A Genetic RNAi Screen for IP₃/Ca²⁺ Coupled GPCRs in <i>Drosophila</i> Identifies the PdfR as a Regulator of Insect Flight

Insect flight is regulated by various sensory inputs and neuromodulatory circuits which function in synchrony to control and fine-tune the final behavioral outcome. The cellular and molecular bases of flight neuromodulatory circuits are not well defined. In Drosophila melanogaster, it is known that neuronal IP3 receptor mediated Ca2+ signaling and store-operated Ca2+ entry (SOCE) are required for air-puff stimulated adult flight. However, G-protein coupled receptors (GPCRs) that activate intracellular Ca2+ signaling in the context of flight are unknown in Drosophila. We performed a genetic RNAi screen to identify GPCRs that regulate flight by activating the IP3 receptor. Among the 108 GPCRs screened, we discovered 5 IP3/Ca2+ linked GPCRs that are necessary for maintenance of air-puff stimulated flight. Analysis of their temporal requirement established that while some GPCRs are required only during flight circuit development, others are required both in pupal development as well as during adult flight. Interestingly, our study identified the Pigment Dispersing Factor Receptor (PdfR) as a regulator of flight circuit development and as a modulator of acute flight. From the analysis of PdfR expressing neurons relevant for flight and its well-defined roles in other behavioral paradigms, we propose that PdfR signaling functions systemically to integrate multiple sensory inputs and modulate downstream motor behavior.昆虫飞行受多种感官输入与神经调节环路协同调控，以精准控制并微调最终的行为输出。目前，飞行神经调节环路的细胞与分子基础尚未得到清晰阐明。在黑腹果蝇(Drosophila melanogaster)中，已有研究证实神经元内肌醇三磷酸受体(IP3 receptor)介导的钙信号通路与钙池操控性钙内流(store-operated Ca2+ entry, SOCE)是气流刺激诱导成虫飞行所必需的。然而，在果蝇体内，能够在飞行过程中激活胞内钙信号的G蛋白偶联受体(G-protein coupled receptors, GPCRs)仍未被鉴定。我们通过遗传RNA干扰筛选(RNAi screen)，旨在筛选出通过激活肌醇三磷酸受体来调控飞行行为的GPCRs。在本次筛选的108种GPCRs中，我们共发现5种与肌醇三磷酸/钙信号通路相关的GPCRs，它们对维持气流刺激诱导的飞行行为不可或缺。对其时间依赖性需求的分析结果显示，部分GPCRs仅在飞行环路发育阶段发挥调控作用，而另一些则在蛹发育阶段及成虫飞行期均为必需。值得注意的是，本研究鉴定出色素分散因子受体(Pigment Dispersing Factor Receptor, PdfR)，其既是飞行环路发育的调控因子，也是急性飞行行为的调节分子。结合对与飞行相关的表达PdfR的神经元的分析，以及该受体在其他行为范式中已明确的功能，我们提出：PdfR信号通路可通过系统性整合多种感官输入，对下游运动行为进行调控。