ppp1r11 Antibody

What is PPP1R11 and why is it important in biological research?

PPP1R11 functions as both a protein phosphatase inhibitor and an E3 ubiquitin ligase, playing crucial roles in cell cycle regulation and innate immunity. It primarily inhibits protein phosphatase 1 (PP1), a key enzyme involved in cell division and growth . More recent research has identified its function as a RING finger E3 ligase that ubiquitinates Toll-like receptor 2 (TLR2) at lysine-754, leading to TLR2 degradation and regulation of inflammatory responses . This dual functionality makes PPP1R11 a significant target for studying cellular signaling pathways, particularly in immune response and cancer research, as dysregulation of PPP1R11 has been implicated in various diseases including cancer development .

What are the primary applications for PPP1R11 antibodies in research?

PPP1R11 antibodies are valuable tools for multiple research applications including protein detection via Western blotting, immunohistochemistry (IHC), and enzyme-linked immunosorbent assay (ELISA) . These antibodies enable researchers to investigate PPP1R11 expression patterns in various cell types and tissues, examine protein-protein interactions through co-immunoprecipitation experiments, and study the role of PPP1R11 in specific signaling pathways. In infection and immunity research, PPP1R11 antibodies help elucidate mechanisms of TLR2 regulation and inflammatory response modulation . Additionally, they're used in T cell research to understand how PPP1R11 influences cytokine expression and susceptibility to regulatory T cell-mediated suppression .

What sample types can be analyzed using PPP1R11 antibodies?

PPP1R11 antibodies such as PACO31756 demonstrate high reactivity with human samples . They can be used to detect endogenous PPP1R11 in cell lysates from various human cell lines, tissue sections for immunohistochemistry analysis, and patient-derived samples. For instance, these antibodies have been successfully employed in analyzing white blood cell (WBC) pellets from patients with Staphylococcus aureus infections to investigate correlations between PPP1R11 and TLR2 levels . When working with mouse models, researchers should select antibodies specifically validated for cross-reactivity with murine PPP1R11, as species-specific variations in epitope recognition can affect experimental outcomes.

What are the recommended protocols for immunohistochemistry with PPP1R11 antibodies?

For optimal immunohistochemistry results with PPP1R11 antibodies:

• Deparaffinize and rehydrate tissue sections if using paraffin-embedded samples

• Perform antigen retrieval using citrate buffer (pH 6.0) with heat-induced epitope retrieval

• Block endogenous peroxidase activity with 3% hydrogen peroxide for 10 minutes

• Apply protein blocking solution for 30 minutes at room temperature

• Incubate with primary PPP1R11 antibody at dilutions between 1:20-1:200 (optimal dilution may require titration)

• Incubate with appropriate secondary antibody and detection system

• Counterstain, dehydrate, and mount

This protocol has been validated for human placenta tissue using the PACO31756 antibody at a dilution of 1:100 . Always include appropriate positive and negative controls to validate staining specificity.

How does PPP1R11 regulate TLR2 signaling and what experimental approaches best demonstrate this relationship?

PPP1R11 negatively regulates TLR2 signaling through direct ubiquitination of TLR2 at lysine-754, leading to its proteasomal degradation . This mechanism can be investigated using several complementary approaches:

• In vitro ubiquitination assays: Using purified components including 20 mM HEPES (pH 7.2), 0.6 mM DTT, 2 mM ATP, E1 (1.5 ng/ml), E2 conjugating enzymes (10 ng/ml), ubiquitin (1 mg/ml), ubiquitin aldehyde (1 mM), and in vitro synthesized V5-TLR2 and PPP1R11. Detection of ubiquitinated TLR2 is achieved through V5 immunoblotting .

• Protein half-life studies: Tracking TLR2 protein stability in cells with normal versus altered PPP1R11 levels using cycloheximide chase assays. CRISPR-edited cells with PPP1R11 knockout show stabilized TLR2 half-life compared to control cells .

