epr1 Antibody

What is EPR1 and what cellular functions does it mediate?

EPR1 (Effector Cell Protease Receptor-1) is characterized by a cysteine-rich extracellular module, a single membrane-spanning domain, and a serine-rich cytoplasmic tail featuring at least 15 potential phosphorylation sites. This receptor plays a critical role in coagulation processes by functioning as a receptor for the coagulation protease factor Xa. The protein contains multiple structural features including 2 N-linked glycosylation sites, 4 O-linked glycosylation sites, and a chondroitin sulfate attachment site, which may provide anchoring for carbohydrate chains. EPR1 transfectants bind to factor Xa in a specific and saturable manner, and in the absence of factor V/Va, they promote prothrombin activation in a factor Xa concentration-dependent reaction. The receptor is notably expressed by activated platelets and megakaryocytes, where it contributes to hemostatic functions .

What are the key structural characteristics of commercial EPR1 antibodies?

Most commercially available EPR1 antibodies are polyclonal antibodies raised in rabbits against synthetic peptides from specific regions of human EPR1. For example, many target the C-terminal region (amino acids 308-337) of human EPR1. These antibodies are typically purified using protein G affinity chromatography to ensure high specificity. Commercial preparations come in both unconjugated forms and conjugated versions with various fluorophores (such as AbBy Fluor® 488, 555, 594, 647, 680) or biotin tags to facilitate different detection methods. The general molecular weight of the antibody is approximately 150 kDa, though this can vary slightly between preparations. Isotype characterization typically identifies these as IgG antibodies .

What are the recommended applications for EPR1 antibodies?

EPR1 antibodies have been validated for multiple research applications with human samples. Western blotting (WB) represents the most widely validated application, typically using dilutions of approximately 1:1000, though optimal concentrations should be determined empirically for each experimental system. Additionally, these antibodies perform well in enzyme-linked immunosorbent assays (ELISA) for quantitative assessment of EPR1 levels. Immunohistochemistry (IHC) applications are also supported, particularly for formalin-fixed paraffin-embedded tissues. Some preparations are additionally validated for immunofluorescence (IF) studies, especially the fluorophore-conjugated versions. Researchers should note that most commercial EPR1 antibodies show primary reactivity with human samples, and cross-reactivity with other species should be verified before experimental use .

How should EPR1 antibodies be stored and handled to maintain activity?

For optimal preservation of antibody activity, EPR1 antibodies should be maintained refrigerated at 2-8°C for short-term storage (up to 6 months). For long-term storage, aliquoting and freezing at -20°C is recommended to prevent freeze-thaw cycles that can degrade antibody performance. When working with the antibodies, centrifugation of the vial may occasionally be necessary as small volumes of antibody can become entrapped in the seal during shipment and storage. Most preparations are supplied in PBS buffer containing 0.09% (w/v) sodium azide as a preservative. When handling, researchers should take appropriate precautions given the presence of sodium azide and follow institutional guidelines for laboratory safety. For diluted working solutions, prepare only the volume needed for immediate experiments and maintain at 4°C for maximum stability .

What positive controls are recommended for validating EPR1 antibody performance?

When validating EPR1 antibody performance in experimental systems, HL60 cell lysates represent a well-established positive control, as demonstrated in Western blot applications. These human promyelocytic leukemia cells express detectable levels of EPR1 protein. For tissue-based applications, researchers should consider using platelet-rich preparations or samples from megakaryocyte lineages, as these cell types have been documented to express EPR1, particularly when in activated states. When running validation experiments, include both positive and negative controls (such as cell lines known not to express EPR1) to confirm specificity. Additionally, blocking peptides specific to the EPR1 antibody epitope (such as synthetic peptides corresponding to amino acids 308-337) can be used to confirm binding specificity in competitive binding assays .

How can EPR1 antibodies be used to investigate platelet activation mechanisms?

To investigate platelet activation mechanisms using EPR1 antibodies, researchers should implement a multi-phase experimental approach. Begin with platelet isolation using density gradient centrifugation, followed by activation using established agonists such as thrombin (0.1-1 U/ml), collagen (1-5 μg/ml), or ADP (5-20 μM). For flow cytometry analysis, use 1×10^6 platelets per sample and stain with fluorophore-conjugated EPR1 antibodies (typically at 1:100 dilution) alongside established platelet activation markers (such as P-selectin/CD62P). When analyzing results, use a gate strategy that first identifies platelets based on forward/side scatter properties and CD41/CD61 positivity, then assess EPR1 expression in both resting and activated populations. For imaging studies, perform immunofluorescence on adhered platelets using 1:200 dilution of primary EPR1 antibody followed by appropriate secondary detection. Quantify EPR1 distribution changes following activation, noting particularly its co-localization with factor Xa and other coagulation components. This approach allows for comprehensive characterization of how EPR1 expression and localization shift during the platelet activation process, providing insight into its role in hemostasis .

