Can BRET-based biosensors be used to characterize G-protein mediated signaling pathways of an insect GPCR, the Schistocerca gregaria CRF-related diuretic hormone receptor?

G protein-coupled receptors (GPCRs) are membrane-bound receptors that are considered prime candidates for the development of novel insect pest management strategies. However, the molecular signaling properties of insect GPCRs remain poorly understood. In fact, most studies on insect GPCR signaling are limited to analysis of fluctuations in the secondary messenger molecules calcium (Ca2+) and/or cyclic adenosine monophosphate (cAMP). In the current study, we characterized a corticotropin-releasing factor-related diuretic hormone (CRF-DH) receptor of the desert locust, Schistocerca gregaria. This Schgr-CRF-DHR is mainly expressed in the nervous system and in brain-associated endocrine organs. The neuropeptide Schgr-CRF-DH induced Ca2+-dependent aequorin-based bioluminescent responses in CHO cells co-expressing this receptor with the promiscuous G alpha(16) protein. Furthermore, when co-expressed with the cAMP-dependent bioluminescence resonance energy transfer (BRET)-based CAMYEL biosensor in HEK293T cells, this receptor elicited dose-dependent agonist-induced responses with an EC50 in the nanomolar range (4.02 nM). In addition, we tested if vertebrate BRET-based G protein biosensors, can also be used to detect direct G alpha protein subunit activation by an insect GPCR. Therefore, we analyzed ten different human BRET-based G protein biosensors, representing members of all four G alpha protein subfamilies; G alpha(s), G alpha(i/o), G alpha(q/11) and G alpha(12/13). Our data demonstrate that stimulation of Schgr-CRF-DHR by Schgr-CRF-DH can dose-dependently activate G alpha(i/o) and G alpha(s) biosensors, while no significant effects were observed with the G alpha(q/11) and G alpha(12/13) biosensors. Our study paves the way for future biosensor-based studies to analyze the signaling properties of insect GPCR5 in both fundamental science and applied research contexts.