Recombinant Gorilla gorilla gorilla Vomeronasal type-1 receptor 1 (VN1R1)

What is VN1R1 and what is its primary function in mammals?

VN1R1 (Vomeronasal type-1 receptor 1) is a G-protein coupled receptor (GPCR) that functions as a pheromone receptor. In most mammals, it mediates the detection of chemical signals that regulate social and reproductive behaviors . Traditionally, vomeronasal receptors were thought to be exclusively expressed in the vomeronasal organ (VNO), but research has shown that in humans, VN1R1 is primarily localized to the olfactory mucosa rather than the VNO . While many mammals have numerous functional vomeronasal receptors, humans have only five (VN1R1-5), with VN1R1 being the most extensively studied . The protein functions by binding specific chemical ligands, which initiates a signal transduction cascade that ultimately affects behavior and physiological responses related to social interactions .

What is the amino acid sequence and structure of Gorilla gorilla gorilla VN1R1?

The full-length Gorilla gorilla gorilla VN1R1 protein consists of 353 amino acids. The sequence is as follows:

MVGDTLKLLSPLMTRYFFLLFYSTDSSDLNENQHPLDFDEMAFGKVKSGISFLIQTGVGILGNSFLLCFYNLILFTGHKLRPTDLILSHLALANSMVLFFKGIPQTMAAFGLKYLLNDTGCKFVFYYHRVGTRVSLSTICLLNGFQAIKLNPSICRWMEIKIRSPRFIDFCCLLCWVPHVLMNASVLLLVNGPLNSKNSSAKNNYGYCSYKASKRFSSLHAVLYFSPDFMSLGFMVWASGSMVFFLYRHKQQVQHNHSNRLSCRPSQETRATRTIMVLVSSFFVFYSVHSFLTIWTTVVANPGQWIVNNSVLVASYFPSRSPFVLIMSDTRISQFCFACRTRKTLFPNLVVMP

Structurally, VN1R1 follows the typical GPCR architecture with seven transmembrane domains. The protein contains several functional regions important for ligand binding and signal transduction. While a high-resolution three-dimensional structure has not yet been definitively determined, computational modeling suggests that the protein forms a pocket-like structure capable of recognizing specific pheromone molecules .

How does Gorilla gorilla gorilla VN1R1 compare to human VN1R1?

Both gorilla and human VN1R1 share considerable sequence homology, reflecting their recent evolutionary divergence. Both proteins are full-length 353 amino acid receptors . The human VN1R1 gene contains two nonsynonymous single-nucleotide polymorphisms (rs61744949 and rs28649880) that are in complete linkage disequilibrium . These polymorphisms result in an alanine to aspartic acid substitution at position 229 (A229D), which may affect protein conformation and function .

Research has demonstrated that human VN1R1 can be activated by specific ligands, including the monoterpene myrtenal and the synthetic agonist Hedione, suggesting functional activity despite evolutionary changes . While gorilla VN1R1 is presumed to maintain its ancestral function in pheromone detection, detailed comparative functional studies between gorilla and human VN1R1 remain limited in the current literature.

What experimental systems are appropriate for studying recombinant VN1R1 function?

Several experimental systems have been validated for studying VN1R1 function:

• Heterologous Expression Systems: Human embryonic kidney (HEK293) cells provide an established platform for expressing recombinant VN1R1 proteins . These cell lines can be transfected with VN1R1-encoding vectors to produce functional receptors for biochemical and pharmacological studies.

• E. coli Expression Systems: For producing recombinant proteins in larger quantities, E. coli expression systems have been effectively used to generate His-tagged VN1R1 proteins from both human and gorilla sources .

• Cell Lysate Preparations: For studying receptor interactions with potential binding partners, cell lysate preparations containing VN1R1 can be utilized as seen with the Human VN1R1 293 Cell Lysate approach .

• Calcium Imaging Assays: Since VN1R1 signaling typically involves calcium mobilization, calcium imaging techniques can be employed to measure receptor activation in response to potential ligands.

• Binding Assays: ELISA-based methods using recombinant VN1R1 can be used to screen for novel ligands and study binding kinetics .

When selecting an experimental system, researchers should consider the specific research question, required protein yield, need for post-translational modifications, and downstream applications.

What are the optimal storage and handling conditions for recombinant VN1R1 proteins?

Recombinant VN1R1 proteins require specific storage and handling conditions to maintain functionality:

• Storage Temperature: Store at -20°C for regular use, and at -80°C for extended storage to minimize protein degradation .

