靶向活化SIRT1调节tau外显子10可变剪接在阿尔茨海默病防治中的作用

Tau malfunction can trigger neurodegeneration, known as tauopathies. Adult human brain expresses six isoforms of tau from a single gene by alternative splicing of its pre-mRNA. Alternative splicing of exon 10 (E10) divides tau isoforms into two main groups, three (3R)- or four (4R)-microtubule-binding repeat tau. Approximately equal amounts of 3R-tau and 4R-tau are expressed in normal adult human brain. Imbalance of 4R-tau/3R-tau results in tauopathies. Splicing factor SC35 play very important role in the promotion of tau exon 10 inclusion. It's activity is highly regulated by phosphorylation. But the function of another post-translational modification of SR proteins known as acetylation has not been determined. In the preliminary data, we found that: 1. SIRT1 regulated the alternative splicing of tau exon 10; 2. the promotion of tau exon 10 inclusion by SC35 was markedly suppressed by overexpressed SIRT1; 3. SIRT1 directly interacted with SC35; 4. in AD brain, the balance of 3R tau and 4R tau was disrupted and the protein level of SIRT1 was decreased. These data indicate that the reduction of SIRT1 may correlate with the dysregulation of tau exon 10 splicing in AD brain. The specific goal of this project is to investigate how the targeted adjustment of SIRT1 regulates the alternative splicing of tau exon 10 in vitro and in vivo even in AD brain, which will provide significant new insights into the molecular mechanism of neurodegenerative disease related to the alternative splicing of tau exon 10.

Tau的病变导致神经退行性疾病，称tau蛋白病。经可变剪接，正常人脑表达六种tau变异体。外显子10是否编码决定tau含3或4个微管结合重复片段(3R、4R)，正常人脑中比例约为1。Tau mRNA异常剪接使其表达失衡，引起某些tau蛋白病。SC35是调节tau外显子10可变剪接的重要剪接因子，活性受磷酸化严格调节，而乙酰化对其功能调控的研究薄弱。SIRT1是与AD相关的去乙酰化酶。预实验发现1.SIRT1调节外显子10可变剪接；2.SIRT1抑制SC35所促进的外显子10的编码；3.SIRT1与SC35相互作用；4.AD患者脑中3R/4R-tau表达失衡，SIRT1表达下降。提示SIRT1与AD患者脑中tau外显子10剪接失调有关。本课题拟在分子、细胞、动物和AD患者脑组织，系统研究靶向调节SIRT1对外显子10可变剪接的影响，为与tau外显子10剪接相关神经退行性疾病的防治提供分子依据

通过可变剪接，正常成人脑表达六种tau变异体。外显子10编码与否决定tau含3或4个微管结合重复片段（3R、4R）。正常人脑表达等量的3R-tau和4R-tau，其表达失衡可引起某些tau蛋白病。剪接因子SC35与9G8调节tau外显子10可变剪接，且活性受乙酰化调节。本课题的研究揭示了去乙酰化酶Sirt1如何通过调节SC35或9G8的乙酰化水平来影响它们在tau外显子10的可变剪接中的调控作用。本课题研究发现：1.Sirt1与SC35存在直接相互作用；2.过表达SC35明显促进tau外显子10的编码，而Sirt1抑制SC35对tau外显子10 编码的促进作用；3. Sirt1对SC35具有去乙酰化作用。4. Sirt1与9G8也存在相互作用；5. 过表达9G8明显抑制tau外显子10的编码，而Sirt1阻遏了9G8对tau外显子10 编码的抑制作用；6. Sirt1在第24位赖氨酸对9G8进行去乙酰化作用。7.白藜芦醇增强了Htau小鼠脑中Sirt1的表达量，明显抑制Htau小鼠脑中3R-tau的蛋白表达水平。白藜芦醇可以改善Htau小鼠的空间记忆缺陷。8. AD患者脑中SIRT1蛋白表达异常与3R-tau和4R-tau表达失衡有相关性。总之，SC35或9G8调节tau外显子10的编码。Sirt1与之相互作用并使之去乙酰化从而抑制它们在调节tau外显子10编码中的作用。以上研究发现提示AD脑中Sirt1的蛋白表达水平异常通过调节SC35、9G8使tau外显子10剪接失调，导致3R-tau、4R-tau的比例失衡。可能启始或加速了tau的病理改变，引发神经退行性疾病。