FLD Antibody

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Description

Definition and Target

FLD antibodies are immunoglobulins engineered to bind the fibrinogen-like domain of ANGPTL3, a liver-secreted protein involved in lipid metabolism and endothelial cell regulation . The FLD region mediates ANGPTL3's interaction with lipoprotein lipase (LPL), making it a critical target for modulating lipid levels and podocyte function .

Development and Screening

The monoclonal antibody 5E5F6 was developed through:

StepMethodologyOutcome
ImmunizationBALB/c mice with human ANGPTL3-FLD40 hybridoma clones generated
Primary screeningELISA against ANGPTL3-FLD20 clones positive for binding
Secondary validationImmunoblotting with E. coli lysates4 clones with strong reactivity
Production scalingTransient expression analysis5E5F6 selected for high yield

Therapeutic Efficacy in Renal Disease

  • Adriamycin (ADR)-induced nephropathy:

    • FLD antibody treatment reduced proteinuria by 58% (p < 0.01) and attenuated podocyte foot process effacement .

    • Mitochondrial damage markers (e.g., ROS) decreased by 40% .

  • Puromycin aminonucleoside (PAN) model:

    • Podocyte apoptosis was inhibited by 35% via caspase-3 pathway suppression .

Mechanistic Insights

  • Lipid metabolism: FLD antibody binding restores LPL activity, reducing serum triglycerides by 30% in hyperlipidemic models .

  • Podocyte protection: Downregulates pro-apoptotic Bax/Bcl-2 ratio and stabilizes mitochondrial membrane potential .

Applications and Clinical Relevance

ApplicationMechanismCurrent Status
HypertriglyceridemiaANGPTL3-FLD inhibition enhances LPLPreclinical validation
Diabetic nephropathyPodocyte mitochondrial protectionPhase I trials pending
AtherosclerosisReduces vascular lipid accumulationIn vitro studies ongoing

Available Research Resources

  • Antibody Registry: Universal identifiers for tracking FLD antibodies (e.g., 5E5F6) .

  • CoV-AbDab: Structural models for cross-reactive antibodies .

  • Validated Antibody Database (VAD): Application-specific validation data .

Product Specs

Buffer
Preservative: 0.03% Proclin 300
Constituents: 50% Glycerol, 0.01M PBS, pH 7.4
Form
Liquid
Lead Time
Made-to-order (14-16 weeks)
Synonyms
FLD antibody; SOF1 antibody; At3g10390 antibody; F13M14.34 antibody; F14P13.1Protein FLOWERING LOCUS D antibody; EC 1.-.-.- antibody; Protein SUPPRESSOR OF OVEREXPRESSED FCA 1 antibody
Target Names
FLD
Uniprot No.

Target Background

Function
FLD (FLOWERING LOCUS D) is a probable histone demethylase that plays a crucial role in promoting flowering. It operates independently of the photoperiod and vernalization pathways by repressing the expression of FLOWERING LOCUS C (FLC), a floral repressor that inhibits the transition from vegetative to reproductive development. FLD likely mediates histone H3 'Lys-4' demethylation at the FLC locus. It appears to act in partial redundancy with LDL1 and LDL2 in repressing FLC expression. FLD is essential for histone H4 deacetylation of the FLC locus and may be a component of the histone deacetylase complex. It forms a histone deacetylase complex with HDA5, HDA6, and MSI4/FVE, which collectively repress FLC gene expression to regulate flowering time.
Gene References Into Functions
  1. Plant cells likely utilize a distinct mechanism to direct their KDM1 chromatin-modifying enzymes to methylated histones of the target chromatin compared to mammalian cells. PMID: 26826387
  2. HDA6 and FLD may collaborate within a protein complex. Elevated levels of histone H3 acetylation and H3K4 trimethylation indicate a functional interplay between histone deacetylase and demethylase through the interaction of HDA6 and FLD in flowering control. PMID: 21398257
  3. The Arabidopsis flowering locus D influences the systemic-acquired-resistance-induced expression and histone modifications of WRKY genes. PMID: 24499796
  4. Research suggests that conformational changes in BRASSINAZOLE-RESISTANT1 (BZR1), mediated by cyclophilin (CYP20-2), may directly regulate the expression of FLOWERING LOCUS D (FLD), influencing flowering. PMID: 23897924
  5. FLD's role in systemic acquired resistance (SAR) is independent of FLC. PMID: 23745676
  6. There is a close association between FCA and FLD in mediating H3K4 demethylation and subsequent transcriptional silencing of FLC. PMID: 17996704
  7. Evidence indicates that by repressing FLD activity through sumoylation, SIZ1 promotes FLC expression. PMID: 18069938

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Database Links

KEGG: ath:AT3G10390

STRING: 3702.AT3G10390.1

UniGene: At.39938

Protein Families
Flavin monoamine oxidase family

Q&A

What is an FLD antibody and what biological structures does it target?

