Epithelial rat liver cells have cell surface receptors recognizing a phosphorylated carbohydrate on lysosomal enzymes.
Receptor-mediated endocytosis of alpha-N-acetylglucosaminidase by cultured epithelial rat liver cells is inhibited by mannose, L-fucose and most effectively by mannose 6-phosphate. Endocytosis of alpha-N-acetylglucosaminidase is lost after treatment of the enzyme with alkaline phosphatase. These findings indicate that epithelial rat liver cells possess cell surface receptors that recognize a phosphorylated carbohydrate on alpha-N-acetylglucosaminidase, as was previously reported for cell surface receptors of human skin fibroblasts. Inhibition of alpha-mannosidase endocytosis by epithelial rat liver cells in the presence of mannose 6-phosphate and loss of enzyme endocytosis after treatment with alkaline phosphatase suggest that this enzyme is recognized by the same receptor.
D000118:Acetylglucosaminidase; D000469:Alkaline Phosphatase; D000818:Animals; D002241:Carbohydrates / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D004705:Endocytosis / Q000187:drug effects; D008099:Liver / Q000378:metabolism* / Q000648:ultrastructure; D008247:Lysosomes / Q000201:enzymology; D008361:Mannosidases; D051381:Rats; D011955:Receptors, Drug / Q000378:metabolism*
D002241:Carbohydrates; D011955:Receptors, Drug; D000469:Alkaline Phosphatase; D008361:Mannosidases; D000118:Acetylglucosaminidase