Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA.
Cell. 2011 Jul 22;146(2):290-302. doi: 10.1016/j.cell.2011.06.022.
Macroautophagy mediates the degradation of long-lived proteins and organelles via the de novo formation of double-membrane autophagosomes that sequester cytoplasm and deliver it to the vacuole/lysosome; however, relatively little is known about autophagosome biogenesis. Atg8, a phosphatidylethanolamine-conjugated protein, was previously proposed to function in autophagosome membrane expansion, based on the observation that it mediates liposome tethering and hemifusion in vitro. We show here that with physiological concentrations of phosphatidylethanolamine, Atg8 does not act as a fusogen. Rather, we provide evidence for the involvement of exocytic Q/t-SNAREs in autophagosome formation, acting in the recruitment of key autophagy components to the site of autophagosome formation, and in regulating the organization of Atg9 into tubulovesicular clusters. Additionally, we found that the endosomal Q/t-SNARE Tlg2 and the R/v-SNAREs Sec22 and Ykt6 interact with Sso1-Sec9, and are required for normal Atg9 transport. Thus, multiple SNARE-mediated fusion events are likely to be involved in autophagosome biogenesis.
自噬体通过从头形成双层膜自噬体来介导长寿命蛋白质和细胞器的降解，该自噬体隔离细胞质并将其递送至液泡/溶酶体；然而，自噬体生物发生的机制相对知之甚少。以前，基于观察到它介导体外脂质体连接和半融合的现象，认为磷酸乙醇胺结合蛋白 Atg8 在自噬体膜扩展中发挥作用。我们在这里表明，在生理浓度的磷酸乙醇胺下，Atg8 不作为融合剂。相反，我们提供了证据表明外排 Q/t-SNAREs 参与自噬体的形成，作用是将关键的自噬成分募集到自噬体形成的部位，并调节 Atg9 形成管状泡状簇。此外，我们发现内体 Q/t-SNARE Tlg2 和 R/v-SNAREs Sec22 和 Ykt6 与 Sso1-Sec9 相互作用，并且是正常 Atg9 运输所必需的。因此，多个 SNARE 介导的融合事件可能参与自噬体的生物发生。
