Phospho-APLP2 (Tyr755) Antibody

What is the Phospho-APLP2 (Tyr755) Antibody and what epitope does it recognize?

The Phospho-APLP2 (Tyr755) Antibody is a rabbit polyclonal antibody that specifically detects endogenous levels of APLP2 protein only when phosphorylated at tyrosine 755. This antibody recognizes an epitope spanning amino acids 714-763 of human APLP2, centered around the phosphorylated Tyr755 residue . The immunogen used for antibody generation is typically a synthesized phosphopeptide derived from human APLP2 with the sequence surrounding the phosphorylation site of Tyr755 (P-T-Y(p)-K-Y) .

What are the recommended applications and dilutions for Phospho-APLP2 (Tyr755) Antibody?

The antibody has been validated for multiple research applications with the following recommended dilutions:

• Immunohistochemistry (IHC): 1:100-1:300

• Immunofluorescence (IF): 1:50-200

• ELISA: 1:20000

Most suppliers indicate these applications have been specifically validated, while other potential applications may require additional optimization . When working with new tissue types or experimental conditions, it is advisable to perform preliminary dilution series tests to determine optimal antibody concentration for your specific application.

What species reactivity has been confirmed for Phospho-APLP2 (Tyr755) Antibody?

The Phospho-APLP2 (Tyr755) Antibody has been validated to react with APLP2 from human, mouse, and rat samples . The high degree of conservation in the amino acid sequence surrounding the Tyr755 site across these species enables cross-reactivity. When working with other species, additional validation would be required to confirm reactivity due to potential sequence variations in the epitope region.

How should I validate the specificity of Phospho-APLP2 (Tyr755) Antibody in my experimental system?

To validate antibody specificity for phospho-APLP2 (Tyr755), employ these methodological approaches:

• Peptide competition assay: Pre-incubate the antibody with the phosphorylated peptide used as the immunogen before application to your samples. This should block specific binding and eliminate signal. Several manufacturers provide examples of this validation technique in brain tissues .

• Phosphatase treatment controls: Treat half of your sample with lambda phosphatase to remove phosphate groups before antibody incubation. The signal should disappear in the phosphatase-treated sample.

• Knockout/knockdown validation: Use APLP2 knockout tissues or APLP2 siRNA-treated cells as negative controls to confirm signal specificity.

• Positive control tissues: Human brain tissue is recommended as a positive control for IHC applications .

What are the optimal experimental conditions for preserving APLP2 phosphorylation at Tyr755 during sample preparation?

To maintain the phosphorylation status at Tyr755 of APLP2 during sample preparation:

• Rapid sample processing: Minimize the time between tissue collection and fixation/lysis to prevent phosphatase activity.

• Phosphatase inhibitors: Include a comprehensive phosphatase inhibitor cocktail in all lysis and wash buffers (e.g., sodium orthovanadate, sodium fluoride, β-glycerophosphate).

• Cold temperature: Perform all processing steps at 4°C to minimize enzymatic dephosphorylation.

• Fixation conditions: For IHC applications, 10% neutral buffered formalin is typically suitable, but avoid overfixation which can mask phospho-epitopes.

• Antigen retrieval: For paraffin-embedded tissues, heat-induced epitope retrieval in citrate buffer (pH 6.0) is recommended to expose the phosphorylated epitope .

How can I design experiments to study the dynamic phosphorylation of APLP2 at Tyr755?

To study dynamic phosphorylation of APLP2 at Tyr755:

• Time-course experiments: Expose cells to stimuli known to affect tyrosine phosphorylation (e.g., stress conditions as indicated in ) and collect samples at multiple time points.

• Kinase inhibitor studies: Pre-treat cells with specific kinase inhibitors to identify the kinase(s) responsible for Tyr755 phosphorylation.

• Quantitative analysis: Implement Western blot with phospho-specific and total APLP2 antibodies in parallel to calculate the phosphorylation ratio.

• Site-directed mutagenesis: Create Y755A or Y755F APLP2 mutants to serve as negative controls and to study the functional consequences of phosphorylation at this site, similar to the approach used in the research showing that mutation of this tyrosine severely impaired APLP2 internalization .

• Stress-induced phosphorylation: JNK has been implicated in the phosphorylation of APP family proteins under cellular stress conditions, which may extend to Tyr755 of APLP2 .

What is the functional significance of APLP2 phosphorylation at Tyr755?

Phosphorylation of APLP2 at Tyr755 plays critical roles in multiple cellular processes:

• Endocytosis regulation: Tyr755 is located within overlapping consensus motifs (NPXY and YXXØ) for binding to the adaptor protein-2 (AP-2) complex. Phosphorylation at this site is essential for APLP2 internalization via clathrin-dependent endocytosis .

• MHC Class I trafficking: Phosphorylation at Tyr755 is necessary for APLP2 to facilitate MHC Class I (specifically Kd) endocytosis. Mutation of Tyr755 severely impaired APLP2 internalization and its ability to promote Kd endocytosis. This suggests a molecular mechanism by which APLP2 regulates immune surveillance .

