PTPRR Antibody

What is PTPRR and what cellular functions does it regulate?

PTPRR (Protein Tyrosine Phosphatase Receptor Type R) functions primarily as a negative regulator of MAPK signaling pathways. It sequesters mitogen-activated protein kinases (MAPKs) such as MAPK1, MAPK3, and MAPK14 in the cytoplasm in an inactive form . PTPRR dephosphorylates these kinases, preventing their activation and nuclear translocation.

In specific tissues, PTPRR is expressed in brain, placenta, small intestine, stomach, uterus, and weakly in the prostate . Different isoforms show tissue-specific expression patterns; for example, isoform alpha is observed only in the brain, while isoform delta is expressed in brain, kidney, placenta, prostate, small intestine, and uterus .

Research has revealed diverse roles for PTPRR:

• In prostate cancer, it negatively regulates the RAS/ERK1/2 pathway

• In ovarian cancer, it suppresses Wnt/β-catenin pathway activation by dephosphorylating β-catenin at Tyr-142

• In neuromuscular junctions, it modulates MuSK signaling

What PTPRR antibody applications are most commonly validated for research?

PTPRR antibodies have been validated for multiple experimental applications, with varying degrees of optimization across different research contexts:

Researchers should note that optimal dilutions are sample-dependent, and each antibody should be titrated for specific experimental conditions .

What molecular weights should researchers expect when detecting PTPRR via Western blot?

PTPRR exists in multiple isoforms with different molecular weights, which can complicate Western blot analysis:

All PTPRR isoforms are relatively short-lived proteins with half-lives of approximately 3-5 hours and are constitutively phosphorylated on one or two protein kinase A and MAP kinase target sites .

How can researchers validate PTPRR antibody specificity for experimental applications?

Validation of PTPRR antibody specificity requires multiple complementary approaches:

• Peptide competition assay: Blocking with the immunizing peptide should eliminate specific signals. This was demonstrated with PTPRR antibody (17937 Proteintech) using peptide ag12145 .

• Genetic validation:

  • Use PTPRR knockout models or PTPRR-depleted cells via siRNA/esiRNA

  • Compare with overexpression systems using tagged PTPRR constructs

  • In one study, androgen-mediated PTPRR protein reduction was prevented when cells were depleted of AR using esiRNA, confirming specificity

• Cross-reactivity assessment:

  • Test against recombinant proteins of closely related phosphatases

  • Examine reactivity in tissues with known PTPRR expression profiles

  • Consider that PTPRR expression is high in brain tissue but low or absent in many other tissues

• Molecular weight verification:

  • Confirm band patterns match expected isoform distribution

  • PTPRR can appear at 32 kDa, 47 kDa, and 65 kDa depending on the isoform

• Subcellular localization:

  • Immunofluorescent staining in LNCaP cells showed PTPRR localizes to the cytoplasm

  • Verify localization patterns against published data

What methodological approaches are effective for studying PTPRR's role in MAPK signaling?

PTPRR's role in MAPK signaling can be studied through several methodological approaches:

• Phosphorylation state analysis:

  • Monitor ERK1/2 phosphorylation levels (Thr202/Tyr204) in response to PTPRR modulation

  • Research has shown that overexpression of PTPRR in androgen-stimulated cells decreases phosphorylation of ERK1/2

• Gain/loss-of-function studies:

  • Overexpress wild-type PTPRR or catalytically inactive mutants (e.g., PTPRR D554A)

  • Using lentiviral vectors with fluorescent markers (e.g., LWT009-GFP) enables FACS sorting of transduced cells

  • Analyze changes in downstream MAPK targets

• Protein-protein interaction assays:

  • Co-immunoprecipitation to detect PTPRR-MAPK physical interactions

  • Proximity ligation assays (PLA) to visualize protein interactions in situ

• Substrate trapping:

  • Use catalytically inactive PTPRR mutants to trap and identify physiological substrates

  • Mass spectrometry analysis of trapped complexes can reveal novel targets

• Functional readouts:

  • Cell proliferation assays (PTPRR overexpression reduces proliferation in prostate cancer cells)

  • Cell invasion assays (PTPRR modulation affects invasion in various cancer models)

When designing these experiments, researchers should consider that PTPRR activity may be context-dependent, varying across cell types and disease states.

How can PTPRR antibodies be utilized to investigate its role in cancer biology?

