Bil Magdalena, Timmermans Iris, Verlinden Heleen, Huybrechts Roger
Research Group of Insect Physiology and Molecular Ethology, KU Leuven, Naamsestraat 59, B-3000, Belgium.
Research Group of Molecular Developmental Physiology and Signal Transduction, KU Leuven, Naamsestraat 59, B-3000, Belgium.
J Insect Physiol. 2016 Jun;89:52-9. doi: 10.1016/j.jinsphys.2016.04.001. Epub 2016 Apr 7.
Adipokinetic hormone (AKH) is an insect neuropeptide mainly involved in fat body energy mobilization. In flies (Phormia regina, Sarcophaga crassipalpis), bugs (Pyrrhocoris apterus) and cockroaches (Periplaneta americana) AKH was also demonstrated to be involved in the regulation of digestion. This makes AKH an important peptide for anautogenous female flies that need to feed on a supplementary protein meal to initiate vitellogenesis, the large scale synthesis of yolk proteins and their uptake by the developing oocytes. Flesh fly AKH, originally identified as Phormia terraenovae hypertrehalosemic hormone (PhoteHrTH), functions through activation of the AKH receptor (AKHR). This is a G protein-coupled receptor that is the orthologue of the human gonadotropin-releasing hormone receptor. Pharmacological characterization indicated that the receptor can be activated by two related dipteran AKH ligands with an EC50 value in the low nanomolar range, whereas micromolar concentrations of the Tribolium castaneum AKH were needed. Consistent with the energy mobilizing function of AKH, the receptor transcript levels were most abundant in the fat body tissue. Nonetheless, Sarcophaga crassipalpis AKHR transcript levels were also high in the brain, the foregut and the hindgut. Interestingly, the receptor transcript numbers were reduced in almost all measured tissues after protein feeding. These changes may enforce the use of ingested energy carrying molecules prior to stored energy mobilization.
脂肪动素（AKH）是一种昆虫神经肽，主要参与脂肪体的能量动员。在苍蝇（丽蝇、肥须亚麻蝇）、椿象（红蝽）和蟑螂（美洲大蠊）中，AKH也被证明参与消化调节。这使得AKH对于非自体生殖的雌蝇来说是一种重要的肽，这些雌蝇需要摄取补充性蛋白质餐来启动卵黄发生，即大规模合成卵黄蛋白并被发育中的卵母细胞摄取。麻蝇AKH最初被鉴定为新陆原伏蝇高海藻糖激素（PhoteHrTH），通过激活AKH受体（AKHR）发挥作用。这是一种G蛋白偶联受体，是人类促性腺激素释放激素受体的直系同源物。药理学特性表明，该受体可被两种相关的双翅目AKH配体激活，其半数有效浓度（EC50）在低纳摩尔范围内，而栗色拟谷盗AKH则需要微摩尔浓度。与AKH的能量动员功能一致，受体转录水平在脂肪体组织中最为丰富。尽管如此，肥须亚麻蝇AKHR转录水平在脑、前肠和后肠中也很高。有趣的是，喂食蛋白质后，几乎所有测量组织中的受体转录数量都减少了。这些变化可能会促使在动员储存能量之前先使用摄入的携带能量的分子。
