Recombinant Gorilla gorilla gorilla Taste receptor type 2 member 60 (TAS2R60)

What is TAS2R60 and what is its structure in primates?

TAS2R60 (Taste receptor type 2 member 60) is a G-protein coupled receptor belonging to the bitter taste receptor family (TAS2Rs). In humans, it is encoded by the TAS2R60 gene located on chromosome 7q35 . Like other TAS2Rs, it possesses a canonical 7-transmembrane structure with conserved short N- and C-terminal domains . The human TAS2R60 comprises 318 amino acids with a predicted molecular weight of approximately 36 kDa . While the specific sequence and structure of Gorilla gorilla gorilla TAS2R60 may have variations, it likely shares high homology with the human version given the evolutionary relationship between the species, though specific differences may reflect dietary adaptations between these species.

How does TAS2R60 function in taste perception systems?

TAS2R60, like other bitter taste receptors, functions primarily as a sensor for bitter compounds in vertebrates. When a bitter ligand binds to TAS2R60, it triggers a signal transduction cascade involving G-proteins, particularly gustducin, leading to calcium release and eventual signal transmission to the central nervous system. This process is part of the evolutionary mechanism to detect potentially harmful compounds in food . The signaling process can be studied using bioluminescence-based assays that measure intracellular calcium release following receptor activation . These assays demonstrate that specific agonists bind to TAS2Rs with varying potencies (EC50 values), and response magnitudes can be enhanced by optimizing receptor trafficking to the plasma membrane .

Where is TAS2R60 expressed beyond taste buds?

While TAS2R60 is canonically located in taste buds of the tongue where it initiates bitter taste perception, growing evidence indicates that TAS2Rs, including TAS2R60, are widely expressed in several extraoral systems . These include:

• Digestive system

• Respiratory system

• Genitourinary system

• Brain

• Immune cells

This extraoral expression pattern suggests that TAS2R60 may have diverse biological functions beyond taste perception, potentially involving chemosensation and defensive responses in various tissues . Research investigating these extraoral functions should consider tissue-specific expression patterns and potential functional adaptations in different primate species.

What expression systems are most effective for producing recombinant gorilla TAS2R60?

For recombinant expression of gorilla TAS2R60, mammalian cell lines such as AD-293 or 293AD are recommended based on their stronger adherent properties and capacity for GPCR expression . When designing expression constructs, consider these methodological approaches:

• Signal sequence optimization: Replace the native N-terminal sequence with signal sequences from well-expressed GPCRs. Research has shown that the signal sequence from the muscarinic acetylcholine M3 receptor (M3) significantly improves plasma membrane translocation of certain TAS2Rs, resulting in 2-3 fold increases in signal window compared to the commonly used somatostatin receptor type 3 (SST3) signal sequence .

• Codon optimization: Adapt the coding sequence to the codon usage bias of the expression host.

• Addition of epitope tags: Consider adding HiBiT or other tags to facilitate detection and purification without compromising function.

• Co-expression with accessory proteins: Include G-protein components, particularly Gα16-gust44, to enhance coupling efficiency and signal transduction .

The choice between these methods should be empirically evaluated as expression efficiency may vary between different TAS2Rs and between species variants.

What assays are most sensitive for measuring gorilla TAS2R60 activation?

Bioluminescence-based intracellular calcium release assays offer superior sensitivity for measuring TAS2R60 activation compared to traditional fluorescence-based methods . This approach uses the following components:

• Calcium-dependent photoprotein: mt-clytin II, which generates light upon calcium binding

• G-protein chimera: Gα16-gust44 to couple receptor activation to calcium signaling

• FLIPR measurement system: For high-throughput detection of luminescence signals

This assay format provides several advantages:

• Larger assay window than fluorescence-based assays

• Ability to evaluate ligands within autofluorescent matrices

• Lower background signal leading to improved signal-to-noise ratio

For full protocol implementation, cells should be transiently transfected with three components: the TAS2R60 gene construct, the Gα16-gust44 chimera, and the mt-clytin II photoprotein. Controls should include cells transfected with only mt-clytin II or with both Gα16-gust44 and mt-clytin II to discount non-specific activation .

How can cell surface expression of recombinant gorilla TAS2R60 be optimized?

Optimizing cell surface expression is critical for functional studies of TAS2Rs. Research has identified several strategies:

• Signal sequence screening: Test multiple signal sequences from well-expressed GPCRs. The M3 receptor signal sequence has been shown to cause the highest degree of plasma membrane translocation for certain TAS2Rs, significantly outperforming the commonly used SST3 tag .