• Cytokine release assays: Measuring inflammatory cytokine production (IL-6, CXCL1) in response to TLR2 ligand (PAM3CSK4) stimulation in cells with PPP1R11 overexpression or knockdown. PPP1R11 overexpression reduces cytokine release while knockdown increases it .

• In vivo infection models: Using lentiviral gene transfer to manipulate PPP1R11 levels in mouse lungs before Staphylococcus aureus challenge. Monitoring inflammation markers (lavage cytokines, protein concentrations, cell counts) and bacterial clearance provide evidence of PPP1R11's role in regulating the immune response .

These approaches collectively demonstrate that PPP1R11 functions as a negative feedback regulator that prevents excessive inflammatory responses while potentially compromising pathogen clearance.

What is the relationship between PPP1R11 and T cell activation, and how can it be experimentally assessed?

PPP1R11 functions as a negative regulator of T cell activation-induced cytokine expression . Its relationship with T cell activation can be experimentally assessed through:

• siRNA-mediated silencing: Transfecting primary human T cells with PPP1R11-specific siRNA to assess the impact of PPP1R11 depletion on T cell functions.

• Cytokine expression analysis: Measuring IL-2 and IFN-γ gene and protein expression in PPP1R11-silenced versus control T cells following TCR stimulation. PPP1R11 knockdown significantly upregulates expression of IL2, IFNG, and other TCR-stimulation-induced cytokines .

• Regulatory T cell (Treg) suppression assays: Co-culturing PPP1R11-silenced or control T cells with regulatory T cells to assess resistance to Treg-mediated suppression. Loss of PPP1R11 renders T cells resistant to Treg-mediated suppression of cytokine expression .

• Whole-transcriptome sequencing: Performing RNA-seq analysis on PPP1R11-silenced and control T cells to identify global effects on gene expression and signaling pathways. This reveals that PPP1R11 may affect phosphatidylinositol signaling, MAPK-AKT, and NF-κB pathways .

• Phosphatase inhibition studies: Using specific inhibitors of PP1 (the target of PPP1R11) to confirm the mechanism by which PPP1R11 regulates cytokine expression.

These experimental approaches reveal that targeting PPP1R11 may have therapeutic potential for modulating T cell activation status, including altering susceptibility to Treg-mediated suppression and specifically shaping the stimulation-induced T cell cytokine profile.

How can researchers design experiments to resolve contradictory findings regarding PPP1R11 function in different cell types?

Contradictory findings about PPP1R11 function may arise due to cell type-specific effects, experimental conditions, or context-dependent protein interactions. To resolve such discrepancies, researchers should consider a comprehensive experimental design:

• Parallel testing in multiple cell types: Simultaneously investigating PPP1R11 function in different cell types (e.g., epithelial cells, T cells, macrophages) under identical conditions to identify cell type-specific responses.

• Context-dependent activation: Examining PPP1R11 function under different stimulation conditions (e.g., TLR2 ligands, TCR stimulation, inflammatory cytokines) to determine context-specific activities.

• Protein complex identification: Using proteomics approaches such as proximity labeling or co-immunoprecipitation coupled with mass spectrometry to identify cell type-specific PPP1R11 binding partners that might explain differential functions.

• Domain-specific mutations: Creating a panel of PPP1R11 mutants with alterations in specific functional domains to dissect which activities (phosphatase inhibition versus E3 ligase activity) are responsible for observed phenotypes in each cell type.

• In vivo validation: Employing tissue-specific conditional knockout models to validate in vitro findings in physiologically relevant contexts.

For example, while PPP1R11 functions as a negative regulator of inflammatory responses in lung epithelial cells by targeting TLR2 for degradation , it also negatively regulates T cell activation-induced cytokine expression through a potentially different mechanism . These seemingly contradictory roles can be reconciled by understanding the tissue-specific signaling networks and protein interactions that dictate PPP1R11 function in each context.

