GPR176 Antibody

What is GPR176 and why is it important in research?

GPR176 (G protein-coupled receptor 176) is an orphan G protein-coupled receptor that acts through the G-protein subclass G(z)-alpha and demonstrates agonist-independent basal activity to repress cAMP production. This receptor is also known by alternative names including RBU-15, HB-954, and AGR9 . GPR176 has a molecular weight of approximately 57 kilodaltons and plays significant roles in:

• Regulation of circadian rhythms in the suprachiasmatic nucleus (SCN)

• Possible involvement in cancer progression and immune regulation

• Cell signaling through cAMP-repressive pathways

Its importance in research stems from its emerging roles in multiple biological processes and pathological conditions, making it a valuable target for investigation in chronobiology, oncology, and immunology.

What applications are GPR176 antibodies validated for?

GPR176 antibodies from various suppliers have been validated for multiple research applications:

When selecting an antibody for your specific application, verify the validation data provided by the manufacturer for your specific species and application combination .

What species reactivity should I consider when selecting a GPR176 antibody?

Most commercially available GPR176 antibodies demonstrate reactivity with:

• Human (Homo sapiens)

• Mouse (Mus musculus)

• Rat (Rattus norvegicus)

Some antibodies offer broader cross-reactivity, including:

• Rabbit (Rb)

• Bovine (Bv)

• Dog (Dg)

• Guinea pig (GP)

• Horse (Hr)

• Pig (Pg)

• Yeast (Ys)

The homology between human GPR176 and its orthologs should be considered when selecting antibodies for non-human models. Carefully review the antibody's datasheet and validation data to ensure compatibility with your experimental system .

What controls should I include when using a GPR176 antibody?

Proper experimental controls are essential for validating GPR176 antibody specificity:

Positive controls:

• HEK293 cells transfected with GPR176 (as demonstrated in validation studies)

• A431 cells (human epidermoid carcinoma cell line) which express detectable levels of GPR176

• MCF7 cells (human breast adenocarcinoma cell line)

Negative controls:

• Native/mock-transfected HEK293 cells (which show minimal endogenous expression)

• Primary antibody omission control

• Isotype control antibody

• Blocking peptide competition (if available)

Tissue controls should be selected based on known expression patterns, with suprachiasmatic nucleus tissue serving as a positive control for GPR176 expression in circadian rhythm studies .

How does GPR176 function in cancer biology and what methodologies best capture this role?

Recent research has identified significant roles for GPR176 in cancer biology, particularly in gastric cancer (GC) and breast cancer:

In gastric cancer:

In breast cancer:

• GPR176 protein shows higher expression in breast cancer than in normal tissues

• Expression correlates with clinicopathological features including age, tumor size, and subtype

• GPR176 silencing suppresses proliferation, glucose catabolism, migration, invasion, and promotes apoptosis of breast cancer cells

Recommended methodologies:

• Multi-modal analysis: Combine protein expression (IHC/WB) with mRNA analysis (qRT-PCR) and methylation assessment to fully characterize GPR176 status

• Immunohistochemistry with digital pathology: For correlation with clinicopathological features and immune cell populations

• Functional assays after knockdown/overexpression: To assess effects on proliferation, migration, invasion, and immune response

• Integration with bioinformatic analyses: Using CIBERSORT, TIMER, and other algorithms to correlate with immune cell infiltration

These integrated approaches provide a comprehensive assessment of GPR176's role in cancer biology .

What mechanisms underlie GPR176 signaling and how can they be experimentally investigated?

GPR176 employs distinctive signaling mechanisms that differ from conventional GPCRs:

Key signaling characteristics:

• Acts through G-protein subclass G(z)-alpha rather than canonical Gi signaling

• Exhibits agonist-independent (constitutive) activity to repress cAMP production

• Contains a critical DRYxxV motif essential for both protein activity and stability

• Is insensitive to pertussis toxin (PTX), distinguishing it from typical Gi/o family-coupled receptors

• Undergoes N-glycosylation which is essential for proper cell surface expression

Experimental approaches for investigation:

• Mutagenesis studies:

  • Point mutations in the DRYxxV motif (e.g., V145R mutation) to disrupt activity

  • Modification of N-glycosylation sites to assess impact on localization and function

• Signaling pathway analysis:

  • cAMP GloSensor assays to measure cAMP repression activity

  • Pertussis toxin treatment to distinguish from canonical Gi signaling

  • Forskolin stimulation studies to assess suppression of adenylyl cyclase activity

• Protein-protein interaction studies:

  • Co-immunoprecipitation with G(z)-alpha

  • BRET/FRET assays to monitor receptor-G protein interactions in real-time

• Structural biology approaches:

  • Cryo-EM or X-ray crystallography to elucidate the unique structural features enabling constitutive activity

These methodologies can help decipher the non-canonical signaling mechanisms of GPR176 and its downstream effects .

