Recombinant Mouse Neuropeptide Y receptor type 2 (Npy2r)

What is the primary function of NPY2R in physiological systems?

NPY2R functions primarily as a G protein-coupled receptor that mediates the effects of Neuropeptide Y (NPY), a 36-amino acid peptide neurotransmitter present in both central and peripheral nervous systems. In physiological contexts, NPY2R activation modulates several key signaling cascades including PI3K, MAPK, and NFAT pathways . The receptor is involved in the regulation of homeostatic functions such as eating behavior, anxiety responses, and reproduction . Research has demonstrated that NPY2R plays significant roles in kidney function, with its activation contributing to podocyte injury and albuminuria in various kidney disease models . Notably, the NPY-NPY2R signaling axis also participates in pain modulation via mechanisms in the amygdala, suggesting its importance in neurological functions beyond metabolic regulation .

How does NPY2R expression differ between healthy and disease states?

The expression pattern of NPY2R shows remarkable tissue-specific alterations in disease conditions. In kidney disease, local NPY production by podocytes decreases, contrasting with increased circulating NPY levels in the plasma and urine . This paradoxical expression pattern suggests complex regulatory mechanisms governing NPY-NPY2R signaling in disease states. In neuropathic pain conditions induced by chronic constriction injury (CCI) of the sciatic nerve, both NPY and NPY2R expression are aberrantly upregulated in the amygdala . This upregulation correlates with decreased mechanical withdrawal threshold and thermal withdrawal latency, indicating enhanced pain sensitivity. These differential expression patterns highlight the context-dependent nature of NPY2R regulation and function across different pathophysiological conditions.

What is known about the structural characteristics of mouse NPY2R?

Mouse NPY2R belongs to the G protein-coupled receptor superfamily, characterized by seven transmembrane domains. The C-terminus of mouse NPY2R contains the amino acid sequence CEQRLDAIHSEVSMTFKAK (residues 346-364), which is located intracellularly and serves as a key region for antibody recognition in experimental applications . The conserved seven transmembrane domains are essential for the receptor's functionality, as demonstrated in knockout studies where their loss resulted in complete functional ablation . The receptor shares structural homology with other NPY receptor subtypes (Y1, Y4, Y5), but displays distinct ligand binding properties and downstream signaling preferences that contribute to its unique physiological roles.

What are the most effective models for studying NPY2R function?

Several experimental models have proven valuable for investigating NPY2R function:

For kidney-related studies, adriamycin-induced nephropathy models in mice with NPY2R manipulation have proven particularly informative for understanding the receptor's role in albuminuria and podocyte injury . For neurological and behavioral studies, mirror tests and open-field assessments in NPY2R-deficient models provide valuable insights into anxiety and social behaviors . The choice of model should align with the specific research question, acknowledging that species differences may influence receptor function and signaling outcomes.

What techniques are recommended for measuring NPY2R expression and activity?

Multiple complementary techniques can be employed to comprehensively assess NPY2R expression and activity:

For protein detection:

• Western blot analysis using specific antibodies targeting the C-terminal region (amino acids 346-364) of mouse NPY2R has been successfully employed to detect the receptor in hippocampus and whole brain lysates .

• Immunohistochemistry and immunocytochemistry can visualize NPY2R localization in tissue sections (e.g., cerebellum) and primary cell cultures (e.g., dorsal root ganglion neurons) .

For gene expression analysis:

• Quantitative RT-PCR using NPY2R-specific primers allows sensitive detection of mRNA expression levels relative to housekeeping genes such as β-actin .

• RNA sequencing can provide comprehensive transcriptomic insights into NPY2R expression patterns and associated gene networks.

For functional assessment:

• High-resolution Tandem Mass Tagged (TMT)-based spectrometry can analyze proteome-wide changes following NPY-NPY2R signaling activation or blockade .

• Calcium imaging and electrophysiology techniques can measure immediate receptor activation responses.

