FNIP1 Antibody, Biotin conjugated

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Description

Key Technical Parameters for Research Applications

The biotinylated FNIP1 antibody is optimized for ELISA, with compatibility for diverse experimental workflows.

Performance Metrics

ParameterDetail
Tested ReactivityHuman
Buffer0.01 M PBS, pH 7.4, 0.03% Proclin-300, 50% glycerol
Storage-20°C; avoid repeated freeze-thaw cycles
ApplicationsELISA (primary); potential use in multiplex assays

ELISA Optimization

The antibody serves as a detection reagent in sandwich ELISA kits (e.g., EH8566). Biotin conjugation enables binding to streptavidin-HRP, facilitating colorimetric detection via TMB substrate .

Workflow Example

  1. Coating: FNIP1-specific antibody pre-coated on plates.

  2. Sample Incubation: Standards or samples added.

  3. Detection: Biotinylated FNIP1 antibody binds to captured antigen.

  4. Signal Amplification: Streptavidin-HRP and TMB substrate generate measurable absorbance at 450 nm .

Research Findings and Biological Relevance

FNIP1 antibodies, including biotin-conjugated variants, are critical for studying:

  • B-cell Development: Fnip1 knockout mice exhibit pro-B cell arrest due to caspase activation and apoptosis, bypassed by Bcl2 overexpression .

  • Metabolic Regulation: FNIP1 interacts with AMPK and mTOR, modulating energy sensing and autophagy .

  • Tumor Suppression: FNIP1-FLCN complex sequesters GABARAP to lysosomes, regulating TFEB activation and lysosomal biogenesis .

Notable Studies

StudyKey FindingSource
Pro-B Cell ArrestFnip1−/− mice show B-cell lymphopenia; rescued by Bcl2
Autophagy RegulationFNIP1-FLCN-GABARAP axis controls lysosomal homeostasis
ELISA ValidationBiotinylated FNIP1 antibody quantifies protein levels in serum/plasma

Product Specs

Buffer
**Preservative:** 0.03% Proclin 300
**Constituents:** 50% Glycerol, 0.01M PBS, pH 7.4
Form
Liquid
Lead Time
Generally, we can ship the products within 1-3 business days after receiving your order. The delivery time may vary depending on the purchase method or location. Please contact your local distributor for specific delivery details.
Synonyms
FNIP1 antibody; KIAA1961Folliculin-interacting protein 1 antibody
Target Names
Uniprot No.

Target Background

Function
FNIP1 (Folliculin-Interacting Protein 1) is a binding partner of the GTPase-activating protein FLCN, playing a crucial role in the cellular response to amino acid availability. It regulates the mTORC1 signaling cascade, which controls the MiT/TFE factors TFEB and TFE3. Under low amino acid conditions, FNIP1 is part of the lysosomal folliculin complex (LFC) located on the lysosomal membrane. This complex inhibits the GTPase-activating activity of FLCN, leading to the inactivation of mTORC1 and promoting the nuclear translocation of TFEB and TFE3. Conversely, when amino acid levels rise, the LFC complex disassembles, releasing the GTPase-activating activity of FLCN. This activates mTORC1 and subsequently causes the cytoplasmic retention of TFEB and TFE3. FNIP1 is essential for FLCN recruitment to lysosomes and its interaction with Rag GTPases. FNIP1, in conjunction with FLCN, regulates autophagy. Following phosphorylation by ULK1, FNIP1 interacts with GABARAP and promotes autophagy. Beyond its role in mTORC1 signaling, FNIP1 acts as a co-chaperone for HSP90AA1/Hsp90. After gradual phosphorylation by CK2, FNIP1 inhibits the ATPase activity of HSP90AA1/Hsp90, leading to the activation of both kinase and non-kinase client proteins of HSP90AA1/Hsp90. It serves as a scaffold to load the client protein FLCN onto HSP90AA1/Hsp90. FNIP1 competes with the activating co-chaperone AHSA1 for binding to HSP90AA1, providing a reciprocal regulatory mechanism for chaperoning client proteins. Additionally, FNIP1 is a core component of the reductive stress response by inhibiting mitochondria activation under normal conditions. In response to reductive stress, the conserved Cys degron is reduced, leading to recognition and polyubiquitylation by the CRL2(FEM1B) complex, followed by proteasomal degradation. FNIP1 is required for B-cell development.
Gene References Into Functions
  1. The FLCN-FNIP complex, which is deregulated in Birt-Hogg-Dube syndrome, is absolutely required for B-cell differentiation. PMID: 22709692
  2. Research suggests that FLCN, mutated in Birt-Hogg-Dube syndrome, and its interacting partner FNIP1 may be involved in energy and/or nutrient sensing through the AMPK and mTOR signaling pathways. PMID: 17028174
Database Links

