免疫原性微核激活cGAS-STING通路并影响PS1突变诱导Aβ形成的机制研究

Presenilin-1 (PS1) mutations can cause familiar Alzheimer’s disease (AD) and is accompanied with an increased ratio of Aβ42(43)/Aβ40. How PS1 mutations influence the production of Aβ, whether innate immunity is involved in this process and how innate immunity regulates Aβ are scientific problems that are far from well understood and await further investigation urgently. The majority of newly-formed micronuclei (MN) are immunogenic (iMN) because micronuclear DNA is a cell intrinsic immuno-stimulatory molecule that triggers the cGAS-STING innate immune-sensing pathway and leads to pro-inflammatory response. AD patients possess a significant higher frequency of MN than that of healthy controls. Previously, we found that PS1 knockdown and over-expression resulted in significant increases in the frequency of MN in human neuron SH-SY5Y cells. In light of these findings, we hypothesize that PS1 mutations activate cGAS-STING innate pathway via inducing iMN, thereby increasing the Aβ42(43)/Aβ40 ratio. Here, using SH-SY5Y and human microglia HMC3 cells whose PS1 is knocked out or replaced by pathogenic mutations as the in vitro cell models, and using genetic, molecular biological and bioinformatic techniques as the main research methods, we aim to explore the biogenesis and structural alterations of iMN and the underlying mechanisms; investigate the surveillance roles of cGAS-STING pathway to iMN and the regulatory actions of cGAS-STING pathway to the Aβ42(43)/Aβ40 ratio; explore the potential ways that can inhibit the generation of iMN induced by PS1 mutations. This research project will helps to demonstrate the pathogenic mechanism of PS1 mutations through activating the iMN-cGAS-STING-Aβ signaling axis, and may provide new insights into the development of promising approaches for the intervention of early-stage AD.

PS1突变可导致早老性阿尔茨海默病（AD）并伴随着Aβ42(43)/Aβ40率的上升。PS1突变如何影响Aβ形成，是否涉及固有免疫，固有免疫又是如何调节Aβ则是远未清楚却又急需研究的科学问题。微核（MN）具有免疫原性（iMN），可激活cGAS-STING通路介导的固有免疫。AD患者的MN显著上升；我们发现敲低或过表达PS1显著增加人神经细胞MN，并据此提出PS1突变通过诱发iMN激活cGAS-STING通路进而影响Aβ形成的假说。课题以PS1敲除和转入致病性PS1突变的人神经细胞系为模型，利用遗传学、分子生物学和生物信息学研究手段，考察iMN形成、结构变化及其分子基础，研究cGAS-STING通路应答iMN以及对Aβ42(43)/Aβ40率的调节作用，探索抑制iMN的策略，以期较深入地阐明PS1突变激活iMN-cGAS-STING-Aβ信号轴的病理性作用，结果有望为AD早期干预提供新思路。

PS1（presenilin-1）突变可导致家族性阿尔茨海默病（AD），然而PS1突变如何促进AD发生和发展，是否涉及基因组不稳定性是远未清楚却又急需研究的科学问题。微核是基因组不稳定的标志，具有高突变性和免疫原性，可诱发染色体碎裂和激活cGAS-STING通路介导的固有免疫。本项目中，我们选取了人类细胞株和小鼠AD模型，利用遗传学、分子生物学和行为学等手段，重点研究了微核在AD中的发生机制和可能的病理学效应。我们发现：（1）PS1基因在表达水平出现紊乱时能够通过γ分泌酶依赖的方式诱发人神经细胞SH-SY5Y和小胶质细胞HMC3产生微核、核质桥和核芽等基因组不稳定事件。（2）在APP/PS1小鼠中，骨髓噬多染红细胞的微核率出现了与月龄相关的上升，多类组织（包括前额叶、垂体、海马和小脑等脑组织，以及结肠和腹部皮肤组织）来源的细胞端粒长度也出现了与月龄相关的下降。APP/PS1小鼠的微核增长速率与端粒长度缩短速率均高于同月龄的野生型C57BL/6小鼠。（3）重要的是，微核率的增加与端粒长度的缩短与AD小鼠的认知下降呈明显正相关效应，而在野生型C57BL/6小鼠中，这种相关性明显弱于AD小鼠。综上所述，我们发现由于突变引起的PS1表达异常可诱发微核等基因组不稳定性事件，而微核在AD的发生发展过程中发挥了关键的作用，该发现为我们理解AD的分子病理学机制提供了崭新的视角。本项目发表高水平论文17篇，毕业硕士研究生3人。