FET3 Antibody

What is TFE3 and what is its biological function?

TFE3 (Transcription Factor E3) is a transcription factor that specifically recognizes and binds E-box sequences (3'-CANNTG-5'). It functions as an efficient DNA-binding protein, requiring dimerization with itself or with other proteins to effectively bind DNA . TFE3 plays significant roles in various cellular processes, including the regulation of innate immune responses. Research has shown that TFE3, along with TFEB, functions as a transcriptional regulator of innate immunity, with its activation being regulated through pathways involving the folliculin (FLCN) protein and AMPK (5'-AMP-activated protein kinase) .

TFE3 is ubiquitously expressed in fetal and adult tissues, suggesting its fundamental importance across different developmental stages and tissue types . The protein contains a basic helix-loop-helix (bHLH) domain characteristic of transcription factors in its family, allowing it to bind to specific DNA sequences and regulate gene expression.

What applications are TFE3 antibodies commonly used for?

TFE3 antibodies are utilized in multiple research applications, with the most common being:

• Western Blotting (WB): For detection of denatured TFE3 protein in samples

• Immunohistochemistry (IHC): For visualization of TFE3 in paraffin sections (IHC-p) or frozen sections (IHC-f) of tissue samples

• Immunofluorescence (IF/ICC): For detection of TFE3 in cell samples using fluorescence microscopy

• ELISA: For quantitative detection of antigenic peptides related to TFE3

The optimization of antibody dilutions for each application should be determined by the researcher based on their specific experimental conditions and samples .

How should researchers properly prepare samples for TFE3 immunofluorescence staining?

For effective immunofluorescence staining of TFE3, researchers should follow these methodological steps:

• Fixation:

  • Cover specimen with 4% formaldehyde (methanol-free) to a depth of 2-3 mm

  • Allow fixation for 15 minutes at room temperature

  • Rinse three times with PBS (pH 8.0) for 5 minutes each

• Blocking:

  • Block the specimen in blocking buffer (1X PBS/5% normal serum/0.3% Triton X-100) for 60 minutes

  • Use normal serum from the same species as the secondary antibody (e.g., normal goat serum)

• Antibody Incubation:

  • Prepare the TFE3 primary antibody in antibody dilution buffer (1X PBS/1% BSA/0.3% Triton X-100)

  • Apply the diluted primary antibody to the specimen according to recommended dilution ranges

Proper sample preparation is critical for achieving specific staining and reducing background, which can significantly impact result interpretation.

What are the common molecular weights and specifications for TFE3 antibodies?

The following table outlines the key specifications for TFE3 antibody:

For citation purposes, researchers should reference: "Affinity Biosciences Cat# AF0363, RRID:AB_2833528" . The molecular weight information is particularly important for verifying specificity when performing Western blot detection.

How does the FLCN-AMPK signaling pathway regulate TFE3 in innate immunity?

The relationship between TFE3 and the FLCN-AMPK pathway represents a sophisticated regulatory mechanism in innate immunity that operates independently of the mTORC1 signaling pathway. Research has revealed that:

• Loss of FLCN or overexpression of AMPK confers pathogen resistance via activation of TFEB/TFE3-dependent antimicrobial genes

• In C. elegans models, chronic AMPK activation due to flcn-1 loss enhances nuclear translocation of HLH-30 (the nematode ortholog of TFEB/TFE3) and induces expression of antimicrobial genes

• AMPK regulates the nuclear localization of TFEB/TFE3 and subsequent transcription of antimicrobial genes upon pathogen infection

• In mammalian cells, AMPK activation leads to the transcriptional up-regulation of pro-inflammatory cytokines through the nuclear translocation and activation of TFEB/TFE3

• Unlike starvation-induced TFEB/TFE3 activation, which involves mTORC1, pathogen-induced activation appears to be mTORC1-independent

Mechanistically, this suggests that AMPK activation under pathogen-induced conditions regulates TFEB and TFE3 distinctly from the metabolic stress response pathway. Quantitative proteomics have identified over 20 phosphorylation sites on TFEB and TFE3, suggesting potential direct regulation by AMPK, though this requires further investigation .

