Phospho-INSR (Tyr1355) Antibody

What is the structure and function of the Insulin Receptor, and why is Tyr1355 phosphorylation significant?

The insulin receptor (INSR) is a heterodimeric protein complex consisting of an extracellular alpha subunit and an intracellular beta subunit linked by disulfide bonds. The alpha subunit binds insulin, while the beta subunit contains the tyrosine kinase domain responsible for signal transduction.

Tyr1355 phosphorylation represents a key post-translational modification that occurs following insulin binding and subsequent activation of the receptor's intrinsic kinase activity. This phosphorylation site (within the sequence R-S-Y-E-E) plays a crucial role in the recruitment of signaling molecules containing SH2 domains, which ultimately activate downstream pathways including PI3K-AKT/PKB and Ras-MAPK cascades .

These pathways regulate glucose uptake, glycogen synthesis, gene expression, and cell growth. Disruption of insulin receptor phosphorylation contributes to insulin resistance syndromes and metabolic disorders .

What are the common applications for Phospho-INSR (Tyr1355) Antibody?

Phospho-INSR (Tyr1355) Antibody can be utilized across multiple experimental platforms:

The antibody demonstrates reactivity across human, mouse, and rat samples, making it versatile for comparative studies across species .

How should Phospho-INSR (Tyr1355) Antibody be stored and handled?

For optimal preservation of antibody activity:

• Store at -20°C for long-term storage (up to one year)

• For frequent use, aliquot and store at 4°C for up to one month

• Avoid repeated freeze-thaw cycles to prevent denaturation

• Most preparations are supplied in PBS buffer containing preservatives (such as sodium azide) and stabilizers (glycerol, BSA)

• Typical concentration is 1mg/ml

When handling, maintain sterile conditions and avoid contamination. The liquid formulation (typically in PBS with 50% glycerol and 0.02% sodium azide at pH 7.3-7.4) prevents freeze-thaw damage while maintaining antibody stability .

How can researchers distinguish between specific Tyr1355 phosphorylation and other INSR phosphorylation sites?

Distinguishing between different phosphorylation sites requires multi-faceted validation approaches:

• Phospho-specificity validation: Treat sample aliquots with lambda phosphatase before western blotting to confirm the signal is phosphorylation-dependent.

• Peptide competition assay: Pre-incubate the antibody with synthetic phosphopeptide containing the Tyr1355 site (sequence R-S-YP-E-E) before sample probing. Signal loss confirms specificity.

• Site-directed mutagenesis: Compare wild-type INSR with Y1355F mutant receptor expression systems. The mutant should show no reactivity with the phospho-specific antibody.

• Cross-reactivity assessment: Compare with other phospho-INSR antibodies targeting different sites (Tyr999, Tyr1345, Tyr1361) to establish site-specificity patterns.

• Mass spectrometry validation: For ultimate confirmation, use phospho-enrichment followed by mass spectrometry to validate the specific phosphorylation site detected by the antibody.

The sequence surrounding Tyr1355 (R-S-Y-E-E) must be carefully considered when evaluating antibody specificity, as antibodies are generated against synthetic phosphopeptides derived from this region .

What experimental approaches can reveal the temporal dynamics of INSR Tyr1355 phosphorylation?

To capture the dynamic nature of INSR phosphorylation:

• Fine-grained time course: Stimulate cells with insulin and collect samples at short intervals (0, 30s, 1m, 2m, 5m, 10m, 15m, 30m, 1h, 2h) to map the complete phosphorylation profile.

• Phosphatase inhibitor optimization: Include varying concentrations of phosphatase inhibitors (sodium orthovanadate, sodium fluoride, etc.) to prevent rapid dephosphorylation during sample processing.

• High-throughput cell-based ELISA: Use specialized kits like the IR Phospho-Tyr1355 Colorimetric Cell-Based ELISA for higher-throughput temporal analysis across multiple conditions .

• Multiplexed phospho-antibody arrays: Implement insulin receptor phospho antibody arrays to simultaneously monitor multiple phosphorylation sites, establishing the hierarchy and temporal relationships between different phosphorylation events .

• Live-cell imaging: For spatial-temporal dynamics, combine the antibody with cell-permeable phospho-specific probes in fixed-time point imaging series.

Experiments should include both dose-response (varying insulin concentrations) and temporal components to fully characterize INSR phosphorylation dynamics at Tyr1355.

How does insulin receptor phosphorylation at Tyr1355 differ functionally from other phosphorylation sites?

The functional significance of Tyr1355 phosphorylation must be understood in the context of the entire insulin receptor signaling cascade:

• Differential signaling pathway activation: While autophosphorylation sites (Tyr1146/1150/1151) directly regulate kinase activity, Tyr1355 appears to function primarily in downstream adaptor protein recruitment .

• Sequential phosphorylation events: Evidence suggests a hierarchical phosphorylation pattern where autophosphorylation sites are modified first, followed by substrate recruitment sites like Tyr1355.

