Document Detail


Synthesis and transport of lysosomal acid phosphatase in normal and I-cell fibroblasts.
MedLine Citation:
PMID:  3160696     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The biosynthesis, proteolytic processing, and transport of lysosomal acid phosphatase in normal and I-cell human skin fibroblasts was studied by metabolic labeling of the cells and isolation of acid phosphatase by immunoprecipitation. Several forms of the enzyme were identified in pulse-chase experiments. The largest precursor form had a Mr of 110,000. It was accompanied by several smaller polypeptides (Mr = 84,000-62,000), which were localized to light membranes containing the markers of endoplasmic reticulum and Golgi complex. These polypeptides were further processed to mature forms with apparent Mr of 57,000, 48,000, and 43,000 that accumulated in the cells and were associated with dense lysosomes. Less than 10% of newly synthesized acid phosphatase was secreted mainly as Mr = 112,000 and 74,000 forms. The processing of acid phosphatase was inhibited by NH4Cl and by a peptidyldiazomethyl ketone inhibitor of cysteine proteinases. The intracellular Mr = 110,000, 57,000, and 48,000 and the secreted Mr = 112,000 and 64,000 forms contained phosphorylated oligosaccharides cleavable by endo-beta-N-acetylglucosaminidase H. Transport of acid phosphatase into lysosomes was sensitive to NH4Cl and dependent on mannose 6-phosphate specific receptors by the following criteria: (i) inhibition of endocytosis of acid phosphatase by mannose 6-phosphate, (ii) enhancement of the secretion of acid phosphatase in the presence of antibodies to the mannose 6-phosphatase specific receptor, and (iii) secretion of about two-thirds of newly synthesized acid phosphatase in I-cell fibroblasts. Obviously, the mechanism of transport of acid phosphatase into lysosomes is indistinguishable from that operating for other lysosomal enzymes in fibroblasts. In contrast to other lysosomal enzymes, acid phosphatase appears to be subjected to an early proteolytic processing, presumably within the endoplasmic reticulum, which results in secretion of several processed forms of the enzyme.
Authors:
P Lemansky; V Gieselmann; A Hasilik; K von Figura
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  260     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  1985 Jul 
Date Detail:
Created Date:  1985-08-28     Completed Date:  1985-08-28     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  2985121R     Medline TA:  J Biol Chem     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  9023-30     Citation Subset:  IM    
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MeSH Terms
Descriptor/Qualifier:
Acid Phosphatase / metabolism*
Ammonium Chloride / pharmacology
Biological Transport
Carrier Proteins / physiology
Endocytosis
Fibroblasts / enzymology
Humans
Lysosomes / enzymology*
Molecular Weight
Mucolipidoses / enzymology*
Oligosaccharides / analysis
Phosphopeptides / analysis
Receptor, IGF Type 2
Solubility
Chemical
Reg. No./Substance:
0/Carrier Proteins; 0/Oligosaccharides; 0/Phosphopeptides; 0/Receptor, IGF Type 2; 12125-02-9/Ammonium Chloride; EC 3.1.3.2/Acid Phosphatase

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