An Atg4B Mutant Hampers the Lipidation of LC3 Paralogues and Causes Defects in Autophagosome Closure
An Atg4B Mutant Hampers the Lipidation of LC3 Paralogues and Causes Defects in Autophagosome Closure
复制标题
DOI：
10.1091/mbc.e08-03-0312
复制
发表时间：
2008-11-01
影响因子：
3.3
通讯作者：
Yoshimori, Tamotsu
中科院分区：
文献类型：
--
作者：
Fujita, Naonobu;Hayashi-Nishino, Mitsuko;Yoshimori, Tamotsu
在自噬过程中，泛素样分子 LC3/Atg8 与磷脂酰乙醇胺 (PE) 结合并形成自噬体。在哺乳动物细胞中，多个Atg8同源物（称为LC3旁系同源物）的存在阻碍了LC3旁系同源物脂化的遗传分析。在这里，我们发现 Atg4B（一种处理前 LC3 旁系同源物的蛋白酶）失活突变体的过度表达会抑制 LC3 旁系同源物的自噬降解和脂化。抑制作用是由游离 LC3 旁系同源物与 Atg4B 突变体形成稳定复合物的隔离引起的。在突变体过表达细胞中，Atg5 和 ULK1 阳性中间自噬结构积累。这些膜结构的长度与对照细胞中的长度相当；然而，仍有相当多的工厂没有关闭。这些结果表明LC3旁系同源物的脂化参与哺乳动物细胞中自噬体形成的完成。这项研究也为未来各种自噬研究提供了强大的工具。
In the process of autophagy, a ubiquitin-like molecule, LC3/Atg8, is conjugated to phosphatidylethanolamine ( PE) and associates with forming autophagosomes. In mammalian cells, the existence of multiple Atg8 homologues ( referred to as LC3 paralogues) has hampered genetic analysis of the lipidation of LC3 paralogues. Here, we show that overexpression of an inactive mutant of Atg4B, a protease that processes pro-LC3 paralogues, inhibits autophagic degradation and lipidation of LC3 paralogues. Inhibition was caused by sequestration of free LC3 paralogues in stable complexes with the Atg4B mutant. In mutant overexpressing cells, Atg5- and ULK1-positive intermediate autophagic structures accumulated. The length of these membrane structures was comparable to that in control cells; however, a significant number were not closed. These results show that the lipidation of LC3 paralogues is involved in the completion of autophagosome formation in mammalian cells. This study also provides a powerful tool for a wide variety of studies of autophagy in the future.