A Novel Mechanism for the Autonomous Termination of Pre-B Cell Receptor Expression via Induction of Lysosome-Associated Protein Transmembrane 5

The expression of the pre-B cell receptor (BCR) is confined to the early stage of B cell development, and its dysregulation is associated with anomalies of B-lineage cells, including leukemogenesis. Previous studies suggested that the pre-BCR signal might trigger the autonomous termination of pre-BCR expression even before the silencing of pre-BCR gene expression to prevent sustained pre-BCR expression. However, the underlying mechanism remains ill defined. Here we demonstrate that the pre-BCR signal induces the expression of lysosome-associated protein transmembrane 5 (LAPTM5), which leads to the prompt downmodulation of the pre-BCR. While LAPTM5 induction had no significant impact on the internalization of cell surface pre-BCR, it elicited the translocation of a large pool of intracellular pre-BCR from the endoplasmic reticulum to the lysosomal compartment concomitantly with a drastic reduction of the level of intracellular pre-BCR proteins. This reduction was inhibited by lysosomal inhibitors, indicating the lysosomal degradation of the pre-BCR. Notably, the LAPTM5 deficiency in pre-B cells led to the augmented expression level of surface pre-BCR. Collectively, the pre-BCR induces the prompt downmodulation of its own expression through the induction of LAPTM5, which promotes the lysosomal transport and degradation of the intracellular pre-BCR pool and, hence, limits the supply of pre-BCR to the cell surface.     

Role of Amphipathic Helix of a Herpesviral Protein in Membrane Deformation and T Cell Receptor Downregulation

Lipid rafts are membrane microdomains that function as platforms for signal transduction and membrane trafficking. Tyrosine kinase interacting protein (Tip) of T lymphotropic Herpesvirus saimiri (HVS) is targeted to lipid rafts in T cells and downregulates TCR and CD4 surface expression. Here, we report that the membrane-proximal amphipathic helix preceding Tip''s transmembrane (TM) domain mediates lipid raft localization and membrane deformation. In turn, this motif directs Tip''s lysosomal trafficking and selective TCR downregulation. The amphipathic helix binds to the negatively charged lipids and induces liposome tubulation, the TM domain mediates oligomerization, and cooperation of the membrane-proximal helix with the TM domain is sufficient for localization to lipid rafts and lysosomal compartments, especially the mutivesicular bodies. These findings suggest that the membrane-proximal amphipathic helix and TM domain provide HVS Tip with the unique ability to deform the cellular membranes in lipid rafts and to downregulate TCRs potentially through MVB formation.     

生长抑素受体在人神经内分泌癌组织中的表达及受体激活对细胞生长的抑制

生长抑素（somatostatin,SST）通过与细胞膜上的G蛋白偶联的生长抑素受体（somatostatin receptors,SSTRs）结合而发挥其抑制细胞增殖的作用,因而生长抑素类似物（somatostatin analogue, SSA）常被用于肿瘤辅助治疗。然而,治疗效果存在相当大的个体差异,推测生长抑素类似物治疗效果不佳,与内源性生长抑素受体表达缺失或者表达量和亚型组合有关。为此,检测各亚型SSTR在几例罕见的神经内分泌肿瘤中的表达,并检测过表达SSTR2和SSTR5以及受体激活对细胞增殖的抑制效果,分析受体激活的可能机制,有助于临床筛选适合SSA肿瘤辅助治疗的病例,预估SSA的治疗效果。免疫组化检测肿瘤组织SSTR1-5的表达。在培养的293T细胞中过表达SSTR2和SSTR5,免疫共沉淀检测受体相互作用,免疫荧光和共聚焦显微镜检测受体细胞内定位。用MTT法检测受体过表达及激活对培养的人肺癌细胞NCI-H460细胞增殖的影响,用流式细胞技术检测细胞周期分布。SSTR1-5在10例神经内分泌肿瘤组织中均有不同程度的表达,表达亚型及表达量与肿瘤类型和年龄无关,SSTR5在所有肿瘤组织中均表达。SSTR2与SSTR5可形成受体相互作用。SSTR2与SSTR5活化后相互作用增加并定位于细胞质。共表达SSTR2和SSTR5显著抑制细胞增殖,并与受体激活剂呈现剂量相关性。SSTR2/SSTR5的共表达及激活显著减少S期的细胞而滞留于G₁期。     

