Resolving ESCRT-III Spirals at the Intercellular Bridge of Dividing Cells Using 3D STORM

TLDR

The ESCRT machinery drives membrane fission, with ESCRT‑III proteins assembling into helical filaments on membranes to mediate this process. The study aimed to map the dynamic structural organization of ESCRT‑III during mammalian cytokinetic abscission. Using 3D STORM imaging of endogenous IST1, the authors visualized ESCRT‑III assemblies at nanometer resolution. They resolved ring and spiral ESCRT‑III structures at distinct abscission stages, showed that spastin, specific ESCRT‑III components, and VPS4 are essential for proper organization, and provided direct evidence that ESCRT‑III forms helical filaments to mediate cytokinetic abscission, suggesting new mechanistic scenarios.

Abstract

The ESCRT machinery mediates membrane fission in a variety of processes in cells. According to current models, ESCRT-III proteins drive membrane fission by assembling into helical filaments on membranes. Here, we used 3D STORM imaging of endogenous ESCRT-III component IST1 to reveal the evolution of the structural organization of ESCRT-III in mammalian cytokinetic abscission. Using this approach, ESCRT-III ring and spiral assemblies were resolved and characterized at different stages of abscission. Visualization of IST1 structures in cells lacking the microtubule-severing enzyme spastin and in cells depleted of specific ESCRT-III components or the ATPase VPS4 demonstrated the contribution of these components to the organization and function of ESCRTs in cells. This work provides direct evidence that ESCRT-III proteins form helical filaments to mediate their function in cells and raises new mechanistic scenarios for ESCRT-driven cytokinetic abscission.