Aggregation and loss of cytokeratin filament networks inhibit Golgi organization in liver‐derived epithelial cell lines

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Abstract
Intermediate filaments are one of the three major cytoskeletons. Some roles of intermediate filaments in cellular functions have emerged based on various diseases associated with mutations of cytokeratins. However, the precise functions of intermediate filament are still unclear. To resolve this, we manipulated intermediate filaments of cultured cells by expressing a mutant cytokeratin. Arginine 89 of cytokeratin18 plays an important role in intermediate filament assembly. The expression of green fluorescent protein‐tagged cytokeratin18 arg89cys induced aggregations and loss of the intermediate filament network composed of cytokeratins in liver‐derived epithelial cells, Huh7 and OUMS29, but only induced the formation of cytokeratin aggregates and did not affect the intermediate filament network of endogenous vimentin in HEK293. The expression of this mutant affected the distribution of Golgi apparatus and the reassembly of Golgi apparatus after perturbations by nocodazole or brefeldin A in both Huh7 and OUMS29, but not in HEK293. Our data show that loss of the original intermediate filament network, but not the existence of cytokeratin aggregates, induces redistribution of the Golgi apparatus. The original intact intermediate filament network is necessary for the organization of Golgi apparatus. Cell Motil. Cytoskeleton 57:37–52, 2004.