Topological and Functional Characterization of an Insect Gustatory Receptor

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Zhang, Hui jie; Anderson, Alisha; Trowell, Stephen; Luo, A-Rong; Xiang, Zhong-Huai; Xia, Qing-You


2011-08-29


Journal Article


PLoS ONE


6


8


e24111


Recently, many insect gustatory receptors have been identified following whole genome sequencing of several insect species. Also, functional studies on a handful of gustatory receptors from Drosophila melanogaster have provided insights into the molecular mechanisms of gustation in insects. However, except for these few examples from Drosophila, the function of individual insect gustatory receptors remains unknown as does the topology of any insect gustatory receptor. In this study, the total number of identified gustatory receptors in Bombyx mori was expanded from 65 to 69. BmGr8, a silkmoth gustatory receptor from the sugar receptor GR subfamily, was expressed in Sf9 cells and a functional assay was performed to test potential ligands. BmGr8 functioned independently in this system and showed concentration-dependent responses to the polyalcohols myo-inositol and epi-inositol, within or close to the naturally occurring range for myo-inositol. BmGr8 did not respond to allo-inositol nor to a range of common mono- and disaccharides. BmGr8 is the first chemoreceptor to be shown to respond specifically to inositol, which is an important or essential nutrient at least for some Lepidoptera. The selectivity of BmGr8 responses is consistent with the known responses of one of the gustatory receptor neurons in the lateral styloconic sensilla of B. mori, which responds to myo-inositol and epi-inositol but not to allo-inositol. Membrane topology studies on BmGr8 indicate that it has an inverted topology relative to G protein-coupled receptors. Experiments with BmGr53, an orphan Gr from the bitter receptor family, yielded similar results. We infer, from the finding that two distantly related BmGrs have an intracellular N-terminus and an odd number of transmembrane spans, that this is likely to be the general topology for all insect gustatory receptors. This would be consistent with the proposal that insect ORs evolved as a subclade within the insect GR family.


Public Library of Science


Biological Sciences not elsewhere classified


Accepted Version (pdf) (761KB)


https://doi.org/10.1371/journal.pone.0024111


Link to Publisher's Version


© 2011 Zhang et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


EP112125


Journal article - Refereed


English


Zhang, Hui jie; Anderson, Alisha; Trowell, Stephen; Luo, A-Rong; Xiang, Zhong-Huai; Xia, Qing-You. Topological and Functional Characterization of an Insect Gustatory Receptor. PLoS ONE. 2011; 6(8):e24111. https://doi.org/10.1371/journal.pone.0024111



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