Recombinant Macaca mulatta Neuropeptide Y receptor type 2 (NPY2R)

What is NPY2R and what are its primary physiological functions?

Neuropeptide Y receptor type 2 (NPY2R) is a G protein-coupled receptor that belongs to the NPY receptor family, which includes five subtypes (Y1, Y2, Y4, Y5, and Y6) in mammals, with four (Y1, Y2, Y4, and Y5) expressed in humans . NPY2R functions as a receptor for neuropeptide Y (NPY) and peptide YY, playing crucial roles in multiple physiological processes across different organ systems . In the central nervous system, NPY2R is involved in the regulation of anxiety, feeding behavior, energy balance, and circadian rhythm control, making it a significant target for neurological and metabolic research . Recent studies have also identified its role in memory processes, particularly in controlling memory extinction by acting on physically non-overlapping neuronal sub-ensembles . In the peripheral system, NPY2R has been implicated in renal function, where it participates in glomerular filtration and podocyte responses at the filtration barrier . NPY2R's diverse physiological roles make it an important target for understanding multiple pathological conditions including obesity, diabetes, anxiety disorders, and kidney disease .

Where is NPY2R primarily expressed in primates and how does this compare to other species?

In primates, including Macaca mulatta, NPY2R expression follows patterns somewhat similar to those observed in other mammals, with notable expression in both central and peripheral nervous systems . Within the central nervous system, NPY2R is prominently expressed in the hippocampus, a region critical for learning and memory formation, as demonstrated by studies in rat models where significant expression was detected in hippocampal tissue . Comparative studies between primate and rodent models reveal that NPY2R is also expressed in the cerebellum, particularly in Purkinje cells, which are responsible for motor coordination and certain cognitive functions . In the peripheral nervous system, NPY2R expression has been detected in dorsal root ganglion neurons, suggesting its involvement in sensory processing and nociception . Importantly, NPY2R is expressed in renal tissue, specifically in podocytes within the glomerulus, indicating its role in kidney function and potentially in the pathophysiology of kidney diseases . These expression patterns show some conservation across mammalian species, though the regulatory mechanisms and functional implications may vary between primates and other experimental models like rodents or teleost fish, where distinct receptor gene deletions have been observed .

How does NPY2R signal transduction work and what pathways does it activate?

NPY2R signal transduction follows the classical G protein-coupled receptor mechanism, wherein ligand binding induces conformational changes that activate associated G proteins and trigger downstream signaling cascades . When NPY binds to NPY2R in the glomerulus, it activates multiple signaling pathways including PI3K (phosphoinositide 3-kinase), MAPK (mitogen-activated protein kinase), and NFAT (nuclear factor of activated T-cells) signaling cascades, all of which are critical for cell function and adaptation to external stimuli . The activation of these pathways by NPY-NPY2R interactions modulates RNA processing mechanisms and inhibits cell migration, which could have significant implications for cellular homeostasis and disease pathogenesis . Prolonged NPY-NPY2R signaling has been predicted to cause nephrotoxicity, highlighting the importance of precise temporal regulation of this signaling axis . In neuronal contexts, NPY2R signaling affects memory processes through sophisticated mechanisms involving neuronal ensembles, where it appears to sequentially activate NPY2R and NPY1R to control memory extinction processes . This bidirectional control suggests that NPY2R signaling works in concert with other NPY receptor subtypes to fine-tune complex physiological responses . The distinct spatial and temporal patterns of NPY2R signaling enable it to precisely regulate diverse functions across multiple organ systems, explaining its involvement in conditions ranging from anxiety and feeding disorders to kidney disease .

What are the optimal methods for detecting and quantifying NPY2R expression in tissue samples?

Multiple complementary approaches can be employed for detecting and quantifying NPY2R expression in tissue samples, each with specific advantages depending on the research question . Immunohistochemistry (IHC) represents a powerful method for visualizing NPY2R distribution within tissues, as demonstrated in rat cerebellum where NPY2R was detected in Purkinje cells using specific antibodies . For optimal results, tissues should be properly fixed (paraformaldehyde fixation is commonly used), sectioned (frozen sections work well), and stained with validated anti-NPY2R antibodies at appropriate dilutions (1:100 has been successfully employed) . Counterstaining with DAPI provides valuable context by visualizing nuclei within the tissue architecture . For cultured cells, immunocytochemistry follows similar principles, as shown in rat dorsal root ganglion neurons where NPY2R was visualized using anti-NPY2R antibody (1:100) followed by fluorescently-labeled secondary antibodies . Western blot analysis provides a complementary approach for quantifying NPY2R protein levels, as demonstrated with rat hippocampus and whole brain lysates, typically using 1:200 antibody dilutions . To ensure specificity of detection, appropriate controls are essential, including preincubation of antibodies with blocking peptides to confirm signal specificity . For mRNA-level quantification, RT-PCR or RNA sequencing can be employed to assess transcript levels, which is particularly valuable when studying expression changes in disease models or following experimental manipulations .