What are the optimal conditions for Western blot detection of PPP1R11?

For successful Western blot detection of PPP1R11:

Always include appropriate positive controls and consider running a loading control (β-actin, GAPDH) to normalize expression levels between samples. For detecting both endogenous and overexpressed tagged-PPP1R11, be aware of the size shift introduced by epitope tags .

What strategies can improve the specificity of PPP1R11 detection in complex biological samples?

Improving specificity of PPP1R11 detection requires careful optimization and validation:

• Antibody validation: Confirm antibody specificity using PPP1R11 knockdown or knockout samples as negative controls. The absence of signal in these samples confirms specificity.

• Peptide competition assays: Pre-incubate the antibody with a blocking peptide containing the immunogen sequence to confirm specific binding.

• Multiple antibody approach: Use antibodies targeting different epitopes of PPP1R11 to validate findings and reduce the likelihood of cross-reactivity.

• Purification of target protein: For complex samples, consider immunoprecipitation to enrich PPP1R11 before detection.

• Optimized blocking conditions: Test different blocking agents (BSA, milk, commercial blockers) to reduce background and non-specific binding.

• Sample preparation optimization: For tissue samples, optimize protein extraction protocols to ensure complete solubilization while maintaining protein integrity.

• Sequential probing strategy: For co-detection of PPP1R11 with its interaction partners (e.g., TLR2, PP1), use sequential probing with thorough stripping between antibodies to prevent cross-reactivity.

These approaches are particularly important when studying PPP1R11 in primary human samples, where protein abundance may be low and complex matrices can interfere with detection .

How can researchers quantitatively assess PPP1R11-mediated ubiquitination of target proteins?

Quantitative assessment of PPP1R11-mediated ubiquitination requires specialized techniques:

• In vitro ubiquitination assays: Using purified components including E1, E2, PPP1R11 (E3), ubiquitin, and the substrate protein (e.g., TLR2). The reaction products are analyzed by immunoblotting for the substrate or for ubiquitin. This can be quantified by densitometry to compare ubiquitination efficiency between conditions .

• Cellular ubiquitination assays: Co-expressing tagged versions of ubiquitin (HA-Ub), PPP1R11, and the substrate protein, followed by immunoprecipitation under denaturing conditions and detection of ubiquitinated species by Western blot.

• Ubiquitin-remnant profiling: Using antibodies that recognize the di-glycine remnant left on ubiquitinated lysines after trypsin digestion, combined with mass spectrometry to identify and quantify ubiquitination sites.

• Cycloheximide chase assays: Comparing the degradation rate of target proteins in the presence or absence of PPP1R11 to indirectly measure ubiquitination efficiency.

• Ubiquitin chain-specific antibodies: Using antibodies that recognize specific ubiquitin chain linkages (K48, K63) to determine the type of ubiquitination catalyzed by PPP1R11, which provides insight into the fate of the substrate.

For the specific assessment of TLR2 ubiquitination by PPP1R11, researchers have successfully employed in vitro ubiquitination assays using reaction buffers containing 20 mM HEPES (pH 7.2), 0.6 mM DTT, 2 mM ATP, E1, E2 enzymes, ubiquitin, and in vitro synthesized V5-TLR2 and PPP1R11, followed by V5 immunoblotting to detect ubiquitinated TLR2 .

What are the therapeutic implications of targeting PPP1R11 in immune-related disorders?

Emerging research suggests that modulating PPP1R11 levels or activity could have therapeutic potential in several immune-related disorders:

• Bacterial infections: PPP1R11 inhibition could enhance pathogen clearance by increasing TLR2 levels and inflammatory responses. In mouse models of Staphylococcus aureus infection, PPP1R11 knockdown significantly increased inflammatory cytokine production and improved bacterial clearance in lavage fluids, lung, and blood . This approach might benefit patients with severe gram-positive bacterial infections, particularly those at risk for acute respiratory distress syndrome (ARDS).

