Modulation of synaptic transmission by a novel activity-dependent regulatory mechanism of astrocytic gap junction coupling

已知星形胶质细胞之间的间隙连接偶联受神经元活性调节。间隙连接耦合的这种改变将通过不同的过程来改变突触的操作，例如空间缓冲的调节、递质摄取和调节因子的释放。最近，我们能够表明，dreplastin与连接蛋白43（Cx43）的相互作用稳定星形胶质细胞中的间隙连接耦合。如在神经元中所证明的，dreplastin也可能作为星形胶质细胞中的信号转导机制，其向膜下细胞骨架的其他组分以及Cx43发出信号。这可能是负责调节细胞-细胞偶联。然而，drebrin介导的星形胶质细胞Cx43功能和缝隙连接偶联的变化如何调节突触活动仍有待研究。该项目旨在分析突触传递活动依赖性调节的功能意义。在新的DFG计划中，我们将致力于证明以下假设。(1)神经元活性通过修改Drebrin-Cx43相互作用来调节相邻星形胶质细胞的偶联。(2)这种Drebrin-Cx43相互作用为感知和调节突触传递提供了一种新的活性依赖性机制。为了回答这些问题，我们将使用不同的实验模型系统，包括细胞培养，其中转染针对dreplatin的siRNA允许星形胶质细胞中的细胞-细胞通信的特异性下调和突触活性的平行电生理学分析。此外，这种新的相互作用将在急性脑切片中进行分析，其中我们将siRNA注射到Tgn（GFAP-EGFP）小鼠的已鉴定星形胶质细胞群中。这将使我们能够研究Drebrin-Cx43介导的功能环境中突触传递的调节。

It is known that gap junction coupling between astrocytes is regulated by neuronal activity. Such modification of gap junction coupling will modify the operation of synapses by different processes, such as modulation of spatial buffering, transmitter up-take, and release of modulatory factors. Recently, we were able to show that the interaction of drebrin with connexin 43 (Cx43) stabilizes gap junction coupling in astrocytes. As demonstrated in neurons, drebrin might also serve as a signal transduction mechanism in astrocytes, which signals to other components of the sub-membrane cytoskeleton as well as to Cx43. This might be responsible for regulation of cell-cell coupling. It remains to be investigated, however, how drebrin-mediated changes of Cx43-function and gap junction coupling in astrocytes modulate on-going synaptic activity. The proposed project is aiming to analyze the functional significance of the activity-dependent regulation of synaptic transmission. In the new DFG program we will aim to prove the following hypothesis. (1) Neuronal activity modulates coupling of adjacent astrocytes by modifying Drebrin-Cx43 interaction. (2) This Drebrin-Cx43 interaction provides a novel activitydependent mechanism for sensing and adjusting synaptic transmission. To answer these questions, we will use different experimental model systems, including cell culture, in which transfection of siRNA against drebrin allows specific down-regulation of cellcell communication in astrocytes and parallel electrophysiological analysis of synaptic activity. Additionally, this novel interaction will be analyzed in acute brain slices, in which we will inject siRNA into a population of identified astrocytes from Tgn(GFAP-EGFP) mice. This will allow us to investigate the Drebrin-Cx43 mediated modulation of synaptic transmission in a functional environment.