Glycosylation site for chondroitin sulfate on the neural part-time proteoglycan, neuroglycan C
Glycosylation site for chondroitin sulfate on the neural part-time proteoglycan, neuroglycan C
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DOI：
10.1074/jbc.m403263200
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发表时间：
2004-11-05
影响因子：
4.8
通讯作者：
Oohira, A
中科院分区：
文献类型：
--
作者：
Aono, S;Tokita, Y;Oohira, A
神经聚糖C （NGC）是一种跨膜硫酸软骨素（CS）蛋白聚糖，主要在中枢神经系统（CNS）中表达。随着小脑的发育，NGC的结构发生了显著的变化，从蛋白聚糖到非蛋白聚糖，而在成熟的中枢神经系统的其他区域，有一小部分NGC分子以非蛋白聚糖的形式存在，这表明NGC的CS糖基化在整个中枢神经系统中受到发育调控。由于原代培养的大脑皮层神经元和星形胶质细胞分别以蛋白聚糖形式和非蛋白聚糖形式表达NGC， CS糖基化似乎受到不同细胞类型的不同调节。为了研究糖基化过程，表达NGC蛋白聚糖形式的细胞系将是良好的实验模型。将小鼠NGC cDNA转染到COS 1、PC12D和Neuro 2a细胞中，只有小鼠神经母细胞瘤细胞系Neuro 2a细胞表达含CS链的NGC。在PC12D细胞中，虽然检测到三种内在的CS蛋白聚糖，但外源表达的NGC不像成熟小脑中的NGC一样具有短的CS链。这表明CS链添加到NGC核心蛋白的调节方式不同于其他CS蛋白聚糖。作为利用Neuro 2a细胞研究CS糖基化机制的第一步，我们通过位点定向诱变确定了CS在NGC核心蛋白上的附着位点为Ser-123。至少在Neuro 2a细胞中，CS糖基化对于NGC在细胞内运输到细胞表面并不是必需的。
Neuroglycan C (NGC) is a membrane-spanning chondroitin sulfate (CS) proteoglycan that is expressed predominantly in the central nervous system (CNS). NGC dramatically changed its structure from a proteoglycan to a nonproteoglycan form with cerebellar development, whereas a small portion of NGC molecules existed in a nonproteoglycan form in the other areas of the mature CNS, suggesting that the CS glycosylation of NGC is developmentally regulated in the whole CNS. As primary cultured neurons and astrocytes from cerebral cortices expressed NGC in a proteoglycan form and in a nonproteoglycan form, respectively, CS glycosylation seems to be regulated differently depending on cell type. To investigate the glycosylation process, cell lines expressing a proteoglycan form of NGC would be favorable experimental models. When a mouse NGC cDNA was transfected into COS 1, PC12D, and Neuro 2a cells, only Neuro 2a cells, a mouse neuroblastoma cell line, expressed NGC bearing CS chains. In PC12D cells, although three intrinsic CS proteoglycans were detected, exogenously expressed NGC did not bear any short CS chains just like NGC in the mature cerebellum. This suggests that the addition of CS chains to the NGC core protein is regulated in a manner different from that of other CS proteoglycans. As the first step in investigating the CS glycosylation mechanism using Neuro 2a cells, we determined the CS attachment site as Ser-123 on the NGC core protein by site-directed mutagenesis. The CS glycosylation was not necessary for intracellular trafficking of NGC to the cell surface at least in Neuro 2a cells.