Kawamata Tomoko, Kamada Yoshiaki, Kabeya Yukiko, Sekito Takayuki, Ohsumi Yoshinori
Department of Cell Biology, National Institute for Basic Biology, and School of Life Science, The Graduate University for Advanced Studies, Okazaki 444-8585, Japan.
Mol Biol Cell. 2008 May;19(5):2039-50. doi: 10.1091/mbc.e07-10-1048. Epub 2008 Feb 20.
Autophagy induced by nutrient depletion is involved in survival during starvation conditions. In addition to starvation-induced autophagy, the yeast Saccharomyces cerevisiae also has a constitutive autophagy-like system, the Cvt pathway. Among 31 autophagy-related (Atg) proteins, the function of Atg17, Atg29, and Atg31 is required specifically for autophagy. In this study, we investigated the role of autophagy-specific (i.e., non-Cvt) proteins under autophagy-inducing conditions. For this purpose, we used atg11Delta cells in which the Cvt pathway is abrogated. The autophagy-unique proteins are required for the localization of Atg proteins to the pre-autophagosomal structure (PAS), the putative site for autophagosome formation, under starvation condition. It is likely that these Atg proteins function as a ternary complex, because Atg29 and Atg31 bind to Atg17. The Atg1 kinase complex (Atg1-Atg13) is also essential for recruitment of Atg proteins to the PAS. The assembly of Atg proteins to the PAS is observed only under autophagy-inducing conditions, indicating that this structure is specifically involved in autophagosome formation. Our results suggest that Atg1 complex and the autophagy-unique Atg proteins cooperatively organize the PAS in response to starvation signals.
营养物质匮乏诱导的自噬参与饥饿条件下的细胞存活。除了饥饿诱导的自噬外，酿酒酵母还具有一种组成型自噬样系统，即Cvt途径。在31种自噬相关（Atg）蛋白中，Atg17、Atg29和Atg31的功能是自噬所特有的。在本研究中，我们研究了自噬诱导条件下自噬特异性（即非Cvt）蛋白的作用。为此，我们使用了缺失Cvt途径的atg11Delta细胞。在饥饿条件下，自噬独特蛋白对于Atg蛋白定位于自噬前体结构（PAS）（自噬体形成的假定位点）是必需的。这些Atg蛋白可能作为三元复合物发挥作用，因为Atg29和Atg31与Atg17结合。Atg1激酶复合物（Atg1-Atg13）对于将Atg蛋白募集到PAS也至关重要。仅在自噬诱导条件下观察到Atg蛋白组装到PAS，这表明该结构特别参与自噬体形成。我们的结果表明，Atg1复合物和自噬独特的Atg蛋白响应饥饿信号协同组织PAS。
