Catabolism of newly synthesized decorin in vitro by human peritoneal mesothelial cells.
OBJECTIVE
Previous studies have shown that decorin and biglycan account for over 70% of the proteoglycans (PGs) synthesized by human peritoneal mesothelial cells (HPMCs). Since these PGs are involved in the control of cell growth, cell differentiation, and matrix assembly, we investigated their turnover in cultured HPMCs.


METHODS
Confluent HPMCs were metabolically labeled with [35S]-sulfate and the labeled products isolated from the cell medium and the cell layer characterized by sensitivity to bacterial eliminases. Experiments were undertaken with exogenous labeled decorin, and its metabolic state was studied.


RESULTS
In a 24-hour labeling period, 75% of the newly synthesized chondroitin sulfate/dermatan sulfate (CS/DS) PGs appeared in the culture medium, the majority of which (90%) was decorin. In the cell layer, protein-free glycosaminoglycan (GAG) chains accounted for 21% of the total CS/DS at 24 hours and exhibited constant specific activity at 12-16 hours. The latter material was turned over with a half-life of approximately 2.5 hours. Exogenous decorin underwent receptor-mediated endocytosis and subsequent intracellular degradation. Uptake but not degradation could be inhibited by heparin.


CONCLUSIONS
HPMCs are distinguished by a rapid turnover of decorin. A characteristic metabolic feature is the existence of a large intracellular pool of protein-free DS-GAGs. Understanding the control of decorin turnover in HPMCs might lead to delineation of its potential role in both the physiology and pathophysiology of the membrane in PD patients.
Yung
Susan
S
Institute of Nephrology, University of Wales College of Medicine, Heath Park, Cardiff, Wales, United Kingdom.
Hausser
Heinz
H
Thomas
Gareth
G
Schaefer
Liliana
L
Kresse
Hans
H
Davies
Malcolm
M
D018929:Cell Culture Techniques; D002809:Chondroitin Sulfates / Q000096:biosynthesis; D058575:Decorin; D003871:Dermatan Sulfate / Q000096:biosynthesis; D004705:Endocytosis; D004847:Epithelial Cells / Q000378:metabolism*; D016326:Extracellular Matrix Proteins; D006801:Humans; D009852:Omentum / Q000166:cytology* / Q000378:metabolism; D011509:Proteoglycans / Q000378:metabolism*
C546878:DCN protein, human; D058575:Decorin; D016326:Extracellular Matrix Proteins; D011509:Proteoglycans; D003871:Dermatan Sulfate; D002809:Chondroitin Sulfates