Recombinant Gorilla gorilla gorilla Taste receptor type 2 member 31 (TAS2R31)

What is TAS2R31 and what is its role in bitter taste perception?

TAS2R31 belongs to the type 2 taste receptor family (TAS2Rs), which comprises G protein-coupled receptors that recognize compounds perceived as bitter to humans and aversive to vertebrates. These receptors initiate bitter taste perception by triggering depolarization of taste bud cells . TAS2R31 is also known by alternative names including T2R31 and T2R44, and it belongs to a five-member subfamily (TAS2R30-46) that responds to a diverse constellation of compounds .

In the context of functional studies, TAS2R31 has been identified as an agonist responsive to artificial sweeteners with bitter aftertastes, including saccharin and acesulfame K . The receptor is expressed not only in gustatory tissues but also in several non-gustatory tissues including lung, trachea, ovary, ganglia, and brain, suggesting broader physiological functions beyond taste perception .

What expression systems are most effective for producing functional recombinant TAS2R31?

For functional expression of TAS2R proteins, including TAS2R31, heterologous expression systems utilizing human embryonic kidney 293 (HEK293) cells have proven effective in numerous studies . When expressing recombinant TAS2R31, researchers typically employ the following methodology:

• Design expression vectors containing the TAS2R31 coding sequence with appropriate epitope tags for detection and purification

• Transiently or stably transfect mammalian cell lines, particularly HEK293 cells

• Co-express necessary signaling components such as G-proteins (typically Gα16gust44, a chimeric G-protein)

• Validate expression through Western blotting, immunofluorescence, or functional calcium mobilization assays

For gorilla TAS2R31 specifically, researchers may need to optimize codon usage for mammalian expression and consider the inclusion of chaperone proteins to enhance proper folding and membrane targeting .

What functional assays are recommended for characterizing recombinant gorilla TAS2R31 ligand specificity?

For characterizing the ligand specificity of recombinant gorilla TAS2R31, researchers should consider the following functional assays:

• Calcium Flux Assays: The most widely used method involves detecting intracellular calcium release following receptor activation. This approach requires:

  • Transfection of cells with gorilla TAS2R31 and appropriate G-protein constructs

  • Loading cells with calcium-sensitive fluorescent dyes (e.g., Fluo-4 AM)

  • Measuring fluorescence changes upon ligand application using plate readers or fluorescence microscopy

  • Analyzing dose-response relationships to determine EC50 values for various bitter compounds

• cAMP Accumulation Assays: As an alternative to calcium measurements, researchers can quantify changes in cyclic AMP levels following receptor activation.

• Receptor Internalization Assays: Monitoring receptor trafficking using fluorescently tagged TAS2R31 can provide insights into receptor dynamics following ligand binding.

• Molecular Docking and Mutagenesis: Combining computational docking with site-directed mutagenesis can identify key residues involved in ligand recognition. This approach has been successful with human TAS2R31 variants .

A cross-species comparison between human and gorilla TAS2R31 responses to known bitter compounds can reveal evolutionary adaptations in bitter taste perception relevant to dietary specialization.

How can researchers identify tissue-specific expression patterns of TAS2R31 in gorilla samples?

To investigate tissue-specific expression patterns of TAS2R31 in gorilla samples, researchers should implement a multi-method approach:

• RNA Analysis:

  • RT-qPCR using TAS2R31-specific primers designed based on the gorilla sequence

  • RNA-seq analysis of various tissues to obtain comprehensive expression profiles

  • In situ hybridization to visualize tissue and cellular localization

• Protein Detection:

  • Immunohistochemistry using antibodies validated for cross-reactivity with gorilla TAS2R31

  • Western blotting of tissue lysates

  • Immunofluorescence microscopy for subcellular localization

• Reporter Systems:

  • For in vivo models, Cre-mediated recombination approaches similar to those used in mouse studies can be adapted . This involves:

    • Generating TAS2R31-specific Cre knock-in constructs

    • Using binary genetic approaches with fluorescent reporters to visualize TAS2R31-expressing cells

    • Tracking expression during developmental stages

Based on human and mouse studies, researchers should examine both gustatory tissues (tongue, palate) and non-gustatory tissues including respiratory tract (lung, trachea), reproductive tissues (ovary), neural tissues (ganglia, brain), and digestive organs .

