lncRNA-HN促进hnRNP-U核转位介导铅暴露影响学习记忆机制的研究

Our previous study showed that lead exposure increased the expression of NRSF and inhibited the transcription level of synaptic vesicle associated protein, resulting in the decrease of its protein level, thereby affecting learning and memory. The mechanism of lead exposure affects the NRSF expression resulting in learning and memory disorder is unclear. lncRNA plays an important role in gene regulation. The high-throughput sequencing and quantitative real-time PCR (qPCR) technology showed that lncRNA-HN expression significantly increased in lead exposed model, and the expression of NRSF decreased significantly after lncRNA-HN silencing. We use RNA binding protein immunoprecipitation technique to show specific binding between lncRNA-HN and heterogeneous nuclear ribnucleoprotein U (hnRNP-U), and hnRNP-U nuclear translocation was observed in lead exposure model. Using bioinformatics analysis, we found that hnRNP-U interacts with neuron-restrictive silencer factor (NRSF). Therefore, we speculate that lead exposure increases the expression of lncRNA-HN and promotes the nuclear transposition of hnRNP-U, and then regulates the expression of NRSF. This project will study the role of lncRNA-HN in lead exposure on learning and memory at overall and cellular levels, and provide a new idea and theoretical basis for early diagnosis and treatment of neurotoxicity of lead exposure.

我们前期研究表明铅暴露上调神经元限制性沉默因子（NRSF）的表达，抑制突触囊泡相关蛋白的转录水平，导致其蛋白水平下降从而影响学习记忆。铅暴露如何影响NRSF表达导致学习记忆障碍，其机制不清楚。lncRNA在基因调控方面发挥着重要作用，预实验通过高通量测序并经qPCR技术发现在铅暴露模型中lncRNA-HN的表达明显升高，沉默lncRNA-HN后NRSF的表达显著下降。我们采用RNA结合蛋白免疫共沉淀技术显示lncRNA-HN与hnRNP-U有特异性的结合，并且在铅暴露模型中观察到hnRNP-U核转位。通过生物信息学分析hnRNP-U可与NRSF相互作用。故我们推测铅暴露可通过上调lncRNA-HN表达，促进hnRNP-U核转位，进而调控NRSF的表达。本项目将在整体和细胞水平深入研究lncRNA-HN在铅暴露影响学习记忆中的作用，为早期诊断和治疗铅暴露的神经毒性提供新的思路和理论基础。

铅是一种广泛存在于自然界的有毒重金属，慢性铅暴露可造成机体多个系统损伤，其中铅对神经系统，尤其是对婴幼儿和儿童智力发育及学习记忆具有严重损伤。铅暴露导致转录因子和转录调节因子的改变可能是铅损害学习和记忆行为的重要机制之一。铅可通过干扰转录因子的转录活性来改变下游基因的转录从而调节细胞生命过程。此外，铅暴露还可能通过改变凋亡相关蛋白和突触可塑性蛋白的mRNA水平，进而导致神经元功能障碍。铅暴露会改变转录因子Kaiso、NF-κB和NR4A1，以及转录调节因子hnRNP U、hnRNP K和HDAC5的表达。通过生物信息学预测筛选到凋亡相关基因（RBBP4、AKT3和 NPAS4）和突出可塑性调节基因（REST、UCP2和β-catenin）的转录受到转录因子（Kaiso、NF-κB和NR4A1）以及转录调节因子（hnRNP U、hnRNP K、HDAC5）调控。因此本项目在预实验的基础上进一步研究铅暴露调控REST表达的原因。明确铅是否通过影响Kaiso、NF-κB、hnRNP U、hnRNP K、NR4A1和HDAC5来调控RBBP4、AKT3、 NPAS4、REST、UCP2和β-catenin的转录水平，干扰上游转录调控因子是否能逆转铅对其转录水平的影响，这将对进一步阐明铅的神经毒性分子机制和寻找新的治疗铅中毒药物有重要的理论和实际指导意义。