HGNC: 29418

OMIM: 610594

KEGG: hsa:96459

STRING: 9606.ENSP00000421985

UniGene: Hs.591273

Protein Families
FNIP family
Subcellular Location
Lysosome membrane. Cytoplasm, cytosol.
Tissue Specificity
Strong expression is found in the heart, liver placenta, muscle, nasal mucosa, salivary gland and uvula and moderate expression in kidney and lung. Higher levels detected in clear cell renal cell carcinoma (RCC) and chromophobe RCC than in normal kidney t

Q&A

What is FNIP1 and why is it significant for research?

FNIP1 (Folliculin-interacting protein 1) functions as a crucial binding partner of the GTPase-activating protein FLCN and plays a vital role in cellular metabolism regulation. The protein is integral to the cellular response to amino acid availability by regulating the non-canonical mTORC1 signaling cascade that controls MiT/TFE factors TFEB and TFE3. Research has demonstrated that FNIP1 is essential for B cell development and metabolic homeostasis, revealing a metabolic checkpoint that ensures pre-B cells have sufficient metabolic capacity to support division while limiting lymphomagenesis caused by deregulated growth . Additionally, FNIP1 promotes FLCN recruitment to lysosomes and interaction with Rag GTPases, leading to activation of non-canonical mTORC1 signaling. The protein's multifaceted roles make it an important target for immunological and metabolic research.

What are the key experimental applications for FNIP1 antibodies?

FNIP1 antibodies have demonstrated utility across multiple experimental applications in research settings. Based on validation studies, these antibodies can be effectively employed in Western Blotting (WB) for protein expression analysis, Immunohistochemistry (IHC) for tissue localization studies, Immunofluorescence (IF) for subcellular localization visualization, and Immunocytochemistry (ICC) for cellular studies . For biotin-conjugated FNIP1 antibodies specifically, Enzyme-Linked Immunosorbent Assay (ELISA) has been validated as an effective application . Researchers should design experiments with these validated applications in mind, while understanding that optimization may be required for specific experimental conditions.

How does biotin conjugation affect the functionality of FNIP1 antibodies?

Biotin conjugation of FNIP1 antibodies provides significant experimental advantages through the high-affinity interaction between biotin and streptavidin (Kd ≈ 10^-15 M). This conjugation enables signal amplification in detection systems while maintaining antibody specificity for the FNIP1 protein. Unlike unconjugated antibodies, biotin-conjugated FNIP1 antibodies can be detected using various streptavidin-conjugated reporter molecules (fluorophores, enzymes, or gold particles), offering experimental flexibility without needing secondary antibodies. The biotin tag does not typically interfere with antigen recognition when properly conjugated, though researchers should verify epitope accessibility in their specific experimental context . The conjugation process may slightly alter binding kinetics compared to unconjugated antibodies, necessitating optimization of incubation times and concentrations.

What are the optimal storage and handling conditions for maintaining FNIP1 antibody activity?

The biotin-conjugated FNIP1 antibody requires specific storage and handling protocols to preserve functionality. Upon receipt, store the antibody at -20°C or -80°C in the buffer provided (0.03% Proclin 300, 50% Glycerol, 0.01M PBS, pH 7.4) . Critical handling considerations include: avoiding repeated freeze-thaw cycles which can cause antibody degradation and aggregation; maintaining aliquots of working solutions (typically 10-50μL) to minimize freeze-thaw events; allowing the antibody to equilibrate to room temperature before opening to prevent condensation; and centrifuging briefly before use to collect solution at the bottom of the tube. For long-term storage stability, the antibody should remain at -80°C, while working aliquots can be kept at -20°C for up to one month. Always handle with powder-free gloves to prevent contamination, and avoid exposure to strong light which may affect the biotin moiety.

What protocols should be followed when using biotin-conjugated FNIP1 antibodies for ELISA?

