Intracellular responses by stimulation of receptors in neurons and related cells

大脑中的神经元和相关细胞接受不同的质膜受体的刺激，包括神经冲动、神经递质、神经肽、类胡萝卜素、激素、细胞因子和生长因子。细胞的反应包括多种类型，如第二信使的产生和酪氨酸激酶的激活。细胞内钙离子被确定为第二信使之一，其在细胞内的浓度受到严格的调控。本研究的目的是在质膜受体刺激的基础上，阐明细胞内Ca~(2+)和Gt~(2+)增加所引起的反应。我们利用原代培养的海马神经元、大脑星形胶质细胞和小脑颗粒细胞，建立了PC12细胞等细胞系。NG108-15细胞、C6胶质瘤细胞、成纤维细胞3YL细胞和脑片。为了通过钙信号通路阐明中枢神经系统的功能，我们检测了细胞系统中钙调素依赖的蛋白激酶II(CaM Kinase II)的激活动态。我们发现，CaM激酶II是通过细胞内钙升高来响应细胞外刺激而被激活的，并参与了中枢神经系统的细胞功能，如PC12细胞的神经元分化、星形胶质细胞的基因表达和海马钙区的长时程增强。它还参与了神经元和星形胶质细胞中丝裂原活化蛋白激酶的激活。此外，在酶激活的同时，还研究了内源底物的磷酸化。

Neurons and related cells in the brain receive diverse stimuli for receptors in the plasma membranes, which include nerve impulses, neurotransmitters, neuropeptides, autacoids, hormones, cytokines, and growth factors. Responses of the cells include various types such as the production of second messengers and activation of tyrosine kinases. The intracellular calcium ion (Ca^<2+>) is established to be one of second messengers and its concentration in the cells is strictly regulated. The purposes of the present study are to elucidate the intracellular responses elicited by the increase in Ca^<2+> on the basis of stimulation of receptors in the plasma membranes. We used primarily cultured neurons of the hippocampus, astrocytes from cerebrum and cultured granule cells from cerebellum, established cell lines such as PC12 cells. NG108-15 cells, C6 glioma cells, fibroblast 3Yl cells and brain slices. In an attempt to elucidate the functions of the central nervous system through Ca^<2+> signaling pathways, we examined the dynamic state of activation of Ca^<2+>/calmodulin-dependent protein kinase II (CaM kinase II) in the cell systems. We found that CaM kinase II is activated through elevation of intracellular Ca^<2+> in response to the extracellular stimuli and is involved in the cellular functions of the central nervous system, such as neuronal differentiation of PC12 cells, gene expression in astrocytes and long-term potentiation in the CAl area of the hippocampus. Ca^<2+> is also involved in the activation of mitogenactivated protein kinase in neurons and astrocytes. Furthermore, with concomitant activation of the enzyme, phosphorylation of endogenous substrates was studied.