[Analysis of keratin filament structural transformation in human epithelial cells]

Upon 2-3 hours cold treatment (0 degrees C), the keratin filaments of some PcaSE-1 cells and BEL-7404 cells are partly transformed into granular aggregates. But such structural transformation does not occur in HeLa cells and CNE cells. By rewarming (37 degrees C) cells within 15-30 minutes, this structural changes of keratin filaments in PcaSE-1 cells and BEL-7404 cells are readily reversed. In contrast, in HeLa cells and CNE cells, keratin filaments are transformed into granula aggregates during mitosis, but the keratin filament network in PcaSE-1 cells and BEL-7404 cells remained intact and encircled the developing mitotic spindle as the cells entered mitosis. Results suggest that the above two types of keratin filament structural transformation might be induced by different factors. Our results also indicate that: (1) PcaSE-1 cells treated with colchicine alone or with combination of colchicine and cytochalasin D does not cause granular aggregates of keratin filaments. However, after depolymerization of microtubules with colchicine, the response of the cells to cold treatment is intensified. (2) The aggregate formation during cold treatment is unrelated to whether epithelial cells contain two different type intermediate filaments or not. (3) Epithelial cells preextracted with Triton X-100 do not induce granular aggregate formation of keratin filaments upon cold treatment. (4) The structural transformation upon cold treatment may be a characteristic of keratin filaments of certain epithelial cell lines.