即将碰撞时间的视觉信息加工研究进展

当物体迫近观察者或观察者迫近物体时,观察者(人或动物)利用何种视觉线索成功地实现躲避行为或截取行为?已有研究显示物体在观察者视网膜上视像均匀扩大的速率(Tau线索)可直接为人或动物提供即将碰撞时间信息,从而使得观察者可以直接指挥肢体,做出反应。本综述从行为学和认知神经基础上总结了支持Tau线索的证据,并对今后关于即将碰撞时间估计视觉线索研究趋势提出建议。     

运动与阿尔茨海默病：基于Tau蛋白翻译后修饰视角的研究述评

阿尔茨海默病（Alzheimer’s disease,AD）是一种与年龄有关的神经退行性疾病,严重危害老年人的身心健康,给社会带来巨大的经济压力。但目前其发病机制尚不完全明确,临床仍无根治的有效方法。Tau蛋白是一种微管相关蛋白质,能够参与维持微管相关结构稳定,具有可溶性且不会聚集。在AD病理状态下,病人脑内Tau蛋白结构和功能异常。异常的Tau蛋白聚集成不可溶的神经纤维缠结,损害微管运输能力,导致病人认知功能障碍。Tau蛋白结构和功能的改变是由多种翻译后修饰过程来调控的,即将特定的化学修饰基团与Tau蛋白N-端或C-端结合,直接改变蛋白质的性质和功能。AD病人脑内Tau蛋白的磷酸化、糖基化、乙酰化及SUMO化等多种翻译后修饰异常,与Tau蛋白的降解和毒性物质的聚集密切相关。本文综述近年来的研究后发现,运动可以通过改善Tau蛋白翻译后的某些异常修饰来预防和改善AD,主要作用方式如下：(1）运动可通过抑制GSK 3β和MAPK等蛋白激酶活性来抑制Tau蛋白的过度磷酸化,可能通过上调PP2A活性来促进Tau蛋白去磷酸化;(2）运动可通过提高GLUT1和GLUT3蛋白质水平,可能通过调节OGA和OGT活性平衡,提高蛋白质O-GlcNAc糖基化水平;(3）运动可能通过AMPK/mTORC1途径抑制p300以及激活SIRT1,降低Tau蛋白乙酰化水平;同时运动还可能通过抑制HDAC6,改善Tau蛋白KXGS基序异常乙酰化程度;(4）运动可能通过调节磷酸化与SUMO化共定位点,改善Tau蛋白异常SUMO化水平。     

Tau蛋白高度磷酸化致阿尔茨海默病动物模型研究进展

阿尔茨海默病（Alzheimer＇sdisease,AD）是老年人中最常见的神经退行性疾病,以过度磷酸化tau蛋白为核心形成的神经原纤维缠结为AD的主要病理特征之一。近年来对tau蛋白磷酸化的研究备受关注。在AD的实验研究中,探索理想的AD动物模型对于明确AD的病因、发病机制及药物的研发等方面起关键作用。本文对Tau蛋白磷酸化致AD主要动物模型的研究进展进行了综述,包括Tau转基因动物模型、激酶和磷酸化酶系统失衡致Tau蛋白过度磷酸化损伤模型、降低Tau蛋白糖基化致Tau过度磷酸化模型等。     

蟾蜍视觉的识别实验探究

研究动物的行为反应是神经生理学的基础,采用神经系统较为简单的低等动物（如两栖类动物等）来研究视觉形成与背景之间的关系,特别是探讨一些与视觉反应有关的神经生理基础就成为入手之处．简单描述了研究蟾蜍视觉形成与背景关系的实验方法,通过使用示波器记录了蟾蜍视觉中枢（视顶盖）与所视目标之间的电生理活动。     

人源Tau蛋白截短片段转基因果蝇模型的建立

人Tau蛋白是一种主要的细胞骨架蛋白,由Tau蛋白组成的神经纤维缠结是阿尔茨海默病的两大病理特征之一,C末端缺失的Tau已经证实是神经纤维缠结的组份之一,体内体外实验已经证实,Tau蛋白可以是多种蛋白酶的水解底物。但是,Tau蛋白水解产生的截短片段在阿尔茨海默病中的作用目前还不清楚。为了能够在在体水平研究Tau蛋白截短片段的毒性机制,将Tau蛋白截短成不同的截短片段:Tau1-44、Tau45-441、Tau45-230、Tau231-441。利用显微注射的方法构建Tau基因截短片段的转基因果蝇,并利用果蝇中的UAS/GAL4系统驱动截短的Tau蛋白片段在果蝇的眼睛中异位表达,该实验结果发现在果蝇眼睛中过表达Tau蛋白截短片段并没有对果蝇眼睛的发育造成明显的毒性,从而推断Tau蛋白水解是机体的一种自我保护机制。     