• Behavioral assessments such as the mirror test and open-field test can evaluate anxiety and social behaviors in NPY2R-modified animal models .

How can I effectively generate and validate NPY2R knockout models?

Generating robust NPY2R knockout models requires careful design and comprehensive validation:

Generation strategies:

• CRISPR/Cas9 system has been successfully employed to create NPY2R-deficient models by targeting coding regions essential for receptor function. In medaka fish models, this approach generated a 297 bp deletion, 5 bp addition, and 1 bp mutation that resulted in premature termination of translation and complete loss of the seven transmembrane domains .

• For conditional knockouts, the Cre-loxP system targeting exons encoding critical transmembrane domains can provide tissue-specific NPY2R deletion when appropriate Cre driver lines are employed.

Validation approaches:

• Genotyping via PCR to confirm the presence of the intended genetic modification.

• mRNA quantification using qRT-PCR to verify reduced NPY2R transcript levels .

• Protein detection using Western blot and immunohistochemistry with NPY2R-specific antibodies to confirm absence of the receptor protein .

• Functional validation through expected phenotypic changes such as altered feeding behavior, anxiety responses, or specific pathway activation (e.g., MAPK signaling) .

• Control validations using blocking peptides in antibody-based detection methods to confirm specificity .

Comprehensive validation combining genetic, transcriptomic, proteomic, and functional assessments provides the strongest evidence for successful knockout generation.

How does NPY2R signaling contribute to kidney disease pathophysiology?

NPY2R signaling in kidney disease involves complex mechanisms that affect podocyte function and glomerular filtration:

The NPY-NPY2R signaling axis demonstrates a paradoxical pattern in kidney disease: local podocyte production of NPY decreases while circulating NPY levels increase . This imbalance appears to contribute to disease progression through several mechanisms:

• Signaling cascade activation: In the glomerulus, NPY signals via NPY2R to modulate PI3K, MAPK, and NFAT signaling pathways . Prolonged activation of these pathways is associated with podocyte injury.

• Proteomic alterations: Unbiased proteomic analysis revealed that glomerular NPY-NPY2R signaling predicts nephrotoxicity, modulates RNA processing, and inhibits cell migration . These changes likely contribute to podocyte dysfunction.

• Therapeutic potential: Pharmacological inhibition of NPY2R in vivo significantly reduced albuminuria in adriamycin-treated glomerulosclerotic mice, independent of blood pressure effects . This suggests that targeting NPY2R may offer protection against kidney disease progression.

• Structural preservation: NPY2R antagonism with BIIE0246 maintained podocyte foot process architecture in animal models, preserving the integrity of the glomerular filtration barrier .

These findings highlight NPY2R as a potential therapeutic target in albuminuric kidney diseases, with mechanistic insights suggesting that its inhibition may protect against podocyte injury and maintain filtration barrier integrity.

What is the role of NPY2R in neuropathic pain modulation?

NPY2R plays a significant role in pain processing and modulation through mechanisms centered in the amygdala:

Research using chronic constriction injury (CCI) models of the sciatic nerve has demonstrated that NPY2R in the amygdala contributes to neuropathic pain-like behaviors . The underlying mechanisms involve:

• Aberrant expression: Both NPY and NPY2R are upregulated in neuropathic pain-related conditions, particularly in the basolateral amygdala (BLA) .

• MAPK pathway activation: NPY2R activation stimulates the MAPK signaling pathway in the amygdala, a critical cascade in pain processing. Antagonism of this pathway restores normal pain thresholds as measured by mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) .

• Microglial regulation: NPY2R overexpression promotes microglial viability while inhibiting apoptosis, suggesting neuroimmune mechanisms may contribute to pain sensitization .

• Bidirectional central-peripheral signaling: The findings suggest that peripheral nerve injury leads to central adaptations in NPY-NPY2R signaling, which then contribute to persistent pain states through altered amygdala function.

