Endothelial cell-derived heparan sulfate binds basic fibroblast growth factor and protects it from proteolytic degradation.
Endothelial cell-derived heparan sulfate binds basic fibroblast growth factor and protects it from proteolytic degradation.
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DOI：
10.1083/jcb.107.2.743
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发表时间：
1988-08
期刊：
影响因子：
--
通讯作者：
Rifkin DB
中科院分区：
文献类型：
--
作者：
Saksela O;Moscatelli D;Sommer A;Rifkin DB
体外培养的牛毛细血管内皮细胞（BCE）可合成和分泌高分子量硫酸肝素蛋白聚糖和糖胺聚糖，并结合碱性成纤维细胞生长因子（bFGF）。用DEAE纤维素层析纯化分泌的硫酸肝素分子，然后用Sepharose 4B层析和固定化bFGF亲和层析纯化。大多数由BCE细胞分泌到培养基中的肝素酶敏感硫酸盐分子在低盐浓度下与固定化bFGF结合。然而，随着盐浓度的增加，从bFGF中洗脱时，所分泌的硫酸肝素分子对bFGF的亲和力有所不同，部分硫酸肝素需要在1.0 ~ 1.5 M的NaCl浓度之间洗脱。从BCE细胞中提取的细胞提取物还含有一种结合bfgf的硫酸肝素蛋白聚糖，该蛋白聚糖可以通过短时间的蛋白酶处理从完整细胞中释放出来。纯化的与bfgf结合的硫酸肝素与125I-bFGF竞争，与细胞上的低亲和力结合位点结合，而不与高亲和力位点结合。硫酸肝素不会干扰bFGF对BCE细胞纤溶酶原激活物活性的刺激，这与它对125I-bFGF与高亲和力位点结合的影响是一致的。可溶性bFGF容易被纤溶蛋白降解，而与硫酸肝素结合的bFGF则不受蛋白水解降解的影响。在加入纤溶酶之前，用肝素酶处理硫酸肝素，破坏了这种保护作用，导致添加的蛋白酶对bFGF的降解。结果表明，无论是由细胞直接释放，还是通过细胞外环境的蛋白水解降解释放，硫酸肝素都可能作为bFGF的载体，并通过与周围基质结构的结合竞争，促进本地产生的生长因子的扩散。同时，分泌的硫酸肝素糖胺聚糖保护生长因子免受细胞外蛋白酶的蛋白水解降解，细胞外蛋白酶在新生血管或细胞侵袭部位丰富。
Cultured bovine capillary endothelial (BCE) cells were found to synthesize and secrete high molecular mass heparan sulfate proteoglycans and glycosaminoglycans, which bound basic fibroblast growth factor (bFGF). The secreted heparan sulfate molecules were purified by DEAE cellulose chromatography, followed by Sepharose 4B chromatography and affinity chromatography on immobilized bFGF. Most of the heparinase-sensitive sulfated molecules secreted into the medium by BCE cells bound to immobilized bFGF at low salt concentrations. However, elution from bFGF with increasing salt concentrations demonstrated varying affinities for bFGF among the secreted heparan sulfate molecules, with part of the heparan sulfate requiring NaCl concentrations between 1.0 and 1.5 M for elution. Cell extracts prepared from BCE cells also contained a bFGF-binding heparan sulfate proteoglycan, which could be released from the intact cells by a short proteinase treatment. The purified bFGF-binding heparan sulfate competed with 125I-bFGF for binding to low-affinity binding sites but not to high-affinity sites on the cells. Heparan sulfate did not interfere with bFGF stimulation of plasminogen activator activity in BCE cells in agreement with its lack of effect on binding of 125I-bFGF to high-affinity sites. Soluble bFGF was readily degraded by plasmin, whereas bFGF bound to heparan sulfate was protected from proteolytic degradation. Treatment of the heparan sulfate with heparinase before addition of plasmin abolished the protection and resulted in degradation of bFGF by the added proteinase. The results suggest that heparan sulfate released either directly by cells or through proteolytic degradation of their extracellular milieu may act as carrier for bFGF and facilitate the diffusion of locally produced growth factor by competing with its binding to surrounding matrix structures. Simultaneously, the secreted heparan sulfate glycosaminoglycans protect the growth factor from proteolytic degradation by extracellular proteinases, which are abundant at sites of neovascularization or cell invasion.