sHLA-G在子痫前期患者的表达及意义

目的：检测子痫前期患者sHLA—G水平,探讨母血sHLA—G的水平和妊娠高血压疾病的关系。方法：采用酶联免疫吸附法检测20例正常孕妇晚期和20例子痫前期患者血清sHLA—G水平。结果：在正常妊娠组sHLA—G血清中的水平为10．72±3.40ng／mL;子痫前期组为9.46±1.5．10ng／mL。子痫前期组sHLA—G水平明显低于正常妊娠晚期组,差异有显著性意义（P〈0．05）。结论：sHLA-G可能与子痫前期患者的发病有关系。     

Multiplex Identification of Antigen-Specific T Cell Receptors Using a Combination of Immune Assays and Immune Receptor Sequencing

Monitoring antigen-specific T cells is critical for the study of immune responses and development of biomarkers and immunotherapeutics. We developed a novel multiplex assay that combines conventional immune monitoring techniques and immune receptor repertoire sequencing to enable identification of T cells specific to large numbers of antigens simultaneously. We multiplexed 30 different antigens and identified 427 antigen-specific clonotypes from 5 individuals with frequencies as low as 1 per million T cells. The clonotypes identified were validated several ways including repeatability, concordance with published clonotypes, and high correlation with ELISPOT. Applying this technology we have shown that the vast majority of shared antigen-specific clonotypes identified in different individuals display the same specificity. We also showed that shared antigen-specific clonotypes are simpler sequences and are present at higher frequencies compared to non-shared clonotypes specific to the same antigen. In conclusion this technology enables sensitive and quantitative monitoring of T cells specific for hundreds or thousands of antigens simultaneously allowing the study of T cell responses with an unprecedented resolution and scale.     

CCR7 在树突状细胞中的功能及对角膜免疫调节的研究进展

树突状细胞(dendritic cells, DCs)是体内已知的功能最强大的专职抗原提呈细胞,对于诱导机体初始免疫应答尤为重要。趋 化受体因子7 (chemokine receptor 7,CCR7)是一个已知的调节各类免疫细胞向初级、次级淋巴细胞分化,并向外周淋巴器官归巢 的趋化因子受体,其具有自我平衡表达能力,在趋化DCs 从外周组织迁移至次级淋巴器官中起关键作用。随着研究的深入,除了 CCR7 最主要的趋化作用外,更多的功能逐渐被了解。目前,DCs 和CCR7 的相关功能已被应用于诱导角膜移植后的免疫耐受等 眼科领域。就CCR7 在DCs中的功能及其对角膜免疫调节的影响进行综述,探讨其关键作用及可能的治疗靶点。     

CCR7在树突状细胞中的功能及对角膜免疫调节的研究进展

树突状细胞（dendritic cells,DCs）是体内已知的功能最强大的专职抗原提呈细胞,对于诱导机体初始免疫应答尤为重要。趋化受体因子7（chemokine receptor 7,CCR7）是一个已知的调节各类免疫细胞向初级、次级淋巴细胞分化,并向外周淋巴器官归巢的趋化因子受体,其具有自我平衡表达能力,在趋化DCs从外周组织迁移至次级淋巴器官中起关键作用。随着研究的深入,除了CCR7最主要的趋化作用外,更多的功能逐渐被了解。目前,DCs和CCR7的相关功能已被应用于诱导角膜移植后的免疫耐受等眼科领域。就CCR7在DCs中的功能及其对角膜免疫调节的影响进行综述,探讨其关键作用及可能的治疗靶点。     

Tailored Immune Responses: Novel Effector Helper T Cell Subsets in Protective Immunity

Differentiation of naïve CD4⁺ cells into functionally distinct effector helper T cell subsets, characterised by distinct “cytokine signatures,” is a cardinal strategy employed by the mammalian immune system to efficiently deal with the rapidly evolving array of pathogenic microorganisms encountered by the host. Since the T_H1/T_H2 paradigm was first described by Mosmann and Coffman, research in the field of helper T cell biology has grown exponentially with seven functionally unique subsets having now been described. In this review, recent insights into the molecular mechanisms that govern differentiation and function of effector helper T cell subsets will be discussed in the context of microbial infections, with a focus on how these different helper T cell subsets orchestrate immune responses tailored to combat the nature of the pathogenic threat encountered.     

