981 PMCID: PMC3124345 DOI: 10.1210/jc.2010-1607] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Accepted: 11/16/2010] [Indexed: 01/02/2023]
Abstract
CONTEXT P450 oxidoreductase (POR) is a crucial electron donor to all microsomal P450 cytochrome (CYP) enzymes including 17α-hydroxylase (CYP17A1), 21-hydroxylase (CYP21A2) and P450 aromatase. Mutant POR causes congenital adrenal hyperplasia with combined glucocorticoid and sex steroid deficiency. P450 oxidoreductase deficiency (ORD) commonly presents neonatally, with disordered sex development in both sexes, skeletal malformations, and glucocorticoid deficiency. OBJECTIVE The aim of the study was to describe the clinical and biochemical characteristics of ORD during puberty. DESIGN Clinical, biochemical, and genetic assessment of seven ORD patients (five females, two males) presenting during puberty was conducted. RESULTS Predominant findings in females were incomplete pubertal development (four of five) and large ovarian cysts (five of five) prone to spontaneous rupture, in some only resolving after combined treatment with estrogen/progestin, GnRH superagonists, and glucocorticoids. Pubertal development in the two boys was more mildly affected, with some spontaneous progression. Urinary steroid profiling revealed combined CYP17A1 and CYP21A2 deficiencies indicative of ORD in all patients; all but one failed to mount an appropriate cortisol response to ACTH stimulation indicative of adrenal insufficiency. Diagnosis of ORD was confirmed by direct sequencing, demonstrating disease-causing POR mutations. CONCLUSION Delayed and disordered puberty can be the first sign leading to a diagnosis of ORD. Appropriate testosterone production during puberty in affected boys but manifest primary hypogonadism in girls with ORD may indicate that testicular steroidogenesis is less dependent on POR than adrenal and ovarian steroidogenesis. Ovarian cysts in pubertal girls may be driven not only by high gonadotropins but possibly also by impaired CYP51A1-mediated production of meiosis-activating sterols due to mutant POR.
Collapse
Affiliation(s)
- Jan Idkowiak
- Centre for Endocrinology, Diabetes and Metabolism, School of Clinical and Experimental Medicine, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
58
|
Effects of genetic variants of human P450 oxidoreductase on catalysis by CYP2D6 in vitro. Pharmacogenet Genomics 2011; 20:677-86. [PMID: 20940534 DOI: 10.1097/fpc.0b013e32833f4f9b] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVES Cytochrome P450 (P450) oxidoreductase (POR) donates electrons to all microsomal cytochrome P450s, including drug-metabolizing and steroidogenic enzymes. Severe POR mutations cause skeletal malformations and disordered steroidogenesis. The POR polymorphism A503V is found on approximately 28% of human alleles and decreases activities of CYP3A4 and steroidogenic CYP17, but not the activities of steroidogenic CYP21 or drug-metabolizing CYP1A2 and CYP2C19. CYP2D6 metabolizes about 25% of clinically used drugs; we assessed the capacity of POR variants to support the activities of human CYP2D6. METHODS N-27 forms of wildtype (WT), Q153R, A287P, R457H and A503V POR, and WT CYP2D6 were expressed in Escherichia coli. POR proteins in bacterial membranes were reconstituted with purified CYP2D6. Support of CYP2D6 was measured by metabolism of EOMCC (2H-1-benzopyran-3-carbonitrile,7-(ethoxy-methoxy)-2-oxo-(9Cl)), dextromethorphan and bufuralol. Michaelis constant (K(m)) and maximum velocity (V(max)) were determined in three triplicate experiments for each reaction; catalytic efficiency is expressed as V(max)/K(m). RESULTS Compared with WT POR, disease-causing POR mutants A287P and R457H supported no detectable CYP2D6 activity with EOMCC, but A287P supported approximately 25% activity with dextromethorphan and bufuralol. Q153R had increased function with CYP2D6 (128% with EOMCC, 198% with dextromethorphan, 153% with bufuralol). A503V supported decreased CYP2D6 activity: 85% with EOMCC, 62% with dextromethorphan and 53% with bufuralol. CONCLUSION POR variants have different effects depending on the substrate metabolized. Disease-causing POR mutations R457H and A287P had poor activities, suggesting that diminished drug metabolism should be considered in affected patients. The common A503V polymorphism impaired CYP2D6 activities with two commonly used drugs by 40-50%, potentially explaining some genetic variation in drug metabolism.
Collapse
|
59
|
Abstract
Antley-Bixler syndrome (ABS) is an exceptionally rare craniosynostosis syndrome characterized by radiohumeral synostosis present from the perinatal period. There is a wide spectrum of anomalies seen within ABS, and other features include midface hypoplasia; choanal stenosis or atresia; multiple joint contractures; visceral anomalies, particularly of the genitourinary system; and impaired steroidogenesis. The condition of ABS is curious in that mutations of 2 separate genes have been identified and that there seem to be subtle phenotypic differences between the 2 genotypes. Mutations of the P450 oxidoreductase gene have been reported in those patients with genital anomalies and/or impaired steroidogenesis, and the S351C mutation of the fibroblast growth factor receptor 2 gene has been reported predominantly in those patients with normal genitalia and steroidogenesis. We report a series of 4 patients with ABS and review their main findings and management.
Collapse
|
60
|
Miller WL, Auchus RJ. The molecular biology, biochemistry, and physiology of human steroidogenesis and its disorders. Endocr Rev 2011; 32:81-151. [PMID: 21051590 PMCID: PMC3365799 DOI: 10.1210/er.2010-0013] [Citation(s) in RCA: 1450] [Impact Index Per Article: 111.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 08/20/2010] [Indexed: 02/08/2023]
Abstract
Steroidogenesis entails processes by which cholesterol is converted to biologically active steroid hormones. Whereas most endocrine texts discuss adrenal, ovarian, testicular, placental, and other steroidogenic processes in a gland-specific fashion, steroidogenesis is better understood as a single process that is repeated in each gland with cell-type-specific variations on a single theme. Thus, understanding steroidogenesis is rooted in an understanding of the biochemistry of the various steroidogenic enzymes and cofactors and the genes that encode them. The first and rate-limiting step in steroidogenesis is the conversion of cholesterol to pregnenolone by a single enzyme, P450scc (CYP11A1), but this enzymatically complex step is subject to multiple regulatory mechanisms, yielding finely tuned quantitative regulation. Qualitative regulation determining the type of steroid to be produced is mediated by many enzymes and cofactors. Steroidogenic enzymes fall into two groups: cytochrome P450 enzymes and hydroxysteroid dehydrogenases. A cytochrome P450 may be either type 1 (in mitochondria) or type 2 (in endoplasmic reticulum), and a hydroxysteroid dehydrogenase may belong to either the aldo-keto reductase or short-chain dehydrogenase/reductase families. The activities of these enzymes are modulated by posttranslational modifications and by cofactors, especially electron-donating redox partners. The elucidation of the precise roles of these various enzymes and cofactors has been greatly facilitated by identifying the genetic bases of rare disorders of steroidogenesis. Some enzymes not principally involved in steroidogenesis may also catalyze extraglandular steroidogenesis, modulating the phenotype expected to result from some mutations. Understanding steroidogenesis is of fundamental importance to understanding disorders of sexual differentiation, reproduction, fertility, hypertension, obesity, and physiological homeostasis.
Collapse
Affiliation(s)
- Walter L Miller
- Distinguished Professor of Pediatrics, University of California San Francisco, San Francisco, California 94143-0978, USA.
| | | |
Collapse
|
61
|
Horvat S, Mcwhir J, Rozman D. Defects in cholesterol synthesis genes in mouse and in humans: lessons for drug development and safer treatments. Drug Metab Rev 2011; 43:69-90. [DOI: 10.3109/03602532.2010.540580] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
|
62
|
Saito Y, Yamamoto N, Katori N, Maekawa K, Fukushima-Uesaka H, Sugimoto D, Kurose K, Sai K, Kaniwa N, Sawada JI, Kunitoh H, Ohe Y, Yoshida T, Matsumura Y, Saijo N, Okuda H, Tamura T. Genetic Polymorphisms and Haplotypes of POR, Encoding Cytochrome P450 Oxidoreductase, in a Japanese Population. Drug Metab Pharmacokinet 2011; 26:107-16. [DOI: 10.2133/dmpk.dmpk-10-sc-096] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
63
|
Tomalik-Scharte D, Maiter D, Kirchheiner J, Ivison HE, Fuhr U, Arlt W. Impaired hepatic drug and steroid metabolism in congenital adrenal hyperplasia due to P450 oxidoreductase deficiency. Eur J Endocrinol 2010; 163:919-24. [PMID: 20844025 PMCID: PMC2977993 DOI: 10.1530/eje-10-0764] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
OBJECTIVE Patients with congenital adrenal hyperplasia due to P450 oxidoreductase (POR) deficiency (ORD) present with disordered sex development and glucocorticoid deficiency. This is due to disruption of electron transfer from mutant POR to microsomal cytochrome P450 (CYP) enzymes that play a key role in glucocorticoid and sex steroid synthesis. POR also transfers electrons to all major drug-metabolizing CYP enzymes, including CYP3A4 that inactivates glucocorticoid and oestrogens. However, whether ORD results in impairment of in vivo drug metabolism has never been studied. DESIGN We studied an adult patient with ORD due to homozygous POR A287P, the most frequent POR mutation in Caucasians, and her clinically unaffected, heterozygous mother. The patient had received standard dose oestrogen replacement from 17 until 37 years of age when it was stopped after she developed breast cancer. METHODS Both subjects underwent in vivo cocktail phenotyping comprising the oral administration of caffeine, tolbutamide, omeprazole, dextromethorphan hydrobromide and midazolam to assess the five major drug-metabolizing CYP enzymes. We also performed genotyping for variant CYP alleles known to affect drug metabolism. RESULTS Though CYP enzyme genotyping predicted normal or high enzymatic activities in both subjects, in vivo assessment showed subnormal activities of CYP1A2, CYP2C9, CYP2D6 and CYP3A4 in the patient and of CYP1A2 and CYP2C9 in her mother. CONCLUSIONS Our results provide in vivo evidence for an important role of POR in regulating drug metabolism and detoxification. In patients with ORD, in vivo assessment of drug-metabolizing activities with subsequent tailoring of drug therapy and steroid replacement should be considered.
