CSF1R (Ab-809) Antibody

What is CSF1R and why is phosphorylation at Tyr809 significant?

CSF1R (Colony Stimulating Factor 1 Receptor), also known as CD115, M-CSFR, or c-Fms, is a transmembrane receptor encoded by the CSF1R gene belonging to the tyrosine kinase receptor family. It is predominantly expressed in monocyte-macrophage lineages and is crucial for their differentiation, proliferation, and survival .

Phosphorylation at Tyr809 is particularly significant because this site provides a specific docking site for the adaptor protein Shc, which is essential for downstream signal transduction . When CSF1R binds its ligands (CSF-1 or IL-34), receptor dimerization and autophosphorylation occur at multiple tyrosine residues, including Tyr809, activating various signaling cascades including PI3K/Akt, MAPK, and STAT pathways .

Unlike other phosphorylation sites such as Tyr723 (which binds PI3K and PLCγ2), Tyr809 specifically recruits Shc, making it a critical node in CSF1R-mediated signaling . Studies have shown that defective autophosphorylation at this residue is associated with hereditary diffuse leukoencephalopathy with spheroids (HDLS) .

The CSF1R (Ab-809) Antibody has been experimentally confirmed to react with:

• Human samples (strongly validated across multiple studies)

• Mouse samples (confirmed reactivity)

While some manufacturers predict potential cross-reactivity with rat samples based on sequence homology, this has not been extensively validated in the provided literature . The immunogen used to develop this antibody was derived from human CSF1R around the phosphorylation site of tyrosine 809 (sequence: S-N-Y(p)-I-V) .

How does CSF1R Tyr809 phosphorylation relate to other phosphorylation sites in signaling cascades?

CSF1R contains multiple key phosphorylation sites that work in concert to orchestrate downstream signaling. Research has demonstrated distinct roles for different phosphorylation sites:

• Tyr723 (Tyr721 in mouse): Binds the p85 subunit of PI3K and PLCγ2, activating PI3K/Akt pathways

• Tyr809: Provides a docking site for Shc adaptor protein, leading to MAPK pathway activation

• Tyr546: Involved in early signaling events following receptor activation

• Tyr699: Contributes to receptor autophosphorylation and activation

Studies examining CSF1R mutations in hereditary diffuse leukoencephalopathy with spheroids (HDLS) reveal that defective autophosphorylation at multiple sites, including Tyr809, is a common feature of disease-causing mutations . Functional studies have demonstrated that these phosphorylation sites are hierarchically regulated, with certain sites being phosphorylated more rapidly than others following ligand binding .

When designing experiments to study CSF1R signaling, researchers should consider examining multiple phosphorylation sites simultaneously, as their interdependence provides a more complete picture of receptor activation status .

What are the best methods to stimulate CSF1R phosphorylation at Tyr809 for positive controls?

For generating reliable positive controls when using CSF1R (Ab-809) Antibody, the following stimulation protocols have been validated:

• Recombinant CSF-1 (M-CSF) stimulation:

  • Serum-starve cells for 16 hours to reduce baseline phosphorylation

  • Treat with 25-50 ng/mL human recombinant CSF-1 for 5-30 minutes

  • This time-dependent stimulation produces robust Tyr809 phosphorylation

• IL-34 stimulation protocol:

  • Alternative ligand that also stimulates CSF1R phosphorylation

  • Similar concentration range (25-50 ng/mL) can be used

  • May produce slightly different phosphorylation kinetics compared to CSF-1

• Cell line selection:

  • HT-29 cells show detectable endogenous CSF1R expression and phosphorylation

  • Macrophage cell lines or primary monocytes provide physiologically relevant models

The phosphorylation at Tyr809 typically peaks between 5-15 minutes after stimulation and may decrease thereafter due to receptor internalization and degradation mechanisms . Time-course experiments are recommended to determine optimal stimulation conditions in your specific experimental system.

How can I validate specificity of CSF1R (Ab-809) Antibody in my experimental model?

Validating antibody specificity is crucial for reliable research outcomes. For CSF1R (Ab-809) Antibody, consider these validation approaches:

• Positive and negative controls:

  • Positive: CSF-1 stimulated cells/tissues known to express CSF1R (e.g., macrophages, microglia)

  • Negative: CSF1R knockout cells or tissues, or cell lines with negligible CSF1R expression

• Peptide competition assay:

  • Pre-incubate the antibody with excess phospho-peptide immunogen (S-N-Y(p)-I-V)

  • This should abolish specific staining/binding in your application

• Phosphatase treatment:

  • Treat one sample set with lambda phosphatase before antibody application

  • This should eliminate signals from phospho-specific antibodies if they are truly phospho-specific

• CRISPR/siRNA knockdown validation:

  • Compare signals in wild-type versus CSF1R knockdown/knockout samples

  • Signals should be substantially reduced in knockdown samples

• Multiple antibody approach:

  • Compare results with other validated anti-CSF1R antibodies targeting different epitopes

  • Consistent patterns across antibodies suggest specific recognition

Published studies have validated this antibody using comparison to non-phosphorylated controls and through analysis of disease models with known CSF1R mutations that affect Tyr809 phosphorylation .