• Protein-protein interactions: The phosphorylation status of Tyr755 may act as a molecular switch for protein-protein interactions, similar to how phosphorylation of APP family proteins modulates their binding partners .

• Subcellular localization: Phosphorylation at this site affects APLP2 trafficking between cell membrane and endosomal compartments, ultimately influencing its biological functions .

How does the APLP2 Tyr755 phosphorylation site compare to similar motifs in other APP family members?

The Tyr755 phosphorylation site in APLP2 shares significant structural and functional similarities with phosphorylation sites in other APP family members:

• Sequence conservation: The APLP2 Tyr755 site is part of a conserved NPXY/YXXØ motif present in all APP family members, including APP and APLP1, suggesting evolutionary conservation of this regulatory mechanism.

• Functional parallels: Similar to APLP2 Tyr755, phosphorylation of APP at Thr668 (APP695 isoform numbering) serves as a molecular switch for protein-protein interactions. Both phosphorylation events are implicated in neural functions and/or Alzheimer's disease pathogenesis .

• Stress-response regulation: Both APP (at Thr668) and APLP2 (at Thr736, in the APLP2-763 isoform) can be phosphorylated by JNK in response to cellular stress. While this specific paper mentions Thr736 rather than Tyr755, it demonstrates that APLP2 phosphorylation is dynamically regulated under stress conditions .

• Endocytic trafficking: The tyrosine-based motifs in both APP and APLP2 mediate interaction with adaptor proteins for endocytosis, suggesting a common mechanism for internalization among APP family members.

What is known about the kinases responsible for phosphorylating APLP2 at Tyr755?

The specific kinases that phosphorylate APLP2 at Tyr755 are not explicitly identified in the provided search results, but several lines of evidence suggest potential kinases:

• Tyrosine kinases: Given that Tyr755 is a tyrosine phosphorylation site, receptor and non-receptor tyrosine kinases are likely candidates. The search results don't specify which tyrosine kinase is responsible.

• Stress-activated kinases: JNK has been shown to phosphorylate APLP2, though the specific research mentioned phosphorylation at Thr736 rather than Tyr755 . This suggests stress-activated pathways may regulate multiple phosphorylation sites on APLP2.

• Signaling pathway context: Since APLP2 interacts with MHC class I molecules and affects their trafficking, kinases involved in immune signaling pathways might be responsible for this phosphorylation event.

• Research approach: To identify the specific kinase(s), researchers would typically use a combination of:

  • In vitro kinase assays with recombinant kinases

  • Kinase inhibitor screens

  • Kinase overexpression and knockdown studies

  • Phosphoproteomic analysis following various cellular stimuli

What is the role of APLP2 and its phosphorylation at Tyr755 in Alzheimer's disease pathogenesis?

While the specific role of Tyr755 phosphorylation is not directly addressed in the search results, APLP2 has several connections to Alzheimer's disease:

• APP family member: APLP2 is a member of the amyloid precursor protein (APP) family, and APP is central to Alzheimer's disease pathology through its processing to form amyloid-beta (Aβ) peptides .

• Functional complementation: APLP2 and APP show synergistic functions in neuromuscular transmission, spatial learning, and synaptic plasticity, suggesting APLP2 may contribute to neurological functions disrupted in Alzheimer's disease .

• Phosphorylation regulation: Phosphorylation of APP family proteins, including APLP2, acts as a molecular switch for protein-protein interactions and is implicated in Alzheimer's disease pathogenesis .

• Research direction: Investigating whether Tyr755 phosphorylation affects APLP2 processing, localization, or interactions with other proteins could provide insights into its potential role in Alzheimer's disease. Experimental approaches might include comparing phosphorylation levels in normal versus Alzheimer's disease brain tissues, and studying the effects of Tyr755 phosphorylation on APLP2 proteolytic processing.

How is APLP2 implicated in cancer progression, and what role might Tyr755 phosphorylation play?

Recent research suggests important roles for APLP2 in cancer:

• Cutaneous squamous cell carcinoma (CSCC): High APLP2 expression was detected in 51.8% of CSCC tissue samples and was significantly associated with subcutaneous fat invasion and poor prognosis .

• Cellular mechanisms: APLP2 knockdown significantly reduced proliferation and invasion by CSCC cells both in vitro and in vivo, suggesting a pro-oncogenic function .

• Immune evasion: APLP2 expression was significantly associated with membrane MHC-I expression in CSCC patients, and APLP2 knockdown increased membrane MHC-I expression in CSCC cells, suggesting a potential role in cancer immune evasion .

• Potential role of Tyr755 phosphorylation: Although not explicitly studied in cancer contexts, the role of Tyr755 phosphorylation in regulating APLP2 endocytosis and MHC class I trafficking suggests it might influence cancer immune evasion. Phosphorylation at this site could potentially affect how cancer cells regulate surface MHC-I levels and thus their visibility to the immune system.

