title: The cation-independent mannose 6-phosphate receptor is involved in lysosomal delivery of serglycin.
abstract: To clarify the sorting mechanism of the lysosomal/granular proteoglycan serglycin, we treated human promonocytic U937 cells with p-nitrophenyl-beta-D-xyloside (PNP-xyl) and cycloheximide. In the absence of protein synthesis, the carbohydrate moiety of serglycin was synthesized as PNP-xyl-chondroitin sulfate (CS), and most of it was delivered to lysosomes and degraded. Further, an augmented lysosomal targeting of serglycin in the presence of tunicamycin suggested that a sorting/lectin receptor with multiple specificity was involved with an increased capacity for serglycin in the absence of N-glycosylation. Correspondingly, the cation-independent mannose 6-phosphate receptor (CI-MPR) and sortilin were observed to bind to immobilized CS. These receptors were eluted in the presence of 200-400 mM and 100-250 mM NaCl, respectively. After treating the cells with a cross-linking reagent, a portion of the sulfated proteoglycan was coimmunoprecipitated with the CI-MPR but not with sortilin. In the presence of phorbol ester, lysosomal targeting of serglycin and to a lesser extent, of cathepsin D was inhibited. We conclude that the CI-MPR participates in lysosomal and granular targeting of serglycin and basic proteins such as lysozyme associated with the proteoglycan in hematopoietic cells.
authors.affiliation: Institut für Physiologische Chemie, Philipps-Universität Marburg, Germany. lemansky@staff.uni-marburg.de
authors.forename: Peter
authors.initials: P
authors.lastname: Lemansky
authors.forename: Ines
authors.initials: I
authors.lastname: Fester
authors.forename: Eva
authors.initials: E
authors.lastname: Smolenova
authors.forename: Christoph
authors.initials: C
authors.lastname: Uhländer
authors.forename: Andrej
authors.initials: A
authors.lastname: Hasilik
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport; D001692:Biological Transport; D002412:Cations / Q000737:chemistry; D002809:Chondroitin Sulfates / Q000737:chemistry; D002846:Chromatography, Affinity; D003432:Cross-Linking Reagents / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D047468:Immunoprecipitation; D008247:Lysosomes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism; D014176:Protein Biosynthesis; D011509:Proteoglycans / Q000378:metabolism*; D017527:Receptor, IGF Type 2 / Q000378:metabolism* / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014415:Tunicamycin / Q000494:pharmacology; D020298:U937 Cells; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D000099183:Sortilin
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D002412:Cations; D002809:Chondroitin Sulfates; D003432:Cross-Linking Reagents; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D011509:Proteoglycans; D017527:Receptor, IGF Type 2; D013755:Tetradecanoylphorbol Acetate; D014415:Tunicamycin; D033921:Vesicular Transport Proteins; D000099183:Sortilin; C075430:serglycin