CATABOLISM AND LOSS OF PROTEOGLYCANS FROM CULTURES OF BOVINE COLLATERAL LIGAMENT

This paper investigates the kinetics and mechanism of loss of the two major proteoglycan species from cultures of bovine collateral ligament . Following incubation of ligament with [S-35]sulfate after 6 days in culture, the rate of loss of the predominant proteoglycan species, dec orin, from the matrix was shown to be much slower (t(1/2) similar to 1 8 days) than that of the large chondroitin sulfate proteoglycan (t(1/2 ) similar to 1.4 days). Analysis of S-35-labeled proteoglycans release d into the medium between Days 11 and 15 of the culture period on a co lumn of Sepharose CL-4B revealed that these macromolecules constituted mainly decorin of similar hydrodynamic size to that present in the ma trix. Furthermore, analysis of core proteins using gel electrophoresis followed by fluorography or immunodetection with LF-94, an antibody d irected against the amino-terminal region of decorin, indicated that t he core proteins of decorin released into the medium and those remaini ng in the matrix of ligament cultures had a similar molecular mass (si milar to 49 kDa). Analysis of both the S-35-labeled and endogenous mac romolecules using 5/6/3-B-3, an antibody directed against terminal uns aturated chondroitin-6-sulfate disaccharides, revealed that three core proteins with molecular masses greater than similar to 200 kDa were p resent in the matrix. Four additional core proteins (range similar to 80-200 kDa) derived from the large proteoglycan were detected in the m edium of ligament cultures. These findings indicate that, unlike decor in, the loss of the large chondroitin sulfate proteoglycan from the ma trix of ligament cultures involved proteolytic cleavage of its core pr otein. No difference in the hydrodynamic size of the S-35-labeled glyc osaminoglycan chains derived from either proteoglycan species remainin g in the matrix or released into the medium of ligament cultures was o bserved. (C) 1996 Academic Press, Inc.