What genetic engineering approaches can be used to study TAS2R31 function in cellular models?

Several genetic engineering approaches can be employed to study TAS2R31 function:

• CRISPR-Cas9 Gene Editing:

  • Generate knockout cell lines to study loss-of-function effects

  • Introduce specific mutations identified in gorilla TAS2R31 into human cell lines

  • Create knock-in reporter lines to track receptor expression and trafficking

• Cre-Lox Recombination Systems:

  • Similar to the TAS2R131-Cre knock-in mouse strain described in the literature , researchers can develop systems where TAS2R31-expressing cells are specifically labeled or manipulated

  • Upon TAS2R31 expression, Cre is produced, excising the STOP cassette and activating reporter expression

• Inducible Expression Systems:

  • Tetracycline-controlled or other inducible promoters to regulate TAS2R31 expression

  • This approach allows temporal control of receptor expression for developmental studies

• Chimeric Receptor Approaches:

  • Generate chimeric receptors between gorilla and human TAS2R31 to identify domains responsible for differential ligand recognition

  • Swap specific transmembrane domains or extra/intracellular loops to map functional regions

These approaches enable detailed investigation of gorilla TAS2R31 function, potentially revealing unique adaptations in bitter taste perception related to dietary specialization in gorillas.

How do functional variations in TAS2R31 correlate with evolutionary adaptations in great apes?

Functional variations in TAS2R31 across great apes, including gorillas, likely reflect evolutionary adaptations to diverse ecological niches and dietary preferences:

• Polymorphism Analysis:
  Human TAS2R genes exhibit extensive polymorphism, with numerous nonsynonymous variants affecting receptor function . Analysis of gorilla TAS2R31 should examine:

  • Single nucleotide polymorphisms (SNPs) within gorilla populations

  • Comparison of these polymorphisms with those found in humans and other great apes

  • Computational prediction of functional effects using tools like PolyPhen-2 and SIFT, similar to analyses performed on human TAS2R variants

• Selection Pressure Analysis:
  Studies of human TAS2R genes have found evidence suggesting relaxation of selective pressure in recent human evolution . Researchers should examine:

  • Ratios of nonsynonymous to synonymous substitutions (dN/dS) in gorilla TAS2R31

  • Population-specific selection signatures using statistics like Tajima's D

  • Fixation index (FST) values to assess differentiation between populations

• Comparative Functional Studies:

  Species	Key Functional Variants	Associated Phenotypic Differences
  Human	Multiple, including R35W in TAS2R31	Altered response to saccharin and acesulfame K
  Gorilla	To be characterized	Potentially adapted to gorilla-specific diet
  Chimpanzee	To be characterized	May reflect dietary adaptations
  Orangutan	To be characterized	May reflect dietary adaptations

• Ecological Correlation:
  Researchers should investigate correlations between TAS2R31 variants and:

  • Known bitter compounds in species-specific diets

  • Potential toxic plant compounds encountered in natural habitats

  • Dietary specialization and food preference behaviors

This evolutionary perspective provides insight into how variations in TAS2R31 might contribute to adaptive responses to environmental challenges faced by different great ape species.

What are the key challenges in obtaining high-yield recombinant gorilla TAS2R31 expression?

Producing high-yield, functional recombinant gorilla TAS2R31 presents several technical challenges:

• Membrane Protein Expression Issues:

  • As a G protein-coupled receptor, TAS2R31 contains multiple transmembrane domains that complicate proper folding and trafficking

  • Low expression levels are common with bitter taste receptors

  • Potential solution: Use specialized expression vectors with strong promoters and optimization of codon usage for the expression system

• Protein Solubility and Stability:

  • Membrane proteins are inherently difficult to solubilize while maintaining native conformation

  • Researchers should evaluate multiple detergents or nanodiscs for optimal solubilization

  • Consider fusion partners that enhance solubility (e.g., MBP, SUMO)

• Post-translational Modifications:

  • Ensure the expression system provides appropriate glycosylation and other modifications

  • Mammalian expression systems are preferable over bacterial systems for this reason

• Functional Verification:

  • Confirming that the recombinant protein maintains native ligand-binding properties

  • Development of robust functional assays specific to gorilla TAS2R31

  • Positive controls using known ligands like saccharin or acesulfame K based on human TAS2R31 studies

How can researchers address cross-reactivity issues when studying TAS2R31 across primate species?

