Effects of agents that modulate intracellular signal transduction, macromolecule synthesis and cytoskeleton assembly

Abstract

Scatter factor (SF) is a cytokine that causes cohesive epithelial colonies to ‘scatter’ into isolated cells and stimulates epithelial cell migration. To investigate SF’s mechanism(s), we screened agents that modulate various intracellular processes for effects on scattering of Madin-Darby canine kidney (MDCK) cells. Selected agents were studied in quantitative migration assays using microcarrier beads. Agents that activate the adenylate cyclase (AC) pathway caused mild to moderate inhibition of scattering and migration, while modulators of Ca2+/calmodulin pathways had little effect on scattering. In contrast, phorbol esters (PMA, PDD) and protein kinase C (PKC) inhibitors (staurosporine, H-7, 7,8-dihydroxy-chlorpromazine) markedly enhanced and accelerated scattering; PMA and staurosporine also stimulated migration. Diacylglycerol analogues (e.g. diC8), naphthalenesulfonamide PKC activators (SC-9, SC-10) and inactive phorbol esters (e.g. 4a-PDD) did not potentiate scattering, while PKC depletion by 48 h pre-incubation with PMA markedly stimulated scattering. Thus, PMA-enhanced scattering may be related to down-modulation of PKC. Scattering was blocked by inhibitors of protein and RNA but not DNA synthesis; SF- and agent-stimulated migration were ablated by cycloheximide. Scattering and migration were inhibited by an anti-microfilament (cytochalasin B) but not anti-microtubule (e.g. colce-mid) agents. These findings suggest that SF-induced epithelial mobility may be mediated, in part, by protein synthesis, alterations in protein phosphorylation (?inhibition of PKC), and actin filament reorganization. They indicate directions for further studies.