PTPRR has been implicated in multiple cancer types with context-dependent functions. Researchers can use PTPRR antibodies to investigate:

• Expression profiling across cancer stages:

  • PTPRR is downregulated in prostate cancer (3.381-fold reduction) and shows a 4.686-fold reduction in metastatic versus primary prostate cancer

  • In ovarian cancer cell lines, PTPRR was significantly downregulated compared to HOSE control cells

  • IHC analysis can reveal expression patterns in tissue microarrays

• Mechanistic studies in different cancer contexts:

  • In prostate cancer: Monitor PTPRR-mediated ERK1/2 dephosphorylation

  • In ovarian cancer: Investigate PTPRR's role in dephosphorylating β-catenin at Tyr-142

  • In colorectal tumorigenesis: Examine PTPRR silencing mechanisms

• Regulatory pathway analysis:

  • AR-dependent regulation: PTPRR is rapidly repressed by androgens in prostate cancer cells

  • Androgen-mediated down-regulation of PTPRR mRNA expression occurs even in the presence of protein synthesis inhibitor cycloheximide, suggesting direct regulation by AR

• Manipulating PTPRR function:

  • Similar to approaches with PTPRD, researchers could develop antibodies targeting PTPRR's extracellular domain to manipulate its dimerization status and function

  • This approach has therapeutic potential based on findings with related phosphatases

What are the critical considerations when using PTPRR antibodies in functional studies of neurodevelopment?

PTPRR plays important roles in neuronal development, requiring specific considerations when using PTPRR antibodies in this context:

• Isoform-specific detection:

  • Mouse gene Ptprr encodes multiple PTPRR isoforms with distinct expression patterns during neural development

  • Antibodies targeting different domains may detect specific subsets of isoforms

  • Verify which isoforms are detected by a specific antibody (e.g., isoform alpha is observed only in the brain)

• Developmental timing:

  • PTPRR expression changes during developmental stages

  • Time-course studies should use consistent antibody lots to minimize variability

  • Consider phosphorylation status changes at different developmental stages

• Subcellular localization:

  • Different PTPRR isoforms localize to distinct subcellular compartments

  • Use subcellular fractionation combined with Western blotting

  • For immunofluorescence, co-stain with organelle markers to confirm localization

• Functional readouts:

  • ERK1/2 phosphorylation is hyperphosphorylated in PTPRR-deficient mouse brains

  • Consider downstream transcriptional targets as functional readouts

  • In depression models, PTPRR regulates ERK dephosphorylation

• Cross-species considerations:

  • When studying model organisms, verify cross-reactivity of PTPRR antibodies

  • Some antibodies are predicted to react with zebrafish, bovine, horse, sheep, rabbit, dog, and Xenopus models

How can researchers address discrepancies in results when using different PTPRR antibodies?

When faced with discrepancies between different PTPRR antibodies, researchers should systematically evaluate:

• Epitope mapping and antibody characteristics:

  • Different antibodies target distinct regions of PTPRR:

    • ABIN519537: targets AA 1-657 (full-length)

    • ABIN7167514: targets AA 1-412

    • ABIN392828: targets AA 234-265 (N-terminal)

  • Clone type (monoclonal vs. polyclonal) affects specificity and sensitivity

• Validation status for specific applications:

  • Some antibodies have extensive validation (e.g., 17937-1-AP with validation in WB, IF, IHC, ELISA)

  • Others may be validated for limited applications

  • Check validation data for your specific application and species

• Protocol optimization:

  • Buffer compositions can significantly affect antibody performance

  • For Western blotting of PTPRR, sample preparation methods may affect detection of different isoforms

  • Fixation methods for IHC/IF should be optimized for PTPRR epitope preservation

• Controls to include:

  • Positive controls: tissues with known high PTPRR expression (brain tissue)

  • Negative controls: tissues with minimal PTPRR expression

  • Knockdown/knockout controls to confirm specificity

  • Peptide competition assays with immunizing peptides

• Reconciliation strategies:

  • Use multiple antibodies targeting different epitopes

  • Complement antibody-based methods with non-antibody techniques (e.g., mRNA expression)

  • Consider that different antibodies may preferentially detect specific isoforms or phosphorylation states

What are the optimal sample preparation methods for detecting PTPRR in different applications?

Sample preparation significantly impacts PTPRR detection across applications:

For Western Blotting:

• Cell lysis buffer considerations:

  • Use buffers containing phosphatase inhibitors to preserve phosphorylation status

  • Include protease inhibitors as PTPRR has a relatively short half-life (3-5 hours)

  • RIPA or NP-40 based buffers are commonly used for membrane proteins like PTPRR

• Protein denaturation:

  • Complete denaturation is essential for accessing epitopes in transmembrane proteins

  • Include reducing agents (β-mercaptoethanol or DTT) in sample buffer

  • Heat samples at 95°C for 5 minutes in Laemmli buffer

• Gel percentage optimization:

  • Use 8-10% gels for full-length PTPRR (65-74 kDa)

  • For detecting multiple isoforms (32-74 kDa), gradient gels (4-15%) may be preferable

For Immunohistochemistry/Immunofluorescence:

• Fixation methods:

  • Paraformaldehyde (4%) is commonly used for preserving PTPRR epitopes

  • For frozen sections, acetone or methanol fixation may preserve certain epitopes better

• Antigen retrieval:

  • Citrate buffer (pH 6.0) heat-induced epitope retrieval is often effective

  • Test both heat-mediated and enzymatic retrieval methods

• Blocking considerations:

  • Use species-appropriate serum (5-10%) or BSA (3-5%)

  • Include permeabilization step with 0.1-0.3% Triton X-100 for intracellular epitopes

For ELISA:

• Sample dilution series:

  • Optimize dilutions based on expected PTPRR concentrations

  • For rat samples, quantitative competition ELISA is available (ABIN512341)

  • For other species, quantitative formats are available (ABIN1057861, ABIN1057862)

How can researchers use PTPRR antibodies to study its interactions with other signaling molecules?

To study PTPRR interactions with other signaling molecules:

• Co-immunoprecipitation (Co-IP):

  • Use PTPRR antibodies for pulldown, then probe for interacting partners

  • Alternatively, immunoprecipitate suspected binding partners and probe for PTPRR

  • Ensure antibodies used for IP don't interfere with protein interaction sites

  • Example protocol:

    • Lyse cells in non-denaturing buffer (e.g., 1% NP-40, 150mM NaCl, 50mM Tris-HCl)

    • Pre-clear lysate with protein A/G beads

    • Incubate with PTPRR antibody (e.g., ABIN519538) overnight at 4°C

    • Add protein A/G beads, wash, and elute

    • Analyze by Western blot for binding partners (e.g., ERK1/2)

• Proximity Ligation Assay (PLA):

  • Enables visualization of protein-protein interactions in situ

  • Requires antibodies from different host species for PTPRR and binding partners

  • PTPRR antibody ABIN519538 has been validated for PLA applications

• Bimolecular Fluorescence Complementation (BiFC):

  • Tag PTPRR and potential binding partners with complementary fluorescent protein fragments

  • Use antibodies to confirm expression levels of fusion proteins

• FRET/FLIM analysis:

  • Label PTPRR and binding partners with appropriate fluorophores using validated antibodies

  • Monitor energy transfer as indication of protein proximity

• Substrate trapping:

  • Generate catalytically inactive PTPRR mutants (e.g., D554A)

  • Use antibodies to immunoprecipitate mutant PTPRR and identify trapped substrates

What strategies can researchers employ to differentiate between PTPRR phosphatase activity and expression levels?

Distinguishing between PTPRR expression and its phosphatase activity requires specific experimental approaches:

• Activity-based assays:

  • Immunoprecipitate PTPRR using validated antibodies (e.g., 17937-1-AP)

  • Measure phosphatase activity using synthetic substrates like pNPP

  • Alternatively, use physiological substrates such as phosphorylated ERK1/2

• Genetic manipulation with activity controls:

  • Compare wild-type PTPRR with catalytically inactive mutants (D554A)

  • Express both at comparable levels (confirm by Western blot)

  • Measure downstream effects (e.g., ERK1/2 phosphorylation)

• Inhibitor-based approaches:

  • Use general PTP inhibitors (sodium orthovanadate) alongside specific manipulations

  • Compare effects of inhibition versus protein reduction

• Monitoring phosphorylation of PTPRR itself:

  • PTPRR is constitutively phosphorylated on protein kinase A and MAP kinase target sites

  • Phosphorylation status may regulate activity independently of expression level

  • Use phospho-specific antibodies if available

• Temporal resolution studies:

  • PTPRR has a relatively short half-life (3-5 hours)

  • Monitor activity and expression changes over time following stimulation

  • Example: androgen treatment rapidly reduces PTPRR expression at both mRNA and protein levels

What are the key considerations when using PTPRR antibodies for quantitative analyses?

For quantitative analyses using PTPRR antibodies, researchers should address:

• Calibration and standardization:

  • Use recombinant PTPRR proteins as standards (available options include):

    • ABIN1316885: Human PTPRR from wheat germ

    • ABIN5711341: Human PTPRR from E. coli

    • ABIN2730150: Human PTPRR from HEK-293 cells

  • Create standard curves with known quantities for quantitative applications

• Signal normalization approaches:

  • For Western blots: Normalize to housekeeping proteins (α-Tubulin, actin)

  • For tissue samples: Consider cell-type specific expression patterns

  • When comparing disease states: Account for tissue composition differences

• Antibody binding characteristics:

  • Determine if antibody binding is affected by post-translational modifications

  • Assess linearity range for quantification

  • Account for potential limitations in detecting all isoforms equally

• Statistical considerations:

  • Perform technical and biological replicates

  • For clinical samples, account for inter-individual variability

  • When comparing disease states, substantial fold changes have been observed:

    • 3.381-fold reduction in prostate cancer relative to normal tissue

    • 4.686-fold reduction in metastatic versus primary prostate cancer

• ELISA-specific considerations:

  • Different analytical methods are available:

    • Quantitative Competition ELISA for rat samples (ABIN512341)

    • Quantitative ELISA for chicken and monkey samples (ABIN1057861, ABIN1057862)

  • Validate assay ranges and limits of detection for your specific sample type

How can researchers troubleshoot non-specific binding or high background when using PTPRR antibodies?