• N-glycosylation site preservation: TAS2Rs are predominantly N-glycosylated at a conserved consensus site in the second extracellular loop, which is important for receptor trafficking. Ensure this site remains intact in the recombinant construct .

• Construct validation: Verify cell surface expression using HiBiT-tagged constructs before functional assays to confirm trafficking efficiency .

• Temperature adjustment: Consider lower incubation temperatures (30-32°C) during expression to facilitate proper folding of the recombinant protein.

The effectiveness of these strategies should be empirically determined for gorilla TAS2R60, as optimization requirements may differ between receptor subtypes and species variants.

How does gorilla TAS2R60 differ from human TAS2R60 in sequence and function?

While the search results don't provide specific information about gorilla TAS2R60 sequence differences, the approach to this question would involve:

• Sequence alignment analysis: Compare the amino acid sequences of gorilla and human TAS2R60 to identify conserved and divergent regions, particularly in ligand binding domains and G-protein coupling interfaces.

• Homology modeling: Construct structural models based on known GPCR structures to predict functional implications of sequence differences.

• Functional assays: Test responses to a panel of bitter compounds to identify differences in ligand specificity and sensitivity between species variants.

TAS2R genes show significant genetic diversity across populations, with 721 SNPs identified across the TAS2R family in human populations, of which 525 were nonsynonymous substitutions . Similar variation might be expected between human and gorilla orthologs, potentially reflecting dietary adaptations. Comparative studies would help identify functional domains under selective pressure and provide insights into the evolution of taste perception in primates.

What evolutionary pressures have shaped TAS2R60 in great apes?

TAS2R genes show evidence of both balancing selection (maintaining genetic diversity) and directional selection in different populations . For great apes, including gorillas, evolutionary pressures likely include:

• Dietary specialization: Adaptation to species-specific plant food sources and their bitter compound profiles.

• Toxin avoidance: Selection for receptors sensitive to toxic compounds present in the natural environment.

• Population history: The history of great ape populations, including bottlenecks and expansions, has influenced genetic diversity in taste receptors.

Human history over the last 65,000 years has been characterized by explosive population growth and rapid diffusion, bringing humans into contact with numerous novel environments . These factors may have altered selective pressures on TAS2Rs, potentially creating divergence from the gorilla lineage which experienced different population dynamics and ecological pressures.

Research approaches should include analysis of nonsynonymous to synonymous substitution ratios (dN/dS) across primate TAS2R60 sequences to identify regions under positive selection, and correlation of genetic variations with ecological niches and dietary patterns.

How does the genetic diversity of TAS2R60 compare between human populations and gorilla populations?

Human TAS2R genes show extensive genetic diversity across global populations. In human TAS2R60 specifically, numerous genetic variants have been documented, though the search results don't provide the exact count for this specific receptor .

For comparative studies between humans and gorillas, research approaches should include:

• Population sampling: Collect genetic data from multiple gorilla populations representing different subspecies and geographical regions.

• Whole-gene sequencing: Analyze complete TAS2R60 sequences rather than targeted SNP analysis to capture the full range of genetic diversity.

• Functional validation: Test variants for their impact on receptor function using in vitro expression systems and ligand response assays.

This data would provide insights into how natural selection has shaped taste perception in different primate lineages and might correlate with dietary specializations.

What methodologies effectively differentiate between specific and non-specific activation in TAS2R60 functional assays?

Distinguishing specific from non-specific activation is crucial for accurate characterization of TAS2R60 function. Effective methodologies include:

• Appropriate controls: Include cells transfected to express both Gα16-gust44 and mt-clytin II, or solely mt-clytin II, without the receptor to identify non-specific responses . Non-specific activation typically produces flat, non-dose dependent calcium responses or extremely weak potency curves .

• Dose-response relationships: Specific activation should produce sigmoidal dose-response curves with defined EC50 values consistent with receptor-mediated responses.

• Competitive antagonist testing: Use known TAS2R antagonists to confirm receptor-specific activation.

• Receptor mutagenesis: Introduce point mutations in key binding residues to confirm specificity of ligand interactions.

• Cross-desensitization experiments: Test whether pre-exposure to a known agonist prevents subsequent responses to test compounds.

Research has shown that when proper controls are employed, non-specific activation can be clearly distinguished from receptor-mediated responses, which show characteristic dose-dependent activation patterns .

How does post-translational modification affect gorilla TAS2R60 function?

