Daz filament5/3/2023 ![]() This scaffolding is not simply a static system conferring stability on cells, but is highly dynamic and capable of rapid reorganization in response to various extracellular and intracellular stimuli. The cytoplasmic cytoskeleton of mammalian cells is composed of three major filament networks – actin filaments, microtubules and intermediate filaments (IFs). 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. ![]() Remaining juxtanuclear filaments stabilize and encage the nucleus. 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. This cycle is independent of protein biosynthesis. 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. ![]() 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. Continuous and regulated remodelling of the cytoskeleton is crucial for many basic cell functions.
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