Glycation induced crosslinking of link proteins, in vivo and in vitro.
OBJECTIVE
Reducing sugars have the ability to crosslink proteins through creation of advanced glycosylated end products (AGE). In this study, we determined the ability of AGE to induce crosslinking of link proteins and aggrecan proteoglycans.


METHODS
Aggrecan proteoglycans and link proteins were purified from adult human articular cartilage and from young bovine nasal cartilage for in vivo and in vitro studies, respectively. In vitro studies concerned incubation of aggrecan aggregates or link proteins with ribose under physiological conditions. After 30 days, aggregates were centrifuged dissociatively to obtain aggrecan monomers and link proteins. Aggrecan monomers were analyzed by immunoblot assay. Incubated link proteins were analyzed by SDS-PAGE and Sephacryl-200 column chromatography.


RESULTS
After extensive purification, adult human cartilage aggrecan continued to show the presence of link protein antigens by immunoblot analysis. Immunoblot analysis of purified aggrecan derived from ribose-treated aggregates also showed the presence of link protein antigens. Ribose treatment of link protein lead to polymerization that was confirmed by Sephacryl-200.


CONCLUSIONS
These studies suggest that human link proteins tend to become crosslinked to aggrecan in adult cartilage. A likely cause of the crosslinking is formation of AGE due to reducing sugars.
Pokharna
H K
HK
Section of Orthopeadic Surgery, University of Chicago Medical Center, Chicago, Illinois 60637, USA. hpokharn@surgery.bsd.uchicago.edu
Pottenger
L A
LA
D053674:Aggrecans; D000818:Animals; D002417:Cattle; D016326:Extracellular Matrix Proteins; D017127:Glycation End Products, Advanced / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D037181:Lectins, C-Type; D011506:Proteins / Q000737:chemistry*; D011509:Proteoglycans / Q000032:analysis / Q000737:chemistry; D012266:Ribose / Q000378:metabolism; D000099249:Proteoglycan Link Protein
D053674:Aggrecans; D016326:Extracellular Matrix Proteins; D017127:Glycation End Products, Advanced; D037181:Lectins, C-Type; D011506:Proteins; D011509:Proteoglycans; D012266:Ribose; D000099249:Proteoglycan Link Protein