Collapse
Affiliation(s)
- Dorota Tomalik-Scharte
- Department of PharmacologyUniversity Hospital, University of CologneCologne, 50931Germany
| | - Dominique Maiter
- Department of EndocrinologyUniversity Hospital Saint LucBrussels, 1200Belgium
| | - Julia Kirchheiner
- Department of Pharmacology of Natural Products and Clinical PharmacologyUniversity of UlmUlm, 89019Germany
| | | | - Uwe Fuhr
- Department of PharmacologyUniversity Hospital, University of CologneCologne, 50931Germany
| | - Wiebke Arlt
- (Correspondence should be addressed to W Arlt; )
| |
Collapse
|
64
|
Porter FD, Herman GE. Malformation syndromes caused by disorders of cholesterol synthesis. J Lipid Res 2010; 52:6-34. [PMID: 20929975 DOI: 10.1194/jlr.r009548] [Citation(s) in RCA: 319] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Cholesterol homeostasis is critical for normal growth and development. In addition to being a major membrane lipid, cholesterol has multiple biological functions. These roles include being a precursor molecule for the synthesis of steroid hormones, neuroactive steroids, oxysterols, and bile acids. Cholesterol is also essential for the proper maturation and signaling of hedgehog proteins, and thus cholesterol is critical for embryonic development. After birth, most tissues can obtain cholesterol from either endogenous synthesis or exogenous dietary sources, but prior to birth, the human fetal tissues are dependent on endogenous synthesis. Due to the blood-brain barrier, brain tissue cannot utilize dietary or peripherally produced cholesterol. Generally, inborn errors of cholesterol synthesis lead to both a deficiency of cholesterol and increased levels of potentially bioactive or toxic precursor sterols. Over the past couple of decades, a number of human malformation syndromes have been shown to be due to inborn errors of cholesterol synthesis. Herein, we will review clinical and basic science aspects of Smith-Lemli-Opitz syndrome, desmosterolosis, lathosterolosis, HEM dysplasia, X-linked dominant chondrodysplasia punctata, Congenital Hemidysplasia with Ichthyosiform erythroderma and Limb Defects Syndrome, sterol-C-4 methyloxidase-like deficiency, and Antley-Bixler syndrome.
Collapse
Affiliation(s)
- Forbes D Porter
- Program in Developmental Genetics and Endocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA.
| | | |
Collapse
|
65
|
Flück CE, Mullis PE, Pandey AV. Reduction in hepatic drug metabolizing CYP3A4 activities caused by P450 oxidoreductase mutations identified in patients with disordered steroid metabolism. Biochem Biophys Res Commun 2010; 401:149-53. [DOI: 10.1016/j.bbrc.2010.09.035] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 09/07/2010] [Indexed: 10/19/2022]
|
66
|
Sheng L, Ding X, Ferguson M, McCallister M, Rhoades R, Maguire M, Ramesh A, Aschner M, Campbell D, Levitt P, Hood DB. Prenatal polycyclic aromatic hydrocarbon exposure leads to behavioral deficits and downregulation of receptor tyrosine kinase, MET. Toxicol Sci 2010; 118:625-34. [PMID: 20889680 DOI: 10.1093/toxsci/kfq304] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Gene by environment interactions (G × E) are thought to underlie neurodevelopmental disorder, etiology, neurodegenerative disorders, including the multiple forms of autism spectrum disorder. However, there is limited biological information, indicating an interaction between specific genes and environmental components. The present study focuses on a major component of airborne pollutants, polycyclic aromatic hydrocarbons (PAHs), such as benzo(a)pyrene [B(a)P], which negatively impacts cognitive development in children who have been exposed in utero. In our study, prenatal exposure of Cpr(lox/lox) timed-pregnant dams to B(a)P (0, 150, 300, and 600 μg/kg body weight via oral gavage) on embryonic day (E14-E17) consistent with our susceptibility-exposure paradigm was combined with the analysis of a replicated autism risk gene, the receptor tyrosine kinase, Met. The results demonstrate a dose-dependent increase in B(a)P metabolite generation in B(a)P-exposed Cpr(lox/lox) offspring. Additionally, a sustained persistence of hydroxy metabolites during the onset of synapse formation was noted, corresponding to the peak of Met expression. Prenatal B(a)P exposure also downregulated Met RNA and protein levels and dysregulated normal temporal patterns of expression during synaptogenesis. Consistent with these data, transcriptional cell-based assays demonstrated that B(a)P exposure directly reduces human MET promoter activity. Furthermore, a functional readout of in utero B(a)P exposure showed a robust reduction in novel object discrimination in B(a)P-exposed Cpr(lox/lox) offspring. These results confirm the notion that common pollutants, such as the PAH B(a)P, can have a direct negative impact on the regulated developmental expression of an autism risk gene with associated negative behavioral learning and memory outcomes.
Collapse
Affiliation(s)
- Liu Sheng
- Department of Neuroscience and Pharmacology, Center for Molecular and Behavioral Neuroscience, Meharry Medical College, Nashville, Tennessee 37208, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
67
|
Pandey AV, Flück CE, Mullis PE. Altered heme catabolism by heme oxygenase-1 caused by mutations in human NADPH cytochrome P450 reductase. Biochem Biophys Res Commun 2010; 400:374-8. [PMID: 20732302 DOI: 10.1016/j.bbrc.2010.08.072] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Accepted: 08/17/2010] [Indexed: 11/28/2022]
Abstract
Human heme oxygenase-1 (HO-1) carries out heme catabolism supported by electrons supplied from the NADPH through NADPH P450 reductase (POR, CPR). Previously we have shown that mutations in human POR cause a rare form of congenital adrenal hyperplasia. In this study, we have evaluated the effects of mutations in POR on HO-1 activity. We used purified preparations of wild type and mutant human POR and in vitro reconstitution with purified HO-1 to measure heme degradation in a coupled assay using biliverdin reductase. Here we show that mutations in POR found in patients may reduce HO-1 activity, potentially influencing heme catabolism in individuals carrying mutant POR alleles. POR mutants Y181D, A457H, Y459H, V492E and R616X had total loss of HO-1 activity, while POR mutations A287P, C569Y and V608F lost 50-70% activity. The POR variants P228L, R316W and G413S, A503V and G504R identified as polymorphs had close to WT activity. Loss of HO-1 activity may result in increased oxidative neurotoxicity, anemia, growth retardation and iron deposition. Further examination of patients affected with POR deficiency will be required to assess the metabolic effects of reduced HO-1 activity in affected individuals.
Collapse
Affiliation(s)
- Amit V Pandey
- Pediatric Endocrinology, Diabetology and Metabolism, Department of Clinical Research, University of Bern, Tiefenaustrasse 120c, CH-3004 Bern, Switzerland.
| | | | | |
Collapse
|
68
|
Linder N, Amarilla M, Hernandez A, Tamiri T, Sirota L, Klinger G, Levy I, Merlob P. Association of high-dose bifonazole administration during early pregnancy and severe limb reduction defects in the newborn. ACTA ACUST UNITED AC 2010; 88:201-4. [PMID: 20014436 DOI: 10.1002/bdra.20644] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND Neonatal limb reduction defects may be caused by exposure to an external agent. The azole derivatives are used in the treatment of systemic and dermal mycoses. Their relative teratogenic risk is still controversial. CASES We describe two newborns with severe limb defects who were exposed to high doses of oral (an unacceptable route) and/or intravaginal bifonazole during the entire first trimester of pregnancy. CONCLUSION Although only two cases are insufficient to establish a relationship, our data suggest that maternal intake of bifonazole in early pregnancy poses a risk of morphogenic malformations. The literature suggests several possible mechanisms.
