Recombinant Bovine Neuropeptide Y receptor type 2 (NPY2R)

What is Recombinant Bovine Neuropeptide Y Receptor Type 2 and how does it compare to human NPY2R?

Recombinant Bovine Neuropeptide Y Receptor Type 2 (NPY2R) is a member of the neuropeptide Y receptor family of G-protein coupled receptors expressed in cattle. Like its human counterpart, bovine NPY2R responds to endogenous peptide ligands including neuropeptide Y (NPY) and peptide YY (PYY), particularly their truncated forms. The receptor plays essential roles in food intake regulation, bone formation, and mood regulation . While the human and bovine receptors share high sequence homology, species-specific differences may exist in binding affinity and downstream signaling pathways.

The NPY2R structure features the canonical seven-transmembrane helical bundle architecture characteristic of G protein-coupled receptors. The receptor's second extracellular loop (ECL2) adopts a β-hairpin conformation, which is stabilized by a conserved disulfide bond connecting helix III and ECL2 . This structural feature is likely conserved in bovine NPY2R and contributes to the stability of the extracellular domain involved in ligand recognition.

What expression systems are most effective for producing recombinant bovine NPY2R?

For successful expression of recombinant bovine NPY2R, researchers should consider several expression systems based on research objectives:

When expressing bovine NPY2R, researchers should consider incorporating modifications similar to those used for human Y2R structural studies. These include truncating C-terminal residues (comparable to S354-V381 in human Y2R) and introducing stabilizing mutations to improve protein yield, homogeneity, and stability . For crystallization studies, fusion partners such as T4 lysozyme or modified flavodoxin may facilitate crystal formation by providing additional crystal contacts.

What are the known selective ligands for NPY2R and how can they be used in bovine studies?

NPY2R interacts with several selective ligands that can be valuable tools in bovine receptor studies:

Agonists:

• Neuropeptide Y (endogenous, non-subtype selective)

• Neuropeptide Y fragment 13-36 (NPY2R selective agonist)

• Peptide YY (PYY)

• Peptide YY 3-36 fragment

Antagonists:

• BIIE-0246 (CAS# 246146-55-4)

• JNJ-31020028 (with resolved crystal structure in complex with human Y2R)

• JNJ 5207787 (CAS# 683746-68-1)

• SF 11 (CAS# 443292-81-7)

When designing studies with bovine NPY2R, researchers should first confirm ligand binding affinities as they may differ from human Y2R. Competitive binding assays using radiolabeled NPY or PYY can establish the pharmacological profile of the bovine receptor. For functional studies, Y2R activation typically inhibits adenylyl cyclase, decreasing intracellular cAMP levels, which can be measured using FRET-based sensors or other cAMP detection methods .

What methodologies are recommended for characterizing NPY2R signaling in bovine systems?

To characterize bovine NPY2R signaling, researchers should implement multiple complementary approaches:

• cAMP Assays: Since NPY2R couples to Gαi proteins, its activation inhibits adenylyl cyclase. Measure decreased cAMP levels using FRET-based sensors or competitive immunoassays. To improve sensitivity, cells are typically pre-treated with forskolin to elevate cAMP levels before agonist addition .

• Calcium Mobilization: Y2R activation can modulate calcium signaling in some contexts. Monitor intracellular calcium using fluorescent indicators like Fura-2 or genetically encoded calcium indicators.

• Receptor Internalization: Track receptor trafficking using fluorescently-tagged receptor constructs or antibodies against epitope-tagged receptors.

• Electrophysiology: In neuronal preparations, Y2R activation modulates ion channel activity and neurotransmitter release. Patch-clamp techniques can directly measure these effects.

• Proximity Ligation Assays: These can detect Y2R interactions with downstream signaling partners to map the signaling network.

NPY2R is known to inhibit glutamate release, which is the principal neuroexcitatory transmitter . This function can be assessed in bovine neuronal preparations using neurotransmitter release assays.

How do the binding modes of NPY peptides differ between NPY2R and other NPY receptor subtypes?

