A new approach for developing a new drugs for alzheimer's disease (AD) and that for diagnosis for AD

由早老素2 （PS2）基因转录物外显子5跳变产生的异常剪接异构体（PS2V）是散发性阿尔茨海默病（AD）的诊断特征。我们发现PS2V在人神经母细胞瘤SK-N-SH细胞中是缺氧诱导的。我们根据它与外显子5片段的结合纯化了一个负责的反式作用因子。该因子被鉴定为高迁移率组A1a （HMGA1a）蛋白。HMGA1a与位于5'剪接位点上游的外显子5上的特定序列结合。缺氧诱导HMGA1a表达，并通过内源剪接因子SC35在核斑中积累。过表达HMGA1a可产生PS2V，但与与HMGA1a有强亲和力的U1 snRNP 70K蛋白共转染可抑制PS2V。HMGA1a可以干扰U1 snRNP与5'剪接位点的结合，导致5号外显子跳变。抑制HMGA1a与ps2外显子5的结合可抑制内质网应激引起的神经元死亡，提示开发一种新的阿尔茨海默病药物的可能性。此外，散发性AD患者脑组织中HMGA1a水平显著升高。此外，我们发现人类caspase- 4， caspase-1亚家族的成员，包括caspase-12，定位于内质网膜，当细胞被内质网应激诱导试剂处理时，被切割，而不是其他凋亡试剂。caspase-4的切割不受Bcl-2过表达的影响，而Bcl-2过表达会阻止线粒体的信号转导，这表明caspase-4主要在内质网应激诱导的细胞凋亡中被激活。此外，通过小干扰RNA降低caspase-4的表达可以减少一些细胞系内质网应激诱导的细胞凋亡，但对其他内质网应激无关的细胞凋亡没有影响。Caspase-4也可通过A β被切割，A β诱导的凋亡可通过干扰Caspase-4的小rna被减少。因此，caspase-4参与了AD的发病机制，抑制caspase-4可能会开发出治疗AD的新药。我们还发现散发性AD脑脊液中PS2V水平高于对照组，表明PS2V水平的改变对散发性AD的诊断有帮助

The aberrant splicing isoform (PS2V), generated by exon 5 skipping of the presenilin2 (PS2) gene transcript, is a diagnostic feature of sporadic Alzheimer's disease (AD). We found PS2V is hypoxia-inducible in human neuroblastoma SK-N-SH cells. We purified a responsible trans-acting factor based on its binding to an exon 5 fragment. The factor was identified as the high mobility group A1a (HMGA1a) protein. HMGA1a bound to a specific sequence on exon 5, located upstream of the 5' splice site. HMGA1a expression was induced by hypoxia and the protein was accumulated in the nuclear speckles with the endogenous splicing factor SC35. Overexpression of HMGA1a generated PS2V, but PS2V was repressed by cotransfection with the U1 snRNP 70K protein that has a strong affinity to HMGA1a. HMGA1a could interfere with U1 snRNP binding to the 5' splice site and caused exon 5 skipping. Inhibition of the binding of HMGA1a to PS2exon 5 inhibited the neuronal death caused by ER (endoplasmi reticulum) stress … More , suggesting the possibility to develop a new drug for AD. Furthermore, HMGA1a levels were significantly increased in the brain tissue from sporadic AD patients.In addition, we found that human cappase-4, a member of caspase-1 subfamily that includes caspase-12, is localized to the ER membrane, and is cleaved when cells are treated with ER stress-inducing reagents, but not other apoptotic reagents. Cleavage of caspase-4 is not affected by overexpression of Bcl-2, which prevents signal transduction on the mitochondria, suggesting that caspase-4 is primarily activated in ER stress-induced apoptosis. Furthermore, a reduction of caspase-4 expression by small interfering RNA decreases ER stress-induced apoptosis in some cell lines, but not other ER stress-independent apoptosis. Caspase-4 is also cleaved by administration of A β and A β-induced apoptosis is reduced by small interfering RNAs to caspase-4. Thus is involved in pathogenesis of AD, and inhibition of caspase-4 may leads to develop a new drug for AD.We also found the high level of PS2V in cerebrospinal fluid of sporadic AD comparing with that of control, showing that alteration of PS2V level is useful for diagnosis of sporadic AD Less