Collapse
Affiliation(s)
- Nehama Linder
- Department of Neonatology, Rabin Medical Center, Petach Tikva, Israel. linderm@ netvision.net.il
| | | | | | | | | | | | | | | |
Collapse
|
69
|
Nicolo C, Flück CE, Mullis PE, Pandey AV. Restoration of mutant cytochrome P450 reductase activity by external flavin. Mol Cell Endocrinol 2010; 321:245-52. [PMID: 20188793 DOI: 10.1016/j.mce.2010.02.024] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2009] [Revised: 01/21/2010] [Accepted: 02/18/2010] [Indexed: 10/19/2022]
Abstract
Cytochrome P450 oxidoreductase (POR) supplies electrons from NADPH to steroid and drug metabolizing reactions catalyzed by the cytochrome P450s located in endoplasmic reticulum. Mutations in human POR cause a wide spectrum of disease ranging from disordered steroidogenesis to sexual differentiation. Previously we and others have shown that POR mutations can lead to reduced activities of steroidogenic P450s CYP17A1, CYP19A1 and CYP21A1. Here we are reporting that mutations in the FMN binding domain of POR may reduce CYP3A4 activity, potentially influencing drug and steroid metabolism; and the loss of CYP3A4 activity may be correlated to the reduction of cytochrome b(5) by POR. Computational molecular docking experiments with a FMN free structural model of POR revealed that an external FMN could be docked in close proximity to the FAD moiety and receive electrons donated by NADPH. Using FMN supplemented assays we have demonstrated restoration of the defective POR activity in vitro.
Collapse
Affiliation(s)
- Catherine Nicolo
- Pediatric Endocrinology, Diabetology and Metabolism, Department of Clinical Research, University of Bern, Bern, Switzerland
| | | | | | | |
Collapse
|
70
|
Wei Y, Zhou X, Fang C, Li L, Kluetzman K, Yang W, Zhang QY, Ding X. Generation of a mouse model with a reversible hypomorphic cytochrome P450 reductase gene: utility for tissue-specific rescue of the reductase expression, and insights from a resultant mouse model with global suppression of P450 reductase expression in extrahepatic tissues. J Pharmacol Exp Ther 2010; 334:69-77. [PMID: 20375200 DOI: 10.1124/jpet.110.167411] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
A mouse model termed Cpr-low (CL) was recently generated, in which the expression of the cytochrome P450 reductase (Cpr) gene was globally down-regulated. The decreased CPR expression was accompanied by phenotypical changes, including reduced embryonic survival, decreases in circulating cholesterol, increases in hepatic P450 expression, and female infertility (accompanied by elevated serum testosterone and progesterone levels). In the present study, a complementary mouse model [named reversible-CL (r-CL)] was generated, in which the reduced CPR expression can be reversed in an organ-specific fashion. The neo cassette, which was inserted into the last Cpr intron in r-CL mice, can be deleted by Cre recombinase, thus returning the structure of the Cpr gene (and hence CPR expression) to normal in Cre-expressing cells. All previously identified phenotypes of the CL mice were preserved in the r-CL mice. As a first application of the r-CL model, we have generated an extrahepatic-CL (xh-CL) mouse for testing of the functions of CPR-dependent enzymes in all extrahepatic tissues. The xh-CL mice, generated by mating of r-CL mice with albumin-Cre mice, had normal CPR expression in hepatocytes but down-regulated CPR expression elsewhere. They were indistinguishable from wild-type mice in body and liver weights, circulating cholesterol levels, and hepatic microsomal P450 expression and activities; however, they still showed elevated serum testosterone and progesterone levels and sterility in females. Embryonic lethality was prevented in males, but apparently not in females, indicating a critical role for fetal hepatic CPR-dependent enzymes in embryonic development, at least in males.
Collapse
Affiliation(s)
- Yuan Wei
- Wadsworth Center, New York State Department of Health, Albany, NY 12201-0509, USA
| | | | | | | | | | | | | | | |
Collapse
|
71
|
Kok RC, Timmerman MA, Wolffenbuttel KP, Drop SLS, de Jong FH. Isolated 17,20-lyase deficiency due to the cytochrome b5 mutation W27X. J Clin Endocrinol Metab 2010; 95:994-9. [PMID: 20080843 DOI: 10.1210/jc.2008-1745] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Cytochrome P450c17 (P450c17) is a bifunctional enzyme necessary for the production of glucocorticoids (17-hydroxylase activity) and sex steroids (17,20-lyase activity). Isolated 17,20-lyase deficiency is a rare condition characterized by a deficient production of androgens resulting in 46,XY disorders of sex development (DSD) while the production of glucocorticoids is intact. Several missense mutations in the CYP17A1 gene are known to cause this condition. Cytochrome b(5) (CytB5) is an important factor in 17,20-lyase activity, probably by acting as an allosteric factor. OBJECTIVE The aim of this study was to investigate the role of CytB5 in a patient with defective 17,20-lyase activity. SETTING We conducted the study in a pediatric outpatient clinic of a University Hospital. PATIENTS We studied a 46,XY DSD patient with 17,20-lyase deficiency without missense mutation in the CYP17A1 gene and his parents. MAIN OUTCOME MEASURES We sequenced the CYB5 gene and measured steroid hormone levels. RESULTS Analysis of the CYB5 gene in our patient revealed a homozygous W27X mutation, leading to the formation of a premature stop codon; his parents were both heterozygous carriers of this mutation. This mutation results in the absence of residues E48 and E49 of CytB5, which are necessary for an intact 17,20-lyase activity. CONCLUSION We demonstrated 17,20-lyase deficiency due to an aberrant CytB5. Our findings thus provide evidence for an alternative etiology for this disorder.
Collapse
Affiliation(s)
- Renée C Kok
- Endocrine Laboratory, Department of Internal Medicine, Erasmus Medical Centre, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands
| | | | | | | | | |
Collapse
|
72
|
Sahakitrungruang T, Huang N, Tee MK, Agrawal V, Russell WE, Crock P, Murphy N, Migeon CJ, Miller WL. Clinical, genetic, and enzymatic characterization of P450 oxidoreductase deficiency in four patients. J Clin Endocrinol Metab 2009; 94:4992-5000. [PMID: 19837910 PMCID: PMC2795645 DOI: 10.1210/jc.2009-1460] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT P450 oxidoreductase (POR) deficiency causes disordered steroidogenesis; severe mutations cause genital ambiguity in both sexes plus the Antley-Bixler skeletal malformation syndrome, whereas mild mutations can cause adult infertility. OBJECTIVE We describe four patients with POR deficiency and identify and characterize the activities of their mutations. A 46,XY male with micropenis and two 46,XX female infants with genital ambiguity presented with skeletal malformations, and a 46,XX adolescent presented with primary amenorrhea, elevated 17alpha-hydroxyprogesterone, and low sex steroids. METHODS The coding regions of the POR gene were sequenced, and the identified mutations were recreated in human POR cDNA expression vectors lacking 27 N-terminal residues. POR and human P450c17 were expressed in bacteria. POR activity was measured by four assays: reduction of cytochrome c, oxidation of reduced nicotinamide adenine dinucleotide phosphate, and support of the 17alpha-hydroxylase and 17,20 lyase activities of P450c17. RESULTS All four patients were compound heterozygotes for POR mutations, including five novel mutations: L577R, N185K, delE217, and frameshift mutations 1363delC and 697-698insGAAC. N185K and delE217 lacked measurable activity in the assays based on P450c17 but retained partial activity in the assays based on cytochrome c. As assessed by V(max)/Km, L577R supported 46% of 17alpha-hydroxylase activity but only 27% of 17,20 lyase activity. Computational modeling of these novel mutants revealed the structural basis for their reduced or absent activities. CONCLUSION These patients illustrate the broad clinical spectrum of POR deficiency, including amenorrhea and infertility as the sole manifestation. POR assays based on P450c17 correlate well with hormonal and clinical phenotypes.
Collapse
Affiliation(s)
- Taninee Sahakitrungruang
- Department of Pediatrics, University of California San Francisco, San Francisco, California 94143, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
73
|
Scott HM, Mason JI, Sharpe RM. Steroidogenesis in the fetal testis and its susceptibility to disruption by exogenous compounds. Endocr Rev 2009; 30:883-925. [PMID: 19887492 DOI: 10.1210/er.2009-0016] [Citation(s) in RCA: 244] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Masculinization depends on adequate production of testosterone by the fetal testis within a specific "masculinization programming window." Disorders resulting from subtle deficiencies in this process are common in humans, and environmental exposures/lifestyle could contribute causally because common therapeutic and environmental compounds can affect steroidogenesis. This evidence derives mainly from rodent studies, but because there are major species differences in regulation of steroidogenesis in the fetal testis, this may not always be a guide to potential effects in the human. In addition to direct study of the effects of compounds on steroidogenesis, information also derives from study of masculinization disorders that result from mutations in genes in pathways regulating steroidogenesis. This review addresses this issue by critically reviewing the comparative timing of production and regulation of steroidogenesis in the fetal testis of humans and of rodents and its susceptibility to disruption; where there is limited information for the fetus, evidence from effects on steroidogenesis in the adult testis is considered. There are a number of fundamental regulatory differences between the human and rodent fetal testis, most notably in the importance of paracrine vs. endocrine drives during masculinization such that inactivating LH receptor mutations block masculinization in humans but not in rodents. Other large differences involve the steroidogenic response to estrogens and GnRH analogs and possibly phthalates, whereas for other compounds there may be differences in sensitivity to disruption (ketoconazole). This comparison identifies steroidogenic targets that are either vulnerable (mitochondrial cholesterol transport, CYP11A, CYP17) or not (cholesterol uptake) to chemical interference.
