Recombinant Mouse Taste receptor type 2 member 116 (Tas2r116)

What is the expression pattern of Tas2r116 in mouse tissues?

While specific Tas2r116 expression data is limited, research demonstrates that all functional mouse Tas2r genes are expressed in the epithelium of the posterior tongue, particularly in the vallate papillae, albeit at varying levels . Some receptors like Tas2r108, Tas2r118, Tas2r126, Tas2r135, and Tas2r137 show high expression (approximately 20% of α-gustducin mRNA levels), while others such as Tas2r114, Tas2r122, and Tas2r140 are expressed at much lower levels . Expression patterns correlate between quantitative RT-PCR and in situ hybridization findings . To determine Tas2r116-specific expression, researchers should perform:

• Quantitative RT-PCR using Tas2r116-specific primers on RNA from posterior tongue epithelium

• In situ hybridization with Tas2r116-specific probes on vallate papillae sections

• Comparative analysis across other taste tissues (foliate and fungiform papillae)

• Expression analysis in non-gustatory tissues, as some Tas2rs show extraoral expression patterns

How can I optimize heterologous expression of recombinant Tas2r116?

Successful heterologous expression of mouse Tas2r proteins is critical for functional characterization. Based on published approaches with other Tas2r receptors, researchers should consider:

• Expression vector selection: Use mammalian expression vectors with strong promoters (CMV) and add epitope tags (e.g., Rho tag) at the N-terminus to facilitate detection

• Host cell selection: HEK293T cells expressing appropriate G-protein chimeras (Gα16gust44 rather than Gα15) provide greater sensitivity for functional assays

• Trafficking optimization: As some Tas2rs show poor cell surface expression, consider adding trafficking enhancers such as the first 45 amino acids of rat somatostatin receptor 3 to the N-terminus

• Verification of expression: Perform immunocytochemistry on both permeabilized and non-permeabilized cells to assess both total expression and cell surface localization

The following table summarizes cell surface expression patterns observed for various mouse Tas2rs:

What are the predicted structural features of Tas2r116?

While specific Tas2r116 structural data is not provided in the search results, homology modeling approaches similar to those used for other TAS2Rs can be applied:

• Template selection: Recent structures of human TAS2R46 can serve as templates for homology modeling of mouse Tas2r116

• Transmembrane domain prediction: Like other bitter taste receptors, Tas2r116 likely contains seven transmembrane domains with the highest conservation in TM3 and TM5, which are critical for signal transduction

• Binding pocket analysis: Bitter taste receptors typically have binding pockets formed by residues on the extracellular side of the transmembrane domains and in the extracellular loops

• Extracellular loop modeling: Pay particular attention to ECL2, which connects TM4 and TM5 and shows high flexibility and diversity across TAS2Rs

Researchers should note that initial modeling will have limitations due to the relatively low sequence identity between human and mouse bitter taste receptors (often around 27%) .

What are the key considerations for designing functional assays for Tas2r116?

Functional characterization of Tas2r116 requires carefully designed assays:

• Calcium flux assays: These are standard for measuring bitter taste receptor activation. Use calcium-sensitive fluorescent dyes (e.g., Fluo-4) in transfected cells expressing Tas2r116

• G-protein selection: Use Gα16gust44 chimeric proteins rather than Gα15 for greater sensitivity, as demonstrated with Tas2r105

• Compound library selection: Test a diverse set of bitter compounds. Previous studies have used libraries of 128 predominantly naturally occurring bitter compounds

• Dose-response measurements: Determine both threshold concentrations and EC50 values to assess both potency and efficacy

• Controls: Include known activators of other Tas2rs as positive controls and mock-transfected cells as negative controls

How can I identify specific ligands for Tas2r116 when previous studies have excluded this receptor?

Comprehensive ligand identification requires systematic approaches:

• Phylogenetic analysis: Compare Tas2r116 sequence with other mouse Tas2rs that have known ligand profiles to predict potential cross-reactivity

• Structure-based virtual screening: Use homology models of Tas2r116 to perform in silico docking of potential ligands, prioritizing compounds that show favorable binding energies

• Targeted screening strategy:

  • Begin with compounds that activate multiple other Tas2rs, especially structurally diverse bitter compounds

  • Test bile acids, as they activate several mouse Tas2rs including Tas2r105, Tas2r108, Tas2r117, Tas2r123, Tas2r126, and Tas2r144

  • Consider N-acyl homoserine lactones, which activate specific Tas2rs and are involved in bacterial quorum sensing

• Validation experiments: Confirm hits using concentration-dependent responses and receptor specificity controls

• Investigate ligand-specific effects using structurally related compounds, as demonstrated with 4-nitrophenyl substitutions for TAS2R16

What mutational analysis approach would best determine critical residues for Tas2r116 ligand binding and signal transduction?

Based on successful approaches with other bitter taste receptors:

• Comprehensive mutation library: Create a complete mutation library covering all amino acid positions in Tas2r116, with an average of 2 substitutions per position (one conserved, one non-conserved)

• High-throughput screening: Evaluate the entire mutation library in a 384-well array format using calcium flux assays

• Two-phase analysis:

  • First, identify mutations that eliminate signaling by all ligands (likely involved in general receptor function or signal transduction)

  • Second, identify mutations with ligand-specific effects (≥2.5-fold difference in activity between ligands), which likely contribute to ligand specificity

• Structural mapping: Map critical residues onto a transmembrane domain schematic to identify patterns, with particular focus on TM3 and TM5

• Surface trafficking analysis: Distinguish between mutations affecting trafficking versus specific ligand interactions

For TAS2R16, this approach identified 39 positions where substitution significantly reduced activation without disrupting surface trafficking, with 90% of these residues clustering within the transmembrane domains .