While the search results don't provide specific information about post-translational modifications of gorilla TAS2R60, research on human TAS2Rs indicates important considerations:

• N-glycosylation: TAS2Rs are predicted to be predominantly N-glycosylated at a conserved consensus site in the second extracellular loop, which has been demonstrated to be important for receptor trafficking to the cell surface . Analysis of TAS2R sequences predicts that all 25 human TAS2Rs have this conserved glycosylation site .

• Phosphorylation: Potential phosphorylation sites in intracellular domains may regulate receptor desensitization and internalization.

• Palmitoylation: Potential cysteine residues in the C-terminal domain may undergo palmitoylation, affecting membrane localization.

Research approaches should include:

• Site-directed mutagenesis of predicted modification sites

• Mass spectrometry to identify actual modifications in expressed receptors

• Functional assays comparing wild-type and modification-deficient mutants

• Inhibitor studies targeting specific modification enzymes

Understanding these modifications is crucial for optimizing recombinant expression systems and interpreting functional data accurately.

What are the key challenges in studying ligand specificity of gorilla TAS2R60?

Researchers face several challenges when investigating ligand specificity of gorilla TAS2R60:

• Limited knowledge of natural ligands: The natural bitter compounds encountered by gorillas in their diet are poorly characterized, making it difficult to select ecologically relevant test compounds.

• Functional expression barriers: TAS2Rs often express poorly in heterologous systems, necessitating optimization strategies such as signal sequence substitution . Even with the best available signal sequences like the M3 receptor tag, expression levels may remain suboptimal for certain receptors .

• Assay limitations: While bioluminescence-based assays offer improved sensitivity over fluorescence-based approaches, they still have detection limits that may miss low-affinity interactions .

• Species-specific cofactors: Gorilla-specific accessory proteins or cellular components may be necessary for full receptor function but are absent in commonly used expression systems.

• Verification in native tissue: Confirming in vitro findings in native gorilla taste tissues is logistically challenging due to limited access to samples and ethical considerations.

Future research should focus on developing better expression systems, identifying natural ligands through analytical chemistry of gorilla food sources, and developing computational models that can predict ligand interactions based on receptor structure.

How can computational approaches improve prediction of functional impacts of TAS2R60 variants?

Computational methods play an increasingly important role in predicting the functional consequences of TAS2R60 variants:

• Current prediction tools: Tools like PolyPhen-2 and SIFT are currently used to predict functional impacts of nonsynonymous substitutions in TAS2Rs . These tools identified 131 SNPs across TAS2Rs that were predicted to be both "Possibly or Probably Damaging" by PolyPhen-2 and "Deleterious" by SIFT .

• Limitations of current approaches: Current tools may not fully capture the complexity of GPCR function, particularly for less-studied receptors like TAS2R60. Among sites where classification disagreed between the two methods, 51 were scored by PolyPhen-2 to be potentially damaging but not by SIFT, and 57 showed the reverse pattern .

• Future computational approaches should incorporate:

  • Molecular dynamics simulations to model ligand binding and receptor activation

  • Machine learning algorithms trained on experimental TAS2R functional data

  • Integration of structural information as it becomes available

  • Consideration of epistatic interactions between multiple variants

  • Population-specific models that account for haplotype structure

By combining these approaches with experimental validation, researchers can develop more accurate models for predicting how genetic variants in gorilla TAS2R60 affect function and potentially correlate with dietary adaptations.

What emerging technologies could advance the study of gorilla TAS2R60 structure and function?

Several emerging technologies hold promise for advancing our understanding of gorilla TAS2R60:

• Cryo-EM for GPCR structure determination: As cryo-electron microscopy techniques advance, obtaining structural information for TAS2Rs becomes increasingly feasible, potentially revealing species-specific structural features of gorilla TAS2R60.

• Single-cell transcriptomics: This approach could identify cell-specific expression patterns of TAS2R60 in gorilla taste tissues and extraoral tissues, providing context for functional studies.

• CRISPR-mediated genome editing: Creating knock-in models with gorilla TAS2R60 in human cell lines or model organisms could provide systems for studying receptor function in more native-like contexts.

• Organoid technology: Developing taste bud organoids from gorilla stem cells could provide more physiologically relevant systems for studying receptor function.

• Advanced computational modeling: As more GPCR structures become available, improved homology modeling and molecular dynamics simulations can provide insights into gorilla TAS2R60 structure-function relationships.

• Nanodiscs and lipid bilayer technologies: These systems allow the study of purified receptors in defined membrane environments, potentially revealing lipid-dependent aspects of receptor function.

These technologies, used in combination, have the potential to significantly advance our understanding of gorilla TAS2R60 biology and its role in primate evolution and dietary adaptation.

Table of Key Differences Between Human and Great Ape TAS2R60