The NPY receptor family exhibits distinct peptide recognition patterns that influence receptor subtype selectivity. Structural and functional studies reveal important differences in how NPY2R interacts with peptide ligands compared to other NPY receptor subtypes:

NPY2R can bind N-terminally truncated forms of NPY and PYY with high affinity, unlike Y1R and Y4R which require the full-length N terminus for optimal agonist activity . This distinct recognition pattern is reflected in the binding pose of NPY in Y2R versus Y1R structures.

When bound to Y2R, the peptide N-terminus stacks on top of the C-terminal region of ECL2. In contrast, when bound to Y1R, the N-terminus of NPY shifts toward ECL3 and binds deeper within the helical bundle . Furthermore, the α-helix in the peptide C-terminal region rotates counterclockwise (from extracellular view) by approximately 45° and moves closer to the receptor N-terminus and ECL3 in the NPY-Y1R structure compared to the NPY-Y2R structure .

These structural distinctions explain why Y2R preferentially binds to NPY3-36 and PYY3-36, whereas Y1R requires intact N-terminal regions. When designing peptide-based ligands for bovine NPY2R, researchers should focus on optimizing interactions with the peptide C-terminus while considering that N-terminal truncations may be tolerated or even preferred.

What structural modifications can improve the stability and expression yield of recombinant bovine NPY2R for crystallography studies?

Based on successful structural studies with human Y2R, several strategic modifications can enhance bovine NPY2R stability and expression for crystallography:

• C-terminal Truncation: Removing the C-terminal portion (comparable to S354-V381 in human Y2R) can significantly improve expression and homogeneity without compromising ligand binding .

• Stabilizing Mutations: Consider introducing mutations analogous to H149³·⁵¹Y and S280⁶·⁴⁷C in human Y2R, which enhanced stability while preserving functionality . These positions correspond to conserved residues in the Ballesteros-Weinstein numbering system, facilitating identification of equivalent residues in bovine NPY2R.

• Fusion Partners: Crystallization can be facilitated by fusing proteins such as modified T4 lysozyme to the N-terminus and replacing a portion of the third intracellular loop (ICL3) with modified flavodoxin .

• Thermostabilizing Mutations: Alanine scanning mutagenesis followed by thermal stability assays can identify additional stabilizing mutations specific to bovine NPY2R.

• Lipid Environment Optimization: Screening different lipids and detergents can identify conditions that maintain bovine NPY2R in a stable, homogeneous conformation.

Before crystallization trials, validate that these modifications preserve the pharmacological properties of the native receptor using ligand binding and functional assays . The modified receptor should maintain similar binding affinities for antagonists like JNJ-31020028 and comparable signaling responses.

What mutagenesis approaches have been most informative in identifying key residues involved in NPY2R function?

Strategic mutagenesis studies have revealed critical residues for NPY2R function, providing valuable insights for bovine receptor research:

The residue Y110²·⁶⁴ (Ballesteros-Weinstein numbering) has been identified as crucial for binding of the peptide agonist NPY. Mutation of this residue to alanine (Y110²·⁶⁴A) resulted in a 30-fold increase in EC₅₀ value for NPY (from 0.06 nM to 1.8 nM), confirming its importance in agonist binding . This mutation also reduced the antagonistic activity of JNJ-31020028 and BIIE0246 by sevenfold and fourfold, respectively, while having minimal impact on compound 6 .

The residue D292⁶·⁵⁹ has been suggested to be important for all NPY receptors in binding NPY through an ionic interaction with one of the two arginine residues at the peptide C-terminus . Mutation D292⁶·⁵⁹N showed a twofold reduction in antagonistic activity of BIIE0246 but did not significantly affect JNJ-31020028 activity, suggesting differential roles in antagonist binding .

When designing mutagenesis studies for bovine NPY2R, researchers should:

• Use alanine scanning of conserved residues in the binding pocket

• Create chimeric receptors swapping domains between bovine and human NPY2R

• Introduce species-specific residues from other NPY receptor subtypes to study selectivity determinants

• Employ charge-reversal mutations to identify electrostatic interactions

Functional consequences should be assessed through multiple assays including binding affinity, agonist potency, and antagonist inhibition to build a comprehensive picture of structure-function relationships.

