Analysis of Flavivirus NS5 Methyltransferase Cap Binding

The flavivirus 2′-O-nucleoside N-terminal RNA methyltransferase (MTase) enzyme is responsible for methylating the viral RNA cap structure. To increase our understanding of the mechanism of viral RNA cap binding we performed a detailed structural and biochemical characterization of the guanosine cap-binding pocket of the dengue (DEN) and yellow fever (YF) virus MTase enzymes. We solved an improved 2.1 Å resolution crystal structure of DEN2 Mtase, new 1.5 Å resolution crystal structures of the YF virus MTase domain in apo form, and a new 1.45 Å structure in complex with guanosine triphosphate and RNA cap analog. Our structures clarify the previously reported DEN MTase structure, suggest novel protein-cap interactions, and provide a detailed view of guanine specificity. Furthermore, the structures of the DEN and YF proteins are essentially identical, indicating a large degree of structural conservation amongst the flavivirus MTases. Guanosine triphosphate analog competition assays and mutagenesis analysis, performed to analyze the biochemical characteristics of cap binding, determined that the major interaction points are (i) guanine ring via π−π stacking with Phe24, N1 hydrogen interaction with the Leu19 backbone carbonyl via a water bridge, and C2 amine interaction with Leu16 and Leu19 backbone carbonyls; (ii) ribose 2′ hydroxyl interaction with Lys13 and Asn17; and (iii) α-phosphate interactions with Lys28 and Ser215. Based on our mutational and analog studies, the guanine ring and α-phosphate interactions provide most of the energy for cap binding, while the combination of the water bridge between the guanine N1 and Leu19 carbonyl and the hydrogen bonds between the C2 amine and Leu16/Leu19 carbonyl groups provide for specific guanine recognition. A detailed model of how the flavivirus MTase protein binds RNA cap structures is presented.     

Stoichiometric network reconstruction and analysis of yeast sphingolipid metabolism incorporating different states of hydroxylation

The first elaborate metabolic model of Saccharomyces cerevisiae sphingolipid metabolism was reconstructed in silico. The model considers five different states of sphingolipid hydroxylation, rendering it unique among other models. It is aimed to clarify the significance of hydroxylation on sphingolipids and hence to interpret the preferences of the cell between different metabolic pathway branches under different stress conditions. The newly constructed model was validated by single, double and triple gene deletions with experimentally verified phenotypes. Calcium sensitivity and deletion mutations that may suppress calcium sensitivity were examined by CSG1 and CSG2 related deletions. The model enabled the analysis of complex sphingolipid content of the plasma membrane coupled with diacylglycerol and phosphatidic acid biosynthesis and ATP consumption in in silico cell. The flux data belonging to these critically important key metabolites are integrated with the fact of phytoceramide induced cell death to propose novel potential drug targets for cancer therapeutics. In conclusion, we propose that IPT1, GDA1, CSG and AUR1 gene deletions may be novel candidates of drug targets for cancer therapy according to the results of flux balance and variability analyses coupled with robustness analysis.     

Immunodiagnosis of platelet activation in immune thrombocytopenia through scFv antibodies cognate to activated IIb3 integrins

Immune thrombocytopenia (ITP) is an autoimmune bleeding disorder characterized by low platelet count and presence of IgG autoantibodies to platelet surface glycoproteins, such as $$\alpha$$IIbβ3 and GPIb/IX. Our previous work has shown that platelets in ITP patients exist in an activated state. Two different marker-based approaches are used to study the course of platelet activation: (1) binding of PAC-1 antibody, signifying a change in αIIbβ3 conformation, and (2) expression of P-selectin, signifying alpha granule content release from platelets. Here, we describe the development of a new scFv antibody (R38) that, compared with PAC-1, appears to better distinguish between platelets of ITP patients and healthy controls. Notably, R38 was generated using commercially sourced resting-state integrin that was coated on a microtiter plate. Its ability to distinguish between ITP patients and healthy controls thus suggests that inadvertent integrin activation caused by coating involves a conformational change and exposure of a cryptic epitope. This report also describes for the first time the potential use of an scFv antibody in the immunodiagnosis of platelet activation in ITP patients.     

