Regulation of Digestion in Blood-Sucking Insects

描述(申请人提供)：在蚊子中，将血粉中的蛋白质转化为卵黄蛋白和脂肪，以供发育中的卵母细胞使用，是繁殖周期的重要组成部分。雌性埃及伊蚊的吸血会在中肠、脂肪体和卵巢中引发一系列事件。雌性蚊子在短时间内摄取超过自身体重的血液，然后在接下来的36小时内将血液蛋白质中的氨基酸转化为卵子的成分，这一过程被称为卵黄发生。这一过程始于中肠，消化血粉蛋白，中肠消化酶合成的调节分两个阶段进行。早期阶段在进食后立即开始，涉及到翻译的激活。早期胰酶的合成为这一阶段提供了一个模型。晚期在进餐后6-8小时开始，涉及转录的激活。晚期胰酶的合成可以作为这一阶段的模型。在这项提案中，我们寻求资金继续研究雌性蚊子中肠在吸血后消化酶合成的调节机制。我们提出了以下两个特定的目标：1.研究蛋白质餐后早期胰酶mRNA翻译的激活机制。在血餐后的前30分钟内，全身提取物中存在一种多肽或小分子，这使得体外中肠制剂能够胜任早期胰酶翻译。30分钟后，在中肠启动了一个磷酸化级联反应，从而激活了早期胰酶的翻译。我们建议分离和表征诱导中肠翻译能力的因素，并表征导致早期胰酶翻译激活的信号传递过程。我们还建议研究内质网轮状结构在调节中肠分泌蛋白质合成中的作用。2.研究晚期胰蛋白酶基因的转录调控机制。摄食后约6小时，中肠胰蛋白酶晚期转录启动。我们最近发现，蜕皮激素和一种存在于喂食蚊子脂肪体提取液中的未知因子，参与了晚期胰酶基因的诱导。我们拟对蜕皮激素调节晚期胰酶表达的机制进行研究，并确定脂肪体因子和磷脂酰肌醇3-激酶(PI-3K)信号在调控晚期胰酶转录中的作用。

DESCRIPTION (provided by applicant): In mosquitoes, the conversion of protein from a blood meal into yolk proteins and lipids for the developing oocytes is an essential part of the reproductive cycle. Blood feeding by a female Aedes aegypti mosquito initiates a series of events in the midgut, the fat body and the ovaries. Female mosquitoes ingest more than their own weight in blood in a short time and then spend the next 36 hours converting the amino acids from the blood proteins into the constituents of their eggs, a process termed vitellogenesis. The process begins in the midgut with the digestions of blood meal proteins and the regulation of digestive enzyme synthesis in the midgut occurs in two phases. The early phase begins immediately after ingestion of the meal and involves activation of translation. The synthesis of early trypsin serves as a model for this phase. The late phase begins 6-8 hours after the meal and involves activation of transcription. The synthesis of late trypsin serves as a model for this phase. In this proposal we seek funds to continue work on the mechanism of regulation of digestive enzyme synthesis in the female mosquito midgut following a blood meal. We propose the following two specific aims: 1. Investigate the mechanism of activation of translation of the early trypsin mRNA following a protein meal. During the first 30 minutes following a blood meal, a peptide or small molecule is present in whole body extracts, which makes an in vitro midgut preparation competent for early trypsin translation. After 30 minutes, a phosphorylation cascade is initiated in the midgut which leads to activation of translation of early trypsin. We propose to isolate and characterize the factor that induces translational competency in the midgut, and to characterize the signaling processes that lead to activation of early trypsin translation. We also propose to investigate the role of the endoplasmic reticulum whorls in regulating secretory protein synthesis in the midgut. 2. Investigate the mechanism of transcriptional regulation of the late trypsin gene. About 6 hours after feeding, late trypsin transcription in the midgut is initiated. We have recently found that ecdysone, and an uncharacterized factor present in extracts prepared from fat bodies of fed mosquitoes, are involved in late trypsin gene induction. We propose to characterize the mechanism of ecdysone regulation of late trypsin expression, and to identify the fat body factor and the role of phosphoinositide 3-kinase (PI-3K) signaling in modulating late trypsin transcription.