FLD antibodies primarily target the Fibrinogen-Like Domain of proteins such as ANGPTL3. In research contexts, anti-ANGPTL3-FLD monoclonal antibodies have demonstrated therapeutic potential by ameliorating podocyte lesions through attenuation of mitochondrial damage . These antibodies specifically recognize the fibrinogen-like domain structure, which is conserved across several proteins but contains sufficient variability to allow for specific targeting.

How are FLD antibodies typically generated in laboratory settings?

The generation of FLD antibodies, particularly those targeting ANGPTL3-FLD, follows a systematic approach involving several key steps:

  • Immunization of BALB/c mice with human ANGPTL3 recombinant protein

  • Hybridoma production through standard protocols

  • Initial screening via Enzyme-linked immunosorbent assays (ELISAs) against the human ANGPTL3-FLD sequence

  • Secondary screening through immunoblotting using cell lysates from Escherichia coli expressing the target protein (e.g., mouse ANGPTL3-FLD)

  • Selection of top clones showing strong immunoreactivity for small-scale antibody production

  • Final selection based on antibody expression analysis

In the case of ANGPTL3-FLD antibodies, this process identified clone 5E5F6 (isotype IgG1/Kappa) as having the highest expression among candidate antibodies, making it suitable for functional assessment .

What screening methods are most effective for identifying high-quality FLD antibodies?

A multi-tier screening approach yields the most robust results:

Screening StageMethodologySelection CriteriaTypical Outcomes
Primary ScreenELISA against target FLDBinding affinity30-50 positive clones
Secondary ScreenImmunoblotting with recombinant proteinSpecificity and sensitivity15-25 positive clones
Tertiary ScreenFunctional assaysBiological activity3-5 candidate clones
Final SelectionExpression analysisProduction efficiency1-2 lead candidates

This systematic narrowing approach ensures that only antibodies with optimal binding, specificity, and production characteristics proceed to experimental applications .

How can researchers visualize FLD antibody binding in tissue samples?

For effective visualization of FLD antibody binding in tissue samples, researchers should implement the following protocol:

  • Fix frozen sections of tissue with 4% paraformaldehyde

  • Permeabilize samples using phosphate-buffered saline containing 0.5% Triton X-100

  • Incubate with primary antibodies (such as anti-WT1 and specific FLD antibodies)

  • Apply appropriate fluorophore-conjugated secondary antibodies (e.g., Alexa Fluor 488 or Cy3)

  • Visualize using laser scanning confocal microscopy

This approach provides high-resolution imaging of antibody localization while preserving tissue architecture, allowing researchers to assess both binding patterns and co-localization with other cellular markers.

What techniques can researchers use to evaluate ultrastructural changes associated with FLD antibody treatment?

Transmission electron microscopy (TEM) offers valuable insights into ultrastructural changes following FLD antibody treatment. The recommended protocol includes:

  • Prefixation of kidney tissue or cultured cell samples in 2.5% glutaraldehyde

  • Washing samples in PBS (0.01 M)

  • Postfixation with 1% osmium acid

  • Gradient dehydration in ethanol and acetone

  • Sample embedding for sectioning and visualization

This approach is particularly valuable for assessing mitochondrial morphology and other subcellular structures affected by ANGPTL3-FLD antibody treatment in conditions like podocyte injury .

How can antibody dynamics be modeled to infer biological events such as infection timing?

Modeling antibody dynamics using Bayesian frameworks allows researchers to estimate important biological events such as infection timing. This approach:

  • Incorporates all available information about potential infection times

  • Models antibody production and decay kinetics

  • Can reduce uncertainty in infection time estimates by up to 83% in some systems

  • Works across various parameter settings including antibody decay rate and peak level variation

This methodology is particularly valuable for field research where precise infection timing data is unavailable, opening new opportunities in wildlife disease ecology while demonstrating the broader applications of antibody dynamics modeling .

What computational approaches can optimize FLD antibody specificity for challenging targets?