骨髓间充质干细胞向神经细胞分化中Tau蛋白的表达

目的：观察骨髓间充质干细胞（MSCs）分化为神经细胞过程中,神经元微管相关蛋白Tau及其磷酸化位点pSer202的表达和含量的差异,探讨Tau蛋白在此过程中的作用。方法：使用EGF和bFGF联合诱导第4、第8和第12代的MSCs向神经细胞分化;14d后,免疫细胞化学法检测Tau蛋白和pSer202的表达;ELISA法分析各代细胞Tau蛋白含量。结果：第4、第8和第12代未诱导组Tau蛋白阳性细胞均〈6％;诱导14d后,各代MSCs在形态上均分化为类似神经元样细胞,Tau蛋白阳性细胞率较未诱导组显著升高（P〈0．05）,但各代之间无显著性,而pSer202在各代MSCs未诱导组和诱导组中均未见表达。ELISA法检测发现Tau蛋白含量在诱导过程中呈上升趋势,14d时各代细胞分化后的Tau蛋白升高程度无显著性差异。结论：MSCs向神经细胞分化过程中Tau蛋白表达量增加且可能尚未发生磷酸化,将有助于神经细胞的正常分化和突触形成。     

物体生命度和真实大小在腹侧视觉通路上表征的研究进展

大脑如何感知物体并对感知到的物体进行类别的划分,这是视觉认知神经科学研究的重要目标之一。先前的研究证明,当我们看到物体时,大脑腹侧视觉通路能够对看到的物体进行识别并分类,进而使我们在行为上产生针对物体的不同交互方式。本文总结了腹侧视觉通路与物体视觉分类相关的最新研究进展,从物体在视觉皮层中的神经表征和机制等方面阐述了物体生命度与真实大小这两个重要组织维度的研究现状,提供了新的见解,同时指出了进一步研究的方向。     

发现果蝇具有基于经验的学习能力

利用先期学习所得的经验来调整随后的认知行为可以体现人类或者动物的某种高级智慧。最近,郭爱克研究员带领其研究小组经过三年多的研究发现：果蝇利用先期学习的经验可以显著提高其随后的视觉特征抽提能力。视觉特征抽提是一种从多个视觉特征（如形状、颜色）中选择关键特征的能力。     

内斜弱视猫的视觉诱发电位

内斜弱视猫的视觉诱发电位蔡浩然,周毅丁,李少敏,王伟（北京医科大学儿童视觉研究中心１０００３４）用棋盘格翻转和平面均匀光作刺激,研究了三只实验性内斜视模型猫的多导程视觉诱发电位（ＶＥＰｓ）。实验动物是在生后２０天行左眼外直肌切除术,然后在９—１３月龄...     

视知觉学习对于识别动态随机点立体图深度运动方向的作用

立体视觉不仅指对静态深度信息的感知,也包括对物体在三维空间中的运动方向的判断。本研究记录了人眼对于动态随机点图运动方向的辨别能力以及视觉训练在提高对动态信息分辨能力的作用。实验结果表明,对于没有任何相关经验的视力正常的受试者,很难分辨出动态随机点的深度运动方向,而视觉训练可以大大提高人眼对物体深度运动方向判断的敏感度。此外,这种视觉训练所达到的效果具有较长时间的持续性（至少6个月）。这种通过视觉训练提高受试者对立体运动信息的敏感度的方式为立体视觉相关的实验和研究提供了新的视角。     

The nucleotide-binding state of microtubules modulates kinesin processivity and the ability of Tau to inhibit kinesin-mediated transport

