title: Characterization of the mannose 6-phosphate receptor (Mr 300 kDa) protein dependent pathway of lysosomal enzyme targeting in Biomphalaria glabrata mollusc cells.
abstract: Mammalian mannose 6-phosphate receptors (MPR 300 and 46) are involved in the targeting of newly synthesized lysosomal enzymes and only MPR 300 also participates in the endocytosis of various exogenous ligands. The present study describes for the first time the MPR 300 dependent pathway of lysosomal enzyme sorting in the Biomphalaria glabrata embryonic (Bge) cells. Lysosomal enzymes (arylsulfatase A, beta-hexosaminidase and alpha-fucosidase) were identified by their enzymatic activities and by immunoprecipitation with specific antisera. Exposure of Bge cells to unio MPR 300 antiserum resulted in a dramatic loss of MPR 300 protein with a shortened half life of approximately 20 min as compared to control cells exposed to preimmune serum in which the half life of MPR 300 was of approximately 13 h. Loss of receptor proteins resulted in a significant misrouting of newly synthesized lysosomal enzymes and their secretion in cell culture medium as demonstrated by immunoprecipitation. The ability of Bge cells to uptake and internalize labeled arylsulfatase A, beta-hexosaminidase and alpha-fucosidase enzymes contained in cell secretion products also indicated the role of B. glabrata MPR 300 (CIMPR) protein in internalization and targeting of lysosomal enzymes. M6P dependent binding of lysosomal enzymes to MPR 300 was shown by confocal microscopy and coimmunoprecipitation experiments.
authors.affiliation: Department of Biochemistry, University of Hyderabad, India.
authors.forename: Praveen Kumar
authors.initials: PK
authors.lastname: Amancha
authors.forename: Colette
authors.initials: C
authors.lastname: Dissous
authors.forename: Siva Kumar
authors.initials: SK
authors.lastname: Nadimpalli
mesh_terms: D000818:Animals; D001700:Biomphalaria / Q000166:cytology* / Q000196:embryology / Q000378:metabolism; D004705:Endocytosis; D016650:Fluorescein-5-isothiocyanate / Q000378:metabolism; D005696:Galactosidases / Q000378:metabolism; D007106:Immune Sera / Q000276:immunology; D047468:Immunoprecipitation; D007457:Iodine Radioisotopes / Q000378:metabolism; D008247:Lysosomes / Q000201:enzymology*; D021381:Protein Transport; D017527:Receptor, IGF Type 2 / Q000276:immunology / Q000378:metabolism*; D005644:alpha-L-Fucosidase / Q000378:metabolism
chemical_list: D007106:Immune Sera; D007457:Iodine Radioisotopes; D017527:Receptor, IGF Type 2; D005696:Galactosidases; D005644:alpha-L-Fucosidase; D016650:Fluorescein-5-isothiocyanate