Proteoglicanos da cartilagem epifisaria de rãs : composição, estrutura e variações regionais

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

A large proteoglycan was isolated fTom the articular, lateral and growth regions of the femoral distal cartilage of the bullfTog, Rana catesbeiana, and identified as aggrecan by a series of biochemical and immunochemical assays. The isolated monomer showed a polydisperse behavior on Sepharose CL2B, with a peak at Kav= 0,17. This proteoglycan was shown to contain the three globular domains G1 and G2 (spaced 21nm ftom each other) and G3, and to aggregate with hyaluronan and bovine link protein. The core protein was prepared after chondroitinase and keratanase digestion and visualized by Westem blotting with the aggrecan domain specific antibodies anti-ATEGQV (G1), anti-CDAGWL (Gl/G2) and Lec7 (reactive with the lectin-like domain ofG3). All three antibodies reacted with a predominant species that migrated with an apparent molecular size of 300kDa. The bullfTog aggrecan was substituted with both chondroitin and keratan sulfate chains. The condroitim sulfate chains showed a Kav of 0.42 after chromatography of all cartilages, but in the growth cartilage a population showed a Kav of 0.35. Aggrecan fTom articular and lateral cartilages contained concroitim sulfate chains that were composed of an average of 42 disaccharide units and 56 dissaccharide units in the growth cartilage. The ratio between the unsaturate disaccharides (Wi6S/Wi4S) was 0.4 for articular and lateral cartilage and 0.7 for the growth cartilage and contained a higher proportion ofunsulfated and 6-sulfated disaccharides. The condroitin sulfate chains contained mostly either GalNAc4S or GalNAc4,6S at non-reducing terminal in all three regions. Keratan sulfate was also detected on both the intact aggrecan and the isolated KS-rich region. For all three cartilage regions, the disaccharides of keratan sulfate were -80% Gal-GlcNAc6S and -20% Gal6S GlcNAc6S. These data demonstrate the evolutionary conservation of the aggrecan structure in a lower vertebrate andsuggest a high dependence of its functions on the domain organization

ASSUNTO(S)

anfibio cartilagem

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