What technical considerations should be addressed when using EPR1 antibodies in complex biological samples?

When working with EPR1 antibodies in complex biological samples, multiple technical challenges must be addressed. First, optimize protein extraction protocols to preserve EPR1's native conformation; for membrane proteins like EPR1, use non-ionic detergents (such as 1% NP-40 or 0.5% Triton X-100) in extraction buffers. Include phosphatase inhibitors (such as 1 mM sodium orthovanadate) to preserve phosphorylation states of EPR1's cytoplasmic tail, which contains at least 15 potential phosphorylation sites. For western blotting applications, transfer protocols should be optimized for transmembrane proteins - using lower methanol concentrations (5-10%) in transfer buffer can improve transfer efficiency. When analyzing samples with high glycoprotein content, consider pre-treating with PNGase F to remove N-linked glycans for more accurate molecular weight determination, as EPR1 contains multiple glycosylation sites. For immunoprecipitation experiments, pre-clear samples with protein G beads before adding EPR1 antibody to reduce non-specific binding. When interpreting results from tissue samples, particularly those with activated platelets, account for potential variation in EPR1 expression levels that correlate with platelet activation states. Additionally, when analyzing patient samples, document any anticoagulant therapy that might affect EPR1-factor Xa interactions and subsequent detection .

How can researchers effectively design experiments to study EPR1's interaction with factor Xa?

Designing effective experiments to study EPR1's interaction with factor Xa requires a multi-methodological approach. Begin with co-immunoprecipitation studies using EPR1 antibodies in cellular lysates from activated platelets or EPR1-transfected cell lines, followed by immunoblotting for factor Xa. Implement surface plasmon resonance (SPR) analysis using purified components, with EPR1 immobilized on sensor chips and factor Xa introduced at concentrations ranging from 1-100 nM to determine binding kinetics (Ka, Kd, and KD values). For cellular systems, develop proximity ligation assays using primary antibodies against EPR1 and factor Xa, which will generate fluorescent signals only when proteins are within 40 nm of each other. Use site-directed mutagenesis to modify specific residues in EPR1's extracellular domain and assess how these alterations affect factor Xa binding through functional prothrombin activation assays. Additionally, evaluate the effects of physiological factors known to modulate coagulation (calcium concentration, presence of phospholipids, pH variations) on EPR1-factor Xa interactions. For visualization of interactions in cellular contexts, implement fluorescence resonance energy transfer (FRET) approaches using appropriately labeled antibodies or recombinant proteins. This comprehensive experimental design will provide detailed characterization of the EPR1-factor Xa interaction parameters and their biological significance .

What approaches can be used to quantify EPR1 expression levels in different cellular contexts?

Quantifying EPR1 expression across different cellular contexts requires implementing multiple complementary techniques. For absolute quantification, develop a quantitative ELISA using EPR1 antibodies with a standard curve generated from recombinant EPR1 protein at concentrations ranging from 0.1-100 ng/ml. When performing Western blot analysis for relative quantification, use β-actin or GAPDH as loading controls and implement densitometric analysis with at least three biological replicates. For single-cell resolution, optimize flow cytometry protocols using directly conjugated EPR1 antibodies (typically at 1:50-1:100 dilution), calibrating results against quantitative beads to convert mean fluorescence intensity to molecules of equivalent soluble fluorophore (MESF). In tissue contexts, implement quantitative immunohistochemistry using automated image analysis software to measure staining intensity and distribution patterns. For gene expression analysis, design RT-qPCR primers spanning exon-exon junctions of the EPR1 transcript, normalizing results to multiple reference genes validated for stability in your experimental system. When comparing expression between different cell types or conditions, account for differences in cell size and total protein content by normalizing to consistent cell numbers or total protein concentrations. This multi-platform approach ensures robust quantification of EPR1 expression that accounts for technical variables while providing insights into biological regulation .

How can EPR1 antibodies be integrated into advanced imaging techniques for coagulation research?