How does GPR176 impact the tumor immune microenvironment and what techniques can assess this relationship?

GPR176 has emerged as a potential immunomodulator in cancer, particularly affecting the tumor immune microenvironment (TIME):

Key findings on GPR176 and immune regulation:

• Negatively correlates with CD8+ T cell infiltration in gastric cancer

• Associated with immune evasion through higher TIDE (Tumor Immune Dysfunction and Exclusion) scores

• Positively correlates with immunosuppressive cell populations (M0 macrophages, M2 macrophages, activated mast cells)

• Negatively correlates with cytotoxic immune cells (CD8+ T cells, activated NK cells, M1 macrophages)

• Positively correlates with multiple immune checkpoint molecules (LAG-3, PD-L1, PD-1, CTLA-4)

Recommended techniques for investigation:

• Computational deconvolution methods:

  • CIBERSORT algorithm to estimate immune cell composition from bulk RNA-seq data

  • TIMER algorithm to evaluate tumor-infiltrating immune cells

  • TIDE analysis to predict immune evasion potential

• Multiplex immunohistochemistry/immunofluorescence:

  • Simultaneous visualization of GPR176 expression with multiple immune cell markers

  • Spatial analysis of immune cell distribution relative to GPR176+ cells

• Flow cytometry:

  • Multi-parameter analysis of tumor-infiltrating immune cells in GPR176-high vs. GPR176-low tumors

  • Correlation of GPR176 expression with immune checkpoint molecules

• Functional co-culture assays:

  • GPR176-expressing tumor cells with immune effector cells to assess functional suppression

  • Assessment of T cell proliferation, cytokine production, and cytotoxicity

• In vivo models:

  • GPR176 knockout or overexpression in syngeneic tumor models to evaluate immune infiltration

  • Response to immune checkpoint inhibitors in GPR176-modified models

These approaches can elucidate how GPR176 influences the immune landscape in cancer and potentially identify opportunities for therapeutic intervention .

What are the challenges in detecting GPR176 protein expression and how can they be addressed?

Detecting GPR176 presents several technical challenges common to membrane-bound GPCRs:

Common challenges:

• Low endogenous expression levels in many cell types

• Post-translational modifications (particularly N-glycosylation) affecting antibody recognition

• Membrane localization complicating extraction and detection

• Conformational epitopes that may be lost during sample preparation

• Cross-reactivity with related GPCRs

Optimized methodologies:

• For Western blotting:

  • Optimize membrane protein extraction using specialized buffers containing appropriate detergents

  • Include deglycosylation controls (PNGase F treatment) to assess glycosylation's impact on detection

  • Use reducing and non-reducing conditions to evaluate effects on epitope accessibility

  • Recommended dilution: 1:1000 for most antibodies

• For immunohistochemistry:

  • Antigen retrieval optimization (citrate buffer pH 7.8, 0.1M for 24 minutes at approximately 82°C)

  • Blocking endogenous peroxidase activity (15 minutes at room temperature)

  • Overnight incubation with primary antibody at optimized concentration

  • Use positive control tissues with known expression (e.g., suprachiasmatic nucleus)

  • Recommended dilution: 1:100-1:500

• For immunofluorescence:

  • Membrane permeabilization optimization

  • Use of detergent-free fixation methods when possible

  • Minimizing autofluorescence through appropriate blocking

  • Recommended dilution: 1:50-1:200

• Validation strategies:

  • Comparison of protein and mRNA levels (noting potential discrepancies)

  • Use of overexpression systems as positive controls

  • Antibody validation using knockdown/knockout approaches

These optimized approaches can help overcome the technical challenges associated with GPR176 detection .

How does GPR176 contribute to circadian rhythm regulation and what experimental models best study this function?

