BIOSYNTHESIS AND APICAL LOCALIZATION OF THE UROKINASE RECEPTOR IN POLARIZED MDCK EPITHELIAL-CELLS

The biosynthesis and the surface localization of the urokinase plasmin ogen activator receptor (uPaR) were analysed in MDCK epithelial cells and in unpolarized fibroblasts. No differences were observed with resp ect to rate of synthesis, nature of precursors and time of surface app earance. uPAR,vas localized particularly at the focal and cell-cell co ntacts when expressed in fibroblasts. On the contrary, in MDCK cells u PAR was found mostly on the apical surface; in agreement with its loca lization, down-regulation of uPAR by the uPA-PAI-1 complex was observe d only from the apical membrane.