scholarly journals Regulation of Microsomal P450, Redox Partner Proteins, and Steroidogenesis in the Developing Testes of the Neonatal Pig

Endocrinology ◽  
2002 ◽  
Vol 143 (9) ◽  
pp. 3361-3369 ◽  
Author(s):  
F. M. Moran ◽  
J. J. Ford ◽  
C. J. Corbin ◽  
S. M. Mapes ◽  
V. C. Njar ◽  
...  
Keyword(s):  
Gnrh Antagonist ◽  
Cytochromes P450 ◽  
Cytochrome B5 ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Reduced Form ◽  
Testicular Development ◽  
Aromatase Activity ◽  
P450 Reductase ◽  
Redox Partner ◽  
Partner Proteins

Abstract Testicular growth and plasma androgen concentrations increase markedly in the first weeks of neonatal life of pigs. The regulation of steroidogenesis through this period was examined by measuring total microsomal cytochromes P450 (P450), 17α-hydroxylase/17,20-lyase P450 (P450c17) and aromatase P450 (P450arom) enzyme activities, and the redox partner proteins nicotinamide adenine dinucleotide phosphate, reduced form (NADPH)-cytochrome P450 reductase (reductase) and cytochrome b5 in testicular microsomes. Testes were collected from 1–24 d of age, and testicular development was suppressed by a GnRH antagonist in some animals from d 1–14. Both 17/20-lyase and aromatase activities increased from d 1–7 but not thereafter, and 17–20-lyase activity was always at least 200-fold higher than aromatase activity. Reductase decreased in wk 1, then increased to d 24. No changes were seen in cytochrome b5 expression. GnRH antagonist treatment suppressed plasma LH, testosterone and testes growth to d 14. 17,20-Lyase and aromatase activities in testicular microsomes were reduced by 20% and 50%, respectively. Total microsomal P450 concentration was reduced by 50% on d 7, but there was no effect of treatment on reductase or cytochrome b5 expression. These data support the hypothesis that the rise in neonatal testicular androgen secretion is more likely due to gonadotropin-stimulated gonadal growth, rather than specific P450c17 expression. Neither P450c17 nor P450arom can account for the decline in total microsomal P450. Reductase and cytochrome b5 expression appears to be constitutive, but reductase levels saturate both P450c17 and P450arom.

scholarly journals Differential effects of variations in human P450 oxidoreductase on the aromatase activity of CYP19A1 polymorphisms R264C and R264H

2019 ◽  
Author(s):  
Shaheena Parween ◽  
Giovanna DiNardo ◽  
Francesca Baj ◽  
Chao Zhang ◽  
Gianfranco Gilardi ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Treatment Options ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Therapeutic Interventions ◽  
Diagnostic Tools ◽  
Variant Form ◽  
Aromatase Activity ◽  
Allelic Variants ◽  
P450 Oxidoreductase ◽  
Redox Partner

AbstractAromatase (CYP19A1) converts androgens into estrogens and is required for female sexual development and growth and development in both sexes. CYP19A1 is a member of cytochrome P450 family of heme-thiolate monooxygenases located in the endoplasmic reticulum and depends on reducing equivalents from the reduced nicotinamide adenine dinucleotide phosphate via the cytochrome P450 oxidoreductase coded by POR. Both the CYP19A1 and POR genes are highly polymorphic, and mutations in both these genes are linked to disorders of steroid biosynthesis. We have previously shown that R264C and R264H mutations in CYP19A1, as well as mutations in POR, result in a reduction of CYP19A1 activity. The R264C is a common polymorphic variant of CYP19A1, with high frequency in Asian and African populations. Polymorphic alleles of POR are found in all populations studied so far and, therefore, may influence activities of CYP19A1 allelic variants. So far, effects of variations in POR on enzymatic activities of allelic variants of CYP19A1 or any other steroid metabolizing cytochrome P450 proteins have not been studied. Here we are reporting the effects of three POR variants on the aromatase activities of two CYP19A1 variants, R264C and R264H. We used bacterially expressed and purified preparations of WT and variant forms of CYP19A1 and POR and constructed liposomes with embedded CYP19A1 and POR proteins and assayed the CYP19A1 activities using radiolabeled androstenedione as a substrate. With the WT-POR as a redox partner, the R264C-CYP19A1 showed only 15% of aromatase activity, but the R264H had 87% of aromatase activity compared to WT-CYP19A1. With P284L-POR as a redox partner, R264C-CYP19A1 lost all activity but retained 6.7% of activity when P284T-POR was used as a redox partner. The R264H-CYP19A1 showed low activities with both the POR-P284L as well as the POR-P284T. When the POR-Y607C was used as a redox partner, the R264C-CYP19A1 retained around 5% of CYP19A1 activity. Remarkably, The R264H-CYP19A1 had more than three-fold higher activity compared to WT-CYP19A1 when the POR-Y607C was used as the redox partner, pointing towards a beneficial effect. The slight increase in activity of R264C-CYP19A1 with the P284T-POR and the three-fold increase in activity of the R264H-CYP19A1 with the Y607C-POR point towards a conformational effect and role of protein-protein interaction governed by the R264C and R264H substitutions in the CYP19A1 as well as P284L, P284T and Y607C variants of POR. These studies demonstrate that the allelic variants of P450 when present with a variant form of POR may show different activities, and combined effects of variations in both the P450 enzymes as well as in the POR should be considered when genetic data are available. Recent trends in the whole-exome and whole-genome sequencing as diagnostic tools will permit combined evaluation of variations in multiple genes that are interdependent and may guide treatment options by adjusting therapeutic interventions based on laboratory analysis.

