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的 细菌。自噬的标志是双膜泡的从头形成，称为 自噬小体。该过程从组装前体膜噬菌体开始。 毗邻内质网，随后扩张为杯状 围绕细胞质的非选择性部分或选定的细胞毒素。在扩张过程中， 噬菌体的边缘仍然与内质网相关联，在最后一刻，边缘 合并，导致杯子关闭，从而产生完整的自噬小体。这个 自噬对细胞动态平衡的贡献取决于这样一个事实，即吞噬体能 吞噬降解底物。吞噬动物要完成这项非凡的任务，它必须 扩张。我们和其他人已经朝着理解分子的目标取得了进展 通过确定吞噬细胞中最大的蛋白质ATG2的功能来研究吞噬细胞扩张的机制 一组与自噬相关的蛋白质。我们已经对人类ATG2A进行了研究，并展示了 这种蛋白质是一种杆状的膜系绳，可以在膜之间转移脂质。 我们目前的工作模型是，ATG2通过以下方式将脂质从内质网输送到吞噬载体 把他们绑起来。然后，运输的脂类将作为吞噬载体的基础。 围绕着底物建造。这项新提案旨在建立在这一模式的基础上，并进一步 对这一神秘过程的机械性洞察。在目标1中，我们将把对ATG2的研究扩展到 确定它的结构。目的是解释ATG2是如何在膜之间运输脂质的。 在目标2中，我们将重点研究ATG9，已知的自噬的完整膜蛋白 作为ATG2的互动演员。通过结构和生物化学特征，我们的目标是阐明 了解这种蛋白质的功能，并对噬菌体的扩张有了新的见解。在《目标3》中，我们将 描述ATG2和ATG9之间的相互作用。目标是确定这两个人是如何 蛋白质在结构水平上相互作用，并探索 ATG2介导的脂类转移和吞噬细胞扩张的相互作用。来自这些的结果 研究将在分子水平上促进我们对自噬小体生物发生的理解 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.