Continuous self-repair protects vimentin intermediate filaments from fragmentation

• 成果类型: Article
• 署名作者: Tran, Quang D.; Lenz, Martin; Lamour, Guillaume; Paty, Lilian; Varela-Salgado, Maritzaida; Campilo, Clemen; Wioland, Hugo; Jegou, Antoine; Romet-Lemonne, Guillaume; Leduc, Cecile
• 署名单位: Universite Paris Cite; Centre National de la Recherche Scientifique (CNRS); Centre National de la Recherche Scientifique (CNRS); Universite Paris Saclay; Universite Paris Cite; Sorbonne Universite; Universite PSL; Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI); CY Cergy Paris Universite; Centre National de la Recherche Scientifique (CNRS); Institut Universitaire de France; Brandeis University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-8724
• DOI: 10.1073/pnas.2417660122
• 发表日期: 2025-06-17
• 关键词: posttranslational modifications; identification; exchange; proteins; DYNAMICS; subunits; reveals

摘要

Intermediate filaments are key regulators of cell mechanics. Vimentin, a type of intermediate filament expressed in mesenchymal cells and involved in migration, forms a dense network in the cytoplasm that is constantly remodeling through filament transport, elongation/shortening, and subunit exchange. While it is known that filament elongation involves end-to-end annealing, the reverse process of filament shortening by fragmentation remains unclear. Here, we use a combination of in vitro reconstitution, probed by fluorescence imaging and atomic force microscopy, with theoretical modeling to uncover the molecular mechanism involved in filament breakage. We first show that vimentin filaments are composed of two populations of subunits, half of which are exchangeable and half immobile. We also show that the exchangeable subunits are tetramers. Furthermore, we reveal a mechanism of continuous filament self-repair, where a soluble pool of vimentin tetramers in equilibrium with the filaments is essential to maintain filament integrity. Filaments break due to local fluctuations in the number of tetramers per cross-section, induced by the constant subunit exchange. We determine that a filament tends to break if approximately four tetramers are removed from the same filament cross-section. Finally, we analyze the dynamics of association/dissociation and fragmentation to estimate the binding energy of a tetramer to a complete versus a partially disassembled filament. Our results provide a comprehensive description of vimentin turnover and reveal the link between subunit exchange and fragmentation.