Methods for syntheses of <Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="Italic">DL</Emphasis>-aspartic acid derivatives

Summary. A novel practical method for the synthesis of N-methyl-DL-aspartic acid 1 (NMA) and new syntheses for N-methyl-aspartic acid derivatives are described. NMA 1, the natural amino acid was synthesized by Michael addition of methylamine to dimethyl fumarate 5. Fumaric or maleic acid mono-ester and -amide were regioselectively transformed into beta-substituted aspartic acid derivatives. In the cases of maleamic 11a or fumaramic esters 11b, the α-amide derivative 13 was formed, but hydrolysis of the product provided N-methyl-DL-asparagine 9 via base catalyzed ring closure to DL-α-methylamino-succinimide 4, followed by selective ring opening. Efficient methods were developed for the preparation of NMA-α-amide 13 from unprotected NMA via sulphinamide anhydride 15 and aspartic anhydride 3 intermediate products. NMA diamide 16 was prepared from NMA dimethyl ester 6 and methylamino-succinimide 4 by ammonolysis. Temperature-dependent side reactions of methylamino-succinimide 4 led to diazocinone 18, resulted from self-condensation of methylamino-succinimide via nucleophyl ring opening and the subsequent ring-transformation.     

运动提高沉默信息调节因子2相关酶1改善阿尔兹海默症

阿尔兹海默症(Alzheimer's disease, AD)是一种神经退行性疾病,β-淀粉样蛋白(β-amyloid, Aβ)沉积和Tau蛋白过度磷酸化是其主要病理特征。沉默信息调节因子2相关酶1 (silent mating-type information regulation 2 homolog 1, SIRT1)具有去乙酰化作用,能够使多种类型组蛋白及非组蛋白脱乙酰化,在AD发病过程中占据重要地位。近年研究发现,运动能够激活SIRT1减缓AD进程,其机制可能是:抑制β-分泌酶活性、提高α-分泌酶活性,减少Aβ生成;减少过度磷酸化Tau蛋白集聚;与过氧化体增殖物激活型受体γ辅激活因子-1α(peroxisome proliferator-activated receptor γ coactivator-1α,PGC-1α)相互作用以促进线粒体生物发生;上调同源性磷酸酶张力蛋白诱导激酶1(phosphatase and tensin homolog induced putative kinase1,PINK1)/Parkin信号通路改善线粒体自噬;去乙酰化核转录因子-κB(nuclear factor kappa B, NF-κB)以抑制神经炎症;提高海马中脑源性神经营养因子(brain-derived neurotrophic factor, BDNF)、神经胶质源性营养因子(glial cellline-derived neurotrophic factor,GDNF)等营养因子的蛋白质水平,以及抑制ApoE4基因进而增强神经元突触可塑性。本文总结了运动通过调控SIRT1改善AD的作用和机制,为预防及治疗AD提供新的思路。     

Phospho-ΔNp63α/microRNA network modulates epigenetic regulatory enzymes in squamous cell carcinomas

The tumor protein (TP) p63/microRNAs functional network may play a key role in supporting the response of squamous cell carcinomas (SCC) to chemotherapy. We show that the cisplatin exposure of SCC-11 cells led to upregulation of miR-297, miR-92b-3p, and miR-485-5p through a phosphorylated ΔNp63α-dependent mechanism that subsequently modulated the expression of the protein targets implicated in DNA methylation (DNMT3A), histone deacetylation (HDAC9), and demethylation (KDM4C). Further studies showed that mimics for miR-297, miR-92b-3p, or miR-485-5p, along with siRNA against and inhibitors of DNMT3A, HDAC9, and KDM4C modulated the expression of DAPK1, SMARCA2, and MDM2 genes assessed by the quantitative PCR, promoter luciferase reporter, and chromatin immunoprecipitation assays. Finally, the above-mentioned treatments affecting epigenetic enzymes also modulated the response of SCC cells to chemotherapeutic drugs, rendering the resistant SCC cells more sensitive to cisplatin exposure, thereby providing the groundwork for novel chemotherapeutic venues in treating patients with SCC.     

Epigenetic interplay of histone modifications and DNA methylation mediated by HDA6

One of the most fundamental questions in the control of gene expression is how epigenetic patterns of DNA methylation and histone modifications are established. Our recent studies demonstrate that histone deacetylase HDA6 integrates DNA methylation and histone modifications in gene silencing by interacting with DNA methyltransferase MET1 and histone demethylase FLD, suggesting that regulatory crosstalk between histone modifications and DNA methylation could be mediated by the interaction of various epigenetic modification proteins.     

