Recombinant Human Protein tyrosine phosphatase receptor type C-associated protein (PTPRCAP)

What is PTPRCAP and what are its alternative names?

PTPRCAP (Protein tyrosine phosphatase receptor type C-associated protein) is also known as CD45-AP and LPAP (Lymphocyte phosphatase-associated phosphoprotein). It was identified as a transmembrane phosphoprotein specifically associated with tyrosine phosphatase PTPRC/CD45 . The protein interacts with CD45/PTPRC, which is a key regulator of T- and B-lymphocyte activation .

What is the molecular weight of PTPRCAP protein?

The calculated molecular weight of PTPRCAP is approximately 21 kDa, though in experimental settings such as Western blot, it is often observed at 28-30 kDa . This discrepancy likely represents post-translational modifications that affect protein migration during gel electrophoresis.

What is the genomic location of the PTPRCAP gene?

The PTPRCAP gene is located on human chromosome 11q13.1 . In mouse models, the CD45-AP gene has been assigned to the centromeric end of mouse chromosome 19 .

What is the primary function of PTPRCAP?

PTPRCAP functions primarily as a positive regulator of protein tyrosine phosphatase PTPRC/CD45 . The interaction with PTPRC may be required for the stable expression of PTPRCAP . Additionally, CD45-associated protein inhibits CD45 dimerization and up-regulates its protein tyrosine phosphatase activity , which is crucial for immune cell signaling.

In which tissues is PTPRCAP primarily expressed?

PTPRCAP is predominantly expressed in lymphoid tissues, including bone marrow, tonsil, appendix, thymus, lymph node, and spleen . This expression pattern correlates with its function in immune cell regulation, particularly in T- and B-lymphocytes.

How can I detect PTPRCAP expression in tissue samples?

PTPRCAP expression can be detected using immunohistochemistry (IHC) with appropriate antibodies. According to available protocols, antigen retrieval with TE buffer pH 9.0 is suggested for optimal results, though citrate buffer pH 6.0 may also be used . PTPRCAP has been successfully detected in human tonsillitis tissue and human lymphoma tissue samples .

What cell lines are suitable for PTPRCAP research?

Jurkat cells (human T lymphocyte cells) have been verified to express PTPRCAP and are commonly used for functional studies . Additionally, lymphoblastoid cell lines derived from blood samples have been used for quantitative expression analysis of PTPRCAP .

What are the recommended antibody dilutions for PTPRCAP detection in various applications?

Based on validated protocols, the following dilutions are recommended:

• Western Blot (WB): 1:500-1:1000

• Immunohistochemistry (IHC): 1:50-1:500

• Immunofluorescence (IF)/ICC: 1:200-1:800

It is advisable to titrate these dilutions in each specific testing system to obtain optimal results.

How can I quantify PTPRCAP expression levels?

Real-time reverse transcription-PCR is an effective method for quantifying PTPRCAP expression levels. According to established protocols, total RNA should be extracted and first-strand complementary DNA synthesized using an oligo(dT) primer. Real-time PCR can then be performed using appropriate primers specific for PTPRCAP, with GAPDH often used as a normalization control .

What recombinant PTPRCAP proteins are available for experimental controls?

Several recombinant PTPRCAP proteins are available for experimental use:

• Full-length recombinant proteins (AA 1-206) with His tag

• Partial fragments such as AA 33-428 with His tag

• Control fragments such as AA 112-169

These proteins can be used for blocking experiments, ELISA standards, and positive controls in various assays.

How does PTPRCAP regulate CD45 phosphatase activity?

CD45-associated protein inhibits CD45 dimerization and up-regulates its protein tyrosine phosphatase activity . The mechanistic details involve specific protein-protein interactions that affect the conformational state of CD45. Studies using PTPRCAP-null mice have shown disruption of lymphocyte function and signaling, indicating that PTPRCAP plays a crucial role in CD45-mediated signaling pathways .

What is known about the interaction between PTPRCAP and the T-cell receptor signaling machinery?

