Maeda N, Noda M
Division of Molecular Neurobiology, National Institute for Basic Biology, Graduate University for Advance Studies, Okazaki, Japan.
Development. 1996 Feb;122(2):647-58. doi: 10.1242/dev.122.2.647.
6B4 proteoglycan/phosphacan is one of the major phosphate-buffered saline-soluble chondroitin sulfate proteoglycans of the brain. Recently, this molecule has been demonstrated to be an extracellular variant of the proteoglycan-type protein tyrosine phosphatase, PTPzeta (RPTPbeta). The influence of the 6B4 proteoglycan, adsorbed onto the substratum, on cell adhesion and neurite outgrowth was studied using dissociated neurons from the cerebral cortex and thalamus. 6B4 proteoglycan adsorbed onto plastic tissue culture dishes did not support neuronal cell adhesion, but rather exerted repulsive effects on cortical and thalamic neurons. When neurons were densely seeded on patterned substrata consisting of a grid-like structure of alternating poly-L-lysine and 6B4 proteoglycan-coated poly-L-lysine domains, they were concentrated on the poly-L-lysine domains. However, 6B4 proteoglycan did not retard the differentiation of neurons but rather promoted neurite outgrowth and development of the dendrites of cortical neurons, when neurons were sparsely seeded on poly-L-lysine-conditioned coverslips continuously coated with 6B4 proteoglycan. This effect of 6B4 proteoglycan on the neurite extension of cortical neurons was apparent even on coverslips co-coated with fibronectin or tenascin. By contrast, the neurite extension of thalamic neurons was not modified by 6B4 proteoglycan. Chondroitinase ABC or keratanase digestion of 6B4 proteoglycan did not affect its neurite outgrowth promoting activity, but a polyclonal antibody against 6B4 proteoglycan completely suppressed this activity, suggesting that a protein moiety is responsible for the activity. 6B4 proteoglycan transiently promoted tyrosine phosphorylation of an 85x10(3) Mr protein in the cortical neurons, which correlated with the induction of neurite outgrowth. These results suggest that 6B4 proteoglycan/phosphacan modulates morphogenesis and differentiation of neurons dependent on its spatiotemporal distribution and the cell types in the brain.
6B4蛋白聚糖/磷酸聚糖是大脑中主要的磷酸盐缓冲盐水可溶性硫酸软骨素蛋白聚糖之一。最近，该分子已被证明是蛋白聚糖型蛋白酪氨酸磷酸酶PTPζ（RPTPβ）的细胞外变体。利用大脑皮层和丘脑的解离神经元，研究了吸附在基质上的6B4蛋白聚糖对细胞黏附和神经突生长的影响。吸附在塑料组织培养皿上的6B4蛋白聚糖不支持神经元细胞黏附，反而对皮层和丘脑神经元产生排斥作用。当神经元密集接种在由交替的聚L-赖氨酸和6B4蛋白聚糖包被的聚L-赖氨酸结构域组成的网格状结构的图案化基质上时，它们集中在聚L-赖氨酸结构域上。然而，当神经元稀疏接种在连续包被有6B4蛋白聚糖的聚L-赖氨酸预处理盖玻片上时，6B4蛋白聚糖并不阻碍神经元的分化，反而促进皮层神经元神经突的生长和树突的发育。即使在与纤连蛋白或腱生蛋白共包被的盖玻片上，6B4蛋白聚糖对皮层神经元神经突延伸的这种作用也很明显。相比之下，6B4蛋白聚糖对丘脑神经元的神经突延伸没有影响。6B4蛋白聚糖经软骨素酶ABC或角蛋白酶消化后，其促进神经突生长的活性不受影响，但针对6B4蛋白聚糖的多克隆抗体完全抑制了这种活性，这表明一种蛋白质部分负责该活性。6B4蛋白聚糖短暂促进皮层神经元中一种85×10³Mr蛋白的酪氨酸磷酸化，这与神经突生长的诱导相关。这些结果表明，6B4蛋白聚糖/磷酸聚糖根据其时空分布和大脑中的细胞类型调节神经元的形态发生和分化。