Cross-reactivity issues present significant challenges when studying TAS2R31 across primate species:

• Antibody Development and Validation:

  • Develop antibodies against conserved epitopes across primate TAS2R31 orthologs

  • Rigorously validate antibody specificity using:

    • Western blots with recombinant proteins from multiple species

    • Immunoprecipitation followed by mass spectrometry

    • Immunofluorescence with appropriate knockout controls

• Primer and Probe Design for Nucleic Acid Detection:

  • Design primers targeting conserved regions for cross-species amplification

  • Validate amplification specificity using sequencing

  • Consider species-specific probes for quantitative applications

• Ligand Specificity Assessment:

  • Test a panel of known human TAS2R31 ligands against recombinant gorilla TAS2R31

  • Generate dose-response curves to identify differences in potency or efficacy

  • Create a comparative pharmacological profile across species

• Computational Approaches:

  • Homology modeling to predict structural differences that might affect ligand binding

  • Molecular docking simulations to predict cross-species differences in ligand interactions

  • Sequence alignment tools to identify conserved functional domains

What are the optimal storage and handling conditions for maintaining recombinant TAS2R31 stability?

Based on information available for recombinant proteins similar to TAS2R31, the following storage and handling conditions are recommended:

• Storage Buffer Composition:

  • Tris-based buffer with 50% glycerol as indicated for commercial recombinant gorilla TAS2R31

  • pH maintenance between 7.2-7.5 for optimal stability

  • Consider addition of protease inhibitors for long-term storage

• Temperature Considerations:

  • Store at -20°C for regular use, or -80°C for extended storage

  • Avoid repeated freeze-thaw cycles; prepare working aliquots stored at 4°C for up to one week

  • Thaw samples on ice when removing from frozen storage

• Handling Recommendations:

  • Minimize exposure to light, particularly for fluorescently tagged constructs

  • Perform manipulations at 4°C when possible

  • Consider addition of reducing agents (e.g., DTT) to prevent oxidation of cysteine residues

• Quality Control:

  • Regularly assess protein integrity via SDS-PAGE

  • Verify functionality using established ligand-binding or signaling assays

  • Monitor for aggregation using dynamic light scattering or size-exclusion chromatography

What bioinformatic approaches are recommended for analyzing TAS2R31 sequence variations across primates?

For comprehensive analysis of TAS2R31 sequence variations across primates, researchers should employ the following bioinformatic approaches:

• Sequence Alignment and Phylogenetic Analysis:

  • Multiple sequence alignment using tools like MUSCLE or CLUSTAL

  • Construction of phylogenetic trees to visualize evolutionary relationships

  • Analysis of selection pressures using methods like PAML

• Variation Identification and Classification:

  • Identification of SNPs and indels across primate species

  • Classification of variants as synonymous or nonsynonymous

  • Prediction of functional consequences using tools like:

    • PolyPhen-2 and SIFT, which have been successfully used for human TAS2R variants

    • PROVEAN for insertions and deletions

• Structural Analysis:

  • Homology modeling based on GPCR crystal structures

  • Identification of conserved functional domains

  • Prediction of transmembrane regions and binding pockets

  • Molecular dynamics simulations to assess effects of variants

• Population Genetics Metrics:

  Metric	Application to TAS2R31 Analysis
  Nucleotide diversity (π)	Ranging from 0.02% to 0.36% in human TAS2R genes
  Fixation index (FST)	Ranging from 0.01 to 0.26 in human TAS2R genes
  Tajima's D	Used to detect signatures of selection
  dN/dS ratio	To assess selective pressure on protein-coding regions

These approaches will provide a comprehensive understanding of evolutionary patterns in TAS2R31 across primates and identify potentially functionally significant variations.

How should researchers interpret differences in ligand response profiles between human and gorilla TAS2R31?

