LOCAL TRANSLATION IN ASTROCYTES

突触调节失调被认为是一系列神经疾病的基础，而星形胶质细胞 突触维持、形成和消除的关键介质。当共同刺激时，神经元形成更多的突触 与星形胶质细胞共同培养，单个星形胶质细胞在体内可包裹10万个突触。这一关键角色导致了 三方突触模型：突触不仅由突触前突触和突触后突触组成 密度，但也包括外周星形胶质突起(PAP)。就像树突和树突一样，PAP也有一个 特定的蛋白质组成，并根据局部活性在形态上进行重塑。 大量研究表明，突触重塑由神经元中的局部翻译调节， 尤其是在树枝状晶体中。特定的mRNA被穿梭到树突中，在那里它们的翻译可以被刺激 通过各种细胞外信号，允许微调调节局部蛋白质合成。新开 合成的蛋白质被认为介导了个体突触的加强，这是学习和 记忆，因为抑制翻译也会抑制记忆的形成。因为PAPs和树枝晶都被重塑 作为对活动的反应，这两种反应很可能对提高个体的整体效能是必不可少的 对经验作出反应的突触。因此，该领域的一个关键问题是，星形胶质细胞是否也能够像神经元一样 将特定的mRNA本地化到他们的翻译过程中？在这里，我们将使用生物化学来解决这个问题 检测PAP中特定mRNAs的浓缩和翻译的方法和功能分析。我们 将寻求：1)确定在加工过程中定位于星形胶质核糖体的转录本，2)确定 转录本本身的序列特征调节了它们在星形胶质细胞中的局部翻译，3)决定了 神经元活动的分子信号是否能够刺激星形胶质细胞的局部翻译。

Dysregulation of synapses is thought to underlie a range of neurological disorders, and astrocytes are key mediators of synaptic maintenance, formation and elimination. Neurons form more synapses when co- cultured with astrocytes, and a single astrocyte may ensheath 100,000 synapses in vivo. This critical role led to the “tripartite synapse” model: the synapse is not only comprised of the presynaptic bouton and postsynaptic density but also includes a peripheral astroglial process(PAP). Like dendrites and boutons, the PAP has a specific protein composition and is remodeled morphologically in response to local activity. Extensive work has demonstrated that synaptic remodeling is regulated by local translation in neurons, particularly in the dendrite. Specific mRNAs are shuttled into dendrites where their translation can be stimulated by a variety of extracellular signals, allowing for fine-tuned regulation of local protein synthesis. Newly synthesized proteins are thought to mediate the strengthening of individual synapses that underlies learning and memory, as inhibiting translation also inhibits formation of memory. As both PAPs and dendrites are remodeled in response to activity, it is likely that both responses are essential to increasing the overall efficacy of individual synapses in response to experience. Thus a key question in the field is are astrocytes, like neurons, also able to localize specific mRNAs to their processes for translation? Here, we will address this question using biochemical approaches and functional assays to test for the enrichment and translation of specific mRNAs in the PAP. We will seek to: 1) identify the transcripts localized to astroglial ribosomes in processes, 2) determine whether features in the sequence of the transcripts themselves mediate their local translation in astrocytes, 3) determine whether molecular cues of neuronal activity are capable of stimulating local translation in astrocytes.