Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, United States; Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
Nicholas J Buchkovich
Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, United States; Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
W Mike Henne
Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, United States; Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
Sudeep Banjade
Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, United States; Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
Yun Jung Kim
Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, United States; Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, United States; Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
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.