When interpreting differences in ligand response profiles between human and gorilla TAS2R31, researchers should consider:

• Pharmacological Parameter Comparison:

  • Compare EC50 values (potency) for shared ligands

  • Assess maximum response (efficacy) differences

  • Evaluate differences in activation thresholds

  • Analyze kinetics of receptor activation and desensitization

• Structure-Function Relationship Analysis:

  • Correlate sequence differences with altered ligand responses

  • Identify key amino acid residues responsible for species-specific responses

  • Consider the role of specific domains (e.g., transmembrane regions, extracellular loops)

• Ecological and Evolutionary Context:

  • Relate differences to dietary specialization of gorillas versus humans

  • Consider potential toxic compounds encountered in natural habitats

  • Evaluate whether differences reflect adaptations or genetic drift

• Functional Redundancy Considerations:

  • Assess overlap in ligand specificity with other TAS2R family members

  • Consider compensatory mechanisms that might exist in vivo

  • Evaluate the net effect on bitter taste perception in the context of the complete receptor repertoire

• Translational Implications:

  • Consider how identified differences might inform understanding of human taste perception

  • Evaluate potential implications for non-gustatory functions of TAS2R31 in tissues like airways and gut

  • Assess whether findings provide insight into therapeutic targeting of bitter taste receptors

What emerging technologies could advance our understanding of gorilla TAS2R31 function in vivo?

Several emerging technologies hold promise for advancing our understanding of gorilla TAS2R31 function:

• Organoid Models:

  • Development of tongue and taste bud organoids from gorilla stem cells

  • Co-culture systems that recapitulate taste receptor cell microenvironments

  • Application of single-cell transcriptomics to characterize cell populations

• Advanced Imaging Techniques:

  • Super-resolution microscopy for subcellular localization

  • FRET/BRET sensors to monitor receptor activation in real time

  • Light-sheet microscopy for 3D visualization in tissue contexts

• Biosensor Development:

  • GPCR-based biosensors that report TAS2R31 activation via fluorescence or luminescence

  • Cell-based assays with improved sensitivity and throughput

  • Microfluidic systems for rapid screening of potential ligands

• Animal Models with Humanized or Gorilla TAS2R31:

  • Generation of knock-in models expressing gorilla TAS2R31

  • Behavioral testing to assess functional consequences in vivo

  • Conditional expression systems using Cre-mediated recombination approaches similar to those described for TAS2R131

• Computational Approaches:

  • Advanced machine learning for predicting ligand-receptor interactions

  • Systems biology models integrating TAS2R31 signaling with downstream pathways

  • In silico evolution models to predict adaptive changes

How might understanding gorilla TAS2R31 function contribute to comparative physiology research?

Understanding gorilla TAS2R31 function can make significant contributions to comparative physiology research in several key areas:

• Evolutionary Adaptations in Sensory Systems:

  • Provide insights into how taste perception systems evolved in response to dietary specialization

  • Reveal mechanisms of sensory adaptation in diverse ecological niches

  • Contribute to understanding the evolution of food preference behaviors

• Extra-oral Functions of Taste Receptors:

  • Research in humans and mice has revealed TAS2R expression in non-gustatory tissues including lung, trachea, ovary, ganglia, and brain

  • Comparative studies may reveal conserved or divergent functions of TAS2R31 in these tissues

  • Potential roles in innate immunity, respiratory function, and other physiological systems

• Structure-Function Relationships in GPCRs:

  • Cross-species comparisons can identify critical residues and domains for TAS2R31 function

  • Reveal principles of ligand recognition that extend to other G protein-coupled receptors

  • Illuminate mechanisms of receptor activation and signal transduction

• Dietary Ecology and Plant-Animal Interactions:

  • Connect molecular adaptations in TAS2R31 to feeding behaviors and food selection

  • Provide insights into co-evolutionary relationships between plants producing bitter compounds and primate consumers

  • Enhance understanding of dietary adaptations in great ape evolution

• Biomedical Applications:

  • Potential for identifying novel ligands with therapeutic applications

  • Understanding mechanisms of bitter taste perception relevant to medication compliance

  • Insights into non-gustatory functions of TAS2Rs that may have clinical relevance