Inhibitory NK Receptor Recognition of HLA-G: Regulation by Contact Residues and by Cell Specific Expression at the Fetal-Maternal Interface

The non-classical HLA-G protein is distinguished from the classical MHC class I molecules by its expression pattern, low polymorphism and its ability to form complexes on the cell surface. The special role of HLA-G in the maternal-fetal interface has been attributed to its ability to interact with specific receptors found on maternal immune cells. However this interaction is restricted to a limited number of receptors. In this study we elucidate the reason for this phenomenon by comparing the specific contact residues responsible for MHC-KIR interactions. This alignment revealed a marked difference between the HLA-G molecule and other MHC class I molecules. By mutating these residues to the equivalent classical MHC residues, the HLA-G molecule regained an ability of interacting with KIR inhibitory receptors found on NK cells derived either from peripheral blood or from the decidua. Functional NK killing assays further substantiated the binding results. Furthermore, double immunofluorescent staining of placental sections revealed that while the conformed form of HLA-G was expressed in all extravillous trophoblasts, the free heavy chain form of HLA-G was expressed in more distal cells of the column, the invasion front. Overall we suggest that HLA-G protein evolved to interact with only some of the NK inhibitory receptors thus allowing a control of inhibition, while permitting appropriate NK cell cytokine and growth factor production necessary for a viable maternal fetal interface.     

Modulation of NMDA Receptor Subunits Expression by Concanavalin A

The processes of N-methyl-d-aspartate (NMDA) receptor subunits expression were examined in cortical neurons and rat brain in order to investigate how the concanavalin A (Con A) modulates neuronal cells. Con A modulated the expression of NMDA receptor subunits in cultured cortical cells. Con A augmented the level of intracellular Ca²⁺ by α-amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA). We determined whether activation of AMPA receptors was involved in the regulation of NMDA receptor expression with Con A by blocking the desensitization of AMPA receptors. The results showed that AMPA receptor antagonists suppressed NMDA receptor subunits expression in Con A-treated cortical neuronal cells. PMA elevated the expression of NMDA receptor subunits, while PKC inhibitor and tyrosine kinases inhibitor suppressed the expression of NMDA receptor subunits. Furthermore, it was shown that NMDA receptor subunits expression was modulated in a region-specific manner after the sustained microinfusion of Con A into the cerebroventricle of the rat brain. Collectively, it could be presumed that the AMPA receptor activation was involved in Con A-induced modulation of NMDA receptor subunits expression.     

Dynamics of Membrane Trafficking Downstream of B and T Cell Receptor Engagement: Impact on Immune Synapses

The onset of an adaptive immune response requires the activation of T and B lymphocytes by antigen-presenting cells, through a specialized form of intercellular communication, known as the immunological synapse (IS). In B lymphocytes the IS promotes efficient recognition and acquisition of membrane-bound Ags, while in T cells, it modulates the T cell response upon exposure to peptide-major histocompatibility complexes. In this review, we highlight the similarities that determine B and T cell activation, focusing on immune receptor downstream signaling events that lead to synapse formation. We stress the notion that polarization of T and B lymphocytes characterized by global changes in cytoskeleton and membrane trafficking modulates synapse structure and function, thus determining lymphocyte effector functions and fate.     

