Phospho-HTRA2 (S142) Antibody

What is the Phospho-HTRA2 (S142) Antibody and what does it detect?

The Phospho-HTRA2 (S142) Antibody is a polyclonal antibody that specifically recognizes HtrA2 protein only when phosphorylated at the serine 142 residue. This antibody does not bind to non-phosphorylated HtrA2 or HtrA2 phosphorylated at other sites, providing a valuable tool for studying the phosphorylation state of this specific residue . The antibody is typically generated using synthesized phospho-peptides derived from human HtrA2 around the S142 phosphorylation site and is available in affinity-purified forms from rabbit antiserum .

What is the biological significance of HtrA2 phosphorylation at S142?

HtrA2 is phosphorylated at S142 upon activation of the p38 signaling pathway, and this phosphorylation is dependent on PINK1, a mitochondrial putative kinase associated with Parkinson's disease . Functionally, phosphorylation at S142 increases HtrA2 protease activity, which enhances its protective effect in cells . This post-translational modification may represent a regulatory mechanism for controlling HtrA2's function in mitochondrial quality control and cellular stress responses.

What are the recommended applications for Phospho-HTRA2 (S142) Antibody?

Based on validated research applications, the Phospho-HTRA2 (S142) Antibody can be used in:

• Immunohistochemistry (IHC): Typically at dilutions of 1:100-1:300

• Enzyme-Linked Immunosorbent Assay (ELISA): Typically at dilutions around 1:40000

• Immunofluorescence (IF): Typically at dilutions of 1:50-1:200

While the antibody has been validated for these applications across human, mouse, and rat samples, researchers should determine optimal working dilutions experimentally for their specific research conditions .

How should the Phospho-HTRA2 (S142) Antibody be stored and handled?

For optimal performance and longevity, the Phospho-HTRA2 (S142) Antibody should be:

• Stored at -20°C or -80°C

• Aliquoted to avoid repeated freeze-thaw cycles

• Maintained in its storage buffer, typically PBS containing 50% glycerol, 0.5% BSA, and 0.02% sodium azide

Long-term stability is typically assured for at least one year when properly stored at -20°C in the recommended buffer conditions .

How can I validate the specificity of the Phospho-HTRA2 (S142) Antibody in my experimental system?

To validate antibody specificity, employ the following approaches:

• Phosphatase treatment controls: Treat half of your sample with lambda phosphatase before antibody incubation. Disappearance of signal confirms phospho-specificity.

• Phospho-mutant controls: Express wild-type HtrA2 and a S142A mutant (non-phosphorylatable) in cells, then perform western blotting or immunostaining. The antibody should only detect wild-type HtrA2 following stimulation of phosphorylation pathways.

• Peptide competition assay: Pre-incubate the antibody with the phospho-peptide immunogen to block specific binding sites before application to samples.

• Phosphorylation induction: Stimulate the p38 pathway (e.g., using ΔMEKK3 activation with 4OH-Tx in appropriate cell lines) to increase S142 phosphorylation, which should increase antibody signal .

What methods can be used to induce HtrA2 phosphorylation at S142 in experimental systems?

Based on established research protocols, HtrA2 phosphorylation at S142 can be induced through:

• Activation of the p38 signaling pathway using ΔMEKK3-ER cells stimulated with 4-hydroxytamoxifen (4OH-Tx)

• Cellular stress conditions that activate p38 MAPK pathways

• Overexpression of PINK1, which has been demonstrated to promote HtrA2 phosphorylation at S142

The effectiveness of phosphorylation induction should be verified using the Phospho-HTRA2 (S142) Antibody in western blotting or immunostaining applications.

What are the recommended protocols for antigen retrieval when using Phospho-HTRA2 (S142) Antibody in immunohistochemistry?

For optimal immunohistochemical detection of phosphorylated HtrA2:

• Use Tris-EDTA buffer (pH 9.0) for antigen retrieval

• Apply the primary antibody at 1:100-1:300 dilution and incubate overnight at 4°C

• Use appropriate secondary antibody at approximately 1:200 dilution with incubation at room temperature for 30 minutes

This protocol has been validated to minimize background while maximizing specific detection of phosphorylated HtrA2 in tissue sections.

