RPS23RG家族在海马神经环路功能和学习记忆中的作用研究

Brain hippocampus is an important structural basis for learning and memory. Neural circuits of the hippocampus are impaired in Alzheimer’s disease (AD) patients, who have learning and memory defects. AD has two important pathological features: senile plaques composed of β-amyloid (Aβ) peptides and neurofibrillary tangles formed by hyperphosphorylated microtubule-binding protein tau. Excessive production and accumulation of Aβ in the brain is primary cause of AD. We previously identified a new mouse gene family, Rps23rg, originated through retroposition of the mouse Rps23 (ribosomal protein S23) mRNA and showed that RPS23RG proteins simultaneously suppress Aβ generation and tau phosphorylation. In preliminary data, we found that retroposition of the human RPS23 mRNA also resulted in a functionally expressed Rps23rg human homolog, which we call hRPS23RG1. Notably, hRPS23RG1 also inhibited Aβ generation and tau phosphorylation and its expression was markedly decreased in AD brain. In addition, we found that downregulation of mouse Rps23rg impaired synaptic function. In this project, we will study the characteristics and transcriptional regulation of hRPS23RG1, determine the molecular mechanism underlying hRPS23RG1-inhibited Aβ generation and tau phosphorylation, and explore the involvement of hRPS23RG1 in neuronal cell differentiation and in synaptic function, using neurons differentiated from human embryonic stem cells. By applying viral injection and generating Rps23rg gene knockout mice, we will modulate the levels of RPS23RG in mouse brain hippocampus and study the effects of RPS23RG on the hippocampal neural circuit functions, as well as on AD-like phenotypes in AD mice. Our study will elucidate the participation of RPS23RG in AD and provide new targets for disease intervention.

阿尔茨海默病AD患者的海马神经环路发生损害，出现学习记忆障碍。AD有两个重要的病理特征和致病因素：Aβ多肽聚集形成淀粉样斑和tau蛋白过度磷酸化形成纤维缠结。我们在小鼠基因组中鉴定出新基因家族Rps23rg，是由小鼠Rps23 mRNA发生返座而起源。小鼠RPS23RG家族成员能够同时抑制Aβ产生和tau磷酸化。前期工作发现人RPS23 mRNA也发生返座，在人基因组中产生1个功能表达的同源蛋白hRPS23RG1。hRPS23RG1抑制Aβ产生和tau磷酸化，其表达在AD中明显降低。此外，下调小鼠Rps23rg会损害神经突触功能。我们将在诱导分化形成的人神经细胞中研究hRPS23RG1的生化特性、表达调控、对神经细胞分化和功能的影响、以及参与AD的机制。我们将应用病毒感染和构建基因敲除小鼠，调控海马区的RPS23RG水平，研究其在海马神经环路的功能以及对AD病理和学习记忆障碍的治疗作用。

本项目研究我们新近在小鼠中鉴定的RPS23RG基因家族对于海马神经环路功能和学习记忆中的作用，以及该基因家族的异常在阿尔茨海默病AD中的参与。在项目支持下，我们首先确定了人源hRPS23RG1蛋白可以像小鼠RPS23RG1蛋白一样，通过与adenylate cyclase相互作用，增加cAMP的水平，进而促进PKA的活性，从而抑制GSK-3，最终同时降低A的产生和tau蛋白的磷酸化。更重要的是，我们发现人源RPS23RG1基因的表达在AD病人中有所下降。我们最近又发现人源RPS23RG1基因上有两个错义突变和1个同义突变，且两个错义突变表现为连锁突变。通过分析单核苷酸多态性的分型结果和等位基因的分布频率，我们初步发现这两个连锁错义突变在AD患者中的纯合突变率比对照组明显升高。这些结果提示人源RPS23RG1基因可能参与了AD疾病过程。.此外，我们发现过表达RPS23RG1可以增加神经元的突触数量和PKA/GSK-3信号通路的活化，并且在小鼠中拮抗因寡聚化A毒性所导致的神经突触、海马LTP以及学习认知记忆的损害。这些结果提示，促进RPS23RG基因家族的表达活性可能作为AD疾病治疗的一种策略。.我们最近应用TALEN技术构建了Rps23rg1敲除小鼠，发现该基因的纯合敲除小鼠仍然可以存活，表明该基因不具备看家基因功能。但这些小鼠的PSD95水平显著降低，提示其神经突触功能发生了损害。行为学研究表明Rps23rg1敲除小鼠的认知记忆出现障碍，而电生理学研究证实Rps23rg1敲除小鼠的海马环路的突触后膜功能也发生异常。进一步的机制研究发现，RPS23RG1蛋白可以与PSD95相互作用，影响PSD95的降解。.在项目支持下，我们已经发表了标记项目资助SCI论文17篇，并获得一项中国专利。