When implementing biotin-conjugated FNIP1 antibodies in ELISA, researchers should follow this methodological framework:

  • Plate Preparation: Coat high-binding 96-well plates with capture antibody (typically anti-FNIP1) at 1-10 μg/mL in carbonate buffer (pH 9.6) overnight at 4°C.

  • Blocking: Block non-specific binding with 1-5% BSA or 5% non-fat dry milk in PBS or TBS for 1-2 hours at room temperature.

  • Sample Incubation: Add samples and standards in dilution buffer (typically blocking buffer with 0.05% Tween-20) for 1-2 hours at room temperature.

  • Detection Antibody: Apply the biotin-conjugated FNIP1 antibody (diluted 1:500-1:5000, requiring optimization) for 1-2 hours at room temperature.

  • Streptavidin-HRP: Add streptavidin-HRP conjugate (typically 1:1000-1:10,000 dilution) for 30-60 minutes.

  • Visualization: Develop with TMB substrate and stop with 2N H₂SO₄.

  • Measurement: Read absorbance at 450nm with 570nm correction.

Between each step, perform 3-5 washes with PBS or TBS containing 0.05% Tween-20 . This protocol should be optimized for specific experimental conditions through antibody titration experiments.

How can researchers validate the specificity of biotin-conjugated FNIP1 antibodies?

Validating antibody specificity is crucial for reliable experimental outcomes. For biotin-conjugated FNIP1 antibodies, implement these comprehensive validation approaches:

  • Positive and Negative Controls:

    • Positive controls: Use tissues or cell lines known to express FNIP1 (based on literature)

    • Negative controls: Employ FNIP1 knockout or knockdown cells/tissues

    • Isotype controls: Use biotin-conjugated IgG from the same host species (rabbit)

  • Cross-reactivity Assessment:

    • Test antibody against recombinant FNIP1 and related proteins (FNIP2)

    • Cross-species reactivity evaluation if working with non-human models

  • Blocking Peptide Experiments:

    • Pre-incubate antibody with immunogen peptide (aa 221-508 of FNIP1)

    • Observe signal elimination when the specific epitope is blocked

  • Western Blot Correlation:

    • Confirm target protein molecular weight (approximately 130 kDa for FNIP1)

    • Verify signal disappearance in knockout samples

  • Method-specific Controls:

    • For ELISA: Include no-primary antibody and no-sample controls

    • For Immunohistochemistry: Examine expected subcellular localization patterns

Document all validation steps meticulously to establish antibody reliability for subsequent experiments.

How can FNIP1 antibodies be utilized to investigate its interaction with metabolic pathways?

FNIP1's role in metabolic regulation can be investigated using biotin-conjugated antibodies through several sophisticated approaches:

  • Co-immunoprecipitation (Co-IP) Studies:

    • Use streptavidin beads to pull down biotin-FNIP1 antibody complexes

    • Identify interacting partners through mass spectrometry or Western blotting

    • Focus on known metabolic regulators like AMPK, mTOR, and TSC2

    • Perform under various metabolic stress conditions (nutrient deprivation, rapamycin treatment)

  • Subcellular Localization Analysis:

    • Employ confocal microscopy with biotin-FNIP1 antibodies and streptavidin-fluorophores

    • Co-stain with markers for lysosomes (LAMP1), mitochondria (MitoTracker), and mTOR

    • Analyze translocation patterns under amino acid starvation and replenishment

    • Quantify co-localization coefficients with subcellular compartments

  • Phosphorylation Status Assessment:

    • Combine with phospho-specific antibodies against AMPK (T172) and mTOR targets

    • Implement sequential immunoprecipitation to isolate FNIP1 followed by phosphorylation analysis

    • Monitor changes in response to energy stress inducers (AICAR, 2-DG)

  • Chromatin Immunoprecipitation (ChIP):

    • Investigate FNIP1's potential nuclear interactions with transcription factors

    • Analyze binding to promoter regions of metabolic genes

Research findings indicate FNIP1 functions at the intersection of AMPK and mTOR signaling, with disruption leading to dysregulation of these metabolic regulators resulting in excessive cell growth and enhanced sensitivity to apoptosis .

What are the methodological considerations for investigating FNIP1's role in B cell development?