Collapse
Affiliation(s)
- Hayley M Scott
- MRC Human Reproductive Sciences Unit, Centre for Reproductive Biology, The Queen's Medical Research Institute, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK
| | | | | |
Collapse
|
74
|
Marohnic CC, Panda SP, McCammon K, Rueff J, Masters BSS, Kranendonk M. Human cytochrome P450 oxidoreductase deficiency caused by the Y181D mutation: molecular consequences and rescue of defect. Drug Metab Dispos 2009; 38:332-40. [PMID: 19884324 DOI: 10.1124/dmd.109.030445] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Patients with congenital adrenal hyperplasia, exhibiting combined CYP17 and CYP21 deficiency, were shown by Arlt et al. (2004) to harbor a 541T-->G mutation in exon 5 of POR (encoding NADPH-cytochrome P450 reductase, CYPOR), which resulted in a Y181D substitution that obliterated electron transfer capacity. Using bacterial expression models, we examined catalytic and physical properties of the human CYPOR Y181D variant. As purified, Y181D lacked flavin mononucleotide (FMN) and NADPH-cytochrome c reductase (NCR) activity but retained normal flavin adenine dinucleotide binding and NADPH utilization. Titration of the purified protein with FMN restored 64 of wild-type (WT) NCR activity in Y181D with an activation constant of approximately 2 microM. As determined by FMN fluorescence quenching, Y181D had K(d)(FMN) = 7.3 microM. Biplasmid coexpression of CYPOR and CYP1A2, at the physiological ratio of approximately 1:10 in the engineered MK_1A2_POR Escherichia coli strain, showed the compromised capacity of Y181D to support CYP1A2-catalyzed metabolism of the procarcinogens 2-aminoanthracene, 2-amino-3-methylimidazo(4,5-f)quinoline, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. Isolated MK1A2_POR membranes confirmed FMN stimulation of Y181D NCR activity with a 1.6 microM activation constant. CYP1A2 ethoxyresorufin-O-dealkylase activity of the MK1A2_POR(Y181D) membranes, undetectable in the absence of added FMN, increased to 37% of MK1A2_POR(WT) membranes with a 1.2 microM FMN activation constant. Therefore, we conclude that compromised FMN binding is the specific molecular defect causing POR deficiency in patients with Y181D mutation and that this defect, in large part, can be overcome in vitro by FMN addition.
Collapse
Affiliation(s)
- Christopher C Marohnic
- Department of Biochemistry, 7760, University of Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
| | | | | | | | | | | |
Collapse
|
75
|
Homma K, Hida M, Ikeda K, Yamaga N, Murata M, Hasegawa T. Measurement of Serum 17α-hydroxyprogesterone in Newborn Infants by Stable Isotope Dilution-Gas Chromatography/Mass Spectrometry. Clin Pediatr Endocrinol 2009; 18:77-80. [PMID: 23926364 PMCID: PMC3687607 DOI: 10.1297/cpe.18.77] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Accepted: 04/06/2009] [Indexed: 11/04/2022] Open
Abstract
Immunochemical measurement of serum 17α-hydroxyprogesterone (17OHP), the most important parameter for diagnosis of classical 21-hydroxylase deficiency (21OHD) in newborn infants, is known to be inaccurate due to the cross-reactivity of antibodies with a large quantity of fetal adrenal steroids. The aims of this study were 1) to establish reference values for the serum 17OHP level in Japanese newborn infants using non-immunochemical stable isotope dilution —gas chromatography/mass spectrometry (SID-GC/MS) and 2) to compare the serum 17OHP levels determined by SID-GC/MS with those determined by radioimmunoassay (RIA). The first study subjects were used for determination of reference values and included 57 healthy full-term newborn infants (4–5 d of age). The second study subjects were used for comparison of SID-GC/MS with RIA and included 27 healthy full-term newborn infants (3–6 d of age) and two subjects with neonatal transient hyper 17OHPnemia; these two subjects were 16 and 27 d of age, respectively. In the first study subjects, the intra-assay coefficient of variation for SID-GC/MS was 3% (n=5), the recovery rate was 98%, the sensitivity was 0.2 ng/ml, and the range of linearity was 0.5–200 ng/ml. The reference values for the serum 17OHP level determined by SID-GC/MS ranged from 0.3–1.5 (0.6) (ng/ml) (median). In the second study subjects, the serum 17OHP levels determined by SID-GC/MS were lower in one of the 27 subjects and both of the two subjects with neonatal transient hyper 17OHPnemia compared with the levels determined by RIA. Measurement of the serum 17OHP level using SID-GC/MS may be clinically useful for definitive diagnosis of classical 21OHD in newborn infants.
Collapse
Affiliation(s)
- Keiko Homma
- Central Clinical Laboratories, Keio University Hospital, Tokyo, Japan
| | | | | | | | | | | |
Collapse
|
76
|
|
77
|
Ko JM, Cheon CK, Kim GH, Yoo HW. A case of Antley-Bixler syndrome caused by compound heterozygous mutations of the cytochrome P450 oxidoreductase gene. Eur J Pediatr 2009; 168:877-80. [PMID: 18853185 DOI: 10.1007/s00431-008-0849-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Accepted: 09/24/2008] [Indexed: 10/21/2022]
Abstract
Antley-Bixler syndrome (ABS) is a skeletal malformation syndrome primarily affecting the skull and limbs. Although causal mutations in the FGFR2 gene have been found in some patients, mutations in the electron donor enzyme P450 oxidoreductase gene (POR) have recently been found to cause ABS in other patients. In addition to skeletal malformations, POR deficiency also causes glucocorticoid deficiency and congenital adrenal hyperplasia with ambiguous genitalia in both sexes. Here, we report on a 7-month-old Korean girl with ABS and ambiguous genitalia who was confirmed by POR gene analysis. Our patient showed typical skeletal findings with brachycephaly, mid-face hypoplasia, and radiohumeral synostosis. She also had partial labial fusion and a single urogenital orifice, as well as increased 17alpha-hydroxyprogesterone levels, suggesting a 21-hydroxylase deficiency. Cortisol and DHEA-sulfate response to rapid adrenocorticotropic hormone (ACTH) stimulation was inadequate. Direct sequencing of the POR gene revealed compound heterozygous mutations (I444fsX449 and R457H). This is the first report of a Korean patient with ABS caused by POR gene mutations.
Collapse
Affiliation(s)
- Jung Min Ko
- Department of Pediatrics, Asan Medical Center, Children and Adolescent Hospital, University of Ulsan College of Medicine, Songpa-Gu, Seoul, Korea
| | | | | | | |
Collapse
|
78
|
Fukami M, Nishimura G, Homma K, Nagai T, Hanaki K, Uematsu A, Ishii T, Numakura C, Sawada H, Nakacho M, Kowase T, Motomura K, Haruna H, Nakamura M, Ohishi A, Adachi M, Tajima T, Hasegawa Y, Hasegawa T, Horikawa R, Fujieda K, Ogata T. Cytochrome P450 oxidoreductase deficiency: identification and characterization of biallelic mutations and genotype-phenotype correlations in 35 Japanese patients. J Clin Endocrinol Metab 2009; 94:1723-31. [PMID: 19258400 DOI: 10.1210/jc.2008-2816] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
CONTEXT Cytochrome P450 oxidoreductase (POR) deficiency is a rare autosomal recessive disorder characterized by skeletal dysplasia, adrenal dysfunction, disorders of sex development (DSD), and maternal virilization during pregnancy. Although multiple studies have been performed for this condition, several matters remain to be clarified, including the presence of manifesting heterozygosity and the underlying factors for clinical variability. OBJECTIVE The objective of the study was to examine such unresolved matters by detailed molecular studies and genotype-phenotype correlations. PATIENTS Thirty-five Japanese patients with POR deficiency participated in the study. RESULTS Mutation analysis revealed homozygosity for R457H in cases 1-14 (group A), compound heterozygosity for R457H and one apparently null mutation in cases 15-28 (group B), and other combinations of mutations in cases 29-35 (group C). In particular, FISH and RT-PCR sequencing analyses revealed an intragenic microdeletion in one apparent R457H homozygote, transcription failure of apparently normal alleles in three R457H heterozygotes, and nonsense mediated mRNA decay in two frameshift mutation-positive cases examined. Genotype-phenotype correlations indicated that skeletal features were definitely more severe, and adrenal dysfunction, 46,XY DSD, and pubertal failure were somewhat more severe in group B than group A, whereas 46,XX DSD and maternal virilization during pregnancy were similar between two groups. Notable findings also included the contrast between infrequent occurrence of 46,XY DSD and invariable occurrence of 46,XX DSD and pubertal growth pattern in group A mimicking that of aromatase deficiency. CONCLUSIONS The results argue against the heterozygote manifestation and suggest that the residual POR activity reflected by the R457H dosage constitutes the underlying factor for clinical variability in some features but not other features, probably due to the simplicity and complexity of POR-dependent metabolic pathways relevant to each phenotype.