PTPRCAP interacts with protein-tyrosine kinases involved in T cell receptor signaling . Specifically, studies have characterized the interactions of CD45-associated protein with the antigen receptor signaling machinery in T-lymphocytes. These interactions are essential for proper immune cell activation and function . Research has shown that disruption of PTPRCAP expression can lead to alterations in signaling cascades downstream of the T-cell receptor.

How are PTPRCAP promoter polymorphisms associated with cancer risk?

SNP rs869736 located at position -309 of the PTPRCAP promoter has been associated with susceptibility to diffuse-type gastric cancer. The minor-allele homozygote was significantly associated with a 2.5-fold increased susceptibility to diffuse-type gastric cancer (P = .0021), but not to intestinal-type (P = .30) .

This polymorphism affects promoter activity, as demonstrated in luciferase reporter assays. The cancer-risk, minor-allele T of rs869736 increased both promoter activity and specific nuclear protein-binding affinity compared to the non-risk, major-allele G. Endogenous transcript levels of PTPRCAP were linearly correlated with copy numbers of the risk-haplotype (P = .0060) .

What are the consequences of PTPRCAP gene knockout in animal models?

Studies using CD45-associated protein-null mice have demonstrated disruption of lymphocyte function and signaling . Biochemical and functional analyses of mice deficient in expression of PTPRCAP have provided insights into its role in immune system development and function. These knockout models have revealed that PTPRCAP is essential for normal T-cell development and function, as its absence leads to altered signaling cascades and immune responses .

How can I study PTPRCAP promoter activity experimentally?

Luciferase reporter assays have been successfully employed to study PTPRCAP promoter activity. DNA segments containing specific alleles of interest can be amplified by PCR using Pfu DNA polymerase and cloned into appropriate vectors (e.g., pGL3-Basic or pGL3-Promoter vectors). The recombinant constructs can then be transfected into suitable cell lines (e.g., MKN28 cells) and luciferase activity measured to assess promoter strength .

What electrophoretic mobility shift assay (EMSA) protocols work for studying transcription factor binding to the PTPRCAP promoter?

EMSA can be performed by incubating nuclear extracts with binding buffer containing poly(dI-dC), BSA, and dithiothreitol for 20 minutes at room temperature, followed by addition of a radioactively labeled probe for another 20 minutes. The reaction product can then be subjected to gel electrophoresis (6% polyacrylamide gel in 0.25x Tris/borate/EDTA running buffer) and visualized using appropriate scanning methods .

How can I predict transcription factors that bind to specific PTPRCAP promoter sequences?

Transcription factors that can bind to specific PTPRCAP promoter sequences (such as SNP rs869736 at position -309) can be predicted using various bioinformatics programs, including AliBaba 2.1, Match 1.0, MatInspector, Patch 1.0, TESS, TFSEARCH, and Tfsitescan. For optimal results, target organisms should be restricted to vertebrates or mammalians in these analyses .

What are the unexplored aspects of PTPRCAP function in immune regulation?

While PTPRCAP's role in regulating CD45 activity is established, many aspects of its broader function in immune regulation remain to be explored. Future research could investigate its potential involvement in other signaling pathways beyond CD45-mediated processes, as well as its potential role in various immune cell subsets beyond T and B lymphocytes.

How might PTPRCAP be targeted therapeutically in immune-related diseases?

Given its role in immune cell signaling, PTPRCAP represents a potential therapeutic target for immune-related diseases. Research into small molecule inhibitors or activators of PTPRCAP function could yield new therapeutic approaches for autoimmune disorders, immunodeficiencies, or certain types of cancer.

What is the potential role of PTPRCAP in other cancer types beyond gastric cancer?

While the association between PTPRCAP promoter polymorphisms and diffuse-type gastric cancer has been established, the potential role of PTPRCAP in other cancer types remains largely unexplored. Future studies could investigate associations between PTPRCAP expression or genetic variations and susceptibility to other malignancies, particularly those with immune system involvement.