scholarly journals Steroidogenesis during postnatal testicular development of Galea spixii

Reproduction ◽  
2017 ◽  
Vol 154 (5) ◽  
pp. 645-652
Author(s):  
P R S Santos ◽  
F D Oliveira ◽  
M A M Arroyo ◽  
M F Oliveira ◽  
P Castelucci ◽  
...  
Keyword(s):  
Sexual Development ◽  
Cytochromes P450 ◽  
Quantitative Polymerase Chain Reaction ◽  
Testicular Development ◽  
Androgen Synthesis ◽  
Redox Partner ◽  
Estrogen Synthesis ◽  
Gene Transcripts ◽  
Pubertal Stages ◽  
Polymerase Chain

The androgen/estrogen balance is essential for normal sexual development and reproduction in mammals. Studies performed herein investigated the potential for estrogen synthesis in cells of the testes of a hystricomorph rodent, Galea spixii. The study characterized the expression of the key enzymes responsible for estrogen and androgen synthesis, cytochromes P450 aromatase (P450arom), 17α-hydroxylase/17,20-lyase (P450c17) respectively, as well as the redox partner NADPH cytochrome P450 oxido-reductase (CPR) required to support electron transfer and catalysis of these P450s, by immunohistochemistry (IHC) and quantitative polymerase chain reaction (qPCR) analysis, throughout postnatal sexual development. Testes (immature, pre-pubertal, pubertal and post-pubertal) were collected, fixed for IHC (CYP19, CYP17 and CPR) and stored frozen for qPCR for the relevant gene transcripts (Cyp19a1 and Cyp17a1). Expression of P450c17 was significantly elevated at the pre-pubertal and pubertal stages. Based on IHC, P450c17 was expressed only in Leydig cell clusters. The expression of P450arom was detectable at all stages of sexual development of Galea spixii. IHC data suggest that estrogen synthesis was not restricted to somatic cells (Leydig cells/Sertoli cells), but that germ cells may also be capable of converting androgens into estrogens, important for testicular function and spermatogenesis.

scholarly journals Interaction of human CYP17 (P-45017α, 17α-hydroxylase-17,20-lyase) with cytochrome b5: importance of the orientation of the hydrophobic domain of cytochrome b5

1997 ◽  
Vol 321 (3) ◽  
pp. 857-864 ◽  
Author(s):  
Peter LEE-ROBICHAUD ◽  
Mustak A. KADERBHAI ◽  
Naheed KADERBHAI ◽  
J. Neville WRIGHT ◽  
Muhammad AKHTAR
Keyword(s):  
Signal Sequence ◽  
Cytochrome B5 ◽  
Amino Acid Sequences ◽  
Side Chain ◽  
Hydrophobic Domain ◽  
Side Chain Cleavage ◽  
The Core ◽  
Cleavage Activity ◽  
P450 Reductase ◽  
Chain Cleavage

Human CYP17 (P-45017α, 17α-hydroxylase-17,20-lyase)-catalysed side-chain cleavage of 17α-hydroxyprogestogens into androgens is greatly dependent on the presence of cytochrome b5. The native form of cytochrome b5 is composed of a globular core, residues 1Ő98, followed by a membrane insertable C-terminal tail, residues 99Ő133. In the present study the abilities of five different forms of cytochrome b5 to support the side-chain cleavage activity of CYP17 were compared. The five derivatives were: the native pig cytochrome b5 (native pig), its genetically engineered rat counterpart (coreŐtail), the soluble core form of the latter (core), the core with the secretory signal sequence of alkaline phosphatase appended to its N-terminal (signalŐcore) and the latter containing the C-terminal tail of the native rat protein (signalŐcoreŐtail). When examined by Edman degradation and MS, the engineered proteins were shown to have the expected N-terminal amino acid sequences and molecular masses. The native pig was found to be acetylated at the N-terminal. The native pig and coreŐtail enzymes were equally efficient at enhancing the side-chain cleavage activity of human CYP17 and the signalŐcoreŐtail was 55% as efficient. The core and signalŐcore constructs were completely inactive in the aforementioned reaction. All the five derivatives were reduced to varying degrees by NADPH:cytochrome P-450 (NADPH-P450) reductase and the relative efficiencies of this reduction were reminiscent of the behaviour of these derivatives in supporting the side-chain cleavage reaction. In the side-chain cleavage assay, however, NADPH-P450 reductase was used in large excess so that the reduction of cytochrome b5 derivatives was not rate-limiting. The results highlight that productive interaction between cytochrome b5 and CYP17 is governed not only by the presence of a membrane insertable hydrophobic region on the cytochrome b5 but also by its defined spatial orientation at the C-terminal.

