Roles of Retromer Complex in Development

描述（由申请人提供）：本项目的长期目标是了解逆转录酶在发育过程中控制细胞过程的分子机制。逆转录聚合物是一种进化上保守的多亚基复合物，由两种复合物组成，即货物识别Vps 26-Vps 29-Vps 35异源三聚体和膜靶向异源二聚体或同源二聚体。在酵母和哺乳动物细胞培养中的早期研究已经证明了其在介导包括哺乳动物阳离子非依赖性甘露糖-6-磷酸受体在内的几种蛋白质的内体-高尔基体运输中的作用。然而，retromer复合物在发育中的作用直到最近才被研究。我们最近的研究发现了逆转录酶复合物在Wnt分泌中的重要作用。我们发现，retromer参与Wnt分泌所需的Wnt无（Wls），一个七次跨膜蛋白的内体到高尔基体的运输。在不存在逆转录酶活性的情况下，Wls是不稳定的并且被降解，从而引起Wnt分泌缺陷。重要的是，虽然retromer不参与许多其他发育信号通路，但我们发现retromer对其他两个重要的发育过程至关重要，包括（1）果蝇胚胎发生期间上皮的顶基极性和（2）幼虫发育期间的造血。我们的初步研究表明，retromer通过调节Crumbs的运输来控制上皮细胞的顶基底极性，同时它还参与调节Toll/Dorsal信号通路来控制造血。因此，我们的研究揭示了retromer复合物在发育中的三个重要作用。在本申请中，我们将进一步研究retromer在Wnt分泌、顶基极性控制和Toll/背侧信号通路中的作用。在Aim 1中，我们将研究泛素化和逆转录酶在调节WLS稳定性和回收中的作用。在Aim 2中，我们将检查逆转录酶是否通过调节Crumb运输和稳定性来控制上皮极性。在Aim 3中，我们将确定逆转录酶调节Toll贩运和信号传导的机制。总之，我们提出的研究将提供新的见解retromer调节Wnt分泌，上皮极性和Toll/背信号在发展过程中的机制。 公共卫生相关性：Retromer控制Wnt和Toll信号通路以及上皮极性。这些信号通路和细胞生物学过程对胚胎发育至关重要。Wnt和Toll信号通路以及上皮极性的缺陷与许多人类疾病包括癌症相关。该应用的结果将有助于了解相关的人类疾病过程。

DESCRIPTION (provided by applicant): The long-term goal of this project is to understand the molecular mechanisms by which retromer controls cellular processes during development. Retromer is an evolutionarily conserved multi-subunit complex, consisting of two complexes, the cargo recognition Vps26-Vps29- Vps35 heterotrimer and a membrane-targeting heterodimer or homodimer. Early studies in yeast and mammalian cell culture have demonstrated its roles in mediating endosome-Golgi trafficking of several proteins including mammalian cation-independent mannose-6-phosphate receptor. However, the roles of retromer complex in development have not been examined until recently. Our recent studies have uncovered an essential role of retromer complex in Wnt secretion. We showed that retromer is involved in endosome-to-Golgi transport of Wntless (Wls), a seven-pass transmembrane protein required for Wnt secretion. In the absence of retromer activity, Wls is unstable and is degraded, thereby causing Wnt secretion defects. Importantly, while retromer is not involved in many other developmental signaling pathways, we found that retromer is crucial for other two essential developmental processes including (1) the apicobasal polarity of epithelium during Drosophila embryogenesis and (2) hematopoeisis during larval development. Our preliminary studies have demonstrated that retromer regulates the trafficking of Crumbs (crb) to control the apicobasal polarity of epithelium, while it is involved in regulating Toll/Dorsal signaling pathway to control hematopoeisis. Thus, our studies have uncovered three essential roles of the retromer complex in development. In this application, we will further investigate the roles of retromer in Wnt secretion, in the apicobasal polarity control and in Toll/dorsal signaling pathway. In Aim1, we will examine the roles of ubiquitination and retromer in regulating Wls stability and recycling. In Aim2, we will examine whether retromer controls epithelium polarity by regulating Crumb trafficking and stability. In Aim3, we will determine the mechanism by which retromer regulates Toll trafficking and signaling. Together, our proposed studies will provide new insights into the mechanisms by which retromer regulates Wnt secretion, epithelium polarity and Toll/dorsal signaling during development. PUBLIC HEALTH RELEVANCE: Retromer controls Wnt and Toll signaling pathways as well as epithelium polarity. These signaling pathways and cell biology processes are essential for embryonic development. Defects in Wnt and Toll signaling pathways as well as epithelium polarity are associated with many human diseases including cancers. The outcomes of this application will help understanding related human disease processes.