A structural perspective on insect gustatory receptors.

Across the animal kingdom, a remarkable diversity of chemoreceptors has evolved, reflecting the ecological and evolutionary pressures that shape species-specific sensory demands. Insects, the most biodiverse class of animals, play crucial roles in ecosystems and have an extensive chemosensory repertoire. At the heart of insect gustation lie the gustatory receptors (GRs), a large and remarkably diverse family of proteins characterized by their seven-transmembrane domain structure and tetrameric stoichiometry. These receptors are phylogenetically distinct from the taste receptors present in most other animal groups, including mammals. Functionally, GRs operate as ligand-gated cation channels. Upon binding to specific chemical compounds (tastants), these receptors undergo conformational changes that lead to the opening of ion-conducting channels in the neuronal membrane, ultimately triggering neuronal activation and initiating the perception of taste. Recent advancements in structural biology, particularly the use of cryo-electron microscopy, have enabled the visualization of the three-dimensional structure of several insect GRs that detect sugars. These structures, in unbound and ligand-bound states, have begun to reveal the principles of sugar recognition and discrimination. Here, we highlight recent advances in our understanding of insect GRs.