To investigate FNIP1's critical role in B cell development, researchers should consider this methodological framework:

  • Flow Cytometry Panel Design:

    • Primary markers: B220, CD19, IgM, CD43, BP-1, and CD24

    • Secondary markers: IL-7R, pre-BCR components

    • FNIP1 internal staining using permeabilization and biotin-conjugated antibody

  • Ex Vivo B Cell Development Assays:

    • Bone marrow isolation and culture with IL-7

    • Monitor proliferation using CFSE dilution

    • Assess developmental progression by surface marker changes

    • Compare FNIP1 knockout vs. wildtype cells

    • Measure cell size changes using forward scatter parameters

  • Metabolic Profiling Methods:

    • Oxygen consumption rate (OCR) measurement

    • Extracellular acidification rate (ECAR) analysis

    • Glucose uptake assays using 2-NBDG

    • ATP production measurement

    • Mitochondrial mass and potential assessment

  • Signaling Pathway Analysis:

    • Western blotting for pre-BCR signaling components

    • AMPK and mTOR activation monitoring

    • Autophagy marker analysis (LC3, p62)

    • Apoptosis assessment under metabolic stress conditions

Research has demonstrated that FNIP1 deletion causes a complete block in B cell development at the pre-B cell stage due to dysregulation of metabolic regulators AMPK and mTOR, establishing FNIP1 as a metabolic checkpoint controller during B lymphopoiesis .

How can FNIP1 antibodies be employed in studying its interaction with the HSP90 pathway?

To investigate FNIP1's co-chaperone function with HSP90, researchers should implement these methodological approaches:

  • Proximity Ligation Assays (PLA):

    • Use biotin-conjugated FNIP1 antibody and anti-HSP90 antibody

    • Employ streptavidin-oligonucleotide and secondary antibody-oligonucleotide conjugates

    • Quantify interaction signals under various cellular conditions

    • Compare interactions before and after CK2 inhibition

  • In Vitro ATPase Activity Measurements:

    • Immunoprecipitate HSP90 complexes with/without FNIP1

    • Measure ATPase activity via malachite green phosphate detection assay

    • Compare results between wildtype and FNIP1-depleted conditions

    • Assess the effect of phosphorylation status on interaction

  • Client Protein Loading Assays:

    • Use biotin-FNIP1 antibodies to study FLCN recruitment to HSP90

    • Implement sequential immunoprecipitation approaches

    • Utilize FNIP1 mutants lacking key phosphorylation sites

    • Compare with other co-chaperones like AHSA1

  • Competitive Binding Studies:

    • Assess competition between FNIP1 and AHSA1 for HSP90 binding

    • Utilize surface plasmon resonance (SPR) or microscale thermophoresis

    • Investigate binding affinities under various cellular conditions

Research indicates FNIP1 acts as a co-chaperone of HSP90AA1/Hsp90 and undergoes gradual phosphorylation by CK2, inhibiting HSP90's ATPase activity and thereby activating both kinase and non-kinase client proteins. FNIP1 also functions as a scaffold to load client protein FLCN onto HSP90 .

What strategies can address inconsistent FNIP1 antibody staining patterns in immunoassays?

When confronting inconsistent staining patterns with biotin-conjugated FNIP1 antibodies, implement this systematic troubleshooting approach:

IssuePotential CauseSolution Strategy
High backgroundInsufficient blockingIncrease blocking time/concentration; use alternative blocking agents (BSA, casein, normal serum)
Endogenous biotinAdd avidin/streptavidin blocking step before antibody application
Non-specific bindingInclude 0.1-0.3% Triton X-100 in antibody diluent; optimize antibody concentration
Weak/no signalEpitope maskingTest multiple antigen retrieval methods (heat-induced, enzymatic)
Low target expressionIncrease antibody concentration; extend incubation time (overnight at 4°C)
Antibody degradationUse fresh aliquots; verify storage conditions
Variable cell-to-cell stainingHeterogeneous expressionConfirm with alternate FNIP1 antibodies targeting different epitopes
Fixation artifactsCompare multiple fixation methods (PFA, methanol, acetone)
Unexpected subcellular localizationAntibody cross-reactivityValidate with knockout controls; perform peptide competition
Post-translational modificationsInvestigate conditions affecting FNIP1 localization (nutrient status, stress)

Remember that FNIP1 localization can change based on cellular metabolic status, particularly under conditions affecting mTOR signaling or amino acid availability, which may explain some pattern variations .