• Research opportunities: Investigating Tyr755 phosphorylation status in cancer tissues compared to normal tissues, and studying how this phosphorylation affects cancer cell properties like proliferation, invasion, and immune evasion could provide valuable insights.

How can phospho-specific antibodies against APLP2 Tyr755 be utilized in disease-relevant research?

Phospho-specific antibodies against APLP2 Tyr755 offer several methodological approaches for disease-relevant research:

• Biomarker development: These antibodies can be used to assess phosphorylation levels in patient samples to determine if altered APLP2 phosphorylation correlates with disease progression or treatment response.

• Pathway analysis: By monitoring Tyr755 phosphorylation after treatment with various inhibitors or stimuli, researchers can map the signaling pathways that regulate APLP2 in disease contexts.

• Histopathological studies: As demonstrated in cutaneous squamous cell carcinoma research, IHC with APLP2 antibodies can reveal expression patterns in patient tissues and correlate them with clinical outcomes . Phospho-specific antibodies could provide additional prognostic information.

• Drug screening: These antibodies can be used to screen for compounds that modulate APLP2 phosphorylation as potential therapeutic agents.

• Mechanistic studies: In both Alzheimer's disease and cancer research, these antibodies enable investigation of how phosphorylation affects APLP2 interactions, particularly with MHC class I molecules, which may influence disease progression .

• Sample type compatibility: The antibody has been validated for use with paraffin-embedded tissues (IHC-p) , making it compatible with archival clinical specimens for retrospective studies.

What are the common technical challenges when working with phospho-specific antibodies like Phospho-APLP2 (Tyr755) Antibody?

Working with phospho-specific antibodies presents several technical challenges:

• Phosphorylation preservation: Phosphate groups can be rapidly lost due to endogenous phosphatase activity. Always use fresh tissue samples and include phosphatase inhibitors (sodium orthovanadate, sodium fluoride, β-glycerophosphate) in all buffers.

• Epitope masking: Formalin fixation can cross-link proteins and mask phospho-epitopes. Optimize antigen retrieval methods (typically heat-induced epitope retrieval with citrate buffer, pH 6.0) for each tissue type.

• Signal specificity: Phospho-antibodies may sometimes recognize similar phosphorylated motifs in other proteins. Always include appropriate controls:

  • Peptide competition assays with both phosphorylated and non-phosphorylated peptides

  • Phosphatase-treated samples as negative controls

  • Western blot verification of molecular weight

• Signal intensity: Phosphorylation is often a transient, substoichiometric modification, resulting in weak signals. Consider signal amplification methods like tyramide signal amplification for IHC/IF applications.

• Storage stability: Phospho-antibodies may lose specificity over time. Store at -20°C in small aliquots to avoid repeated freeze-thaw cycles, as recommended by manufacturers .

What are the recommended storage and handling conditions to maintain antibody performance?

To maintain optimal performance of the Phospho-APLP2 (Tyr755) Antibody:

• Storage temperature: Store at -20°C for long-term storage (up to 1 year from the date of receipt) .

• Formulation: The antibody is typically provided in PBS containing 50% glycerol, 0.5% BSA, and 0.02% sodium azide , which helps maintain stability.

• Aliquoting: Upon receipt, divide the antibody into small working aliquots to avoid repeated freeze-thaw cycles which can degrade antibody performance.

• Short-term storage: For frequent use over a short period (up to one month), store at 4°C .

• Handling: When removing from storage, allow the antibody to equilibrate to room temperature before opening the vial to prevent condensation that could dilute or contaminate the antibody.

• Working dilutions: Prepare working dilutions immediately before use and discard any unused diluted antibody rather than storing diluted solutions for extended periods.

• Transportation: During transportation, ensure the antibody remains frozen or at least below 4°C to maintain its activity and specificity.

What controls should be included when designing experiments with Phospho-APLP2 (Tyr755) Antibody?

A robust experimental design with Phospho-APLP2 (Tyr755) Antibody should include these controls:

• Positive tissue control: Human brain tissue is recommended as a positive control for IHC applications , as it has confirmed expression of phosphorylated APLP2.

• Peptide competition controls:

  • Phosphorylated peptide: Pre-incubation with the phosphopeptide immunogen should abolish specific staining

  • Non-phosphorylated peptide: Pre-incubation with the corresponding non-phosphorylated peptide should not affect specific staining

• Phosphatase treatment control: Treating samples with lambda phosphatase before antibody incubation should eliminate specific phospho-signal.

• Genetic controls:

  • APLP2 knockdown/knockout samples as negative controls

  • APLP2 Y755A or Y755F mutant transfected cells as negative controls for phosphorylation

  • Wild-type APLP2 overexpression as a positive control

• Pathway modulation controls:

  • Treatment with tyrosine kinase inhibitors should reduce signal

  • Treatment with phosphatase inhibitors may enhance signal

• Secondary antibody control: Incubation with secondary antibody alone to check for non-specific binding

• Cross-reactivity assessment: If studying multiple APP family members, include controls for APP and APLP1 to ensure specificity for APLP2.