STAT3 couples with 14-3-3σ to regulate BCR signaling,B-cell differentiation,and IgE production

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上皮间质转化(EMT)及其分子机制

上皮细胞受到细胞外因子刺激后向间质细胞转化的现象与肿瘤的浸润转移密切相关。在此过程中上皮细胞的极性丧失，迁移和运动能力增强，同时上皮表型丢失而逐渐获得间质表型。参与这一过程的细胞内信号转导途径有受体酪氨酸激酶Ras-MAPK途径，Src激酶，Rho家族激酶，PI3K/AKT途径，Wnt信号通路，转录因子等。     

Signal-dependent wavelets for electromyogram classification

In the study, an efficient method to perform supervised classification of surface electromyogram (EMG) signals is proposed. The method is based on the choice of a relevant representation space and its optimisation with respect to a training set. As EMG signals are the summation of compact-support waveforms (the motor unit action potentials), a natural tool for their representation is the discrete dyadic wavelet transform. The feature space was thus built from the marginals of a discrete wavelet decomposition. The mother wavelet was designed to minimise the probability of classification error estimated on the learning set (supervised classification). As a representative example, the method was applied to simulate surface EMG signals generated by motor units with different degrees of short-term synchronisation. The proposed approach was able to distinguish surface EMG signals with degrees of synchronisation that differed by 10%, with a misclassification rate of 8%. The performance of a spectral-based classification (error rate approximately 33%) and of the classification with Daubechies wavelet (21%) was significantly poorer than with the proposed wavelet optimisation. The method can be used for a number of different application fields of surface EMG classification, as the feature space is adapted to the characteristics of the signal that discriminate between classes. An erratum to this article is available at .     

尿激酶型纤溶酶原激活物系统对骨巨细胞瘤细胞基质金属蛋白酶-2和组织基质金属蛋白酶抑制物-3表达的影响

目的:研究尿激酶型纤溶酶原激活物(uPA)及其受体(uPAR)信号转导对骨巨细胞瘤基质金属蛋白酶-2(MMP-2)和金属蛋白酶组织抑制物-3(TIMP-3)的调节。方法:用免疫组化检测骨巨细胞瘤组织中uPAR、MMP-2和TIMP-3的表达。用免疫共沉淀法检测uPA对瘤细胞信号转导通路的p44蛋白磷酸化水平。用蛋白印迹法检测用uPA和uPAR抗体处理后瘤细胞MMP-2和TIMP-3蛋白表达。结果:(1)uPAR主要表达在部分单核基质细胞和一些多核巨细胞的胞膜上;(2)MMP-2主要表达在瘤细胞的胞浆,在多核巨细胞,其表达有明显的极向性;(3)在骨巨细胞瘤组织TIMP-3表达量低于MMP-2,在多核巨细胞也显示极向性表达;(4)将uPA-ATF加入培养的骨巨细胞瘤细胞后,细胞信号通路上的p44蛋白磷酸化水平明显增高。用uPAR抗体处理后,细胞p44蛋白磷酸化水平明显降低。说明uPA-ATF参与细胞信号转导,而且受uPAR拮抗剂的影响;(5)uPA-ATF信号通路上调MMP-2和TIMP-3的表达,而uPAR抗体则下调MMP-2和TIMP-3的表达。结论:本实验首次直接证明uPA-ATF通过信号转导能调节MMP-2和TIMP-3的表达,而后者则在骨巨细胞瘤局部骨质吸收中起重要作用。     

T cell receptor induced intracellular redistribution of type I protein kinase A

The productive activation of CD4(+) T lymphocytes, leading to proliferation and cytokine secretion, requires precise temporal regulation of intracellular cyclic AMP concentrations. The major effector molecule activated by cyclic AMP in mammalian cells is the cyclic AMP-dependent protein kinase A (PKA). The type I PKA isozyme mediates the inhibitory effects of cyclic AMP on T-cell activation. Using laser scanning confocal microscopy, we demonstrated that the regulation of PKA type I activity involves spatial redistribution of PKA type I molecules following T-cell receptor (TCR) stimulation. In resting T cells, PKA type I was located in membrane proximal regions and distributed equally across the cell. Shortly after antigen engagement, T cells and antigen-presenting cells formed an area of intense contact, known as the immunological synapse. TCR concentrated at the synapse, whereas PKA type I molecules redistributed to the opposite cell pole within 10 min after T-cell stimulation. Type I PKA redistribution was solely dependent on TCR signalling, because we observed the same temporal and spatial distribution after antibody-mediated cross-linking of the TCR-associated CD3 complex. Segregation of TCR and PKA type I molecules was maintained for at least 20 min. Thirty minutes after stimulation, PKA type I partially colocalized with the TCR. After 60 min, PKA type I distribution again approached the resting state. Considering that initial TCR signals lead to increases in intracellular cyclic AMP, PKA type I molecules may be targeted towards localized cyclic AMP accumulations or transported away from these areas, depending on the requirements of the cellular response.     