Collapse
Affiliation(s)
- Maki Fukami
- Research Institute, National Center for Child Health and Development, Tokyo 157-8535, Japan.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
79
|
Iijima S, Ohishi A, Ohzeki T. Cytochrome P450 oxidoreductase deficiency with Antley-Bixler syndrome: steroidogenic capacities. J Pediatr Endocrinol Metab 2009; 22:469-75. [PMID: 19618668 DOI: 10.1515/jpem.2009.22.5.469] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
For patients with cytochrome P450 oxidoreductase deficiency (PORD), steroid replacement is recommended at times of stress. However, it is unknown how hormones respond to actual physical stress in these patients. We report a female infant with PORD accompanied by the Antley-Bixler syndrome phenotype. Her urinary steroid profile revealed defective CYP17A1 and CYP21A2 activities, and an adrenocorticotropin (ACTH) stimulation test showed potential adrenal insufficiency. Hormonal responses to actual physical stress were as follows: Vigorous crying during blood sampling rarely affected the serum cortisol level. Acute viral gastroenteritis led to marked increases in blood ACTH and 17alpha-hydroxyprogesterone levels in proportion to the severity of the illness. The serum cortisol level also responded to this stress, but the response might have been blunted. Regarding peri-operative steroid replacement, intravenous hydrocortisone administration even at a dose of 6 mg/kg, which is lower than that recommended for congenital adrenal hyperplasia in Japan, proved to be excessive.
Collapse
Affiliation(s)
- Shigeo Iijima
- Department of Pediatrics, Hamamatsu University School of Medicine, Japan.
| | | | | |
Collapse
|
80
|
Abstract
Congenital adrenal hyperplasia (CAH) is one of the most common inherited metabolic disorders. It comprises a group of autosomal recessive disorders caused by the deficiency of one of four steroidogenic enzymes involved in cortisol biosynthesis or in the electron donor enzyme P450 oxidoreductase (POR) that serves as electron donor to steroidogenic cytochrome P450 (CYP) type II enzymes. The biochemical and clinical phenotype depends on the specific enzymatic defect and the impairment of specific enzyme activity. Defects of steroid 21-hydroxylase (CYP21A2) and 11beta-hydroxylase (CYP11B1) only affect adrenal steroidogenesis, whereas 17alpha-hydroxylase (CYP17A1) and 3beta-hydroxysteroid dehydrogenase type 2 (HSD3B2) deficiency also impact on gonadal steroid biosynthesis. Inactivating POR gene mutations are the cause of CAH manifesting with apparent combined CYP17A1-CYP21A2 deficiency. P450 oxidoreductase deficiency (ORD) has a complex phenotype including two unique features not observed in any other CAH variant: skeletal malformations and severe genital ambiguity in both sexes.
Collapse
Affiliation(s)
- Nils Krone
- Centre for Endocrinology, Diabetes & Metabolism, School of Clinical & Experimental Medicine, Institute of Biomedical Research, Edgbaston, Birmingham, UK.
| | | |
Collapse
|
81
|
Cholesterol metabolism: the main pathway acting downstream of cytochrome P450 oxidoreductase in skeletal development of the limb. Mol Cell Biol 2009; 29:2716-29. [PMID: 19273610 DOI: 10.1128/mcb.01638-08] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Cytochrome P450 oxidoreductase (POR) is the obligate electron donor for all microsomal cytochrome P450 enzymes, which catalyze the metabolism of a wide spectrum of xenobiotic and endobiotic compounds. Point mutations in POR have been found recently in patients with Antley-Bixler-like syndrome, which includes limb skeletal defects. In order to study P450 function during limb and skeletal development, we deleted POR specifically in mouse limb bud mesenchyme. Forelimbs and hind limbs in conditional knockout (CKO) mice were short with thin skeletal elements and fused joints. POR deletion occurred earlier in forelimbs than in hind limbs, leading additionally to soft tissue syndactyly and loss of wrist elements and phalanges due to changes in growth, cell death, and skeletal segmentation. Transcriptional analysis of E12.5 mouse forelimb buds demonstrated the expression of P450s involved in retinoic acid, cholesterol, and arachidonic acid metabolism. Biochemical analysis of CKO limbs confirmed retinoic acid excess. In CKO limbs, expression of genes throughout the whole cholesterol biosynthetic pathway was upregulated, and cholesterol deficiency can explain most aspects of the phenotype. Thus, cellular POR-dependent cholesterol synthesis is essential during limb and skeletal development. Modulation of P450 activity could contribute to susceptibility of the embryo and developing organs to teratogenesis.
Collapse
|
82
|
Inaoka Y, Yazawa T, Mizutani T, Kokame K, Kangawa K, Uesaka M, Umezawa A, Miyamoto K. Regulation of P450 oxidoreductase by gonadotropins in rat ovary and its effect on estrogen production. Reprod Biol Endocrinol 2008; 6:62. [PMID: 19077323 PMCID: PMC2647926 DOI: 10.1186/1477-7827-6-62] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Accepted: 12/16/2008] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND P450 oxidoreductase (POR) catalyzes electron transfer to microsomal P450 enzymes. Its deficiency causes Antley-Bixler syndrome (ABS), and about half the patients with ABS have ambiguous genitalia and/or impaired steroidogenesis. POR mRNA expression is up-regulated when mesenchymal stem cells (MSCs) differentiate into steroidogenic cells, suggesting that the regulation of POR gene expression is important for steroidogenesis. In this context we examined the regulation of POR expression in ovarian granulosa cells by gonadotropins, and its possible role in steroidogenesis. METHODS Changes in gene expression in MSCs during differentiation into steroidogenic cells were examined by DNA microarray analysis. Changes in mRNA and protein expression of POR in the rat ovary or in granulosa cells induced by gonadotropin treatment were examined by reverse transcription-polymerase chain reaction and western blotting. Effects of transient expression of wild-type or mutant (R457H or V492E) POR proteins on the production of estrone in COS-7 cells were examined in vitro. Effects of POR knockdown were also examined in estrogen producing cell-line, KGN cells. RESULTS POR mRNA was induced in MSCs following transduction with the SF-1 retrovirus, and was further increased by cAMP treatment. Expression of POR mRNA, as well as Cyp19 mRNA, in the rat ovary were induced by equine chorionic gonadotropin and human chorionic gonadotropin. POR mRNA and protein were also induced by follicle stimulating hormone in primary cultured rat granulosa cells, and the induction pattern was similar to that for aromatase. Transient expression of POR in COS-7 cells, which expressed a constant amount of aromatase protein, greatly increased the rate of conversion of androstenedione to estrone, in a dose-dependent manner. The expression of mutant POR proteins (R457H or V492E), such as those found in ABS patients, had much less effect on aromatase activity than expression of wild-type POR proteins. Knockdown of endogenous POR protein in KGN human granulosa cells led to reduced estrone production, indicating that endogenous POR affected aromatase activity. CONCLUSION We demonstrated that the expression of POR, together with that of aromatase, was regulated by gonadotropins, and that its induction could up-regulate aromatase activity in the ovary, resulting in a coordinated increase in estrogen production.
