Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, Gif-sur-Yvette, France.
INSERM U1280, Gif-sur-Yvette, France.
Elife. 2023 Jul 3;12:e85748. doi: 10.7554/eLife.85748.
The ubiquitin-like proteins Atg8/LC3/GABARAP are required for multiple steps of autophagy, such as initiation, cargo recognition and engulfment, vesicle closure and degradation. Most of LC3/GABARAP functions are considered dependent on their post-translational modifications and their association with the autophagosome membrane through a conjugation to a lipid, the phosphatidyl-ethanolamine. Contrarily to mammals, possesses single homologs of LC3 and GABARAP families, named LGG-2 and LGG-1. Using site-directed mutagenesis, we inhibited the conjugation of LGG-1 to the autophagosome membrane and generated mutants that express only cytosolic forms, either the precursor or the cleaved protein. LGG-1 is an essential gene for autophagy and development in , but we discovered that its functions could be fully achieved independently of its localization to the membrane. This study reveals an essential role for the cleaved form of LGG-1 in autophagy but also in an autophagy-independent embryonic function. Our data question the use of lipidated GABARAP/LC3 as the main marker of autophagic flux and highlight the high plasticity of autophagy.
泛素样蛋白 Atg8/LC3/GABARAP 对于自噬的多个步骤是必需的，如起始、货物识别和吞噬、囊泡闭合和降解。LC3/GABARAP 的大多数功能被认为依赖于它们的翻译后修饰以及通过与脂质（磷脂酰乙醇胺）缀合与自噬体膜的关联。与哺乳动物不同，秀丽隐杆线虫拥有 LC3 和 GABARAP 家族的单个同源物，分别命名为 LGG-2 和 LGG-1。通过定点诱变，我们抑制了 LGG-1 与自噬体膜的缀合，并生成了仅表达细胞质形式的突变体，无论是前体还是切割蛋白。LGG-1 是线虫中自噬和发育所必需的基因，但我们发现其功能可以完全独立于其定位于膜上实现。这项研究揭示了 LGG-1 的切割形式在自噬中的重要作用，但也揭示了其在自噬独立的胚胎功能中的作用。我们的数据对使用脂质化 GABARAP/LC3 作为自噬通量的主要标志物提出了质疑，并强调了自噬的高度可塑性。
