Abstract
Pheromone receptors (PRs) recognize specific pheromone compounds to guide the behavioral outputs of insects, which are the most diverse group of animals on earth. The activation of PRs is known to couple to the calcium permeability of their coreceptor (Orco) or putatively with G proteins; however, the underlying mechanisms of this process are not yet fully understood. Moreover, whether this transverse seven transmembrane domain (7TM)-containing receptor is able to couple to arrestin, a common effector for many conventional 7TM receptors, is unknown. Herein, using the PR BmOR3 from the silk moth Bombyx mori and its coreceptor BmOrco as a template, we revealed that an agonist-induced conformational change of BmOR3 was transmitted to BmOrco through transmembrane segment 7 from both receptors, resulting in the activation of BmOrco. Key interactions, including an ionic lock and a hydrophobic zipper, are essential in mediating the functional coupling between BmOR3 and BmOrco. BmOR3 also selectively coupled with Gi proteins, which was dispensable for BmOrco coupling. Moreover, we demonstrated that trans-7TM BmOR3 recruited arrestin in an agonist-dependent manner, which indicates an important role for BmOR3–BmOrco complex formation in ionotropic functions. Collectively, our study identified the coupling of G protein and arrestin to a prototype trans-7TM PR, BmOR3, and provided important mechanistic insights into the coupling of active PRs to their downstream effectors, including coreceptors, G proteins, and arrestin.
Highlights
Pheromone receptors (PRs) recognize specific pheromone compounds to guide the behavioral outputs of insects, which are the most diverse group of animals on earth
By using a genetically encoded BRET-based calcium sensor composed of Venus, troponin, and NanoLuc, we investigated the signaling properties of the BmOR3–BmOrco pair by expressing these receptors in heterologous human embryonic kidney 293 (HEK293) cells [23]
We found that the coexpression of BmOR3 and BmOrco in HEK293 cells, but not the expression of BmOR3 or BmOrco alone, elicited robust calcium influx in response to stimulation with the specific BmOR3 agonist bombykal (Fig. 1B)
Summary
Pheromone receptors (PRs) recognize specific pheromone compounds to guide the behavioral outputs of insects, which are the most diverse group of animals on earth. Consistent with the results of G protein recruitment assay, the bombykal induced dosedependent Gi activation through BmOR3 as revealed by the mutants were compared with cells transfected with WT receptors.
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