How should researchers interpret contradictory findings when studying FNIP1 function across different experimental systems?

When encountering contradictory results across experimental systems, implement this analytical framework:

  • System-specific Context Analysis:

    • Cell/tissue type differences: FNIP1 functions may vary between immune cells and other tissues

    • Species variations: Mouse Fnip1 (documented in B-cell development) may have context-specific functions different from human FNIP1

    • Developmental stage impact: FNIP1 requirements may differ between developing B cells and mature cells

  • Methodological Variations Assessment:

    • Antibody epitope differences: Distinct antibodies may recognize different FNIP1 domains/conformations

    • Knockout/knockdown strategy comparison: Complete knockout vs. partial knockdown effects

    • In vitro vs. in vivo discrepancies: Address physiological relevance of findings

  • Pathway Interconnection Analysis:

    • AMPK/mTOR status: Document baseline activity in each experimental system

    • Nutrient conditions: Standardize and report culture media composition

    • Stress conditions: Account for variations in cellular stress levels

  • Integrated Data Resolution Approach:

    • Perform rescue experiments with defined FNIP1 constructs

    • Use domain-specific mutations to isolate function-specific effects

    • Implement time-course analyses to distinguish primary from secondary effects

Research has demonstrated that FNIP1's functions include roles in mTOR signaling, HSP90 co-chaperoning, and B cell development, which may manifest differently depending on cellular context .

What quality control metrics should be applied when evaluating antibody-based FNIP1 detection methods?

Implementing rigorous quality control for FNIP1 antibody applications requires these quantitative and qualitative assessments:

  • Antibody Performance Metrics:

    • Signal-to-noise ratio: Calculate and maintain ≥5:1 for quantitative applications

    • Coefficient of variation: Maintain <15% for technical replicates

    • Limit of detection: Determine minimum detectable FNIP1 concentration

    • Dynamic range: Establish linear detection range for quantitative assays

  • Specificity Verification:

    • Single band/signal verification: Confirm expected molecular weight (130 kDa)

    • Signal reduction quantification: ≥80% signal reduction in knockdown/competition assays

    • Cross-reactivity assessment: Test against FNIP2 and related proteins

  • Reproducibility Standards:

    • Batch-to-batch consistency: Compare lot numbers using consistent samples

    • Inter-laboratory validation: Exchange protocols and samples with collaborators

    • Long-term stability monitoring: Test antibody performance over defined time intervals

  • Application-specific Controls:

    • For ELISA: Generate standard curves with recombinant FNIP1 (R² > 0.98)

    • For Western blotting: Include loading controls and molecular weight markers

    • For microscopy: Implement fluorescence intensity standardization

Maintain detailed documentation of all quality control measures to ensure data reliability and facilitate troubleshooting when inconsistencies arise.

How do recent findings on FNIP1's role in metabolic checkpoints inform experimental design?

Recent discoveries regarding FNIP1's function as a metabolic checkpoint regulator offer several experimental design considerations:

  • Pre-B Cell Developmental Studies:

    • Design experiments investigating the metabolic capacity requirements for B cell division

    • Implement measurements of mitochondrial function during developmental transitions

    • Assess FNIP1 expression correlation with metabolic enzyme activity

    • Investigate threshold levels of FNIP1 required for developmental progression

  • Oncogenic Transformation Models:

    • Develop assays monitoring FNIP1 status during B cell transformation

    • Create experimental systems with controlled FNIP1 expression in lymphoma models

    • Assess synergy between FNIP1 deletion and oncogene activation

    • Monitor sensitivity to apoptosis under metabolic stress conditions

  • AMPK/mTOR Pathway Integration:

    • Design dual-reporter systems for simultaneous monitoring of AMPK and mTOR activity

    • Implement optogenetic tools to manipulate FNIP1 activity with temporal precision

    • Develop assays monitoring the FNIP1-dependent response to nutrient fluctuations

    • Create FNIP1 mutants unable to respond to specific metabolic signals

Research has demonstrated that FNIP1 deletion causes dysregulation of metabolic regulators AMPK and mTOR, resulting in excessive cell growth and enhanced sensitivity to apoptosis in response to metabolic stress, presenting a potential therapeutic target for lymphomas characterized by deregulated growth .

