Zimmer D B, Landar A
Department of Pharmacology, University of South Alabama School of Medicine, Mobile 36688, USA.
J Neurochem. 1995 Jun;64(6):2727-36. doi: 10.1046/j.1471-4159.1995.64062727.x.
To better understand the mechanisms that regulate the function of the calcium-binding proteins S100A1 and S100B in developing systems, we have examined the level of, subcellular distribution of, and target proteins for these proteins in skeletal muscle (L6S4) and neuronal (PC12) cell lines. Both undifferentiated and differentiated L6 and PC12 cells express S100A1 and not S100B. Whereas S100A1 protein levels were higher in differentiated cells than in undifferentiated cells, steady-state mRNA levels did not change in differentiated L6 cells and decreased in differentiated PC12 cells when compared with undifferentiated cells. These results suggest that posttranscriptional rather than transcriptional mechanisms are responsible for increased S100A1 protein expression in myotubes and neurons. The colocalization of S100A1 staining with wheat germ agglutinin staining suggests that S100A1 is associated with the Golgi apparatus and secretory vesicles in PC12 and L6 cells. Using a gel overlay technique, S100A1-binding proteins were detected in undifferentiated and differentiated PC12 and L6 cells and the patterns observed were similar to those observed in brain and skeletal muscle, respectively. Although changes in the intensity of some binding proteins were detected, the overall pattern did not change when differentiated and undifferentiated cells were compared. These results suggest that the complement of S100A1-binding proteins does not change during differentiation, only the levels of some binding proteins. Altogether, our data demonstrate that the L6 and PC12 cell lines are excellent in vitro model systems for studying S100A1 expression and mechanisms that regulate S100A1 expression, subcellular distribution, and interaction with target proteins.
为了更好地理解在发育系统中调节钙结合蛋白S100A1和S100B功能的机制，我们检测了骨骼肌（L6S4）和神经元（PC12）细胞系中这些蛋白的水平、亚细胞分布及其靶蛋白。未分化和分化的L6和PC12细胞均表达S100A1而不表达S100B。与未分化细胞相比，S100A1蛋白水平在分化细胞中更高，而在分化的L6细胞中稳态mRNA水平没有变化，在分化的PC12细胞中与未分化细胞相比则下降。这些结果表明，转录后而非转录机制导致了肌管和神经元中S100A1蛋白表达的增加。S100A1染色与麦胚凝集素染色的共定位表明，S100A1与PC12和L6细胞中的高尔基体和分泌小泡相关。使用凝胶覆盖技术，在未分化和分化的PC12和L6细胞中检测到了S100A1结合蛋白，观察到的模式分别与在脑和骨骼肌中观察到的相似。尽管检测到一些结合蛋白强度的变化，但比较分化和未分化细胞时总体模式没有改变。这些结果表明，S100A1结合蛋白的组成在分化过程中没有变化，只是一些结合蛋白的水平发生了变化。总之，我们的数据表明，L6和PC12细胞系是研究S100A1表达以及调节S100A1表达、亚细胞分布及其与靶蛋白相互作用机制的优秀体外模型系统。