How can contradictory data regarding NPY2R signaling in different tissue types be resolved?

Reconciling contradictory NPY2R signaling data across different tissues requires systematic experimental approaches:

• Tissue-Specific Expression Analysis:

  • Quantify NPY2R expression levels in different bovine tissues using qRT-PCR and Western blotting

  • Identify tissue-specific splice variants that may exhibit altered signaling properties

  • Map receptor distribution using immunohistochemistry with validated antibodies

• Signaling Partner Profiling:

  • Analyze expression patterns of G-proteins, arrestins, and other downstream effectors across tissues

  • Use co-immunoprecipitation or proximity ligation assays to identify tissue-specific protein-protein interactions

  • Employ phosphoproteomics to map tissue-specific signaling networks

• Contextual Activation Assessment:

  • Compare NPY2R signaling in primary cells versus cell lines

  • Evaluate receptor function in organotypic cultures that maintain tissue architecture

  • Develop tissue-specific conditional knockout models to assess context-dependent roles

• Technical Standardization:

  • Use consistent experimental conditions (temperature, buffer composition, cell density)

  • Apply multiple complementary assay formats to verify findings

  • Ensure physiologically relevant ligand concentrations

For example, studies have shown that Y2R-linked inhibition of noradrenaline release from hypothalamic synaptosomes is apparently not due to reduced Ca²⁺ influx , while inhibition of glutamate release from retinal presynaptic bipolar cells is connected to Y2R interaction with Ca²⁺ channels . These differences highlight tissue-specific signaling mechanisms that must be considered when designing experiments with bovine NPY2R.

What are the optimal experimental designs for studying NPY2R involvement in metabolic regulation and obesity?

To investigate bovine NPY2R in metabolic regulation, researchers should implement multi-level experimental approaches:

• In Vitro Models:

  • Primary bovine adipocytes to study direct effects on lipid metabolism

  • Hypothalamic neuronal cultures to assess feeding circuit regulation

  • Pancreatic islet preparations to examine insulin/glucagon secretion

  • Co-culture systems to study cell-cell communication

• Ex Vivo Tissue Preparations:

  • Perifused hypothalamic slices to measure neuropeptide release in response to Y2R modulation

  • Isolated intestinal segments to study PYY3-36 secretion and Y2R signaling

  • Adipose tissue explants to examine lipolysis and lipogenesis

• In Vivo Approaches:

  • Intracerebroventricular administration of selective Y2R agonists/antagonists with metabolic phenotyping

  • Tissue-specific NPY2R knockout/knockdown using CRISPR-Cas9 or RNAi

  • Metabolic clamp studies to assess insulin sensitivity and glucose metabolism

  • Combined PET-CT imaging to track tissue-specific metabolic activity

• Key Parameters to Measure:

  • Food intake patterns (meal frequency, size, duration)

  • Energy expenditure and respiratory quotient

  • Body composition (fat mass vs. lean mass)

  • Glucose tolerance and insulin sensitivity

  • Circulating hormones (insulin, glucagon, gut hormones)

  • Hypothalamic and peripheral gene expression profiles

Y2R plays essential roles in food intake and has been considered an important drug target for obesity . Understanding its function in bovine systems could provide valuable insights for veterinary medicine and comparative physiology. Researchers should carefully consider species differences in metabolic regulation when translating findings between bovine models and other species.

What considerations are important when developing selective antagonists for bovine NPY2R?

Developing selective antagonists for bovine NPY2R requires careful attention to several key factors:

• Species-Specific Binding Pocket Analysis:

  • Compare the binding pocket residues between bovine and human NPY2R

  • Identify unique residues that could be targeted for species selectivity

  • Model the bovine NPY2R structure based on the human Y2R crystal structure with JNJ-31020028

• Structure-Activity Relationship Studies:

  • Start with known Y2R antagonists like JNJ-31020028 and BIIE0246

  • Systematically modify chemical scaffolds to optimize binding to bovine NPY2R

  • Focus on the six functional groups of JNJ-31020028 (phenylethyl, diethyl amide, benzamide, pyridine, fluorophenyl, and piperazine moieties) as starting points for derivatization

