Autophagic and non-autophagic functions of the S. cerevisiae PROPPINs Atg18, Atg21 and Hsv2

酿酒酵母 PROPPIN Atg18、Atg21 和 Hsv2 的自噬和非自噬功能

• 批准号: 519482673
• 负责人: Professor Dr. Michael Thumm
• 金额: --
• 依托单位: Institut für Zellbiochemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/519482673?language=en
• 关键词: Autophagic; non; autophagic; functions; S.

Atg18, Atg21 and Hsv2 are yeast members of a highly conserved family of PROPPINs (-propeller that bind polyphosphoinositides). They bind via two binding sites at their circumference to PI3P and PI(3,5)P2. Atg18 and Atg21 were initially identified for their requirement for macroautophagy (hereafter autophagy). The function of the homologous Hsv2 remained elusive. We only found a partial effect on micronucleophagy, where the contact site between the vacuole and the nuclear envelope is degraded during nitrogen starvation together with non-essential parts of the nucleus. PROPPINs have beside their PI3P-dependent roles in autophagy additional non-autophagic functions. Atg18 negatively regulates the vacuolar PI3P 5-kinase Fab1. It further functions in retrograde transport of the artificial cargo RS-ALP from the vacuole to the Golgi. Atg18 and to a lesser extend Atg21 are further involved in vacuolar fragmentation upon hyperosmotic shock. To better understand the molecular functions of the PROPPINs, we used the proximity labeling BioID approach for all three PROPPINs, which allows in living cells the identification of proteins within the microenvironment of the bait proteins. In an already published study we found that Atg18 is part of a novel retromer complex, which mediates vacuole fragmentation upon hyperosmotic stress. We further showed that the cycling of the integral membrane protein Atg9, which is essential for autophagosome biogenesis depends on Atg18-retromer. Using two types of Atg18 mutants, which are expected to be selectively impaired in its role in protein recycling but not autophagy, we now want to understand the precise molecular function of Atg18-retromer. Further major aims are to clarify the function of Hsv2 and to dissect the organization of Atg21-complexes at the phagophore. To this end, we will carry out in depth analyses of a set of novel PROPPIN interactors found in our unpublished proximity labeling screens.

Atg 18、Atg 21和Hsv 2是高度保守的PROPPIN（结合多磷酸肌醇的β-螺旋桨）家族的酵母成员。它们通过其周围的两个结合位点与PI 3 P和PI（3，5）P2结合。Atg 18和Atg 21最初被鉴定为它们对大自噬（下文称为自噬）的需要。同源的Hsv 2的功能仍然难以捉摸。我们只发现了对嗜微核的部分影响，其中空泡和核膜之间的接触部位在氮饥饿期间与核的非必需部分一起降解。PROPPIN除了在自噬中的PI 3 P依赖性作用外，还具有额外的非自噬功能。Atg 18负调节液泡PI 3 P 5-激酶Fab 1。它还在人工货物RS-ALP从液泡到高尔基体的逆行运输中发挥作用。Atg 18和在较小程度上Atg 21进一步参与高渗休克后的液泡破碎。为了更好地了解PROPPIN的分子功能，我们对所有三种PROPPIN使用了邻近标记BioID方法，该方法允许在活细胞中鉴定诱饵蛋白微环境中的蛋白质。在一项已经发表的研究中，我们发现Atg 18是一种新型retromer复合物的一部分，它在高渗胁迫下介导液泡破碎。我们进一步表明，自噬体生物合成所必需的膜蛋白Atg 9的循环依赖于Atg 18-retromer。使用两种类型的Atg 18突变体，这是预计将选择性地削弱其在蛋白质回收的作用，但不是自噬，我们现在想了解确切的分子功能Atg 18逆转录。进一步的主要目的是澄清Hsv 2的功能，并剖析Atg 21复合物在吞噬细胞的组织。为此，我们将进行深入分析的一组新的PROPPIN相互作用发现在我们的未发表的接近标记屏幕。