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The repertoire of olfactory C family G protein-coupled receptors in zebrafish: candidate chemosensory receptors for amino acids.

Alioto TS, Ngai J - BMC Genomics (2006)

Bottom Line: Interestingly, an analysis of sequence conservation and selective pressure in the zebrafish receptors revealed the retention of a conserved sequence motif previously shown to be required for ligand binding in other amino acid receptors.Based on our findings, we propose that the repertoire of zebrafish olfactory C family GPCRs has evolved to allow the detection and discrimination of a spectrum of amino acid and/or amino acid-based compounds, which are potent olfactory cues in fish.Furthermore, as the major groups of fish receptors and mammalian V2R receptors appear to have diverged significantly from a common ancestral gene(s), these receptors likely mediate chemosensation of different classes of chemical structures by their respective organisms.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Molecular and Cell Biology, Functional Genomics Laboratory, and Helen Wills Neuroscience Institute, University of California, Berkeley, California 94720, USA. talioto@imim.es <talioto@imim.es>

ABSTRACT

Background: Vertebrate odorant receptors comprise at least three types of G protein-coupled receptors (GPCRs): the OR, V1R, and V2R/V2R-like receptors, the latter group belonging to the C family of GPCRs. These receptor families are thought to receive chemosensory information from a wide spectrum of odorant and pheromonal cues that influence critical animal behaviors such as feeding, reproduction and other social interactions.

Results: Using genome database mining and other informatics approaches, we identified and characterized the repertoire of 54 intact "V2R-like" olfactory C family GPCRs in the zebrafish. Phylogenetic analysis - which also included a set of 34 C family GPCRs from fugu - places the fish olfactory receptors in three major groups, which are related to but clearly distinct from other C family GPCRs, including the calcium sensing receptor, metabotropic glutamate receptors, GABA-B receptor, T1R taste receptors, and the major group of V2R vomeronasal receptor families. Interestingly, an analysis of sequence conservation and selective pressure in the zebrafish receptors revealed the retention of a conserved sequence motif previously shown to be required for ligand binding in other amino acid receptors.

Conclusion: Based on our findings, we propose that the repertoire of zebrafish olfactory C family GPCRs has evolved to allow the detection and discrimination of a spectrum of amino acid and/or amino acid-based compounds, which are potent olfactory cues in fish. Furthermore, as the major groups of fish receptors and mammalian V2R receptors appear to have diverged significantly from a common ancestral gene(s), these receptors likely mediate chemosensation of different classes of chemical structures by their respective organisms.

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Sites under positive and negative selection in OlfC coding sequences. A schematic representation of site-by-site selective pressure is shown on the OlfCa1 receptor sequence. Nucleotide alignments were generated from the corresponding amino acid alignment [see Additional file 4]. SLAC analysis shows the probability of sites being under selective pressure (positive selection shown in red (p < 0.1) or orange (p < 0.2), neutral selection in yellow and negative selection in blue-green (p < 0.2) or blue (p < 0.1). The  hypothesis is that a site is neutrally evolving with dN/dS = 1.
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Figure 7: Sites under positive and negative selection in OlfC coding sequences. A schematic representation of site-by-site selective pressure is shown on the OlfCa1 receptor sequence. Nucleotide alignments were generated from the corresponding amino acid alignment [see Additional file 4]. SLAC analysis shows the probability of sites being under selective pressure (positive selection shown in red (p < 0.1) or orange (p < 0.2), neutral selection in yellow and negative selection in blue-green (p < 0.2) or blue (p < 0.1). The hypothesis is that a site is neutrally evolving with dN/dS = 1.

Mentions: Figure 7 shows the probability for each codon site being under positive or negative selection (dN/dS values different than dN/dS = 1.0) on a snake plot of a representative OlfC amino acid sequence, OlfCa1. By this analysis, only one site, M436 in OlfCa1, appears to be under positive selection (dN/dS >1 with p < 0.1). It is unclear what role this position may play in receptor function. Based on existing models of C family GPCR structure [49,61], this site resides within or near the hinge of the ligand-binding clamshell. The apparent positive selection acting on this site may therefore indicate its importance in modulating some aspect of ligand binding or receptor activation. It is also possible that the identification of this site represents a false positive from this analysis.