What methodological considerations should be taken when developing a recombinant antibody screening system for TFE3?

When developing recombinant antibody screening systems, researchers should consider the following methodological approach:

• Vector Design: Implement a Golden Gate-based dual-expression vector system for efficient cloning and expression of paired antibody chains (heavy and light chains)

• Membrane Display Strategy: Design the system to express antibodies in membrane-bound form for rapid screening, possibly fusing the antibody sequence to a fluorescent reporter gene (such as Venus) for visualization

• Cell Expression System: Utilize FreeStyle 293 cells or similar mammalian expression systems for proper folding and post-translational modifications of the antibodies

• Transfection Protocol:

  • Use 1 μg of antibody-expressing plasmid per 1×10^6 cells

  • Select appropriate transfection reagents (e.g., 293fectin Transfection Reagent)

  • Culture in expression medium in a humidified incubator with 8% CO2 at 37°C

• Binding Activity Assessment: Test displayed antibodies for binding activity using fluorescently-labeled antigens (e.g., Alexa647-labeled) and flow cytometry analysis

This approach allows for rapid isolation of high-affinity antibodies, potentially within 7 days from immunized mice, significantly accelerating the traditional antibody discovery timeline .

How can researchers troubleshoot non-specific binding with TFE3 antibodies in immunofluorescence studies?

Non-specific binding is a common challenge in immunofluorescence studies using TFE3 antibodies. Implementing the following troubleshooting approaches can significantly improve specificity:

• Optimize Blocking Conditions:

  • Extend blocking time to 90 minutes instead of 60 minutes

  • Test different blocking buffers by adjusting normal serum concentration (3-10%)

  • Consider adding additional blocking agents like BSA (1-5%)

• Antibody Dilution Optimization:

  • Perform a dilution series to determine optimal antibody concentration

  • For polyclonal TFE3 antibodies, higher dilutions often reduce background while maintaining specific signals

• Sample Preparation Modifications:

  • Ensure complete fixation with 4% formaldehyde for precisely 15 minutes

  • Extend PBS washing steps to 10 minutes each and increase number of washes

  • Pre-absorb the primary antibody with the blocking solution before application

• Validate Specificity Controls:

  • Include a peptide competition assay using the immunogen peptide

  • Perform parallel staining with different TFE3 antibody clones

  • Include known TFE3-negative and TFE3-positive samples as controls

• Data Analysis Considerations:

  • Quantify signal-to-noise ratio across different protocol conditions

  • Document exact fixation and permeabilization conditions that yield optimal results

These methodological refinements should be systematically tested and documented to establish an optimized protocol specific to the researcher's experimental system.

What recent advances have been made in understanding TFE3's role in phagocytosis and cellular bioenergetics?

Recent research has revealed sophisticated connections between TFE3 activation and cellular functions related to phagocytosis and bioenergetics:

• Metabolic Reprogramming: TFEB/TFE3 activation has been found to enhance the phagocytic capacity of innate immune effector cells through metabolic reprogramming. Following pathogen challenge, cells undergo a rapid reduction in cellular ATP levels, accompanied by acute AMPK activation and subsequent TFEB/TFE3 nuclear localization

• Phagocytic Enhancement: Down-regulation of FLCN in murine macrophages enhances their phagocytic activity and prompts a metabolic transformation toward increased cellular bioenergetics, further enhancing the innate immune response

• Autophagy and Lysosomal Biogenesis: FLCN/AMPK-mediated increase in autophagic flux and AMPK/TFEB-mediated increase in lysosomal biogenesis likely contribute to metabolic fitness of infected cells and increased phagocytosis in macrophages

• Fcγ Receptor Activation: Activation of the Fcγ receptor in macrophages has been shown to enhance lysosome-based proteolysis and killing of phagocytosed pathogens, potentially through TFEB/TFE3-dependent mechanisms

• Pathogen Tolerance Mechanisms: While TFEB/TFE3 activation may not directly affect pathogen burden over the course of infection, they appear to regulate mechanisms of tolerance to infection through autophagy/lysosomal pathways that enhance the host's ability to survive upon pathogen invasion

These findings suggest that TFE3 sits at a critical intersection between cellular metabolism, phagocytosis, and antimicrobial defense, presenting potential therapeutic targets for enhancing immune function.