• Buffer Composition: Tris-based buffers with 50% glycerol have been optimized for VN1R1 stability .

• Freeze-Thaw Cycles: Repeated freezing and thawing should be avoided as this can lead to protein denaturation and loss of activity. Working aliquots should be prepared and stored at 4°C for up to one week .

• Protein Concentration: Typically, recombinant VN1R1 is supplied at concentrations around 50 μg per standard vial, though other quantities can be prepared for specific experimental needs .

• Handling Precautions: As with all recombinant proteins, VN1R1 should be handled with appropriate laboratory safety measures, including the use of gloves to prevent contamination.

How can researchers verify the functional activity of recombinant VN1R1?

Functional verification of recombinant VN1R1 can be achieved through several complementary approaches:

• Ligand Binding Assays: Using known ligands such as myrtenal or Hedione to confirm binding capacity. For human VN1R1, these compounds have been established as agonists .

• Signal Transduction Assays: Measuring downstream signaling events such as calcium flux, cAMP production, or ERK phosphorylation in response to ligand exposure.

• Receptor Internalization Studies: Monitoring receptor trafficking in response to ligand activation using fluorescently tagged receptors.

• Comparative Functional Assays: Testing wildtype versus polymorphic variants (e.g., A229D in human VN1R1) to assess functional differences that may correlate with behavioral phenotypes .

• Species-Comparative Approaches: Comparing response profiles between human and gorilla VN1R1 to identify conserved and divergent functional properties.

Each verification approach should include appropriate positive and negative controls, and results should be replicated across multiple experimental conditions to ensure reliability.

What polymorphisms exist in VN1R1 and how do they affect function?

In humans, VN1R1 contains notable polymorphic variations that appear to have functional consequences:

• A229D Substitution: The most well-characterized polymorphism in human VN1R1 involves an alanine to aspartic acid substitution at position 229 (encoded by SNPs rs61744949 and rs28649880, which are in complete linkage disequilibrium) . The D-allele frequency is approximately 37% in studied populations .

• Functional Impact: Research suggests this polymorphism may alter receptor conformation and function. In cell culture studies, the variants show differential responses to ligands, suggesting altered sensitivity or specificity.

• Behavioral Associations: In human studies, the D-allele has been associated with increased sociosexual behavior in women, particularly regarding one-night stands, and with decreased likelihood of being in a long-term relationship . This association was not observed in men, suggesting possible sex-specific effects .

• Hardy-Weinberg Equilibrium: Interestingly, genotype distribution for this polymorphism deviates from Hardy-Weinberg equilibrium in studied populations, with fewer heterozygotes than expected. This deviation was even more pronounced in women who had never had sex, suggesting possible selection pressures related to reproductive behavior .

For gorilla VN1R1, comprehensive studies on polymorphic variations are more limited in the available literature, representing a gap in current knowledge that merits further investigation.

How do VN1R1 polymorphisms correlate with behavioral phenotypes?

Research on human VN1R1 polymorphisms has revealed several significant behavioral correlations:

• Sociosexual Behavior: In women, the D-allele of the A229D polymorphism has been significantly associated with sociosexual behavior (p=0.0001), explaining approximately 1.2% of the variance in this behavior . This association was specifically driven by differences in the number of one-night stands (p=0.0004) .

• Relationship Status: Female carriers of the D-allele were less likely to be in a relationship (odds ratio=0.8, p=0.008), though no association was found with relationship duration or sex-related anxiety .

• Sex-Specific Effects: These associations were not observed in men, suggesting sex-specific effects of the polymorphism. The gene by sex interaction was statistically significant (p=0.001) .

• Reproductive Strategy: The association between VN1R1 polymorphism and sociosexual behavior remained significant after controlling for relationship status, relationship duration, and sex-related anxiety, suggesting an independent effect on reproductive strategy .

These findings suggest that despite the reduction in vomeronasal function during human evolution, variation in remaining vomeronasal receptors like VN1R1 may still influence human social and reproductive behavior, possibly through alternative signaling pathways or expression in the main olfactory epithelium.

What are the methodological challenges in studying VN1R1 across species?

Researchers studying VN1R1 across species face several methodological challenges:

To address these challenges, researchers often employ combinatorial approaches, including computational modeling, comparative genomics, and in vitro functional assays.

How does VN1R1 interact with other proteins in signaling pathways?