• T cell-mediated autoimmunity: Silencing PPP1R11 renders T cells resistant to regulatory T cell (Treg)-mediated suppression . This finding suggests that enhancing PPP1R11 expression or activity might help restore proper Treg function in autoimmune conditions characterized by defective immunosuppression.

• Cancer immunotherapy: Modulating PPP1R11 could potentially enhance or inhibit T cell responses in tumor microenvironments. Since PPP1R11 silencing increases cytokine production in T cells, inhibiting PPP1R11 might augment anti-tumor immune responses in the context of cancer immunotherapy .

• Inflammatory conditions: PPP1R11 overexpression reduces inflammatory cytokine production but may compromise pathogen clearance . This presents a complex therapeutic consideration where timing and context would be critical - PPP1R11 enhancement might benefit conditions of excessive harmful inflammation, while PPP1R11 inhibition might improve pathogen clearance during acute infection.

The development of small molecule modulators of PPP1R11 activity, or targeted delivery of PPP1R11-modifying agents to specific cell types, represents promising future directions for therapeutic intervention.

How do post-translational modifications affect PPP1R11 function, and what techniques can be used to study them?

Post-translational modifications (PTMs) likely play critical roles in regulating PPP1R11 function, affecting its stability, localization, and activity as both a phosphatase inhibitor and E3 ligase. While current literature on PPP1R11 PTMs is limited, researchers can employ the following techniques to investigate them:

• Mass spectrometry-based PTM mapping: Using enrichment strategies coupled with high-resolution mass spectrometry to identify phosphorylation, ubiquitination, SUMOylation, acetylation and other modifications on purified PPP1R11.

• Site-directed mutagenesis: Creating PPP1R11 mutants with alanine substitutions at potential modification sites to assess functional consequences on its dual activities.

• Proximity labeling proteomics: Employing BioID or APEX2 fusions with PPP1R11 to identify proteins that interact with PPP1R11 in a modification-dependent manner.

• Stimulus-dependent PTM analysis: Examining how different cellular stimuli (TLR2 ligands, kinase activators/inhibitors) affect the PTM status of PPP1R11.

• Pharmacological inhibition: Using specific inhibitors of kinases, phosphatases, or other PTM-regulating enzymes to determine their effects on PPP1R11 function.

Understanding PPP1R11 PTMs is particularly relevant since the protein likely requires regulatory mechanisms to switch between its roles in different cellular contexts. For example, in TLR2 signaling pathways, PPP1R11 is upregulated in response to TLR2 ligand stimulation , suggesting that transcriptional and post-translational regulation work together to modulate PPP1R11 activity during immune responses.

What is the relationship between PPP1R11's dual functions as a phosphatase inhibitor and E3 ligase?

PPP1R11 possesses the unusual dual functionality of acting as both a protein phosphatase 1 (PP1) inhibitor and a RING finger E3 ubiquitin ligase . The relationship between these functions represents a complex and intriguing research question:

• Structural basis: Researchers should investigate whether these functions are mediated by distinct domains within PPP1R11. Domain mapping experiments using truncated variants can determine if the phosphatase inhibitory region is separate from the E3 ligase catalytic domain.

• Cross-regulation: Studies should examine whether PPP1R11's E3 ligase activity affects its phosphatase inhibitory function and vice versa. For instance, does PPP1R11 ubiquitinate PP1 to regulate its activity or stability?

• Substrate specificity determinants: Research should focus on identifying factors that direct PPP1R11 toward phosphatase inhibition versus ubiquitination activities in different contexts. This might involve identifying interaction partners that modulate PPP1R11 function.

• Signaling pathway integration: Investigations should determine how PPP1R11's dual functions integrate different signaling pathways. For example, in T cells, RNAseq analyses indicate that PPP1R11 may affect phosphatidylinositol signaling, MAPK-AKT, and NF-κB pathways , which could involve both phosphatase inhibition and targeted ubiquitination.

