National Institute of Biological Sciences, Beijing, China.
PLoS Genet. 2013;9(8):e1003715. doi: 10.1371/journal.pgen.1003715. Epub 2013 Aug 8.
Macroautophagy (autophagy) is crucial for cell survival during starvation and plays important roles in animal development and human diseases. Molecular understanding of autophagy has mainly come from the budding yeast Saccharomyces cerevisiae, and it remains unclear to what extent the mechanisms are the same in other organisms. Here, through screening the mating phenotype of a genome-wide deletion collection of the fission yeast Schizosaccharomyces pombe, we obtained a comprehensive catalog of autophagy genes in this highly tractable organism, including genes encoding three heretofore unidentified core Atg proteins, Atg10, Atg14, and Atg16, and two novel factors, Ctl1 and Fsc1. We systematically examined the subcellular localization of fission yeast autophagy factors for the first time and characterized the phenotypes of their mutants, thereby uncovering both similarities and differences between the two yeasts. Unlike budding yeast, all three Atg18/WIPI proteins in fission yeast are essential for autophagy, and we found that they play different roles, with Atg18a uniquely required for the targeting of the Atg12-Atg5·Atg16 complex. Our investigation of the two novel factors revealed unforeseen autophagy mechanisms. The choline transporter-like protein Ctl1 interacts with Atg9 and is required for autophagosome formation. The fasciclin domain protein Fsc1 localizes to the vacuole membrane and is required for autophagosome-vacuole fusion but not other vacuolar fusion events. Our study sheds new light on the evolutionary diversity of the autophagy machinery and establishes the fission yeast as a useful model for dissecting the mechanisms of autophagy.
自噬（autophagy）在饥饿时对细胞存活至关重要，并在动物发育和人类疾病中发挥重要作用。自噬的分子理解主要来自出芽酵母酿酒酵母，而其他生物体的机制在多大程度上相同尚不清楚。在这里，我们通过筛选裂殖酵母 Schizosaccharomyces pombe 的全基因组缺失文库的交配表型，获得了这个高度可操作的生物体中自噬基因的综合目录，包括编码三个以前未鉴定的核心 Atg 蛋白（Atg10、Atg14 和 Atg16）和两个新因子（Ctl1 和 Fsc1）的基因。我们首次系统地检查了裂殖酵母自噬因子的亚细胞定位，并对其突变体的表型进行了特征描述，从而揭示了两种酵母之间的相似性和差异性。与出芽酵母不同，裂殖酵母中所有三种 Atg18/WIPI 蛋白对于自噬都是必需的，我们发现它们发挥不同的作用，Atg18a 独特地需要将 Atg12-Atg5·Atg16 复合物靶向。我们对这两个新因子的研究揭示了意想不到的自噬机制。胆碱转运蛋白样蛋白 Ctl1 与 Atg9 相互作用，是自噬体形成所必需的。纤连蛋白结构域蛋白 Fsc1 定位于液泡膜，对于自噬体-液泡融合是必需的，但对于其他液泡融合事件不是必需的。我们的研究揭示了自噬机制的进化多样性，并确立了裂殖酵母作为解析自噬机制的有用模型。
