166: Molecular Squeezing: How Coronin, Cofilin, and AIP1 Rapidly Disassemble Actin Filaments

️ Episode 166: Molecular Squeezing: How Coronin, Cofilin, and AIP1 Rapidly Disassemble Actin Filaments In this episode of PaperCast Base by Base, we explore a Cell study that uses single-particle cryo-EM to reveal the stepwise, synergistic mechanism by which coronin, cofilin, and AIP1 drive rapid actin filament disassembly in eukaryotic cells. Study Highlights:The authors solve a series of cryo-EM structures showing that coronin binds cooperatively to F-actin, opens a molecular backdoor to accelerate inorganic phosphate release, and undertwists the filament to prime it for cofilin binding. Cofilin then binds in a strand-restricted cooperative manner that converts subunits to a C-actin state and sterically displaces coronin without immediately severing the filament. AIP1 recognizes the cofilactin platform and triggers severing via a clamp-like molecular squeezing mechanism while remaining at the barbed end to cap it. This structural choreography explains how rapid filament turnover can occur at high cellular cofilin concentrations and clarifies the distinct roles of each factor in actin dynamics. Conclusion:By redefining AIP1 as the severing effector acting on cofilactin while capping the barbed end, the work provides a unifying structural model for fast actin network disassembly and points to testable predictions for reconstituted and cellular systems. Reference:Oosterheert W, Boiero Sanders M, Hofnagel O, Bieling P, Raunser S. Choreography of rapid actin filament disassembly by coronin, cofilin, and AIP1. Cell. 2025;188:1–16. https://doi.org/10.1016/j.cell.2025.09.016 License:This episode is based on an open-access article published under the Creative Commons Attribution 4.0 International License (CC BY 4.0) – https://creativecommons.org/licenses/by/4.0/ Support:If you'd like to support Base by Base, you can make a one-time or monthly donation here: https://basebybase.castos.com/ On PaperCast Base by Base you’ll discover the latest in genomics, functional genomics, structural genomics, and proteomics.