How can researchers effectively validate NPY2R antibodies for experimental applications?

Rigorous validation of NPY2R antibodies is essential for generating reliable research data, requiring a multifaceted approach that employs several complementary methods . Western blot analysis represents a fundamental validation step, where researchers should observe bands of the expected molecular weight in tissues known to express NPY2R, such as hippocampus and whole brain lysates, as demonstrated in rat models . Importantly, antibody specificity must be confirmed by including appropriate negative controls, such as preincubation with specific blocking peptides (e.g., NPY2R Blocking Peptide #BLP-NR022), which should abolish the specific signal if the antibody is truly targeting NPY2R . Immunohistochemistry in tissues with established NPY2R expression patterns, such as cerebellum (particularly Purkinje cells) and dorsal root ganglion neurons, provides additional validation of antibody performance in spatial localization studies . For comprehensive validation, researchers should ideally compare results across multiple antibodies targeting different epitopes of NPY2R, and if possible, include knockout/knockdown models as gold-standard negative controls . When validating antibodies for specific applications, researchers should optimize conditions (antibody concentration, incubation times, blocking agents, detection methods) for each technique separately, as conditions that work for Western blotting (e.g., 1:200 dilution) may differ from those optimal for immunohistochemistry (e.g., 1:100 dilution) . Cross-reactivity with related receptors (other NPY receptor subtypes) should also be assessed, particularly in systems where multiple receptor types are expressed simultaneously .

What considerations are important when designing experiments with recombinant NPY2R proteins?

When designing experiments with recombinant NPY2R proteins, researchers must address several critical considerations to ensure valid and reproducible results . First, the choice of protein construct is paramount—researchers must decide whether to use full-length receptor or specific domains (such as the 1-51 amino acid fragment), considering that truncated versions may not recapitulate all functional aspects of the native receptor . The presence and position of fusion tags (His, SUMO, Myc) must be carefully considered, as these can affect protein folding, stability, and functionality; ideally, control experiments with differently tagged versions or tag-cleaved proteins should be conducted to rule out tag-specific artifacts . Storage and handling conditions significantly impact experimental outcomes—researchers should avoid repeated freeze-thaw cycles, maintain appropriate buffer conditions (such as Tris-based buffer with 50% glycerol), and consider protein stability (shelf life of liquid form is typically 6 months at -20°C/-80°C, while lyophilized form can be stable for 12 months) . For functional studies, it's essential to establish appropriate ligand concentrations that reflect physiologically relevant conditions, particularly when studying NPY-NPY2R interactions . When using recombinant proteins to study signaling pathways (PI3K, MAPK, NFAT), researchers should include positive and negative controls to ensure specificity of observed effects . Finally, species differences must be considered—while recombinant proteins from different species (mouse, human, Macaca mulatta) share functional similarities, there may be subtle differences in ligand affinity, signaling efficiency, or regulatory mechanisms that could impact experimental outcomes and interpretation .

How does NPY-NPY2R signaling contribute to kidney disease pathophysiology?

NPY-NPY2R signaling plays a complex and previously underappreciated role in kidney disease pathophysiology, with recent research revealing its involvement in albuminuric kidney disease . Studies have demonstrated that NPY is produced by podocytes in the glomerulus, but this production decreases in renal disease, contrasting with the increase in circulating NPY levels observed in such conditions . This paradoxical expression pattern suggests a sophisticated regulatory mechanism wherein local and systemic NPY might play different roles in kidney homeostasis and disease progression . In the glomerulus, NPY signals through NPY2R to modulate crucial signaling pathways including PI3K, MAPK, and NFAT, which collectively regulate podocyte function and integrity . Prolonged activation of these pathways by NPY-NPY2R signaling is predicted to cause nephrotoxicity, suggesting a potential pathogenic mechanism in kidney disease . Importantly, NPY-NPY2R signaling also affects RNA processing and inhibits cell migration, processes that are essential for proper podocyte function and response to injury . The pathophysiological significance of this signaling axis is highlighted by in vivo studies showing that NPY deficiency surprisingly reduced albuminuria and podocyte injury in both diabetic and non-diabetic kidney disease models . Furthermore, pharmacological inhibition of NPY-NPY2R signaling protected against albuminuria and kidney disease in a mouse model of glomerulosclerosis, presenting a potential therapeutic approach for preventing kidney disease progression . These findings establish NPY-NPY2R signaling as a novel target for intervention in albuminuric kidney diseases, particularly in conditions associated with elevated systemic NPY levels such as obesity, diabetes, hypertension, and chronic kidney disease .

