链脲佐菌素对大鼠海马p-CREB表达的影响及APP5肽类似物165的治疗作用

目的探讨链脲佐菌素(streptozotocin,STZ)对大鼠海马磷酸化环磷腺苷反应成分结合蛋白(phosphatedcylinc AMP response element binding protein,p-CREB)表达的影响以及APP5肽类似物165的治疗作用。方法将42只Wistar大鼠随机分为对照组、模型组和APP5肽类似物165治疗组。将STZ溶解于人工脑脊液,新鲜配制成浓度为25mg/mL,分别于第1、3天按体重3mg/kg行双侧脑室注射。APP5肽治疗组于3周后开始行APP5肽类似物165灌胃,连续4周。对照组和模型组则以等量生理盐水灌胃。4周后取脑组织海马行免疫组织化学染色和Western-blotting检测p-CREB。结果模型组p-CREB阳性神经细胞数(137.44±22.62)较对照组(27.33±9.91)明显增多(P<0.05),胞质淡染;APP5肽治疗组p-CREB阳性神经元数目(29.78±10.72)与对照组比较差异无统计学意义(P>0.05)。模型组海马p-CREB表达多于对照组和APP5肽治疗组,APP5肽治疗组与对照组接近。结论脑室注射小剂量STZ可使海马p-CREB阳性神经元表达增多,而APP5肽类似物165可使p-CREB阳性神经元表达恢复至正常水平。     

经颅磁刺激对脑梗死大鼠学习记忆与健侧海马锥体细胞树突和突触结构的影响

目的研究经颅磁刺激(TMS)对脑梗死后大鼠学习记忆功能,以及海马锥体细胞树突和突触结构的影响。方法将48只雄性SD大鼠随机分为正常组、模型组和TMS组,每组16只。采用线栓法对模型组和TMS组大鼠制作一侧大脑中动脉闭塞的脑梗死模型,并在制模后第2天,对TMS组给予每天2次、每次30个脉冲的TMS治疗,疗程4周;观察各组大鼠治疗后在Y-迷宫中的学习记忆成绩和梗死对侧海马锥体细胞树突和突触结构变化。结果(1)TMS组大鼠学习尝试次数[(18.4±4.8)次]少于模型组[(26.4±5.4)次;P<0.01],记忆再现次数[(6.1±1.3)次]多于模型组[(3.7±1.2)次;P<0.01];(2)TMS组海马CA3区锥体细胞树突顶树突总长度[(196±35)μm]长于模型组(175±33)μm;P<0.01]。(3)TMS组的突触后致密物质厚度[(68±11)nm]宽于模型组[(62±10)nm],穿孔性突触百分比(27.5%)高于模型组(10.0%),突触间隙[(16.7±1.8)nm]窄于模型组[(21.3±2.3)nm],均P<0.01和P<0.05。结论TMS能促进脑梗死大鼠学习记忆功能的恢复,其机制可能与海马锥体细胞树突和突触结构的改变有关。     

间歇性缺氧对大鼠认知功能和海马CA1区超微结构的影响

目的观察间歇性缺氧对大鼠认知功能及海马CA1区神经元超微结构的影响。方法SD雄性大鼠16只,随机分为正常组(UC,n=8)和间歇性缺氧组(IH,n=8)。UC组正常饲养,IH组每日间歇缺氧7 h建立间歇性缺氧大鼠模型,通过Morris水迷宫测试检测其学习和记忆能力,并于灌注固定后应用透射电镜观察海马CA1区超微结构。结果(1)Morris水迷宫学习成绩(定位航行实验):第5 d训练结束时IH组大鼠逃避潜伏期明显长于UC组,两组之间差异有统计学意义(P<0.05)。(2)Morris水迷宫记忆成绩:IH组穿越平台次数[(1.38±0.92)次]较UC组减少[(3.75±1.04)次](P<0.01);IH组跨越目标象限时间占整个游泳时间的百分率[(20.52±3.41)%]也较UC组减少[(39.89±5.63)%](P<0.01)。(3)电镜下可见IH组神经元细胞质的电子密度增加,核染色质浓缩并聚集核膜附近,粗面内质网排列紊乱或扩张并出现脱颗粒现象,线粒体主要表现为肿胀、空泡变性及嵴消失,突触结构分界不清,突触小泡稀疏。UC组无明显病变。结论IH可致大鼠学习记忆障碍和海马神经元超微结构改变,IH所引起的大鼠学习记忆障碍与海马神经元超微结构的改变密切相关。     

