Department of Urology, State Key Laboratory of Biotherapy, West China Hospital, College of Life Sciences, Sichuan University, Chengdu, China.
State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, Chinese Academy of Medical Sciences Research Unit of Oral Carcinogenesis and Management, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
Cell Mol Life Sci. 2021 Mar;78(5):2131-2143. doi: 10.1007/s00018-020-03621-9. Epub 2020 Aug 18.
Macroautophagy (hereafter referred to as autophagy) is a highly conserved catabolic eukaryotic pathway that is critical for stress responses and homeostasis. Atg18, one of the core proteins involved in autophagy, belongs to the PROPPIN family and is composed of seven WD40 repeats. Together with Atg2, Atg18 participates in the elongation of phagophores and the recycling of Atg9 in yeast. Despite extensive studies on the PROPPIN family, the structure of Atg18 from Saccharomyces cerevisiae has not been determined. Here, we report the structure of ScAtg18 at a resolution of 2.8 Å. Based on bioinformatics and structural analysis, we found that the 7AB loop of ScAtg18 is extended in Atg18, in comparison to other members of the PROPPIN family. Genetic analysis revealed that the 7AB loop of ScAtg18 is required for autophagy. Biochemical and biophysical experiments indicated that the 7AB loop of ScAtg18 is critical for interaction with ScAtg2 and the recruitment of ScAtg2 to the autophagy-initiating site. Collectively, our results show that the 7AB loop of ScAtg18 is a new binding site for Atg2 and is of functional importance to autophagy.
自噬（以下简称自噬）是一种高度保守的溶酶体途径，对于应激反应和内稳态至关重要。参与自噬的核心蛋白之一 Atg18 属于 PROPPIN 家族，由七个 WD40 重复组成。Atg18 与 Atg2 一起参与噬泡的伸长和酵母中 Atg9 的循环利用。尽管对 PROPPIN 家族进行了广泛的研究，但酿酒酵母的 Atg18 结构尚未确定。在这里，我们报告了分辨率为 2.8Å 的 ScAtg18 结构。基于生物信息学和结构分析，我们发现与 PROPPIN 家族的其他成员相比，ScAtg18 的 7AB 环在 Atg18 中得到了延伸。遗传分析表明，ScAtg18 的 7AB 环对于自噬是必需的。生化和生物物理实验表明，ScAtg18 的 7AB 环对于与 ScAtg2 的相互作用以及 ScAtg2 向自噬起始部位的募集至关重要。总之，我们的结果表明，ScAtg18 的 7AB 环是 Atg2 的新结合位点，对自噬具有重要的功能意义。
