Changes in the distribution of a major fibroblast protein, fibronectin, during mitosis and interphase

Abstract

The distribution of a major fibroblast protein, fibronectin, was studied by immunofluorescence and immunoscanning electron microscopy in cultures of human and chicken fibroblasts during different phases of the cell cycle. In interphase cells, the intensity of surface-associated fibronectin fluorescence correlated with that of intracellular fibronectin fluorescence. The intensity of the fluorescence of surface-associated and intracellular fibronectins was not changed in cells that were synthesizing DNA. Mitotic cells had reduced amounts of surface-associated but not of intracellular fibronectin. The surface fibronectin that remained on meta-, ana- or telophase cells had a distinct punctate distribution and was localized to strands attaching the cells to the substratum. Fibronectin strands first reappeared on the surface of flattening cytoplasmic parts of telophase cells. Fibronectin was detected in extracellular fibrillar material on the growth substratum, particularly around dividing cells. Surface-associated fibrillar fibronectin was present during G1, S and G2, but in cells undergoing mitosis the distribution was altered and the amount appeared to be reduced. The observations on the distribution of surface-associated fibronectin suggest that rather than being involved in growth control this fibronectin plays a structural role in interactions of cells with the environment.