Macroautophagy is a conserved degradation pathway, which mediates cellular homeostasis by the delivery of harmful substances into lysosomes. This is achieved by the sequestration of these substances referred to as cargo within double membrane vesicles, the autophagosomes, which form de novo. Among the many cargoes that are targeted by autophagy are condensates containing p62 and ubiquitinated proteins. p62 recruits the FIP200 protein to initiate autophagosome formation at the condensates. How FIP200 in turn organizes the autophagy machinery is unclear. Here we show that FIP200 is dispensable for the recruitment of the upstream autophagy machinery to the condensates, but it is necessary for phosphatidylinositol 3-phosphate formation and WIPI2 recruitment. We further find that FIP200 is required for the activation of the ULK1 kinase. Surprisingly, ULK1 kinase activity is not strictly required for autophagosome formation at p62 condensates. Super-resolution microscopy of p62 condensates revealed that FIP200 surrounds the condensates where it spatially organizes ATG13 and ATG9A for productive autophagosome formation. Our data provide a mechanistic insight into how FIP200 orchestrates autophagosome initiation at the cargo.

中文翻译：

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FIP200在激活ULK1激酶后在p62泛素凝结处组织自噬机制

巨自噬是一种保守的降解途径，其通过将有害物质输送到溶酶体中来介导细胞稳态。这是通过将称为“货物”的这些物质隔离在从头形成的双层膜囊泡（自噬体）中来实现的。自噬靶向的许多货物中有含有p62和泛素化蛋白的冷凝物。p62募集FIP200蛋白以启动在冷凝物中的自噬体形成。FIP200又如何组织自噬机制尚不清楚。在这里，我们显示FIP200对于将上游自噬机械募集至冷凝液是必不可少的，但对于磷脂酰肌醇3-磷酸的形成和WIPI2募集是必需的。我们进一步发现FIP200是激活ULK1激酶所必需的。出奇，对于p62冷凝物上的自噬体形成，ULK1激酶活性不是严格要求的。p62冷凝物的超分辨率显微镜显示，FIP200围绕冷凝物，在空间上它在空间上组织了ATG13和ATG9A，以形成高效的自噬体。我们的数据提供了有关FIP200如何协调货物中自噬起始的机制的见解。