GPR115 Antibody

What is GPR115 and why is it relevant in cancer research?

GPR115, also known as ADGRF4, is a member of the adhesion G protein-coupled receptor (aGPCR) family, a unique subfamily of GPCRs. It has gained significant attention due to its involvement in cancer progression, particularly lung adenocarcinoma (LUAD).

GPR115 is expressed in human epidermis, specifically in KRT10-positive suprabasal, noncornified keratinocytes . More importantly, studies have demonstrated that GPR115 is significantly upregulated in non-small cell lung cancer (NSCLC) tissues compared to normal lung epithelial tissue . The protein contains domains associated with cell-cell and cell-matrix interactions, including epidermal growth factor-like domains, thrombospondin, leucine-rich regions, and cadherin repeats, which play crucial roles in cancer growth and metastasis .

What are the optimal immunohistochemistry protocols for GPR115 detection in tissue samples?

Based on published methodologies, the following optimized protocol is recommended for GPR115 detection in tissue samples:

Tissue preparation:

• For FFPE tissues: Deparaffinize sections and rehydrate through a graded series of alcohol (100%, 95%, and 75%)

• For cryosections: Use appropriate fixation methods

Antigen retrieval:

• Immerse sections in citrate buffer at 99°C for 30 minutes

• Allow to cool to room temperature

Blocking and primary antibody:

• Quench endogenous peroxidase with 3% H₂O₂

• Incubate with anti-GPR115 antibody (1:200 dilution recommended, e.g., HPA007158, Atlas Antibodies) at 4°C overnight

Detection and visualization:

• Apply horseradish peroxidase-conjugated secondary antibody at room temperature for 1 hour

• Develop with 3,3′-diaminobenzidine solution

• Counterstain with hematoxylin

• Scan using an Automated Quantitative Pathology Imaging System

Scoring:

• Use a semi-quantitative system based on staining intensity and percentage of cells stained:

  • 0 (negative, blue)

  • 1+ (weak, yellow)

  • 2+ (positive, brown-red)

  • 3+ (strong, brown)

• Calculate H-score as: sum of (intensity score × percentage of cells with that intensity)

• Final scores range from 0-300, with a median score of 183 often used as a cutoff for high versus low expression

How can I verify the specificity of GPR115 antibodies for my research?

Validating antibody specificity is crucial for reliable GPR115 research. Multiple complementary approaches should be employed:

Knockout/knockdown controls:

• Compare staining between wild-type cells and GPR115 knockout or knockdown cells

• Studies have used HaCaT wild-type keratinocytes alongside HaCaT GPR115 knockout clones where GPR115 ECD antibody stained 5-8% of wild-type cells but almost none of the GPR115KO cells

Overexpression systems:

• Express tagged versions of GPR115 (HA-tagged or Flag-tagged) in cell lines with low endogenous expression

• In studies using Cos-7 cells expressing HA-GPR115, researchers observed one-to-one overlapping of the Tag with GPR115 ECD antibody labeling

Pre-absorption controls:

• Preincubate GPR115 antibody with cells overexpressing GPR115

• Apply pre-absorbed antibody to tissue sections

• Research has shown that epidermal staining was strongly reduced after preincubation of the antibody with Cos-7 cells expressing GPR115

Western blot validation:

• Perform western blotting on multiple cell lines

• GPR115 typically appears as a band at approximately 90-110 kDa

• Compare expression patterns in GPR115-expressing and control cell lines

Cross-antibody validation:

• Use multiple antibodies targeting different epitopes of GPR115

• Compare staining patterns to ensure consistency across different antibodies

What cell lines are most appropriate for studying GPR115 function in cancer research?

Based on published research, the following cell lines have been successfully used to study GPR115 and are recommended for different experimental purposes:

Lung adenocarcinoma (LUAD) cell lines:

• H1650 and SPCA: These express high levels of GPR115 and have been used for functional studies including proliferation, migration, and invasion assays

• A549: Human lung carcinoma cell line with detectable GPR115 expression

• H1975: Another LUAD cell line used in GPR115 research

Epithelial cell lines:

• HaCaT: Human keratinocyte cell line useful for studying GPR115 in epithelial biology. Both wild-type and GPR115 knockout versions have been used for antibody validation

• A431: Human epithelial carcinoma cell line with detectable GPR115 expression

• RT-4: Human bladder carcinoma cell line expressing GPR115

Other relevant cell lines:

• HeLa: Human cervical epithelial carcinoma cell line showing GPR115 expression in western blot analyses

• Cos-7: Often used for overexpression studies due to low endogenous expression

• HEK293: Human embryonic kidney cell line commonly used for transfection with GPR115 constructs

When selecting cell lines, it's important to verify their baseline GPR115 expression through western blot or RT-PCR analysis before proceeding with functional studies.

