Transport of phosphatidylinositol 3-phosphate into the vacuole via autophagic membranes in S . cerevisiae
Transport of phosphatidylinositol 3-phosphate into the vacuole via autophagic membranes in S . cerevisiae
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发表时间：
2018
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通讯作者：
K. Obara;T. Noda;K. Niimi;Y. Ohsumi
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作者：
K. Obara;T. Noda;K. Niimi;Y. Ohsumi
Vps34是酵母中唯一的PtdIns 3-激酶，对自噬是必不可少的。在这里，我们证明了Vps34的脂激酶活性是自噬所必需的，这意味着其产物PtdIns(3)P的一个重要作用。PtdIns 3-激酶复合体的一个调节亚单位Vps15的蛋白激酶活性也是有效自噬所必需的。我们使用一种特定的指示剂，即来自哺乳动物HRS的2xFYVE结构域，监测了PtdIns(3)P在活细胞中的分布。在对数生长期，PtdIns(3)P在内体和液泡膜上含量丰富。在饥饿条件下，我们观察到大量的PtdIns(3)P进入液泡。这种积累依赖于自噬的膜动力学。值得注意的是，PtdIns(3)P高度浓缩，并作为自噬体膜的一个组成部分输送到液泡中，而不是作为包裹在自噬体膜内的货物，这意味着这种肌醇磷脂直接参与了自噬体膜的形成。我们还发现，与外膜相比，PtdIns(3)P可能在自噬体内膜上富集。在此基础上，我们讨论了PtdIns(3)P在自噬中的作用。
Vps34, the sole PtdIns 3-kinase in yeast, is essential for autophagy. Here, we show that the lipid-kinase activity of Vps34 is required for autophagy, implying an essential role of its product PtdIns(3)P. The protein kinase activity of Vps15, a regulatory subunit of the PtdIns 3-kinase complex, is also required for efficient autophagy. We monitored the distribution of PtdIns(3)P in living cells using a specific indicator, the 2xFYVE domain derived from mammalian Hrs. PtdIns(3)P was abundant at endosomes and on the vacuolar membrane during logarithmic growth phase. Under starvation conditions, we observed massive transport of PtdIns(3)P into the vacuole. This accumulation was dependent on the membrane dynamics of autophagy. Notably, PtdIns(3)P was highly enriched and delivered into the vacuole as a component of autophagosome membranes but not as a cargo enclosed within them, implying direct involvement of this phosphoinositide in autophagosome formation. We also found a possible enrichment of PtdIns(3)P on the inner autophagosomal membrane compared to the outer membrane. Based on these results we discuss the function of PtdIns(3)P in autophagy.