白桦脂醇对APP/PS1双转基因痴呆模型小鼠认知及海马突触功能相关蛋白表达的影响

目的 探讨白桦脂醇对阿尔茨海默病（AD）小鼠的学习记忆功能的干预作用及海马突触功能相关蛋白表达的影响，为探索治疗AD提供新的可能。方法 采用白桦脂醇干预APP/PS1双转基因痴呆模型小鼠，将小鼠随机分为模型组、药物高剂量组和低剂量组，C57BL/6J健康小鼠为对照组。通过行为学观察学习记忆能力、在体电生理记录海马神经元的生物电、TUNEL法检测神经元凋亡、Realtime PCR法检测PSD-95和Synapsin-I水平。结果 水迷宫检测结果发现白桦脂醇能改善模型小鼠认知功能障碍；电生理检测AD模型组长时程增强（LTP）幅值低于对照组，经过白桦脂醇干预治疗后，白桦脂醇各组LTP幅值较AD模型组升高；AD模型组神经元凋亡率显著高于对照组，经过白桦脂醇干预治疗后凋亡率下降；AD小鼠模型海马区PSD-95和Synapsin-I表达下降，但经白桦脂醇干预后其表达上升。结论 白桦脂醇通过使海马PSD-95和Synapsin-I的表达增加，发挥对APP/PS1双转基因痴呆模型小鼠认知功能的保护，使海马长时程增强。     

碱性成纤维细胞生长因子改善血管性痴呆小鼠学习记忆功能：与清除氧自由基有关？

背景：血管性痴呆（Vascular Dementia,VD）是由一系列脑血管因素导致脑组织损害引起的痴呆综合征,患者表现为学习、记忆等功能障碍。bFGF具有神经保护功能。 目的: 研究拟血管性痴呆模型小鼠学习记忆功能的改变及bFGF的治疗作用。 设计、时间及地点: 随机对照动物实验,于2008-03/12在北华大学医学院完成。 材料: 昆明种小鼠60只,体重(30.0±3.12g),♀♂兼用,随机分成4组：正常组、假手术组、模型组、bFGF治疗组（bFGF组）。 方法：采用清醒小鼠反复脑缺血再灌注方法建立VD动物模型。假手术组只分离双侧颈总动脉,不阻断血流。正常组不做任何处理。bFGF组于手术后首次即刻给药,正常组、假手术组、模型组给予等体积生理盐水腹腔注射。 主要观察指标: 应用Morris水迷宫观察bFGF对血管性痴呆小鼠学习记忆的改善作用;尼氏染色观察病理形态学变化;生化分析方法检测脑组织中SOD、MDA的含量;应用Annexin V-F1TC /PI双标记流式细胞术检测海马神经元的凋亡情况。 结果: 与正常组比较,水迷宫实验显示模型组小鼠学习记忆功能明显下降,表现为潜伏期延长、穿越有效区的时间缩短、穿越平台的次数减少（P<0.01,P<0.05）。生化指标显示模型小鼠脑组织SOD的活性下降,MDA 的含量增加（P<0.01）;流式细胞术检测结果显示海马神经元凋亡率显著增加（P<0.01）。与模型组比较,bFGF能够改善小鼠的学习记忆能力,增加SOD活力降低MDA含量（P<0.01）,降低海马神经元的凋亡率（P<0.01）。 结论:（1）清醒小鼠反复脑缺血再灌注引起的学习记忆障碍的动物模型具有较好的仿真VD的特点。（2）bFGF对VD小鼠的学习记忆功能障碍具有一定的改善作用。其机制可能与改善自由基代谢和脂质过氧化反应抑制神经细胞凋亡有关。     

复智散对神经细胞凋亡的影响

目的应用Aβ25～35孵育SH-SY5Y神经母细胞瘤株制作细胞损伤模型,以研究复智散对Aβ25～35细胞损伤模型凋亡相关指标的影响。方法将制备好的SH-SY5Y细胞分为正常对照组、单纯应用复智散孵育组、Aβ25～35细胞损伤模型组、复智散与Aβ25～35共同孵育SH-SY5Y细胞组。采用异硫氰酸荧光素(fluoresceinisothiocyanate,FITC)标记的AnnexinⅤ及碘化丙锭双染流式细胞技术检测各组细胞的凋亡率,并利用荧光探针JC-1测定线粒体膜电位,统计分析不同组间神经细胞凋亡率及线粒体膜电位的变化情况,以确认药物的保护作用。结果单纯应用复智散孵育组神经细胞凋亡率及线粒体膜电位的变化与正常对照组相比,差异无显著性意义(P>0.05);Aβ25～35细胞损伤模型组培养的SH-SY5Y细胞线粒体膜电位下降,凋亡率增高(P<0.05);复智散与Aβ25～35共同孵育组神经细胞线粒体膜电位上调,细胞凋亡率降低,提示复智散对培养的SH-SY5Y细胞具有保护作用。结论复智散可拮抗Aβ25～35降低培养神经细胞线粒体膜电位、增加凋亡率的不良效应,具有神经细胞保护功能。     