VN1R1 functions within complex signaling networks:

• G-Protein Coupling: As a GPCR, VN1R1 couples with G-proteins to transduce signals. In traditional vomeronasal signaling, this often involves Gαi2 proteins, though human VN1R1 may utilize alternative G-protein subtypes given its expression in the main olfactory epithelium .

• Downstream Effectors: Activation of VN1R1 leads to engagement of various downstream effectors, potentially including phospholipase C, resulting in IP3 production and calcium mobilization from intracellular stores.

• Interacting Proteins: While the search results don't specify direct protein interactions for gorilla VN1R1, the Creative BioMart database indicates that human VN1R1 has documented interactions with several proteins that could be investigated using techniques such as yeast two-hybrid assays, co-immunoprecipitation, and pull-down assays .

• Pathway Involvement: VN1R1 is involved in GPCR signaling pathways and may interact with proteins such as OR10A5, LGR6, GPR132, S1PR1, V1RA8, GPR183, EMR3, GPR84, VMN1R45, and PROKR2 in these pathways .

• Shared Functional Properties: VN1R1 shares pheromone receptor activity with proteins including VMN1R44, VMN1R46, VMN1R40, VMN1R52, VMN1R54, VMN1R49, VMN1R45, VMN1R47, V1RA8, and ORA1 .

Understanding these interactions is critical for elucidating the complete signaling mechanisms of VN1R1 and may reveal novel therapeutic targets or biological insights.

What are the evolutionary implications of VN1R1 conservation across primates?

The conservation of VN1R1 across primate species raises several important evolutionary questions:

• Functional Retention: Despite the reduction in vomeronasal system function in Old World monkeys, apes, and humans, VN1R1 remains conserved as a functional receptor, suggesting selective pressure to maintain its function .

• Expression Pattern Shifts: In humans, VN1R1 expression has shifted from the vestigial vomeronasal organ to the main olfactory epithelium, potentially indicating evolutionary repurposing of this receptor .

• Ligand Specificity Evolution: Differences in receptor structure across species may reflect adaptation to different ecologically relevant chemical signals, though specific ligands for gorilla VN1R1 remain to be characterized.

• Behavioral Correlates: The association between human VN1R1 polymorphisms and sociosexual behavior suggests that even in species with reduced vomeronasal function, these receptors may continue to influence socially relevant behaviors .

• Molecular Evolution Rates: Comparative analysis of VN1R1 sequences across primates could reveal variable rates of molecular evolution that correspond to ecological specializations or mating systems.

This evolutionary context provides a framework for understanding the functional significance of VN1R1 across species and may guide future comparative studies.

What are the optimal protocols for expressing recombinant gorilla VN1R1?

Based on the available information, several expression systems have been successfully used for recombinant VN1R1 production:

• E. coli Expression System: This system has been effectively used to produce His-tagged full-length gorilla VN1R1 protein (1-353 amino acids) . Key considerations include:

  • Use of appropriate expression vectors with strong promoters

  • Optimization of induction conditions (temperature, IPTG concentration)

  • Inclusion of a His-tag for purification purposes

  • Careful cell lysis and membrane protein solubilization

• Mammalian Expression Systems: For applications requiring mammalian post-translational modifications, HEK293 cells have been used successfully for human VN1R1 and likely would work for gorilla VN1R1 as well . Considerations include:

  • Codon optimization for mammalian expression

  • Selection of appropriate transfection methods

  • Creation of stable cell lines for consistent protein production

  • Proper membrane protein extraction protocols

• Purification Approaches: For His-tagged proteins, immobilized metal affinity chromatography (IMAC) is typically employed, followed by size exclusion chromatography to enhance purity.

• Quality Control: Verification of expression through Western blotting, mass spectrometry, and functional assays is essential to ensure the recombinant protein accurately represents native VN1R1.

The choice of expression system should align with the specific research objectives and downstream applications planned for the recombinant protein.

What experimental designs are appropriate for studying VN1R1 polymorphisms?

When investigating VN1R1 polymorphisms, several experimental approaches can be employed:

• Genotype-Phenotype Association Studies: Similar to the human studies that identified associations between the A229D polymorphism and sociosexual behavior, researchers can design studies examining correlations between VN1R1 variants and specific behavioral or physiological traits . Such studies require:

  • Clear phenotype definitions and measurement tools

  • Appropriate sample sizes for statistical power

  • Control for potential confounding variables

  • Replication in independent samples

• In Vitro Functional Comparisons: Different polymorphic variants can be expressed in cell systems to compare:

  • Ligand binding affinities

  • Signal transduction efficiency

  • Receptor internalization and trafficking

  • Protein stability and expression levels

• Structural Biology Approaches: Computational modeling or experimental structure determination can reveal how specific polymorphisms affect receptor conformation and function.

