Disease relevance of FDXR

• Mutant ferredoxins were produced in Escherichia coli, and separate assays were used to determine the effect of substitutions on the capacity of each mutant to bind to Fd-reductase and cytochrome P450scc and to participate in the cholesterol side chain cleavage reaction [1].
• Alterations in the AR gene result in a number of clinical disorders, including: androgen-insensitivity, which leads to disruption of male development; prostate cancer; and a neuromuscular degenerative condition termed spinal bulbar muscular atrophy or Kennedy's disease [2].
• Androgen insensitivity syndrome (AIS) is a disorder of male sexual development caused by an absent or dysfunctional AR [3].
• BphA4 is the ferredoxin reductase component of biphenyl dioxygenase from Pseudomonas sp. strain KKS102 [4].
• Mutants (over 50) of the vegetative ferredoxin have been designed to explore questions about cluster assembly and stabilization and to determine which residues are important for recognition and electron transfer to the redox partner Anabaena ferredoxin reductase [5].

High impact information on FDXR

• Targeted disruption of the FDXR gene in human colon cancer cells showed that it was essential for viability, and partial disruption of the gene resulted in decreased sensitivity to 5-FU-induced apoptosis [6].
• Ferredoxin reductase affects p53-dependent, 5-fluorouracil-induced apoptosis in colorectal cancer cells [6].
• Potentially, the development of newer drugs that selectively inhibit AR-mediated glucose metabolism and signaling, without affecting aldehyde detoxification, may be useful in preventing inflammation associated with the development of diabetic complications, particularly micro- and macrovascular diseases [7].
• These data underscore the need for reevaluating anti-AR interventions for the treatment of diabetic complications [7].
• Aldose reductase (AR) is widely expressed aldehyde-metabolizing enzyme [7].

Chemical compound and disease context of FDXR

• The ligand-binding domain (LBD) of the human androgen receptor (hAR LBD), encompassing amino acids (AAs) 647-919, was expressed in Escherichia coli with an N-terminal polyhistidine tag (His(10)-hAR LBD) from a pET-16b vector [8].
• Diabetic complications including neuropathy, nephropathy, cataracts and retinopathy are considerately caused by accumulation of sorbitol, which is produced from glucose by AR in polyol pathway [9].
• To examine if similar mechanisms are operating in the retinal pigment epithelium (RPE), another target tissue of diabetic complications, we studied the effect of hypertonic media on the induction of AR, alpha B-crystallin, myoinositol, taurine, and other free amino acids [10].
• Synthesis and accumulation of sorbitol in cells due to aldose reductase (AR) activity is implicated in secondary diabetic complications [11].
• Gene expression of ferredoxin reductase predicts outcome in patients with metastatic colorectal cancer treated by 5-fluorouracil plus leucovorin [12].

Biological context of FDXR

• We found that FDXR can be induced by DNA damage in cells in a p53-dependent manner and by a mutated form of p53 that is competent in inducing apoptosis [13].
• In addition, we identified a p53 response element located within the FDXR promoter that is responsive to wild-type p53, p63alpha, p63gamma, p73alpha, and p73beta [13].
• In contrast, substitutions at positions 76 and 79 (D76N and D79A) caused dramatic decreases in activity and in the affinity of ferredoxin for both Fd-reductase and P450scc; this suggests that the binding sites on ferredoxin for its redox partners overlap [1].
• The AR gene is X-linked and the protein is coded for by eight exons, giving rise to a C-terminal LBD (ligand-binding domain; exons 4-8), linked by a hinge region (exon 4) to a Zn-finger DBD (DNA-binding domain; exons 2 and 3) and a large structurally distinct NTD (N-terminal domain; exon 1) [2].
• Adrenodoxin reductase (ferrodoxin:NADP+ oxidoreductase, EC 1.18.1.2) is a flavoprotein mediating electron transport to all mitochondrial forms of cytochrome P450 [14].