滤泡辅助性T细胞在特发性血小板减少性紫癜患者的变化及其意义

目的：研究滤泡辅助性T细胞（T follicular helper cells,Tfh）在免疫性血小板减少性紫癜（immune thrombocytopenic purpura,ITP）患者的表达并探讨其临床意义。方法：用流式细胞术检测20例健康人、25例ITP患者外周血CXCR5＋CD4＋T细胞占CD4＋T细胞的比例。结果：与健康对照组相比,ITP患者外周血CXCR5＋CD4＋T细胞占CD4＋T细胞的比例显著增高（P〈0.05）。结论：Tfh在ITP患者外周血比例增高,为Tfh能否为ITP的免疫调节和干预提出新的方向提供了证据。     

The clinical effect of Prednisone in combination with Mycophenolate mofetil on idiopathic thrombocytopenic purpura (ITP) and its influence on the level of peripheral blood T lymphocytes and NK lymphocytes

ObjectiveTo explore he curative effect and safety of Prednisone in combination with Mycophenolate in treating ITP and its influence on the level of peripheral blood T lymphocytes and NK lymphocytes.Method93 cases of ITP patients were divided into the observation group and the control group by the Random Number Table method, 48 cases for the observation group, 45 for another. Patients in the control group orally took 0.5 mg/kg Prednisone Acetate tablets daily, two times each in the morning and evening. And the observation group, based on the treatment of the control group, orally took Mycophenolate Mofetil Dispersible tablets twice a day, 1 g each time. According to patients’ conditions, 3 to 5 courses were set for treatment with 3 weeks a course. Compared PLT amount and the changing situation of inflammatory factors, CD3⁺ and CD3⁺CD95L⁺ before and after the treatment, the level of CD3⁺Caspase-3⁺ and CD3⁺Caspase-8⁺, NK⁺, NK⁺ CD95L⁺, NK⁺Caspase-3⁺, NK⁺Caspase-8, the curative effect and adverse events.ResultAfter treatment, PLT amount in both groups increased, and the increase in the observation group was much higher than that of the control group, the difference had statistical significance (P < 0.05). The time needed for PLT amount in the control group to reach the normal and peak values was longer than that of the observation group, whose PLT peak value was higher than another group. The difference had statistical significance (P < 0.05). After the treatment, the levels of TNF-α and IL-6 were lowered, and the value of the observation group was lower than that of another. The difference between and within the group has statistical significance. After the treatment, the level of CD3⁺, CD3⁺CD95L⁺ and CD3⁺Caspase-8⁺ is much higher and CD3⁺Caspase-3⁺ level lower than that before the treatment. The difference has statistical significance (P < 0.05). After the treatment, the level of NK⁺ and NK⁺ CD95L⁺ is higher and the level of NK⁺Caspase-8⁺ lower than that before the treatment. The difference has statistical significance (P < 0.05). After the treatment, the total effective rate 91.67% of the observation group is much higher than that 75.56% of another. The difference has statistical significance (P < 0.05). After the treatment, the incidence rate of adverse events in the control group is 11.11% (5/45), while 4.17% (2/48) in the observation group. The difference between groups has statistical significance (χ² = 3.890, P < 0.05).ConclusionThe curative effect of Prednisone in combination with Mycophenolate on ITP patients is better than orally taking Prednisone tablets. Moreover, when it comes to Prednisone in combination with Mycophenolate, both the PLT amount and immunocompetence are improved without much adverse reaction, and the molecules of peripheral blood T lymphocytes and NK lymphocytes can be effectively adjusted to relieve the symptoms. So the method is trustworthy to be popularized for clinical practices.     

大剂量丙种球蛋白联合地塞米松治疗重度ITP疗效观察

目的评价大剂量丙种球蛋白联合地塞米松、单独大剂量地塞米松及单独大剂量丙种球蛋白3种方法治疗重度ITP的疗效.方法对人院时PLT≤25×109/L,出血倾向明显的45例患儿随机分成3个组,每组15例.联合组:静滴丙种球蛋白1.0g·kg-1·d-1,连用2天,同时静滴地塞米松1.5mg·kg-1·d-1,连用7天,第7天起口服强的松2mg·kg-1·d-1;地塞米松组:静滴地塞米松1.5mg·kg-1·d-1,连用7天,第7天起口服强的松2mg·kg-1·d-1;丙种球蛋白组:静滴丙种球蛋白1.0g·kg-1·d-1,连用2天.连续监测治疗效果.结果联合组、丙种球蛋白组、地塞米松组使PLT≥50×109/L时间分别为(2.0±1.1)天,(2.8士1.2)天,(3.9士1.3)天;≥100×109/L时间分别为(4.0±1.4)天,(5.2土1.5)天,(6.9±1.7)天;PLT的峰值(×109/L)分别为(368±131),(317±121),(213±76). 结论大剂量丙种球蛋白联合地塞米松静滴治疗重度ITP比单纯用其中任一种药物升高血小板的作用更为显著,迅速.     