These insights suggest that targeting NPY2R in the amygdala could offer a novel approach to managing neuropathic pain, particularly in cases where conventional analgesics provide inadequate relief.

How does NPY2R impact feeding behavior and metabolism?

NPY2R exerts significant influence on feeding behavior and metabolic regulation through multiple mechanisms:

Studies in NPY2R-deficient models have revealed pronounced effects on food intake and body composition:

• Increased food consumption: NPY2R knockout medaka exhibited significantly increased food intake compared to wild-type controls . This enhanced appetite may reflect removal of inhibitory signals normally mediated by NPY2R.

• Growth acceleration: NPY2R-deficient fish showed significantly increased total length and body weight compared to wild-type . This suggests that NPY2R normally serves as a brake on growth pathways.

• Species conservation of function: The finding that NPY2R knockout in medaka increases food intake parallels observations in mammalian models, suggesting evolutionary conservation of NPY2R's role in appetite regulation across vertebrates .

• Integration with other feeding circuits: NPY2R functions within a complex network of neuropeptides regulating food intake, including AgRP, POMC, and CCK. Studies examining expression changes in these factors following NPY2R manipulation provide insights into compensatory mechanisms .

• Relationship to anxiety: NPY2R's dual role in regulating both feeding and anxiety behaviors suggests these functions may be mechanistically linked, potentially through shared neural circuits .

These findings highlight NPY2R as a potential therapeutic target for metabolic disorders, though careful consideration of potential side effects on anxiety and social behaviors would be necessary for any interventional approach.

How do I resolve contradictory findings between central and peripheral NPY2R signaling?

Reconciling apparently contradictory findings regarding NPY2R signaling requires considering several key factors:

• Tissue-specific expression patterns: NPY2R may have opposite effects in different tissues. For example, in kidney disease, local NPY production by podocytes decreases while circulating NPY levels increase . This contrast suggests tissue-specific regulation that must be considered when interpreting results.

• Methodological differences in receptor activation:

  • Acute vs. chronic stimulation: Short-term (10-minute) NPY treatment produces different proteomic changes than long-term (24-hour) exposure .

  • Concentration dependence: Different NPY concentrations may preferentially activate different receptor subtypes or signaling pathways.

  • Ligand specificity: Studies using full-length NPY versus specific NPY2R agonists may yield different results due to cross-activation of other NPY receptor subtypes.

• Model system variables:

  • Species differences: While NPY2R function shows conservation across vertebrates, important differences exist between mammalian and non-mammalian models .

  • Genetic background: The impact of NPY2R manipulation may vary with the genetic background of the model organism.

  • Developmental timing: Constitutive versus inducible NPY2R knockout may produce different phenotypes due to developmental compensation.

• Contextual factors:

  • Physiological state: The impact of NPY2R signaling may differ between healthy and disease states.

  • Environmental conditions: Stress, feeding status, and other environmental factors may modify NPY2R signaling outcomes.

To resolve contradictions, researchers should carefully control for these variables and consider employing multiple complementary approaches (e.g., pharmacological and genetic) in multiple model systems to build a more complete understanding of NPY2R function.

What controls should be included in NPY2R functional studies?

Robust NPY2R functional studies require comprehensive controls to ensure valid interpretation:

Genetic model controls:

• Heterozygous comparisons: Include NPY2R+/- alongside NPY2R-/- and wild-type to assess gene dosage effects .

• Rescue experiments: Re-expression of NPY2R in knockout models should reverse phenotypes if they are directly related to receptor loss.

• Alternative knockout strategies: Using different targeting approaches (e.g., different CRISPR guide RNAs) helps confirm phenotypes are due to NPY2R loss rather than off-target effects.

Pharmacological controls:

• Multiple specific antagonists: Using structurally diverse NPY2R antagonists (e.g., BIIE0246) helps confirm receptor specificity .

