Abstract
Continuous and regulated remodelling of the cytoskeleton is crucial for many basic cell functions. In contrast to actin filaments and microtubules, it is not understood how this is accomplished for the third major cytoskeletal filament system, which consists of intermediate-filament polypeptides. Using time-lapse fluorescence microscopy of living interphase cells, in combination with photobleaching, photoactivation and quantitative fluorescence measurements, we observed that epithelial keratin intermediate filaments constantly release non-filamentous subunits, which are reused in the cell periphery for filament assembly. This cycle is independent of protein biosynthesis. The different stages of the cycle occur in defined cellular subdomains: assembly takes place in the cell periphery and newly formed filaments are constantly transported toward the perinuclear region while disassembly occurs, giving rise to diffusible subunits for another round of peripheral assembly. Remaining juxtanuclear filaments stabilize and encage the nucleus. Our data suggest that the keratin-filament cycle of assembly and disassembly is a major mechanism of intermediate-filament network plasticity, allowing rapid adaptation to specific requirements, notably in migrating cells.
Highlights
The cytoplasmic cytoskeleton of mammalian cells is composed of three major filament networks – actin filaments, microtubules and intermediate filaments (IFs)
KF precursors (KFPs) grow by elongation and fusion until integration into the peripheral keratin IF (KF) network
Considering the abundance of keratin particles in the cell periphery of wounded and migrating cells, we wanted to know whether protein biosynthesis is sufficient to account for keratin assembly, as predicted by the dynamic co-translation model (Chang et al, 2006)
Summary
The cytoplasmic cytoskeleton of mammalian cells is composed of three major filament networks – actin filaments, microtubules and intermediate filaments (IFs). Spontaneous self-assembly of tetramers into unit-length filaments (ULFs), followed by compaction and longitudinal annealing, occurs – at least in vitro – without nucleoside triphosphates and additional cofactors (Herrmann et al, 2007; Kim and Coulombe, 2007). How these in vitro observations relate to the in vivo situation and how assembly is regulated is not understood
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
