Sun X, Kaesberg P R, Choay J, Harenberg J, Ershler W B, Mosher D F
Department of Medicine, University of Wisconsin, Madison.
Semin Thromb Hemost. 1992;18(2):243-51. doi: 10.1055/s-2007-1002430.
Binding and degradation of TSP by CHO cells and adhesion of CHO cells to substrate-adsorbed TSP are mediated by cell surface PGs and inhibitable by heparin. In order to learn how these three processes are related, we studied the effects of defined heparin oligosaccharides up to 18-mer produced by nitrous acid digestion. There was a complex correlation among oligosaccharide chain length, affinity of oligosaccharide for TSP in a solid phase binding assay, and potencies of oligosaccharide in inhibition of the three cellular processes. Inhibition of degradation was more sensitive to shorter oligosaccharides than inhibition of binding. For instance, the 10-mer inhibited binding of TSP to cells by 10% and degradation by 70%. Punctate immunofluorescence of cell surface bound TSP was replaced by a diffuse pattern after incubation in the presence of the 10-mer. These results suggest that the clustering of TSP on the cell surface may trigger endocytosis and degradation. Inhibition of binding of TSP to cells, in turn, was more sensitive to midsized oligosaccharides than inhibition of cell adhesion to adsorbed TSP. Inhibition of adhesion correlated with the ability of oligosaccharides to block binding of 125I-heparin to adsorbed TSP.
CHO细胞对血小板反应蛋白（TSP）的结合与降解以及CHO细胞对底物吸附的TSP的黏附是由细胞表面的蛋白聚糖介导的，并可被肝素抑制。为了了解这三个过程之间的关系，我们研究了亚硝酸消化产生的长度达18聚体的特定肝素寡糖的作用。在固相结合试验中，寡糖链长度、寡糖对TSP的亲和力以及寡糖对这三个细胞过程的抑制效力之间存在复杂的相关性。降解的抑制比结合的抑制对较短的寡糖更敏感。例如，10聚体抑制TSP与细胞的结合达10%，抑制降解达70%。在10聚体存在下孵育后，细胞表面结合的TSP的点状免疫荧光被弥散模式所取代。这些结果表明，TSP在细胞表面的聚集可能触发内吞作用和降解。反过来，TSP与细胞结合的抑制对中等大小的寡糖比细胞对吸附的TSP的黏附抑制更敏感。黏附的抑制与寡糖阻断125I-肝素与吸附的TSP结合的能力相关。
