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The organization of intermediate filaments in cultured epithelial cells was rapidly and radically affected by intracellularly injected monoclonal antikeratin filament antibodies. Different antibodies had different effects, ranging from an apparent splaying apart of keratin filament bundles to the complete disruption of the keratin filament network. Antibodies were detectable within cells for more than four days after injection. The antibody-induced disruption of keratin filament organization had no light-microscopically discernible effect on microfilament or microtubule organization, cellular morphology, mitosis, the integrity of epithelial sheets, mitotic rate, or cellular reintegration after mitosis. Cell-to-cell adhesion junctions survived keratin filament disruption. However, antibody injected into a keratinocyte-derived cell line, rich in desmosomes, brought on a superfasciculation of keratin filament bundles, which appeared to pull desmosomal junctions together, suggesting that desmosomes can move in the plane of the plasma membrane and may only be 'fixed' by their anchoring to the cytoplasmic filament network. Our observations suggest that keratin filaments are not involved in the establishment or maintenance of cell shape in cultured cells.
Klymkowsky et al. (Tue,) studied this question.