How do I design experiments to study GPR115's role in cancer cell migration and invasion?

Based on published methodologies, the following experimental designs are recommended:

Wound Healing Assay for Migration:

• Grow cells (e.g., H1650 or SPCA lung cancer cell lines) to 90% confluence

• Modulate GPR115 expression (siRNA knockdown or overexpression)

• Create a wound by scraping the monolayer with a micropipette tip

• Culture in reduced serum medium (e.g., RPMI 1640 with 1% FBS)

• Wash gently with PBS to remove non-adherent cells

• Image wounds at 0, 24, and 48 hours using an inverted microscope

• Quantify wound healing rate using Image J software

• Analyze using two-way ANOVA

Transwell Invasion Assay:

• Coat Transwell chambers with Matrigel

• Harvest cells 24 hours after GPR115 modulation

• Add 10^5 cells/well to upper chambers

• Add medium with 10% FBS to lower chambers as chemoattractant

• Incubate for 48 hours

• Process chambers: wash with PBS, fix with 4% paraformaldehyde, stain with crystal violet

• Count invaded cells under microscope (200× magnification)

• Analyze using Image J software and two-way ANOVA

Molecular Markers to Assess:

• E-cadherin (epithelial marker)

• N-cadherin (mesenchymal marker)

• Vimentin (mesenchymal marker)

• LAMC2 (shown to be associated with GPR115, Spearman correlation coefficient=0.67)

Controls and Validation:

• Use multiple siRNAs targeting different regions of GPR115

• Include appropriate negative controls (siRNA-NC)

• Verify knockdown efficiency by western blot or qPCR

• Test effects in multiple cell lines for robustness

Published research has demonstrated that downregulation of GPR115 by RNA interference significantly inhibits cell proliferation, migration, and invasion in lung cancer cell lines , providing a foundation for these experimental approaches.

What is the correlation between GPR115 expression and cancer progression parameters?

Research has established significant correlations between GPR115 expression and cancer progression, particularly in lung adenocarcinoma. The following table summarizes key findings from clinical samples:

*P < 0.05

Important clinical correlations include:

These findings suggest GPR115 may be valuable as both a prognostic marker and potential therapeutic target in LUAD.

What are the technical challenges in detecting GPR115 by Western blot?

Western blot detection of GPR115 presents several technical challenges that researchers should anticipate and address:

Molecular weight variation:

• GPR115 appears at different molecular weights in different systems:

  • Approximately 90 kDa in some studies

  • Approximately 100-110 kDa in others

• This variation may be due to post-translational modifications, particularly glycosylation (note research on "GPR115 mutGlyc and GPR115 noGlyc" constructs)

Antibody selection and validation:

• Multiple antibodies are commercially available with varying specificity and applications:

  • Mouse monoclonal antibodies (clones 527003, 527018)

  • Goat polyclonal antibodies

  • Rabbit polyclonal antibodies

• Careful validation is essential using:

  • GPR115 knockout/knockdown controls

  • Overexpression systems with tagged GPR115

Sample preparation optimization:

• Buffer systems affect detection quality:

  • "Immunoblot Buffer Group 1" versus "Immunoblot Buffer Group 8"

• Recommended procedures:

  • Use PVDF membrane for transfer

  • Apply antibody at 1-2 µg/mL concentration

  • Use appropriate reducing conditions

  • Include protease inhibitors to prevent degradation

Cell line selection:
Successful western blot detection has been reported in:

• Human peripheral blood mononuclear cells (PBMC)

• HeLa cells

• A431, RT-4, and A549 cell lines

When optimizing western blot protocols for GPR115, it's advisable to test multiple antibodies, validate with appropriate controls, and carefully optimize lysis and detection conditions for your specific experimental system.