• Dose-response relationships: Establish concentration-dependent effects to confirm specific receptor engagement.

• Receptor blocking peptides: These can serve as negative controls in antibody-based detection methods .

Analytical controls:

• Multiple detection methods: Combine RT-qPCR, Western blot, and immunostaining to confirm receptor expression changes .

• Housekeeping gene selection: Validate multiple reference genes (e.g., β-actin) for expression normalization .

• Statistical power: Ensure sufficient sample sizes based on power calculations to detect biologically meaningful differences.

Physiological controls:

• Body weight measurements: Monitor for changes that might indirectly impact experimental outcomes, especially in feeding studies .

• Blood pressure assessment: Rule out confounding cardiovascular effects in kidney-related studies .

• Behavioral baseline measures: Establish normal ranges for behavioral parameters in anxiety and sociability assessments .

Implementation of these comprehensive controls strengthens the validity and reproducibility of NPY2R functional studies and facilitates comparison across different experimental systems.

How can species differences in NPY2R function be reconciled in translational research?

Reconciling species differences in NPY2R function requires systematic comparative approaches:

Understanding evolutionary conservation:

• Sequence homology analysis: Compare NPY2R amino acid sequences across species to identify conserved functional domains versus divergent regions that might explain functional differences.

• Signaling pathway conservation: Determine whether downstream effectors (PI3K, MAPK, NFAT) are similarly engaged by NPY2R across species .

• Expression pattern mapping: Compare tissue distribution of NPY2R across species using comparable detection methods .

Methodological approaches:

• Parallel model systems: Study NPY2R function simultaneously in multiple species (e.g., mouse, zebrafish, medaka) using identical experimental paradigms .

• Humanized animal models: Generate mouse models expressing human NPY2R to directly assess functional differences.

• Cross-species pharmacology: Compare pharmacological profiles of NPY2R ligands across species to identify conserved binding mechanisms.

Data integration strategies:

• Molecular phenotyping: Use multi-omics approaches to characterize NPY2R signaling networks across species.

• Behavioral homology: Identify behaviors that represent functional equivalents across species despite different manifestations.

• Physiological endpoints: Focus on conserved physiological parameters (e.g., feeding regulation) rather than species-specific behaviors.

Translational considerations:

• Pathway focus: When direct receptor functions differ, concentrate on conserved downstream pathways as translational targets.

• Ligand development: Design NPY2R ligands targeting evolutionarily conserved binding domains to maximize cross-species applicability.

• Context specification: Clearly delineate which aspects of NPY2R function are species-specific versus broadly conserved when designing translational studies.

By systematically addressing these considerations, researchers can develop more effective translational frameworks for NPY2R research that appropriately account for species differences while leveraging functional conservation.

What is the therapeutic potential of targeting NPY2R in different disease conditions?

The therapeutic potential of NPY2R modulation spans multiple disease areas:

Kidney disease:

• NPY2R antagonism (e.g., with BIIE0246) significantly reduced albuminuria and preserved podocyte foot process architecture in adriamycin-induced nephropathy models .

• These protective effects occurred independently of blood pressure changes, suggesting direct renoprotective mechanisms .

• Future therapeutic development could focus on kidney-targeted NPY2R antagonists to minimize systemic effects.

Neuropathic pain:

• NPY2R in the amygdala contributes to pain sensitivity via MAPK pathway activation .

• Localized NPY2R antagonism in pain-processing brain regions represents a potential novel approach for treating neuropathic pain resistant to conventional analgesics.

• Combinatorial approaches targeting NPY2R alongside established pain pathways might offer synergistic benefits.

Metabolic disorders:

• NPY2R's role in feeding regulation suggests potential applications in obesity and metabolic syndrome .

• The complex relationship between NPY2R, food intake, and anxiety requires carefully balanced therapeutic approaches.

• Conditional or tissue-specific modulation might help separate beneficial metabolic effects from unwanted neuropsychiatric impacts.