• Selectivity Screening:

  • Test compounds against all NPY receptor subtypes (Y1R, Y2R, Y4R, Y5R)

  • Evaluate cross-species activity using human, mouse, and bovine receptors

  • Assess off-target activity against structurally related GPCRs

• Functional Characterization:

  • Determine antagonist mechanism (competitive, non-competitive, allosteric)

  • Measure antagonist potency using multiple functional assays (cAMP, Ca²⁺, β-arrestin recruitment)

  • Assess the impact of antagonists on receptor internalization and desensitization

The Y2R binding cavity formed by residues from the first extracellular loop (ECL1) and helices II-VII should be the primary target for antagonist design. Understanding how specific residues like Y110²·⁶⁴ and D292⁶·⁵⁹ contribute to antagonist binding will be crucial for developing compounds with optimal pharmacological properties for bovine NPY2R.

How might recent advances in GPCR structural biology accelerate NPY2R research?

Recent breakthroughs in GPCR structural biology offer unprecedented opportunities for advancing bovine NPY2R research:

• Cryo-Electron Microscopy (Cryo-EM): The revolution in cryo-EM technology now enables structure determination of GPCRs in complex with various signaling partners without crystallization. This approach could reveal the full-length bovine NPY2R structure in various activation states, capturing conformational dynamics that crystallography might miss .

• AlphaFold and Deep Learning Approaches: These computational methods can predict bovine NPY2R structures with high accuracy based on amino acid sequence, potentially identifying species-specific structural features before experimental confirmation.

• Lipid Nanodisc Technology: Reconstituting bovine NPY2R in lipid nanodiscs provides a native-like membrane environment, enabling structural and functional studies in conditions closer to physiological reality than detergent solubilization.

• Serial Femtosecond Crystallography: This technique can capture dynamic states of GPCRs using X-ray free-electron lasers, potentially revealing transient conformational states of bovine NPY2R during activation.

• Molecular Dynamics Simulations: These computational approaches can model the dynamic behavior of bovine NPY2R over time, predicting conformational changes induced by different ligands and identifying allosteric binding sites.

The crystal structure of human Y2R bound to JNJ-31020028 provides a valuable template for these advanced approaches. Future studies applying these technologies to bovine NPY2R will likely reveal species-specific features that could be exploited for selective therapeutic targeting in veterinary medicine.

What role might NPY2R play in bovine metabolic disorders and potential therapeutic applications?

Bovine NPY2R likely plays significant roles in metabolic regulation with important implications for veterinary medicine:

• Dairy Cattle Nutrition and Production:

  • NPY2R may regulate feed intake and energy balance in lactating cows

  • Selective modulation could potentially enhance milk production efficiency

  • Understanding Y2R function could help manage negative energy balance post-calving

• Obesity and Metabolic Syndrome in Cattle:

  • High-energy diets in feedlot cattle may dysregulate NPY2R signaling

  • Y2R agonists could potentially reduce excess adiposity in overfeeding scenarios

  • NPY2R polymorphisms might influence feed efficiency and weight gain

• Stress Response and Production Parameters:

  • NPY2R regulates mood and anxiety-like behaviors

  • Chronic stress may alter Y2R expression and function in cattle

  • Y2R modulators could potentially improve welfare and production in stressful environments

• Bone Formation and Health:

  • Y2R plays essential roles in bone formation

  • Selective targeting could potentially address bone disorders in high-producing dairy cattle

  • Understanding Y2R in bovine bone metabolism could provide insights for managing lameness

• Comparative Physiology Insights:

  • Species differences in NPY2R function between bovines and humans

  • Unique aspects of ruminant metabolism mediated by NPY signaling

  • Evolutionary adaptations in the NPY system related to feeding patterns

The multifunctional nature of NPY2R in food intake, bone formation, and mood regulation makes it a promising target for addressing complex disorders in cattle. Future research should focus on tissue-specific roles of bovine NPY2R and how they integrate to maintain metabolic homeostasis in both healthy and pathological states.