title: Inhibition of protein kinase C-dependent protein phosphorylation correlates with increased polarity and locomotion in Walker 256 carcinosarcoma cells.
abstract: Signal transduction pathways controlling tumor cell locomotion are not yet well understood. We have studied the role of protein kinase C (PKC)-dependent protein phosphorylation associated with changes in cell shape and locomotor activity of Walker carcinosarcoma cells in culture. We show that the inhibitory effect of phorbol-12-myristate-13-acetate (PMA), an activator of PKC, on cell polarity and locomotion can be suppressed by the PKC-selective inhibitor Ro 31-8220. PMA induces increased phosphorylation of at least 2 proteins, of 65 and 80 kDa, in intact Walker carcinosarcoma cells. These bands are enriched in cytosolic fractions isolated from cells incubated with 32PO4. Pre-incubation with Ro 31-8220 inhibits the PMA-induced phosphorylation of both bands in a concentration-dependent manner. This effect is very likely not due to inhibition of translocation of PKC to the membrane as Ro 31-8220 enhances, rather than inhibits, PMA-induced transfer of PKC beta(II) to the particulate fraction. We have carried out a quantitative analysis of phosphorylation of the 80-kDa band. Ro 31-8220 reverses both PMA-induced phosphorylation of this band and PMA-induced suppression of cell polarity in parallel. Increased phosphorylation of proteins via PKC may thus be a stop signal for locomoting Walker carcinosarcoma cells.
authors.affiliation: Department of Pathology, University of Bern, Switzerland.
authors.forename: V
authors.initials: V
authors.lastname: Niggli
authors.forename: A
authors.initials: A
authors.lastname: Zimmermann
authors.forename: H
authors.initials: H
authors.lastname: Keller
mesh_terms: D000818:Animals; D002279:Carcinoma 256, Walker / Q000378:metabolism / Q000473:pathology*; D002465:Cell Movement; D016764:Cell Polarity; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D011506:Proteins / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D007211:Indoles; D011506:Proteins; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; C064758:Ro 31-8220