Oncology applications:

• The high frequency and density of NPY receptors in steroid hormone-producing tumors suggests potential applications in tumor management .

• NPY2R-targeted imaging agents could improve tumor detection and monitoring.

• Cytotoxic payloads conjugated to NPY2R ligands might enable targeted tumor therapy.

As research progresses, therapeutic development will need to address challenges including receptor subtype selectivity, tissue-specific delivery, and management of effects across multiple physiological systems regulated by NPY2R.

How does NPY2R interact with other signaling systems in integrated physiological responses?

NPY2R functions within complex signaling networks that coordinate integrated physiological responses:

Neuroendocrine interactions:

• Glucocorticoid system: Studies have examined interactions between NPY2R and glucocorticoid receptors (GR1, GR2) and mineralocorticoid receptors (MR), suggesting coordinated stress and metabolic regulation .

• Serotonergic pathways: NPY2R interacts with tryptophan hydroxylase (TH1, TH2) expression, linking NPY signaling to serotonin production and mood regulation .

Feeding circuit integration:

• Appetite regulation network: NPY2R functions alongside other key regulators including AgRP, POMC, CCK, and NPY itself to form a coordinated feeding circuit .

• Counter-regulatory mechanisms: When NPY2R is deleted, compensatory changes in other appetite-regulating genes help maintain energy homeostasis.

Kidney signaling crosstalk:

• PI3K/MAPK/NFAT integration: NPY2R activation modulates these key signaling pathways that also respond to other renal regulatory factors, creating complex signaling nodes .

• Proteomic network effects: High-resolution proteomics has revealed that NPY-NPY2R signaling influences a broad array of proteins involved in RNA processing, cell migration, and nephrotoxicity responses .

Pain processing circuits:

• Amygdala microcircuits: NPY2R influences microglial viability and apoptosis, affecting neuroimmune interactions crucial for pain processing .

• MAPK pathway convergence: Multiple pain mediators converge on MAPK signaling, with NPY2R representing one regulatory input among many .

Understanding these complex interactions requires systems biology approaches that can map the full scope of NPY2R's influence across multiple signaling networks and physiological systems.

What emerging technologies are advancing NPY2R research?

Several cutting-edge technologies are transforming NPY2R research capabilities:

Genetic engineering advancements:

• CRISPR/Cas9 precision editing: Beyond simple knockouts, precision editing now enables subtle modifications of NPY2R regulatory elements and specific domains to dissect receptor function with unprecedented resolution .

• Cell-specific manipulation: Combinatorial approaches using Cre-driver lines with floxed NPY2R alleles allow investigation of receptor function in specific cell populations.

• Inducible systems: Temporally controlled NPY2R manipulation helps distinguish developmental versus acute receptor functions.

Advanced imaging techniques:

• GPCR conformational biosensors: These allow real-time visualization of NPY2R activation states in living cells.

• Tissue clearing methods: Technologies like CLARITY and iDISCO enable whole-organ imaging of NPY2R distribution across intact neural and renal tissues.

• Multiplexed receptor visualization: Methods to simultaneously image multiple receptor types reveal how NPY2R spatially interacts with other signaling components.

High-dimensional analytical methods:

• Single-cell transcriptomics: This reveals cell-specific NPY2R expression patterns and responses across heterogeneous tissues.

• High-resolution mass spectrometry: Tandem Mass Tagged (TMT)-based proteomics enables comprehensive analysis of NPY2R-mediated protein changes .

• Spatial transcriptomics: These techniques map NPY2R expression with spatial context in complex tissues.

Pharmacological innovations:

• Biased ligand development: Creation of ligands that selectively activate specific NPY2R signaling pathways while avoiding others.

• PET ligands for NPY2R: Development of positron emission tomography tracers allows in vivo imaging of receptor distribution and occupancy.

• Targeted nanoparticle delivery: These systems enable tissue-specific delivery of NPY2R modulators.