Anatomical context of FDXR

• The adrenodoxin (Adx) concentration in mitochondria from term placentae is near-saturating for P450scc and under these conditions, we found that decreasing AR reduces the K(m) of P450scc for adrenodoxin [15].
• Treatment with 5 alpha-dihydrotestosterone (5 alpha-DHT) (10(-8) M) for 24 h did not alter hAR mRNA steady state levels in the hFOB/AR cell lines [16].
• Thus, treatment with AR inhibitors prevents vascular smooth muscle cell growth and endothelial cell apoptosis in culture and inflammation and restenosis in vivo [7].
• This is the first report of AR regulation in the pancreatic duct epithelium [17].
• The present studies examined the effects of glucose on Na, K-ATPase activity and on expression and activity of aldose reductase (AR), a primary enzyme of polyol metabolism, in Capan-1 human pancreatic duct cells [17].

Associations of FDXR with chemical compounds

• Increasing either the cholesterol or P450scc concentration increased the amount of AR required for P450scc to work at half its maximum velocity [15].
• In order to better understand which components of the cholesterol side-chain cleavage system are important in the regulation of placental progesterone synthesis, we have examined their effects on P450scc activity with both saturating and limiting concentrations of AR [15].
• The AR (androgen receptor) is a ligand-activated transcription factor that mediates the action of the steroids testosterone and dihydrotestosterone [2].
• Reducing equivalents that originate from NADH are transferred from ferredoxin reductase to ferredoxin and, in turn, to the terminal oxygenase, thus resulting in the activation of a dioxygen [4].
• Crystal structure of NADH-dependent ferredoxin reductase component in biphenyl dioxygenase [4].

Physical interactions of FDXR

• Site-specific mutations in human ferredoxin that affect binding to ferredoxin reductase and cytochrome P450scc [1].

Enzymatic interactions of FDXR

• Under anaerobic conditions, the endogenous rate of O2 reduction by NADPH catalyzed by ferredoxin reductase (0.12 s-1 at pH 7.4) is augmented by the anthracyclines and 7-deoxyanthracyclinones [18].

Regulatory relationships of FDXR

• The ferredoxin reductase gene is regulated by the p53 family and sensitizes cells to oxidative stress-induced apoptosis [13].

Other interactions of FDXR

• We propose a model in which Fd-reductase and P450scc share a requirement for ferredoxin residues Asp-76 and Asp-79 but have other determinants that differ and play an important role in binding [1].
• Placental cytochrome P450scc (CYP11A1): comparison of catalytic properties between conditions of limiting and saturating adrenodoxin reductase [15].
• Regional mapping of genes encoding human steroidogenic enzymes: P450scc to 15q23-q24, adrenodoxin to 11q22; adrenodoxin reductase to 17q24-q25; and P450c17 to 10q24-q25 [19].
• In concert with its cofactors, adrenodoxin and adrenodoxin reductase, and the transcription factor steroidogenic factor 1, P450scc converts cholesterol to pregnenolone [20].
• Its primary function as a soluble electron carrier between the NADPH-dependent adrenodoxin reductase and several cytochromes P450 makes it an irreplaceable component of the steroid hormones biosynthesis in the adrenal mitochondria of vertebrates [21].

Analytical, diagnostic and therapeutic context of FDXR

• We cloned the human adrenodoxin reductase gene and characterized it by restriction endonuclease mapping and DNA sequencing [14].
• Southern blot hybridization patterns of human genomic DNA cut with four restriction enzymes indicate that the human genome has only one gene for adrenodoxin reductase [22].
• Compared to nontransfected hFOB cells, constitutive hAR mRNA expression in three independent hAR-transfected hFOB clones (hFOB/AR) was 15-fold higher in hFOB/AR-16, 62-fold higher in hFOB/AR-2, and 72-fold higher in hFOB/AR-6 cells, respectively, as assessed by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) [16].
• This genomic characterization provides the foundation for pharmacogenetic analysis of the impact of FDXR on chemotherapy for colorectal cancer [23].
• To facilitate the study of this enzyme in cell culture systems, we engineered a fusion protein consisting of P450c27 coupled to its electron-transport accessory proteins, ferredoxin and ferredoxin reductase, and assessed its enzyme activity by measuring the C-25 and C-27 (side-chain) hydroxylation of 1 alpha-hydroxyvitamin D3 (1 alpha-OH-D3) [24].

References