Role of Tau Cleavage in Tauopathy

该项目旨在验证一种治疗牛头病变的新药物靶点，牛头病变是一组无法治愈的神经退行性疾病，包括阿尔茨海默病（AD）。我的实验室以前使用转基因小鼠来测定微管结合蛋白tau的生物活性，这种蛋白聚集形成神经原纤维缠结，是tau病的主要特征。我们发现表达P301L tau变体（tauP301L）的rTg4510小鼠的认知功能障碍与额颞叶痴呆有关，在神经元丢失之前开始，并且独立于神经原纤维缠结或不溶性tau发生。当可溶性转基因tau蛋白减少时，认知功能得到改善（SantaCruz et al., Science, 2005）。这些结果暗示了某种形式的可溶性tau损害认知能力。接下来，我们发现tauP301L和伪过度磷酸化的野生型tau （tauEPWT）错定位到树突棘上，由于棘中谷氨酸受体的减少，导致突触传递减少（Hoover et al., Neuron, 2010）。这些数据表明病理形式的tau破坏突触功能的机制。在目前的应用中，我们证明了tauP301L或tauEPWT的特定修饰对于tau错定位到脊柱是必要和充分的。我们还发现，在轻度认知障碍和AD患者的大脑中，tau蛋白的特异性修饰形式升高。

This project aims to validate a novel drug target for tauopathies ¿ a group of incurable neurodegenerative conditions that includes Alzheimer¿s disease (AD). My lab previously used transgenic mice to assay the biological activity of the microtubule-binding protein tau, which aggregates to form neurofibrillary tangles, a cardinal feature of tauopathies. We discovered that cognitive dysfunction in rTg4510 mice expressing the P301L tau variant (tauP301L), linked to frontotemporal dementia, begins prior to neuron loss and occurs independently of neurofibrillary tangles or insoluble tau. Cognitive function improves when soluble transgenic tau is reduced (SantaCruz et al., Science, 2005). These results implicated some form of soluble tau in impairing cognition. Next, we showed that tauP301L and pseudo-hyperphosphorylated wild-type tau (tauEPWT) mislocalize to dendritic spines, which results in decreased synaptic transmission due to the reduction of glutamate receptors in the spines (Hoover et al., Neuron, 2010). These data suggested a mechanism by which pathological forms of tau disrupt synaptic function. In the current application, we show that a specific modification of either tauP301L or tauEPWT is necessary and sufficient for tau to mislocalize to spines. We also show that the specifically modified form to tau is elevated in the brains of patients with Mild Cognitive Impairment and AD. Here, we propose to test the hypothesis that the specifically modified form of tau disrupts synaptic function and impairs cognition in tauopathies. The successful completion of our goals will enable us to lay the biological foundation for discovering drugs that may block tau-related neurotoxicity in Alzheimer¿s disease and other tauopathies. This project intends to improve both our understanding of the processes that initiate AD and our ability to treat it in its earliest stages, by determining whether specific forms of tau interfere with neurotransmitter receptor trafficking in dendritic spines and memory function. Since these abnormal processes occur prior to the loss of neurons, these pathogenic tau species could become a target for therapies aimed at preventing tauopathies from developing into progressive, fatal dementias. If successful, the work could benefit millions of people.