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（amyloidplaques）。β-淀粉样蛋白前体蛋白（β-amyloidprocursorprotein,APP）经β-分泌酶和γ-分泌酶依次水解后产生AB和APP胞内结构域（APP intrace Uulardomain,AICD）。现在已经知道AB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。     

β淀粉样蛋白的分泌酶与阿尔采末病的治疗

β淀粉样蛋白(Aβ)级联反应在阿尔采末病(AD)发病过程中起主要作用,Aβ由分泌酶中的β和γ分泌酶水解β淀粉样蛋白前体蛋白(APP)而来。本文综述了参与APP水解的三种分泌酶(α、β和γ)的发现、研究进展及其在调节β淀粉样蛋白过程中的作用。选择性地激活α分泌薄或抑制β和γ分泌酶格减少Aβ产生,为AD治疗提供新的研究思路,以分泌酶为靶点可能成为治疗AD的理想途径。     

催化淀粉样蛋白产生的γ分泌酶的组装

γ分泌酶可引起多种膜蛋白的跨膜剪切作用,尤其可导致淀粉样前体蛋白（APP）的跨膜剪切,产生淀粉样蛋白（Aβ）。Aβ易发生沉积而诱发阿尔茨海默氏病（AD）。γ分泌酶由四种组分PS、Aph-1、NCT及Pen-2构成,由于该酶的相对分子质量巨大以及结构复杂,所以研究进展比较缓慢,其结构与功能至今仍未完全揭示。本文概述了在催化Aβ产生时γ分泌酶组装过程的研究进展,包括各组分之间的调控及组装。     

基于淀粉样蛋白级联假说的阿尔茨海默症防治研究进展

阿尔茨海默症（Alzheimer＇s Disease,AD）是一种中枢神经系统退行性病变,目前发病机制不清。淀粉样蛋白级联假说是有关AD发病机制的主流学说,认为脑内过量产生的β-淀粉样蛋白（β-amyloid peptide,Aβ）是引发AD的主要原因。针对Aβ的生成、聚集、清除及靶向治疗相关的药物开发是目前的研究热点,就淀粉样蛋白级联假说的最新研究进展及AD的预防治疗现状作一综述。     

Ca2＋失调与阿尔茨海默病发生发展关系的研究进展

阿尔茨海默病（Alzheimer’s disease,AD）是全球老年人中最常见的神经退行性疾病。在对家族性AD的动物模型和个别AD患者死后脑组织的研究中发现,除了A1342水平升高外,神经元内Ca2＋信号失调,并且Ca2＋信号蛋白表达水平也发生了改变。淀粉样蛋白斑、神经元纤维缠结和神经元丢失是AD的后期标志,它们的共同点可能是破坏神经元钙离子信号。细胞内钙离子水平提高在功能上与淀粉样蛋白斑、早老素突变、tau缠结和突触功能障碍相关,基于这些研究,产生了AD的Ca2＋假说。主要介绍神经元内Ca2＋失调与AD的关系以及钙拮抗剂作为AD的潜在治疗方法。     

囊泡谷氨酸转运体在阿尔兹海默病发病机制中的作用

阿尔兹海默病（Alzheimer’s disease,AD）是一种多因素复杂性神经退行性疾病,β淀粉样蛋白（pamyloid,AB）级联假说和谷氨酸兴奋性毒性是其重要的发病机制。囊泡谷氨酸转运体（vesicularglutamate transporters,VGLUTs）可特异性地将神经元内的谷氨酸转移入突触囊泡,且一个独立功能单位的VGLUT对于完成一个囊泡的填充是必要和充分的,没有VGLUT的突触囊泡中就没有谷氨酸（glutamate,Glul,VGLUT在一定程度上决定了释放进突触间隙Glu的量,是谷氨酸能突触传递的关键因子。在AD中Aβ增多聚集,VGLUTs表达减低,且VGLUTs转运Glu和Glu的囊泡释放与淀粉样前体蛋白（amyloid precursor protein,APP）代谢和A13的释放在突触囊泡的循环中存在行为平行性和共定位。胞外AB的增加可增强囊泡的释放几率,而Glu引起的突触活性增加亦可增加胞外A[3的浓度。APP／Aβ与谷氨酸能系统之间相互影响导致AD的发生,VGLUTs可能在其中发挥重要作用,被认为是治疗AD的潜在的药物靶点和预警标志物。     

雌激素对淀粉样β蛋白代谢的调节和毒性缓解

以淀粉样β蛋白为主的老年斑胞外沉积和神经元内神经原纤维缠结,是阿尔采末病(AD)特征性的病理学改变。近来,人们逐渐认可淀粉样蛋白假说,即认为淀粉样蛋白沉积是AD最初起因。研究人员正在寻找针对淀粉样β蛋白沉积的药物,雌激素是其中之一。初步的工作证明,雌激素能够调节淀粉样β蛋白前体代谢,减少淀粉样β蛋白生成,也能够减轻淀粉样B蛋白引起的免疫炎症反应、氧应激对细胞造成的损伤,和对抗细胞凋亡。     