• Evolutionary perspective: Comparative genomics approaches could reveal how PPP1R11's dual functionality evolved and whether this represents an example of protein moonlighting or domain fusion during evolution.

Understanding this dual functionality could provide insights into how cells coordinate phosphorylation and ubiquitination networks to regulate complex processes like inflammatory responses and cell cycle progression.

What are common technical challenges when working with PPP1R11 antibodies and how can they be addressed?

Researchers working with PPP1R11 antibodies may encounter several technical challenges:

Additionally, when working with PPP1R11 antibodies for co-immunoprecipitation studies to identify interaction partners, researchers should consider crosslinking antibodies to beads to prevent heavy and light chain interference in subsequent Western blot analysis.

How can researchers validate that PPP1R11 antibodies are specifically detecting their target in experimental systems?

Thorough validation of PPP1R11 antibody specificity is essential for reliable experimental outcomes:

• Genetic validation: Use samples with PPP1R11 gene knockout or knockdown to confirm loss of signal. CRISPR-Cas9 editing targeting the first exon of Ppp1r11 can generate knockout cell lines for validation purposes .

• Overexpression controls: Compare antibody signal in cells overexpressing tagged PPP1R11 versus empty vector controls to confirm detection of the correct protein.

• Peptide competition: Pre-incubate the antibody with the immunizing peptide before immunodetection to demonstrate specific binding.

• Multiple antibodies comparison: Use antibodies raised against different epitopes of PPP1R11 to confirm consistent detection patterns.

• Immunoprecipitation-mass spectrometry: Perform immunoprecipitation with the PPP1R11 antibody followed by mass spectrometry to confirm capture of PPP1R11 and identify potential cross-reactive proteins.

• Orthogonal detection methods: Correlate protein detection with mRNA levels using qPCR to validate expression patterns across different samples.

• Expected molecular weight: Confirm that the detected band matches the expected molecular weight of PPP1R11 (approximately 14 kDa), accounting for any post-translational modifications or tags.

Researchers studying PPP1R11's role in TLR2 signaling have successfully validated antibody specificity using both CRISPR-generated knockout cells and expression validation with tagged constructs .

What experimental design considerations are important when studying the relationship between PPP1R11 and its target proteins?

When investigating PPP1R11 interactions with target proteins like TLR2 or PP1, researchers should consider these experimental design elements:

• Appropriate controls: Include both positive controls (known interactions) and negative controls (non-relevant proteins) in interaction studies. For example, when studying PPP1R11-TLR2 interactions, TLR4 might serve as a specificity control .

• Bidirectional validation: Confirm interactions by immunoprecipitating either PPP1R11 or its target protein and blotting for the partner protein. For robust validation, the interaction should be detectable in both directions.

• Endogenous versus overexpression systems: While overexpression facilitates detection, verify that interactions occur between endogenous proteins to confirm physiological relevance.

• Domain mapping: Use truncation or point mutants of both PPP1R11 and target proteins to identify specific interaction domains. For example, the RING domain of PPP1R11 is critical for its E3 ligase activity, while lysine-754 of TLR2 is the ubiquitination site .

• Stimulus dependency: Assess whether interactions are constitutive or induced by specific stimuli. For instance, PPP1R11 protein levels increase in response to TLR2 ligand (Pam3CSK4) stimulation .

• Temporal dynamics: Study the kinetics of interactions, as timing may be critical. PPP1R11 upregulation after TLR2 stimulation gradually reduces TLR2 protein levels at about 4-6 hours post-stimulation .

• Functional readouts: Include downstream functional assays to demonstrate biological significance of interactions. For PPP1R11-TLR2, this includes measuring inflammatory cytokine production , while for PPP1R11-PP1 interactions, assessing phosphatase activity is informative .

This comprehensive approach ensures that identified interactions are specific, physiologically relevant, and mechanistically informative.