Project: Synaptotagmin IV Regulates The Tripartite Synapse

钙结合的突触素家族囊泡蛋白控制囊泡与质膜的融合。研究最深入的家族成员--突触素I，是突触前终末快速、同步释放神经递质所必需的。虽然突触素I的作用正在被阐明，但该小组另外14个成员的作用还不太清楚。然而，我们的初步研究支持这样的观点，即星形胶质细胞，而不是海马体锥体神经元，表达突触素IV。鉴于突触素IV基因敲除的小鼠在基于海马体的学习和记忆中表现出缺陷，项目3的目标是检验这一假说，即突触素IV对于钙触发的星形胶质细胞谷氨酸的胞吐释放以及这种受调控的递质释放是必不可少的 通路是控制突触传递的关键途径。在第一个目标中，我们将检验星形细胞突触素IV调节胶质递质释放和原位突触调制的假设(Haydon，Ellis-Davies和Coulter)。众所周知，突触活动的序列会导致突触的长期修改。我们假设，这种活动同样会导致三方突触的星形细胞臂的长期变化。在第二个目标中，我们将与项目2合作，询问是否 突触活动调节原位星形胶质细胞(Haydon，Ellis-Davies和Eberwin)内胶质递质释放机制的合成。本实验中研究的分子将取决于项目2的初步结果，其中位于星形胶质细胞内的mRNAs和那些特定于胶质细胞突起的mRNAs将被识别。然而，我们将研究的候选药物之一是synaptopagmin IV。为了实现这一目标，我们将在最近开发的 能够使用电穿孔将信使核糖核酸导入急性分离的海马片中的星形胶质细胞。这一目标在独立项目中是不可行的，需要密切互动，因为项目3的结果将决定在此采取的方向。通过阐明星形胶质细胞对突触传递的控制功能，这个协作性的Conte Center项目具有 有可能改变我们对突触的短期和长期调控的看法。

The calcium-binding synaptotagmin family of vesicle proteins control vesicle fusion with the plasma membrane. The best studied family member, synaptotagmin I, is necessary for fast, synchronized neurotransmitter release from presynaptic terminals. While the roles of synaptotagmin I are being elucidated, the roles of the additional 14 members of the group are less clear. However, our preliminary studies support the notion that astrocytes, but not hippocampal pyramidal neurons, express synaptotagmin IV. Given that synaptotagmin IV knockout mice have demonstrated deficits in hippocampal-based learning and memory, the goal of project 3 is to test the hypothesis that synaptotagmin IV is essential for calcium-triggered exocytotic release of glutamate from astrocytes and that this regulated transmitter release pathway is critical for the control of synaptic transmission at the tripartite synapse. In the first aim we will test the hypothesis that astrocytic synaptotagrnin IV regulates glial transmitter release and the modulation of synapses in situ (Haydon, Ellis-Davies and Coulter). It is well established that trains of synaptic activity lead to long-term modifications of the synapse. We hypothesize that such activity similarly causes a long-term change in the astrocytic arm of the tripartite synapse. In collaboration with project 2, we will, in the second aim, ask whether synaptic activity regulates the synthesis of gliotransmitter release machinery within astrocytes in situ (Haydon, Ellis-Davies and Eberwine). The molecules studied in this experiment will be dependent on the initial results from project 2 where mRNAs resident within astrocytes and those specifically within glial processes will be identified. However, one candidate that we will study is synaptotagmin IV. To achieve this objective we will build on our recently developed ability to use electroporation to introduce mRNA into astrocytes in acutely isolated hippocampal slices. This aim is not feasible in a stand-alone project and will require close interactions as the outcomes of project 3 will dictate the directions taken here. By elucidating control functions of astrocytes over synaptic transmission this collaborative Conte Center project has the potential to change the way we view both short- and long-term regulation of the synapse.