Regulation of parallel recycling pathways at synaptic sites

项目总结/摘要 磷脂酰肌醇信号脂质是内膜运输的关键调节因子，对突触传递至关重要。 功能和可塑性。值得注意的是，许多突触特异性运输途径与同源的 非神经元细胞的信号通路。突触的专门运输主要是通过适度的 改变通用贩运途径。由于突触上的高流量需求， 在这些途径中，特别是影响神经系统，并构成广泛的神经系统疾病的基础。 PIKfyve及其调节蛋白Vac 14和Fig 4控制低丰度的细胞水平， 信号脂质磷脂酰肌醇（3，5）-二磷酸（PI 3，5 P2）和磷脂酰肌醇5-磷酸 （PI5P）。我们和其他人的研究表明，这一途径中的微小突变与几种 神经系统疾病对PI（3，5）P2在神经元中的作用的深入了解来自我们发现PIKfyve在神经元中起作用， 在突触功能和可塑性中起重要作用，并部分通过控制AMPA的表面水平发挥作用， 型谷氨酸受体（AMPAR）。PIKfyve下调导致循环和表面水平增强 的AMPAR，虽然潜在的分子机制是未知的。巧合的是，我们在 在非神经元细胞中，揭示了PIKfyve在SNX 17再循环途径的控制中具有直接的积极作用。 值得注意的是，SNX 17和SNX 27途径都来自核内体上的相同微结构域。这 将PIKfyve置于主动再循环SNX 17依赖性和SNX 27依赖性货物的内体上。 重要的是，AMPAR表面水平部分通过SNX 27依赖性再循环来控制。本提案的目标1 试图确定PIKfyve是否通过SNX 27的负调节来控制AMPAR表面水平， 依赖回收。 重要的是，我们的新研究提出了在PIKfyve抑制期间SNX 17失调的可能性， 也可能导致观察到的突触缺陷。与SNX 17一起发挥功能的蛋白质突变导致了 一些神经系统疾病，但令人惊讶的是，没有发表的研究来确定SNX 17是否 再循环对于突触功能至关重要。目前的项目将测试假设，PIKfyve差异 调节来自相同内体的不同再循环途径。为了解决这个假设，我们 将1）确定PIKfyve调节AMPAR再循环的机制; 2）确定SNX 17的作用- 神经元和非神经元细胞中的Retriever通路是否相似，PIKfyve是这一通路的调节因子。

PROJECT SUMMARY/ABSTRACT Phosphoinositide signaling lipids are key regulators of endomembrane trafficking and are critical for synaptic function and plasticity. Notably, many synapse-specific trafficking pathways are highly similar to cognate pathways in non-neuronal cells. The specialized trafficking at synapses is largely achieved via modest alterations to generic trafficking pathways. Due to the high demand of traffic at synapses, very minor mutations in these pathways specifically impact the nervous system and underlie a wide range of neurological disorders. PIKfyve and its regulatory proteins Vac14 and Fig4 control the cellular levels of the low abundance signaling lipids phosphatidylinositol (3,5)-bis phosphate (PI3,5P2) and phosphatidylinositol 5- phosphate (PI5P). Studies from us and others revealed that minor mutations in this pathway are associated with several neurological disorders. Insights into roles of PI(3,5)P2 in neurons came from our discovery that PIKfyve plays essential roles in synaptic function and plasticity, and acts in part via controlling the surface levels of AMPA- type glutamate receptors (AMPARs). PIKfyve downregulation results in enhanced recycling and surface levels of AMPAR, although the underlying molecular mechanism(s) are unknown. Paradoxically, our new studies in non-neuronal cells, reveal that PIKfyve has a direct positive role in the control of the SNX17 recycling pathway. Notably, both the SNX17 and SNX27 pathways emerge from the same microdomains on endosomes. This places PIKfyve on endosomes that actively recycle both SNX17-dependent and SNX27-dependent cargoes. Importantly AMPAR surface levels are controlled in part via SNX27-dependent recycling. Aim 1 of this proposal seeks to determine whether PIKfyve controls AMPAR surface levels via negative regulation of SNX27- dependent recycling. Importantly, our new studies raise the possibility that dysregulation of SNX17 during PIKfyve inhibition, may also contribute to the observed synaptic defects. Mutations in proteins that function with SNX17 underlie some neurological diseases, but surprisingly, there are no published studies to establish whether SNX17 recycling is critical for synaptic function. The current project will test the hypothesis that PIKfyve differentially regulates distinct recycling pathways that emerge from the same endosomes. To address this hypothesis we will 1) Determine mechanisms whereby PIKfyve regulates AMPAR recycling; 2) Determine roles of the SNX17- Retriever pathway in neurons and whether similar to non-neuronal cells, PIKfyve is a regulator of this pathway.