scholarly journals Towards Initial Indications for a Thiol-Based Redox Control of Arabidopsis 5-Aminolevulinic Acid Dehydratase

Antioxidants ◽  
2018 ◽  
Vol 7 (11) ◽  
pp. 152 ◽  
Author(s):  
Daniel Wittmann ◽  
Sigri Kløve ◽  
Peng Wang ◽  
Bernhard Grimm
Keyword(s):  
Aminolevulinic Acid ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Thioredoxin Reductase ◽  
Reducing Power ◽  
Reduced Form ◽  
Redox Control ◽  
In Planta ◽  
Acid Dehydratase ◽  
Reducing Conditions ◽  
Alad Activity

Thiol-based redox control is one of the important posttranslational mechanisms of the tetrapyrrole biosynthesis pathway. Many enzymes of the pathway have been shown to interact with thioredoxin (TRX) and Nicotinamide adenine dinucleotide phosphate (NADPH)-dependent thioredoxin reductase C (NTRC). We examined the redox-dependency of 5-aminolevulinic acid dehydratase (ALAD), which catalyzed the conjugation of two 5-aminolevulinic acid (ALA) molecules to porphobilinogen. ALAD interacted with TRX f, TRX m and NTRC in chloroplasts. Consequently, less ALAD protein accumulated in the trx f1, ntrc and trx f1/ntrc mutants compared to wild-type control resulting in decreased ALAD activity. In a polyacrylamide gel under non-reducing conditions, ALAD monomers turned out to be present in reduced and two oxidized forms. The reduced and oxidized forms of ALAD differed in their catalytic activity. The addition of TRX stimulated ALAD activity. From our results it was concluded that (i) deficiency of the reducing power mainly affected the in planta stability of ALAD; and (ii) the reduced form of ALAD displayed increased enzymatic activity.

Squalene epoxidase drives NAFLD-induced hepatocellular carcinoma and is a pharmaceutical target

2018 ◽  
Vol 10 (437) ◽  
pp. eaap9840 ◽  
Author(s):  
Dabin Liu ◽  
Chi Chun Wong ◽  
Li Fu ◽  
Huarong Chen ◽  
Liuyang Zhao ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Cell Growth ◽  
Cholesteryl Ester ◽  
Dna Methyltransferase ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Reduced Form ◽  
Squalene Epoxidase ◽  
High Cholesterol Diet ◽  
Sequencing Analysis ◽  
Nonalcoholic Fatty Liver

Nonalcoholic fatty liver disease (NAFLD)–induced hepatocellular carcinoma (HCC) is an emerging malignancy in the developed world; however, mechanisms that contribute to its formation are largely unknown, and targeted therapy is currently not available. Our RNA sequencing analysis of NAFLD-HCC samples revealed squalene epoxidase (SQLE) as the top outlier metabolic gene overexpressed in NAFLD-HCC patients. Hepatocyte-specific Sqle transgenic expression in mice accelerated the development of high-fat, high-cholesterol diet–induced HCC. SQLE exerts its oncogenic effect via its metabolites, cholesteryl ester and nicotinamide adenine dinucleotide phosphate (NADP+). Increased SQLE expression promotes the biosynthesis of cholesteryl ester, which induces NAFLD-HCC cell growth. SQLE increased the NADP+/NADPH (reduced form of NADP+) ratio, which triggered a cascade of events involving oxidative stress–induced DNA methyltransferase 3A (DNMT3A) expression, DNMT3A-mediated epigenetic silencing of PTEN, and activation of AKT-mTOR (mammalian target of rapamycin). In human NAFLD-HCC and HCC, SQLE is overexpressed and its expression is associated with poor patient outcomes. Terbinafine, a U.S. Food and Drug Administration–approved antifungal drug targeting SQLE, markedly inhibited SQLE-induced NAFLD-HCC cell growth in NAFLD-HCC and HCC cells and attenuated tumor development in xenograft models and in Sqle transgenic mice. Suppression of tumor growth by terbinafine is associated with decreased cholesteryl ester concentrations, restoration of PTEN expression, and inhibition of AKT-mTOR, consistent with blockade of SQLE function. Collectively, we established SQLE as an oncogene in NAFLD-HCC and propose that repurposing SQLE inhibitors may be a promising approach for the prevention and treatment of NAFLD-HCC.

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