• Substrate selectivity: Tyr1355 phosphorylation creates a specific binding motif (phospho-YXXM) that preferentially recruits particular SH2 domain-containing proteins to activate PI3K-AKT signaling versus Ras-MAPK pathways .

• Metabolic versus mitogenic signaling: Phosphorylation at Tyr1355 appears to favor metabolic responses (glucose uptake, glycogen synthesis) over cell growth/proliferation signals compared to other sites.

• Differential regulation by phosphatases: Different phospho-sites show distinct temporal dynamics due to variable targeting by specific protein tyrosine phosphatases (PTPs).

Research using site-specific mutants and phospho-specific antibodies suggests that Tyr1355 phosphorylation contributes to metabolic insulin signaling while other sites may have more pronounced effects on mitogenic pathways .

What are common sources of false negative results when detecting INSR Tyr1355 phosphorylation and how can they be addressed?

Several factors can lead to false negative results:

• Rapid dephosphorylation: Phosphorylation can be extremely transient. Ensure samples are:

  • Collected rapidly

  • Immediately placed in appropriate lysis buffer containing phosphatase inhibitors

  • Kept cold throughout processing

  • Processed with minimal delay

• Insufficient stimulation: Insulin signaling requires:

  • Fresh, active insulin

  • Appropriate concentration (typically 10-100 nM)

  • Proper stimulation timing (peak phosphorylation often at 5-15 minutes)

• Antibody quality issues:

  • Verify antibody hasn't degraded through storage

  • Confirm phospho-specificity using controls

  • Test antibody on known positive samples (insulin-stimulated adipocytes or hepatocytes)

• Inappropriate sample preparation:

  • Ensure buffer compatibility (avoid detergents that may interfere with epitope recognition)

  • Include proper detergents to solubilize membrane-associated receptors

  • Maintain appropriate protein concentration (1-2 mg/ml typically optimal)

• Detection system limitations:

  • Consider higher sensitivity detection methods (ECL-Plus or similar)

  • For weaker signals, employ signal enhancement techniques

Implementing phospho-enrichment steps (phosphotyrosine immunoprecipitation before western blotting) can significantly improve detection of low-abundance phosphorylated species .

What strategies can improve detection sensitivity for INSR Tyr1355 phosphorylation in tissues with low insulin receptor expression?

When working with challenging samples:

• Sample enrichment strategies:

  • Immunoprecipitate total INSR before probing for phospho-specific detection

  • Use phosphotyrosine antibody enrichment followed by INSR detection

  • Consider cell/tissue fractionation to concentrate membrane fractions containing INSR

• Signal amplification methods:

  • Utilize tyramide signal amplification (TSA) for immunohistochemistry

  • Employ biotin-streptavidin systems to enhance detection

  • Consider more sensitive substrates for colorimetric/chemiluminescent detection

• Optimized protocols for specific tissues:

  • Adipose tissue: Use specialized lysis buffers to handle high lipid content

  • Muscle tissue: Employ mechanical homogenization techniques

  • Brain tissue: Consider region-specific protocols

• Alternative detection platforms:

  • For extremely low signals, consider IR Phospho-Tyr1355 Colorimetric Cell-Based ELISA

  • Utilize phospho-specific antibody arrays with fluorescent detection

  • Implement digital droplet PCR for indirect measurement of phosphorylation response genes

• Experimental manipulations:

  • Use phosphatase inhibitors at higher concentrations

  • Consider insulin receptor overexpression models

  • Employ insulin sensitizers to enhance receptor phosphorylation

The optimal dilution range for detection varies by application: Western blot (1:500-1:2000), IHC (1:100-1:500), and ELISA (1:500-1:10000) .

How can researchers reconcile contradictory results between different detection methods for INSR Tyr1355 phosphorylation?

Methodological differences can lead to apparently conflicting results:

• Understand methodological biases:

  • Western blotting measures denatured proteins, potentially exposing epitopes hidden in native conformation

  • ELISA preserves native structure but may have accessibility issues

  • Immunohistochemistry provides spatial context but may have fixation-dependent artifacts

  • Flow cytometry measures intact cells but requires permeabilization

• Consider temporal factors:

  • Different methods have variable processing times

  • Phosphorylation may be lost during longer procedures

  • Establish synchronized protocols with equivalent time points

• Evaluate epitope accessibility:

  • Fixation can mask epitopes in IHC that are detectable in WB

  • Some detergents may enhance or inhibit antibody binding

  • Native protein interactions may block Tyr1355 in some contexts

• Compare quantification approaches:

  • Normalize phospho-signal to total INSR consistently across methods

  • Use absolute quantification methods where possible

  • Employ phosphopeptide standards for calibration

• Validate with orthogonal techniques:

  • Confirm key findings with mass spectrometry

  • Use genetic approaches (Y1355F mutation) to validate specificity

  • Employ site-specific pharmacological tools

When publishing, report all methodological details including extraction buffers, antibody dilutions, incubation times, and detection systems to enable proper interpretation of results .

How can Phospho-INSR (Tyr1355) Antibody be utilized to study cross-talk between insulin signaling and inflammation?

