Zimmer D B, Van Eldik L J
Department of Cell Biology, Howard Hughes Medical Institute, Vanderbilt University, Nashville, Tennessee 37232.
J Cell Biol. 1989 Jan;108(1):141-51. doi: 10.1083/jcb.108.1.141.
We have analyzed the levels, subcellular distribution, and target proteins of two calcium-modulated proteins, S100 and calmodulin, in differentiated and undifferentiated rat C6 glioma cells. Undifferentiated and differentiated C6 cells express primarily the S100 beta polypeptide, and the S100 beta levels are four-fold higher in differentiated compared to undifferentiated cells. Double fluorescent labeling studies of undifferentiated cells demonstrated that S100 beta staining localized to a small region of the perinuclear cytoplasm and colocalized with the microtubule organizing center and Golgi apparatus. Analysis of differentiated C6 cells demonstrated that S100 beta distribution and S100 beta-binding protein profile changed significantly upon differentiation. In addition, the brain-specific isozyme of one S100-binding protein, fructose-1,6-bisphosphate aldolase C, can be detected in differentiated but not undifferentiated C6 cells. While changes in the subcellular distribution of calmodulin were not observed during differentiation, calmodulin levels and calmodulin-binding protein profiles did change. Altogether these data suggest that S100 beta and calmodulin regulate different processes in glial cells and that the regulation of the expression, subcellular distribution, and target proteins of S100 beta and calmodulin during differentiation is a complex process which involves multiple mechanisms.
我们分析了两种钙调节蛋白S100和钙调蛋白在分化和未分化的大鼠C6胶质瘤细胞中的水平、亚细胞分布及靶蛋白。未分化和分化的C6细胞主要表达S100β多肽，与未分化细胞相比，分化细胞中的S100β水平高四倍。对未分化细胞的双荧光标记研究表明，S100β染色定位于核周细胞质的一个小区域，并与微管组织中心和高尔基体共定位。对分化的C6细胞的分析表明，分化后S100β分布和S100β结合蛋白谱发生了显著变化。此外，在分化的而非未分化的C6细胞中可检测到一种S100结合蛋白（果糖-1,6-二磷酸醛缩酶C）的脑特异性同工酶。虽然在分化过程中未观察到钙调蛋白亚细胞分布的变化，但钙调蛋白水平和钙调蛋白结合蛋白谱确实发生了变化。总之，这些数据表明，S100β和钙调蛋白在胶质细胞中调节不同的过程，并且在分化过程中S100β和钙调蛋白的表达、亚细胞分布及靶蛋白的调节是一个涉及多种机制的复杂过程。