What is the significance of intracellular versus membrane localization of GPR115?

The subcellular localization of GPR115 has important functional implications that researchers should consider:

Observed localization patterns:

• In human epidermis, GPR115 shows "apparent intracellular distribution in keratinocytes in vivo and lacked the expected membrane-associated localization pattern"

• In cancer tissues, "GPR115 was present in both the cytoplasm and membrane of cancer cells"

• In basal keratinocytes, GPR115-positive cells "touched the basal membrane only with little membrane extensions but not across their entire basal site"

Functional implications:

• Receptor signaling: As an adhesion GPCR, GPR115 would typically function at the cell membrane. Intracellular localization might indicate:

  • Receptor internalization after activation

  • Storage pools awaiting mobilization

  • Non-canonical signaling mechanisms

  • Altered trafficking in disease states

• Cell adhesion properties: The distribution pattern may reflect:

  • Different functional states during cell differentiation

  • Changes in cell-cell and cell-matrix interactions

  • Altered receptor processing in malignant transformation

• Research considerations:

  • Different fixation and staining protocols might affect observed localization

  • Co-localization studies with organelle markers can help determine the exact subcellular compartment

  • The balance between membrane and intracellular GPR115 may be dynamically regulated

Understanding these localization patterns is crucial for interpreting functional studies and may provide insights into both normal biology and pathological processes involving GPR115.

How can I interpret discrepancies in GPR115 expression patterns across different studies?

When faced with apparent discrepancies in GPR115 expression patterns, consider the following analytical framework:

Methodological variables to consider:

• Antibody differences: Different antibodies may recognize distinct epitopes or forms of GPR115

  • "GPR115 ECD Ab" versus other antibody types

  • Monoclonal versus polyclonal antibodies

  • Different detection systems (HRP, fluorescence)

• Detection techniques:

  • IHC scoring systems vary (H-score cutoff of 183 in some studies)

  • Western blot buffer systems affect protein detection

  • RNA versus protein detection methods may yield different results

Biological variables:

• Tissue and cell type specificity: GPR115 expression varies significantly:

  • "In few basal and in almost all KRT10-positive suprabasal, noncornified keratinocytes"

  • Expression in skin appendages shows "a very similar distribution as KRT1 and KRT10"

  • Differential expression between LUAD and LUSC

• Disease context:

  • Expression correlates with "differentiation level, tumor size, lymph node metastasis, tumor-node-metastasis stage"

  • Cancer versus normal tissue expression patterns differ substantially

Analytical approach for reconciliation:

• Carefully examine methodological details of each study

• Consider specific tissue/cell types and their pathological state

• Look for consensus patterns across multiple studies despite methodological differences

• Perform comparative analyses using multiple antibodies and detection methods

• Account for post-translational modifications that may affect detection

By systematically evaluating these factors, researchers can develop a more nuanced understanding of GPR115 expression patterns despite apparent discrepancies in the literature.

What are the latest molecular mechanisms linking GPR115 to cancer metastasis?

Research has begun to uncover the molecular mechanisms through which GPR115 contributes to cancer metastasis:

GPR115 and epithelial-mesenchymal transition (EMT):

• Downregulation of GPR115 is associated with changes in key EMT markers:

  • E-cadherin (epithelial marker)

  • N-cadherin (mesenchymal marker)

  • Vimentin (mesenchymal marker)

• These findings suggest GPR115 may promote metastasis by regulating EMT, a critical process in cancer cell invasion and dissemination

Association with extracellular matrix interactions:

• Bioinformatic analysis has revealed that GPR115 is closely associated with LAMC2 (Spearman correlation coefficient=0.67, P<0.05)

• LAMC2 (laminin subunit gamma 2) accumulates in:

  • ECM-receptor interaction pathways

  • Focal adhesion complexes

• This suggests GPR115 may influence how cancer cells interact with the extracellular matrix

Functional evidence:

• RNA interference experiments demonstrated that GPR115 knockdown:

  • Inhibited cell proliferation in lung cancer cell lines

  • Significantly reduced cell migration in wound healing assays

  • Decreased invasion through Matrigel in Transwell assays

• These functional studies provide direct evidence of GPR115's role in promoting metastatic behavior

Gene co-expression networks: