Oct 1, 1989

Epidermal growth factor-induced selective phosphorylation of cultured rat hepatocyte 55-kD cytokeratin before filament reorganization and DNA synthesis

The Journal of Cell Biology
H BaribaultN Marceau


We have reported previously that the addition of dexamethasone to cultured quiescent suckling rat hepatocytes in the presence of insulin, a culture condition which does not cause growth activation, induces a selective increase in the synthesis of the 49-kD/55-kD cytokeratin (CK49/CK55) pair over a 24-h period. This increased synthesis coincides with the formation of dense filament networks reminiscent of those observed in situ at the cell periphery (Marceau, N., H. Baribault, and I. Leroux-Nicollet. 1985. Can. J. Biochem. Cell Biol. 63:448-457). We show here for the first time that when EGF is added 48 h after insulin and dexamethasone, there is an early preferential phosphorylation of the CK55 of the CK49/CK55 pair, an induced filament rearrangement from the cell periphery to the cytoplasm, and a subsequent entry into S phase and mitosis after a lag period of 8 h. Indirect immunofluorescence microscopy with monoclonal antibodies to CK49 and CK55 indicate that, while before EGF treatment the cytokeratin filaments were mainly distributed near the cell periphery, the addition of EGF resulted in their reorganization to a predominantly cytoplasmic localization within less than 3 h. Antitubulin and anti-actin antibodies showed no de...Continue Reading

Mentioned in this Paper

Immunofluorescence Assay
Epidermal Growth Factor
Rats, Inbred F344
DNA Replication
Microtrabecular Lattice

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