Integrating EPR1 antibodies into advanced imaging techniques requires specialized protocols for each imaging modality. For super-resolution microscopy (such as STORM or PALM), conjugate EPR1 antibodies with photoswitchable fluorophores like Alexa Fluor 647 at a labeling ratio of approximately 1-2 fluorophores per antibody to maintain antibody functionality while enabling single-molecule localization. When implementing intravital microscopy to visualize EPR1 in thrombus formation in vivo, inject fluorescently labeled EPR1 antibodies (typically 50-100 μg per mouse) 24 hours before imaging, and use spinning disk confocal microscopy to capture dynamic interactions with factor Xa (separately labeled with spectrally distinct fluorophores). For electron microscopy applications, use immunogold labeling with EPR1 antibodies conjugated to gold nanoparticles (typically 10-15 nm diameter), employing high-pressure freezing and freeze substitution to preserve membrane structures. In two-photon microscopy applications, use EPR1 antibodies conjugated with fluorophores having high two-photon cross-sections (such as rhodamine derivatives) for deep tissue imaging. When implementing multiplexed imaging, design panels that include EPR1 alongside markers for platelet activation (P-selectin), fibrin formation, and factor Xa localization using spectrally distinct fluorophores. These advanced imaging approaches enable spatial and temporal resolution of EPR1 dynamics during coagulation processes that cannot be achieved through conventional biochemical methods .

What are common issues when using EPR1 antibodies in Western blotting and how can they be resolved?

When using EPR1 antibodies in Western blotting applications, researchers frequently encounter several challenges that require systematic troubleshooting. Weak or absent signals often result from insufficient protein extraction, particularly since EPR1 is a membrane protein. To resolve this, implement optimized lysis buffers containing 1% NP-40 or 0.5% Triton X-100, combined with sonication (3-5 pulses, 10 seconds each) to enhance membrane protein solubilization. Multiple or non-specific bands may appear due to post-translational modifications of EPR1, including its multiple glycosylation sites. Address this by pre-treating samples with specific glycosidases (PNGase F for N-linked glycans, O-glycosidase for O-linked glycans) to reduce heterogeneity. High background signals often indicate suboptimal blocking or washing conditions; increase blocking time to 2 hours at room temperature using 5% non-fat dry milk in TBST, and extend wash steps to 15 minutes each (repeated 4 times). For samples with low EPR1 expression, implement signal enhancement systems such as biotin-streptavidin amplification or enhance protein loading to 50-75 μg per lane. When transferring EPR1 (particularly due to its membrane-spanning domain), use a semi-dry transfer system with reduced methanol concentration (5-10%) in transfer buffer and extend transfer time by 25-30%. Finally, when working with clinical samples, note that anticoagulant treatments may alter EPR1 expression or conformation, potentially affecting antibody recognition; document treatment histories when interpreting results .

How can researchers address epitope masking issues when detecting EPR1 in different sample types?

Addressing epitope masking issues when detecting EPR1 requires implementation of optimized epitope retrieval strategies tailored to sample preparation methods. For formalin-fixed paraffin-embedded (FFPE) tissues, implement a two-step antigen retrieval process: first heat-mediated retrieval using citrate buffer (pH 6.0) at 95-98°C for 20 minutes, followed by a brief protease treatment (0.05% trypsin for 5-10 minutes at 37°C) to further expose membrane epitopes. When working with frozen sections, optimize fixation using 2-4% paraformaldehyde for precisely 10 minutes, as overfixation can mask EPR1 epitopes. For native protein interaction studies, where binding partners may obscure antibody access to EPR1, incorporate a gentle detergent treatment (0.1% Saponin) in the antibody incubation buffer to partially disrupt protein-protein interactions without denaturing EPR1. In flow cytometry applications, particularly with platelets or other blood components, include a pre-incubation step with Fc receptor blocking reagents (10% normal serum matching the secondary antibody species) to reduce non-specific binding. When targeting the C-terminal region of EPR1, which contains multiple phosphorylation sites, consider phosphatase treatments on parallel samples to determine if phosphorylation status affects epitope recognition. For particularly challenging samples, implement a panel approach using multiple EPR1 antibodies targeting different epitopes to provide complementary detection. Document successful epitope retrieval protocols for specific tissue types and experimental conditions to ensure reproducibility across studies .

What strategies can optimize EPR1 antibody performance in immunoprecipitation experiments?

