Autophagosome biogenesis is an essential feature of autophagy. Lipidation of Atg8 plays a critical role in this process. Previous in vitro studies identified membrane tethering and hemi-fusion/fusion activities of Atg8, yet definitive roles in autophagosome biogenesis remained controversial. Here, we studied the effect of Atg8 lipidation on membrane structure. Lipidation of Saccharomyces cerevisiae Atg8 on nonspherical giant vesicles induced dramatic vesicle deformation into a sphere with an out-bud. Solution NMR spectroscopy of Atg8 lipidated on nanodiscs identified two aromatic membrane-facing residues that mediate membrane-area expansion and fragmentation of giant vesicles in vitro. These residues also contribute to the in vivo maintenance of fragmented vacuolar morphology under stress in fission yeast, a moonlighting function of Atg8. Furthermore, these aromatic residues are crucial for the formation of a sufficient number of autophagosomes and regulate autophagosome size. Together, these data demonstrate that Atg8 can cause membrane perturbations that underlie efficient autophagosome biogenesis.

自噬体生物发生是自噬的一个重要特征。Atg8 的脂质化在此过程中起着关键作用。先前的体外研究确定了 Atg8 的膜束缚和半融合/融合活性，但自噬体生物发生中的确定作用仍存在争议。在这里，我们研究了 Atg8 脂化对膜结构的影响。酿酒酵母的脂化非球形巨型囊泡上的 Atg8 诱导囊泡显着变形为具有外芽的球体。纳米圆盘上脂化的 Atg8 的溶液 NMR 光谱鉴定了两个芳香族膜面向残基，它们在体外介导膜面积扩张和巨型囊泡的碎裂。这些残基还有助于在裂殖酵母中在压力下维持碎片化的液泡形态，这是 Atg8 的兼职功能。此外，这些芳香族残基对于形成足够数量的自噬体和调节自噬体大小至关重要。总之，这些数据表明 Atg8 可以引起膜扰动，这是有效自噬体生物发生的基础。