Collapse
Affiliation(s)
- Yoshihiko Inaoka
- Department of Biochemistry, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Takashi Yazawa
- Department of Biochemistry, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Tetsuya Mizutani
- Department of Biochemistry, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Koichi Kokame
- National Cardiovascular Research Center, Osaka 565-8565, Japan
| | - Kenji Kangawa
- National Cardiovascular Research Center, Osaka 565-8565, Japan
| | - Miki Uesaka
- Department of Biochemistry, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| | - Akihiro Umezawa
- National Research Institute for Child Health and Development, Tokyo 157-8535, Japan
| | - Kaoru Miyamoto
- Department of Biochemistry, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
| |
Collapse
|
83
|
Hershkovitz E, Parvari R, Wudy SA, Hartmann MF, Gomes LG, Loewental N, Miller WL. Homozygous mutation G539R in the gene for P450 oxidoreductase in a family previously diagnosed as having 17,20-lyase deficiency. J Clin Endocrinol Metab 2008; 93:3584-8. [PMID: 18559916 PMCID: PMC2567854 DOI: 10.1210/jc.2008-0051] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Very few patients have been described with isolated 17,20-lyase deficiency who have had their mutations in P450c17 (17alpha-hydroxylase/17,20-lyase) proven by DNA sequencing and in vitro characterization of the mutations. Most patients with 17,20-lyase deficiency have mutations in the domain of P450c17 that interact with the electron-donating redox partner, P450 oxidoreductase (POR). OBJECTIVE Our objective was to clarify the genetic and functional basis of isolated 17,20-lyase deficiency in familial cases who were previously reported as having 17,20-lyase deficiency. PATIENTS Four undervirilized males of an extended Bedouin family were investigated. One of these has previously been reported to carry mutations in the CYP17A1 gene encoding P450c17 causing isolated 17,20-lyase deficiency. METHODS Serum hormones were evaluated before and after stimulation with ACTH. Urinary steroid metabolites were profiled by gas chromatography-mass spectrometry. Exons 1 and 8 of CYP17A1 previously reported to harbor mutations in one of these patients and all 15 coding exons of POR were sequenced. RESULTS Gas chromatography-mass spectrometry (GC-MS) urinary steroid profiling and serum steroid measurements showed combined deficiencies of 17,20-lyase and 21-hydroxylase. Sequencing of exons 1 and 8 of CYP17A1 in two different laboratories showed no mutations. Sequencing of POR showed that all four patients were homozygous for G539R, a previously studied mutation that retains 46% of normal capacity to support the 17alpha-hydroxylase activity but only 8% of the 17,20-lyase activity of P450c17. CONCLUSION POR deficiency can masquerade clinically as isolated 17,20-lyase deficiency.
Collapse
Affiliation(s)
- Eli Hershkovitz
- Pediatric Endocrinology and Metabolic Unit, Soroka University Medical Center, P.O. Box 151, Beer Sheva 84101, Israel.
| | | | | | | | | | | | | |
Collapse
|
84
|
Honda A, Yamashita K, Miyazaki H, Shirai M, Ikegami T, Xu G, Numazawa M, Hara T, Matsuzaki Y. Highly sensitive analysis of sterol profiles in human serum by LC-ESI-MS/MS. J Lipid Res 2008; 49:2063-73. [DOI: 10.1194/jlr.d800017-jlr200] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
|
85
|
Hart SN, Zhong XB. P450 oxidoreductase: genetic polymorphisms and implications for drug metabolism and toxicity. Expert Opin Drug Metab Toxicol 2008; 4:439-52. [PMID: 18433346 DOI: 10.1517/17425255.4.4.439] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND Cytochrome P450 oxidoreductase (POR) is the only electron donor for all microsomal cytochrome P450 monooxygenases (CYP), some of which are phase I drug-metabolizing enzymes, responsible for oxidation of more than 80% of drugs. OBJECTIVES To provide a more thorough understanding of the genetic factors influencing drug metabolism, we address the role of genetic polymorphisms in the POR gene, and their implications for drug metabolism and cytotoxicity. METHODS The scope of this review is intended to cover polymorphisms currently identified in the POR gene, assess their functional significance on POR activity, and address their impact on CYP-mediated drug metabolism. POR is also responsible for directly metabolizing several anticancer prodrugs via a 1-electron reduction reaction, so the effect of POR polymorphisms on the direct bioactivation of drugs is also considered. RESULTS/CONCLUSION POR is a polymorphic enzyme that can affect CYP-mediated drug metabolism as well as direct bioactivation of prodrugs. Genetic polymorphisms in the POR gene may help to explain altered drug-metabolizing phenotypes.
Collapse
Affiliation(s)
- Steven N Hart
- University of Kansas Medical Center, Department of Pharmacology, Toxicology, and Therapeutics, 3901 Rainbow Boulevard, Kansas City, Kansas 66160, USA
| | | |
Collapse
|
86
|
Pharmacogenetics of P450 oxidoreductase: effect of sequence variants on activities of CYP1A2 and CYP2C19. Pharmacogenet Genomics 2008; 18:569-76. [DOI: 10.1097/fpc.0b013e32830054ac] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
|
87
|
Impairment of human CYP1A2-mediated xenobiotic metabolism by Antley-Bixler syndrome variants of cytochrome P450 oxidoreductase. Arch Biochem Biophys 2008; 475:93-9. [PMID: 18455494 DOI: 10.1016/j.abb.2008.04.014] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Revised: 04/14/2008] [Accepted: 04/15/2008] [Indexed: 01/08/2023]
Abstract
Y459H and V492E mutations of cytochrome P450 reductase (CYPOR) cause Antley-Bixler syndrome due to diminished binding of the FAD cofactor. To address whether these mutations impaired the interaction with drug-metabolizing CYPs, a bacterial model of human liver expression of CYP1A2 and CYPOR was implemented. Four models were generated: POR(null), POR(wt), POR(YH), and POR(VE), for which equivalent CYP1A2 and CYPOR levels were confirmed, except for POR(null), not containing any CYPOR. The mutant CYPORs were unable to catalyze cytochrome c and MTT reduction, and were unable to support EROD and MROD activities. Activity was restored by the addition of FAD, with V492E having a higher apparent FAD affinity than Y459H. The CYP1A2-activated procarcinogens, 2-aminoanthracene, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, and 2-amino-3-methylimidazo(4,5-f)quinoline, were significantly less mutagenic in POR(YH) and POR(VE) models than in POR(wt), indicating that CYP1A2, and likely other drug-metabolizing CYPs, are impaired by ABS-related POR mutations as observed in the steroidogenic CYPs.
Collapse
|
88
|
Genetics of P450 oxidoreductase: sequence variation in 842 individuals of four ethnicities and activities of 15 missense mutations. Proc Natl Acad Sci U S A 2008; 105:1733-8. [PMID: 18230729 DOI: 10.1073/pnas.0711621105] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
P450 oxidoreductase (POR) is an electron-donating flavoprotein required for the activity of all microsomal cytochrome P450 enzymes. We sequenced 5,655 bp of the POR gene in a representative population of 842 healthy unrelated individuals in four ethnic groups: 218 African Americans, 260 Caucasian Americans, 179 Chinese Americans, and 185 Mexican Americans. One hundred forty SNPs were detected, of which 43 were found in >/=1% of alleles. Twelve SNPs were in the POR promoter region. Fifteen of 32 exonic variations altered the POR amino acid sequence; 13 of these 15 are previously undescribed missense variations. We found eight indels, only one of which was in the coding region. A previously described variant, A503V, was found on 27.9% of all alleles with some ethnic predilection (19.1% in African Americans, 26.4% in Caucasian Americans, 36.7% Chinese Americans, and 31.0% in Mexican Americans). We built cDNA expression vectors for the 13 previously undescribed missense variants, expressed each protein lacking 27 N-terminal residues in Escherichia coli, and assayed the apparent K(m) and V(max) of each in four assays: reduction of cytochrome c, oxidation of NADPH, 17alpha-hydroxylase activity of P450c17, and 17,20 lyase activity of P450c17. The catalytic activities of several missense mutants differed substantially in these assays, indicating that each POR mutant must be assayed separately with each potential target P450 enzyme. The activity of A503V was reduced to a modest but statistically significant degree in all four assays, suggesting that it may play an important role in interindividual variation in drug response.
Collapse
|
89
|
Scott RR, Miller WL. Genetic and Clinical Features of P450 Oxidoreductase Deficiency. HORMONE RESEARCH 2008; 69:266-75. [DOI: 10.1159/000114857] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2007] [Accepted: 09/19/2007] [Indexed: 11/19/2022]
|
90
|
Genetic polymorphisms in cytochrome P450 oxidoreductase influence microsomal P450-catalyzed drug metabolism. Pharmacogenet Genomics 2008; 18:11-24. [DOI: 10.1097/fpc.0b013e3282f2f121] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
91
|
Abstract
Antley-Bixler syndrome is a congenital malformation syndrome that primarily manifests with craniofacial abnormalities but may include skeletal malformations. Some cases have been shown to be caused by fibroblast growth factor receptor 2 mutations and, recently, it was revealed that others are caused by mutations in the electron donor enzyme P450 oxidoreductase (POR). P450 oxidoreductase deficiency, however, is not only associated with the malformations but frequently presents with disordered sex development in affected patients of both sexes. Furthermore, biochemical work-up invariably reveals impairment of 17-hydroxylase and 21-hydroxylase activities, two steroidogenic enzymes dependent on electron transfer from POR. While we begin to gain insight into the pathogenesis of disease, detailed genotype-phenotype studies are still lacking and POR deficiency presents several challenges for research. Firstly, the exact pathogenesis of the skeletal malformations as a consequence of POR mutations is unclear, though impaired sterol biosynthesis has been implicated. Secondly, it needs to be explained, why the external genitalia in affected boys may appear undervirilized while affected girls can be severely virilized. Further evidence is required for the proposed alternative pathway in human androgen synthesis that might explain the apparently contradictory finding of low circulating androgens and severely virilised external genitalia in affected girls. Recent studies have provided evidence for a differential interaction of specific POR mutations with different electron-accepting P450 enzymes and this may provide the key for further understanding of the complex pathogenesis of this complex disease.
