Two memory associated genes regulated by amyloid precursor protein intracellular domain Novel insights into the pathogenesis of learning and memory impairment in Alzheimer's disease

In this study, we employed chromatin immunoprecipitation, a useful method for studying the locations of transcription factors bound to specific DNA regions in specific cells, to investigate amyloid precursor protein intracellular domain binding sites in chromatin DNA from hippocampal neurons of rats, and to screen out five putative genes associated with the learning and memory functions. The promoter regions of the calcium/calmodulin-dependent protein kinase II alpha and glutamate receptor-2 genes were amplified by PCR from DNA products immunoprecipitated by amyloid precursor protein intracellular domain. An electrophoretic mobility shift assay and western blot analysis suggested that the promoter regions of these two genes associated with learning and memory were bound by amyloid precursor protein intracellular domain （in complex form）. Our experimental findings indicate that the amyloid precursor protein intracellular domain is involved in the transcriptional regulation of learning- and memory-associated genes in hippocampal neurons. These data may provide new insights into the molecular mechanism underlying the symptoms of progressive memory loss in Alzheimer＇s disease.

Physiological effects of amyloid precursor protein and its derivatives on neural stem cell biology and signaling pathways involved

The pathological implication of amyloid precursor protein(APP)in Alzheimer’s disease has been widely documented due to its involvement in the generation of amyloid-β peptide.However,the physiological functions of APP are still poorly understood.APP is considered a multimodal protein due to its role in a wide variety of processes,both in the embryo and in the adult brain.Specifically,APP seems to play a key role in the proliferation,differentiation and maturation of neural stem cells.In addition,APP can be processed through two canonical processing pathways,generating different functionally active fragments:soluble APP-α,soluble APP-β,amyloid-β peptide and the APP intracellular C-terminal domain.These fragments also appear to modulate various functions in neural stem cells,including the processes of proliferation,neurogenesis,gliogenesis or cell death.However,the molecular mechanisms involved in these effects are still unclear.In this review,we summarize the physiological functions of APP and its main proteolytic derivatives in neural stem cells,as well as the possible signaling pathways that could be implicated in these effects.The knowledge of these functions and signaling pathways involved in the onset or during the development of Alzheimer’s disease is essential to advance the understanding of the pathogenesis of Alzheimer’s disease,and in the search for potential therapeutic targets.

Novel Adaptors of Amyloid Precursor Protein Intracellular Domain and Their Functional Implications

Amyloid precursor protein intracellular domain （AICD） is one of the potential candidates in deciphering the complexity of Alzheimer＇s disease. It plays important roles in determining cell fate and neurodegeneration through its interactions with several adaptors. The pres- ence or absence of phosphorylation at specific sites determines the choice of partners. In this study, we identified 20 novel AICD- interacting proteins by in vitro pull down experiments followed by 2D gel electrophoresis and MALDI-MS analysis. The identified proteins can be grouped into different functional classes including molecular chaperones, structural proteins, signaling and transport molecules, adaptors, motor proteins and apoptosis determinants. Interactions of nine proteins were further validated either by colocal- ization using confocal imaging or by co-immunoprecipitation followed by immunoblotting. The cellular functions of most of the proteins can be correlated with AD. Hence, illustration of their interactions with AICD may shed some light on the disease pathophysiology.

淀粉样前体蛋白胞内结构域对阿尔茨海默病模型小鼠神经发生和学习记忆的影响

【目的】探讨淀粉样前体蛋白胞内结构域(AICD)对阿尔茨海默病(AD)模型动物神经发生、学习记忆的影响。【方法】本研究使用免疫荧光染色检测AICD转基因小鼠来源的体外培养的神经前体细胞(NPCs)、胚胎大脑皮质、成年海马齿状回(DG)中增殖和分化的细胞数目;水迷宫实验检测老年AICD转基因小鼠对学习记忆能力影响;生物信息学预测和分析潜在的分子机制。【结果】免疫荧光染色结果显示AICD转基因模型体外NPCs、胚胎皮质、海马DG区域的神经干细胞和神经元数量减少(P<0.05),即AICD抑制不同时期AD模型小鼠的神经发生。水迷宫结果显示AICD增加AD模型小鼠逃逸潜伏期,减少其跨越平台次数,并减少DG区域神经元数目(P<0.05)。生物信息学结果显示,AICD参与调节AD发病进程中神经发生和学习记忆的靶点有1723个,关键靶点有TP53、CTNNB1、Akt1、EGFR、SRC、EP300、HDAC1、STAT3、HSP90AA1和MAPK1;另外,KEGG通路注释分析发现PI3KAkt、HIF-1等信号通路在AICD调节神经发生和学习记忆起关键作用。【结论】表明AICD可以抑制AD模型小鼠海马神经发生进而损害学习记忆能力,这可能与PI3K-Akt和HIF-1等信号通路有关。本研究为进一步理解AICD在AD发病进程中作用提供实验依据。

β-淀粉样蛋白前体蛋白胞内结构域(AICD)研究进展

老年性痴呆症(Alzheimer's disease,AD)一个重要的病理学特征,是在神经细胞外形成由β-淀粉样蛋白(β-amyloid,Aβ)组成的淀粉样斑(amyloid plaques)。β-淀粉样蛋白前体蛋白(β-amyloid procursor protein,APP)经β-分泌酶和γ-分泌酶依次水解后产生Aβ和APP胞内结构域(APP intracellular domain,AICD)。现在已经知道Aβ在AD的发病机制中起着关键作用,但是关于AICD的生理及病理功能还不清楚。近年来研究发现AICD可以与细胞内多种蛋白相互作用,而且AICD在基因转录、细胞凋亡以及APP的加工和运输过程中均有调节功能。本文针对这一领域的研究进展,对AICD的生理及病理功能进行探讨。

淀粉样前体蛋白胞内域的功能和机制

Alzheimer's disease (AD),a degenerative neurological disorder,is the most common form of dementia among older people,whose symptoms include gradual memory loss,cognitive impairments and deterioration of language skills.Amyloid precursor protein (APP) is cleaved by serials of secretases and generates Aβ,sAPPα/β and APP intracellular domain (AICD).Aβ forms amyloid plaques,together with neurofibrillary tangles (NFTs) which is comprised with hyperphosphorylated tau,are hallmarks ofAD.Aβ,especially in its oligomeric form,plays important roles in AD,causing cell death,calcium influx,loss of spines and repression of long-term potentiation (LTP)[1].However,recent studies indicate that in addition to Aβ,other fragments of APP after its cleavage,such as AICD,play essential roles in AD as well.In this article,the function of AICD and its underlying mechanisms will be reviewed.