FDXR Antibody

What is FDXR and what cellular functions does it perform?

FDXR (Ferredoxin Reductase, also known as adrenodoxin reductase) is a mitochondrial membrane-associated flavoprotein that serves as the first electron transfer protein in all mitochondrial P450 systems. Its primary function is to transfer electrons from NADPH to human ferredoxin proteins (FDX1 and FDX2) . FDXR is involved in several critical cellular processes including:

• Biosynthesis of iron-sulfur clusters, essential cofactors for various cellular processes

• Steroidogenesis, particularly in tissues like the adrenal cortex

• Cholesterol side chain cleavage in steroidogenic tissues

• Steroid 11-beta hydroxylation in the adrenal cortex

• 25-OH-vitamin D3-24 hydroxylation in the kidney

• Sterol C-27 hydroxylation in the liver

FDXR is expressed in all tissues with highest expression in tissues specialized in steroid hormone synthesis, such as the adrenal cortex . Recent research has also implicated FDXR in cancer progression, particularly in endocrine-resistant breast cancer .

What are the standard applications for FDXR antibodies?

FDXR antibodies are employed in multiple molecular biology techniques:

These applications have been validated across multiple species including human, mouse, rat, and pig samples . When selecting an FDXR antibody, it's essential to verify reactivity with your species of interest, as antibody performance can vary significantly between species.

What tissue types show significant FDXR expression?

FDXR is expressed with varying abundance across different tissues:

• Highest expression is found in steroidogenic tissues such as the adrenal cortex

• Significant expression in testis (mouse and rat)

• Detectable expression in liver (human)

• Notable expression in adrenal gland (human and pig)

• In the mouse cochlea, FDXR shows prominent expression in the spiral ganglion neuron area and moderate expression in the inner hair cell area

This expression pattern reflects FDXR's functional roles in steroidogenesis and mitochondrial function across different tissue types. When designing experiments, it's advisable to use tissues with known high expression (such as adrenal gland) as positive controls .

How should antigen retrieval and fixation be optimized for FDXR immunohistochemistry?

Successful FDXR immunohistochemistry requires careful optimization of fixation and antigen retrieval:

Fixation protocols:

• Formalin-fixed, paraffin-embedded (FFPE) tissues have been successfully used with FDXR antibodies

• For cell cultures, 4% paraformaldehyde fixation for 15 minutes at room temperature is effective

• For cochlear samples, 4% paraformaldehyde fixation for 1 hour at room temperature has been used successfully

Antigen retrieval methods:

• TE buffer pH 9.0 is suggested as the primary antigen retrieval method

• Alternatively, citrate buffer pH 6.0 can be used for antigen retrieval

Blocking conditions:

• 2% BSA, 0.1% Triton X-100, and 5% normal goat serum for 1 hour at room temperature

When developing an IHC protocol for a new tissue type, it's advisable to test both antigen retrieval methods, as FDXR detection can be significantly affected by the retrieval process. The search results indicate that human liver cancer tissue has been successfully stained using these protocols .

How can the specificity of an FDXR antibody be validated?

Validating antibody specificity is crucial for reliable experimental results. For FDXR antibodies, consider these validation approaches:

• Knockout/knockdown validation:

  • Use FDXR-knockdown (KD) cells as negative controls

  • Research has employed shRNA-mediated FDXR knockdown in T47D breast cancer cells

• Overexpression validation:

  • Transfect cells with GFP-tagged FDXR constructs

  • Compare antibody staining pattern with GFP signal

  • Studies have used full-length FLAG and HA double-tagged FDXR cloned into pBABE-puro vectors

• Western blot validation:

  • Confirm single band at the expected molecular weight (calculated: 54 kDa; observed: 48-58 kDa)

  • Include appropriate positive controls (adrenal tissue, testis)

• Multiple antibody concordance:

  • Compare staining patterns using antibodies targeting different FDXR epitopes

  • The literature reports use of antibodies targeting different regions (e.g., aa 1-150 vs. full protein)

The GFP-tagged FDXR (NM_001258012) approach used in published research provides an excellent positive control system for antibody validation .

How does FDXR expression change under different cellular stress conditions?

FDXR expression responds to various cellular stresses:

Radiation exposure:

• FDXR is significantly upregulated at the transcriptional level after radiation exposure

• Upregulation occurs in patients undergoing various radiation procedures (fluoroscopy, CT, radiotherapy)

• Expression changes are detectable as early as 2 hours post-exposure (after diagnostic CT)

• FDXR shows a dose-dependent response even at very low doses or partial body exposure

Endocrine treatment:

• Endocrine treatments (tamoxifen or fulvestrant) increase FDXR expression

• This increase occurs alongside upregulation of CPT1A expression

Mitochondrial stress:

• Mutations in FDXR lead to mitochondrial dysfunction markers

• These include decreased ATP levels, reduced mitochondrial membrane potential, and increased reactive oxygen species

These expression changes can be monitored through qPCR, Western blotting, or functional assays of mitochondrial activity, making FDXR an interesting biomarker for various stress conditions.