Insulin resistance frequently involves inflammatory pathway activation. Research approaches include:

• Stimulation protocols:

  • Sequential treatment (e.g., TNF-α pretreatment followed by insulin)

  • Co-stimulation experiments

  • Time-course analysis of both pathways

• Cell models for pathway interaction:

  • Co-culture systems (e.g., adipocytes with macrophages)

  • Cells expressing reporters for both pathways

  • Primary cells from models of metabolic inflammation

• Biochemical approaches:

  • Immunoprecipitation of signaling complexes

  • Proximity ligation assays to detect protein interactions

  • Phospho-proteomic analysis focusing on insulin and inflammatory pathways

• Data analysis considerations:

  • Pathway enrichment analysis

  • Network modeling of signaling interactions

  • Quantitative analysis of phosphorylation stoichiometry

Published studies have demonstrated that inflammatory cytokines can impair insulin-stimulated INSR phosphorylation at Tyr1355, which can be counteracted by anti-inflammatory agents like anthocyanins from purple corn and cocoa shell phenolic extracts .

What experimental designs best utilize Phospho-INSR (Tyr1355) Antibody to investigate insulin resistance mechanisms?

Comprehensive experimental approaches include:

• In vitro models:

  • Induce insulin resistance with free fatty acids, high glucose, glucocorticoids

  • Compare acute vs. chronic insulin treatment (receptor desensitization)

  • Use siRNA knockdown of pathway components to identify key mediators

• Ex vivo tissue analysis:

  • Compare insulin-stimulated phosphorylation in tissues from normal vs. diabetic models

  • Analyze receptor phosphorylation across multiple tissues (liver, muscle, adipose)

  • Perform insulin dose-response curves in tissue explants

• In vivo approaches:

  • Tissue-specific insulin receptor knockout/knockin models

  • Diet-induced obesity and insulin resistance models

  • Time-course analysis following insulin tolerance tests

• Therapeutic intervention studies:

  • Test compounds that potentially enhance insulin sensitivity

  • Monitor changes in Tyr1355 phosphorylation following treatment with metformin or thiazolidinediones

  • Correlate receptor phosphorylation with physiological outcomes

Recent research demonstrated that metformin treatment can repair hepatic insulin signaling in a rat model of acute food insecurity, with phospho-specific antibodies allowing assessment of signaling restoration .

How can comprehensive phosphorylation profiling using antibody arrays that include Phospho-INSR (Tyr1355) advance insulin signaling research?

Phospho-antibody arrays offer significant advantages:

• Multiplexed analysis advantages:

  • Simultaneous detection of multiple phosphorylation sites (219 site-specific and phospho-specific antibodies in some arrays)

  • Consistent experimental conditions across all measurements

  • Reduced sample requirements

  • Higher throughput capability

• Experimental design considerations:

  • Compare phosphorylation patterns between normal and disease states

  • Analyze temporal dynamics across multiple sites

  • Evaluate effects of drug candidates on signaling networks

  • Map pathway cross-talk comprehensively

• Technical implementation:

  • The process involves four major steps:

    • Protein extraction with non-denaturing buffer

    • Biotinylation of protein samples

    • Incubation with antibody array

    • Detection using dye-conjugated streptavidin

• Data analysis approaches:

  • Hierarchical clustering of phosphorylation patterns

  • Principal component analysis to identify key determinants

  • Pathway mapping to visualize network-level changes

  • Time-course modeling of phosphorylation dynamics

• Validation strategies:

  • Confirm key findings with traditional western blotting

  • Correlate with functional outcomes

  • Use phospho-knockout controls to validate specificity

These arrays have been successfully used to analyze insulin signaling in various contexts, including studies on T cell function in adaptive immunity and metabolic inflammation models .

What are the methodological considerations when studying INSR Tyr1355 phosphorylation in spatial context using microscopy techniques?

Microscopy-based approaches require specific considerations:

• Sample preparation optimization:

  • Fixation method selection (paraformaldehyde vs. methanol)

  • Permeabilization protocol optimization

  • Antigen retrieval techniques for tissue sections

  • Blocking protocol adjustment for phospho-epitopes

• Antibody validation for microscopy:

  • Test specificity using phosphatase treatment controls

  • Validate with peptide competition assays

  • Compare staining patterns with total INSR

  • Use insulin stimulation to confirm responsiveness

• Co-localization studies:

  • Pair with markers for specific cellular compartments

  • Co-stain with downstream signaling components

  • Use proximity ligation assay for interaction studies

  • Implement super-resolution techniques for detailed localization

• Quantitative image analysis:

  • Establish consistent signal thresholding

  • Implement cell segmentation for single-cell analysis

  • Perform ratiometric imaging (phospho/total)

  • Consider 3D analysis for tissue architecture

• Dynamic studies:

  • Design methods for rapid fixation post-stimulation

  • Consider live-cell compatible phospho-sensors

  • Implement time-resolved microscopy when possible

Recommended antibody dilutions for microscopy applications include 1:100-1:500 for immunohistochemistry and immunofluorescence studies .