Inhibition of protein kinase C-dependent protein phosphorylation correlates with increased polarity and locomotion in Walker 256 carcinosarcoma cells

✍ Scribed by Verena Niggli; Arthur Zimmermann; Hansuli Keller

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: French
• Weight: 746 KB
• Volume: 65
• Category: Article
• ISSN: 0020-7136
• DOI: 10.1002/(sici)1097-0215(19960208)65:4<473::aid-ijc14>3.0.co;2-b

✦ Synopsis

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.