Lark M W, Culp L A
J Biol Chem. 1984 Jan 10;259(1):212-7.
Substratum adhesion sites from murine Balb/c SVT2 fibroblasts are enriched in heparan sulfate proteoglycans which have been implicated in mediating adhesion of these cells to a fibronectin-adsorbed tissue culture substratum. Most of the heparan sulfate isolated from newly formed adhesion sites is found covalently attached to protein as proteoglycan while a significant portion of heparan sulfate from older sites has been identified as a single-chain species. This observation suggests that there may be catabolism of the heparan sulfate proteoglycan during the "maturation" of these adhesion sites at the cell's undersurface. Zwittergent 3-12 selectively extracts the single-chain class of heparan sulfate from either newly formed or "mature" adhesion sites while leaving the proteoglycan firmly bound in these sites. In an effort to further characterize the metabolism of these proteoglycans, substratum adhesion sites were isolated at various times after the cells had been pulse-radiolabeled using radioactive sulfate and subsequently chased. Greater than 80% of the sulfate-radiolabeled material is lost from the substratum-attached material within 24-48 h. Characterization of both the Zwittergent-soluble and -resistant heparan sulfate indicated that there was an initial accumulation followed by a rapid loss of a portion of the radiolabeled heparan sulfate as the single-chain Zwittergent-soluble class. However, most of the heparan sulfate proteoglycan was lost from the adhesion sites following approximately a 4-h time lag during the chase period without going through a smaller molecular weight intermediate. The turnover properties of the heparan sulfate proteoglycan in the EGTA-detachable cells were different from those in the substratum-attached fraction of the cell. The significance of these two different mechanisms of turnover of heparan sulfate proteoglycan in adhesion sites is discussed in relation to the role of this proteoglycan in mediating adhesion processes.
来自小鼠Balb/c SVT2成纤维细胞的基质黏附位点富含硫酸乙酰肝素蛋白聚糖，这些蛋白聚糖被认为介导了这些细胞与纤连蛋白吸附的组织培养基质的黏附。从新形成的黏附位点分离出的大部分硫酸乙酰肝素共价连接在蛋白上形成蛋白聚糖，而来自较老位点的相当一部分硫酸乙酰肝素已被鉴定为单链形式。这一观察结果表明，在细胞下表面这些黏附位点的“成熟”过程中，硫酸乙酰肝素蛋白聚糖可能存在分解代谢。两性离子去污剂3-12能选择性地从新形成的或“成熟”的黏附位点提取单链类硫酸乙酰肝素，同时使蛋白聚糖牢固地结合在这些位点。为了进一步表征这些蛋白聚糖的代谢，在细胞用放射性硫酸盐进行脉冲放射性标记并随后进行追踪后的不同时间分离基质黏附位点。超过80%的硫酸放射性标记物质在24-48小时内从附着在基质上的物质中丢失。对两性离子去污剂可溶和不可溶的硫酸乙酰肝素的表征表明，随着单链两性离子去污剂可溶类放射性标记硫酸乙酰肝素的一部分，最初有积累，随后迅速丢失。然而，在追踪期大约4小时的时间滞后后，大部分硫酸乙酰肝素蛋白聚糖从黏附位点丢失，而没有经过较小分子量的中间体。硫酸乙酰肝素蛋白聚糖在EGTA可分离细胞中的周转特性与细胞附着在基质部分中的不同。本文讨论了硫酸乙酰肝素蛋白聚糖在黏附位点的这两种不同周转机制的意义，以及该蛋白聚糖在介导黏附过程中的作用。
