Establishment of cell models on transfection of functional protein and the study on brain signal transduction

本研究旨在建立表达受体、酶、离子通道等重要功能蛋白的细胞系模型。用神经递质激素、生长因子等刺激已建立的细胞激活细胞中表达的蛋白质。本研究的重点是对细胞内钙离子（Ca^2+）的分析以及钙调素激酶I、II、III、IV和激酶的功能意义的研究。在NG 108 -15细胞中表达CaM激酶II的胞浆和核亚型，其中检测脑源性神经营养因子（BDNF）的表达。BDNF的表达不被胞质异构体如CaM激酶II δ1和δ2的转染所增加，但被CaM激酶II δ3和αB所增加。RT-PCR定量检测结果显示，在体外培养条件下，第四外显子BDNF mRNA表达量增加，而第三外显子BDNF mRNA表达量无明显变化。多巴胺D_2受体（D_2R）由长链受体（D_2RL）和短链受体（D_2RS）组成。将两种cDNA转染NG 108 -15细胞，获得稳定表达两种受体的细胞。通过共聚焦激光显微镜的分析揭示了每个受体在细胞中的不同定位。刺激D2 R可增加细胞内Ca^<2+>浓度。将具有核定位信号的CaM激酶II δ3的cDNA瞬时转染D2 RL稳定细胞。用激动剂刺激转染细胞的D2 R导致CaM激酶II的核亚型的激活和BDNF表达的增加。

The present study intends to establish the model of the cell line in which functionally important proteins such as receptors, enzymes, ion channels are expressed. Stimulation of the established cells with neurotransmitters hormones, growth factors etc. activates the expressed proteins in the cells. These models serve as the established systems to analyze effects of drugs and to create new drugs.The study focuses the analysis on the intracellular calcium (Ca^<2+>) and on the functional significance of CaM kinases I, II, III, IV and kinase. The cytosolic and nuclear isoforms of CaM kinase II were expressed in NG108-15 cells in which the expression of brain-derived neurotrophic factor (BDNF) was examined. The expression of BDNF was not increased by the transfection of the cytosolic isoforms such as CaM kinase II δ1, and δ2 but was increased by CaM kinase II δ3 and αB. The quantitative method of RT-PCR for the amount of the mRNA indicated the increase in Exon IV-BDNF mRNA but not Exon III-BDNF mRNA. This suggest that the nuclear isoforms only increase the mRNA and proteins of BDNF.Dopamine D2 receptors (D2R) consist of the long chain receptor (D2RL) and the short chain receptor (D2RS). Both cDNAs were transfected into NG108-15 cells and the stable cells with the expression of each receptor were obtained. The analysis by confocal laser microscopy revealed different localization of each receptor in the cells. Stimulation of D2R increased the concentration of the intracellular Ca^<2+>. The cDNA of CaM kinase II δ3 with nuclear localization signal was transiently transfected in the stable cells of D2RL. Stimulation of D2R of the transfected cells with the agonist resulted in activation of the nuclear isoform of CaM kinase II and the increase in the expression of BDNF.