What role does NPY2R play in neuronal memory processes and extinction learning?

NPY2R plays a sophisticated role in neuronal memory processes, particularly in memory extinction, functioning as part of a complex system that balances memory stability with adaptability . Recent research has revealed that NPY, released by specific interneurons, acts through NPY2R to regulate memory lability and extinction through a process described as "peptide tagging" of engram cells . During extinction learning, NPY release increases significantly in response to conditioned stimuli, particularly as the extinction process progresses and fear responses diminish, suggesting a direct correlation between NPY signaling and extinction learning . Interestingly, NPY release demonstrates a dynamic pattern that ramps up during extinction learning while inversely correlating with freezing behavior—decreasing during freezing ON epochs and increasing during freezing OFF periods . Mechanistically, NPY appears to sequentially activate two physically non-overlapping neuronal sub-ensembles through NPY2R and NPY1R, allowing for precise temporal control over different stages of extinction . CRISPR/Cas9-mediated knockout studies have further elucidated that NPY2R specifically gates early fast stages of extinction, while NPY1R influences late slow stages, revealing a sophisticated temporal organization of the extinction process . This bidirectional control mechanism exemplifies how peptidergic inhibitions from GABAergic interneurons can fine-tune the balance between memory lability and stability, providing important insights into potential therapeutic approaches for conditions characterized by maladaptive memory processes, such as post-traumatic stress disorder or phobias . The complex spatiotemporal orchestration of NPY-NPY2R signaling in memory circuitry highlights the sophisticated nature of neuromodulatory systems in cognitive processes .

What are the emerging therapeutic applications targeting NPY-NPY2R interactions?

Emerging therapeutic applications targeting NPY-NPY2R interactions span multiple disease areas, with particularly promising developments in kidney disease, neuropsychiatric disorders, and metabolic conditions . In kidney disease, pharmacological inhibition of NPY-NPY2R signaling has demonstrated protective effects against albuminuria and disease progression in mouse models of glomerulosclerosis, suggesting potential therapeutic benefits for preventing kidney disease in high-risk populations . This approach may be particularly valuable for patients with conditions associated with elevated systemic NPY levels, such as obesity, diabetes, hypertension, and chronic kidney disease . In the neuropsychiatric domain, the role of NPY2R in memory extinction processes presents intriguing opportunities for treating conditions characterized by maladaptive memory persistence, such as post-traumatic stress disorder, phobias, and addiction . By targeting NPY2R to facilitate extinction learning, it may be possible to develop novel approaches for enhancing exposure therapy outcomes in these conditions . For anxiety disorders, NPY2R modulators could potentially address the altered anxiety-like behaviors observed in animal models, though translation to human applications requires careful consideration of species differences . In metabolic disorders, the involvement of NPY-NPY2R signaling in feeding regulation and energy balance suggests potential applications in obesity and diabetes management, though these would need to balance effects on multiple physiological systems . The development of these therapeutic applications faces significant challenges, including the need for receptor subtype selectivity to avoid unwanted effects through other NPY receptors, appropriate tissue targeting to minimize systemic effects, and consideration of potential compensatory mechanisms that might emerge with chronic receptor modulation .

What controls should be included when studying NPY2R function in different species?

Robust experimental design for studying NPY2R function across species requires thoughtfully selected controls that address biological variability, technical artifacts, and species-specific differences . For protein expression studies, researchers should include both positive controls (tissues known to express NPY2R, such as hippocampus and cerebellum) and negative controls (tissues with minimal NPY2R expression or samples from NPY2R knockout animals when available) . When utilizing antibody-based detection methods, specificity controls are essential—preincubation with specific blocking peptides should eliminate signal in Western blot and immunohistochemistry applications, confirming the specificity of the observed patterns . For functional studies of NPY-NPY2R signaling, appropriate ligand controls are crucial, including dose-response curves to establish optimal concentrations and comparison with other NPY receptor ligands to confirm receptor subtype specificity . When comparing NPY2R function across species (e.g., between Macaca mulatta and mouse or rat models), researchers should account for potential differences in receptor sequence, expression patterns, and downstream signaling pathways that might influence experimental outcomes . In genetic manipulation studies (knockout, knockdown, or CRISPR-Cas9 editing), appropriate wild-type and heterozygous controls should be included to establish gene-dose effects, as demonstrated in npy2r-deficient medaka studies . For behavioral experiments investigating NPY2R function, carefully matched control groups and standardized testing conditions are essential to minimize variability and enable valid cross-species comparisons . Finally, when studying NPY2R in disease models, both age-matched healthy controls and disease models with intact NPY2R function should be included to distinguish receptor-specific effects from general disease mechanisms .

How can researchers address species differences when studying recombinant NPY2R proteins?