When encountering non-specific binding or high background with PTPRR antibodies:

• For Western blotting:

  • Increase blocking time/concentration (5% milk or BSA in TBST)

  • Optimize primary antibody dilution (start with 1:1000 for most PTPRR antibodies)

  • Increase washing duration and number of washes

  • Use higher stringency wash buffer (increase Tween-20 to 0.1-0.2%)

  • Consider alternative membrane types (PVDF vs nitrocellulose)

  • Run a peptide competition assay with the immunizing peptide

• For immunohistochemistry/immunofluorescence:

  • Optimize fixation conditions (overfixation can increase background)

  • Use gentler permeabilization methods

  • Extend blocking time with appropriate blocking agents

  • Include protein from the host species of the secondary antibody in blocking buffer

  • Try fluorophores with different excitation/emission profiles to reduce autofluorescence interference

• For ELISA:

  • Increase blocking time and wash frequency

  • Optimize antibody concentration through titration

  • Use validated ELISA kits with optimized formulations

  • Consider sample pre-clearing steps to remove interfering components

• For low signal issues:

  • PTPRR expression is tissue-dependent (highest in brain, low in many other tissues)

  • Consider signal amplification methods like TSA for low-expression tissues

  • Use enhanced chemiluminescence substrates for Western blotting

  • For clinical samples, compare with expression databases to set realistic expectations

What protocol modifications are necessary when studying post-translational modifications of PTPRR?

To effectively study post-translational modifications of PTPRR:

• Phosphorylation analysis:

  • PTPRR is constitutively phosphorylated on protein kinase A and MAP kinase target sites

  • Include phosphatase inhibitors (sodium orthovanadate, sodium fluoride, β-glycerophosphate) in all buffers

  • Use Phos-tag gels to separate phosphorylated from non-phosphorylated forms

  • For immunoprecipitation, consider using phospho-tyrosine antibodies (e.g., 4G10) to pull down phosphorylated PTPRR

• Glycosylation studies:

  • PTPRR contains potential N-glycosylation sites

  • Use deglycosylation enzymes (PNGase F) followed by Western blotting to assess glycosylation

  • Changes in apparent molecular weight can indicate glycosylation status

• Proteolytic processing:

  • Some receptor PTPs undergo proteolytic processing

  • Use antibodies targeting different domains to detect processed fragments

  • Compare full-length (74 kDa) versus processed forms (may correspond to observed 47 kDa, 32 kDa bands)

• Subcellular localization changes:

  • Post-translational modifications may alter localization

  • Use subcellular fractionation followed by Western blotting

  • For imaging studies, co-stain with organelle markers to track localization changes

• Dimerization analysis:

  • Dimerization has been implicated in regulating RPTP activity

  • Use non-reducing gel conditions to preserve dimers

  • Consider chemical crosslinking before cell lysis to stabilize weak interactions

How can researchers adapt PTPRR antibody protocols for different model organisms?

When adapting PTPRR antibody protocols across species:

• Species cross-reactivity verification:

  • Some PTPRR antibodies have confirmed reactivity with:

    • Human, mouse, and rat (e.g., DF12713)

    • Predicted reactivity with pig, zebrafish, bovine, horse, sheep, rabbit, dog, and Xenopus

  • Perform validation experiments with positive and negative controls from target species

• Sequence homology assessment:

  • Compare PTPRR protein sequences between species

  • Focus on antibodies targeting highly conserved regions

  • Consider epitope mapping to identify species-specific sequences

• Application-specific modifications:

  • For Western blotting: Adjust protein loading amounts based on expression levels in target species

  • For IHC/IF: Optimize fixation and antigen retrieval conditions for each species

  • For co-IP: Modify lysis buffer conditions based on tissue-specific considerations

• Isoform considerations across species:

  • Different species may express different ratios of PTPRR isoforms

  • Verify which isoforms are predominant in your model organism

  • Mouse Ptprr encodes multiple isoforms with distinct expression patterns

• Alternative approaches for non-validated species:

  • Consider raising custom antibodies against species-specific peptides

  • Use tagged PTPRR constructs in transfection/transduction experiments

  • Employ genetic approaches (CRISPR/Cas9) to validate antibody specificity

By systematically addressing these considerations, researchers can effectively adapt PTPRR antibody protocols for their specific model organisms and research questions.