线粒体通透性转换孔在缺血预处理脑保护中的作用及机制

目的观察线粒体通透性转换孔(mitochondrial permeability transition pore,MPTP)在缺血再灌注及缺血预处理脑保护中的作用。方法将体外培养8 d的海马神经元分为五组,正常对照组(A组),缺血再灌注组(B组),缺血预处理+缺血再灌注组(C组),苍术苷+缺血再灌注组(D组),缺血预处理+苍术苷+缺血再灌注组(E组)。使用流式细胞术检测各组细胞凋亡率,罗丹明123染色流式细胞术检测线粒体膜电位,Western-blot检测Bcl-2,Bax的表达水平。结果与A组比较,其余四组线粒体膜电位均降低,神经元凋亡率升高(P<0.05);与B组比较,C组线粒体膜电位升高,神经元凋亡率升高,Bcl-2表达上调,Bax表达下调(P<0.05);与C组比较,E组粒体膜电位降低,神经元凋亡率升高,Bcl-2表达下调,Bax表达上调(P<0.05)。结论缺血预处理能有效减轻海马神经元缺血再灌注损伤,抑制缺血再灌注后神经细胞凋亡,其机制可能与抑制MPTP的开放有关。     

低频脉冲磁场对脑缺血再灌注损伤大鼠神经元保护作用的研究

目的研究低频脉冲磁场对脑缺血再灌注损伤大鼠海马神经元的保护作用。方法将24只SD大鼠随机分成磁辐射组和对照组(每组12只),应用改良的Pulsineli法制作大鼠全脑缺血再灌注模型;将磁辐射组大鼠头部置于低频脉冲磁场(20mT、10Hz)辐射45min,每天1次,连续4d。进行脑电图监测,用Nissl染色及免疫组化方法检测海马神经元数及caspase-3蛋白阳性细胞数。结果磁辐射组脑电图振幅[(10.27±1.12)μV]和频率[(10.06±1.02)Hz]较对照组[(8.95±1.04)μV、(8.62±0.94)Hz]显著增加(均P<0.05);磁辐射组海马神经元数[(29.02±1.32)个/高倍镜视野]较对照组[(21.25±1.06)个/高倍镜视野]增多,磁辐射组caspase-3蛋白阳性细胞数[(21.33±1.32)个/高倍镜视野]较对照组[(28.34±1.10)个/高倍镜视野]减少,两组相比差异具有统计学意义(均P<0.05)。结论低频脉冲磁场可以减轻脑缺血再灌注后海马神经元的损伤及凋亡,对脑缺血再灌注损伤有保护作用。     

姜黄素对AD小鼠海马神经元凋亡和GSK-3β表达及磷酸化的影响

目的观察姜黄素对AD小鼠模型海马神经元凋亡和糖原合成酶激酶3β表达及其磷酸化影响。方法将20只APP/PS1转基因小鼠随机分为AD模型组、AD模型+姜黄素组,每组10只,AD模型+姜黄素组腹腔注射剂量为400mg/(kg·d)姜黄素,1次/d,连续14d。取12只正常小鼠作对照组。采用扫描电镜检测小鼠海马神经元凋亡,Western blot检测GSK-3β、酪氨酸磷酸化GSK-3β(pTyr-GSK-3β)和丝氨酸磷酸化GSK-3β(pSer-GSK-3β)的表达情况。结果与对照组相比,模型组海马神经元出现染色质边集、线粒体肿胀、细胞器减少;pTyr-GSK-3β和pSer-GSK-3β的表达明显增加(t=5.112,P=0.005;t=5.619,P=0.006)。与模型组相比,姜黄素组海马神经元染色质呈弥散分布、线粒体嵴清晰可见、细胞器排列紧密,pTyr-GSK-3β表达明显降低(t=-7.985,P=0.001),pSer-GSK-3β表达明显提高(t=9.105,P=0.001)。结论 GSK-3β可能参与AD小鼠海马神经元损伤,姜黄素通过减少pTyr-GSK-3β、增加pSer-GSK-3β的表达抑制GSK-3β活性来减少AD小鼠海马神经元凋亡。     

