Absence of Tec family kinases interleukin-2 inducible T cell kinase (Itk) and Bruton's tyrosine kinase (Btk) severely impairs Fc epsilonRI-dependent mast cell responses

Mast cells are critical effector cells in the pathophysiology of allergic asthma and other IgE-mediated diseases. The Tec family of tyrosine kinases Itk and Btk serve as critical signal amplifiers downstream of antigen receptors. Although both kinases are expressed and activated in mast cells following FcεRI stimulation, their individual contributions are not clear. To determine whether these kinases play unique and/or complementary roles in FcεRI signaling and mast cell function, we generated Itk and Btk double knock-out mice. Analyses of these mice show decreased mast cell granularity and impaired passive systemic anaphylaxis responses. This impaired response is accompanied by a significant elevation in serum IgE in Itk/Btk double knock-out mice. In vitro analyses of bone marrow-derived mast cells (BMMCs) indicated that Itk/Btk double knock-out BMMCs are defective in degranulation and cytokine secretion responses downstream to FcεRI activation. These responses were accompanied by a significant reduction in PLCγ2 phosphorylation and severely impaired calcium responses in these cells. This defect also results in altered NFAT1 nuclear localization in double knock-out BMMCs. Network analysis suggests that although they may share substrates, Itk plays both positive and negative roles, while Btk primarily plays a positive role in mast cell FcεRI-induced cytokine secretion.     

Sneezing reflex is mediated by a peptidergic pathway from nose to brainstem

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IBVS1基因表达载体PG-S1的构建

以含有鸡传染性支气管炎病毒S1基因的载体P^IBV-Z和含有CMV启动子的栽体质粒P^EGFR-C1为材料,构建了可表达IBV S1基因的表达载体P^G-S1,经酶切、电泳和PCR检测结果证实,构建的载体符合目的要求,可以作为表达载体用于鸡的抗病育种。     

Bcl-2 and caspase-8 related anoikis resistance in human osteosarcoma MG-63 cells

Detachment of adherent cells from extracellular matrix results in apoptosis, a process termed "anoikis". Resistance to anoikis is implicated in the progression of many malignancies by facilitating the migration and eventual colonization of distant sites. Human kidney epithelial cells 293T, human osteoblast cells hFOB 1.19 and human osteosarcoma cells Saos-2 significantly underwent anoikis when adherence was prevented. But human osteosarcoma MG-63 cells were distinctly anoikis resistant when detached. They formed large aggregates and showed little apoptosis compared to the other cells. When MG-63 cells were in suspension, caspase-8, physically associated with death receptor was activated by cell-matrix detachment, whereas. Caspase-3 and caspase-9 were not activated. Translational level of Bcl-2 significantly increased in a time-dependent manner, but the level of beta-catenin and PI3K did not. Caspase-8 participates in an anoikis-inducing process in MG-63 cells at an early time, and overexpression of Bcl-2 blocks activation of caspase-8 making MG-63 cells anoikis resistant.     

Selection on codon usage in Drosophila americana

Synonymous codons are not used at random, significantly influencing the base composition of the genome. The selection-mutation-drift model proposes that this bias reflects natural selection in favor of a subset of preferred codons. Previous estimates in Drosophila of the intensity of selective forces involved seem too large to be reconciled with theoretical predictions of the level of codon bias. This probably results from confounding effects of the demographic histories of the species concerned. We have studied three species of the virilis group of Drosophila, which are more likely to satisfy the assumptions of the evolutionary models. We analyzed the patterns of polymorphism and divergence in a sample of 18 genes and applied a new method for estimating the intensity of selection on synonymous mutations based on the frequencies of unpreferred mutations among polymorphic sites. This yielded estimates of selection intensities (N(e)s) of the order of 0.65, which is more compatible with the observed levels of codon bias. Our results support the action of both selection and mutational bias on codon usage bias and suggest that codon usage and genome base composition in the D. americana lineage are in approximate equilibrium. Biased gene conversion may also contribute to the observed patterns.     

Unusual binding mode of scorpion toxin BmKTX onto potassium channels relies on its distribution of acidic residues

Besides classical scorpion toxin–potassium channel binding modes, novel modes remain unknown. Here, we report a novel binding mode of native toxin BmKTX towards Kv1.3 channel. The combined experimental and computational data indicated that BmKTX-D33H analog used the classical anti-parallel β-sheet domain as the channel-interacting interface together with the conserved channel pore-blocking Lys²⁶. However, the wild-type BmKTX was found to use Arg²³ rather than Lys²⁶ as the new pore-blocking residue, and mainly adopt the turn motif between the α-helix and antiparallel β-sheet domains to recognize K_v1.3 channel. Together, these findings not only reveal that scorpion toxin–potassium channel interaction modes are more diverse than thought, but also highlight the functional role of toxin acidic residues in mediating diverse toxin–potassium channel binding modes.     

天蓝色链霉菌代谢物组测定方法优化及其代谢特征

链霉菌能够产生多种抗生素,具有重要的研究与应用价值。代谢物组学能够定性和定量测定胞内外主要低分子量代谢产物。相对于其他组学,代谢物组学在监控胞内代谢状态、指导物种理性改造方面具有独特优势。本文旨在建立一种快速、准确的链霉菌胞内代谢物分析方法。以模式菌株天蓝色链霉菌为研究对象,基于GC-MS分析平台优化了代谢物组学样品制备流程中的细胞淬灭时间、菌体分离方法、代谢物提取及代谢物衍生化条件,并利用该方法对天蓝色链霉菌不同生长时期各代谢途径的相对活性进行了初步分析。采用"低温淬灭(–40℃,4 min)-快速过滤分离-反复冻融(45 s/3 min)-衍生化(40℃,90 min)"的流程能够鉴定出中心代谢途径(糖酵解、戊糖磷酸途径和TCA循环)、氨基酸代谢途径、脂肪酸代谢途径、核酸代谢途径及部分次级代谢途径中的103种主要代谢物。利用该流程测定发现天蓝色链霉菌细胞生长周期中存在显著的代谢时序差异,并且发现氨基酸与脂肪酸代谢在衔接初级代谢与次级代谢生物合成中具有重要作用。本研究建立的测定方法能够有效地用于天蓝色链霉胞内代谢物分析,该方法将有助于深入刻画链霉菌细胞代谢过程,为菌株代谢工程改造增加次级代谢产物产量提供理性指导。