Binding of Endophilin Endocytic Proteins to AMPA Receptors and Neuronal Voltage-gated Potassium (Kv) Channels: Regulation of Synaptic Plasticity

这项发现资助主要集中在离子通道的细胞生物学和神经组织兴奋性的调节以及学习和记忆。电压门控钾（Kv）通道和称为AMPAR的配体门控谷氨酸受体在人脑中执行许多功能，分别包括维持静息膜电位和调节记忆形成突触可塑性。钾通道Kv家族的几个成员，即Kv1.5，Kv4.2和HERG通道，以及AMPAR在大脑的一个区域中表达，称为海马体，负责编码和储存记忆。 越来越多的证据表明，通常参与微小膜囊泡再循环的一些蛋白质可以调节存在于神经细胞表面的特定膜受体和离子通道的密度。内嗜蛋白家族的再循环蛋白含有优先结合富含脯氨酸氨基酸的蛋白质序列的特定区域。 也已知内吞蛋白质与其他内吞蛋白质机制结合，包括发动蛋白2，以及与称为Arc/Arg3.1（Arc）的立即早期基因结合，该基因也作为最近激活的神经细胞的标记物。 Arc也被证明可以调节AMPAR的表面表达，Arc的基因消融导致记忆保留缺陷。最近，我们报道了腺苷A1受体（A1 R）引起网格蛋白介导的AMPAR内化，这是A1 R介导的海马突触传递减少的基础。 然而，目前尚不清楚脑中Kv通道是否也存在类似的内嗜蛋白-Arc驱动的AMPAR内化机制。 由于一些KV通道的胞质区域含有适当的模式，为endophilin结合，我们将调查的可能性，一些KV通道直接耦合到endophilin。这种相互作用可以促进这些Kv通道往返于神经表面的再循环，这可以影响神经兴奋性和记忆形成分子（如AMPAR）的作用。 该提案围绕这三个目标： 1)确定内嗜蛋白是否调节神经细胞中Kv通道和AMPAR的再循环和整体功能; 2)确定Kv通道和AMPAR的富含脯氨酸的区域是否是内啡肽结合的靶标;以及 3)确定是否与Kv和AMPAR的内啡肽相互作用影响大脑记忆中心内神经元的兴奋性和记忆形成能力。 这些研究将为Kv通道和AMPAR的生理学，神经通信的调节以及有助于大脑学习和记忆的因素提供新的见解。 从长远来看，这项工作将有助于评估特定的钾通道作为目标，以防止过度的神经元兴奋，如癫痫发作和随后的记忆丧失。

This Discovery Grant is focused on the cellular biology of ion channels and regulation of nervous tissue excitability and learning and memory. The voltage-gated potassium (Kv) channels and ligand-gated glutamate receptors called AMPARs perform many functions in the human brain, including maintenance of resting membrane potential and regulation of memory-forming synaptic plasticity, respectively. Several members of the Kv-family of potassium channels, namely the Kv1.5, Kv4.2 and HERG channels, and AMPARs are expressed in an area of the brain, called the hippocampus, which is responsible for encoding and storing memory. Increasing evidence suggest that some proteins normally involved in the recycling of tiny membrane vesicles can regulate the density of specific membrane receptors and ion channels present on the surfaces of nerve cells. The recycling proteins of the endophilin-family contain a specific region that preferentially binds to protein sequences enriched with proline amino acids.  Endophilin proteins are also known to bind to other endocytic protein machineries, including dynamin 2, and to the immediate-early gene called Arc/Arg3.1 (Arc), which also serves as a marker for recently activated nerve cells.  Arc has also been shown to regulate the surface expression of AMPARs, and genetic ablation of Arc leads to memory retention deficits. Recently we reported that the adenosine A1 receptor (A1R) causes clathrin-mediated internalization of AMPARs, which underlies A1R-mediated reduction in hippocampal synaptic transmission.  However, it is not yet known whether a similar mechanism for endophilin-Arc-driven AMPAR internalization also occurs for Kv channels in the brain.  Since the cytoplasmic regions of some Kv channels contain appropriate patterns for endophilin binding, we will investigate the possibility that some Kv channels are directly coupled to endophilin. This interaction can facilitate the recycling of these Kv channels to and from the nerve surface, which can affect nerve excitability and action of memory-forming molecules, such as the AMPARs. The proposal is centered on these three aims: 1) To determine whether endophilin regulates the recycling and overall function of the Kv channels and AMPARs in nerve cells; 2) To determine whether the proline-rich regions of Kv channels and AMPARs are targets for endophilin binding; and 3) To determine whether the endophilin interactions with Kv and AMPARs influence the excitability and memory-forming capacity of neurons within the brain’s memory center. These studies will provide new insight into the physiology of Kv channels and AMPARs, regulation of nervous communication, and factors that contribute to learning and memory in the brain.  In long term, this work will assist in the evaluation of specific potassium channels as targets to prevent excessive neuronal excitability, such as seen with seizures and subsequent memory loss.