Iwata M, Carlson S S
Department of Physiology and Biophysics, University of Washington, Seattle 98195.
J Neurosci. 1993 Jan;13(1):195-207. doi: 10.1523/JNEUROSCI.13-01-00195.1993.
Extracellular matrix (ECM) is a secreted extracellular network. Few components of adult brain ECM are known. We have identified a new, large chondroitin sulfate proteoglycan (T1 antigen) that acts like a general ECM protein of brain. First, it is present throughout the brain; second, it has the properties of an extracellular protein; and third, it is extracted only under denaturing conditions. Immunocytochemical localization of the T1 antigen by light microscope shows it to be present throughout the rat brain in both white and gray matter. The T1 antigen outlines Purkinje and other large cells. No antigenicity is seen inside these cells. Biochemical evidence suggests that the T1 antigen is extracellular rather than cytosolic or intravesicular. The T1 antigen is disulfide-linked to two other proteins. Disulfide bonds are found only in extracellular or intravesicular proteins, not in intracellular cytosolic proteins. Moreover, the T1 antigen is probably not intravesicular. Unlike intravesicular proteins, only a small amount of T1 antigen is solubilized by nondenaturing detergents. While nondenaturing detergents extract but a small amount of T1 antigen from rat brain, the majority is solubilized by denaturing conditions (6 M guanidine-HCl). This behavior is similar to that of ECM components in other tissues and is unlike that of membrane proteins, even those linked to the cytoskeleton. We hypothesize that the insolubility of the T1 antigen in brain is due to its presence in an extracellular aggregate. The T1 antigen is a proteoglycan with a highly glycosylated protein core of 300 kDa. It does not appear to be related to the large, heavily glycosylated chondroitin sulfate proteoglycans aggrecan and versican, which were discovered in non-neural tissues. Antibodies to a 15 residue peptide present in both aggrecan and versican do not react with the T1 antigen.
细胞外基质（ECM）是一种分泌性的细胞外网络。目前已知的成体脑ECM成分很少。我们鉴定出一种新的、大型硫酸软骨素蛋白聚糖（T1抗原），它的作用类似于脑的一种普通ECM蛋白。首先，它遍布整个大脑；其次，它具有细胞外蛋白的特性；第三，它仅在变性条件下才能被提取出来。通过光学显微镜对T1抗原进行免疫细胞化学定位显示，它在大鼠脑的白质和灰质中均有分布。T1抗原勾勒出浦肯野细胞和其他大型细胞的轮廓。在这些细胞内部未观察到抗原性。生化证据表明，T1抗原位于细胞外，而非胞质或囊泡内。T1抗原通过二硫键与另外两种蛋白质相连。二硫键仅存在于细胞外或囊泡内的蛋白质中，而不存在于细胞内的胞质蛋白中。此外，T1抗原可能不在囊泡内。与囊泡内的蛋白质不同，非变性去污剂只能溶解少量的T1抗原。虽然非变性去污剂只能从大鼠脑中提取少量的T1抗原，但大多数在变性条件下（6M盐酸胍）可溶解。这种行为与其他组织中ECM成分的行为相似，与膜蛋白不同，即使是那些与细胞骨架相连的膜蛋白也不同。我们推测，脑内T1抗原的不溶性是由于它存在于细胞外聚集体中。T1抗原是一种蛋白聚糖，其蛋白核心高度糖基化，分子量为300 kDa。它似乎与在非神经组织中发现的大型、高度糖基化的硫酸软骨素蛋白聚糖聚集蛋白聚糖和多功能蛋白聚糖无关。针对聚集蛋白聚糖和多功能蛋白聚糖中都存在的一个15个氨基酸残基的肽段所产生的抗体，与T1抗原不发生反应。
