Delipidation of mammalian Atg8-family proteins by each of the four ATG4 proteases
Delipidation of mammalian Atg8-family proteins by each of the four ATG4 proteases
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DOI：
10.1080/15548627.2018.1437341
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发表时间：
2018-01-01
期刊：
影响因子：
13.3
通讯作者：
Melia, Thomas J.
中科院分区：
文献类型：
--
作者：
Kauffman, Karlina J.;Yu, Shenliang;Melia, Thomas J.
在巨噬/自噬过程中，哺乳动物atg8家族蛋白经历2个蛋白水解加工事件。第一种方法将用于这些蛋白质结合的羧基末端甘氨酸暴露于吞噬细胞（自噬体的前体）上的脂质上，而第二种方法则释放脂质。ATG4蛋白酶家族驱动这两种裂解，但ATG4蛋白如何区分可溶性和脂质锚定的at8蛋白尚不清楚。在一个完全重构的脱水实验中，我们发现哺乳动物atg8家族蛋白在膜上的物理锚定极大地改变了ATG4蛋白酶识别这些底物的方式。因此，虽然ATG4B处理可溶性无引物蛋白的速度要快几个数量级，但所有4种ATG4蛋白酶都可以在脂质附着的底物上被激活，产生类似的酶活性。在体外和细胞中，脂化但不溶性底物的识别对cooh末端LIR基序都很敏感。我们提出了一种模型，其中ATG4B驱动哺乳动物at8蛋白的快速启动，而脱脂本身是缓慢的，并由所有ATG4同源物调节。
During macroautophagy/autophagy, mammalian Atg8-family proteins undergo 2 proteolytic processing events. The first exposes a COOH-terminal glycine used in the conjugation of these proteins to lipids on the phagophore, the precursor to the autophagosome, whereas the second releases the lipid. The ATG4 family of proteases drives both cleavages, but how ATG4 proteins distinguish between soluble and lipid-anchored Atg8 proteins is not well understood. In a fully reconstituted delipidation assay, we establish that the physical anchoring of mammalian Atg8-family proteins in the membrane dramatically shifts the way ATG4 proteases recognize these substrates. Thus, while ATG4B is orders of magnitude faster at processing a soluble unprimed protein, all 4 ATG4 proteases can be activated to similar enzymatic activities on lipid-attached substrates. The recognition of lipidated but not soluble substrates is sensitive to a COOH-terminal LIR motif both in vitro and in cells. We suggest a model whereby ATG4B drives very fast priming of mammalian Atg8 proteins, whereas delipidation is inherently slow and regulated by all ATG4 homologs.