GPR176 plays a crucial role in circadian rhythm regulation, particularly in the suprachiasmatic nucleus (SCN):

Key findings on GPR176 in circadian biology:

• Enriched expression in the SCN, the brain's circadian pacemaker

• Acts as a pace-setting factor for circadian behavior

• Functions independently of, and in parallel to, the Vipr2 GPCR pathway

• Represses cAMP signaling in an agonist-independent manner

• Operates through Gz rather than canonical Gi subunits

Optimal experimental models and approaches:

• Animal models:

  • Gpr176 knockout mice to study circadian behavioral changes

  • SCN-specific conditional knockout using Cre-loxP systems

  • Knockin models with mutations affecting constitutive activity or G-protein coupling

• Cellular models:

  • SCN slice cultures from wild-type and Gpr176 mutant mice

  • Primary SCN neuron cultures with GPR176 manipulation

  • Cell lines stably expressing circadian reporters (e.g., PER2::LUC) with GPR176 modulation

• Analytical techniques:

  • Real-time bioluminescence recording of circadian gene expression

  • Wheel-running activity monitoring for behavioral rhythms

  • In vivo microdialysis to measure cAMP fluctuations in the SCN

  • Single-cell calcium imaging to assess neuronal activity rhythms

• Molecular approaches:

  • Temporal profiling of GPR176 expression throughout the circadian cycle

  • ChIP-seq to identify transcriptional regulators of GPR176

  • RNA-seq to assess genome-wide effects of GPR176 manipulation on circadian gene expression

These approaches can help elucidate the specific mechanisms by which GPR176 contributes to the precision of the circadian clock .

How should I optimize immunohistochemistry protocols for GPR176 detection in different tissue types?

Successful detection of GPR176 by immunohistochemistry requires careful protocol optimization based on tissue type:

General protocol optimization:

• Fixation considerations:

  • Standard 4% paraformaldehyde fixation (24-48 hours) is generally suitable

  • Overfixation may mask epitopes, particularly for membrane proteins like GPR176

• Antigen retrieval optimization:

  • Heat-induced epitope retrieval using citrate buffer (pH 7.8, 0.1M) for 24 minutes at 82°C

  • Alternative: EDTA buffer (pH 9.0) if citrate buffer yields insufficient results

  • Optimization of retrieval time (15-30 minutes) based on tissue type

• Blocking optimization:

  • Endogenous peroxidase blocking (15 minutes at room temperature)

  • Additional blocking with 5-10% normal serum from the secondary antibody host species

  • Consider adding 0.1-0.3% Triton X-100 for improved antibody penetration

• Antibody incubation:

  • Primary antibody dilution: 1:100-1:500 based on antibody and tissue

  • Overnight incubation at 4°C for optimal sensitivity

  • Secondary detection: biotin-conjugated secondary antibody (10 minutes) followed by streptavidin peroxidase (5 minutes)

Tissue-specific considerations:

Scoring and interpretation:

• Evaluate both staining intensity and percentage of positive cells

• Document membrane vs. cytoplasmic localization

• Consider digital pathology quantification for objective assessment

These optimized protocols can improve the consistency and reliability of GPR176 detection across different tissue types .

What approaches can resolve discrepancies between GPR176 mRNA and protein expression levels?

Researchers have observed discrepancies between GPR176 mRNA and protein expression, particularly in cancer tissues. Understanding and addressing these discrepancies requires systematic approaches:

Observed discrepancies:

• In breast cancer, GPR176 mRNA levels were lower in cancer versus normal tissues, while protein levels showed the opposite pattern

• Various post-transcriptional and post-translational mechanisms may explain these differences

Systematic investigation approach:

• Comprehensive expression analysis:

  • Parallel assessment of mRNA (qRT-PCR, RNA-seq) and protein (WB, IHC) in the same samples

  • Use multiple primer pairs targeting different exons for mRNA detection

  • Use multiple antibodies targeting different epitopes for protein detection

• Post-transcriptional regulation assessment:

  • Analysis of microRNA targeting GPR176 mRNA

  • RNA stability assays using actinomycin D treatment

  • Polysome profiling to assess translational efficiency

• Post-translational modification analysis:

  • Evaluation of N-glycosylation status using PNGase F treatment

  • Phosphorylation analysis using phospho-specific antibodies or phosphoproteomics

  • Protein stability assessment using cycloheximide chase experiments

• Epigenetic regulation:

  • Analysis of DNA methylation status of the GPR176 promoter

  • Correlation between methylation status and expression levels

  • Histone modification profiling at the GPR176 locus

• Technical validation:

  • Multiple extraction methods for both RNA and protein

  • Inclusion of spike-in controls

  • Assessment of reference genes/proteins stability across samples

This multi-faceted approach can help elucidate the mechanisms behind observed discrepancies between GPR176 mRNA and protein levels, providing insights into its regulation in normal and pathological states .