How is Phospho-HTRA2 (S142) relevant to Parkinson's disease research?

HtrA2 has been implicated in Parkinson's disease (PD) through several mechanisms:

• Genetic associations: Mutations in HtrA2 (G399S and A141S polymorphism) have been identified in PD patients, with the G399S mutation positioned one amino acid downstream from the S400 phosphorylation site .

• PINK1 pathway integration: HtrA2 phosphorylation at S142 is dependent on PINK1, a well-established PD-associated gene. This suggests HtrA2 functions within the same cellular pathway as other PD-linked proteins .

• Protective functions: Phosphorylation at S142 increases HtrA2 protease activity, enhancing its protective effect. Disruption of this phosphorylation could contribute to mitochondrial dysfunction observed in PD .

The Phospho-HTRA2 (S142) Antibody enables researchers to monitor this specific post-translational modification in PD models and patient samples, potentially revealing disease-specific alterations in HtrA2 regulation.

What evidence connects HtrA2 to amyloid beta aggregation in Alzheimer's disease models?

Research has demonstrated that HtrA2 can delay aggregation of the amyloid beta (Aβ) peptide, implicated in Alzheimer's disease pathology:

• HtrA2 significantly delays Aβ (1-42) peptide aggregation into fibers as visualized by electron microscopy .

• The delay in Aβ aggregation appears comparable to that observed with human serum albumin, a known Aβ-binding protein .

• Extended incubation (72 hours) of HtrA2 with Aβ (1-42) results in partial degradation of the peptide, suggesting HtrA2's protease activity contributes to its anti-aggregation effects .

• HtrA2 may function both as a protease that degrades Aβ and as a chaperone that maintains Aβ in a monomeric state, delaying its aggregation .

The Phospho-HTRA2 (S142) Antibody could be valuable for investigating whether S142 phosphorylation affects HtrA2's capacity to influence Aβ aggregation, potentially linking HtrA2 regulation to Alzheimer's disease mechanisms.

How does Cdk5-mediated phosphorylation of HtrA2 at S400 interact with S142 phosphorylation?

Research has revealed a complex interplay between different phosphorylation sites on HtrA2:

• While p38 pathway activation leads to S142 phosphorylation, Cdk5 preferentially phosphorylates HtrA2 at S400 both in vitro and in situ .

• Experimental evidence indicates that Cdk5-mediated phosphorylation of HtrA2 at S400 requires a functional serine at position 142, suggesting interdependence between these phosphorylation sites .

• The S142/400A double phosphomutant shows the least ability to be phosphorylated, highlighting the potential regulatory cross-talk between these sites .

This interplay suggests a sophisticated regulatory mechanism wherein different kinases (p38-dependent kinases and Cdk5) may coordinate HtrA2 function through site-specific phosphorylation events. Researchers investigating S142 phosphorylation should consider the potential influence of S400 phosphorylation status on their experimental outcomes.

What are the methodological considerations for distinguishing between HtrA2's protease and chaperone functions when studying its phosphorylation state?

To differentiate between HtrA2's dual functions, researchers should implement these methodological approaches:

• Use of protease-inactive mutants: The S306A mutation renders HtrA2 proteolytically inactive while preserving potential chaperone function. Compare wild-type phosphorylated HtrA2 with phosphorylated S306A mutant to isolate chaperone activity .

• Domain-specific mutations: The HtrA2 ΔPDZ S306A mutant (residues 133-342) can be used to assess the role of the PDZ domain in potential chaperone functions independent of protease activity .

• Protein aggregation assays: Monitor aggregation of model substrates like citrate synthase (CS) or Aβ peptides using light scattering or electron microscopy in the presence of wild-type or mutant HtrA2 proteins .

• Combined approaches: Use immunoprecipitation with Phospho-HTRA2 (S142) Antibody followed by protease activity assays to correlate phosphorylation status with specific functions.

A sample experimental design comparing aggregation prevention capabilities is shown in the table below:

How can phosphorylation status of HtrA2 be integrated into studies of mitochondrial dynamics and quality control?