Optimizing EPR1 antibody performance in immunoprecipitation (IP) experiments requires attention to several critical parameters. Begin by selecting lysis conditions that preserve native protein conformation; for EPR1, use buffers containing 1% digitonin or 0.5% CHAPS rather than stronger ionic detergents, supplemented with protease inhibitors (complete protease inhibitor cocktail at 1X concentration) and phosphatase inhibitors (1 mM sodium orthovanadate, 5 mM sodium fluoride). Pre-clear lysates thoroughly using 50 μl of protein G beads per 1 mg of total protein for 1 hour at 4°C to reduce non-specific binding. For antibody binding, implement extended incubation periods (overnight at 4°C with gentle rotation) using 5-10 μg of EPR1 antibody per 1 mg of total protein. When isolating EPR1 complexes with factor Xa or other interaction partners, consider crosslinking approaches using membrane-permeable crosslinkers like DSP (dithiobis[succinimidyl propionate]) at 1-2 mM for 30 minutes before lysis to stabilize transient interactions. For elution, compare different strategies including low pH (glycine buffer, pH 2.5-3.0), competitive elution with excess immunizing peptide (100-200 μg/ml), or direct boiling in reducing sample buffer, selecting the approach that yields highest recovery with minimal antibody contamination. When validating IP results, implement reciprocal co-IPs using antibodies against putative EPR1 interaction partners and include appropriate negative controls (isotype-matched non-specific antibodies). For challenging samples with low EPR1 expression, scale up starting material and concentrate eluted proteins using TCA precipitation or similar methods before downstream analysis .

How should researchers validate the specificity of EPR1 antibody staining in microscopy applications?

Validating the specificity of EPR1 antibody staining in microscopy applications requires implementation of multiple complementary controls. First, perform peptide competition assays by pre-incubating the EPR1 antibody with 100-fold molar excess of the immunizing peptide (typically the C-terminal region, amino acids 308-337) before application to samples; specific staining should be significantly reduced or eliminated. Include biological negative controls such as cell lines with confirmed absence of EPR1 expression or tissues known not to express EPR1. For genetic validation, compare staining patterns in wild-type samples with those from EPR1 knockdown models generated using siRNA or CRISPR-Cas9 approaches; specific signal should be proportionally reduced with knockdown efficiency. Implement dual-labeling approaches using two different EPR1 antibodies targeting distinct epitopes - colocalization of signals strongly supports specificity. When examining tissues with endogenous biotin (such as liver or kidney), include avidin-biotin blocking steps before applying biotinylated EPR1 antibodies to prevent false-positive signals. For quantitative assessment of background, include secondary-only controls for each experiment and substract background signal values during image analysis. In multiplexed immunofluorescence experiments, prepare single-stained controls to confirm absence of spectral bleed-through between channels. Document optimal antibody concentrations (typically starting with 1:100-1:500 dilutions for immunofluorescence) and incubation conditions for each sample type and imaging system to ensure reproducibility across experiments .

How can computational approaches assist in improving EPR1 antibody design and epitope selection?

Recent advances in computational biology offer significant opportunities for enhancing EPR1 antibody design and epitope selection. Implementing structure-based computational approaches using RFdiffusion networks can enable the atomically accurate design of antibodies targeting specific EPR1 epitopes. This approach involves first generating high-resolution structural models of EPR1 using AlphaFold2 or RoseTTAFold, followed by epitope mapping to identify accessible surface regions with high antigenicity scores (particularly within the cysteine-rich extracellular domain). Once promising epitopes are identified, fine-tuned RFdiffusion networks can design complementary binding interfaces with atomic precision. The process involves generating diverse computational designs (typically 1000-5000 candidates), followed by energy minimization and filtering based on binding energy calculations. Selected designs can be further refined through molecular dynamics simulations (100-200 ns) to assess binding stability under physiological conditions. These computational approaches can specifically address challenges in targeting conformational epitopes within EPR1's extracellular domain that may be critical for factor Xa interaction. For validation, in silico designs can be tested experimentally through yeast display screening methodologies, enabling rapid identification of designs with desired binding properties. This integrated computational-experimental pipeline has demonstrated success in generating antibodies with atomic-level precision in both structure and epitope targeting for other proteins, and represents a promising approach for developing next-generation EPR1-targeting antibodies .

What approaches can be used to study EPR1 in patient samples and its potential relevance to thrombotic disorders?

