The Role of SNX8 in Alzheimer’s Disease

阿尔茨海默病（Alzheimer’sdisease，AD）一个重要的病理学特征是在神经细胞外形成主要由β淀粉样蛋白（βamyloid，Aβ）组成的淀粉样斑（amyloidplaques）。大脑内具有神经毒性的Aβ的累积在AD的发病过程中处于中心地位。β淀粉样蛋白前体蛋白（βamyloidprecursorprotein，APP）依次经过β分泌酶和γ分泌酶切割后可以产生Aβ和APP的胞内结构域（APPintracellulardomain，AICD）。APP还可以被α分泌酶切割产生具有神经保护作用的sAPPα。许多研究发现α分泌酶主要在细胞膜上对APP进行切割，而β分泌酶主要在内体（Endsom...One of the neuropathologic hallmarks of Alzheimer’s disease (AD) is the presence of senile plaques which consist of β-amyloid peptide (Aβ) in the brain. Accumulation of the neurotoxic Aβ in the brain is central to the pathogenesis of AD. Aβ is derived from β-amyloid precursor protein (APP) through sequential cleavages by the β-secretase and the γ-secretase. In addition to amyloidogenic processing,...学位：理学博士院系专业：生物医学研究院_化学生物学学号：3052010015394

原癌基因K-Ras调控APPThr668位点磷酸化及APP的切割

在阿尔茨海默症(Alzheimer′s disease,AD)发病的早期,Ras蛋白所在的信号通路被激活,但具体作用机制还不清楚.探讨了K-Ras及其突变体K-RasG12V对淀粉样前体蛋白(amyloid precursor protein,APP)的剪切的影响.Western blot结果显示,过量表达K-Ras能够激活细胞外调节蛋白激酶1/2(extracellular signal-regulated kinase,ERK 1/2)、c-Jun氨基末端激酶(c-Jun N-terminal kinase,JNK)通路,并增加APP在Thr668的磷酸化;抑制JNK通路则阻断了K-Ras过表达所引起的APP Thr668磷酸化.此外,过表达K-Ras造成分泌到细胞外的sAPPα增加,而sAPPβ减少.通过生物素标记实验发现,过表达K-Ras使得APP在细胞膜上的定位增加,而细胞内APP总量没有改变.这些结果表明,过量表达K-Ras可以通过调控JNK的通路,增加APP在Thr668位点的磷酸化,造成APP在细胞膜上水平升高,导致APP向sAPPβ的切割减少,而向sAPPα的切割增加.提示K-Ras对APP切割的影响可能在AD的发病过程中起着一定的应激作用

Mechanism Underlying the Brain-specific Membrane-anchored Protein TMEM59L-mediated Apoptosis

TMEM59l为近年来新发现的脑特异性高表达蛋白,具有促凋亡效果,但其具体的凋亡机制还不清楚.构建了TMEM59l重组质粒,并在HEk293T细胞中过表达TMEM59l,用AnnEXIn V-fITC/PI双染法确定了TMEM59l可以诱导细胞凋亡,之后用免疫印迹方法检测细胞内凋亡相关分子激活情况.结果显示,外源TMEM59l可以降低bCl-2的蛋白表达水平,诱导细胞色素C从线粒体释放进入细胞质,并且激活CASPASE-9、CASPASE-7和CASPASE-3,但不激活CASPASE-8;活化的CASPASE-7和CASPASE-3进一步酶解死亡底物PArP,导致细胞凋亡;此外,用广谱CASPASE抑制剂z-VAl-AlA-ASP-fMk(z-VAd-fMk)抑制CASPASE-7和CASPASE-3活性后,死亡底物PArP的酶解也基本被抑制.由此可见,TMEM59l是通过CASPASE依赖的线粒体途径诱导HEk293T细胞凋亡.Apoptosis plays a key role in multiple biological functions and dysregulation of apoptosis leads to disease pathogenesis.Therefore,identification of new proteins mediating apoptosis and elucidation of the underlying mechanism is important not only for basic research but also for disease intervention.TMEM59L is a newly-found brain-specific anchored protein with very limited information.One study reported that TMEM59L could induce apoptosis.But the underlying mechanism remains elusive.In this paper,TMEM59L recombinant plasmid was constructed and transfected into HEK293 cells.Through Annexin V-FITC/ propidium iodide double staining and flow cytometry assay,it was confirmed that overexpression of TMEM59L could dramatically induce cell apoptosis.Through Westen blotting study,it was also found that overexpression of TMEM59L could reduce the protein level of Bcl-2,induce cytochrome c release from mitochondria to the cytosol,and activate caspase-9,caspase-3 and caspase-7,but not caspase-8.Consistently,overexpression of TMEM59L promoted the cleavage of death substrate PARP by activated caspases.While cleavage of PARP upon TMEM59L overexpression was dramatically decreased when cells were treated with a caspase inhibitor Z-Val-Ala-Asp-FMK(Z-VAD-FMK).Together these results suggest that TMEM59L can induce apoptosis through a caspase-dependent mitochondrial pathway.Because of its high abundance in the brain,TMEM59L might participate in the physiological apoptosis during neural development and/or pathological apoptosis during neurodegenerative diseases,and these deserve further investigation.国家自然科学基金项目(30973150);国家重点基础研究发展计划(973)前期研究专项项目(2010CB535004);国家科技重大专项项目(2009ZX09103-731);福建省自然科学杰出青年基金项目(2009J06022

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies