Abstract：
The prothoracic gland (PG) is the source of ecdysteoids in larval insects. Although numerous studies have been conducted on signaling networks involved in prothoracicotropic hormone (PTTH)-stimulated ecdysteroidogenesis in PGs, less is known about regulation of metabolism in PGs. In the present study, we investigated correlations between expressions of sugar transporter (St)/trehalase (Treh) genes and PTTH-stimulated ecdysteroidogenesis in Bombyx mori PGs. Our results showed that in vitro PTTH treatment stimulated expression of the St1 gene, but not other transporter genes. Expression of the Treh1 gene was also stimulated by PTTH treatment. An immunoblotting analysis showed that St1 protein levels in Bombyx PGs increased during the later stage of the last larval instar and were not affect by PTTH treatment. PTTH treatment enhanced Treh enzyme activity in a time-dependent manner. Blocking either extracellular signal-regulated kinase (ERK) signaling with U0126 or phosphatidylinositol 3-kinase (PI3K) signaling with LY294002 decreased PTTH-stimulated Treh enzyme activity, indicating a link from the ERK and PI3K signaling pathways to Treh activity. Treatment with the Treh inhibitor, validamycin A, blocked PTTH-stimulated Treh enzyme activity and partially inhibited PTTH-stimulated ecdysteroidogenesis. Treatment with either a sugar transport inhibitor (cytochalasin B) or a specific glycolysis inhibitor (2-deoxy-D-glucose, 2-DG) partially inhibited PTTH-stimulated ecdysteroidogenesis. Taken together, these results indicate that increased expressions of St1/Treh1 and Treh activity, which lie downstream of PTTH signaling, are involved in PTTH stimulation in B. mori PGs.
摘要：
前胸腺（PG）是幼虫昆虫中类外皮的来源。尽管已经对参与PGs中促胸激素（PTTH）刺激的蜕皮类固醇生成的信号网络进行了大量研究，对PG中代谢的调节知之甚少。在本研究中,我们研究了糖转运蛋白（St）/海藻糖酶（Treh）基因的表达与家蚕PGs中PTTH刺激的蜕皮类固醇发生之间的相关性。我们的结果表明，体外PTTH处理刺激St1基因的表达，但不是其他转运基因。PTTH处理也刺激了Treh1基因的表达。免疫印迹分析表明，家蚕PGs中的St1蛋白水平在最后一个幼虫龄后期增加，并且不受PTTH处理的影响。PTTH处理以时间依赖性方式增强Treh酶活性。用U0126阻断细胞外信号调节激酶（ERK）信号或LY294002阻断磷脂酰肌醇3激酶（PI3K）信号降低PTTH刺激的Treh酶活性，表明ERK和PI3K信号通路与Treh活性的联系。用Treh抑制剂治疗，有效霉素A,阻断PTTH刺激的Treh酶活性，并部分抑制PTTH刺激的蜕皮类固醇生成。用糖转运抑制剂（细胞松弛素B）或特定的糖酵解抑制剂（2-脱氧-D-葡萄糖，2-DG）部分抑制PTTH刺激的蜕皮类固醇生成。一起来看,这些结果表明，St1/Treh1和Treh活性的表达增加，位于PTTH信号的下游，参与B.moriPG中的PTTH刺激。