How does the evolutionary conservation of Tas2r116 compare with other mouse bitter taste receptors?

Evolutionary analysis can provide insights into functional significance:

• Comparative genomics: Analyze Tas2r116 sequences across rodent species to identify conserved residues

• Positive selection analysis: Calculate dN/dS ratios to identify regions under positive selection

• Cross-species functional comparison: Where possible, express and test orthologs from different species

• Specific residue comparison: Focus on positions known to be important in other Tas2rs, such as position 96 in TAS2R16, where the N96T mutation affects ligand sensitivity

• Phylogenetic placement: Determine if Tas2r116 belongs to a specific Tas2r subfamily that might predict functional properties

The study of human TAS2R16 revealed that specific amino acid substitutions can confer different sensitivities to ligands, as demonstrated by the N96T mutation which increased sensitivity to both salicin and 4-NP-β-mannoside .

What approaches can resolve discrepancies in Tas2r activation profiles between different experimental systems?

Addressing methodological discrepancies is crucial for accurate characterization:

• G-protein coupling comparison: Test both Gα15 and Gα16gust44 systems in parallel, as demonstrated with Tas2r105 where low efficacy activators resulted in reduced or absent responses in Gα15-expressing cells compared to the more sensitive Gα16gust44 system

• Expression level normalization: Quantify receptor expression levels using epitope tags and normalize functional data accordingly

• Assay sensitivity optimization:

  • Test multiple calcium indicators with different sensitivities

  • Optimize cell density, transfection efficiency, and signal detection parameters

• Inter-laboratory validation: Standardize protocols and share reagents to confirm results across different research groups

• Correlation with in vivo studies: Validate findings using behavioral tests with knockout mice to connect in vitro observations with physiological responses

How can I investigate potential heterodimer formation between Tas2r116 and other Tas2r family members?

Investigating potential oligomerization requires specialized approaches:

• Bioluminescence/Förster resonance energy transfer (BRET/FRET): Tag potential interaction partners with compatible fluorophores or luminescent proteins to detect proximity-dependent energy transfer

• Co-immunoprecipitation: Use differentially tagged Tas2r proteins to detect physical interactions

• Functional complementation: Express split receptor constructs that require dimerization for function

• Cross-linking studies: Use chemical cross-linkers followed by mass spectrometry to identify interacting proteins

• Single-molecule imaging: Visualize receptor diffusion and colocalization in the plasma membrane of live cells

The evidence for GPCR heterodimerization is growing, and investigating whether Tas2r116 forms functional complexes with other family members could reveal new aspects of bitter taste signaling.

What are the optimal methods for quantifying Tas2r116 gene and protein expression?

Accurate quantification requires:

• Transcript analysis:

  • Design highly specific primers that distinguish Tas2r116 from other family members

  • Validate primers against genomic DNA from Tas2r116 knockout mice

  • Use digital PCR or RNA-seq for absolute quantification

  • For relative expression, normalize to multiple reference genes, including α-gustducin

• Protein detection:

  • Generate Tas2r116-specific antibodies or use epitope tags for detection

  • Validate antibody specificity using knockout controls

  • Use quantitative western blotting with standard curves

  • Consider proximity ligation assays for in situ protein quantification

Comprehensive expression profiling should include both lingual and extra-oral tissues, as bitter taste receptors show expression in various tissues beyond the tongue .

How should I design experiments to test the effects of single nucleotide polymorphisms (SNPs) in Tas2r116?

SNP analysis requires:

• SNP identification:

  • Screen mouse strains for naturally occurring Tas2r116 SNPs

  • Focus on non-synonymous SNPs that change amino acid sequence

  • Prioritize SNPs in regions corresponding to ligand binding or G-protein coupling

• Functional characterization:

  • Create matched expression constructs differing only at the SNP position

  • Test effects on surface expression using immunocytochemistry

  • Measure ligand responses with dose-response curves to determine changes in EC50 values

  • Analyze G-protein coupling efficiency

• In vivo validation:

  • Generate knock-in mice expressing specific SNP variants

  • Perform behavioral tests to assess differences in bitter taste perception

This approach parallels studies of the N96T mutation in TAS2R16, which demonstrated a 5-fold decrease in EC50 values for activation by both salicin and 4-NP-β-mannoside .

What are the most promising approaches for integrating Tas2r116 findings into broader bitter taste perception models?

Integrative approaches include:

• Comparative analysis: Place Tas2r116 functional properties in context with the complete mouse Tas2r family

• Systems biology: Incorporate Tas2r116 data into computational models of taste perception

• Circuit-level investigation: Study how Tas2r116-expressing cells integrate with the larger taste bud circuitry

• Behavioral correlations: Connect molecular properties to behavioral responses in wild-type and transgenic mice

• Translational aspects: Explore how findings with Tas2r116 inform understanding of human bitter taste perception

Comprehensive characterization of the complete Tas2r family, including previously excluded members like Tas2r116, will provide a more complete picture of bitter taste coding mechanisms.

What are the most reliable resources for Tas2r116 research tools and protocols?

Researchers should consult:

• Mouse Genome Informatics (MGI) database for genetic information

• Protocols from laboratories that have successfully characterized other Tas2r family members

• Publicly available plasmids and cell lines optimized for bitter taste receptor expression

• Standardized compound libraries used in previous bitter taste receptor studies

• Computational tools for homology modeling and ligand docking

Researchers should note that many bitter compound screening libraries contain approximately 128 predominantly naturally occurring bitter compounds with diverse chemical structures , providing a foundation for initial Tas2r116 characterization studies.