Interactions of recombinant prions with compounds of therapeutical significance

The transformation of the cellular prion protein (PrP(C)) into the infectious form (PrP(Sc)) is implicated in the invariably fatal transmissible spongiform encephalopathies. To identify a mechanism to prevent the undesired PrP(C)-->PrP(Sc) transformation, we investigated the interactions of recombinant prion proteins with a number of potential therapeutic agents which inhibit the PrP(Sc) formation, infectivity, and the accumulation of the misfolded form. We show that the prion aggregates formed in the presence of six compounds have no beta-structure, which is typical of the infectious form, and possess considerably higher alpha-helical content than the normal PrP(C). The investigated compounds stimulate the formation of alpha-helices and the destruction of beta-structure. They prevent the transformation of alpha-helical structure into beta-sheets. Probably, this is the reason for the resistance to PrP(C)-->PrP(Sc) transformation in the presence of these compounds. The results may be useful for the future therapy of neurodegenerative diseases.     

Exploring the capacity of trigger factor to function as a shield for ribosome bound polypeptide chains

Ribosome-bound trigger factor (TF) is the first chaperone encountered by a nascent polypeptide chain in bacteria. TF has been proposed to form a cradle-shaped shield for nascent chains up to approximately 130 residues to fold in a protected environment upon exit from the ribosome. We report that nascent chains of luciferase up to 280 residues in length are relatively protected by TF against digestion by proteinase K. In contrast, nascent chains of the constitutively unstructured protein alpha-synuclein were not protected, although they were in close proximity to TF by crosslinking. Thus, TF is not a general shield for nascent chains. Protease protection appears to depend on a hydrophobic interaction of TF with nascent polypeptides.     

A new proteinase 3 substrate with improved selectivity over human neutrophil elastase

We report the synthesis and enzymatic studies on a new proteinase 3 intermolecular quenched substrate with enhanced selectivity over neutrophil elastase. Using combinatorial chemistry methods, we were able to synthesize the hexapeptide library with the general formula ABZ-Tyr-Tyr-Abu-X₁′-X₂′-X₃′-Tyr(3-NO₂)-NH₂ using the mix and split method. The iterative deconvolution of such a library allowed us to obtain the sequence ABZ-Tyr-Tyr-Abu-Asn-Glu-Pro-Tyr(3-NO₂)-NH₂ with a high specificity constant (k_cat/K_M = 1534 × 10³ M⁻¹ s⁻¹) and superior selectivity over neutrophil elastase and other neutrophil-derived serine proteases. Moreover, using the obtained substrate, we were able to detect a picomolar concentration of proteinase 3 (PR3). Incubation of the above-mentioned substrate with neutrophil lysate resulted in a strong fluorescent signal that was significantly reduced in the presence of a PR3 selective inhibitor.     

Recognition of microbial molecular patterns and stimulation of prophenoloxidase activation by a β-1,3-glucanase-related protein in Manduca sexta larval plasma

Detection of pathogenic invaders is the essential first step of a successful defense response in multicellular organisms. In this study, we have identified a new member of the ??-1,3-glucanase-related protein superfamily from the tobacco hornworm Manduca sexta. This protein, designated microbe binding protein (MBP), is 61% identical in sequence to Bombyx mori Gram-negative bacteria binding protein, but only 34-36% identical to M. sexta ??-1,3-glucan recognition protein-1 and 2. Its mRNA levels were strongly up-regulated in hemocytes and fat body of immune challenged larvae, along with an increase in concentration of the plasma protein. We expressed M. sexta MBP in a baculovirus-insect cell system. The purified protein associated with intact bacteria and fungi. It specifically bound to lipoteichoic acid, lipopolysaccharide, diaminopimelic acid-type peptidoglycans (DAP-PGs) from Escherichia coli and Bacillus subtilis, but less so to laminarin or Lys-type PG from Staphylococcus aureus. The complex binding pattern was influenced by other plasma factors and additional microbial surface molecules. After different amounts of MBP had been incubated with larval plasma on ice, a concentration-dependent increase in phenoloxidase (PO) activity occurred in the absence of any microbial elicitor. The activity increase was also observed in the mixture of plasma and a bacterial or fungal cell wall component. The prophenoloxidase (proPO) activation became more prominent when DAP-PGs, Micrococcus luteus Lys-PG, or lipoteichoic acid was included in the mixture of MBP and plasma. Statistic analysis suggested that a synergistic enhancement of proPO activation was caused by an interaction between MBP and these elicitors, but not S. aureus Lys-PG, lipopolysaccharide, curdlan, or laminarin. These data indicate that M. sexta MBP is a component of the surveillance mechanism and, by working together with other pattern recognition molecules and serine proteinases, triggers the proPO activation system.     