Histone deacetylase 6 interacts with the microtubule-associated protein tau

Histone deacetylase 6 (HDAC6), a unique cytoplasmic deacetylase, likely plays a role in neurodegeneration by coordinating cell responses to abnormal protein aggregation. Here, we provide in vitro and in vivo evidence that HDAC6 interacts with tau, a microtubule-associated protein that forms neurofibrillary tangles in Alzheimer's disease. This interaction is mediated by the microtubule-binding domain on tau and the Ser/Glu tetradecapeptide domain on HDAC6. Treatment with tubacin, a selective inhibitor of tubulin deacetylation activity of HDAC6, did not disrupt HDAC6–tau interaction. Nonetheless tubacin treatment attenuated site-specific tau phosphorylation, as did shRNA-mediated knockdown of HDAC6. Proteasome inhibition potentiated HDAC6–tau interactions and facilitated the concentration and co-localization of HDAC6 and tau in a perinuclear aggresome-like compartment, independent of HDAC6 tubulin deacetylase activity. Furthermore, we observed that in Alzheimer's disease brains the protein level of HDAC6 was significantly increased. These findings establish HDAC6 as a tau-interacting protein and as a potential modulator of tau phosphorylation and accumulation.     

Structural variation in the glycan strands of bacterial peptidoglycan

The normal, unmodified glycan strands of bacterial peptidoglycan consist of alternating residues of beta-1,4-linked N-acetylmuramic acid and N-acetylglucosamine. In many species the glycan strands become modified after their insertion into the cell wall. This review describes the structure of secondary modifications and of attachment sites of surface polymers in the glycan strands of peptidoglycan. It also provides an overview of the occurrence of these modifications in various bacterial species. Recently, enzymes responsible for the N-deacetylation, N-glycolylation and O-acetylation of the glycan strands were identified. The presence of these modifications affects the hydrolysis of peptidoglycan and its enlargement during cell growth. Glycan strands are frequently deacetylated and/or O-acetylated in pathogenic species. These alterations affect the recognition of bacteria by host factors, and contribute to the resistance of bacteria to host defence factors such as lysozyme.     

基于激光共聚焦同步双扫描技术的LC3脱乙酰化修饰调控自噬的机理研究

激光共聚焦同步双扫描(simultaneous,SIM)技术在常规扫描单元的基础上,引入一个同步扫描单元(SIM scanner),该技术独立控制了两个激光束,一个用于激光光刺激,另一个用于同步成像。本实验中,采用激光共聚焦同步双扫描系统的405 nm和488 nm激光分别对细胞的特定部位进行刺激和同步成像,实时检测了LC3复合物的形成,记录并分析了乙酰化前后LC3的光动力学变化过程,证实了LC3的脱乙酰化修饰是自噬性降解所必须的,本实验体系为激光共聚焦双扫描技术的推广提供了一个很好的平台。SIM技术的应用,解决了刺激过程无法成像的问题,为漂白后荧光恢复(fluorescence recovery after photobleaching,FRAP)、漂白后荧光损失(fluorescence loss in photobleaching,FLIP)和光诱导激活等研究提供了最佳的解决方案,可作为光刺激的一种实验模式在很多实验设计中进行延伸应用。     

Enzymatic selective acylation of glycosides in ionic liquids: significantly enhanced reactivity and regioselectivity

The enzymatic selective acylations of carbohydrates in ionic liquids were explored in both organic solvents and ionic liquids to see any significant differences in terms of reactivity and regioselectivity between two different classes of reaction media. Monoprotected glycosides (methyl-6-O-trityl-glucosides and galactosides) were chosen as the substrates with Candida rugosa lipase as an acylation enzyme. Two organic solvents, THF and chloroform, and two ionic liquids, [BMIM]⁺PF₆⁻ ([BMIM]⁺ = 1-butyl-3-methylimidazolium) and [MOEMIM]⁺PF₆⁻ ([MOEMIM]⁺ = 1-methoxyethyl-3-methylimidazolium), were employed as reaction media. The enzymatic reactions were performed in the presence of vinyl acetate at room temperature. It was observed that the reactions in ionic liquids took place more rapidly and more selectively than those in conventional organic solvents.     

Effects of several acetylated chitooligosaccharides on antioxidation,antiglycation and NO generation in erythrocyte

Three kinds of chitooligosaccharides (COS) with different degrees of deacetylation were prepared and named MD90, MD70 and MD50, respectively. Antioxidation, antiglycation and nitric oxide (NO) promotion in erythrocyte of these samples were investigated. The results showed that COS, especially MD90 had obviously inhibitory effects on oxidation and glycation. In addition, MD90 displayed stronger effect on increasing endogenous NO content than both MD70 and MD50, whose degrees of deacetylation were lower. The results indicated that amino group in COS has a certain effect on the activities of COS. As COS have a conformed activity to treat diabetes, the results of this study may be meaningful for further understanding the mechanism of the action.