泛素蛋白酶体调节BDNF更新在短期记忆退化干扰中的作用

Whereas signaling pathways involved in initiation of memory formation have been investigated widely, the basics of memory decline remain to be specified. A theory about memory decline emphasizes the retrograde interference with memory, showing that specific (similar learning task) or unspecific (novelty, working memory) brain activities modulate the consolidation of memory traces. A possible cellular mechanism thereby might be the interference of modulated synaptic transmission after memory formation with new learning events. In my studies of activity-dependent synaptic plasticity, I found that inhibition of ubiquitin-proteasome system (UPS) removes the immunity of already established memory traces to new learning events. In addition, the brain-derived neurotrophic factor (BDNF) gene with its multiple transcripts has been recognized as a key factor for learning, but the involvement of BDNF mRNA with short-3' untranslated region (UTR) or long-3'UTR in memory persistence needs clarification. In particular, evidence suggests that long-3'UTR tails targets BDNF mRNA into dendrites, making it a prime candidate for a role in synaptic plasticity..BDNF-related signaling is important for learning and for regulation of the synaptic proteome including components of UPS; furthermore, UPS is involved in BDNF turnover. Hence I propose to test the basic hypothesis that the interaction of UPS and BDNF-related signaling is a critical cellular mechanism underlying the retrograde interference with memory..Based on this global hypothesis, I propose to test the following sub-hypotheses:.1).UPS-inhibition enhances short-term memory decline in response to retrograde interference tasks and.2).translation of long-3'UTR BDNF mRNA restores UPS-inhibition enhanced memory decline..Moreover, at the cellular and neuronal level, I propose that.3).UPS-dependent abrogation of immunity against heterosynaptic depotentiation during memory trace formation is prevented by BDNF and for that.4).dendritic BDNF synthesis is required..To this end, I propose pharmacological inhibition of UPS and one-trial passive avoidance learning in combination with retrograde interference tasks and electrophysiological analysis of activity-dependent synaptic potentiation in acute brain slices and primary neuronal cell cultures. The crosstalk of UPS and overexpressed BDNF as well as the specific role of BDNF transcripts in these paradigms is investigated by AAV-mediated transfection..The proposed research will provide new insights on cellular mechanisms on physiological and pathological memory decline and promotes the development of new means to reduce memory decline in Alzheimer's patients with dementia, whose memory is highly vulnerable to new environments and tasks.

心理学研究提示特异性或非特异性的干扰能够消除前期形成的短期记忆.然而该原理在实验模型中尚未得到验证.前期实验也显示抑制UPS的活性能够消除已有记忆耐受新事物干扰的免疫力.脑源性神经营养因子（BDNF）被认为是记忆形成的关键,其相关信号通路对记忆形成和突触蛋白调节具有重要作用,且合成过程由UPS参与.本项目提出1)抑制UPS活性加剧干扰导致的短时记忆减退2)提高BDNF表达能逆转UPS抑制介导的记忆减退 3)该过程需要树突中新合成BDNF的假设.本项目拟建立被动回避实验模型,通过调节UPS的活性观察AAV病毒转染的GFP-BDNF的调节作用,并研究二者的交互性;运用实时成像和免疫印迹技术检测BDNF在急性分离的海马脑片和原代培养的海马神经元中的表达,阐明树突中BDNF的合成在记忆减退中的作用.本项目将会为研究"遗忘"的细胞机制提供新的思路,并为寻求干预记忆退化的新策略提供实验依据.

BDNF基因和它的多种转录本被认为是记忆形成的重要因子, 但是非转录区短3’端BDNF转录本在学习记忆中的作用还需要进一步分析。通过被动回避实验，我们发现海马区BDNF蛋白过表达的小鼠，其短期记忆以及长期记忆的形成都得到了促进，而长期记忆的消退也得到了抑制。BDNF 的表达加强了突触可塑性相关蛋白的磷酸化和提高了被动回避和物体位置识别能力,而不是重新物体识别能力。但是高剂量的BDNF在海马中过表达有可能诱发小鼠癫痫，恐惧行为加强伴随着被动回避下降。因而在野生品系小鼠中，控制海马CA1区BDNF的适量表达,可以提高恐惧和物体位置识别记忆。

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