To investigate the relationship between HtrA2 phosphorylation and mitochondrial biology:

• Co-localization studies: Use the Phospho-HTRA2 (S142) Antibody in combination with mitochondrial markers to assess whether phosphorylated HtrA2 shows distinct subcellular localization compared to total HtrA2.

• Mitochondrial fractionation: Separate mitochondrial compartments (outer membrane, intermembrane space, inner membrane, matrix) and quantify the distribution of phosphorylated versus total HtrA2.

• Stress response dynamics: Monitor changes in HtrA2 phosphorylation levels following mitochondrial stress (e.g., CCCP treatment, rotenone exposure) using the Phospho-HTRA2 (S142) Antibody.

• Integration with mitophagy pathways: Assess the relationship between HtrA2 phosphorylation status and PINK1/Parkin-dependent mitophagy using dual immunostaining approaches.

This integrated approach can reveal whether S142 phosphorylation serves as a molecular switch that alters HtrA2's role in mitochondrial homeostasis under different cellular conditions.

What are common issues when using Phospho-HTRA2 (S142) Antibody and how can they be resolved?

How can I quantitatively assess HtrA2 phosphorylation levels in complex biological samples?

For quantitative assessment of HtrA2 phosphorylation:

• Normalization strategy: Always normalize phospho-HtrA2 signal to total HtrA2 levels rather than housekeeping proteins to account for variations in total HtrA2 expression.

• Multiple analytical techniques: Combine western blotting, ELISA, and immunohistochemistry quantification for robust measurements across different sample types.

• Standard curve approach: Generate a standard curve using recombinant phosphorylated and non-phosphorylated HtrA2 at known concentrations to establish absolute quantification parameters.

• Phospho-state specific enrichment: Use phospho-protein enrichment techniques prior to analysis to enhance detection sensitivity in samples with low phosphorylation levels.

• Mass spectrometry validation: For highest accuracy, complement antibody-based detection with phospho-peptide mapping using mass spectrometry to confirm site-specific phosphorylation and determine stoichiometry.

This multifaceted approach provides more reliable quantification than any single method alone, especially when studying subtle changes in phosphorylation status across experimental conditions.

What emerging research areas might benefit from studying HtrA2 phosphorylation at S142?

Several promising research directions could leverage the Phospho-HTRA2 (S142) Antibody:

• Biomarker development: Investigating whether phospho-HtrA2 levels in cerebrospinal fluid or exosomes correlate with neurodegenerative disease progression.

• Therapeutic modulation: Screening compounds that selectively modulate HtrA2 phosphorylation as potential neuroprotective agents.

• Stress response pathways: Mapping how diverse cellular stressors affect HtrA2 phosphorylation status and subsequent mitochondrial function.

• Protein quality control networks: Exploring how HtrA2 phosphorylation interfaces with other mitochondrial quality control systems like the PINK1/Parkin pathway.

• Age-related mitochondrial dysfunction: Examining whether altered HtrA2 phosphorylation contributes to mitochondrial decline in aging tissues.

These research directions may reveal new insights into fundamental cellular processes and disease mechanisms, potentially identifying novel therapeutic targets.

How might phospho-proteomic approaches complement antibody-based detection of HtrA2 phosphorylation?

Integration of phospho-proteomics with antibody-based approaches offers several advantages:

• Multi-site phosphorylation analysis: Mass spectrometry can simultaneously detect all phosphorylation sites on HtrA2, revealing potential crosstalk between S142 and other sites like S400.

• Pathway mapping: Phospho-proteomics can identify other proteins phosphorylated concurrent with HtrA2, helping to map the broader signaling network.

• Quantitative stoichiometry: Mass spectrometry provides absolute quantification of phosphorylation stoichiometry, complementing the relative measurements from antibody-based approaches.

• Novel site discovery: Unbiased phospho-proteomic screening might reveal previously uncharacterized phosphorylation sites on HtrA2 with functional significance.

• Validation of antibody specificity: Phospho-proteomic methods can serve as an orthogonal validation approach for confirming antibody specificity in complex samples.