Recruitment and diversification of an ecdysozoan family of neuropeptide hormones for black widow spider venom expression

Venoms have attracted enormous attention because of their potent physiological effects and dynamic evolution, including the convergent recruitment of homologous genes for venom expression. Here we provide novel evidence for the recruitment of genes from the Crustacean Hyperglycemic Hormone (CHH) and arthropod Ion Transport Peptide (ITP) superfamily for venom expression in black widow spiders. We characterized latrodectin peptides from venom gland cDNAs from the Western black widow spider (Latrodectus hesperus), the brown widow (Latrodectus geometricus) and cupboard spider (Steatoda grossa). Phylogenetic analyses of these sequences with homologs from other spider, scorpion and wasp venom cDNAs, as well as CHH/ITP neuropeptides, show latrodectins as derived members of the CHH/ITP superfamily. These analyses suggest that CHH/ITP homologs are more widespread in spider venoms, and were recruited for venom expression in two additional arthropod lineages. We also found that the latrodectin 2 gene and nearly all CHH/ITP genes include a phase 2 intron in the same position, supporting latrodectin's placement within the CHH/ITP superfamily. Evolutionary analyses of latrodectins suggest episodes of positive selection along some sequence lineages, and positive and purifying selection on specific codons, supporting its functional importance in widow venom. We consider how this improved understanding of latrodectin evolution informs functional hypotheses regarding its role in black widow venom as well as its potential convergent recruitment for venom expression across arthropods.     

不同载体固定化胰蛋白酶酶学特性的研究

目的:研究以壳聚糖、复合硅胶、阴离子交换树脂为载体固定化胰蛋白酶的酶学特性。方法:通过测定不同载体固定化胰蛋白酶的活力得其最适反应温度值、最适反应pH值和米氏常数(Km)值。结果:以壳聚糖、复合硅胶、阴离子交换树脂为载体制备固定化胰蛋白酶的最适反应温度分别为70℃、60℃、60℃;最适反应pH值分别为7.5、8.0、8.0;表观米氏常数K’m分别为22.72mg/ml、25.12mg/ml、29.04mg/ml。结论:与游离酶相比,固定化胰蛋白酶均表现出一定的热稳定性、酸碱稳定性,利于工业化生产。     

Thiazolidinediones increase the number of platelets in immune thrombocytopenic purpura mice via inhibition of phagocytic activity of the reticulo-endothelial system

Thiazolidinediones (TZDs) have broad spectrum of actions, including immunomodulating effects that are dependent or independent of the target nuclear receptor, peroxisome proliferator activated receptor-gamma (PPAR-gamma). In this study, we investigated the effect of TZDs on the platelet numbers in male immune thrombocytopenic purpura (ITP) model mice, (NZW x BXSB)F(1) (W/BF(1)) in vivo, and attempted to clarify the mechanism of action. Seven-day treatment with troglitazone increased platelet counts by 66% compared with those of controls. Within two weeks after the termination of the treatment period, the numbers of platelets were decreased to the level in controls. Pioglitazone showed only weak increasing effect on platelet counts in short-term experiment. However, long-term treatment with the drug resulted in a more pronounced up-regulation of platelets. We next assayed the platelet-associated antibodies (PAA) and the survival rate of antibody-sensitized mouse erythrocytes (Ab-mRBC) in W/BF1 mice. Pioglitazone slightly decreased the production of PAA and significantly elongated the survival period of Ab-mRBC in vivo. These drugs showed dose-dependent inhibitory effects on the cell proliferation and Fcgamma receptor (FcgammaR)-mediated phagocytic activity of macrophage-like cells in vitro. These results suggest that TZDs improve platelet counts in this mouse model mainly by suppressing systemic reticulo-endothelial phagocytic function.