What are common causes of false positives/negatives when using CSF1R (Ab-809) Antibody?

Causes of false negatives:

• Inadequate preservation of phospho-epitopes:

  • Phosphorylation is labile and can be lost during sample processing

  • Solution: Use phosphatase inhibitors (e.g., sodium orthovanadate, sodium fluoride) in all buffers

  • Process samples rapidly and maintain cold temperatures

• Insufficient antigen retrieval (for IHC/IF):

  • Phospho-epitopes may be masked by fixation

  • Solution: Optimize antigen retrieval methods (heat-induced epitope retrieval with citrate or EDTA buffers)

• Low receptor expression levels:

  • CSF1R expression varies across tissues and cell types

  • Solution: Use signal amplification methods or more sensitive detection systems

Causes of false positives:

• Cross-reactivity with similar phospho-motifs:

  • Other phosphorylated tyrosine residues in similar sequence contexts

  • Solution: Include proper negative controls and validate with alternative methods

• Non-specific binding at high antibody concentrations:

  • Solution: Titrate antibody to optimal concentration and include appropriate blocking steps

  • Use the recommended dilutions: WB (1:500-1:3000), IHC (1:50-1:100), IF (1:100-1:500)

• Background from detection systems:

  • High background can mask or mimic specific signals

  • Solution: Optimize blocking conditions and secondary antibody dilutions

Importantly, western blot analysis of CSF1R typically reveals multiple bands: ~175 kDa (mature form), ~140 kDa (immature/precursor form), and ~55 kDa (cleaved C-terminal fragment) . Understanding this complex pattern helps avoid misinterpretation of results.

How can I use CSF1R (Ab-809) Antibody effectively in cancer research studies?

CSF1R signaling has significant implications in cancer biology, particularly in understanding tumor-associated macrophages (TAMs) and potential therapeutic targets. For effective use in cancer research:

• Tumor microenvironment studies:

  • Use CSF1R (Ab-809) Antibody to assess phosphorylation status in different tumor regions

  • Combine with macrophage markers (CD68, Iba1) to correlate with immune infiltration

  • Research has shown CSF1R overactivation can lead to malignant phenotypes and correlates with poor outcomes in epithelial ovarian carcinoma and breast cancer

• Therapeutic response monitoring:

  • Monitor changes in CSF1R Tyr809 phosphorylation following CSF1R inhibitor treatment

  • CSF1R inhibitors (e.g., PLX3397) have shown anti-tumor effects by modulating TAM polarization

• Multi-parameter analysis approaches:

  • Combine with other phospho-specific antibodies (p-Tyr723, p-Tyr546) to generate a comprehensive signaling profile

  • Include downstream effectors (phospho-ERK, phospho-AKT) to link receptor activation to cellular outcomes

• Patient-derived samples:

  • When analyzing clinical specimens, consider tissue fixation time (shorter is better for phospho-epitopes)

  • Compare matched normal and tumor tissues from the same patient when possible

Recent studies have demonstrated that CSF1R blockade delays tumor growth by shifting TAM polarization rather than depleting TAMs entirely . This antibody can help monitor these changes at the molecular level and provide mechanistic insights.

What approaches can resolve contradictory results between phospho-CSF1R detection methods?

When facing contradictory results in CSF1R phosphorylation studies, consider these resolution strategies:

• Technical validation across platforms:

  • If WB and IHC/IF results differ, perform both techniques on identical samples

  • Include appropriate controls for each technique separately

  • Consider sample processing differences that might affect phospho-epitope preservation

• Investigate temporal dynamics:

  • CSF1R phosphorylation is dynamic and time-dependent

  • Different detection methods may have varying sensitivities to phosphorylation kinetics

  • Perform detailed time-course experiments using consistent stimulation protocols

• Examine cellular heterogeneity:

  • Single-cell techniques (flow cytometry, imaging) can reveal heterogeneous responses masked in bulk assays

  • For heterogeneous tissues, consider laser capture microdissection to isolate specific regions before analysis

• Complementary functional assays:

  • Correlate phosphorylation status with functional outcomes (proliferation, migration, gene expression)

  • Use CSF1R inhibitors or mutants with impaired Tyr809 phosphorylation as functional controls

• Quantitative considerations:

  • Western blot provides semi-quantitative data while IHC is often qualitative

  • Consider phospho-flow cytometry for quantitative single-cell analysis

How does autophagy regulation relate to CSF1R Tyr809 phosphorylation?