The repertoire of olfactory C family G protein-coupled receptors in zebrafish: candidate chemosensory receptors for amino acids.

Alioto TS, Ngai J - BMC Genomics (2006)

Sites under positive and negative selection in OlfC coding sequences. A schematic representation of site-by-site selective pressure is shown on the OlfCa1 receptor sequence. Nucleotide alignments were generated from the corresponding amino acid alignment [see Additional file 4]. SLAC analysis shows the probability of sites being under selective pressure (positive selection shown in red (p < 0.1) or orange (p < 0.2), neutral selection in yellow and negative selection in blue-green (p < 0.2) or blue (p < 0.1). The  hypothesis is that a site is neutrally evolving with dN/dS = 1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1764893&req=5

Figure 7: Sites under positive and negative selection in OlfC coding sequences. A schematic representation of site-by-site selective pressure is shown on the OlfCa1 receptor sequence. Nucleotide alignments were generated from the corresponding amino acid alignment [see Additional file 4]. SLAC analysis shows the probability of sites being under selective pressure (positive selection shown in red (p < 0.1) or orange (p < 0.2), neutral selection in yellow and negative selection in blue-green (p < 0.2) or blue (p < 0.1). The hypothesis is that a site is neutrally evolving with dN/dS = 1.
Mentions: Figure 7 shows the probability for each codon site being under positive or negative selection (dN/dS values different than dN/dS = 1.0) on a snake plot of a representative OlfC amino acid sequence, OlfCa1. By this analysis, only one site, M436 in OlfCa1, appears to be under positive selection (dN/dS >1 with p < 0.1). It is unclear what role this position may play in receptor function. Based on existing models of C family GPCR structure [49,61], this site resides within or near the hinge of the ligand-binding clamshell. The apparent positive selection acting on this site may therefore indicate its importance in modulating some aspect of ligand binding or receptor activation. It is also possible that the identification of this site represents a false positive from this analysis.

Bottom Line: Interestingly, an analysis of sequence conservation and selective pressure in the zebrafish receptors revealed the retention of a conserved sequence motif previously shown to be required for ligand binding in other amino acid receptors.Based on our findings, we propose that the repertoire of zebrafish olfactory C family GPCRs has evolved to allow the detection and discrimination of a spectrum of amino acid and/or amino acid-based compounds, which are potent olfactory cues in fish.Furthermore, as the major groups of fish receptors and mammalian V2R receptors appear to have diverged significantly from a common ancestral gene(s), these receptors likely mediate chemosensation of different classes of chemical structures by their respective organisms.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Molecular and Cell Biology, Functional Genomics Laboratory, and Helen Wills Neuroscience Institute, University of California, Berkeley, California 94720, USA. talioto@imim.es <talioto@imim.es>

ABSTRACT

Background: Vertebrate odorant receptors comprise at least three types of G protein-coupled receptors (GPCRs): the OR, V1R, and V2R/V2R-like receptors, the latter group belonging to the C family of GPCRs. These receptor families are thought to receive chemosensory information from a wide spectrum of odorant and pheromonal cues that influence critical animal behaviors such as feeding, reproduction and other social interactions.

Results: Using genome database mining and other informatics approaches, we identified and characterized the repertoire of 54 intact "V2R-like" olfactory C family GPCRs in the zebrafish. Phylogenetic analysis - which also included a set of 34 C family GPCRs from fugu - places the fish olfactory receptors in three major groups, which are related to but clearly distinct from other C family GPCRs, including the calcium sensing receptor, metabotropic glutamate receptors, GABA-B receptor, T1R taste receptors, and the major group of V2R vomeronasal receptor families. Interestingly, an analysis of sequence conservation and selective pressure in the zebrafish receptors revealed the retention of a conserved sequence motif previously shown to be required for ligand binding in other amino acid receptors.

Conclusion: Based on our findings, we propose that the repertoire of zebrafish olfactory C family GPCRs has evolved to allow the detection and discrimination of a spectrum of amino acid and/or amino acid-based compounds, which are potent olfactory cues in fish. Furthermore, as the major groups of fish receptors and mammalian V2R receptors appear to have diverged significantly from a common ancestral gene(s), these receptors likely mediate chemosensation of different classes of chemical structures by their respective organisms.

Show MeSH