老年痴呆症中神经递质释放异常的机理

阿尔茨海默症(Alzheimer’s disease,AD)是以胞外淀粉样蛋白(amyloid-β,Aβ)沉积和胞内神经纤维缠结为病理特征的神经退行性疾病。AD典型症状的出现与中枢神经系统突触数量的减少密切相关,因此,明确AD早期突触数量还没有明显降低时突触功能失调的机制对AD的临床诊治具有十分重要的意义。寡聚Aβ、早老素功能缺失等因素造成的突触前神经递质释放异常很有可能是AD突触功能异常的上游机制。对AD中神经递质释放异常的现象和机制进行综述,并对这一领域存在的开放问题作一归纳。     

Aβ对阿尔茨海默病影响机制的研究进展

阿尔茨海默病(Alzheimer's disease,AD)是一种以突触丢失、认知功能衰退和渐进性神经元死亡为特征的退行性神经系统疾病,主要临床表现为认知能力下降和行为障碍.在众多病因学说中,淀粉样蛋白斑块是AD病理的主要标志,在AD的发病过程中起着相当重要的作用.胞外β淀粉样蛋白(amyloid β-protein,...     

酶解淀粉样前体蛋白的β分泌酶研究进展

β淀粉样蛋白（β－Amyloid,Aβ）是阿尔茨海默症（Alzheimer’s disease,AD)病人脑中老年斑（senile plagues,SP)的主要成分。β分泌酶（β－secretase)是水解淀粉样前体蛋白（amyloid protein precursor,APP)产生β淀粉样蛋白所必须的。多年来众多科学家一直在寻找β分泌酶。最后三个研究组通过不同的研究途径各自独立发现了具有β分泌酶活性的酶,该酶很可能就是寻觅已久的β分泌酶。β分泌酶的发现不仅为药物设计提供了依据,而且为β淀粉样蛋白的生物学研究提供了线索。     

Calsyntenins Mediate TGN Exit of APP in a Kinesin-1-Dependent Manner

Kinesin motors are required for the export of membranous cargo from the trans-Golgi network (TGN), yet information about how kinesins are recruited to forming transport intermediates is sparse. Here we show that the Kinesin-1 docking protein calsyntenin-1 localizes to the TGN in vivo and directly and specifically recruits Kinesin-1 to Golgi/TGN membranes as well as to dynamic post-Golgi carriers. Overexpression of various calsyntenin chimeras and kinesin light chain 1 (KLC1) at high levels caused the formation of aberrant membrane stacks at the endoplasmic reticulum (ER) or the Golgi, disrupted overall Golgi structure and blocked exit of calsyntenin from the TGN. Intriguingly, this blockade of calsyntenin exit strongly and selectively impeded TGN exit of amyloid precursor protein (APP). Using live cell microscopy we found that calsyntenins exit the TGN in Kinesin-1-decorated tubular structures which may serve as carriers for calsyntenin-1-mediated post-TGN transport of APP. Abrogation of this pathway via virus-mediated knockdown of calsyntenin-1 expression in primary cultured neurons caused a marked elevation of APP C-terminal fragments. Together, these results indicate a role for calsyntenin-1 in Kinesin-1-dependent TGN exit and post-Golgi transport of APP-containing organelles and further suggest that distinct intracellular routes may exhibit different capacities for proteolytic processing of APP.     

Calsyntenins are secretory granule proteins in anterior pituitary gland and pancreatic islet alpha cells.

Calsyntenins are members of the cadherin superfamily of cell adhesion molecules. They are present in postsynaptic membranes of excitatory neurons and in vesicles in transit to neuronal growth cones. In the current study, calsyntenin-1 (CST-1) and calsyntenin-3 (CST-3) were identified by mass spectrometric analysis (LC-MS/MS) of integral membrane proteins from highly enriched secretory granule preparations from bovine anterior pituitary gland. Immunofluorescence microscopy on thin frozen sections of rat pituitary revealed that CST-1 was present only in gonadotropes where it colocalized with follicle-stimulating hormone in secretory granules. In contrast, CST-3 was present not only in gonadotrope secretory granules but also in those of somatotropes and thyrotropes. Neither protein was detected in mammatropes. In addition, CST-1 was also localized to the glucagon-containing secretory granules of alpha cells in the pancreatic islets of Langerhans. Results indicate that calsyntenins function outside the nervous system and potentially are modulators of endocrine function.     

