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一个主要成分是α-晶体蛋白，这是一种主要的晶状体蛋白。正常情况下，α-晶体蛋白在大脑中的数量很少，但在各种病理条件下，它在反应性和肿瘤性胶质细胞以及一些神经元中积聚。因此，α-晶状体蛋白的积累似乎是反应过程的一部分，是形成罗森塔尔纤维所必需的。为了解α-晶状体蛋白在星形胶质细胞Rosenthal纤维中积聚的意义，我们观察了在高温和氧化应激条件下，α-晶状体蛋白在胶质瘤细胞系中的表达和代谢。在两次胁迫后，α-晶状体蛋白的mRNA都增加了，并且α-晶状体蛋白从洗涤剂可溶的形式转变为洗涤剂不能溶解的形式。接下来，我们研究了通过基因操作选择性地改变培养的神经胶质细胞中α-晶体蛋白水平的表型效应。以大鼠C6神经胶质瘤细胞和人U-373 MG神经胶质瘤细胞为研究对象，分别导入大鼠α-晶体蛋白正义和反义基因，改变细胞内α-晶体蛋白的表达水平。Western印迹和免疫细胞化学分析显示，反义策略导致α-晶体蛋白水平下降。α-晶状体蛋白表达的降低伴随着细胞表型的改变：(1)细胞尺寸缩小和/或细胞形态细长；(2)微丝网络紊乱；(3)细胞粘附性降低。像HSP27一样，额外的α-晶体蛋白的存在使稳定的转化子具有耐热表型。因此，胶质瘤细胞中的α-晶状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。

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.