α7神经型尼古丁受体激动剂PNU282987对APP/PS1小鼠海马组织中AP180蛋白表达的影响

目的探讨特异性激动APP/PS1转基因小鼠中的α7nAChR后其海马组织中突触后膜蛋白的表达变化。方法选择16只经过鉴定的APP/PS1小鼠随机分为APP/PS1组(APP/PS1)和APP/PS1+PNU282987组(AP),每组各8只;另选16只野生型小鼠随机分为对照组(Control)和野生+PNU282987组(WP),每组各8只。饲养小鼠达到24周龄后,AP组和WP组于每天进行Morris水迷宫行为学测试前4 h腹腔注射PNU282987(1 mg/kg/d),之后利用Morris水迷宫进行行为学测试,Real-time PCR及Western blotting法分别检测各组小鼠海马组织中AP180 mRNA及蛋白水平的表达情况。结果与对照组比较,APP/PS1组海马组织中AP180 mRNA及蛋白表达水平明显降低(P0.01,P0.01);而特异性激动α7 nAChR水平后,WP组中AP180 mRNA和蛋白水平升高(P0.01,P0.05);与APP/PS1组相比AP组小鼠大脑海马组织中AP180 mRNA和蛋白水平明显升高(P0.01,P0.01)。结论特异性激动APP/PS1转基因小鼠海马组织中α7 nAChR能够使网格蛋白介导的突触囊泡内吞过程中的关键蛋白AP180表达水平升高。这可能提示了α7nAChR对突触有一定的保护作用,进一步说明α7nAChR在阿尔茨海默病的发病中起着重要作用。     

FBL2 regulates amyloid precursor protein (APP) metabolism by promoting ubiquitination-dependent APP degradation and inhibition of APP endocytosis

The ubiquitin-proteasome pathway is a major protein degradation pathway whose dysfunction is now widely accepted as a cause of neurodegenerative diseases, including Alzheimer's disease. Here we demonstrate that the F-box and leucine rich repeat protein2 (FBL2), a component of the E3 ubiquitin ligase complex, regulates amyloid precursor protein (APP) metabolism through APP ubiquitination. FBL2 overexpression decreased the amount of secreted amyloid β (Aβ) peptides and sAPPβ, whereas FBL2 mRNA knockdown by siRNA increased these levels. FBL2 overexpression also decreased the amount of intracellular Aβ in Neuro2a cells stably expressing APP with Swedish mutation. FBL2 bound with APP specifically at its C-terminal fragment (CTF), which promoted APP/CTF ubiquitination. FBL2 overexpression also accelerated APP proteasome-dependent degradation and decreased APP protein localization in lipid rafts by inhibiting endocytosis. These effects were not observed in an F-box-deleted FBL2 mutant that does not participate in the E3 ubiquitin ligase complex. Furthermore, a reduced insoluble Aβ and Aβ plaque burden was observed in the hippocampus of 7-month-old FBL2 transgenic mice crossed with double-transgenic mice harboring APPswe and PS1(M146V) transgenes. These findings indicate that FBL2 is a novel and dual regulator of APP metabolism through FBL2-dependent ubiquitination of APP.     

Lentivirus-mediated APP695-RNAi reduces apoptosis in APP transgenic mouse neurons

Amyloid-β peptide (Aβ) is a cleavage product of the amyloid precursor protein (APP), which is thought to be important in the pathogenesis of Alzheimer's disease (AD). Recent evidence suggests that Aβ induces neuronal apoptosis in the brain and in primary neuronal cultures. If decreased Aβ whether could reduce the neuronal apoptosis? In this study, APP695-siRNA was delivered to hippocampal and cortical neurons of APP695 transgenic mice (AD model) in vitro using a recombinant lentivirus vector. The results show that lentivirus-mediated RNA interference of the APP695 gene could reduce neuronal apoptosis, possibly through the reduction of caspase-3 activity and the neuronal apoptosis pathway. These results suggest that lentivirus-mediated RNA interference may be a potential therapeutic for AD.     