一种快速、经济提取外周凝血基因组DNA方法的建立

目的：建立一种经济、快速且高质量提取人体外周凝血DNA的方法。方法：摸索最佳的匀浆条件,对外周凝血块进行匀浆,采用Ⅺ法对匀浆液进行基因组DNA的提取,通过凝胶电泳、单重PCR和多重PCR检测凝血基因组DNA的提取产量和质量。并分别与常规的凝血基因组DNA提取方法,即蛋白酶K消化法,以及提取抗凝血基因组DNA的Ⅺ法进行比较分析。结果：最佳的匀浆条件为：39000map,15秒。在此条件下提取的基因组DNA完整性好,纯度和产量与蛋白酶K消化法提取凝血DNA和KI法提取抗凝血DNA的结果相比,没有统计学差异。单重PCR和多重PCR也获得了理想的扩增结果。结论：与常规的外周凝血提取方法相比（蛋白酶K消化法）,本方法节省了时间和成本,能快速、经济、有效地提取外周凝血基因组DNA,可用于后续的科研和临床诊断需要,解决了部分科研机构血液基因组DNA的样本来源问题。     

胰蛋白酶诱导人脐静脉内皮细胞分泌白细胞介素-8

目的：研究胰蛋白酶对IL-8释放的影响。方法：分离、培养人脐静脉内皮细胞（human umbilical vein endothelialcells,HU-VECs）、倒置显微镜观察形态变化,流式细胞术检测内皮细胞标志和蛋白酶活化受体．2（proteinase．activatedreceptor．2,PAR-2）表达,ELISA检测HUVECs培养上清中IL-8水平。结果：HUVECs表达内皮细胞标志和PAR-2。刺激16h,1g／ml胰蛋白酶和100MPAR-2激活肽组HUVECs单层均匀性降低。胰蛋白酶能够显著刺激HUVECs释放IL-8,PAR-2激活肽也诱导IL-8水平升高。蛋白酶抑制剂和PAR-2抑制肽均能够显著抑制胰蛋白酶诱导的IL-8释放。PAR-2激活肽和胰蛋白酶诱导升高的IL-8水平之间成正相关性。结论：胰蛋白酶很可能通过PAR-2激活促进血管内皮细胞释放IL-8。     

一种快速、经济提取外周凝血基因组DNA 方法的建立

目的:建立一种经济、快速且高质量提取人体外周凝血DNA的方法。方法:摸索最佳的匀浆条件,对外周凝血块进行匀浆,采用KI法对匀浆液进行基因组DNA的提取,通过凝胶电泳、单重PCR和多重PCR检测凝血基因组DNA的提取产量和质量,并分别与常规的凝血基因组DNA提取方法,即蛋白酶K消化法,以及提取抗凝血基因组DNA的KI法进行比较分析。结果:最佳的匀浆条件为:39000 rmp,15秒。在此条件下提取的基因组DNA完整性好,纯度和产量与蛋白酶K消化法提取凝血DNA和KI法提取抗凝血DNA的结果相比,没有统计学差异。单重PCR和多重PCR也获得了理想的扩增结果。结论:与常规的外周凝血提取方法相比(蛋白酶K消化法),本方法节省了时间和成本,能快速、经济、有效地提取外周凝血基因组DNA,可用于后续的科研和临床诊断需要,解决了部分科研机构血液基因组DNA的样本来源问题。     

烟草蛋白酶抑制剂基因的电子克隆及生物信息学分析

蛋白酶抑制剂可以增强植物对病虫害的抵抗能力,为了深入研究蛋白酶抑制剂在烟草中的作用机制,利用生物信息学的方法,成功获得了烟草品种K326中的4种蛋白酶抑制剂cDNA序列(NtPI-1、NtPI-2、NtPI-3和NtPI-4)并对其进行了序列分析.它们编码的氨基酸序列都具有典型的马铃薯蛋白酶抑制剂Ⅰ家族功能结构域,属于马铃薯蛋白酶抑制剂Ⅰ家族成员.序列分析表明,4种蛋白酶抑制剂基因cDNA序列均具有完整的开放读码框,依次编码128、95、94和72个氨基酸残基,它们的氨基酸序列一致性在31％-38％之间.系统树分析表明,烟草品种K326中的4种蛋白酶抑制剂分散在进化树的不同位置,形成不同亚群.     

Ocimum sanctum essential oil inhibits virulence attributes in Candida albicans

Candida albicans is an opportunistic human fungal pathogen which causes disease mainly in immunocompromised patients. Activity of hydrolytic enzymes is essential for virulence of C. albicans and so is the capacity of these cells to undergo transition from yeast to mycelial form of growth. Ocimum sanctum is cultivated worldwide for its essential oil which exhibits medicinal properties. This work evaluates the anti-virulence activity of O. sanctum essential oil (OSEO) on 22 strains of C. albicans (including a standard strain ATCC 90028) isolated from both HIV positive and HIV negative patients. Candida isolates were exposed to sub-MICs of OSEO. In vitro secretion of proteinases and phospholipases was evaluated by plate assay containing BSA and egg yolk respectively. Morphological transition from yeast to filamentous form was monitored microscopically in LSM. For genetic analysis, respective genes associated with morphological transition (HWP1), proteinase (SAP1) and phospholipase (PLB2) were also investigated by Real Time PCR (qRT-PCR). Results were analyzed using Student's t-test. OSEO inhibits morphological transition in C. albicans and had a significant inhibitory effect on extracellular secretion of proteinases and phospholipases. Expression profile of respective selected genes associated with C. albicans virulence by qRT-PCR showed a reduced expression of HWP1, SAP1 and PLB2 genes in cells treated with sub-inhibitory concentrations of OSEO. This work suggests that OSEO inhibits morphological transition in C. albicans and decreases the secretion of hydrolytic enzymes involved in the early stage of infection as well as down regulates the associated genes. Further studies will assess the clinical application of OSEO and its constituents in the treatment of fungal infections.