Recent studies have uncovered intriguing connections between CSF1R signaling and autophagy regulation that can be investigated using CSF1R (Ab-809) Antibody:

• CSF1R mutations and autophagy:

  • Research has demonstrated that CSF1R mutations causing HDLS lead to defective autophagy

  • CSF1R mutants with impaired Tyr809 phosphorylation show lower levels of LC3-II, a marker of autophagy activation

  • In vitro studies revealed decreased LC3 accumulation in cells expressing CSF1R mutants compared to wild-type CSF1R

• Experimental approaches:

  • Co-stain for phospho-CSF1R (Tyr809) and autophagy markers (LC3, p62) to correlate signaling with autophagy status

  • Monitor changes in autophagy flux following CSF1R activation or inhibition

  • Use CSF1R Tyr809 phosphorylation status as a predictor of autophagy regulation potential

• Disease implications:

  • Defective autophagy resulting from impaired CSF1R signaling may contribute to neurodegenerative pathology in HDLS

  • This connection provides a mechanistic link between CSF1R signaling and cellular homeostasis

Quantitative analysis of LC3-II levels relative to phospho-CSF1R (Tyr809) can help establish the relationship between receptor activation and autophagy regulation in various experimental systems.

How can I correlate CSF1R Tyr809 phosphorylation with functional outcomes in immune cells?

For researchers investigating immune cell function in relation to CSF1R signaling:

• Macrophage polarization assays:

  • Monitor Tyr809 phosphorylation during M1/M2 polarization

  • Studies show CSF1R inhibition shifts tumor-associated macrophages toward M1-like phenotype

  • Correlate phosphorylation status with expression of polarization markers (CD80, CD206, etc.)

• Migration and invasion assays:

  • Assess cell motility following CSF1R stimulation or inhibition

  • Quantify Tyr809 phosphorylation at different time points during migration processes

  • CSF1R signaling is known to promote cell migration and invasion through cytoskeletal remodeling

• Proliferation and survival analysis:

  • Measure BrdU incorporation or Ki-67 staining in relation to Tyr809 phosphorylation

  • Use flow cytometry to correlate phospho-CSF1R levels with cell cycle progression

  • Research has shown CSF1R-deficient mice display reduced microglial proliferation and abnormal morphology

• Gene expression profiling:

  • Perform RNA-seq or qPCR for CSF1R-regulated genes following receptor activation

  • Compare transcriptional profiles between cells with normal versus impaired Tyr809 phosphorylation

  • Correlate phosphorylation status with expression of key target genes

When conducting these experiments, time-resolved analysis is crucial, as CSF1R signaling dynamics may vary depending on the functional outcome being assessed. The CSF1R (Ab-809) Antibody provides a valuable tool for monitoring this specific phosphorylation event in relation to these functional parameters.

What are the implications of CSF1R Tyr809 phosphorylation in neurological disease research?

The CSF1R (Ab-809) Antibody has particular relevance in neurological disease research:

• Hereditary Diffuse Leukoencephalopathy with Spheroids (HDLS):

  • CSF1R mutations are causative in HDLS, a rare white matter disease

  • Multiple studies have demonstrated that these mutations lead to defective autophosphorylation at Tyr809

  • Western blot analysis of brain tissues from HDLS patients shows reduced CSF1R expression and impaired phosphorylation

• Microglial function in neurodegeneration:

  • CSF1R is expressed in microglia and regulates their survival and function

  • Phosphorylation at Tyr809 is critical for normal microglial responses

  • Immunohistochemistry studies of HDLS brains show abnormal microglial morphology and reduced CSF1R immunopositivity

• Experimental approaches:

  • Compare phospho-CSF1R (Tyr809) levels in normal versus diseased brain tissues

  • Study the effects of CSF1R inhibitors on microglial activation and neuroinflammation

  • Use transgenic models expressing CSF1R mutations to understand phosphorylation-dependent functions

• Therapeutic implications:

  • CSF1R inhibitors are being investigated as potential treatments for neuroinflammatory conditions

  • Monitoring Tyr809 phosphorylation can help assess target engagement and efficacy

Recent studies have revealed that impaired CSF1R-mediated microglial repair of axonal degeneration may contribute to white matter pathology, and that CSF1R may also play direct roles in neuronal survival and differentiation . These findings highlight the importance of understanding CSF1R phosphorylation in the context of neurological disease.

Research has shown that CSF1R haploinsufficiency in HDLS leads to characteristic clinical and neuroimaging features, regardless of the specific mutation type in CSF1R . The CSF1R (Ab-809) Antibody provides a valuable tool for investigating these disease mechanisms at the molecular level.