LOCAL INCREASE OF BETA-1-INTEGRIN EXPRESSION IN COCULTURES OF IMMORTALIZED HEPATOCYTES AND SINUSOIDAL ENDOTHELIAL-CELLS

The expression and spatial arrangement of beta 1-integrins was determi ned on two immortalized liver cell lines held in coculture, namely the epithelial cell line mHepR1 and a sinusoidal endothelial cell line. O n mHepR1 cells the distribution of beta 1-integrins was restricted to the basolateral plasma membrane domains, a staining pattern that is ty pical of polarized epithelial cells. On the endothelial cell line the beta 1-integrins were distributed all over the cell surface. In cocult ure the endothelial cells tended to cover over the epithelial cells. E pithelial cells located in their vicinity exhibited an increased stain ing of beta 1-integrins at basolateral plasma membrane domains, which was most prominent with regard to the alpha 2-subunit. When mHepR1 cel ls were cultivated on various types of extracellular matrix also synth esized by the endothelial cells only collagen IV was found to increase the intensity of beta 1-integrin expression at the cell surface. The results indicate that beta 1-integrin expression in epithelial cell co lonies can locally be modulated by interactions with non parenchymal c ells. In addition, the data suggest that mHepR1 cells may be a favorab le system for analyzing basic functions of beta 1-integrins in polariz ed epithelial cells.