How should researchers design experiments to investigate TFE3 nuclear translocation?

When designing experiments to study TFE3 nuclear translocation, a rigorous approach should incorporate:

• Time-Course Analysis:

  • Monitor TFE3 localization at multiple time points (e.g., 15, 30, 60, 120 minutes) after stimulation

  • Compare pathogen-induced versus starvation-induced translocation kinetics

  • Document the temporal relationship between AMPK activation and TFE3 nuclear entry

• Imaging Methodology:

  • Use immunofluorescence with optimized fixation protocols using 4% formaldehyde for 15 minutes

  • Employ nuclear counterstaining (DAPI or Hoechst) for precise nuclear/cytoplasmic delineation

  • Consider live-cell imaging with TFE3-fluorescent protein fusions for real-time dynamics

• Quantification Approach:

  • Calculate nuclear-to-cytoplasmic ratio of TFE3 signal intensity

  • Perform automated image analysis on >100 cells per condition

  • Apply statistical analysis to determine significance of translocation events

• Pathway Disruption Controls:

  • Include AMPK inhibitors (e.g., Compound C) and activators (e.g., AICAR)

  • Test mTORC1 inhibitors (e.g., rapamycin) to distinguish pathway independence

  • Utilize FLCN knockdown/knockout models to assess upstream regulation

This systematic approach allows for robust quantitative assessment of TFE3 nuclear translocation under various experimental conditions.

What are the critical quality control measures for validating a new TFE3 antibody lot?

Implementing rigorous quality control measures when validating a new TFE3 antibody lot is essential for experimental reliability:

• Western Blot Validation:

  • Confirm detection of the expected 62 kDa band in positive control samples

  • Test multiple cell lines with known TFE3 expression levels

  • Compare band intensity and specificity with previous antibody lots

• Immunofluorescence Cross-Validation:

  • Perform parallel staining with the new lot and a previously validated lot

  • Quantify nuclear/cytoplasmic signal ratios under basal and stimulated conditions

  • Document any changes in background staining or signal-to-noise ratio

• Peptide Competition Assay:

  • Pre-incubate the antibody with increasing concentrations of immunizing peptide

  • Verify signal reduction or elimination with specific peptide competition

  • Include non-specific peptide controls to confirm binding specificity

• Knockout/Knockdown Controls:

  • Test antibody in TFE3 knockout or siRNA knockdown samples

  • Verify complete signal elimination in knockout samples or proportional reduction in knockdown samples

  • Document any residual signal that might indicate cross-reactivity

• Lot-to-Lot Comparison Documentation:

  • Create a standardized validation report with side-by-side comparisons

  • Include image acquisition parameters to ensure comparable analysis

  • Maintain antibody validation records for reproducibility tracking

These validation steps should be completed before using a new lot for critical experiments to ensure data quality and reproducibility.

How is TFE3 antibody used in the diagnosis and study of TFE3-associated neoplasms?

TFE3 antibody has become an invaluable tool in diagnosing and investigating TFE3-associated neoplasms, which include renal cell carcinomas and other rare tumor types:

• Diagnostic Applications:

  • Immunohistochemical detection of TFE3 nuclear overexpression in tissue sections represents a standard diagnostic approach for identifying TFE3-rearranged neoplasms

  • TFE3 immunostaining patterns (intensity and subcellular localization) can help distinguish between different fusion partners in translocation-associated renal cell carcinomas

• Research Applications:

  • Investigation of downstream molecular pathways activated in TFE3-driven tumors

  • Correlation of TFE3 nuclear expression patterns with specific genomic alterations

  • Exploration of potential therapeutic vulnerabilities in TFE3-positive tumors

• Technical Considerations:

  • Careful validation of antibody specificity for diagnostic purposes is critical

  • Different antibody clones may have varying sensitivity and specificity for detecting TFE3 rearrangements

  • Correlation with molecular testing (FISH or RT-PCR) is recommended for definitive diagnosis

Understanding the specific patterns of TFE3 expression in different neoplasms continues to be an active area of research with important diagnostic and therapeutic implications.