Collapse
Affiliation(s)
- Wiebke Arlt
- Division of Medical Sciences, School of Medicine University of Birmingham, Birmingham, UK.
| |
Collapse
|
92
|
Flück CE, Nicolo C, Pandey AV. Clinical, structural and functional implications of mutations and polymorphisms in human NADPH P450 oxidoreductase. Fundam Clin Pharmacol 2007; 21:399-410. [PMID: 17635179 DOI: 10.1111/j.1472-8206.2007.00520.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cytochrome P450 proteins are involved in metabolism of drugs and xenobiotics. In the endoplasmic reticulum a single nicotinamide adenine dinucleotide phosphate (NADPH) P450 oxidoreductase (POR) supplies electrons to all microsomal P450s for catalytic activity. POR is a flavoprotein that contains both flavin mononucleotide and flavin adenine dinucleotide as cofactors and uses NADPH as the source of electrons. We have recently reported a number of POR mutations in the patients with disordered steroidogenesis. In the first report we had described missense mutations (A287P, R457H, V492E, C569Y, and V608F) identified in four patients with defects in steroid production. Each POR variant was produced as recombinant N-27 form of the enzyme in bacteria and as full-length form in yeast. Membranes from bacteria or yeast expressing normal or variant POR were purified and their activities were characterized in cytochrome c and CYP17A1 assays. Later we have published a larger study that described a whole range of POR mutations and characterized the mutants/polymorphisms A115V, T142A, M263V, Y459H, A503V, G539R, L565P, R616X, V631I, and F646del from the sequencing of patient DNA. We also studied POR variants Y181D, P228L, R316W, G413S, and G504R that were available in public databases or published literature. Three-dimensional structure of rat POR is known and we have used this structure to deduce the structure-function correlation of POR mutations in human. The missense mutations found in patients with disordered steroidogenesis are generally in the co-factor binding and functionally important domains of POR and the apparent polymorphisms are found in regions with lesser structural importance. A variation in POR can alter the activity of all microsomal P450s, and therefore, can affect the metabolism of drugs and xenobiotics even when the P450s involved are otherwise normal. It is important to study the genetic and biochemical basis of POR variants in human population to gain information about possible differences in P450 mediated reactions among the individuals carrying a variant or polymorphic form of POR that could impact their metabolism.
Collapse
Affiliation(s)
- Christa E Flück
- Department of Pediatrics Endocrinology, University Children's Hospital, Freiburgstrasse 15, 3010 Bern, Switzerland
| | | | | |
Collapse
|
93
|
Dhir V, Ivison HE, Krone N, Shackleton CHL, Doherty AJ, Stewart PM, Arlt W. Differential Inhibition of CYP17A1 and CYP21A2 Activities by the P450 Oxidoreductase Mutant A287P. Mol Endocrinol 2007; 21:1958-68. [PMID: 17505056 DOI: 10.1210/me.2007-0066] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
P450 oxidoreductase (POR) has a pivotal role in facilitating electron transfer from nicotinamide adenine dinucleotide phosphate to microsomal cytochrome P450 (CYP) enzymes, including the steroidogenic enzymes CYP17A1 and CYP21A2. Mutations in POR have been shown recently to cause congenital adrenal hyperplasia with apparent combined CYP17A1 and CYP21A2 deficiency that comprises a variable clinical phenotype, including glucocorticoid deficiency, ambiguous genitalia, and craniofacial malformations. To dissect structure-function relationships potentially explaining this phenotypic diversity, we investigated whether specific POR mutations have differential effects on CYP17A1 and CYP21A2. We compared the impact of missense mutations encoding for single amino acid changes in three distinct regions of the POR molecule: 1), Y181D and H628P close to the central electron transfer area, 2) S244C located within the hinge close to the flavin adenine dinucleotide and flavin mononucleotide domains of POR, and 3) A287P that is clearly distant from the two other regions. Functional analysis using a yeast microsomal assay with coexpression of human CYP17A1 or CYP21A2 with wild-type or mutant human POR revealed equivalent decreases in CYP17A1 and CYP21A2 activities by Y181D, H628P, and S244C. In contrast, A287P had a differential inhibitory effect, with decreased catalytic efficiency (Vmax/Km) for CYP17A1, whereas CYP21A2 retained near normal activity. In vivo analysis of urinary steroid excretion by gas chromatography/mass spectrometry in 11 patients with POR mutations showed that A287P homozygous patients had the highest corticosterone/cortisol metabolite ratios, further indicative of preferential inhibition of CYP17A1. These findings provide novel mechanistic insights into the redox regulation of human steroidogenesis. Differential interaction of POR with electron-accepting CYP enzymes may explain the phenotypic variability in POR deficiency, with additional implications for hepatic drug metabolism by POR-dependant CYP enzymes.
Collapse
Affiliation(s)
- Vivek Dhir
- Division of Medical Sciences, Institute of Biomedical Research, The University of Birmingham, Birmingham B15 2TT, United Kingdom
| | | | | | | | | | | | | |
Collapse
|
94
|
Scott RR, Gomes LG, Huang N, Van Vliet G, Miller WL. Apparent manifesting heterozygosity in P450 oxidoreductase deficiency and its effect on coexisting 21-hydroxylase deficiency. J Clin Endocrinol Metab 2007; 92:2318-22. [PMID: 17389698 DOI: 10.1210/jc.2006-2345] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CONTEXT P450 oxidoreductase (POR) deficiency is a disorder of steroidogenesis affecting the microsomal P450 enzymes that use POR as an electron donor. The clinical presentation is variable; patients can be asymptomatic or can present with genital anomalies and the Antley-Bixler syndrome, characterized by craniosynostosis and other bony anomalies. Obligately heterozygous parents are normal. Combined POR and 21-hydroxylase deficiencies have not been reported. OBJECTIVE The aim was to explore the manifestations of combined deficiencies of 21-hydroxylase and POR and to search for lesions in apparent manifesting POR heterozygotes. PATIENTS AND METHODS A newborn female had craniosynostosis, severe salt wasting, minimal virilization, grossly elevated 17OH-progesterone, and minimally elevated androgens. DNA encoding 21-hydroxylase, POR, and fibroblast growth factor receptor 2 was sequenced. For POR, the first untranslated exon (exon 1U), 5' flanking DNA, and most introns were sequenced in five apparent manifesting POR heterozygotes. RESULTS CYP21B mutations were found on both alleles, proving classical 21-hydroxylase deficiency. Fibroblast growth factor receptor 2 exons 8 and 10 were normal. A POR mutation, A287P, was found only on the maternal allele. Five previously reported patients had POR mutations found on only one allele, but their clinical characteristics were indistinguishable from patients with mutations on both alleles. Sequencing of exon 1U, 274 bp of POR 5' flanking DNA, and 12 of the 15 POR introns did not identify additional mutations affecting gene expression or splicing. CONCLUSION Manifesting heterozygosity is a possible feature of POR deficiency and may ameliorate the findings in coexisting 21-hydroxylase deficiency.
Collapse
Affiliation(s)
- Rachel R Scott
- Pediatric Endocrinology, 672-S, University of California San Francisco, San Francisco, CA 94143-0434, USA
| | | | | | | | | |
Collapse
|
95
|
Haiman CA, Setiawan VW, Xia LY, Le Marchand L, Ingles SA, Ursin G, Press MF, Bernstein L, John EM, Henderson BE. A variant in the cytochrome p450 oxidoreductase gene is associated with breast cancer risk in African Americans. Cancer Res 2007; 67:3565-8. [PMID: 17440066 DOI: 10.1158/0008-5472.can-06-4801] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Variation in the cytochrome P450 oxidoreductase (POR) gene, a key regulator of type II cytochrome P450 enzymes, may affect exposure to endogenous steroid hormones and breast cancer risk. We sequenced the POR locus and tested candidate polymorphisms G5G and A503V for association with breast cancer risk among women in the Multiethnic Cohort Study (1,615 cases and 1,962 controls). The single nucleotide polymorphism (SNP) A503V was common in all racial/ethnic populations (minor allele frequency, > or =0.05) but was not associated with risk. SNP G5G (A --> G nucleotide change), which lies in a suggestive exonic splicing enhancer motif in exon 1, was common only in African Americans (minor allele frequency, 0.21) and the homozygous state was modestly associated with increased breast risk among all cases [345 cases and 426 controls; odds ratio (OR), 1.64; 95% confidence interval (CI), 0.89-3.04; P = 0.12] and among cases with advanced disease (95 cases: OR, 3.08; 95% CI, 1.42-6.70; P = 0.005). In an attempt to replicate this association, we genotyped SNP G5G in additional African American case-control studies (747 cases and 468 controls). Nonsignificant positive associations were noted with the GG genotype class in all studies. In the pooled analysis (1,038 cases and 877 controls with genotype data), the association was statistically significant among all cases (OR, 1.58; 95% CI, 1.04-2.41; P = 0.03) and stronger in those with advanced disease (411 cases and 877 controls; OR, 2.60; 95% CI, 1.56-4.34; P = 0.0002). These data suggest that African Americans harbor an allele at the POR locus that may increase breast cancer risk.