The ability of Tau to act as a potent inhibitor of kinesin's processive run length in vitro suggests that it may actively participate in the regulation of axonal transport in vivo. However, it remains unclear how kinesin-based transport could then proceed effectively in neurons, where Tau is expressed at high levels. One potential explanation is that Tau, a conformationally dynamic protein, has multiple modes of interaction with the microtubule, not all of which inhibit kinesin's processive run length. Previous studies support the hypothesis that Tau has at least two modes of interaction with microtubules, but the mechanisms by which Tau adopts these different conformations and their functional consequences have not been investigated previously. In the present study, we have used single molecule imaging techniques to demonstrate that Tau inhibits kinesin's processive run length in an isoform-dependent manner on GDP-microtubules stabilized with either paclitaxel or glycerol/DMSO but not guanosine-5'-((α,β)-methyleno)triphosphate (GMPCPP)-stabilized microtubules. Furthermore, the order of Tau addition to microtubules before or after polymerization has no effect on the ability of Tau to modulate kinesin motility regardless of the stabilizing agent used. Finally, the processive run length of kinesin is reduced on GMPCPP-microtubules relative to GDP-microtubules, and kinesin's velocity is enhanced in the presence of 4-repeat long Tau but not the 3-repeat short isoform. These results shed new light on the potential role of Tau in the regulation of axonal transport, which is more complex than previously recognized.     

Seeding of normal Tau by pathological Tau conformers drives pathogenesis of Alzheimer-like tangles

Neurofibrillary tangles (NFTs) in Alzheimer disease and related tauopathies are composed of insoluble hyperphosphorylated Tau protein, but the mechanisms underlying the conversion of highly soluble Tau into insoluble NFTs remain elusive. Here, we demonstrate that introduction of minute quantities of misfolded preformed Tau fibrils (Tau pffs) into Tau-expressing cells rapidly recruit large amounts of soluble Tau into filamentous inclusions resembling NFTs with unprecedented efficiency, suggesting a "seeding"-recruitment process as a highly plausible mechanism underlying NFT formation in vivo. Consistent with the emerging concept of prion-like transmissibility of disease-causing amyloidogenic proteins, we found that spontaneous uptake of Tau pffs into cells is likely mediated by endocytosis, suggesting a potential mechanism for the propagation of Tau lesions in tauopathy brains. Furthermore, sequestration of soluble Tau by pff-induced Tau aggregates attenuates microtubule overstabilization in Tau-expressing cells, supporting the hypothesis of a Tau loss-of-function toxicity in cells harboring NFTs. In summary, our study establishes a cellular system that robustly develops authentic NFT-like Tau aggregates, which provides mechanistic insights into NFT pathogenesis and a potential tool for identifying Tau-based therapeutics.     

Tau Monoclonal Antibody Generation Based on Humanized Yeast Models: IMPACT ON TAU OLIGOMERIZATION AND DIAGNOSTICS*

A link between Tau phosphorylation and aggregation has been shown in different models for Alzheimer disease, including yeast. We used human Tau purified from yeast models to generate new monoclonal antibodies, of which three were further characterized. The first antibody, ADx201, binds the Tau proline-rich region independently of the phosphorylation status, whereas the second, ADx215, detects an epitope formed by the Tau N terminus when Tau is not phosphorylated at Tyr¹⁸. For the third antibody, ADx210, the binding site could not be determined because its epitope is probably conformational. All three antibodies stained tangle-like structures in different brain sections of THY-Tau22 transgenic mice and Alzheimer patients, and ADx201 and ADx210 also detected neuritic plaques in the cortex of the patient brains. In hippocampal homogenates from THY-Tau22 mice and cortex homogenates obtained from Alzheimer patients, ADx215 consistently stained specific low order Tau oligomers in diseased brain, which in size correspond to Tau dimers. ADx201 and ADx210 additionally reacted to higher order Tau oligomers and presumed prefibrillar structures in the patient samples. Our data further suggest that formation of the low order Tau oligomers marks an early disease stage that is initiated by Tau phosphorylation at N-terminal sites. Formation of higher order oligomers appears to require additional phosphorylation in the C terminus of Tau. When used to assess Tau levels in human cerebrospinal fluid, the antibodies permitted us to discriminate patients with Alzheimer disease or other dementia like vascular dementia, indicative that these antibodies hold promising diagnostic potential.     

