Molecular mechanisms of autophagosome biogenesis

摘要 被称为自噬的分解代谢过程对于维持细胞健康和 清除细胞毒素，如异常的大分子，受损的细胞器，和侵入性 细菌自噬的标志是重新形成双膜囊泡， 自噬体这个过程开始于组装前体膜吞噬细胞 与内质网（ER）相邻，随后扩张成杯状 在细胞质的非选择性部分或选定的细胞毒素周围。在扩张过程中， 吞噬细胞的边缘保持与ER结合，并且在最后时刻， 合并，导致杯的关闭，从而产生完整的自噬体。的 自噬对细胞内稳态的贡献取决于吞噬细胞可以 吞噬降解底物。为了让噬菌体完成这项非凡的任务，它必须 扩大我们和其他人已经朝着理解分子生物学的目标取得了进展。 吞噬细胞扩张的机制，通过确定ATG 2的功能，最大的蛋白质， 自噬相关蛋白质组。我们研究了人类ATG2A， 这种蛋白质是一种杆状的膜系链，可以在膜之间转移脂质。 我们目前的工作模型是ATG2通过以下途径将脂质从ER转运到吞噬细胞： 把他们绑起来这些被转运的脂质将作为吞噬细胞的组成部分 围绕着基板。这项新提案旨在建立在这一模式的基础上， 对这一神秘过程的机械见解。在目标1中，我们将把我们对ATG 2的研究扩展到 确定其结构。目的是解释ATG2如何在膜之间转运脂质。 在目标2中，我们将关注ATG9，这是已知的自噬的整合膜蛋白， 作为ATG2的参与者。通过结构和生化特征，我们的目的是阐明 这种蛋白质的功能，并获得新的见解吞噬细胞扩张。在目标3中，我们 描述了ATG2和ATG9之间的相互作用。目标是确定这两个 蛋白质在结构水平上相互作用，并探讨蛋白质相互作用的意义。 ATG 2介导的脂质转移和吞噬细胞扩增的相互作用。从这些 这些研究将纵向推进我们对自噬体生物发生的分子水平的理解。 水平

Abstract The catabolic process known as autophagy is essential for the maintenance of cellular health and the removal of cytotoxins, such as aberrant macromolecules, damaged organelles, and invasive bacteria. The hallmark of autophagy is de novo formation of the double-membrane vesicle called autophagosome. The process begins with assembling the precursor membrane phagophore adjacent to the endoplasmic reticulum (ER), followed by its expansion into a cup-like shape around a non-selective portion of the cytoplasm or a selected cytotoxin. During the expansion, the edges of the phagophore remain associated with the ER and at the last moment, the edges merge, resulting in the closure of the cup, thereby producing a complete autophagosome. The contribution to cellular homeostasis by autophagy hinges on the fact that the phagophore can engulf degradation substrates. For the phagophore to achieve this remarkable task, it must expand. We and others have made progress toward the goal of understanding the molecular mechanism of phagophore expansion by determining the function of ATG2, the largest protein in the group of autophagy-related proteins. We have worked on human ATG2A and demonstrated that this protein is a rod-shaped membrane tether that can transfer lipids between membranes. Our current working model is that ATG2 transports lipids from the ER to the phagophore by tethering them. The transported lipids would then serve as the building blocks the phagophore built around the substrates. This new proposal aims to build on this model and gain further mechanistic insights into this enigmatic process. In Aim 1, we will extend our study of ATG2 to determine its structure. The goal is to explain how ATG2 transports lipids between membranes. In Aim 2, we will focus on ATG9, the integral membrane protein of autophagy that has been known as an ATG2 interactor. Through structural and biochemical characterizations, we aim to elucidate the function of this protein and gain new insights into phagophore expansion. In Aim 3, we will characterize the interaction between ATG2 and ATG9. The goal is to determine how these two proteins interact with each other at the structural level and explore the significance of the interaction for ATG2-mediated lipid transfer and phagophore expansion. Results from these studies will vertically advance our understanding of autophagosome biogenesis at the molecular level.