Novak J E, Agranoff B W, Fisher S K
Neuroscience Laboratory, Mental Health Research Institute, and Department of Pharmacology, University of Michigan, Ann Arbor, MI 48104-1687, USA.
J Neurochem. 2000 Jun;74(6):2322-30. doi: 10.1046/j.1471-4159.2000.0742322.x.
The CNS is enriched in phosphoinositide-specific phospholipase C (PLC) and in the G proteins linked to its activation. Although the regional distributions of these signaling components within the brain have been determined, neither their cell type-specific localizations (i.e., neuronal versus glial) nor the functional significance of their high expression has been definitively established. In this study, we have examined the expression of phosphoinositide signaling proteins in human NT2-N cells, a well characterized model system for CNS neurons. Retinoic acid-mediated differentiation of NT2 precursor cells to the neuronal phenotype resulted in five- to 15-fold increases in the expression of PLC-beta1, PLC-beta4, and Galpha(q/11) (the prime G protein activator of these isozymes). In contrast, the expression of PLC-beta3 and PLC-gamma1 was markedly reduced following neuronal differentiation. Similar alterations in cell morphology and in the expression of PLC-beta1, PLC-beta3, and Galpha(q/11) expression were observed when NT2 cells were differentiated with berberine, a compound structurally unrelated to retinoic acid. NT2-N neurons exhibited a significantly higher rate of phosphoinositide hydrolysis than NT2 precursor cells in response to direct activation of either G proteins or PLC. These results indicate that neuronal differentiation of NT2 cells is associated with dramatic changes in the expression of proteins of the phosphoinositide signaling system and that, accordingly, differentiated NT2-N neurons possess an increased ability to hydrolyze inositol lipids.
中枢神经系统富含磷酸肌醇特异性磷脂酶C（PLC）以及与其激活相关的G蛋白。尽管已经确定了这些信号成分在脑内的区域分布，但它们在细胞类型特异性定位（即神经元与神经胶质细胞）以及高表达的功能意义方面均未得到明确证实。在本研究中，我们检测了人NT2 - N细胞（一种用于中枢神经系统神经元的特征明确的模型系统）中磷酸肌醇信号蛋白的表达。视黄酸介导的NT2前体细胞向神经元表型的分化导致PLC - β1、PLC - β4和Gα(q/11)（这些同工酶的主要G蛋白激活剂）的表达增加了5至15倍。相反，神经元分化后PLC - β3和PLC - γ1的表达明显降低。当用与视黄酸结构无关的化合物黄连素诱导NT2细胞分化时，观察到细胞形态以及PLC - β1、PLC - β3和Gα(q/11)表达有类似变化。响应G蛋白或PLC的直接激活，NT2 - N神经元的磷酸肌醇水解速率显著高于NT2前体细胞。这些结果表明，NT2细胞的神经元分化与磷酸肌醇信号系统蛋白表达的显著变化相关，因此，分化后的NT2 - N神经元具有增强的水解肌醇脂质的能力。