Mapping the APP/presenilin (PS) binding domains: the hydrophilic N-terminus of PS2 is sufficient for interaction with APP and can displace APP/PS1 interaction

Mutations in presenilin 1 and presenilin 2 (PS1 and PS2, respectively) genes cause the large majority of familial forms of early-onset Alzheimer's disease. The physical interaction between presenilins and APP has been recently described using coimmunoprecipitation. With a similar technique, we confirmed this interaction and have mapped the interaction domains on both PS2 and APP. Using several carboxy-terminal truncated forms of PS2, we demonstrated that the hydrophilic amino terminus of PS2 (residues 1 to 87, PS2NT) was sufficient for interaction with APP. Interestingly, only a construct with a leader peptide for secretion (SecPS2NT) and not its cytosolic counterpart was shown to interact with APP. For APP, we could demonstrate interaction of PS2 with the last 100 but not the last 45 amino acids of APP, including therefore the A beta region. Accordingly, SecPS2NT is capable of binding to A beta-immunoreactive species in conditioned medium. In addition, a second region in the extracellular domain of APP also interacted with PS2. Comparable results with PS1 indicate that the two presenilins share similar determinants of binding to APP. Confirming these results, SecPS2NT is able to inhibit PS1/APP interaction. Such a competition makes it unlikely that the PS/APP interaction results from nonspecific aggregation of PS in transfected cells. The physical interaction of presenilins with a region encompassing the A beta sequence of APP could be causally related to the misprocessing of APP and the production of A beta1-42.     

The upside of APP at synapses

The memory dysfunctions that characterize Alzheimer's disease (AD) are strongly correlated with synapse loss. The amyloid precursor protein (APP) and its cleavage product Aβ play central roles in synapse and memory loss, and thus are strongly implicated in the pathogenesis of AD. Numerous in vitro and transgenic AD mouse model studies have shown that overexpression of APP leads to Aβ accumulation, which causes decreased synaptic activity and dendritic spine density. However, the normal synaptic function of APP itself is not fully understood. Several recent studies have found that full-length APP promotes synaptic activity, synapse formation, and dendritic spine formation. These findings cast APP as a potential key player in learning and memory. It is of interest that the synaptic functions of full-length APP are opposite to the effects associated with pathological Aβ accumulation. In this review, we will summarize the normal functions of APP at synapses and spines along with other known functions of APP, including its role in cell motility, neuronal migration, and neurite outgrowth. These studies shed light on the physiological actions of APP, independent of Aβ effects, and thus lead to a better understanding of the synaptic dysfunctions associated with AD.     

APP involvement in retinogenesis of mice

Very few studies have examined expression and function of amyloid precursor protein (APP) in the retina. We showed that APP mRNA and protein are expressed according to the different waves of retinal differentiation. Depletion of App led to an absence of amacrine cells, a 50% increase in the number of horizontal cells and alteration of the synapses. The retinas of adult APP(-/-) mice showed only half as many glycinergic amacrine cells as wild-type retinas. We identified Ptf1a, which plays a role in controlling both amacrine and horizontal cell fates, as a downstream effector of APP. The observation of a similar phenotype in sorLA knockout mice, a major regulator of APP processing, suggests that regulation of APP functions via sorLA controls the determination of amacrine and horizontal cell fate. These findings provide novel insights that indicate that APP plays an important role in retinal differentiation.     

Amyloid beta-protein precursor (APP) of cultured cells: secretory and non-secretory forms of APP

Overproduction or aberrant catabolism of the predicted amyloid beta-protein precursor (APP) is suspected as the cause of amyloid deposition in Alzheimer's disease and Down's syndrome brains. For possible in vitro experiments of amyloid formation, we have examined the expression of APP in various cultured cells. We found two types of APP producing cell lines. PC12h (rat pheochromocytoma) and HL-60 (human acute promyelocytic leukemia) cells produce a secretory form that is released into the culture medium, while Bu-17 (human glioma) cells synthesize only a non-secretory form that accumulates at the cell surface. APP immunoreactivity on the latter cells was detected at the tips of cell processes or growth cones. These observations indicate that the nonsecretory form of APP may play a role in cell contact or adhesion.     