• Evolutionary Analyses: Comparing allele frequencies across populations and related species can provide insights into selective pressures acting on different VN1R1 variants.

• Transgenic Animal Models: While challenging and subject to ethical considerations, introducing specific VN1R1 variants into model organisms could help elucidate their functional effects in vivo.

Each approach has strengths and limitations, and combining multiple methods often provides the most comprehensive understanding of polymorphism effects.

How can researchers design experiments to identify novel ligands for gorilla VN1R1?

Identifying novel ligands for gorilla VN1R1 requires systematic screening approaches:

• High-Throughput Screening: Using recombinant VN1R1 expressed in appropriate cellular systems, researchers can screen chemical libraries for compounds that activate the receptor. Detection methods may include:

  • Calcium imaging assays

  • Reporter gene assays (e.g., luciferase linked to signaling pathway activation)

  • BRET/FRET-based interaction assays

  • Electrophysiological measurements

• Candidate Compound Approach: Testing compounds known to activate VN1R1 in humans or other species (e.g., myrtenal, Hedione) on gorilla VN1R1 to assess conserved activation patterns .

• Computational Docking Studies: Using homology models of gorilla VN1R1 to virtually screen compound libraries for potential ligands based on predicted binding energies and interactions.

• Ecological Chemistry Approaches: Analyzing chemical compounds present in gorilla social environments, secretions, or excretions to identify ecologically relevant candidate ligands.

• Comparative Pharmacology: Systematic comparison of response profiles between gorilla and human VN1R1 to identify species-specific and conserved ligand preferences.

• Structure-Activity Relationship Studies: Once preliminary ligands are identified, testing structural analogs to determine key molecular features required for receptor activation.

These approaches should ideally be combined in an iterative process, with initial hits being validated through secondary assays and structure-activity studies.

What are the promising future directions for VN1R1 research?

Several emerging research directions hold promise for advancing our understanding of VN1R1:

• Comparative Functional Genomics: Systematic comparison of VN1R1 structure, expression, and function across primate species could reveal evolutionary patterns and functional adaptations related to social organization and mating systems.

• Advanced Structural Biology: Application of cryo-electron microscopy and other advanced structural techniques to determine high-resolution structures of VN1R1, potentially in complex with ligands.

• Chemosensory Communication in Great Apes: Investigation of potential chemical communication mediated by VN1R1 in gorillas and other great apes in their natural environments, which remains poorly understood.

• Expanded Human Polymorphism Studies: Building on the sociosexual behavior associations found in existing studies, future research could explore whether VN1R1 polymorphisms influence other aspects of human social behavior or perception.

• Therapeutic Applications: Given the association with social behavior, exploring whether VN1R1 modulators might have potential applications in conditions involving social dysfunction.

• Integration with Neuroimaging: Combining genotyping for VN1R1 polymorphisms with neuroimaging studies to understand how genetic variation influences neural processing of social and chemical signals.

These directions represent opportunities to deepen our understanding of this fascinating receptor system and its role in primate evolution and behavior.

How might CRISPR/Cas9 technology be applied to VN1R1 research?

CRISPR/Cas9 technology offers powerful new approaches for VN1R1 research:

• Gene Editing in Cell Lines: Creating isogenic cell lines differing only in specific VN1R1 polymorphisms to study their functional effects in a controlled genetic background.

• Domain Swapping: Engineering chimeric receptors containing domains from gorilla and human VN1R1 to identify regions responsible for specific functional properties.

• Reporter Systems: Integrating fluorescent or luminescent reporters downstream of VN1R1 activation to create sensitive biosensors for ligand discovery.

• Regulatory Element Analysis: Using CRISPR to modify putative regulatory regions of VN1R1 to understand expression control mechanisms.

• Model Organism Modifications: Creating model organisms with humanized or gorilla-like VN1R1 to study behavioral effects, though such approaches would be subject to strict ethical oversight.

• High-Throughput Functional Screening: CRISPR libraries targeting VN1R1 interaction partners could help identify essential components of its signaling network.

These approaches must be conducted with appropriate ethical considerations, particularly for any applications involving model organisms.