Document Detail

Defective acidification of intracellular organelles results in aberrant secretion of cathepsin D in cancer cells.
MedLine Citation:
PMID:  15258139     Owner:  NLM     Status:  MEDLINE    
Aberrant secretion of lysosomal hydrolases such as (pro)cathepsin D (proCD) is a common phenotypic change in many human cancers. Here we explore the underlying molecular defect(s) and find that MCF-7 breast and CaCo-2 colorectal cancer cells that are unable to acidify their endosomal compartments secreted higher amounts of proCD than did acidification-competent cancer cell types. The latter secreted equivalent amounts of proCD only after dissipation of their organellar pH gradients with NH(4)Cl. Assessing the critical steps that resulted in proCD secretion revealed that the Golgi-associated sorting receptor for CD, i.e. the cation-independent mannose-6-phosphate receptor (MPR300), was aberrantly distributed in acidification-defective MCF-7 cells. It accumulated mainly in late endosomes and/or lysosomes as a complex with its ligand (proCD or intermediate CD), as evidenced by its co-localization with both CD and LAMP-2, a late endosome/lysosome marker. Our immunoprecipitation analyses also showed that MCF-7 cells possessed 7-fold higher levels of receptor-enzyme complexes than did acidification-competent cells. NH(4)Cl induced similar receptor redistribution into LAMP-2-positive structures in acidification-competent cells but not in MCF-7 cells. The receptor also recovered its normal Golgi localization upon drug removal. Based on these observations, we conclude that defective acidification results in the aberrant secretion of proCD in certain cancer cells and interferes mainly with the normal disassembly of the receptor-enzyme complexes and efficient receptor reutilization in the Golgi.
Nina Kokkonen; Antti Rivinoja; Annika Kauppila; Marko Suokas; Ilmo Kellokumpu; Sakari Kellokumpu
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2004-07-16
Journal Detail:
Title:  The Journal of biological chemistry     Volume:  279     ISSN:  0021-9258     ISO Abbreviation:  J. Biol. Chem.     Publication Date:  2004 Sep 
Date Detail:
Created Date:  2004-09-13     Completed Date:  2004-10-25     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:  39982-8     Citation Subset:  IM    
Department of Biochemistry, University of Oulu, P. O. Box 3000, FIN-90014 Oulu, Finland.
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MeSH Terms
Acids / metabolism*
Ammonium Chloride / pharmacology
Antigens, CD / metabolism
Breast Neoplasms
COS Cells
Caco-2 Cells
Cathepsin D / metabolism*,  secretion*
Diuretics / pharmacology
Endosomes / drug effects,  metabolism
Golgi Apparatus / drug effects,  metabolism*
HT29 Cells
Lysosome-Associated Membrane Glycoproteins
Lysosomes / drug effects,  metabolism
Reg. No./Substance:
0/Acids; 0/Antigens, CD; 0/Diuretics; 0/Lysosome-Associated Membrane Glycoproteins; 12125-02-9/Ammonium Chloride; EC D

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