人趋化因子受体CXCR4基因的克隆及原核表达

目的:构建人CXCR4原核表达载体并在大肠杆菌中进行表达。方法:从健康人外周血单个核细胞提取总RNA,以RT-PCR获得CXCR4基因全长1059bp的完整编码序列,将其克隆入载体pMD-18T中,经限制性内切酶和菌落PCR分析并测序证实的阳性重组子与表达载体pET-28a( )连接并转化大肠杆菌BL21(DE3)。结果:12%SDS-PAGE分析表明,在30℃以IPTG诱导获得分子量为43ku的His-CXCR4融合蛋白表达带,诱导4h后此蛋白表达量约为全菌总蛋白的25%。结论:成功获得人CXCR4基因融合蛋白。     

Assessment of T Cell Receptor Complex Expression Kinetics in Natural Killer Cells

Among the polypeptides that comprise the T cell receptor (TCR), only CD3ζ is found in Natural Killer (NK) cells, where it transmits signals from activating receptors such as CD16 and NKp46. NK cells are potent immune cells that recognize target cells through germline-encoded activating and inhibitory receptors. Genetic engineering of NK cells enables tumor-specific antigen recognition and, thus, has a significant promise in adoptive cell therapy. Ectopic expression of engineered TCR components in T cells leads to mispairing with the endogenous components, making a knockout of the endogenous TCR necessary. To circumvent the mispairing of TCRs or the need for knockout technologies, TCR complex expression has been studied in NK cells. In the current study, we explored the cellular processing of the TCR complex in NK cells. We observed that in the absence of CD3 subunits, the TCR was not expressed on the surface of NK cells and vice versa. Moreover, a progressive increase in surface expression of TCR between day three and day seven was observed after transduction. Interestingly, the TCR complex expression in NK92 cells was enhanced with a proteasome inhibitor (bortezomib) but not a lysosomal inhibitor (chloroquine). Additionally, we observed that the TCR complex was functional in NK92 cells as measured by estimating CD107a as a degranulation marker, IFNγ cytokine production, and killing assays. NK92 cells strongly degranulated when CD3ε was engaged in the presence of TCR, but not when only CD3 was overexpressed. Therefore, our findings encourage further investigation to unravel the mechanisms that prevent the surface expression of the TCR complex.     

Modulation of Cell Surface Protein Free Thiols: A Potential Novel Mechanism of Action of the Sesquiterpene Lactone Parthenolide

Background

There has been much interest in targeting intracellular redox pathways as a therapeutic approach for cancer. Given recent data to suggest that the redox status of extracellular protein thiol groups (i.e. exofacial thiols) effects cell behavior, we hypothesized that redox active anti-cancer agents would modulate exofacial protein thiols.

Methodology/Principal Findings

To test this hypothesis, we used the sesquiterpene lactone parthenolide, a known anti-cancer agent. Using flow cytometry, and western blotting to label free thiols with Alexa Fluor 633 C₅ maleimide dye and N-(biotinoyl)-N-(iodoacetyl) ethylendiamine (BIAM), respectively, we show that parthenolide decreases the level of free exofacial thiols on Granta mantle lymphoma cells. In addition, we used immuno-precipitation techniques to identify the central redox regulator thioredoxin, as one of the surface protein thiol targets modified by parthenolide. To examine the functional role of parthenolide induced surface protein thiol modification, we pretreated Granta cells with cell impermeable glutathione (GSH), prior to exposure to parthenolide, and showed that GSH pretreatment; (a) inhibited the interaction of parthenolide with exofacial thiols; (b) inhibited parthenolide mediated activation of JNK and inhibition of NFκB, two well established mechanisms of parthenolide activity and; (c) blocked the cytotoxic activity of parthenolide. That GSH had no effect on the parthenolide induced generation of intracellular reactive oxygen species supports the fact that GSH had no effect on intracellular redox. Together these data support the likelihood that GSH inhibits the effect of parthenolide on JNK, NFκB and cell death through its direct inhibition of parthenolide''s modulation of exofacial thiols.

Conclusions/Significance

Based on these data, we postulate that one component of parthenolide''s anti-lymphoma activity derives from its ability to modify the redox state of critical exofacial thiols. Further, we propose that cancer cell exofacial thiols may be important and novel targets for therapy.