Acrylamide treatment of PtK1 cells causes dephosphorylation of keratin polypeptides.

Treatment of PtKl cells with 5 mM acrylamide for 4 hr results in alterations in the distribution of keratin filaments within the cells. This effect is reversible within 18 hr. Labeling of PtKl cells with 32P demonstrates that there are four phosphorylated keratins, having Mr of 56 k, 53 k, 45 k, and 40 k. Phosphate associated with these polypeptides appears to turn over with a t1/2 of 12 hr. Incubation of labeled cells in 5 mM acrylamide results in approximately 50% dephosphorylation of keratins within 2 hr, which is 3 times faster than normal turnover. Recovery of cells from acrylamide is accompanied by rephosphorylation of keratins within 18 hr. Analysis by 31P NMR spectroscopy shows that acrylamide treatments are accompanied by a transient decrease in soluble inorganic phosphate. This is followed by a rapid increase in Pi which gradually returns to normal levels. These studies show a strong correlation between phosphorylation of PtKl cell keratins and morphological response of keratin filaments to acrylamide. These observations suggest that normal distribution of keratin filaments may be, in part, mediated by protein phosphorylation.