Collapse
Affiliation(s)
- Christopher A Haiman
- Departments of Preventive Medicine and Pathology, Keck School of Medicine, University of Southern California, 1441 Eastlake Avenue, Los Angeles, CA 90089, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
96
|
Gonçalves J, Friães A, Moura L. Congenital adrenal hyperplasia: focus on the molecular basis of 21-hydroxylase deficiency. Expert Rev Mol Med 2007; 9:1-23. [PMID: 17466088 DOI: 10.1017/s1462399407000300] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractCongenital adrenal hyperplasia (CAH) is an autosomal recessive disorder caused by defects in one of several steroidogenic enzymes involved in the synthesis of cortisol from cholesterol in the adrenal glands. More than 90% of cases are caused by 21-hydroxylase deficiency, and the severity of the resulting clinical symptoms varies according to the level of 21-hydroxylase activity. 21-Hydroxylase deficiency is usually caused by mutations in theCYP21A2gene, which is located on the RCCX module, a chromosomal region highly prone to genetic recombination events that can result in a wide variety of complex rearrangements, such as gene duplications, gross deletions and gene conversions of variable extensions. Molecular genotyping ofCYP21A2and the RCCX module has proved useful for a more accurate diagnosis of the disease, and prenatal diagnosis. This article summarises the clinical features of 21-hydroxylase deficiency, explains current understanding of the disease at the molecular level, and highlights recent developments, particularly in diagnosis.
Collapse
Affiliation(s)
- João Gonçalves
- Centro de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisboa, Portugal.
| | | | | |
Collapse
|
97
|
Abstract
All microsomal P450s require POR (cytochrome P450 reductase) for catalytic activity. Most of the clinically used drugs are metabolized by a small number of P450s and polymorphisms in the cytochrome P450s are known to cause changes in drug metabolism. We have recently found a number of POR missense mutations in the patients with disordered steroidogenesis. Our initial report described five missense mutations (A284P, R454H, V489E, C566Y and V605F) identified in four patients. We built bacterial expression vectors for each POR variant, purified the membranes expressing normal or variant POR and characterized their activities with cytochrome c and P450c17 assays. We have recently completed an extensive study of the range of POR mutations and characterized the mutants/polymorphisms A112V, T139A, M260V, Y456H, A500V, G536R, L562P, R613X, V628I and F643del from sequencing of patient DNA. We also studied POR variants Y179D, P225L, R313W, G410S and G501R that were available in databases or the published literature. We analysed the mutations with a three-dimensional model of human POR that was based on an essentially similar rat POR with known crystal structure. The missense mutations found in patients with disordered steroidogenesis mapped to functionally important domains of POR and the apparent polymorphisms mapped to less crucial regions. Since a variation in POR can alter the activity of all microsomal P450s, it can also affect the drug metabolism even with a normal P450. Understanding the genetic and biochemical basis of POR-mediated drug metabolism will provide valuable information about possible differences in P450-mediated reactions among the individuals carrying a variant or polymorphic form of POR.
Collapse
Affiliation(s)
- A V Pandey
- Theodor Kocher Institute, University of Bern, Freiestrasse 1, CH-3010 Bern, Switzerland.
| |
Collapse
|
98
|
Abstract
Congenital adrenal hyperplasia (CAH) comprises a group of autosomal recessive disorders, which are usually due to inactivating mutations in single enzymes involved in adrenal steroid biosynthesis. The characteristics of the biochemical and clinical phenotype depend on the specific enzymatic defect. In 21-hydroxylase and 11beta-hydroxylase deficiency only adrenal steroidogenesis is affected, whereas a defect in 3beta-hydroxysteroid dehydrogenase or 17alpha-hydroxylase also involves gonadal steroid biosynthesis. Recently, mutations in the electron donor enzyme P450 oxidoreductase were identified as the cause of CAH with apparent combined 17alpha-hydroxylase and 21-hydroxylase deficiency, thereby illustrating the impact of redox regulation enzymes on steroidogenesis. P450 oxidoreductase deficiency (ORD) has a complex phenotype including two unique features not observed in any other CAH variant, skeletal malformations and severe genital ambiguity in both sexes. Despite invariably low circulating androgens, females with ORD may present with virilized genitalia and mothers may suffer from virilization during pregnancy. This apparently contradictory finding may be explained by the existence of an alternative pathway in human androgen biosynthesis, with important implications for physiology and pathophysiology. This review discusses the biochemical and clinical presentation and the genetic and functional basis of the currently known CAH variants, with a specific focus on ORD.
Collapse
Affiliation(s)
- Nils Krone
- Institute of Biomedical Research, Division of Medical Sciences, University of Birmingham, Birmingham, UK
| | | | | | | |
Collapse
|
99
|
Hart SN, Li Y, Nakamoto K, Wesselman C, Zhong XB. Novel SNPs in Cytochrome P450 Oxidoreductase. Drug Metab Pharmacokinet 2007; 22:322-6. [PMID: 17827787 DOI: 10.2133/dmpk.22.322] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cytochrome P450 oxidoreductase (POR) is the single flavoprotein which donates electrons to the microsomal cytochrome P450 enzymes for oxidation of their substrates. In this study, we sequenced all 15 exons and the surrounding intronic sequences of POR in 100 human liver samples to identify novel and confirm known genetic polymorphisms in POR. Thirty-four single nucleotide polymorphisms (SNPs) were identified including 9 in the coding exons (5 synonymous and 4 nonsynonymous), 20 in the intronic regions, and 5 in the 3'-UTR. Of these, 9 were novel SNPs, including three nonsynonymous SNPs, SNH313003 (817733G>C; K49N), SNH313020 (848661C>A; L420M), and SNH313029 (849577T>C; L577P) with minor allele frequencies of 0.005, 0.045, and 0.020, respectively. We also confirmed a previously reported non-synonymous SNP rs1057868 (A503V) as well as five synonymous SNPs (G5G, T29T, P129P, S485S, and S572S) all with allele frequencies similar to those previously reported. Structurally, these polymorphisms occur in different regions: SNH313003 (K49N) in the amino-terminal tail, SNH313020 (L420M) in the connecting domain, SNH313029 (L577P) in the NADPH-binding domain, and rs1057868 (A503V) in the FAD binding domain.
Collapse
Affiliation(s)
- Steven N Hart
- Department of Pharmacology, Toxicology, and Therapeutics, The University of Kansas Medical Center, KS 66160, USA
| | | | | | | | | |
Collapse
|
100
|
Marohnic CC, Panda SP, Martásek P, Masters BS. Diminished FAD binding in the Y459H and V492E Antley-Bixler syndrome mutants of human cytochrome P450 reductase. J Biol Chem 2006; 281:35975-82. [PMID: 16998238 DOI: 10.1074/jbc.m607095200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Numerous mutations/polymorphisms of the POR gene, encoding NADPH:cytochrome P450 oxidoreductase (CYPOR), have been described in patients with Antley-Bixler syndrome (ABS), presenting with craniofacial dysmorphogenesis, and/or disordered steroidogenesis, exhibiting ambiguous genitalia. CYPOR is the obligate electron donor to 51 microsomal cytochromes P450 that catalyze critical steroidogenic and xenobiotic reactions, and to two heme oxygenase isoforms, among other redox partners. To address the molecular basis of CYPOR dysfunction in ABS patients, the soluble catalytic domain of human CYPOR was bacterially expressed. WT enzyme was green, due to air-stable FMN semiquinone (blue) and oxidized FAD (yellow). The ABS mutant V492E was blue-gray. Flavin analysis indicated that WT had a protein:FAD:FMN ratio of approximately 1:1:1, whereas approximately 1:0.1:0.9 was observed for V492E, which retained 9% of the WT k(cat)/K(m) in NADPH:cytochrome c reductase assays. V492E was reconstituted upon addition of FAD, post-purification, as shown by flavin analysis, activity assay, and near UV-visible CD. Both Y459H and V492E were expressed as membrane anchor-containing proteins, which also exhibited FAD deficiency. CYP4A4-catalyzed omega-hydroxylation of prostaglandin E1 was supported by WT CYPOR but not by either of the ABS mutants. Hydroxylation activity was rescued for both Y459H and V492E upon addition of FAD to the reaction. Based on these findings, decreased FAD-binding affinity is proposed as the basis of the observed loss of CYPOR function in the Y459H and V492E POR mutations in ABS.
Collapse
Affiliation(s)
- Christopher C Marohnic
- Department of Biochemistry, The University of Texas Health Science Center, San Antonio, Texas 78229, USA
| | | | | | | |
Collapse
|