Targeting of lysosomal acid phosphatase with altered carbohydrate.
Human lysosomal acid phosphatase is transported as a transmembrane protein to lysosomes, where it is converted into a soluble protein by a limited proteolysis (Waheed et al., 1988, EMBO J. 7, 2351-2358). Transport of human lysosomal acid phosphatase in heterologous BHK-21 cells was examined under conditions that impair mannose-6-phosphate receptor-dependent transport, N-glycosylation or processing of N-linked oligosaccharides. Targeting of lysosomal acid phosphatase to lysosomes was neither affected by antibodies blocking the mannose-6-phosphate/IGF II receptor, nor by NH4Cl, which inhibited the mannose-6-phosphate receptor-dependent targeting of soluble lysosomal enzymes. 1-Deoxynojirimycin, 1-deoxymannojirimycin and swainsonine inhibited processing of N-linked oligosaccharides in lysosomal acid phosphatase without significantly affecting its transport. Tunicamycin inhibited N-glycosylation of lysosomal acid phosphatase. The non-glycosylated lysosomal acid phosphatase polypeptides accumulated within light membranes and were not transported to dense lysosomes. These results indicate that transport of lysosomal acid phosphatase is independent of mannose-6-phosphate receptors, does not involve an acid pH-dependent step and does not require processing of N-linked oligosaccharides. N-glycosylation appears to be necessary to achieve a transport competent form of lysosomal acid phosphatase.
Gottschalk
S
S
Universität Göttingen, Abt. Biochemie II.
Waheed
A
A
von Figura
K
K
D017485:1-Deoxynojirimycin; D000135:Acid Phosphatase / Q000302:isolation & purification* / Q000378:metabolism*; D000470:Alkaloids / Q000494:pharmacology; D000643:Ammonium Chloride / Q000494:pharmacology; D001345:Autoradiography; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D005944:Glucosamine / Q000031:analogs & derivatives / Q000494:pharmacology; D007425:Intracellular Membranes; D008247:Lysosomes / Q000201:enzymology*; D008565:Membrane Proteins; D009844:Oligosaccharides / Q000494:pharmacology; D017527:Receptor, IGF Type 2; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors; D017451:Receptors, Somatomedin; D012967:Sodium Dodecyl Sulfate; D013462:Sulfur Radioisotopes; D017026:Swainsonine; D014415:Tunicamycin / Q000494:pharmacology
D000470:Alkaloids; D008565:Membrane Proteins; D009844:Oligosaccharides; D017527:Receptor, IGF Type 2; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013462:Sulfur Radioisotopes; D000643:Ammonium Chloride; D014415:Tunicamycin; D017485:1-Deoxynojirimycin; D012967:Sodium Dodecyl Sulfate; D000135:Acid Phosphatase; D005944:Glucosamine; D017026:Swainsonine