参与突触与认知功能的非钙二价阳离子通道的深入研究

Studies have been focusing on investigating the role of different calcium channels in synaptic and cognitive functions. Little attention, if any, has been paid to examining a potential role of other di-cation channels in such functions. Magnesium ion is the fourth most abundant cation in nature and human body. It is known to be essential for the function of more than 360 enzymes. Our previous work demonstrates that elevating brain magnesium enhances synaptic plasticity/density and different forms of learning and memory in rodents suggesting that magnesium ion plays critical role in synaptic and cognitive functions. .These intriguing data raise the following fundamental question regarding channels/transporters involved in magnesium homeostasis; that is whether or not they play essential role in maintaining normal synaptic and cognitive functions; besides calcium ion channels..The current project will explore the potential role of magnesium channels in maintaining normal synaptic plasticity/density and learning & memory abilities at the molecular, cellular and behavioral levels. To identify the key channels, we will screen for the channels that are responsive to changes in extracellular magnesium concentration and/or in neuronal activity. Following the identification of the key channels, we will study the effect of knocking down these channels on the structural and functional synapse density in hippocampal neurons. To study the ion channels’ role in cognitive functions, we will knock down the identified key channels in the hippocampus of rats and generate conditional knock out mice to monitor the learning & memory abilities using different behavioral assays. Finally, to provide molecular insights, we will conduct rescue experiments in hippocampal neurons derived from the knock out mice..The project is expected to show for the first time that ion channels/transporters, known to be involved in magnesium homeostasis, are essential for having normal synaptic density and cognitive abilities. The results of this project are expected to advance, or even revolutionize, our basic understanding of molecular mechanisms involved in synaptic and cognitive functions. Furthermore, the identified channels will represent new molecular targets for future drug design, which will generate novel drugs for treating mental diseases/disorders associated with cognitive impairment such as PTSD, phobias, depression and Alzheimer’s disease.

有关突触/认知的研究，大多与Ca2+相关，鲜有其他离子的报道。我们前期工作证明提高脑镁能增强突触可塑性/密度，能特异增强大小鼠不同形式的学习/记忆，这提示Mg2+内稳态至关重要：与Ca2+通道一样，其对维持正常的突触/认知功能起到关键作用。那么Mg2+通道是否参与了突触功能/认知过程？.本课题将在分子、细胞和行为水平上探索Mg2+通道在突触功能/认知功能的作用：通过分子，细胞手段确定关键的Mg2+通道，在大小鼠原代离体海马神经元细胞培养上研究干扰关键Mg2+通道对突触可塑性/密度的影响，通过下调/敲除活体大小鼠海马区关键的Mg2+通道基因表达来观察其对大/小鼠认知行为的影响。最后我们还将通过分子，细胞手段来试图恢复该转小鼠因为关键的Mg2+通道基因被敲除而引起的认知障碍。.本课题首次揭示Mg2+通道在突触/认知功能的作用。将增进/彻底改变我们对突触/认知分子机制的理解。将为治疗认知功能障。

有关突触/认知的研究，大多与Ca2+相关，鲜有其他离子的报道。我们前期工作证明提高脑镁能增强突触可塑性/密度，能特异增强大小鼠不同形式的学习/记忆，这提示Mg2+内稳态至关重要：与Ca2+通道一样，其对维持正常的突触/认知功能起到关键作用。那么Mg2+通道是否参与了突触功能/认知过程？本课题在分子、细胞和行为水平上研究了Mg2+通道在突触功能/认知功能的作用：通过分子，细胞手段确定关键的Mg2+通道，在大小鼠原代离体海马神经元细胞培养上研究干扰关键Mg2+通道对突触可塑性/密度的影响，通过下调/敲除活体大小鼠海马区关键的Mg2+通道基因表达来观察其对大/小鼠认知行为的影响。最后我们还通过分子，细胞手段来试图恢复该转小鼠因为关键的Mg2+通道（TRPM7）基因被敲除而引起的认知障碍。此外，已确定的镁离子通道TRPM7有助于不同组织中的多个生物和病理过程。然而，它在生理条件下的中枢神经系统中的作用仍然不清楚。我们的研究表明，在海马神经元敲低TRPM7有效降低结构突触密度。其中突触密度是由C端的β-激酶域来挽救，而不是通过TRPM7的电导道区域或通过增加Mg2+或Zn2+的细胞外浓度来挽救的。小鼠早期条件敲除TRPM7会损害其学习和记忆，降低其突触密度和可塑性。成年大鼠海马中的TRPM7击倒也会损害其学习和记忆，降低其突触密度和突触可塑性。在敲除小鼠中，恢复大脑中β-激酶域的表达可以挽救其突触密度/可塑性和学习记忆能力，而这些变化可能是通过和磷酸化cofilin的相互作用来实现的。这些结果表明，大脑TRPM7对于生理和非病理条件下维持正常突触密度和认知的功能非常重要。