Mechanisms Underlying Tau45-230-Induced Neuronal Degeneration

 描述(申请人提供)：tau在神经退行性疾病中的潜在病理机制尚未完全阐明。然而，越来越多的证据表明，tau的翻译后修饰，而不是磷酸化，可能在这些机制中发挥重要作用。最近，我们已经证明了其中一种修饰是Calain介导的tau裂解。这种切割导致了17 kDa tau45-230片段的产生，在阿尔茨海默病(AD)和其他tau病的背景下。此外，我们的数据表明，该片段可诱导培养的海马神经元进行性变性。相反，阻止这种片段产生的条件与增强中枢神经元的神经元存活率有关。此外，在表达tau45-230的转基因小鼠中，检测到神经元死亡、突触丢失和行为异常增加。综上所述，这些数据提供了证据表明，tau裂解成这种神经毒性片段是神经退行性变的一种保守的分子致病途径。另一方面，tau45-230诱导退化和细胞死亡的机制尚不清楚。根据我们的初步结果，我们假设tau45-230可能通过双重机制发挥其神经毒性作用：1)tau45-230可以调节全长tau的聚集，导致更小和更有毒的聚集体的形成；2)tau45-230可以作为单体或小聚集体干扰tau的全长生物学功能。为了验证这些假说，我们建议：1)评估tau45-230聚集体在AD和其他tau病患者脑样本中的存在和毒性；2)确定tau45-230在多大程度上调节全长tau聚集；以及3)确定tau45-230改变中枢神经元tau功能的机制。这些实验将通过多种技术相结合的方式进行，包括：蛋白质印迹分析、免疫细胞化学、体外聚合分析、聚集体纯化、同源重组技术、微管结合分析、活细胞显微镜和细胞活力分析。这些研究可能导致一种新的分子退变途径的鉴定。此外，它们还可以为AD和其他疾病的诊断、预防以及最终的治疗提供有用的帮助。

 DESCRIPTION (provided by applicant): The mechanisms underlying tau pathology in neurodegenerative diseases have not been completely elucidated. However, a growing body of evidence suggests that tau posttranslational modifications, other than phosphorylation, might play an important role in those mechanisms. Recently, we have shown that one of such modifications is calpain-mediated tau cleavage. This cleavage leads to the generation of the 17 kDa tau45-230 fragment in the context of Alzheimer's disease (AD) and other tauopathies. In addition, our data indicated that this fragment induced progressive degeneration in cultured hippocampal neurons. Conversely, conditions that prevented the generation of this fragment were associated with enhanced neuronal survival in central neurons. Furthermore, increased neuronal death, synapse loss, and behavioral abnormalities have been detected in transgenic mice expressing tau45-230. Together, these data provide evidence indicating that tau cleavage into this neurotoxic fragment is a conserved molecular pathogenic pathway of neurodegeneration. On the other hand, the mechanisms by which tau45-230 induces degeneration and cell death remain unknown. Based on our preliminary results, we hypothesize that tau45-230 could exert its neurotoxic effects through a dual mechanism: 1) tau45-230 could modulate the aggregation of full-length tau inducing the formation of smaller and more toxic aggregates; and 2) tau45-230 could interfere, either as a monomer or as small aggregates, with full-length tau's biological functions. To test these hypotheses, we propose to: 1) assess the presence and toxicity of tau45-230 aggregates in brain samples obtained from AD and other tauopathy subjects; 2) determine to what extent tau45-230 modulates full-length tau aggregation; and 3) identify the mechanisms by which tau45-230 alters tau function in central neurons. These experiments will be performed by means of a combination of techniques including: Western blot analysis, immunocytochemistry, in vitro polymerization assays, aggregate purification, homologous recombination techniques, microtubule-binding assays, live cell microscopy, and cell viability assays. These studies could lead to the identification of a novel molecular pathway of degeneration. In addition, they could provide useful for the diagnosis, prevention, and eventually the treatment of AD and other tauopathies.