Mechanisms and function of endosome-derived tubular carriers

内吞运输是正常细胞功能的核心，并且失调是内吞运输的根本原因。 动脉粥样硬化、糖尿病和癌症等多种疾病。我的实验室为 了解膜和受体通过内吞作用再循环的机制 再循环隔室（ERC）至质膜（PM）。内吞再循环仍然是 研究内吞途径;特别是，在回收过程中膜小管的参与， 了解甚少，以及各种形式的管状内体的作用，以及 这些结构的产生和经历囊泡化仍然是一个主要的未回答的问题。有 多种“类型”的内体衍生的管状载体（EDTC），包括分选连接蛋白-BAR（SNX-BAR） 结构域和逆转录衍生的小管，以及内体小管的网络，如小管再循环 由MICAL-L1、Syndapin 2（Synd 2）和Eps 15同源结构域（EHD）修饰的内体（TRE） proteins.很少有人知道这些明显不同的EDTC如何整合它们的功能，甚至 retromer和SXN-BAR EDTC是否与TRE不同。最近的研究表明，EHD 蛋白质和MICAL-L1与逆转录复合物的组分相互作用，这表明这些小管 网络是相关的。我们的中心假设是，重叠和不同的管状膜协调 从内体运输到PM和高尔基体。在本提案中，我们将揭示功能和 TRE、retromer和SNX-BAR衍生的EDTC之间的物理关系。此外，我们将集中在一个 对EDTC产生模式的机械理解，以及它们如何进行囊泡化 来促进细胞内的运输。目的1：探讨EDTC的关系和功能作用。 管状内体在内吞膜运输中起主要作用。EDTC包括一些 含有逆转录酶的结构，SNX-BAR结构域蛋白产生的逆转录酶非依赖性小管， 和由MICAL-L1、BAR结构域蛋白Synd 2和EHD蛋白修饰的TRE。我们会研究 这些途径的相互影响和相互调节， 小管和内吞再循环的控制。目的2：定义和阐明时空 TRE生物发生和囊泡形成的调控和机制。我们的假设是 磷脂酸的产生导致膜中心、MICAL-L1和F-BAR蛋白的募集 Synd 2，用于生成和改造TRE。我们进一步假设EHD 3在这一过程中起着重要作用。 通过稳定MICAL-L1-Synd 2相互作用来实现。我们对细胞、细胞器、分子和细胞周期的研究， 原子水平将使用从结构生物学到超分辨率显微镜的技术， 生物物理囊泡形成试验，提供了对知之甚少的 TRE和retromer-SNX-BAR衍生的小管，以及它们的生物发生和囊泡形成。

Endocytic trafficking is central to normal cell function, and dysregulation is the underlying cause for diseases as diverse as atherosclerosis, diabetes and cancer. My laboratory has contributed to understanding the mechanisms by which membranes and receptors are recycled via the endocytic recycling compartment (ERC) to the plasma membrane (PM). Endocytic recycling remains one of the least studied endocytic pathways; in particular, the involvement of membrane tubules in the recycling process is poorly understood, and the roles of the various forms of tubular endosomes, and the mechanisms by which these structures are generated and undergo vesiculation remain a major unanswered question. There are multiple `types' of endosome-derived tubular carriers (EDTC), including sorting nexin-BAR (SNX-BAR) domain and retromer-derived tubules, and networks of endosomal tubules, such as tubular recycling endosomes (TRE) decorated by MICAL-L1, Syndapin2 (Synd2) and Eps15 Homology Domain (EHD) proteins. Little is known about how these apparently different EDTC integrate their functions, or even whether retromer and SXN-BAR EDTC are distinct from TRE. Recent studies demonstrate that EHD proteins and MICAL-L1 interact with components of the retromer complex, suggesting that these tubular networks are related. Our central hypothesis is that overlapping and distinct tubular membranes coordinate transport from endosomes to the PM and the Golgi. In this proposal, we will uncover the functional and physical relationships between TRE, retromer and SNX-BAR-derived EDTC. Moreover, we will focus on a mechanistic understanding of the mode by which EDTC are generated, and how they undergo vesiculation to promote transport within the cell. Aim 1: To examine the relationship and functional roles of EDTC. Tubular endosomes play major roles in endocytic membrane trafficking. EDTC include a number of retromer-containing structures, retromer-independent tubules generated by SNX-BAR domain proteins, and TRE decorated by MICAL-L1, the BAR domain protein Synd2, and EHD proteins. We will examine the cross-talk and cross-regulation of these pathways with regard to the generation and fission of recycling tubules, and the control of endocytic recycling. Aim 2: To define and elucidate the spatio-temporal regulation and mechanism of TRE biogenesis and vesiculation. Our working hypothesis is that phosphatidic acid generation leads to recruitment of the membrane hub, MICAL-L1 and the F-BAR protein Synd2, to generate and remodel TRE. We further hypothesize that EHD3 plays an essential role in this process by stabilizing MICAL-L1-Synd2 interactions. Our studies on the cellular, organellar, molecular and atomic levels will use techniques ranging from structural biology to super-resolution microscopy and novel biophysical vesiculation assays, providing crucial knowledge of the functional role of the poorly understood TRE and retromer-SNX-BAR derived tubules, and their biogenesis and vesiculation.