Roles of Retromer Complex in Development

描述（由申请人提供）：该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。Retromer是一种进化上保守的多亚基复合物，由两个复合物组成，即货物识别Vps26-Vps29- Vps35异源三聚体和膜靶向异源二聚体或同源二聚体。酵母和哺乳动物细胞培养的早期研究已经证明了它在介导几种蛋白质的内体高尔基体运输中的作用，包括哺乳动物阳离子非依赖性甘露糖-6-磷酸受体。然而，直到最近才对后转录复合体在发育中的作用进行了研究。我们最近的研究发现了反转录复合物在Wnt分泌中的重要作用。我们发现逆转录酶参与了Wntless （Wls）的内体到高尔基体的转运，wnnt是一种分泌Wnt所需的七通跨膜蛋白。在缺乏逆转录酶活性的情况下，Wls不稳定并被降解，从而导致Wnt分泌缺陷。重要的是，虽然逆转录酶不参与许多其他发育信号通路，但我们发现逆转录酶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crumb （crb）的转运来控制上皮的顶基极性，同时参与调节Toll/Dorsal信号通路来控制造血。因此，我们的研究揭示了后转录复合体在发育中的三个重要作用。在本研究中，我们将进一步研究逆转录酶在Wnt分泌、顶基底极性控制和Toll/背侧信号通路中的作用。在目的1中，我们将研究泛素化和逆转录酶在调节Wls稳定性和循环中的作用。在目的2中，我们将研究retromer是否通过调节Crumb的运输和稳定性来控制上皮极性。在Aim3中，我们将确定retromer调节Toll贩运和信令的机制。总之，我们提出的研究将为retromer在发育过程中调节Wnt分泌、上皮极性和Toll/dorsal信号传导的机制提供新的见解。

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.