How can I design effective knockdown or knockout studies to investigate GPR176 function?

Effective manipulation of GPR176 expression requires careful experimental design:

siRNA/shRNA knockdown approaches:

• Target sequence selection:

  • Design 3-4 independent siRNA sequences targeting different exons

  • Avoid sequences with potential off-target effects using algorithms like BLAST

  • Consider targeting regions with lower secondary structure for improved efficiency

• Knockdown validation:

  • qRT-PCR using primers spanning an exon-exon junction (recommended primers: 5′-AAGGTGTTCTGCTCGGTGAC′ (forward) and 5′-GAGGGTAGAGGACTGAATAGTACCTG-3′ (reverse))

  • Western blot using validated antibodies

  • Verify phenotypic effects with multiple independent siRNAs to rule out off-target effects

• Controls:

  • Non-targeting siRNA with similar GC content

  • Rescue experiments with siRNA-resistant GPR176 expression construct

CRISPR/Cas9 knockout strategies:

• gRNA design:

  • Target early exons to ensure functional knockout

  • Verify target sites are not in areas of known GPR176 polymorphisms

  • Design multiple gRNAs to increase efficiency

• Validation strategies:

  • Genomic PCR and sequencing to confirm mutations

  • Western blot to verify protein loss

  • Rescue experiments with wild-type GPR176 expression

• Special considerations:

  • For membrane proteins like GPR176, consider creating truncated proteins rather than complete knockouts

  • Create specific mutations targeting key functional domains (e.g., DRYxxV motif)

Functional readouts for GPR176 manipulation:

These approaches provide a comprehensive framework for investigating GPR176 function through genetic manipulation .

What considerations are important when selecting animal models for studying GPR176 function?

Selecting appropriate animal models for GPR176 research requires careful consideration of several factors:

Species conservation and expression patterns:

• Human and mouse GPR176 share significant homology, making mouse models generally suitable

• Expression patterns differ between species, with enrichment in the SCN confirmed in mice

• Verify expression in your tissue of interest before selecting a model

Available genetic models:

Cancer models incorporating GPR176 manipulation:

• Syngeneic models:

  • GPR176-overexpressing or knockout cancer cells implanted in immunocompetent mice

  • Suitable for studying immune interactions and microenvironment effects

• Xenograft models:

  • Human cancer cells with GPR176 manipulation in immunodeficient mice

  • Useful for studying direct effects on tumor growth and metastasis

• Genetic cancer models with GPR176 modification:

  • Crossing GPR176 knockout mice with genetic cancer models (e.g., APC^Min/+^ for intestinal tumors)

  • Provides insights into GPR176's role in cancer development and progression

Functional readouts by research area:

These considerations can guide the selection of appropriate animal models for investigating various aspects of GPR176 biology .

How can researchers integrate multi-omics approaches to comprehensively study GPR176 function?

A multi-omics approach provides the most comprehensive understanding of GPR176 function across biological contexts:

Integrated multi-omics framework:

• Genomics:

  • Analysis of GPR176 gene variants and their functional impacts

  • Identify potential regulatory elements through ATAC-seq

  • Evaluate copy number variations in cancer contexts

• Transcriptomics:

  • RNA-seq following GPR176 manipulation to identify downstream targets

  • Single-cell RNA-seq to identify cell populations expressing GPR176

  • Circadian profiling of GPR176 expression

  • Differential expression analysis between GPR176-high and -low tumors

• Proteomics:

  • Identification of GPR176 interaction partners through IP-MS

  • Analysis of proteome changes following GPR176 manipulation

  • PTM analysis focusing on glycosylation and phosphorylation

  • Spatial proteomics to determine subcellular localization

• Epigenomics:

  • Methylation analysis of the GPR176 promoter in normal and disease states

  • ChIP-seq to identify transcription factors regulating GPR176

  • Histone modification profiles at the GPR176 locus

• Metabolomics:

  • Metabolic changes in GPR176-manipulated systems

  • Focus on cAMP-related metabolic pathways

  • Circadian variation in metabolites related to GPR176 function

Data integration strategies:

• Computational integration:

  • Pathway enrichment analysis across multiple data types

  • Network analysis to identify functional modules

  • Machine learning approaches to identify GPR176-related signatures

• Experimental validation:

  • Target validation using CRISPR screens

  • Confirmation of key nodes in identified networks

  • Testing predicted drug sensitivities

Application examples in different research contexts:

These multi-omics approaches can provide a systems-level understanding of GPR176 function and identify new research directions and therapeutic opportunities .