Autophagosomes are double-membrane vesicles that sequester cytoplasmic material for lysosomal degradation. Their biogenesis is initiated by recruitment of Atg9-vesicles to the phagophore assembly site. This process depends on the regulated activation of the Atg1-kinase complex. However, the underlying molecular mechanism remains unclear. Here we reconstitute this early step in autophagy from purified components in vitro. We find that on assembly from its cytoplasmic subcomplexes, the Atg1-kinase complex becomes activated, enabling it to recruit and tether Atg9-vesicles. The scaffolding protein Atg17 targets the Atg1-kinase complex to autophagic membranes by specifically recognizing the membrane protein Atg9. This interaction is inhibited by the two regulatory subunits Atg31 and Atg29. Engagement of the Atg1-Atg13 subcomplex restores the Atg9-binding and membrane-tethering activity of Atg17. Our data help to unravel the mechanism that controls Atg17-mediated tethering of Atg9-vesicles, providing the molecular basis to understand initiation of autophagosome-biogenesis.

中文翻译：

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Atg1激酶复杂的系链Atg9小泡启动自噬。

自噬体是双膜囊泡，可将胞质物质隔离起来以进行溶酶体降解。它们的生物发生是通过将Atg9囊泡募集到吞噬细胞装配位点而启动的。此过程取决于Atg1激酶复合物的调节激活。但是，潜在的分子机制仍不清楚。在这里，我们从体外纯化的成分中重建了自噬的这一早期步骤。我们发现从其细胞质亚复合体组装时，Atg1激酶复合体被激活，使其能够募集并束缚Atg9囊泡。支架蛋白Atg17通过特异性识别膜蛋白Atg9，将Atg1-激酶复合物靶向自噬膜。该相互作用被两个调节亚基Atg31和Atg29抑制。Atg1-Atg13亚复合物的参与恢复了Atg17的Atg9结合和膜束缚活性。我们的数据有助于揭示控制Atg17介导的Atg9囊泡束缚的机制，为理解自噬生物体的启动提供分子基础。