Addressing species differences when studying recombinant NPY2R proteins requires a multi-faceted approach that combines comparative analysis with appropriate experimental controls and interpretative caution . Researchers should begin by conducting detailed sequence alignments between NPY2R from different species (human, non-human primates, rodents, fish) to identify conserved domains likely responsible for core functions versus divergent regions that might confer species-specific properties . When designing recombinant constructs, considering these alignment results can help determine whether to use full-length receptors or focus on highly conserved functional domains that may better represent cross-species properties . Parallel experiments using recombinant NPY2R from multiple species (e.g., Macaca mulatta, human, and mouse) under identical conditions can directly reveal functional differences in ligand binding, signaling efficiency, or regulatory responses . For ligand-receptor interaction studies, researchers should conduct comparative binding assays with ligands from different species to assess potential differences in affinity or specificity that might affect experimental outcomes . When translating findings between species, heterologous expression systems can help isolate receptor-specific effects from cellular context—expressing Macaca mulatta NPY2R in both primate and non-primate cell lines can reveal how cellular environment influences receptor function . Advanced methodologies such as site-directed mutagenesis can pinpoint specific amino acid residues responsible for species differences in receptor function, allowing for the creation of chimeric receptors or point mutants that help elucidate the molecular basis of functional divergence . Finally, researchers should exercise caution when extrapolating findings across species, particularly for complex phenotypes like reproductive development, where NPY2R deficiency in fish led to all-male offspring—a phenotype that may not translate to mammalian systems due to fundamental differences in sex determination mechanisms .

What approaches can resolve contradictory findings in NPY2R research?

Resolving contradictory findings in NPY2R research requires systematic investigation that addresses methodological differences, biological variability, and contextual factors that might explain divergent results . Researchers should first conduct detailed methodological comparisons between contradictory studies, examining differences in experimental models (cell lines, animal strains, species), protein constructs (full-length vs. truncated, tag positions), and analytical approaches that might account for discrepancies . Meta-analysis of existing literature can help identify patterns in contradictory findings, revealing whether inconsistencies correlate with specific methodological choices or experimental conditions . Independent replication by multiple laboratories using standardized protocols represents a gold-standard approach for resolving contradictions, particularly when accompanied by detailed reporting of all experimental parameters to ensure reproducibility . For mechanistic contradictions, researchers should consider the possibility that NPY-NPY2R signaling has context-dependent effects—the seemingly paradoxical findings that NPY production decreases in diseased kidneys while circulating levels increase highlights how local versus systemic effects might differ substantially . Temporal dynamics may also explain contradictions, as demonstrated by the sequential activation of NPY2R and NPY1R in memory extinction, where studying different time points might yield apparently conflicting results regarding receptor roles . Advanced approaches such as CRISPR/Cas9-mediated receptor knockout in various model systems can provide definitive evidence regarding receptor function, helping to resolve contradictions arising from less specific pharmacological or antibody-based approaches . Finally, contradictions might reflect genuine biological complexity rather than experimental artifacts—the bidirectional control of memory processes by NPY-NPY2R signaling exemplifies how seemingly contradictory findings (promoting both stability and lability) can be reconciled through deeper mechanistic understanding .

What are the key considerations for knockout/knockdown studies of NPY2R?

Knockout/knockdown studies of NPY2R require careful consideration of multiple factors to generate valid, interpretable results that advance our understanding of receptor function . The choice of genetic modification approach is fundamental—CRISPR/Cas9 systems have been successfully employed for NPY2R knockout in various models, offering advantages in terms of specificity and efficiency compared to older techniques . Researchers must decide between global knockout approaches (affecting all tissues) versus conditional or tissue-specific modifications that can help distinguish primary from secondary effects and avoid developmental compensation . The selection of appropriate model organisms is crucial—while medaka fish provided valuable insights into npy2r function, the observation that knockout resulted in all-male offspring highlights potential species-specific roles that might not translate directly to mammalian systems . Verification of knockout/knockdown efficiency through multiple complementary methods (genomic sequencing, RT-PCR, Western blotting, immunohistochemistry) is essential to confirm successful modification and rule out residual expression that might confound results . Researchers must also consider potential compensatory mechanisms that might emerge following NPY2R deletion, such as upregulation of other NPY receptor subtypes or alternative signaling pathways that could mask phenotypes or create secondary effects . When interpreting results, careful phenotypic characterization across multiple domains (molecular, cellular, physiological, behavioral) can provide comprehensive insights into receptor function while accounting for potential pleiotropy . Finally, appropriate controls are indispensable—heterozygous models can reveal gene dosage effects, as demonstrated in medaka where heterozygous npy2r+/- fish showed intermediate phenotypes in growth and behavior compared to wild-type and homozygous knockout animals . The application of these considerations can maximize the value of knockout/knockdown approaches in elucidating NPY2R function across diverse physiological contexts and species .