Abstract
We have studied the hyaluronate-binding properties of aggregating cartilage proteoglycans synthesized in vivo by immature (6-week), mature (25-week) and aged (75-week) rabbits. Precursor isotope (35SO4) was given by intra-articular injection and articular cartilage was removed from rabbits after periods ranging from 1.5 h to 168 h. Proteoglycans were extracted with 4 M-guanidinium/HCl and monomers were isolated by CsCl gradient centrifugation under dissociative conditions. The percentages of both radiolabelled and total tissue monomers with a high affinity for hyaluronate [that is, capable of forming aggregates on Sepharose CL-2B in the presence of 0.8% (w/w) hyaluronate] were then determined. For all samples about 30% of the tissue monomers were high-affinity; however, less than 5% of the radiolabelled monomers were high-affinity at 1.5 h after injection, and this figure increased gradually with time in vivo. The increase was rapid in immature rabbits, such that after 24 h, about 30% of the radiolabelled monomers were high-affinity; on the other hand for mature and aged rabbits the increase was markedly slower such that 30% high-affinity was attained only after about 72 h. The results show that aggregating cartilage proteoglycans are secreted in vivo in a 'precursor' form with a low affinity for hyaluronate, and suggest that conversion of these monomers to a form with a higher binding affinity occurs with a half-time of about 12 h in immature cartilages but greater than 24 h in mature cartilages. The possible relationship of these findings to the process of proteoglycan aggregation in vivo is discussed.
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Selected References
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- Bayliss M. T., Ridgway G. D., Ali S. Y. Delayed aggregation of proteoglycans in adult human articular cartilage. Biosci Rep. 1984 Oct;4(10):827–833. doi: 10.1007/BF01138164. [DOI] [PubMed] [Google Scholar]
- Bayliss M. T., Ridgway G. D., Ali S. Y. Differences in the rates of aggregation of proteoglycans from human articular cartilage and chondrosarcoma. Biochem J. 1983 Dec 1;215(3):705–708. doi: 10.1042/bj2150705. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Farndale R. W., Sayers C. A., Barrett A. J. A direct spectrophotometric microassay for sulfated glycosaminoglycans in cartilage cultures. Connect Tissue Res. 1982;9(4):247–248. doi: 10.3109/03008208209160269. [DOI] [PubMed] [Google Scholar]
- Kimura J. H., Hardingham T. E., Hascall V. C. Assembly of newly synthesized proteoglycan and link protein into aggregates in cultures of chondrosarcoma chondrocytes. J Biol Chem. 1980 Aug 10;255(15):7134–7143. [PubMed] [Google Scholar]
- Kimura J. H., Shinomura T., Thonar E. J. Biosynthesis of cartilage proteoglycan and link protein. Methods Enzymol. 1987;144:372–393. doi: 10.1016/0076-6879(87)44187-6. [DOI] [PubMed] [Google Scholar]
- Melching L. I., Roughley P. J. The role of link protein in mediating the interaction between hyaluronic acid and newly secreted proteoglycan subunits from adult human articular cartilage. J Biol Chem. 1985 Dec 25;260(30):16279–16285. [PubMed] [Google Scholar]
- Oegema T. R., Jr Delayed formation of proteoglycan aggregate structures in human articular cartilage disease states. Nature. 1980 Dec 11;288(5791):583–585. doi: 10.1038/288583a0. [DOI] [PubMed] [Google Scholar]
- Plaas A. H., Sandy J. D., Kimura J. H. Biosynthesis of cartilage proteoglycan and link protein by articular chondrocytes from immature and mature rabbits. J Biol Chem. 1988 Jun 5;263(16):7560–7566. [PubMed] [Google Scholar]
- Plaas A. H., Sandy J. D. The affinity of newly synthesized proteoglycan for hyaluronic acid can be enhanced by exposure to mild alkali. Biochem J. 1986 Feb 15;234(1):221–223. doi: 10.1042/bj2340221. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sandy J. D., Plaas A. H. Age-related changes in the kinetics of release of proteoglycans from normal rabbit cartilage explants. J Orthop Res. 1986;4(3):263–272. doi: 10.1002/jor.1100040302. [DOI] [PubMed] [Google Scholar]
- Tang L. H., Rosenberg L., Reiner A., Poole A. R. Proteoglycans from bovine nasal cartilage. Properties of a soluble form of link protein. J Biol Chem. 1979 Oct 25;254(20):10523–10531. [PubMed] [Google Scholar]