Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Faculty of Biology, University of Freiburg, Freiburg, Germany.
EMBO Rep. 2020 Dec 3;21(12):e51869. doi: 10.15252/embr.202051869.
Autophagy mediates the degradation of cytoplasmic material. Upon autophagy induction, autophagosomes form a sealed membrane around the cargo and fuse with the lytic compartment to release the cargo for degradation. In order to avoid premature fusion of immature autophagosomal membranes with the lytic compartment, this process needs to be tightly regulated. Several factors mediating autophagosome-vacuole fusion have recently been identified. In budding yeast, autophagosome-vacuole fusion requires the R-SNARE Ykt6 on the autophagosome, together with the three Q-SNAREs Vam3, Vam7, and Vti1 on the vacuole. However, how these SNAREs are regulated during the fusion process is poorly understood. In this study, we investigate the regulation of Ykt6. We found that Ykt6 is directly phosphorylated by Atg1 kinase, which keeps this SNARE in an inactive state. Ykt6 phosphorylation prevents SNARE bundling by disrupting its interaction with the vacuolar SNAREs Vam3 and Vti1, thereby preventing premature autophagosome-vacuole fusion. These findings shed new light on the regulation of autophagosome-vacuole fusion and reveal a further step in autophagy controlled by the Atg1 kinase.
自噬介导细胞质物质的降解。在自噬诱导后，自噬体围绕货物形成密封膜，并与溶酶体融合，将货物释放进行降解。为了避免未成熟的自噬体膜与溶酶体过早融合，这个过程需要严格调控。最近已经鉴定出了几种介导自噬体-液泡融合的因素。在芽殖酵母中，自噬体-液泡融合需要自噬体上的 R-SNARE Ykt6，以及液泡上的三个 Q-SNAREs Vam3、Vam7 和 Vti1。然而，在融合过程中这些 SNAREs 是如何被调控的还知之甚少。在这项研究中，我们研究了 Ykt6 的调控。我们发现 Ykt6 被 Atg1 激酶直接磷酸化，使其处于非活性状态。Ykt6 的磷酸化通过破坏其与液泡 SNAREs Vam3 和 Vti1 的相互作用，阻止 SNARE 束的形成，从而防止过早的自噬体-液泡融合。这些发现为自噬体-液泡融合的调控提供了新的视角，并揭示了 Atg1 激酶控制的自噬的进一步步骤。
