High affinity binding and overlapping localization of neurocan and phosphacan protein-tyrosine phosphatase-ζ/β with tenascin-R, amphoterin, and the heparin-binding growth-associated molecule
High affinity binding and overlapping localization of neurocan and phosphacan protein-tyrosine phosphatase-ζ/β with tenascin-R, amphoterin, and the heparin-binding growth-associated molecule
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DOI：
10.1074/jbc.273.12.6998
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发表时间：
1998-03-20
影响因子：
4.8
通讯作者：
Margolis, RU
中科院分区：
文献类型：
--
作者：
Milev, P;Chiba, A;Margolis, RU
我们研究了神经组织特异性硫酸软骨素蛋白多糖与细胞外基质蛋白tenascin-a和两种肝素结合蛋白，两性霉素和肝素结合生长相关分子(HB-GAM)的相互作用，用放射配基结合分析，这两种蛋白多糖都与tenascin-R显示出饱和的高亲和力结合，表观解离常数在2-7 nM范围内，结合是可逆的，在未标记的蛋白多糖的存在下被抑制，并且在蛋白多糖的软骨素酶处理后增加了类似60%的增加，表明这种相互作用是通过核心(糖蛋白)蛋白而不是由糖胺链介导的，这实际上可以部分地屏蔽结合部位，与其与tenascin-C的相互作用相反，在没有钙的情况下，结合减少了类似75%，磷酸聚糖与tenascin-R的结合不受结合缓冲液中缺乏二价阳离子的影响，尽管神经钙素的结合有很小但显著的下降，神经钙素和磷酸钙也是两性霉素和HB-GAM的高亲和力配体(K-d=0.3-8 nM)，这两种肝素结合蛋白在大脑中受到发育调节，并在功能上参与轴突生长，神经胶和磷酸多糖上的硫酸软骨素链至少占其与两性霉素和HB-GAM结合的80%。两性霉素的存在也使磷酸多糖与神经细胞黏附分子Contact的结合增加了5倍，免疫细胞化学研究显示蛋白多糖及其配体在胚胎和出生后的脑、视网膜和脊髓中重叠定位，因此这些研究揭示了神经聚糖和磷酸多糖与Tenascin细胞外基质蛋白家族的两个主要成员相互作用的差异，并表明硫酸软骨素蛋白多糖在中枢神经系统分化因子的结合和/或递送中发挥重要作用。
We have studied the interactions of the nervous tissue-specific chondroitin sulfate proteoglycans neurocan and phosphacan with the extracellular matrix protein tenascin-a and two heparin-binding proteins, amphoterin and the heparin-binding growth-associated molecule (HB-GAM), using a radioligand binding assay, Both proteoglycans show saturable, high affinity binding to tenascin-R with apparent dissociation constants in the 2-7 nM range, Binding is reversible, inhibited in the presence of unlabeled proteoglycan, and increased by similar to 60% following chondroitinase treatment of the proteoglycans, indicating that the interactions are mediated via the core (glyco)proteins rather than by the glycosaminoglycan chains, which may in fact partially shield the binding sites, In contrast to their interactions with tenascin-C, in which binding was decreased by similar to 75% in the absence of calcium, binding of phosphacan to tenascin-R was not affected by the absence of divalent cations in the binding buffer, although there was a small but significant decrease in the binding of neurocan, Neurocan and phosphacan are also high affinity ligands of amphoterin and HB-GAM (K-d = 0.3-8 nM), two heparin-binding proteins that are developmentally regulated in brain and functionally involved in neurite outgrowth, The chondroitin sulfate chains on neurocan and phosphacan account for at least 80% of their binding to amphoterin and HB-GAM. The presence of amphoterin also produces a 5-fold increase in phosphacan binding to the neural cell adhesion molecule contactin, Immunocytochemical studies showed an overlapping localization of the proteoglycans and their ligands in the embryonic and postnatal brain, retina, and spinal cord, These studies have therefore revealed differences in the interactions of neurocan and phosphacan with the two major members of the tenascin family of extracellular matrix proteins, and also suggest that chondroitin sulfate proteoglycans play an important role in the binding and/or presentation of differentiation factors in the developing central nervous system.