How can FDXR antibodies be used to investigate mitochondrial dysfunction in disease models?

FDXR antibodies offer powerful tools for investigating mitochondrial dysfunction across disease models:

Methodological approaches:

• Expression analysis in disease tissues:

  • Use IHC with FDXR antibodies to assess expression patterns in patient tissues

  • Compare FDXR localization between healthy and diseased samples

  • Research has employed this approach in patients with FDXR-related mitochondriopathy

• Mitochondrial function correlation:

  • Correlate FDXR expression/localization with functional parameters:

    • ATP levels

    • Mitochondrial membrane potential (MtMP)

    • Reactive oxygen species (ROS) levels

    • Iron accumulation (using Prussian blue staining)

  • Studies have demonstrated decreased ATP, reduced MtMP, and increased ROS in cells with FDXR mutations

• Intervention studies:

  • Monitor changes in FDXR expression after mitochondrial-targeted therapies

  • Research has shown that transferring functional mitochondria (PN-101) can restore function in FDXR-mutant cells

These approaches have been successfully applied in several disease models:

• Breast cancer (especially endocrine-resistant models)

• Mitochondriopathy and optic atrophy models

• Auditory neuropathy spectrum disorder (ANSD)

When designing such studies, it's critical to correlate FDXR protein levels with functional mitochondrial assays to establish causal relationships rather than mere associations.

What is the role of FDXR in cancer metabolism and endocrine resistance?

FDXR has emerged as a key player in cancer metabolism, particularly in endocrine-resistant breast cancer:

• FDXR-CPT1A-FAO signaling axis:

  • FDXR promotes fatty acid oxidation (FAO) by positively regulating CPT1A expression

  • This axis supports growth of both primary and endocrine-resistant breast cancer cells

  • Western blotting with FDXR antibodies shows increased expression in resistant cells

• Experimental approaches:

  • Western blotting to quantify FDXR and CPT1A expression changes

  • Cell proliferation assays (MTS assay) to correlate expression with growth

  • Colony formation and anchorage-independent growth assays to assess tumorigenic potential

  • Seahorse XF24 analyzer to measure FAO-mediated oxygen consumption rate

• Therapeutic implications:

  • Combination of endocrine therapy with FAO inhibitors (e.g., etomoxir) shows synergistic effects

  • FDXR depletion sensitizes resistant cells to endocrine treatment

For researchers investigating metabolic adaptations in cancer, FDXR antibodies provide a valuable tool to monitor this key metabolic regulator. The methodology typically involves:

• Creating resistant cell models through continuous treatment with tamoxifen (100 nM, >6 months) or fulvestrant (100 nM, >4 months)

• Western blotting to monitor FDXR expression changes during resistance development

• Functional assays to correlate expression with metabolic and growth phenotypes

How can FDXR antibodies help investigate the relationship between FDXR mutations and neurological disorders?

FDXR mutations cause a spectrum of neurological disorders, and antibodies are essential tools for investigating disease mechanisms:

• Expression and localization studies in neural tissues:

  • Immunohistochemistry in brain, cochlea, and retina samples

  • Research has shown prominent FDXR expression in the spiral ganglion neuron area and inner hair cell area of mouse cochlea

  • This expression pattern suggests FDXR's role in synaptic regions and the spiral ganglion

• Functional correlations in patient-derived cells:

  • Generate lymphoblastoid cell lines (LCLs) from patients with FDXR mutations

  • Use Western blotting with FDXR antibodies to confirm protein expression

  • Correlate with mitochondrial function assays (ATP, MtMP, ROS)

  • Patient-derived LCLs show decreased ATP, reduced MtMP, and increased ROS levels

• Axonal transport studies:

  • Assess anterograde axonal transport in retinal ganglion cells

  • Research in mouse models has shown that FDXR mutation causes reduced transport of tracers from the eye to the superior colliculi

• Iron accumulation in neural tissues:

  • FDXR mutations lead to abnormal iron accumulation in mitochondria

  • This can be visualized using Prussian blue staining

  • Iron accumulation occurs in multiple tissues including brain, liver, heart, and muscles

The neurological manifestations of FDXR mutations include optic atrophy, auditory neuropathy, peripheral neuropathy, and ataxia . Using FDXR antibodies alongside functional assays helps elucidate the complex pathophysiology of these disorders and potentially identify therapeutic targets.

What methodologies can be used to study FDXR's role in iron-sulfur cluster biogenesis?