甲醛诱导Tau蛋白形成“孔道样”聚集结构

尽管Lin等(University of California, Santa Barbara)就蛋白构象病中细胞死亡的机制提出了“非特异性淀粉样离子通道”(aspecific amyloid ion channels)学说,但到目前为止,尚未发现神经Tau蛋白能形成“孔道样”聚集结构,也未寻找到可以导致蛋白质形成“孔道样”聚集结构的诱导剂．依据本实验室提出的“散发性老年痴呆发生发展中的内源性甲醛慢性损伤”假说,采用一定浓度的甲醛与Tau蛋白进行温育,观察到甲醛可以明显诱导Tau蛋白分子聚集并形成淀粉样沉积物,同时也观察到了Tau蛋白“孔道样”聚集结构．上述结果为探索甲醛诱导Tau蛋白错误折叠形成的产物导致细胞代谢障碍和死亡的机制提供了新的研究思路．     

Truncation and Activation of Dual Specificity Tyrosine Phosphorylation-regulated Kinase 1A by Calpain I: A MOLECULAR MECHANISM LINKED TO TAU PATHOLOGY IN ALZHEIMER DISEASE*

Hyperphosphorylation and dysregulation of exon 10 splicing of Tau are pivotally involved in pathogenesis of Alzheimer disease (AD) and/or other tauopathies. Alternative splicing of Tau exon 10, which encodes the second microtubule-binding repeat, generates Tau isoforms containing three and four microtubule-binding repeats, termed 3R-Taus and 4R-Taus, respectively. Dual specificity tyrosine-phosphorylation-regulated kinase 1A (Dyrk1A) lies at the Down syndrome critical region of chromosome 21. Overexpression of this kinase may contribute to the early Tau pathology in Down syndrome via phosphorylation of Tau and dysregulation of Tau exon 10. Here, we report that Dyrk1A was truncated at the C terminus and was associated with overactivation of calpain I in AD brain. Calpain I proteolyzed Dyrk1A in vitro first at the C terminus and further at the N terminus and enhanced its kinase activity toward Tau via increased V_max but not K_m. C-terminal truncation of Dyrk1A resulted in stronger activity than its full-length protein in promotion of exon 10 exclusion and phosphorylation of Tau. Dyrk1A was truncated in kainic acid-induced excitotoxic mouse brains and coincided with an increase in 3R-Tau expression and phosphorylation of Tau via calpain activation. Moreover, truncation of Dyrk1A was correlated with an increase in the ratio of 3R-Tau/4R-Tau and Tau hyperphosphorylation in AD brain. Collectively, these findings suggest that truncation/activation of Dyrk1A by Ca²⁺/calpain I might contribute to Tau pathology via promotion of exon 10 exclusion and hyperphosphorylation of Tau in AD brain.     

Ribosylation triggering Alzheimer's disease‐like Tau hyperphosphorylation via activation of CaMKII

Type 2 diabetes mellitus (T2DM) is regarded as one of the serious risk factors for age‐related cognitive impairment; however, a causal link between these two diseases has so far not been established. It was recently discovered that, apart from high D‐glucose levels, T2DM patients also display abnormally high concentrations of uric D‐ribose. Here, we show for the first time that the administration of D‐ribose, the most active glycator among monosaccharides, produces high levels of advanced glycation end products (AGEs) and, importantly, triggers hyperphosphorylation of Tau in the brain of C57BL/6 mouse and neuroblastoma N2a cells. However, the administration of D‐glucose showed no significant changes in Tau phosphorylation under the same experimental conditions. Crucially, suppression of AGE formation using an AGEs inhibitor (aminoguanidine) effectively prevents hyperphosphorylation of Tau protein. Further study shows AGEs resulted from ribosylation activate calcium‐/calmodulin‐dependent protein kinase type II (CaMKII), a key kinase responsible for Tau hyperphosphorylation. These data suggest that there is indeed a mechanistic link between ribosylation and Tau hyperphosphorylation. Targeting ribosylation by inhibiting AGE formation may be a promising therapeutic strategy to prevent Alzheimer's disease‐like Tau hyperphosphorylation and diabetic encephalopathies.     

