HEPATOCYTE GROWTH FACTOR-INDUCED SCATTER OF MADIN-DARBY CANINE KIDNEY-CELLS REQUIRES PHOSPHATIDYLINOSITOL 3-KINASE

Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional cytokine that induces mitogenesis, motility, invasion, and morphogenesis of several epithelial and endothelial cell lines in culture. The receptor for HGF/SF has been identified as the Met tyrosine kinase. To investigate the signaling pathways that are involved in these events, we have generated chimeric receptors containing the extracellular domain of the colony stimulating factor-1 (CSF-1) receptor fused to the transmembrane and intracellular domains of the Met receptor (MET). Madin-Darby canine kidney (MDCK) epithelial cells expressing the CSF-MET chimera dissociate and scatter in response to CSF-1. However, cells expressing a mutant CSF-MET receptor containing a phenylalanine substitution for tyrosine 1356 were unable to scatter or form branching tubules following stimulation with CSF-1. Tyrosine 1356 is essential for the recruitment of multiple substrates including the p85 subunit of PI3-kinase, phospholipase C gamma, and Grb2. In this study, we have investigated the role of PI3-kinase and a downstream target of PI3-kinase, pp70(S6K), in the induction of MDCK cell scatter in response to HGF/SF. Our results demonstrate that following stimulation with HGF/SF, activation of PI3-kinase but not pp70(S6K) is essential for MDCK cell scatter.