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Allosteric modulation of the fish taste receptor type 1 (T1R) family by the extracellular chloride ion.

ABSTRACT: Many G protein-coupled receptors (GPCRs) are allosterically modulated by inorganic ions. Although the intraoral ionic composition of the oral cavity varies depending on the living environment and feeding behavior, little is known about whether and how it affects the function of taste receptor type 1 (T1R), a member of the class C GPCR family. Here, we report that chloride ions allosterically modulate the functions of specific fish T1Rs, namely, mfT1R2a/mfT1R3 and zfT1R2a/zfT1R3. Site-directed mutagenesis revealed mfT1R2a K265, which lies in the extracellular domain of mfT1R2a, to be as a critical residue for the modulation of mfT1R2a/mfT1R3 by Cl^-. However, this residue is not conserved in zfT1R2a, and the introduction of the key residue at the corresponding site of another T1R, mfT1R2b, did not confer Cl^- susceptibility. These results indicate the variability of the determinants of Cl^- susceptibility.

SUBMITTER: Goda R

PROVIDER: S-EPMC10539361 | biostudies-literature | 2023 Sep

REPOSITORIES: biostudies-literature

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Allosteric modulation of the fish taste receptor type 1 (T1R) family by the extracellular chloride ion.

Goda Ryusei R Watanabe Soichi S Misaka Takumi T

Scientific reports 20230928 1

Many G protein-coupled receptors (GPCRs) are allosterically modulated by inorganic ions. Although the intraoral ionic composition of the oral cavity varies depending on the living environment and feeding behavior, little is known about whether and how it affects the function of taste receptor type 1 (T1R), a member of the class C GPCR family. Here, we report that chloride ions allosterically modulate the functions of specific fish T1Rs, namely, mfT1R2a/mfT1R3 and zfT1R2a/zfT1R3. Site-directed mu ...[more]

PMID: 37770555

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Project description:BackgroundChemical senses are one of the foremost means by which organisms make sense of their environment, among them the olfactory and gustatory sense of vertebrates and arthropods. Both senses use large repertoires of receptors to achieve perception of complex chemosensory stimuli. High evolutionary dynamics of some olfactory and gustatory receptor gene families result in considerable variance of chemosensory perception between species. Interestingly, both ora/v1r genes and the closely related t2r genes constitute small and rather conserved families in teleost fish, but show rapid evolution and large species differences in tetrapods. To understand this transition, chemosensory gene repertoires of earlier diverging members of the tetrapod lineage, i.e. lobe-finned fish such as Latimeria would be of high interest.ResultsWe report here the complete T2R repertoire of Latimeria chalumnae, using thorough data mining and extensive phylogenetic analysis. Eighty t2r genes were identified, by far the largest family reported for any species so far. The genomic neighborhood of t2r genes is enriched in repeat elements, which may have facilitated the extensive gene duplication events resulting in such a large family. Examination of non-synonymous vs. synonymous substitution rates (dN/dS) suggests pronounced positive Darwinian selection in Latimeria T2Rs, conceivably ensuring efficient neo-functionalization of newly born t2r genes. Notably, both traits, positive selection and enrichment of repeat elements in the genomic neighborhood, are absent in the twenty v1r genes of Latimeria. Sequence divergence in Latimeria T2Rs and V1Rs is high, reminescent of the corresponding teleost families. Some conserved sequence motifs of Latimeria T2Rs and V1Rs are shared with the respective teleost but not tetrapod genes, consistent with a potential role of such motifs in detection of aquatic chemosensory stimuli.ConclusionsThe singularly large T2R repertoire of Latimeria may have been generated by facilitating local gene duplication via increased density of repeat elements, and efficient neofunctionalization via positive Darwinian selection.The high evolutionary dynamics of tetrapod t2r gene families precedes the emergence of tetrapods, i.e. the water-to-land transition, and thus constitutes a basal feature of the lobe-finned lineage of vertebrates.

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Allosteric modulation of the fish taste receptor type 1 (T1R) family by the extracellular chloride ion.

Publications

Allosteric modulation of the fish taste receptor type 1 (T1R) family by the extracellular chloride ion.

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