Roles and regulation of PI(3,5)P2 and PI5P in neurons

描述（由申请人提供）：我们的长期目标是确定磷脂酰肌醇(3,5)-二磷酸（PI3,5P2）在神经元中的作用和调控。我们最近意外地发现，PI3, 5P2是突触强度的关键上游调节因子。PI3和5P2的丰度很低。它的合成需要脂质激酶PIKfyve和PIKfyve调节因子：Vac14和Fig4。我们对小鼠突变体的研究，以及对图4中突变的人类患者的发现，确立了PI3、5P2在神经系统中的普遍重要性。我们最近的两个发现改变了目前对神经元中PI3, 5P2信号通路的作用的认识。首先，Vac14-PIKfyve-Fig4复合物在兴奋性突触中起抑制作用，并影响突触前和突触后功能。其次，这些研究强烈表明，Vac14-PIKfyve-Fig4复合体通过其在细胞膜运输中的作用，在特定形式的突触可塑性中起着关键作用。此外，来自我们和其他人的新数据表明，PI3, 5P2是神经元和其他细胞类型中多种途径的关键上游调节剂。在这里，我们重点研究了PIKfyve、Vac14和Fig4对化学长期抑制和稳态降尺度的要求。此外，我们还与密歇根大学的许浩兴博士合作开发了一种pi35,5p2荧光探针。我们期望这个探针将极大地扩展我们和其他人研究神经元中PI3,5P2的能力。本提案的总体目标是：1)确定PI3、5P2和PI5P是否对特定形式的突触可塑性至关重要。2)确定PIKfyve的瞬时激活是否需要钙，以及PIKfyve和/或AMPA受体的定位在激活过程中是否发生变化。这些拟议的研究有可能为突触可塑性的分子基础的现有知识提供重大进展，并促进对学习和记忆所需的分子机制的理解。

DESCRIPTION (provided by applicant): Our long-range goals are to determine the roles and regulation of phosphatidylinositol (3, 5)-bis phosphate (PI3,5P2) in neurons. We recently made the unexpected discovery that PI3, 5P2 is a critical upstream regulator of synaptic strength. PI3,5P2 is in very low abundance. Its synthesis requires the lipid kinase PIKfyve and PIKfyve regulators: Vac14 and Fig4. Our studies of mouse mutants, as well as discovery of human patients with mutations in Fig4, establish the general importance of PI3, 5P2 within the nervous system. We recently made two findings that change current knowledge of the roles of the PI3, 5P2 signaling pathway in neurons. First, the Vac14-PIKfyve-Fig4 complex plays an inhibitory role at excitatory synapses, and affects both presynaptic and postsynaptic function. Second, studies shown here strongly suggest that the Vac14-PIKfyve-Fig4 complex, via its role in endomembrane trafficking, plays a critical role in specific forms of synaptic plasticity. In additin, emerging data from us and others indicate that PI3, 5P2 is a critical upstream regulator of multiple pathways both in neurons and other cell- types. Here we focus on the requirement of PIKfyve, Vac14 and Fig4 for chemical long-term depression and homeostatic down scaling. In addition, in collaboration with Dr. Haoxing Xu (U. Michigan) we have developed a fluorescent probe for PI3,5P2. We anticipate that this probe will greatly expand the ability of us and others to study PI3,5P2 in neurons. The overall goals of this proposal are to 1) Determine whether PI3, 5P2 and PI5P are essential for specific forms of synaptic plasticity. 2) Determine whether calcium is required for the transient activation of PIKfyve, and whether PIKfyve and/or AMPA receptor localization changes during this activation. These proposed studies have the potential to provide significant advances in current knowledge of the molecular basis of synaptic plasticity, as well as advance understanding of molecular mechanisms required for learning and memory.