Physiological mechanisms of TRPC activation

TRPC (canonical transient receptor potential) channels are vertebrate homologs of the Drosophila photoreceptor channel, TRP. Considerable research has been brought to bear on the seven members of this family, especially with regard to their possible role in calcium entry. Unfortunately, the current literature presents a confusing picture, with different laboratories producing widely differing results and interpretations. It appears that ectopically expressed TRPC channels can be activated by phospholipase C products (generally, diacylglycerols), by stimulation of trafficking to the plasma membrane, or by depletion of intracellular Ca²⁺ stores. Here, I discuss the possibility that these diverse experimental findings arise because TRPC channels can, under both experimental as well as physiological conditions, be activated in three distinct ways, possibly depending on their subunit composition and/or signaling complex environment. The TRPCs may be unique among ion-channel subunit families in being able to participate in the assembly and function of multiple types of physiologically important ion channels.     

Angiotensin-(1-7)对血管平滑肌细胞钙化的影响及信号转导通路

目的:在钙化大鼠主动脉血管平滑肌细胞上观察血管紧张素-(1-7)[Angiotensin-(1-7)]对钙化的影响及其信号通道。方法:用β-磷酸甘油制备钙化的大鼠血管平滑肌细胞,再以血管紧张素-(1-7)、血管紧张素Ⅱ、血管紧张素Ⅱ 血管紧张素-(1-7)、选择性蛋白激酶A(PKA)或蛋白激酶C(PKC)抑制剂等干预,通过Von Kossa染色及检测钙含量、碱性磷酸酶活性、骨钙素浓度和Cbfa1 mRNA表达来探讨血管紧张素Ⅱ对钙化的影响及其信号通道。结果:血管紧张素-(1-7)抑制钙化大鼠血管平滑肌细胞的钙含量、碱性磷酸酶活性(P>0.05)、骨钙素浓度和Cbfa1 mRNA表达(P<0.05),也抑制血管紧张素Ⅱ对血管平滑肌细胞的钙含量、碱性磷酸酶活性、骨钙素浓度和Cbfa1 mRNA表达的促进作用(P<0.05);血管紧张素-(1-7)提高血管平滑肌细胞内cAMP浓度(P<0.05),PKA抑制剂可阻断血管紧张素-(1-7)对钙化血管平滑肌细胞的钙含量、碱性磷酸酶活性、骨钙素浓度和Cbfa1 mRNA表达的抑制作用(P<0.05)。结论:血管紧张素-(1-7)可抑制β-磷酸甘油诱导的血管平滑肌细胞钙化,并拮抗血管紧张素Ⅱ促进的血管平滑肌细胞钙化;这些效应与cAMP-PKA-Cbfa1信号途径有关。     

Internalization of extraintestinal Escherichia coli O18 strains by epithelial cells is modulated by EGF, insulin, and effectors of transmembrane signal transduction

Adhesion to and internalization into host cells is an essential step in the pathogenesis of various bacterial infections. Here we investigated the effects of growth factors on the internalization of Escherichia coli O18 strains isolated from patients with urinary tract infection (UTI) by human epithelial cells. A dramatic increase in the uptake of Escherichia coli was observed after treatment of epithelial cells with epidermal growth factor (EGF) and to a lower extent with insulin. EGF-dependent internalization can be suppressed by tyrosine kinase inhibitors suggesting an involvement of the receptor tyrosine kinases in the regulation of the endocytotic process. Inhibitors of phospholipase A2, lipoxygenase, and cyclooxygenase significantly decreased internalization of bacteria induced by EGF. Finally, the specific inhibitor of PI 3-kinases Wortmannin was shown to suppress completely the EGF-independent internalization. The data of this analysis indicate the involvement of several signaling paths in bacterial internalization of uropathogenic Escherichia coli O18 strains and contribute to the comprehension of the pathogenesis of recurrent UTI.     

Cloning and sequence analysis of the glucoamylase gene of Neurospora crassa

A 1.0-kb DNA fragment, corresponding to an internal region of the Neurospora crassa glucoamylase gene, gla-1, was generated from genomic DNA by the polymerase chain reaction, using oligonucleotide primers which had been deduced from the known N-terminal amino-acid sequence or from consensus regions within the aligned amino-acid sequences of other fungal glucoamylases. The fragment was used to screen an N. crassa genomic DNA library. One clone contained the gene together with flanking regions and its sequence was determined. The gene was found to code for a preproprotein of 626 amino acids, 35 of which constitute a signal and propeptide region. The protein and the gene are compared with corresponding sequences in other fungi.