Biomedical Sciences Graduate Program, University of California San Francisco, San Francisco, CA 94143, USA.
Department of Laboratory Medicine, University of California San Francisco, San Francisco, CA 94143, USA.
Biol Open. 2021 Oct 15;10(10). doi: 10.1242/bio.058736. Epub 2021 Oct 12.
There is great interest in understanding the cellular mechanisms controlling autophagy, a tightly regulated catabolic and stress-response pathway. Prior work has uncovered links between autophagy and the Golgi reassembly stacking protein of 55 kDa (GRASP55), but their precise interrelationship remains unclear. Intriguingly, both autophagy and GRASP55 have been functionally and spatially linked to the endoplasmic reticulum (ER)---Golgi interface, broaching this compartment as a site where GRASP55 and autophagy may intersect. Here, we uncover that loss of GRASP55 enhances LC3 puncta formation, indicating that GRASP55 restricts autophagosome formation. Additionally, using proximity-dependent biotinylation, we identify a GRASP55 proximal interactome highly associated with the ER-Golgi interface. Both nutrient starvation and loss of GRASP55 are associated with coalescence of early secretory pathway markers. In light of these findings, we propose that GRASP55 regulates spatial organization of the ER-Golgi interface, which suppresses early autophagosome formation.
人们对于理解控制自噬的细胞机制非常感兴趣，自噬是一种受到严格调控的分解代谢和应激反应途径。先前的工作已经揭示了自噬与 Golgi 重组装堆叠蛋白 55kDa（GRASP55）之间的联系，但它们之间的确切相互关系仍不清楚。有趣的是，自噬和 GRASP55 的功能和空间都与内质网（ER）-高尔基体接口有关，这表明这个隔室是 GRASP55 和自噬可能交汇的地方。在这里，我们发现 GRASP55 的缺失增强了 LC3 斑点的形成，表明 GRASP55 限制了自噬体的形成。此外，我们利用邻近依赖性生物素化，鉴定了一个与 ER-Golgi 界面高度相关的 GRASP55 近端相互作用组。营养饥饿和 GRASP55 的缺失都与早期分泌途径标记物的融合有关。鉴于这些发现，我们提出 GRASP55 调节 ER-Golgi 界面的空间组织，从而抑制早期自噬体的形成。
