Accumulation of alphaB-crystallin in glioma cells and the relation to oncogene expression.

我们已经确定罗森塔尔纤维的主要成分为α B-晶状体蛋白，一种主要的透镜蛋白。通常存在于脑中的α B-晶体蛋白的量很小，但它在各种病理条件下在反应性和肿瘤性胶质细胞和一些神经元中积累。因此，α B-晶状体蛋白的积累似乎是反应过程的一部分，并且是罗森塔尔纤维形成所需的。为了了解α B-晶体蛋白在星形胶质细胞内的罗森塔尔纤维中积累的意义，在热和氧化应激条件下检查了胶质瘤细胞系中α B-晶体蛋白的表达和代谢。α B-晶状体蛋白mRNA在两种应激后均增加，并且α B-晶状体蛋白蛋白从洗涤剂可溶的形式转变为洗涤剂不溶的形式。接下来，我们研究了通过遗传操作选择性地改变培养的神经胶质细胞中的α B-晶状体蛋白水平的表型效应。用大鼠α B-晶状体蛋白正义cDNA或反义cDNA转染大鼠C6神经胶质瘤细胞和人U-373 MG神经胶质瘤细胞以改变α B-晶状体蛋白的细胞水平。反义策略导致降低的alphaB-晶状体蛋白水平，如通过Western印迹和免疫细胞化学分析所揭示的。减少的α B-晶状体蛋白表达伴随着细胞表型的改变：（1）细胞大小和/或细长细胞形态的减少;（2）微丝网络的紊乱;和（3）细胞粘附性的降低。与HSP 27一样，额外的α B-晶状体蛋白的存在赋予稳定转染子耐热表型。因此，胶质瘤细胞中的α B-晶体蛋白在其耐热性中起作用，并可能有助于细胞骨架组织的稳定性。

We have identified a major component of Rosenthal fibers as alphaB-crystallin, a major lens protein. The amount of alphaB-crystallin normally present in the brain is small, but it accumulates in reactive and neoplastic glial cells and in some neurons in a variety of pathologic conditions. Thus, the accumulation of alphaB-crystallin appears to be a part of a reactive process and is required for the formation of Rosenthal fibers. To understand the significance of the accumulation of alphaB-crystallin in Rosenthal fibers within astrocytes, the expression and metabolism of alphaB-crystallin in glioma cell lines were examined under the condition of heat and oxidative stress. alphaB-crystallin mRNA was increased after both stresses and alphaB-crystallin protein moved from a detergent-soluble to a detergent-insoluble form. Next we investigated the phenotypic effects of selectively altering the levels of alphaB-crystallin in cultured glial cells by genetic manipulation. Rat C6 glioma cells and human U-373MG glioma cells were transfected with a rat alphaB-crystallin sense cDNA or an antisense cDNA to alter cellular levels of alphaB-crystallin. The anti-sense strategy resulted in decreased alphaB-crystallin levels, as revealed by Western blot and immunocytochemical analyzes. The reduced alphaB-crystallin expression was accompanied by alterations in cellular phenotype : (1)a reduction of cell size and/or a slender cell morphology ; (2)a disorganized microfilament network ; and (3)a reduction of cell adhensiveness. Like HSP27, the presence of additional alphaB-crystallin protein confers a thermoresistant phenotype to stable tranfectants. Thus, alphaB-crystallin in glioma cells plays a role in their thermal resistance and may contribute to the stability of cytoskeletal organization.