Cellular Models of Aggregation-dependent Template-directed Proteolysis to Characterize Tau Aggregation Inhibitors for Treatment of Alzheimer Disease

Alzheimer disease (AD) is a degenerative tauopathy characterized by aggregation of Tau protein through the repeat domain to form intraneuronal paired helical filaments (PHFs). We report two cell models in which we control the inherent toxicity of the core Tau fragment. These models demonstrate the properties of prion-like recruitment of full-length Tau into an aggregation pathway in which template-directed, endogenous truncation propagates aggregation through the core Tau binding domain. We use these in combination with dissolution of native PHFs to quantify the activity of Tau aggregation inhibitors (TAIs). We report the synthesis of novel stable crystalline leucomethylthioninium salts (LMTX®), which overcome the pharmacokinetic limitations of methylthioninium chloride. LMTX®, as either a dihydromesylate or a dihydrobromide salt, retains TAI activity in vitro and disrupts PHFs isolated from AD brain tissues at 0.16 μm. The K_i value for intracellular TAI activity, which we have been able to determine for the first time, is 0.12 μm. These values are close to the steady state trough brain concentration of methylthioninium ion (0.18 μm) that is required to arrest progression of AD on clinical and imaging end points and the minimum brain concentration (0.13 μm) required to reverse behavioral deficits and pathology in Tau transgenic mice.     

Absence of Tau triggers age‐dependent sciatic nerve morphofunctional deficits and motor impairment

Dementia is the cardinal feature of Alzheimer's disease (AD), yet the clinical symptoms of this disorder also include a marked loss of motor function. Tau abnormal hyperphosphorylation and malfunction are well‐established key events in AD neuropathology but the impact of the loss of normal Tau function in neuronal degeneration and subsequent behavioral deficits is still debated. While Tau reduction has been increasingly suggested as therapeutic strategy against neurodegeneration, particularly in AD, there is controversial evidence about whether loss of Tau progressively impacts on motor function arguing about damage of CNS motor components. Using a variety of motor‐related tests, we herein provide evidence of an age‐dependent motor impairment in Tau?/? animals that is accompanied by ultrastructural and functional impairments of the efferent fibers that convey motor‐related information. Specifically, we show that the sciatic nerve of old (17–22‐months) Tau?/? mice displays increased degenerating myelinated fibers and diminished conduction properties, as compared to age‐matched wild‐type (Tau+/+) littermates and younger (4–6 months) Tau?/? and Tau+/+ mice. In addition, the sciatic nerves of Tau?/? mice exhibit a progressive hypomyelination (assessed by g‐ratio) specifically affecting large‐diameter, motor‐related axons in old animals. These findings suggest that loss of Tau protein may progressively impact on peripheral motor system.     

Co-immunoprecipitation with Tau Isoform-specific Antibodies Reveals Distinct Protein Interactions and Highlights a Putative Role for 2N Tau in Disease

Alternative splicing generates multiple isoforms of the microtubule-associated protein Tau, but little is known about their specific function. In the adult mouse brain, three Tau isoforms are expressed that contain either 0, 1, or 2 N-terminal inserts (0N, 1N, and 2N). We generated Tau isoform-specific antibodies and performed co-immunoprecipitations followed by tandem mass tag multiplexed quantitative mass spectrometry. We identified novel Tau-interacting proteins of which one-half comprised membrane-bound proteins, localized to the plasma membrane, mitochondria, and other organelles. Tau was also found to interact with proteins involved in presynaptic signal transduction. MetaCore analysis revealed one major Tau interaction cluster that contained 33 Tau pulldown proteins. To explore the pathways in which these proteins are involved, we conducted an ingenuity pathway analysis that revealed two significant overlapping pathways, “cell-to-cell signaling and interaction” and “neurological disease.” The functional enrichment tool DAVID showed that in particular the 2N Tau-interacting proteins were specifically associated with neurological disease. Finally, for a subset of Tau interactions (apolipoprotein A1 (apoA1), apoE, mitochondrial creatine kinase U-type, β-synuclein, synaptogyrin-3, synaptophysin, syntaxin 1B, synaptotagmin, and synapsin 1), we performed reverse co-immunoprecipitations, confirming the preferential interaction of specific isoforms. For example, apoA1 displayed a 5-fold preference for the interaction with 2N, whereas β-synuclein showed preference for 0N. Remarkably, a reverse immunoprecipitation with apoA1 detected only the 2N isoform. This highlights distinct protein interactions of the different Tau isoforms, suggesting that they execute different functions in brain tissue.