Mechanisms of Selective Autophagy

 描述（由申请人提供）：选择性自噬机制大自噬（称为自噬）是细胞通过高度调节的途径隔离胞质组分/细胞器的过程，该途径以溶酶体介导的货物降解和大分子再循环回到胞质溶胶中终止。虽然最初被认为是一种非特异性的大量降解过程，但最近的工作揭示了几种形式的选择性自噬在多种生物过程中发挥关键作用。各种类型的选择性自噬在多个水平上被调节，使用特异性自噬受体的库，其识别不同的货物以及与自噬体相关并结合货物受体的不同的ATG 8蛋白家族。先前的研究表明，自噬通过降解铁蛋白（一种形成螯合游离铁的复合物的蛋白质）来控制细胞铁水平;然而，这种活性的机制仍不清楚。通过先进的定量蛋白质组学，我们的实验室发现NCOA 4作为铁蛋白降解的自噬受体（ferritinophagy）。此外，我们的初步数据表明，这一过程在几个水平上受到高度调控，包括响应铁的NCOA 4降解。这些发现为我们提供了前所未有的机会，机械解剖的生化基础，以及阐明铁蛋白是如何与其他形式的选择性自噬（即线粒体自噬），有助于铁稳态和氧化应激控制整合。该提议的总体假设是，各种形式的选择性自噬被高度调节以协调关键的细胞过程，例如生物可利用铁的调节。在此背景下，我们提出以下目标： AIM 1.调节铁蛋白吞噬的生化机制和整合到整体自噬途径中。这些研究将阐明在铁蛋白吞噬和其他形式的选择性自噬中货物识别和招募自噬体的选择性机制。 AIM 2.探讨线粒体吞噬和铁蛋白吞噬在细胞应激反应中的协同作用。这些研究将阐明铁蛋白自噬和线粒体自噬对关键细胞功能的贡献。 目标3.通过控制铁代谢阐明自噬在体内组织内稳定中的重要性。这些研究将使用以诱导方式有条件抑制自噬的小鼠模型以及有条件的NCOA 4敲除小鼠，以了解自噬的作用，特别是通过控制生物可利用铁的铁蛋白在红细胞生成中的作用。

 DESCRIPTION (provided by applicant): Mechanisms of Selective Autophagy Macroautophagy (referred to as autophagy) is a process whereby cells sequester cytosolic components/organelles via a highly regulated pathway that terminates with the lysosomal-mediated degradation of the cargo and the recycling of macromolecules back into the cytosol. While initially thought to be a non-specific process of bulk degradation, recent work has revealed several forms of selective autophagy that play key roles in multiple biological processes. The various types of selective autophagy are regulated on multiple levels, using a repertoire of specific autophagy receptors, which recognize distinct cargo as well as a diverse family of ATG8 proteins that associate with the autophagosome and bind cargo receptors. Prior work has implicated autophagy in the control of cellular iron levels through the degradation of ferritin (a protein that forms a complex which sequesters free iron); however, the mechanism underlying this activity remained unclear. Through advanced quantitative proteomics, our laboratories discovered NCOA4 as the autophagy receptor for ferritin degradation (ferritinophagy). Moreover, our preliminary data suggests that this process is highly regulated at several levels, including the degradation of NCOA4 in response to iron. These findings provide us with the unprecedented opportunity to mechanistically dissect the biochemical basis for ferritinophagy, as well as to elucidate how ferritinophagy is integrated with other forms of selective autophagy (i.e. mitophagy) that contribute to iron homeostasis and oxidative stress control. The overarching hypothesis of this proposal is that the various forms of selective autophagy are highly regulated to coordinate critical cellular processes such as the regulation of bioavailable iron. Against this backdrop, we propose the following Aims: AIM 1. BIOCHEMICAL MECHANISMS REGULATING FERRITINOPHAGY AND INTEGRATION INTO GLOBAL AUTOPHAGY PATHWAYS. These studies will elucidate mechanisms underlying the selectivity of cargo recognition and recruitment to autophagosomes in ferritinophagy and other forms of selective autophagy. AIM 2. TO EXPLORE THE COOPERATIVE FUNCTIONS OF MITOPHAGY AND FERRITINOPHAGY IN RESPONSE TO CELLULAR STRESSORS. These studies will elucidate the contributions of ferritinophagy and mitophagy to critical cellular functions. Aim 3. TO ELUCIDATE THE IMPORTANCE OF AUTOPHAGY IN TISSUE HOMEOSTASIS IN VIVO THROUGH THE CONTROL OF IRON METABOLISM. These studies will use mouse models where autophagy is conditionally inhibited in an inducible fashion as well as a conditional NCOA4 knockout mouse to understand the role of autophagy and specifically ferritinophagy in erythrogenesis through its control of bioavailable iron.