Gopaldass Navin, Fauvet Bruno, Lashuel Hilal, Roux Aurélien, Mayer Andreas
Department of Biochemistry, University of Lausanne, Epalinges, Switzerland.
Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
EMBO J. 2017 Nov 15;36(22):3274-3291. doi: 10.15252/embj.201796859. Epub 2017 Oct 13.
Sorting, transport, and autophagic degradation of proteins in endosomes and lysosomes, as well as the division of these organelles, depend on scission of membrane-bound tubulo-vesicular carriers. How scission occurs is poorly understood, but family proteins bind these membranes. Here, we show that the yeast PROPPIN Atg18 carries membrane scission activity. Purified Atg18 drives tubulation and scission of giant unilamellar vesicles. Upon membrane contact, Atg18 folds its unstructured CD loop into an amphipathic α-helix that inserts into the bilayer. This allows the protein to engage its two lipid binding sites for PI3P and PI(3,5)P PI(3,5)P induces Atg18 oligomerization, which should concentrate lipid-inserted α-helices in the outer membrane leaflet and drive membrane tubulation and scission. The scission activity of Atg18 is compatible with its known roles in endo-lysosomal protein trafficking, autophagosome biogenesis, and vacuole fission. Key features required for membrane tubulation and scission by Atg18 are shared by other PROPPINs, suggesting that membrane scission may be a generic function of this protein family.
内体和溶酶体中蛋白质的分选、运输和自噬降解，以及这些细胞器的分裂，都依赖于膜结合的管状囊泡载体的切割。切割是如何发生的目前还知之甚少，但家族蛋白会结合这些膜。在这里，我们表明酵母PROPPIN蛋白Atg18具有膜切割活性。纯化的Atg18可驱动巨型单层囊泡的管状化和切割。在膜接触时，Atg18将其无结构的CD环折叠成一个两亲性α螺旋，该螺旋插入双层膜中。这使得该蛋白能够利用其两个与PI3P和PI(3,5)P结合的脂质结合位点。PI(3,5)P诱导Atg18寡聚化，这应该会使插入脂质的α螺旋在外膜小叶中聚集，并驱动膜的管状化和切割。Atg18的切割活性与其在内溶酶体蛋白运输、自噬体生物发生和液泡分裂中的已知作用是一致的。Atg18进行膜管状化和切割所需的关键特征也存在于其他PROPPIN蛋白中，这表明膜切割可能是该蛋白家族的一个普遍功能。
