Decoding the RGS14 Interactome/Signalosome in CA2 hippocampal neurons

 描述(由申请人提供)：最近备受瞩目的报告发现，神秘的海马区CA2位于一个全新的海马区回路的中心，该回路对于与自闭症和精神分裂症有关的社会学习至关重要。与众所周知的三突触(齿状回(DG)-CA3-CA1)海马回路不同，人们对CA2区知之甚少。此前，这一大脑区域曾间接与自闭症/双相情感障碍和精神分裂症有关。然而，这些新的报告证明了CA2的S在社会学习中的重要作用，提供了一个令人信服的新联系，将自闭症/双相情感障碍的大脑区域与精神分裂症联系起来。因此，了解CA2神经元中的信号蛋白和信号通路为开发新的治疗工具来治疗这些毁灭性和令人烦恼的疾病提供了一个令人兴奋的新机会。我们已经证明，脑蛋白RGS14在成年小鼠和人的海马区CA2区的锥体神经元中表达。RGS14是一种不寻常的支架/效应蛋白，它整合了G蛋白、MAPKinase和突触可塑性所必需的Ca++/CaM信号通路。我们最近发现，RGS14是CA2神经元突触可塑性的天然抑制因子，而不是CA1。缺乏RGS14(RGS14-KO)的小鼠表现出显著的和意想不到的CA2神经元长时程增强(LTP)和基于海马区的空间学习和记忆的获得，而在其他行为上没有差异。这些发现突显了了解RGS14调节其天然宿主海马神经元突触可塑性的分子机制(S)的重要性。到目前为止，对CA2神经元中的信号蛋白/通路知之甚少。此外，我们对RGS14信号功能的理解在很大程度上是基于非天然表达系统中重组RGS14与合作伙伴的结合作用。基于这些发现，我们的工作假设是RGS14是一个中枢神经网络，调节突触功能和可塑性所必需的信号通路。然而，关于天然RGS14的天然结合伙伴以及它在天然宿主CA2神经元中参与的信号通路尚不清楚。与这一观点一致，我们的初步研究表明，天然的RGS14以高分子量蛋白质复合体的形式存在，并与脑中身份不明的伙伴结合。这些研究的目的是为未来的研究确定表达RGS14的CA2海马神经元中新的信号通路，以及天然RGS14参与调节突触可塑性的特定信号通路。目的1：利用生物信息学分析方法确定表达RGS14的CA2神经元的细胞转录组和蛋白质组，以及CA2特异性信号转导通路。目的2：从脑中鉴定天然RGS14的天然结合伙伴(野生型与RGS14-KO)。目的：研究新发现的CA2受体通路在野生型和RGS14-KO小鼠海马脑片CA2神经元LTP调节中的作用。

 DESCRIPTION (provided by applicant): Recent high profile reports have identified the enigmatic hippocampal area CA2 as being at the center of an entirely new hippocampal circuit that is essential for social learning linked to autism and schizophrenia. Unlike the well-understood trisynaptic (dentate gyrus (DG)-CA3-CA1) hippocampal circuit, very little is known about area CA2. Previously, this brain region had been indirectly implicated in the autism/bipolar spectrum of disorders and schizophrenia. However, these new reports demonstrating CA2's essential role in social learning provide a compelling novel link between this brain region with autism/bipolar disorders and schizophrenia. Therefore, understanding signaling proteins and pathways in CA2 neurons offers an exciting new opportunity for the development of novel therapeutic tools to treat these devastating and vexing diseases. We have shown that the brain protein RGS14 is expressed in pyramidal neurons of hippocampal region CA2 in adult mouse and humans. RGS14 is an unusual scaffold/effector protein that integrates G protein, MAPkinase, and Ca++/CaM signaling pathways essential for synaptic plasticity. We recently discovered that RGS14 is critically important as a natural suppressor of synaptic plasticity in CA2 neurons but not CA1. Mice lacking RGS14 (RGS14-KO) exhibit a marked and unexpected enhancement of long-term potentiation (LTP) in CA2 neurons and in the acquisition of hippocampal-based spatial learning and memory, with no differences in other behaviors. These findings highlight the importance of understanding the molecular mechanism(s) whereby RGS14 regulates synaptic plasticity in its natural host CA2 hippocampal neurons. To date, very little is known about signaling proteins/pathways in CA2 neurons. Furthermore, our understanding of RGS14 signaling functions is based largely on binding interactions of recombinant RGS14 and partners in non-native expression systems. Based on these findings, our working hypothesis is that RGS14 is a central nexus that regulates signaling pathways essential for synaptic function and plasticity. Yet nothing is known about natural binding partners of native RGS14, and the signaling pathways it engages within its natural host CA2 neurons. Consistent with this idea, our preliminary studies show that native RGS14 exists as a high molecular weight protein complex and binds unidentified partners from brain. The goal of these studies is to define novel signaling pathways in RGS14-expressing CA2 hippocampal neurons for future study, and the specific signaling pathways that native RGS14 engages to regulate synaptic plasticity. AIM 1: Determine the cell transcriptome and proteome of RGS14-expressing CA2 hippocampal neurons and CA2-specific signaling pathways using bioinfomatics analysis. AIM 2: Identify natural binding partners of native RGS14 from brain (wild type vs RGS14-KO). AIM 3: Determine roles for newly identified CA2-specific receptor pathways in regulating LTP in CA2 neurons of hippocampal slice preparations from wild type and RGS14-KO mice.