Designing FLD antibodies capable of discriminating between structurally and chemically similar ligands requires sophisticated computational approaches:

  • Biophysics-informed models can be trained on experimentally selected antibodies

  • These models associate each potential ligand with a distinct binding mode

  • The approach enables prediction of binding profiles for new ligand combinations

  • Most importantly, it allows for the generation of novel antibody sequences with customized specificity profiles

The computational framework optimizes energy functions associated with each binding mode, enabling researchers to design antibodies with either high specificity for a single target or cross-specificity for multiple related targets .

How can phage display experiments be designed to select antibodies with desired specificity profiles?

Effective phage display experiments for FLD antibody selection should follow this structured approach:

  • Design experiments for selection against various combinations of ligands

  • Use the resulting data to build and assess computational models

  • Identify different binding modes associated with specific ligands

  • Validate experimentally by testing variants predicted by the model but not present in the training set

This integrated experimental-computational approach has successfully disentangled binding modes associated with chemically similar ligands, overcoming a significant challenge in antibody design .

How can researchers optimize antibody design to address pathogen evolution challenges?

The COVID-19 pandemic highlighted limitations of antibody therapies against rapidly evolving pathogens. To address this challenge, researchers should:

  • Target highly conserved regions on pathogens where mutations are less likely

  • Anticipate evolutionary changes rather than reacting to them

  • Design antibodies against regions where mutations would compromise pathogen fitness

  • Consider combinations of antibodies targeting different conserved epitopes

As noted by immunology expert Rino Rappuoli: "You have to get ahead of it. To go after regions where it cannot change or where it is extremely difficult for it to mutate." This forward-thinking approach is essential for developing antibodies with sustained effectiveness against evolving pathogens.

How can researchers address epitope similarity challenges when designing specific FLD antibodies?

When targeting domains with structural similarity to other proteins, researchers should:

  • Implement a binding mode identification approach that associates each ligand with a distinct interaction profile

  • Optimize antibody sequences by minimizing energy functions for desired ligands while maximizing them for undesired ones

  • Validate specificity experimentally using direct binding assays against both target and potential cross-reactive proteins

This approach has been validated in generating antibodies with customized specificity profiles, even for challenging targets with high structural similarity .

What strategies can overcome manufacturing and delivery limitations for antibody therapeutics?

Although manufacturing challenges remain significant for antibody therapeutics, several strategies show promise:

  • Engineering antibodies for higher potency and longer half-life (e.g., "LS" antibodies)

  • Developing lower-dose regimens to offset high production costs

  • Focusing on specific applications where antibodies offer unique advantages over vaccines

  • Targeting bacterial pathogens with multiple strains using newer isolation technologies

As noted in recent research: "If you have an outbreak situation where you need to deliver an immune response very rapidly, antibodies are a great solution." This strategic approach can maximize impact while addressing practical limitations.

How can researchers navigate the complexity of antibody deficiencies when studying FLD antibody function?

Understanding antibody deficiencies provides important context for FLD antibody research:

  • The newest classification includes 45 different predominantly antibody deficiencies

  • These disorders affect a person's ability to produce functional versions of one or more antibody types

  • B cells produce antibodies that recognize specific antigens, with each B cell producing a different antibody

  • When a B cell contacts its target antigen, it matures into a plasma cell that produces large quantities of that specific antibody

This fundamental knowledge helps researchers interpret experimental results and design appropriate controls when studying FLD antibody function in various biological contexts.

What emerging technologies might enhance FLD antibody research and applications?

Several emerging technologies hold promise for advancing FLD antibody research:

  • High-throughput sequencing and computational analysis for enhanced specificity control

  • Biophysics-informed models for predicting and generating antibodies with custom specificity profiles

  • Advanced imaging techniques for visualizing antibody-target interactions in situ

  • Novel antibody engineering approaches for bacterial pathogens, including those targeting drug-resistant bacteria

These technologies collectively address current limitations in antibody design, production, and application, opening new possibilities for FLD antibody research.

What lessons from recent therapeutic antibody applications might inform FLD antibody research?

Recent experiences with therapeutic antibodies, particularly during the COVID-19 pandemic, offer valuable insights:

  • Viral evolution can rapidly outpace antibody effectiveness unless conserved epitopes are targeted

  • Mass production capabilities must be considered early in development

  • Careful epitope selection is critical for sustained efficacy

  • Combination approaches may be necessary for adequate coverage against diverse pathogen strains

As researcher Rino Rappuoli notes regarding antibacterial antibodies: "I don't want to be too optimistic, but I don't want to be too pessimistic... Now we can do 100,000 times better than we could do at the time." This balanced perspective acknowledges both challenges and opportunities in the field.

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