UNUSUAL PROCESSING OF GP280, A PROTEIN ASSOCIATED WITH THE INTERMICROVILLAR AREAS OF YOLK-SAC EPITHELIAL-CELLS - PLASMA-MEMBRANE DELIVERY OF IMMATURE PROTEIN

We have previously shown the close association with endocytosis of 2 g lycoproteins, gp330 and gp280, expressed within the clathrin coated in termicrovillar areas of epithelial cells lining the proximal tubule an d visceral layer of the yolk sac. Exposure at 37 degrees C of yolk sac epithelial cells in the presence of antibodies to gp280 induced disru ption of the early endocytic pathway whereas anti-gp330 antibodies did not. In this study, using yolk sac epithelial cells in culture, we sh ow that, in contrast to gp330 which is processed by the Golgi enzymes before expression on the plasma membrane, gp280 follows an unusual pro cessing pathway : indeed, although the bulk of the plasma membrane gp2 80 is endoglycosidase H resistant, the protein is initially targeted t o the plasma membrane in an endoglycosidase Il sensitive form. This im plies that processing takes place mainly, if not exclusively, by recyc ling in the Golgi apparatus. (C) 1995 Academic Press, Inc.