Molecular structure of heparan sulphate synthesised by bovine aortic endothelial cells

The distribution and structure of heparan sulphate (HS) synthesised by bovine aortic endothelial cells (BAEC) has been studied. Confluent cultures were harvested and analysed as three separate compartments: (a) the culture medium, (b) the detergent-soluble cell-associated material and (c) the detergent-insoluble matrix material extracted with 6 M urea. HS was present in all three of the culture compartments, but the molecular size of the HS proteoglycans (PG) and the free polysaccharide chains varied according to compartment origin. The matrix pool accounted for almost 50% of the total HS which was present as a large HSPG possessing polysaccharide chains of 79 kDa. When studied in more detail, these large HS chains displayed an N-sulphate content and distribution (determined by low pH nitrous acid treatment) similar to that seen in the majority of other mammalian heparan sulphates. Extended iduronate sequences were also identified (i.e., heparitinase-resistant sequences); however, apart from these regions, the degree of O-sulphation was relatively low. In addition, the presence of heparin-like sequences (GlcNSO3(+/- 6S)-IdoA(2S)), characterised by heparinase sensitivity, accounted for only 5% of the disaccharides and such sequences appeared to be located with an ordered distribution, mainly in relatively short sulphated domains within the intact molecule. Given the strategic location of the large matrix-associated HSPG within the BAEC system studied, it is conceivable that the HS structure may be important in a number of functions such as cell attachment processes and/or the binding of growth factors.