Document Detail

Chondroitin sulfate is involved in lysosomal transport of lysozyme in U937 cells.
MedLine Citation:
PMID:  11148136     Owner:  NLM     Status:  MEDLINE    
Human promonocytes U937 synthesize lysozyme and retain approximately one third of it within lysosomes. Lysozyme is not glycosylated; thus, it cannot be subject to mannose-6-phosphate-dependent targeting to lysosomes. It is a basic protein with a pI of 10.5 and is known to interact with negatively charged macromolecules like proteoglycans. Therefore, we examined whether the latter are involved in the lysosomal targeting of lysozyme in U937 cells. We partially diminished the electronegative charge of newly synthesized proteoglycans by inhibiting their sulfation with chlorate. This increased the rate of secretion of lysozyme. Upon treatment of U937 cells with phorbol esters, the rate of secretion of lysozyme was increased to more than 90%. This coincided with an almost complete redistribution of a [(35)S]sulfate bearing proteoglycan to the secretory pathway. After a brief pulse with [(35)S]sulfate in the control, 80% of the [(35)S]sulfate-bearing proteoglycan was retained within the cells, whereas in the treated cells this proportion was decreased to 13%. The secreted proteoglycan was sensitive to chondroitinase ABC and bound to immobilized lysozyme. This interaction was disrupted by 50-300 mM NaCl. The intracellularly retained proteoglycan was degraded with a half-life of 50-60 minutes and seemed to be directed to lysosomes because in the presence of NH(4)Cl the degradation was strongly inhibited. Our results suggest that the proteoglycan is involved in lysosomal targeting of lysozyme in U937 cells.
P Lemansky; A Hasilik
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of cell science     Volume:  114     ISSN:  0021-9533     ISO Abbreviation:  J. Cell. Sci.     Publication Date:  2001 Jan 
Date Detail:
Created Date:  2001-01-26     Completed Date:  2001-05-17     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  0052457     Medline TA:  J Cell Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  345-52     Citation Subset:  IM    
Philipps-Universität Marburg, Institut für Physiologische Chemie, Karl-von-Frisch-Strasse 1, Germany.
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MeSH Terms
Ammonium Chloride / pharmacology
Chondroitin ABC Lyase
Chondroitin Sulfates / biosynthesis,  isolation & purification,  metabolism*
Chromatography, Affinity
Enzymes, Immobilized / chemistry,  metabolism
Lysosomes / drug effects,  metabolism*
Mannosephosphates / metabolism
Muramidase / chemistry,  metabolism*
Perchloric Acid / pharmacology
Protein Binding
Protein Transport
Proteoglycans / metabolism
Sodium Compounds / pharmacology
Sulfates / metabolism
Sulfur Radioisotopes
Tetradecanoylphorbol Acetate / pharmacology
U937 Cells
Reg. No./Substance:
0/Enzymes, Immobilized; 0/Mannosephosphates; 0/Proteoglycans; 0/Sodium Compounds; 0/Sulfates; 0/Sulfur Radioisotopes; 12125-02-9/Ammonium Chloride; 16561-29-8/Tetradecanoylphorbol Acetate; 3672-15-9/mannose-6-phosphate; 7601-89-0/sodium perchlorate; 7601-90-3/Perchloric Acid; 9007-28-7/Chondroitin Sulfates; EC; EC ABC Lyase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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