PDF(Pubmed)
Abstract：
Autophagy was initially recognized as a bulk degradation process that randomly sequesters and degrades cytoplasmic material in lysosomes (vacuoles in yeast). In recent years, various types of selective autophagy have been discovered. Glycophagy, the selective autophagy of glycogen granules, is one of them. While autophagy of glycogen is an important contributor to Pompe disease, which is characterized by the lysosomal accumulation of glycogen, its selectivity is still a matter of debate. Here, we developed the Komagataella phaffii yeast as a simple model of glycogen autophagy under nitrogen starvation conditions to address the question of its selectivity. For this, we turned the self-glucosylating initiator of glycogen synthesis, Glg1, which is covalently bound to glycogen, into the Glg1-GFP autophagic reporter. Our results revealed that vacuolar delivery of Glg1-GFP and its processing to free GFP were strictly dependent on autophagic machinery and vacuolar proteolysis. Notably, this process was independent of Atg11, the scaffold protein common for many selective autophagy pathways. Importantly, the non-mutated Glg1-GFP (which synthesizes and marks glycogen) and mutated Glg1Y212F-GFP (which does not synthesize glycogen and is degraded by non-selective autophagy as cytosolic Pgk1-GFP) were equally well delivered to the vacuole and had similar levels of released GFP. Therefore, we concluded that glycogen autophagy is a non-selective process in K. phaffii yeast under nitrogen starvation conditions.
摘要：
自噬最初被认为是一种批量降解过程，它随机隔离和降解溶酶体（酵母中的液泡）中的细胞质物质。近年来,已经发现了各种类型的选择性自噬。糖食，糖原颗粒的选择性自噬，是其中之一。虽然糖原的自噬是导致庞贝氏症的重要因素，其特征是糖原的溶酶体积累，它的选择性仍然是一个争论的问题。这里,我们开发了Komagataellaphafii酵母作为氮饥饿条件下糖原自噬的简单模型，以解决其选择性问题。为此，我们把糖原合成的自糖基化引发剂,与糖原共价结合的Glg1，进入Glg1-GFP自噬报告分子。我们的结果表明，Glg1-GFP的液泡递送及其对游离GFP的加工严格依赖于自噬机制和液泡蛋白水解。值得注意的是,该过程与许多选择性自噬途径常见的支架蛋白Atg11无关。重要的是,未突变的Glg1-GFP(其合成并标记糖原)和突变的Glg1Y212F-GFP(其不合成糖原并且被非选择性自噬降解为胞质Pgk1-GFP)同样良好地递送至液泡,并且具有相似水平的GFP释放.因此,我们得出结论，在氮饥饿条件下，糖原自噬是K.phafii酵母中的非选择性过程。