Investigating FDXR's role in iron-sulfur (Fe-S) cluster biogenesis requires a multi-faceted approach:

• Iron homeostasis analysis:

  • Quantify iron in mitochondrial vs. cytosolic fractions using the QuantiChrom iron assay

  • Visualize iron accumulation with Prussian blue staining

  • Research has demonstrated that FDXR mutations lead to dramatic iron accumulation in mitochondria

• Functional consequences of FDXR dysfunction:

  • Measure activities of Fe-S containing enzymes

  • Assess electron transport chain complex activities

  • Monitor reactive oxygen species production

  • FDXR mutations cause reduced function of the electron transport chain and elevated ROS production

• Imaging approaches:

  • Use FDXR antibodies for immunocytochemistry to visualize mitochondrial localization

  • Double-staining with mitochondrial markers

  • Analysis of mitochondrial morphology and distribution

• Genetic manipulation:

  • FDXR knockdown models using shRNA

  • Site-directed mutagenesis to create specific FDXR variants

  • Rescue experiments with wild-type FDXR

  • Published studies have used these approaches to investigate FDXR function

When designing these experiments, it's important to consider tissue specificity, as iron accumulation and its consequences may vary between different tissues. The research indicates that brain, liver, heart, and muscle tissues all show significant iron accumulation in the context of FDXR mutations .

What are the most suitable cell models for studying FDXR function?

Several cell models have proven valuable for FDXR research:

Cancer cell lines:

• MCF7 and T47D (breast cancer): Used for studying FDXR in endocrine resistance

• U-2 OS (osteosarcoma): Suitable for ICC applications

• RT4 (urinary bladder cancer) and U-251 MG (brain glioma): Used for western blot detection

Patient-derived models:

• Lymphoblastoid cell lines (LCLs) derived from patients with FDXR mutations

• These provide an excellent model for studying disease mechanisms

• Allow comparison between patient and control cells

Resistance models:

• Tamoxifen- or fulvestrant-resistant derivatives of MCF7 and T47D

• Developed through continuous treatment (tamoxifen 100 nM, >6 months; fulvestrant 100 nM, >4 months)

• Cultured in phenol-red free medium with charcoal-stripped FBS and the appropriate drug

Experimental procedures:

• For general maintenance: DMEM with 10% FBS for MCF7, RPMI-1640 with 10% FBS for T47D

• For resistance models: Phenol-red free medium with charcoal-stripped FBS

• For genetic manipulation: Lentiviral infection using 293T packaging cells

These models offer complementary advantages for studying different aspects of FDXR biology, from basic function to disease mechanisms.

What controls should be included when working with FDXR antibodies?

Proper controls are essential for interpreting FDXR antibody-based experiments:

Positive controls:

• Tissues with known high FDXR expression (adrenal gland, testis)

• Cell lines with confirmed FDXR expression (MCF7, T47D)

• FDXR-overexpressing cells (cells transfected with FDXR expression plasmids)

Negative controls:

• FDXR knockdown samples (using shRNA)

• Primary antibody omission control

• Isotype control antibody

Technical controls for Western blotting:

• Loading controls: Vinculin (V9131, Sigma-Aldrich) has been used successfully

• Molecular weight markers to confirm band size (FDXR calculated MW: 54 kDa; observed: 48-58 kDa)

Validation controls:

• GFP-tagged FDXR transfection followed by antibody staining

• This approach can confirm antibody specificity by demonstrating co-localization

For quantitative applications, standard curves using recombinant FDXR protein can provide absolute quantification. When performing comparative studies, it's essential to maintain consistent protocols for sample preparation, antibody dilutions, and imaging parameters.

What are emerging applications of FDXR antibodies in research?

FDXR antibodies are finding new applications beyond traditional protein detection:

• Biomarker development:

  • FDXR shows promise as a biomarker for radiation exposure

  • Transcriptional changes in blood can be correlated with protein-level changes

  • Potential applications in radiation biodosimetry and environmental exposure assessment

• Therapeutic target validation:

  • The FDXR-CPT1A-FAO axis presents a potential therapeutic target for endocrine-resistant breast cancer

  • Antibodies can monitor target engagement and efficacy of novel treatments

• Precision medicine applications:

  • FDXR mutations cause a spectrum of neurological disorders

  • Antibody-based assays could potentially assess disease severity or progression

  • May help monitor response to interventions like mitochondrial transfer therapy

• Combination with emerging technologies:

  • Integration with spatial transcriptomics

  • Mass cytometry (CyTOF) with FDXR antibodies

  • Single-cell protein analysis

As research into FDXR's roles in disease continues to expand, antibody-based detection methods will remain essential tools for both basic research and translational applications.

What technical considerations can improve FDXR antibody performance?

Optimizing FDXR antibody performance requires attention to several technical factors:

• Antibody selection:

  • Consider the target epitope (N-terminal vs. internal regions)

  • Verify species reactivity for your model system

  • Available antibodies target different regions (e.g., aa 1-150 vs. FDXR fusion protein)

• Sample preparation optimization:

  • For cell lysis: EBC buffer (50 mM Tris pH 8.0, 120 mM NaCl, 0.5% NP40, 0.1 mM EDTA, 10% glycerol) with protease inhibitors

  • Protein quantification using Bradford assay ensures equal loading

• Application-specific considerations:

  • Western blot: Antibody dilutions range from 1:1000 to 1:8000

  • IHC: Dilutions from 1:50 to 1:500, with optimization for each tissue type

  • ICC: ~2 μg/mL starting concentration

• Storage and handling:

  • Store at -20°C for long-term stability

  • Aliquot to avoid freeze-thaw cycles

  • Some formulations contain 0.1% BSA for additional stability