What are the current methodological approaches for studying TFE3's role in autophagy and lysosomal biogenesis?

Investigating TFE3's function in autophagy and lysosomal biogenesis requires sophisticated methodological approaches:

• Gene Expression Analysis:

  • Quantify expression of TFE3-dependent genes involved in lysosomal biogenesis following various stimuli

  • Use RNA-seq to comprehensively map TFE3-regulated genes under different conditions (e.g., starvation, pathogen exposure)

  • Compare transcriptional profiles between wild-type and TFE3-deficient cells

• Lysosome Quantification:

  • Employ LysoTracker staining followed by flow cytometry or fluorescence microscopy to quantify lysosomal mass

  • Measure expression of key lysosomal enzymes (e.g., cathepsins) at protein and activity levels

  • Assess lysosomal pH using ratiometric dyes in TFE3-manipulated cells

• Autophagy Flux Assessment:

  • Monitor LC3-II conversion with and without lysosomal inhibitors (e.g., bafilomycin A1)

  • Quantify autophagic vesicles using fluorescent reporters (e.g., GFP-LC3)

  • Measure autophagy substrate (p62/SQSTM1) clearance rates in the presence and absence of TFE3

• Pathway Integration Analysis:

  • Investigate the interplay between AMPK activation, mTORC1 inhibition, and TFE3 nuclear translocation

  • Study the kinetics of TFE3 phosphorylation/dephosphorylation following different stimuli

  • Examine TFE3's interaction with other transcription factors and co-regulators

These methodological approaches provide a comprehensive framework for understanding TFE3's complex role in coordinating cellular responses to metabolic and immune challenges.

What emerging technologies might improve TFE3 antibody applications in research?

Several emerging technologies show promise for enhancing TFE3 antibody applications:

• Recombinant Antibody Engineering:

  • Development of high-specificity recombinant antibodies using genotype-phenotype linked antibody display technologies

  • Creation of bispecific antibodies that simultaneously target TFE3 and interacting partners for co-localization studies

  • Engineering of intrabodies that can track TFE3 in living cells without interfering with function

• Advanced Imaging Techniques:

  • Super-resolution microscopy to visualize TFE3's nuclear sublocalization with nanometer precision

  • Multiplexed imaging systems that can simultaneously track TFE3 and multiple pathway components

  • Correlative light-electron microscopy to connect TFE3 localization with ultrastructural features

• Single-Cell Analysis:

  • Integration of TFE3 antibody-based detection with single-cell transcriptomics

  • Development of proximity ligation assays to detect specific TFE3 protein-protein interactions at single-cell resolution

  • Antibody-based chromatin immunoprecipitation coupled with single-cell technologies to map TFE3 binding sites

These technological advances will likely provide unprecedented insights into TFE3's dynamic functions across different cellular contexts and disease states.

How might researchers integrate computational approaches with TFE3 antibody studies?

Computational approaches can significantly enhance TFE3 antibody-based research through:

• Machine Learning for Image Analysis:

  • Develop neural network models for automated quantification of TFE3 nuclear/cytoplasmic ratios

  • Train algorithms to recognize subtle patterns in TFE3 localization across different experimental conditions

  • Create pipelines for high-throughput screening of factors affecting TFE3 localization

• Systems Biology Integration:

  • Model the FLCN-AMPK-TFE3 pathway dynamics using differential equations

  • Integrate transcriptomic, proteomic, and imaging data to create comprehensive pathway maps

  • Predict potential therapeutic targets within the TFE3 regulatory network

• Structural Biology Applications:

  • Use molecular dynamics simulations to understand how phosphorylation affects TFE3 structure and nuclear import

  • Predict antibody epitope accessibility under different conformational states

  • Model TFE3-DNA binding dynamics at target promoters