Ford Marijn G J, Mills Ian G, Peter Brian J, Vallis Yvonne, Praefcke Gerrit J K, Evans Philip R, McMahon Harvey T
MRC Laboratory of Molecular Biology, Cambridge, UK.
Nature. 2002 Sep 26;419(6905):361-6. doi: 10.1038/nature01020.
Clathrin-mediated endocytosis involves cargo selection and membrane budding into vesicles with the aid of a protein coat. Formation of invaginated pits on the plasma membrane and subsequent budding of vesicles is an energetically demanding process that involves the cooperation of clathrin with many different proteins. Here we investigate the role of the brain-enriched protein epsin 1 in this process. Epsin is targeted to areas of endocytosis by binding the membrane lipid phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P(2)). We show here that epsin 1 directly modifies membrane curvature on binding to PtdIns(4,5)P(2) in conjunction with clathrin polymerization. We have discovered that formation of an amphipathic alpha-helix in epsin is coupled to PtdIns(4,5)P(2) binding. Mutation of residues on the hydrophobic region of this helix abolishes the ability to curve membranes. We propose that this helix is inserted into one leaflet of the lipid bilayer, inducing curvature. On lipid monolayers epsin alone is sufficient to facilitate the formation of clathrin-coated invaginations.
网格蛋白介导的内吞作用涉及货物选择以及在蛋白质衣被的帮助下细胞膜出芽形成囊泡。在质膜上形成内陷小窝以及随后囊泡的出芽是一个能量需求很高的过程，这涉及网格蛋白与许多不同蛋白质的协同作用。在这里，我们研究了大脑富集蛋白 epsin 1 在这个过程中的作用。Epsin 通过与膜脂磷脂酰肌醇 -4,5- 二磷酸（PtdIns(4,5)P(2)）结合而靶向内吞作用区域。我们在此表明，epsin 1 与网格蛋白聚合作用相结合，在结合 PtdIns(4,5)P(2) 时直接改变膜曲率。我们发现 epsin 中两亲性α-螺旋的形成与 PtdIns(4,5)P(2) 结合相关联。该螺旋疏水区域上的残基发生突变会消除使膜弯曲的能力。我们提出这个螺旋插入脂质双层的一个小叶中，诱导曲率产生。在脂质单层上，单独的 epsin 就足以促进网格蛋白包被的内陷的形成。
