Autophagy, an intracellular degradation mechanism, involves de novo generation of autophagosomes that sequester and deliver cytoplasmic components to the lysosome for degradation. The mechanism behind autophagosomal membrane expansion has been a longstanding enigma in this field. Recent structural and biochemical analyses have revealed that two mysterious autophagy-related (Atg) proteins, Atg2 and Atg9, are novel types of intermembrane and interleaflet lipid transporters, respectively. This review summarizes recent discoveries surrounding Atg2 and Atg9 as a lipid transporter and discusses the molecular mechanism of autophagosomal membrane expansion driven by collaboration between these two lipid transporters.

自噬是一种细胞内降解机制，涉及自噬体的从头生成，自噬体将细胞质成分隔离并递送至溶酶体进行降解。自噬体膜扩张背后的机制一直是该领域的一个长期未解之谜。最近的结构和生化分析表明，两种神秘的自噬相关 (Atg) 蛋白 Atg2 和 Atg9 分别是新型的膜间和叶间脂质转运蛋白。本综述总结了 Atg2 和 Atg9 作为脂质转运蛋白的最新发现，并讨论了这两种脂质转运蛋白之间的协作驱动的自噬体膜扩张的分子机制。