Novel cadherin-related membrane proteins,Alcadeins, enhance the X11-like protein-mediated stabilization of amyloid beta-protein precursor metabolism

Previously we found that X11-like protein (X11L) associates with amyloid beta-protein precursor (APP). X11L stabilizes APP metabolism and suppresses the secretion of the amyloid beta-protein (Abeta) that are the pathogenic agents of Alzheimer's disease (AD). Here we found that Alcadein (Alc), a novel membrane protein family that contains cadherin motifs and originally reported as calsyntenins, also interacted with X11L. Alc was abundant in the brain and occurred in the same areas of the brain as X11L. X11L could simultaneously associate with APP and Alc, resulting in the formation of a tripartite complex in brain. The tripartite complex stabilized intracellular APP metabolism and enhanced the X11L-mediated suppression of Abeta secretion that is due to the retardation of intracellular APP maturation. X11L and Alc also formed another complex with C99, a carboxyl-terminal fragment of APP cleaved at the beta-site (CTFbeta). The formation of the Alc.X11L.C99 complex inhibited the interaction of C99 with presenilin, which strongly suppressed the gamma-cleavage of C99. In AD patient brains, Alc and APP were particularly colocalized in dystrophic neurites in senile plaques. Deficiencies in the X11L-mediated interaction between Alc and APP and/or CTFbeta enhanced the production of Abeta, which may be related to the development or progression of AD.     

Cross-talk of membrane lipids and Alzheimer-related proteins

Alzheimer’s disease (AD) is neuropathologically characterized by the combined occurrence of extracellular β-amyloid plaques and intracellular neurofibrillary tangles in the brain. While plaques contain aggregated forms of the amyloid β-peptide (Aβ), tangles are formed by fibrillar forms of the microtubule associated protein tau. All mutations identified so far to cause familial forms of early onset AD (FAD) are localized close to or within the Aβ domain of the amyloid precursor protein (APP) or in the presenilin proteins that are essential components of a protease complex involved in the generation of Aβ. Mutations in the tau gene are not associated with FAD, but can cause other forms of dementia. The genetics of FAD together with biochemical and cell biological data, led to the formulation of the amyloid hypothesis, stating that accumulation and aggregation of Aβ is the primary event in the pathogenesis of AD, while tau might mediate its toxicity and neurodegeneration.The generation of Aβ involves sequential proteolytic cleavages of the amyloid precursor protein (APP) by enzymes called β-and γ-secretases. Notably, APP itself as well as the secretases are integral membrane proteins. Thus, it is very likely that membrane lipids are involved in the regulation of subcellular transport, activity, and metabolism of AD related proteins.Indeed, several studies indicate that membrane lipids, including cholesterol and sphingolipids (SLs) affect Aβ generation and aggregation. Interestingly, APP and other AD associated proteins, including β-and γ-secretases can, in turn, influence lipid metabolic pathways. Here, we review the close connection of cellular lipid metabolism and AD associated proteins and discuss potential mechanisms that could contribute to initiation and progression of AD.     

细菌中钙信号的作用

摘要：越来越多的实验证明二价钙离子（Ca2+）在细菌中有重要调控作用。本文从Ca2+ 信号对细菌生理的影响、细胞内Ca2+ 浓度及测定方法、细菌中Ca2+ 的运输和Ca2+ 结合蛋白四个方面综述了目前细菌中钙信号的研究进展。     

血管紧张素Ⅱ增加新生鼠脑细胞胞浆Ca~(2+)浓度

本文应用荧光钙测定技术观察了血管紧张素Ⅱ(AⅡ)对新生Wistar鼠脑细胞胞浆Ca~(2+)浓度([Ca~(2+)]_i)的影响。结果表明:血管紧张素Ⅱ在1nmol/L—1μmol/L浓度下可诱导新生鼠脑细胞[Ca~(2+)]_i增加,具量效关系。在无外Ca~(2+)存在对,其增加幅度有所减少。上述效应可被血管紧张素Ⅱ拮抗剂Saralasin所阻断,并呈剂量依赖关系。上述结果提示,血管紧张素Ⅱ可激活血管紧张素AⅡ受体,增加脑细胞[Ca~(2+)]_i,该效应通过细胞内Ca~(2+)释放和细胞外Ca~(2+)内流两条适径实现,前者的作用是主要的。     

Coordinated metabolism of Alcadein and amyloid beta-protein precursor regulates FE65-dependent gene transactivation

