Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, United States.
Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States.
Elife. 2016 Apr 13;5:e15507. doi: 10.7554/eLife.15507.
The endosomal sorting complexes required for transport (ESCRT) pathway facilitates multiple fundamental membrane remodeling events. Previously, we determined X-ray crystal structures of ESCRT-III subunit Snf7, the yeast CHMP4 ortholog, in its active and polymeric state (Tang et al., 2015). However, how ESCRT-III activation is coordinated by the upstream ESCRT components at endosomes remains unclear. Here, we provide a molecular explanation for the functional divergence of structurally similar ESCRT-III subunits. We characterize novel mutations in ESCRT-III Snf7 that trigger activation, and identify a novel role of Bro1, the yeast ALIX ortholog, in Snf7 assembly. We show that upstream ESCRTs regulate Snf7 activation at both its N-terminal core domain and the C-terminus α6 helix through two parallel ubiquitin-dependent pathways: the ESCRT-I-ESCRT-II-Vps20 pathway and the ESCRT-0-Bro1 pathway. We therefore provide an enhanced understanding for the activation of the spatially unique ESCRT-III-mediated membrane remodeling.
内体分选复合物需要运输 (ESCRT) 途径促进多个基本的膜重塑事件。以前，我们确定了 ESCRT-III 亚基 Snf7 的 X 射线晶体结构，酵母 CHMP4 同源物，在其活性和聚合状态（Tang 等人，2015 年）。然而，在上游 ESCRT 成分在内涵体中如何协调 ESCRT-III 的激活仍然不清楚。在这里，我们为结构相似的 ESCRT-III 亚基的功能分化提供了一个分子解释。我们描述了 ESCRT-III Snf7 的新型突变，这些突变触发了激活，并确定了酵母 ALIX 同源物 Bro1 在 Snf7 组装中的新作用。我们表明，上游 ESCRTs 通过两条平行的泛素依赖性途径调节 Snf7 在其 N 端核心结构域和 C 端α6 螺旋上的激活：ESCRT-I-ESCRT-II-Vps20 途径和 ESCRT-0-Bro1 途径。因此，我们为空间独特的 ESCRT-III 介导的膜重塑的激活提供了更深入的理解。