Fimbria-fornix lesion does not affect APP levels and amyloid deposition in the hippocampus of APP+PS1 double transgenic mice

The deposition of amyloid beta peptides (Abeta) and cholinergic dysfunction are two characteristic features of Alzheimer's disease. Several studies have suggested that a compromised cholinergic transmission can increase the amount of amyloid precursor protein (APP) in the denervated cortex (or hippocampus); however, whether this will increase Abeta production is unknown. To investigate the relation between cholinergic neurotransmission and APP metabolism, and the possible role of cholinergic dysfunction in the development of amyloid neuropathology, we lesioned the fimbria-fornix pathway in APP+PS1 double transgenic mice, at 5 and 7 months of age. Three months and 11 months postlesion, the mice were sacrificed for biochemical and histopathological analyses. The fimbria-fornix transection resulted in a substantial depletion of cholinergic markers in the hippocampus at both time points. Three months postlesion, hippocampal APP and Abeta levels were not significantly changed. At 11 months postlesion, the fimbria-fornix lesion did not result in an alteration in either the hippocampal Abeta levels or the extent of Abeta deposition, as assessed by amyloid plaque counts and image analysis of Abeta load in the 18-month-old APP+PS1 mice. Our findings indicate that APP metabolism in mice may be dissociated from cholinergic neurotransmission rather than related as previously suggested in other mammalian species.     

Arsenic affects expression and processing of amyloid precursor protein (APP) in primary neuronal cells overexpressing the Swedish mutation of human APP

Arsenic poisoning due to contaminated water and soil, mining waste, glass manufacture, select agrochemicals, as well as sea food, affects millions of people world wide. Recently, an involvement of arsenic in Alzheimer's disease (AD) has been hypothesized (Gong and O’Bryant, 2010). The present study stresses the hypothesis whether sodium arsenite, and its main metabolite, dimethylarsinic acid (DMA), may affect expression and processing of the amyloid precursor protein (APP), using the cholinergic cell line SN56.B5.G4 and primary neuronal cells overexpressing the Swedish mutation of APP, as experimental approaches.Exposure of cholinergic SN56.B5.G4 cells with either sodium arsenite or DMA decreased cell viability in a concentration- and exposure-time dependent manner, and affected the activities of the cholinergic enzymes acetylcholinesterase and choline acetyltransferase. Both sodium arsenite and DMA exposure of SN56.B5.G4 cells resulted in enhanced level of APP, and sAPP in the membrane and cytosolic fractions, respectively. To reveal any effect of arsenic on APP processing, the amounts of APP cleavage products, sAPPβ, and β-amyloid (Aβ) peptides, released into the culture medium of primary neuronal cells derived from transgenic Tg2576 mice, were assessed by ELISA. Following exposure of neuronal cells by sodium arsenite for 12 h, the membrane-bound APP level was enhanced, the amount of sAPPβ released into the culture medium was slightly higher, while the levels of Aβ peptides in the culture medium were considerably lower as compared to that assayed in the absence of any drug. The sodium arsenite-induced reduction of Aβ formation suggests an inhibition of the APP γ-cleavage step by arsenite. In contrast, DMA exposure of neuronal cells considerably increased formation of Aβ and sAPPβ, accompanied by enhanced membrane APP level. The DMA-induced changes in APP processing may be the result of the enhanced APP expression. Alternatively, increased Aβ production may also be due to stimulation of caspase activity by arsenic compounds, or failure in Aβ degradation.In summary, the present report clearly demonstrates that sodium arsenite and DMA affect processing of APP in vitro.     

Retromer disruption promotes amyloidogenic APP processing

Retromer deficiency has been implicated in sporadic AD and animals deficient in retromer components exhibit pronounced neurodegeneration. Because retromer performs retrograde transport from the endosome to the Golgi apparatus and neuronal Aβ is found in late endosomal compartments, we speculated that retromer malfunction might enhance amyloidogenic APP processing by promoting interactions between APP and secretase enzymes in late endosomes. We have evaluated changes in amyloid precursor protein (APP) processing and trafficking as a result of disrupted retromer activity by knockdown of Vps35, a vacuolar sorting protein that is an essential component of the retromer complex. Knocking down retromer activity produced no change in the quantity or cellular distribution of total cellular APP and had no affect on internalization of cell-surface APP. Retromer deficiency did, however, increase the ratio of secreted Aβ42:Aβ40 in HEK-293 cells over-expressing APP695, due primarily to a decrease in Aβ40 secretion. Recent studies suggest that the retromer-trafficked protein, Wntless, is secreted at the synapse in exosome vesicles and that these same vesicles contain Aβ. We therefore hypothesized that retromer deficiency may be associated with altered exosomal secretion of APP and/or secretase fragments. Holo-APP, Presenilin and APP C-terminal fragments were detected in exosomal vesicles secreted from HEK-293 cells. Levels of total APP C-terminal fragments were significantly increased in exosomes secreted by retromer deficient cells. These data suggest that reduced retromer activity can mimic the effects of familial AD Presenilin mutations on APP processing and promote export of amyloidogenic APP derivatives.