Institut de recherches cliniques de Montréal, 110 Pine Avenue West, Montreal H2W 1R7, QC, Canada.
Department of Biology, McGill University, Montreal H3A 1B1, QC, Canada.
Development. 2021 Apr 1;148(7). doi: 10.1242/dev.189258. Epub 2021 Apr 15.
Hedgehog (Hh) ligands orchestrate tissue patterning and growth by acting as morphogens, dictating different cellular responses depending on ligand concentration. Cellular sensitivity to Hh ligands is influenced by heterotrimeric G protein activity, which controls production of the second messenger 3',5'-cyclic adenosine monophosphate (cAMP). cAMP in turn activates Protein kinase A (PKA), which functions as an inhibitor and (uniquely in Drosophila) as an activator of Hh signalling. A few mammalian Gαi- and Gαs-coupled G protein-coupled receptors (GPCRs) have been shown to influence Sonic hedgehog (Shh) responses in this way. To determine whether this is a more-general phenomenon, we carried out an RNAi screen targeting GPCRs in Drosophila. RNAi-mediated depletion of more than 40% of GPCRs tested either decreased or increased Hh responsiveness in the developing Drosophila wing, closely matching the effects of Gαs and Gαi depletion, respectively. Genetic analysis indicated that the orphan GPCR Mthl5 lowers cAMP levels to attenuate Hh responsiveness. Our results identify Mthl5 as a new Hh signalling pathway modulator in Drosophila and suggest that many GPCRs may crosstalk with the Hh pathway in mammals.
刺猬 (Hh) 配体通过作为形态发生素发挥作用，协调组织模式和生长，根据配体浓度决定不同的细胞反应。细胞对 Hh 配体的敏感性受异三聚体 G 蛋白活性的影响，该活性控制第二信使 3'，5'-环腺苷单磷酸 (cAMP) 的产生。cAMP 反过来激活蛋白激酶 A (PKA)，PKA 作为 Hh 信号通路的抑制剂（在果蝇中是唯一的）和激活剂。已经表明，一些哺乳动物 Gαi 和 Gαs 偶联的 G 蛋白偶联受体 (GPCR) 以这种方式影响 Sonic hedgehog (Shh) 反应。为了确定这是否是一种更为普遍的现象，我们针对果蝇中的 GPCR 进行了 RNAi 筛选。在发育中的果蝇翅膀中，超过 40%的 GPCR 的 RNAi 介导消耗要么降低要么增加了 Hh 反应性，分别与 Gαs 和 Gαi 消耗的效果非常匹配。遗传分析表明，孤儿 GPCR Mthl5 降低 cAMP 水平以减弱 Hh 反应性。我们的结果将 Mthl5 鉴定为果蝇中 Hh 信号通路的新调节剂，并表明许多 GPCR 可能在哺乳动物中与 Hh 途径发生串扰。