What are the technical considerations for studying post-translational modifications of FNIP1?

Investigating FNIP1's post-translational modifications requires specialized methodological approaches:

  • Phosphorylation Analysis:

    • Implement Phos-tag™ SDS-PAGE for mobility shift detection

    • Perform IP with biotin-conjugated FNIP1 antibodies followed by phospho-specific Western blotting

    • Utilize mass spectrometry to identify phosphorylation sites:

      • Sample preparation: IMAC enrichment of phosphopeptides

      • Instrumentation: High-resolution MS/MS with ETD or HCD fragmentation

      • Data analysis: Site localization probability scoring (>0.75 threshold)

    • Compare phosphorylation patterns following CK2 inhibition or ULK1 activation

  • Ubiquitination Studies:

    • Detect polyubiquitylation through tandem ubiquitin binding entities (TUBEs) pulldown

    • Implement IP under denaturing conditions to eliminate associated proteins

    • Distinguish K48 vs. K63-linked chains using linkage-specific antibodies

    • Monitor ubiquitination kinetics under reductive stress conditions

  • Redox Modification Assessment:

    • Implement redox proteomics to identify Cys oxidation states

    • Use biotin-switch technique to detect reversible Cys modifications

    • Employ diagonal electrophoresis to identify disulfide bond formation

    • Create Cys mutants to validate redox-sensitive residues

Research indicates FNIP1 undergoes gradual phosphorylation by CK2 and phosphorylation by ULK1. Additionally, under reductive stress, FNIP1's conserved Cys degron is reduced, leading to recognition and polyubiquitylation by the CRL2(FEM1B) complex .

What methodological approaches can elucidate FNIP1's role in the lysosomal folliculin complex (LFC)?

To investigate FNIP1's function within the lysosomal folliculin complex, researchers should implement these specialized approaches:

  • Dynamic Interaction Mapping:

    • Proximity labeling techniques (BioID, APEX) fused to FNIP1

    • FLIM-FRET analysis of FNIP1-FLCN interactions at lysosomes

    • Single-molecule tracking of fluorescently labeled FNIP1

    • Live-cell imaging with amino acid modulation

  • Lysosomal Proteomics:

    • Lysosomal immunoprecipitation followed by mass spectrometry

    • Stable isotope labeling (SILAC) to compare LFC composition under different conditions

    • Identification of post-translational modifications occurring at lysosomes

    • Cross-linking mass spectrometry to identify protein-protein interfaces

  • Functional Dissection Assays:

    • Domain mapping through truncation and point mutations

    • LFC reconstitution assays with purified components

    • In vitro GTPase activity measurements of FLCN in presence/absence of FNIP1

    • Structure-function analysis using cryo-EM of the assembled complex

  • Nutrient Sensing Circuit Analysis:

    • Real-time monitoring of mTORC1 recruitment to lysosomes

    • TFEB/TFE3 nuclear translocation dynamics under amino acid modulation

    • Correlation of FNIP1 lysosomal localization with Rag GTPase nucleotide status

    • Develop biosensors for LFC assembly/disassembly

Research indicates FNIP1 is a component of the lysosomal folliculin complex on lysosomal membranes, where it inhibits FLCN's GTPase-activating activity in low-amino acid conditions, inactivating mTORC1 and promoting nuclear translocation of TFEB and TFE3. Upon amino acid restimulation, the LFC complex disassembles, liberating FLCN's GTPase-activating activity .

How can multiomics approaches enhance understanding of FNIP1 function in cellular metabolism?

Implementing integrated multiomics strategies provides comprehensive insights into FNIP1's metabolic regulatory functions:

  • Combined Omics Experimental Design:

    • Parallel transcriptomics, proteomics, and metabolomics from the same samples

    • Compare FNIP1 wildtype, knockout, and rescue conditions

    • Include time-course analysis following metabolic perturbations

    • Develop computational integration frameworks for data synthesis

  • Transcriptomics Applications:

    • RNA-seq to identify FNIP1-responsive gene networks

    • Focus on metabolic enzyme transcripts and AMPK/mTOR targets

    • Analyze alternative splicing patterns affected by FNIP1 status

    • Implement ATAC-seq to assess chromatin accessibility changes

  • Proteomics Strategies:

