EIF4EBP1 (Ab-36) Antibody

What is EIF4EBP1 and what is its function in cellular processes?

EIF4EBP1 (Eukaryotic Translation Initiation Factor 4E Binding Protein 1) functions as a repressor of translation initiation by regulating EIF4E activity. In its hypophosphorylated form, EIF4EBP1 competes with EIF4G1/EIF4G3 and strongly binds to EIF4E, leading to translation repression. When hyperphosphorylated, EIF4EBP1 dissociates from EIF4E, allowing interaction between EIF4G1/EIF4G3 and EIF4E, thus initiating translation. This protein mediates the regulation of protein translation by hormones, growth factors, and other stimuli that signal through the MAP kinase and mTORC1 pathways .

What is the specificity of the EIF4EBP1 (Ab-36) antibody?

The EIF4EBP1 (Ab-36) or phospho-T36 antibody specifically detects endogenous levels of 4E-BP1 only when phosphorylated at Threonine 36. The specificity is achieved through affinity purification via sequential chromatography on phospho- and non-phospho-peptide affinity columns. Typically, these antibodies are developed using a synthetic phosphorylated peptide around the T36 position of human eIF4EBP1 (NP_004086.1) as the immunogen .

What applications are suitable for EIF4EBP1 (Ab-36) antibody?

EIF4EBP1 (Ab-36) antibodies have been validated for multiple applications including:

• Western Blot (WB): Typically at dilutions of 1:500-1:2000

• Immunohistochemistry (IHC): Typically at dilutions of 1:50-1:200

• Immunocytochemistry (ICC)

• Immunofluorescence (IF)

• ELISA

The antibody has been tested and confirmed to react with human, mouse, and rat samples .

How should EIF4EBP1 (Ab-36) antibody be stored and handled?

For long-term storage, it is recommended to store the antibody at -20°C for up to one year. For short-term storage and frequent use, store at 4°C for up to one month. It's important to avoid repeated freeze-thaw cycles to maintain antibody efficacy. Most commercially available preparations come in liquid form, often in PBS with 0.02% sodium azide, 50% glycerol, pH 7.2 .

How does phosphorylation status of EIF4EBP1 at different sites affect antibody selection for specific research questions?

EIF4EBP1 is phosphorylated at multiple sites including T36, T37, T46, S65, and T70, each representing different stages of activation and potentially different biological consequences. When designing experiments:

• For investigating initial mTOR activation: Target T36/T37 phosphorylation

• For studying hierarchical phosphorylation patterns: Use antibodies that can distinguish between T36 vs. T37/T46 phosphorylation

• For complete inactivation of EIF4EBP1: Target S65 and T70 phosphorylation

Researchers should carefully select antibodies based on whether they need to track initial, intermediate, or final phosphorylation events in the EIF4EBP1 regulatory cascade .

What are the technical considerations when using phospho-specific T36 EIF4EBP1 antibodies in Western blot analyses?

When using phospho-specific T36 EIF4EBP1 antibodies in Western blot:

• Protein extraction: Use phosphatase inhibitors to preserve phosphorylation status

• Loading controls: Include both phospho-independent EIF4EBP1 antibody and a site-specific phospho-EIF4EBP1 antibody to determine relative phosphorylation levels

• Band analysis: EIF4EBP1 runs at approximately 13 kDa, but phosphorylation causes mobility shifts that result in multiple bands (α, β, γ forms)

• Positive controls: Include extracts from cells treated with EGF (200 ng/ml, 30min) as demonstrated in validation studies

How can EIF4EBP1 (Ab-36) antibody be validated for phosphorylation specificity?

Rigorous validation of phospho-specificity includes:

• Phosphatase treatment: Samples can be treated with λ phosphatase to remove phosphorylation and confirm antibody specificity

• Peptide competition assays: Pre-incubating the antibody with immunizing peptide should abolish signal, as demonstrated in immunohistochemical analyses

• Phospho-mutant controls: Using cells expressing T36A mutants of EIF4EBP1

• Pathway manipulation: Comparing serum-starved cells with those treated with 20% FBS, which activates the mTOR pathway and increases phosphorylation

What is the relationship between EIF4EBP1 phosphorylation at T36 and other phosphorylation sites in the context of mTOR signaling?

Phosphorylation of EIF4EBP1 occurs in a hierarchical manner:

• Initial phosphorylation at T36/T37/T46 (priming sites) is mediated by mTORC1

• This priming phosphorylation facilitates subsequent phosphorylation at S65 and T70

• Complete phosphorylation at all sites is required for full dissociation from eIF4E

Studies have shown that phosphorylation of T36 is often concurrent with T37/T46 phosphorylation, making it important to consider cross-reactivity when interpreting experimental results. This hierarchical phosphorylation pattern makes T36 phosphorylation an early indicator of mTORC1 activity .

What are the recommended protocols for immunohistochemistry using EIF4EBP1 (Ab-36) antibody?