Studying EPR1 in patient samples to investigate its relevance in thrombotic disorders requires a comprehensive translational research approach. Begin by establishing a biobank of plasma, platelet-rich plasma, and platelet pellets from well-characterized patient cohorts with various thrombotic conditions (venous thromboembolism, arterial thrombosis, thrombotic microangiopathies) alongside matched controls. Implement quantitative flow cytometry using fluorophore-conjugated EPR1 antibodies to measure platelet surface expression levels, establishing reference ranges from healthy donors (minimum 100 samples) stratified by age and sex. Develop multiplexed immunoassays combining EPR1 quantification with established thrombotic markers (D-dimer, tissue factor, PAI-1) to create comprehensive profiles. For genetic analysis, sequence the EPR1 gene region in patient cohorts to identify potential variants associated with thrombotic risk, followed by functional characterization of identified variants using site-directed mutagenesis and cellular expression systems. In tissue analysis from thrombectomy specimens, implement multiplexed immunohistochemistry to visualize EPR1 in relation to fibrin deposition and inflammatory markers. Correlate EPR1 expression patterns with clinical parameters including thrombosis recurrence, treatment response, and long-term outcomes through longitudinal patient follow-up. Additionally, assess how common anticoagulant therapies (direct factor Xa inhibitors, vitamin K antagonists) affect EPR1 expression and function in ex vivo platelet samples from treated patients. This translational approach can establish whether EPR1 represents a clinically relevant biomarker or therapeutic target in thrombotic conditions .

How can researchers investigate the potential role of EPR1 in COVID-19 coagulopathy?

Investigating EPR1's potential role in COVID-19-associated coagulopathy requires a systematic research approach integrating clinical samples with mechanistic studies. Begin by establishing a prospective biorepository of samples from COVID-19 patients stratified by disease severity and coagulation abnormalities, collecting platelets, plasma, and when possible, lung tissue from autopsy cases. Quantify EPR1 expression on platelets using flow cytometry with fluorophore-conjugated antibodies, comparing levels between COVID-19 patients with and without thrombotic complications. Measure soluble EPR1 in plasma using validated ELISA methods to determine if shedding occurs during infection. In parallel, develop in vitro models exposing platelets and endothelial cells to SARS-CoV-2 spike protein or patient-derived serum to assess direct effects on EPR1 expression and localization. Implement proximity ligation assays to visualize potential interactions between EPR1 and components of the SARS-CoV-2 entry machinery (ACE2, TMPRSS2) on relevant cell types. For mechanistic insights, evaluate how inflammatory mediators elevated in COVID-19 (IL-6, TNF-α) affect EPR1 expression and factor Xa binding using dose-response experiments. Additionally, assess whether direct factor Xa inhibitors can modulate COVID-19-induced platelet activation and if this effect correlates with EPR1 expression levels. This integrated approach can determine whether EPR1 represents a mechanistic link between SARS-CoV-2 infection and the hypercoagulable state observed in severe COVID-19, potentially informing therapeutic strategies .

What techniques can be used to study EPR1 post-translational modifications and their functional significance?

Studying EPR1 post-translational modifications (PTMs) and their functional significance requires integration of advanced proteomic techniques with functional assays. Begin with immunoprecipitation of EPR1 from relevant cellular contexts (activated platelets, megakaryocytes) using optimized protocols with phosphatase and deubiquitinase inhibitors (50 mM sodium fluoride, 10 mM N-ethylmaleimide) to preserve labile modifications. Subject immunoprecipitated EPR1 to high-resolution mass spectrometry analysis, implementing both collision-induced dissociation (CID) and electron transfer dissociation (ETD) fragmentation methods to comprehensively map modification sites. Focus particularly on characterizing the 15 potential phosphorylation sites in EPR1's cytoplasmic tail using titanium dioxide enrichment before MS analysis. For glycosylation analysis, employ a combination of enzymatic deglycosylation (PNGase F, O-glycosidase) and hydrophilic interaction liquid chromatography (HILIC) separation coupled with MS to characterize both N- and O-linked glycans at the 2 N-linked and 4 O-linked glycosylation sites. To determine functional significance, generate site-directed mutants replacing modified residues with non-modifiable counterparts (S/T→A for phosphorylation, N→Q for N-glycosylation) and assess effects on EPR1 membrane localization, factor Xa binding affinity, and downstream signaling. Implement real-time assays measuring calcium flux and prothrombinase complex assembly in cells expressing wild-type versus modification-deficient EPR1 variants. Additionally, determine if specific PTMs are dynamically regulated during platelet activation by analyzing EPR1 modifications at different time points after stimulation with physiological agonists. This comprehensive approach will establish mechanistic links between specific EPR1 modifications and its functional properties in hemostasis .

EPR1 Antibody Applications and Recommended Dilutions

EPR1 Structural Characteristics and Binding Properties

Troubleshooting Guide for EPR1 Antibody Applications