Interactions of the chondroitin sulfate proteoglycan phosphacan, the extracellular domain of a receptor-type protein tyrosine phosphatase, with neurons, glia, and neural cell adhesion molecules.
Interactions of the chondroitin sulfate proteoglycan phosphacan, the extracellular domain of a receptor-type protein tyrosine phosphatase, with neurons, glia, and neural cell adhesion molecules.
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DOI：
10.1083/jcb.127.6.1703
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发表时间：
1994-12
期刊：
影响因子：
--
通讯作者：
Margolis RU
中科院分区：
文献类型：
--
作者：
Milev P;Friedlander DR;Sakurai T;Karthikeyan L;Flad M;Margolis RK;Grumet M;Margolis RU
Phosphacan 是一种由中枢神经系统神经胶质细胞产生的硫酸软骨素蛋白聚糖，代表受体型蛋白酪氨酸磷酸酶 (RPTP zeta/beta) 的胞外结构域。我们之前证明可溶性磷酸聚糖抑制了 N-CAM 或 Ng-CAM 包被的微珠的聚集，现在发现可溶性 125I-磷酸聚糖可逆地与这些神经细胞粘附分子结合，但不与许多其他细胞表面和细胞外基质蛋白结合。结合是可饱和的，Scatchard 图显示单个高亲和力结合位点，Kd 约为 0.1 nM。软骨素酶处理后结合减少约15%，游离硫酸软骨素仅具有中等抑制作用，表明磷酸聚糖核心糖蛋白占大部分结合活性。胚胎大鼠脊髓磷酸聚糖、Ng-CAM 和 N-CAM 的免疫细胞化学研究具有重叠的分布。当分离的神经元在涂有磷酸聚糖和 Ng-CAM 组合的培养皿上孵育时，神经元粘附和神经突生长受到抑制。 125I-磷酸聚糖与神经元结合，并且这种结合被针对 Ng-CAM 和 N-CAM 的抗体抑制，表明这些 CAM 是神经元上磷酸聚糖的主要受体。表达磷酸聚糖的 C6 神经胶质瘤细胞粘附在涂有 Ng-CAM 的培养皿上，低浓度的磷酸聚糖抑制对 Ng-CAM 的粘附，但不抑制对层粘连蛋白和纤连蛋白的粘附。我们的研究表明，通过与神经细胞粘附分子结合，也可能通过竞争跨膜磷酸酶的配体，磷酸聚糖可能在中枢神经系统发育过程中调节神经元和神经胶质粘附、神经突生长和信号转导中发挥重要作用。
Phosphacan is a chondroitin sulfate proteoglycan produced by glial cells in the central nervous system, and represents the extracellular domain of a receptor-type protein tyrosine phosphatase (RPTP zeta/beta). We previously demonstrated that soluble phosphacan inhibited the aggregation of microbeads coated with N-CAM or Ng-CAM, and have now found that soluble 125I-phosphacan bound reversibly to these neural cell adhesion molecules, but not to a number of other cell surface and extracellular matrix proteins. The binding was saturable, and Scatchard plots indicated a single high affinity binding site with a Kd of approximately 0.1 nM. Binding was reduced by approximately 15% after chondroitinase treatment, and free chondroitin sulfate was only moderately inhibitory, indicating that the phosphacan core glycoprotein accounts for most of the binding activity. Immunocytochemical studies of embryonic rat spinal phosphacan, Ng-CAM, and N-CAM have overlapping distributions. When dissociated neurons were incubated on dishes coated with combinations of phosphacan and Ng-CAM, neuronal adhesion and neurite growth were inhibited. 125I-phosphacan bound to neurons, and the binding was inhibited by antibodies against Ng-CAM and N-CAM, suggesting that these CAMs are major receptors for phosphacan on neurons. C6 glioma cells, which express phosphacan, adhered to dishes coated with Ng-CAM, and low concentrations of phosphacan inhibited adhesion to Ng-CAM but not to laminin and fibronectin. Our studies suggest that by binding to neural cell adhesion molecules, and possibly also by competing for ligands of the transmembrane phosphatase, phosphacan may play a major role in modulating neuronal and glial adhesion, neurite growth, and signal transduction during the development of the central nervous system.