For optimal immunohistochemistry results with EIF4EBP1 (Ab-36) antibody:

• Tissue preparation: Use deparaffinized tissue sections pretreated with citrate buffer at 98°C for 20 min

• Blocking: Block with 2% horse serum, followed by avidin/biotin blocking solutions for 10 min each

• Primary antibody incubation: Apply antibody at 1:50-1:200 dilution for 2 hours at 37°C

• Detection: Use an appropriate detection system (e.g., alkaline phosphatase/RED)

• Counterstaining: Counterstain with hematoxylin solution

• Scoring: Evaluate immunoreactivity using a standardized scoring system such as the Immune Reactive Score (IRS), ranging from 0-12

How can EIF4EBP1 (Ab-36) antibody be used in combination with other antibodies to study the mTOR pathway comprehensively?

A comprehensive analysis of the mTOR pathway requires combining EIF4EBP1 (Ab-36) with:

• Total EIF4EBP1 antibody: To determine the ratio of phosphorylated to total protein

• Phospho-S6K and phospho-rpS6 antibodies: To assess parallel mTORC1 outputs

• Phospho-AKT antibodies: To evaluate upstream pathway activation

• eIF4E antibodies: To study the translation initiation complex formation

Using these antibodies in parallel provides a more complete picture of mTOR pathway activity and avoids misinterpretation due to feedback mechanisms or pathway crosstalk .

What are the best practices for quantifying EIF4EBP1 phosphorylation levels in Western blot and immunohistochemistry?

For accurate quantification:

Western Blot:

• Always include both phospho-specific and total EIF4EBP1 antibodies

• Normalize phospho-EIF4EBP1 signal to total EIF4EBP1 rather than housekeeping proteins

• Account for all bands (α, β, γ forms) when measuring total phosphorylation

• Use appropriate positive and negative controls (serum-starved vs. FBS-treated cells)

Immunohistochemistry:

• Implement standardized scoring systems like the IRS (0-12) based on:

  • Percentage of positive cells (grade 0-4): 0=0-19%, 1=20-39%, 2=40-59%, 3=60-79%, 4=80-100%

  • Staining intensity (grade 0-3): 0=none, 1=low, 2=moderate, 3=strong

  • Final IRS = percentage score × intensity score

• Define threshold values for "high" vs "low" expression (e.g., IRS 0-6 = "low", IRS 7-12 = "high")

How does EIF4EBP1 expression and phosphorylation status correlate with cancer prognosis?

Research indicates significant correlations between EIF4EBP1 expression and cancer outcomes:

How can EIF4EBP1 (Ab-36) antibody be used to evaluate mTOR inhibitor efficacy in cancer research?

EIF4EBP1 (Ab-36) antibody serves as a valuable tool for evaluating mTOR inhibitor efficacy by:

• Providing direct evidence of target engagement: Reduction in T36 phosphorylation indicates successful mTOR inhibition

• Enabling time-course analyses: Monitoring duration of phosphorylation suppression after inhibitor administration

• Allowing dose-response studies: Quantifying phosphorylation reduction at different inhibitor concentrations

• Identifying resistance mechanisms: Persistent phosphorylation despite treatment indicates pathway reactivation

This approach helps researchers differentiate between complete and partial mTOR inhibition, which is critical as partial inhibition may be insufficient to block translation of certain oncogenic mRNAs .

What is the relationship between MYCN and EIF4EBP1 in neuroblastoma, and how can antibodies help study this interaction?

Recent research has revealed that:

• EIF4EBP1 is transcriptionally upregulated by MYCN in neuroblastoma cells

• MYCN directly binds to the EIF4EBP1 promoter at three distinct E-box sites

• High EIF4EBP1 expression correlates with MYCN amplification and is associated with poor prognosis in neuroblastoma

Studying this relationship requires:

• Using EIF4EBP1 antibodies together with MYCN antibodies in co-immunoprecipitation studies

• Combining phospho-EIF4EBP1 (T36) antibodies with total EIF4EBP1 antibodies to assess how MYCN affects both expression and phosphorylation status

• Performing ChIP assays with MYCN antibodies to confirm binding to the EIF4EBP1 promoter region

How does EIF4EBP1 stability relate to eIF4E levels, and what methodological approaches can investigate this relationship?

Research has shown that hypophosphorylated 4E-BP1 is highly unstable when eIF4E amounts are reduced. This dynamic relationship can be investigated using:

• Co-immunoprecipitation with eIF4E and EIF4EBP1 antibodies to study direct interactions

• RNA interference approaches targeting eIF4E followed by assessment of EIF4EBP1 protein levels

• Rescue experiments expressing eIF4E-resistant variants (e.g., HA-tagged mouse eIF4E resistant to human eIF4E shRNA)

• Pulse-chase experiments to measure EIF4EBP1 protein stability under different eIF4E levels

Studies have demonstrated that expression of HA-tagged mouse eIF4E mitigates the decrease in 4E-BP1 and completely averts the elimination of hypophosphorylated 4E-BP1 when human eIF4E is knocked down .