Targeting of the SF/HGF receptor to the basolateral domain of polarized epithelial cells.

Abstract

Scatter Factor, also known as Hepatocyte Growth Factor (SF/HGF), has pleiotropic functions including direct control of cell-cell and cell-substrate adhesion in epithelia. The subcellular localization of the SF/HGF receptor is controversial. In this work, the cell surface distribution of the SF/HGF receptor was studied in vivo in epithelial tissues and in vitro in polarized MDCK monolayers. A panel of monoclonal antibodies against the beta chain of the SF/HGF receptor stained the basolateral but not the apical surface of epithelia lining the lumen of human organs. Radiolabeled or fluorescent-tagged anti-receptor antibodies selectively bound the basolateral cell surface of MDCK cells, which form a polarized monolayer sealed by intercellular junctions, when grown on polycarbonate filters in a two-chamber culture system. The receptor was concentrated around the cell-cell contact zone, showing a distribution pattern overlapping with that of the cell adhesion molecule E-cadherin. The basolateral localization of the SF/HGF receptor was confirmed by immunoprecipitation after domain selective cell surface biotinylation. When cells were fully polarized the SF/HGF receptor became resistant to non-ionic detergents, indicating interaction with insoluble component(s). In pulse-chase labeling and surface biotinylation experiments, the newly synthesized receptor was found exclusively at the basolateral surface. We conclude that the SF/HGF receptor is selectively exposed at the basolateral plasma membrane domain of polarized epithelial cells and is targeted after synthesis to that surface by direct delivery from the trans-Golgi network.