Autophagosome formation is initiated at phosphatidylinositol synthase-enriched ER subdomains
Autophagosome formation is initiated at phosphatidylinositol synthase-enriched ER subdomains
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DOI：
10.15252/embj.201695189
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发表时间：
2017-06-14
期刊：
影响因子：
11.4
通讯作者：
Mizushima, Noboru
中科院分区：
文献类型：
--
作者：
Nishimura, Taki;Tamura, Norito;Mizushima, Noboru
自噬小体是一种双膜结构，通过大范围的自噬作用调节细胞质的降解，形成于内质网(ER)附近。然而，内质网膜如何参与自噬启动，以及自噬启动复合体定位于哪些膜结构还没有完全确定。在这里，我们能够对自噬中间膜进行生化分析，并表明含有ULK和FIP200的自噬起始复合体首先与内质网膜结合。为了进一步研究ER亚区，我们对磷脂生物合成酶进行了筛选，发现自噬起始复合体定位于磷脂酰肌醇合成酶(PiS)丰富的ER亚区。然后，起始复合体以依赖于PI3P的方式移位到ATG9A阳性的自噬小体前体。通过将磷脂酰肌醇(PI)特异性磷脂酶C靶向PIS结构域来耗尽磷脂酰肌醇(PI)会损害下游自噬因子的募集和自噬小体的形成。这些发现表明，自噬起始复合体、富含PIS的ER亚域和ATG9A小泡共同启动自噬小体的形成。
The autophagosome, a double-membrane structure mediating degradation of cytoplasmic materials by macroautophagy, is formed in close proximity to the endoplasmic reticulum (ER). However, how the ER membrane is involved in autophagy initiation and to which membrane structures the autophagy-initiation complex is localized have not been fully characterized. Here, we were able to biochemically analyze autophagic intermediate membranes and show that the autophagy-initiation complex containing ULK and FIP200 first associates with the ER membrane. To further characterize the ER subdomain, we screened phospholipid biosynthetic enzymes and found that the autophagy-initiation complex localizes to phosphatidylinositol synthase (PIS)-enriched ER subdomains. Then, the initiation complex translocates to the ATG9A-positive autophagosome precursors in a PI3P-dependent manner. Depletion of phosphatidylinositol (PI) by targeting bacterial PI-specific phospholipase C to the PIS domain impairs recruitment of downstream autophagy factors and autophagosome formation. These findings suggest that the autophagy-initiation complex, the PIS-enriched ER subdomain, and ATG9A vesicles together initiate autophagosome formation.