    • Global proteome analysis with high-resolution MS

    • Phosphoproteomics focusing on AMPK/mTOR signaling nodes

    • Protein turnover assessment using pulse-chase SILAC

    • Protein-protein interaction mapping via AP-MS with biotin-FNIP1 antibodies

  • Metabolomics Approaches:

    • Untargeted LC-MS/MS to identify metabolite signature changes

    • Stable isotope tracing to track metabolic flux alterations

    • Lipidomics to assess membrane composition changes

    • Analysis of TCA cycle and glycolytic intermediates

Research shows FNIP1 deletion causes dysregulation of AMPK and mTOR, suggesting multiomics approaches would reveal downstream effects on cellular metabolism spanning transcriptional regulation to metabolite utilization patterns .

What are the best practices for designing in vivo experiments to study FNIP1 function?

Design rigorous in vivo experiments to study FNIP1 function using these methodological guidelines:

  • Genetic Model Development:

    • Generate tissue-specific conditional Fnip1 knockout models

    • Implement inducible systems (e.g., tamoxifen-inducible Cre) for temporal control

    • Create knock-in reporter models (e.g., FNIP1-GFP) for localization studies

    • Develop point mutation models targeting specific functional domains

  • Experimental Design Principles:

    • Ensure proper controls: littermate comparisons, Cre-only controls

    • Implement blinding and randomization protocols

    • Calculate appropriate sample sizes based on expected effect sizes

    • Include both sexes and multiple age points in analysis

  • Phenotypic Analysis Framework:

    • Comprehensive immune cell profiling via flow cytometry

    • Metabolic phenotyping (glucose tolerance, insulin sensitivity)

    • Challenge models (nutrient restriction, metabolic stress inducers)

    • Longitudinal studies to capture developmental aspects

  • Molecular Analysis Approaches:

    • In situ detection of FNIP1 using validated antibodies

    • Ex vivo analysis of isolated primary cells

    • Tissue metabolomics to assess metabolic alterations

    • Single-cell sequencing to capture cellular heterogeneity

Research with FNIP1-null mice revealed multiple phenotypes including B cell development block, alterations in skeletal muscle, increased liver glycogen content, and hypertrophic cardiomyopathy, highlighting the importance of comprehensive phenotyping approaches .

How should researchers approach contradictions between in vitro and in vivo findings on FNIP1 function?

When reconciling disparities between in vitro and in vivo FNIP1 findings, implement this methodological framework:

  • Systematic Comparison Analysis:

    • Create side-by-side documentation of contradictory findings

    • Identify key variables differing between systems:

      • Nutrient conditions (culture media vs. physiological fluctuations)

      • Oxygen tension (normoxia vs. tissue-specific oxygen levels)

      • Cell-cell interactions (monoculture vs. tissue microenvironment)

      • Temporal aspects (acute vs. chronic adaptations)

  • Bridging Experimental Approaches:

    • Implement ex vivo organ culture systems

    • Develop 3D organoid models recapitulating tissue architecture

    • Use primary cells with minimal time in culture

    • Design in vitro systems that mimic physiological conditions

  • Mechanistic Reconciliation Strategies:

    • Identify threshold effects present in one system but not the other

    • Assess compensatory mechanisms active in vivo but absent in vitro

    • Investigate tissue-specific cofactors or interaction partners

    • Examine developmental timing considerations

  • Integrated Validation Framework:

    • Test in vitro-derived hypotheses in vivo using genetic models

    • Validate in vivo observations using reconstituted in vitro systems

    • Implement pharmacological approaches across both systems

    • Develop computational models integrating findings from both contexts

The complex functions of FNIP1 in mTORC1 signaling, HSP90 co-chaperoning, and developmental regulation underscore the importance of integrated approaches to understand its context-dependent roles .

How can CRISPR-based approaches advance the study of FNIP1 biology?