The Alcadeins (Alcs)/calsyntenins and the amyloid beta-protein precursor (APP) associate with each other in the brain by binding via their cytoplasmic domains to X11L (the X11-like protein). We previously reported that the formation of this APP-X11L-Alc tripartite complex suppresses the metabolic cleavages of APP. We show here that the metabolism of the Alcs markedly resembles that of APP. The Alcs are subjected to a primary cleavage event that releases their extracellular domain. Alcs then undergo a secondary presenilin-dependent gamma-cleavage that leads to the secretion of the amyloid beta-protein-like peptide and the liberation of an intracellular domain fragment (AlcICD). However, when Alc is in the tripartite complex, it escapes from these cleavages, as does APP. We also found that AlcICD suppressed the FE65-dependent gene transactivation activity of the APP intracellular domain fragment, probably because AlcICD competes with the APP intracellular domain fragment for binding to FE65. We propose that the Alcs and APP are coordinately metabolized in neurons and that their cleaved cytoplasmic fragments are reciprocally involved in the regulation of FE65-dependent gene transactivation. Any imbalance in the metabolism of Alcs and APP may influence the FE65-dependent gene transactivation, which together with increased secretion of amyloid beta-protein may contribute to neural disorders.     

Molecular characterization of a trafficking organelle: dissecting the axonal paths of calsyntenin-1 transport vesicles

Kinesin motors play crucial roles in the delivery of membranous cargo to its destination and thus for the establishment and maintenance of cellular polarization. Recently, calsyntenin-1 was identified as a cargo-docking protein for Kinesin-1-mediated axonal transport of tubulovesicular organelles along axons of central nervous system neurons. To further define the function of calsyntenin-1, we immunoisolated calsyntenin-1 organelles from murine brain homogenates and determined their proteome by MS. We found that calsyntenin-1 organelles are endowed with components of the endosomal trafficking machinery and contained the β-amyloid precursor protein (APP). Detailed biochemical analyses of calsyntenin-1 immunoisolates in conjunction with immunocytochemical colocalization studies with cultured hippocampal neurons, using endosomal marker proteins for distinct subcompartments of the endosomal pathways, indicated that neuronal axons contain at least two distinct, nonoverlapping calsyntenin-1-containing transport packages: one characterized as early-endosomal, APP positive, the other as recycling-endosomal, APP negative. We postulate that calsyntenin-1 acts as a general mediator of anterograde axonal transportation of endosomal vesicles. In this role, calsyntenin-1 may actively contribute to axonal growth and pathfinding in the developing as well as to the maintenance of neuronal polarity in the adult nervous system; further, it may actively contribute to the stabilization of APP during its anterograde axonal trajectory.     

Molecular and cellular mechanisms for Alzheimer's disease: understanding APP metabolism

Alzheimer's disease (AD) is the most common neurodegenerative disease associated with aging. One important pathologic feature of AD is the formation of extracellular senile plaques in the brain, whose major components are small peptides called beta-amyloid (Abeta) that are derived from beta-amyloid precursor protein (APP) through sequential cleavages by beta-secretase and gamma-secretase. Because of the critical role of Abeta in the pathogenesis of AD, unraveling the cellular and molecular events underlying APP/Abeta metabolism has been and remains, of paramount importance to AD research. In this article we will focus on the regulation of APP metabolism leading to Abeta generation. We will review current knowledge of the secretases (alpha-, beta-, and gamma-secretases) involved in APP processing and various molecular and cellular mechanisms underlying intracellular trafficking of APP, which is a highly regulated process and whose disturbance has direct impacts on the production of Abeta.     

Neuronal and glial calcium signaling in Alzheimer's disease

Cognitive impairment and emotional disturbances in Alzheimer's disease (AD) result from the degeneration of synapses and death of neurons in the limbic system and associated regions of the cerebral cortex. An alteration in the proteolytic processing of the amyloid precursor protein (APP) results in increased production and accumulation of amyloid beta-peptide (Abeta) in the brain. Abeta has been shown to cause synaptic dysfunction and can render neurons vulnerable to excitotoxicity and apoptosis by a mechanism involving disruption of cellular calcium homeostasis. By inducing membrane lipid peroxidation and generation of the aldehyde 4-hydroxynonenal, Abeta impairs the function of membrane ion-motive ATPases and glucose and glutamate transporters, and can enhance calcium influx through voltage-dependent and ligand-gated calcium channels. Reduced levels of a secreted form of APP which normally regulates synaptic plasticity and cell survival may also promote disruption of synaptic calcium homeostasis in AD. Some cases of inherited AD are caused by mutations in presenilins 1 and 2 which perturb endoplasmic reticulum (ER) calcium homeostasis such that greater amounts of calcium are released upon stimulation, possibly as the result of alterations in IP(3) and ryanodine receptor channels, Ca(2+)-ATPases and the ER stress protein Herp. Abnormalities in calcium regulation in astrocytes, oligodendrocytes, and microglia have also been documented in studies of experimental models of AD, suggesting contributions of these alterations to neuronal dysfunction and cell death in AD. Collectively, the available data show that perturbed cellular calcium homeostasis plays a prominent role in the pathogenesis of AD, suggesting potential benefits of preventative and therapeutic strategies that stabilize cellular calcium homeostasis.