CRISPR technologies offer powerful tools for dissecting FNIP1 function through these methodological approaches:

  • Domain-Specific Functional Analysis:

    • Generate precise domain deletions or point mutations

    • Create allelic series targeting different FNIP1 functional regions:

      • FLCN interaction domain

      • AMPK binding region

      • HSP90 interaction sites

      • Phosphorylation sites important for regulation

    • Implement base editing for single amino acid substitutions

    • Develop CRISPR interference/activation systems for tunable expression

  • Spatiotemporal Regulation Studies:

    • Implement optogenetic or chemically-inducible CRISPR systems

    • Create cellular mosaics for comparative analysis

    • Develop tissue-specific gene editing approaches in vivo

    • Design lineage-tracing systems coupled with FNIP1 modifications

  • Interaction Network Mapping:

    • Employ CRISPR screens to identify synthetic lethal interactions

    • Implement perturb-seq for single-cell transcriptional profiling

    • Design pooled CRISPR screens under metabolic stress conditions

    • Develop proximity-based genetic screens for FNIP1 interactors

  • High-throughput Phenotypic Analysis:

    • Create CRISPR libraries targeting FNIP1 regulatory regions

    • Implement multi-parameter phenotypic readouts

    • Design reporter systems for metabolic pathway activities

    • Develop machine learning approaches for complex phenotype analysis

These approaches would help clarify FNIP1's roles in B cell development, metabolic regulation, and potential contributions to disease pathogenesis .

What special considerations apply when using FNIP1 antibodies in multiplexed imaging techniques?

When implementing biotin-conjugated FNIP1 antibodies in advanced multiplexed imaging, consider these methodological requirements:

  • Panel Design Optimization:

    • Spectral overlap management: Separate streptavidin-fluorophore signal from other channels

    • Epitope access considerations: Use gentle fixation methods (2% PFA, short duration)

    • Signal amplification calibration: Titrate streptavidin conjugates to avoid oversaturation

    • Order of application: Place biotin-FNIP1 detection early in sequential staining protocols

  • Technical Implementation Strategies:

    • Endogenous biotin blocking: Use avidin/biotin blocking kit prior to antibody application

    • Signal-to-noise optimization: Implement image processing algorithms for background subtraction

    • Autofluorescence management: Use spectral unmixing or tissue autofluorescence quenching

    • Antibody cross-reactivity prevention: Include thorough washing steps with detergents

  • Validation Approaches:

    • Single-stain controls: Establish spectral profiles for each antibody

    • Fluorescence minus one (FMO) controls: Verify specificity in multiplex context

    • Serial section comparison: Correlate with chromogenic IHC results

    • Resolution standards: Use structured illumination patterns to assess effective resolution

  • Advanced Multiplexing Methods:

    • Cyclic immunofluorescence: Optimize elution conditions preserving tissue integrity

    • Mass cytometry adaptation: Conjugate non-biotin FNIP1 antibodies with metal isotopes

    • DNA-barcoded antibody strategies: Implement transcoding approaches for multiplexing

    • Spatial proteomics correlation: Integrate with region-specific proteomics data

These considerations ensure reliable detection of FNIP1 in complex tissue environments while maintaining compatibility with other markers in multiplexed systems.

How might current understanding of FNIP1 translate to therapeutic applications?

Translating FNIP1 research toward therapeutic applications requires consideration of these methodological pathways:

  • Target Validation Approaches:

    • Develop conditional rescue models to establish therapeutic windows

    • Identify tissue-specific FNIP1 requirements and potential toxicities

    • Create genetic suppressor screens for compensatory pathways

    • Implement pharmacological modulation of downstream pathways

  • Therapeutic Strategy Development:

    • mTOR pathway modulation: Design selective approaches targeting FNIP1-regulated nodes

    • Metabolic checkpoint targeting: Develop compounds that mimic FNIP1's regulatory effects

    • B cell development modulation: Explore immunomodulatory applications

    • HSP90 co-chaperone targeting: Design molecules that affect FNIP1-HSP90 interactions

  • Biomarker Development Framework:

    • Create detection systems for FNIP1 expression/modification status

    • Develop metabolic signature profiles associated with FNIP1 function

    • Identify patient stratification markers for FNIP1-targeted therapies

    • Implement tissue-specific response indicators

  • Disease Context Applications:

    • Lymphoma/leukemia: Target metabolic vulnerabilities in B cell malignancies

    • Metabolic disorders: Address dysregulated energy sensing pathways

    • Kidney cancer: Explore FLCN-FNIP1 axis in Birt-Hogg-Dubé syndrome

    • Neurodegenerative diseases: Investigate protein quality control applications

Research indicates FNIP1's role as a metabolic checkpoint controller could be exploited therapeutically in conditions characterized by dysregulated cellular metabolism or protein quality control mechanisms .

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