Dynamic regulation of T cell activation and co-stimulation through TCR-microclusters

Laboratory for Cell Signaling, RIKEN Research Center for Allergy and Immunology, Tsurumi-ku, Yokohama, Japan.
FEBS letters (Impact Factor: 3.17). 12/2010; 584(24):4865-71. DOI: 10.1016/j.febslet.2010.11.036
Source: PubMed


TCR-microclusters (MC) are generated upon TCR stimulation prior to the immune synapse formation independently of lipid rafts. TCR-MCs contain receptors, kinases and adaptors, and function as the signaling unit for T cell activation. The TCR complex, but not the signaling molecules, is transported to the center to form cSMAC. The co-stimulation receptor CD28 joins the signaling region of cSMAC and recruits PKCθ and Carma1. CTLA-4 accumulates in the same region and competes with CD28 for negative regulation of T cell activation. T cell activation is therefore mediated by two spatially distinct signaling compartments: TCR signaling by the peripheral TCR-MC and co-stimulation signal by the central signaling cSMAC.

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    • "Upon the formation of direct cell-cell interaction between T cells and antigen-presenting cells, some sequential and consecutive cellular events in immune synapses are known to precede signal transduction for T-cell activation. These cellular events include the formation of TCR microclusters, which accumulate at the central supramolecular activation complex, consisting of several adhesion and signaling molecules [17]. Therefore, it is quite reasonable to speculate that the properties of the cell membrane, in particular membrane fluidity, of T cells affect these dynamic movements of molecules on the T-cell membrane, and eventually affect T-cell function. "
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    ABSTRACT: Increase in body temperature has been thought to play an important role in the regulation of immune responses, although its precise mechanisms are still under investigation. Here, we examined the effects of physiologically relevant thermal stress on the cytokine production from human peripheral T cells. Volunteers were heated using a whole-body hyperthermia device, the rectal temperature was maintained above 38.5°C for more than 60min, and peripheral blood mononuclear cells (PBMCs) were obtained before and after the treatment. When T cells were stimulated with anti-CD3/CD28 antibodies, marked increases in the production of interferon-γ (IFN-γ) and interleukin-2 were observed in PBMCs prepared immediately after and 24h after the treatment. Similarly, enhanced production of IFN-γ in response to the tuberculin purified protein derivative or antigenic viral peptides was also observed immediately after and 24h after the treatment. Fluorescence photo-bleaching analyses showed heat-induced increase of membrane fluidity in T cells, which probably enables them to induce rapid and efficient cluster formation of molecules involved in antigen recognition and signal transduction for T-cell stimulation. We concluded that physiologically relevant thermal stress could efficiently modify T-cell responsiveness to various stimuli, including enhanced responses to specific antigens.
    09/2014; DOI:10.1016/j.imlet.2014.09.014
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    • "The formation of membrane-proximal protein clusters upon engagement of the T cell receptor (TCR) is a hallmark of early T cell signaling [1], [2], [3]. Cluster formation is the result of protein interactions, driven by phosphorylation of immunoreceptor tyrosine-based activation motifs (ITAMs) in the TCR complex itself and of tyrosines in scaffolding proteins such as the linker for activation of T cells (LAT) [4], [5], [6], [7] and reorganization of the cytoskeleton [8] but the exact mechanisms remain to be further elucidated [9]. "
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    ABSTRACT: T cell signaling is triggered through stimulation of the T cell receptor and costimulatory receptors. Receptor activation leads to the formation of membrane-proximal protein microclusters. These clusters undergo tyrosine phosphorylation and organize multiprotein complexes thereby acting as molecular signaling platforms. Little is known about how the quantity and phosphorylation levels of microclusters are affected by costimulatory signals and the activity of specific signaling proteins. We combined micrometer-sized, microcontact printed, striped patterns of different stimuli and simultaneous analysis of different cell strains with image processing protocols to address this problem. First, we validated the stimulation protocol by showing that high expression levels CD28 result in increased cell spreading. Subsequently, we addressed the role of costimulation and a specific phosphotyrosine phosphatase in cluster formation by including a SHP2 knock-down strain in our system. Distinguishing cell strains using carboxyfluorescein succinimidyl ester enabled a comparison within single samples. SHP2 exerted its effect by lowering phosphorylation levels of individual clusters while CD28 costimulation mainly increased the number of signaling clusters and cell spreading. These effects were observed for general tyrosine phosphorylation of clusters and for phosphorylated PLCγ1. Our analysis enables a clear distinction between factors determining the number of microclusters and those that act on these signaling platforms.
    PLoS ONE 10/2013; 8(10):e79277. DOI:10.1371/journal.pone.0079277 · 3.23 Impact Factor
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    • "Based on the distribution of TCR and CD28, the c-SMAC can be divided into two regions. TCRhigh regions contain no CD28 and show little or no signaling activity (Saito et al., 2010). These regions are rigid and are most likely areas of TCR endocytosis. "
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    ABSTRACT: Genetic and biochemical studies have identified a large number of molecules involved in T cell signaling. They have provided us with a comprehensive understanding of protein-protein interactions and protein modifications that take place upon antigen recognition. Diffraction limited fluorescence microscopy has been used to study the distribution of signaling molecules on a cellular level. Specifically, the discovery of microclusters and the immunological synapse demonstrates that T cell signaling cascades utilizes spatial association and segregation. Recent advancements in live cell imaging have allowed us to visualize the spatio-temporal mechanisms of T cell signaling at nanometer scale resolution. This led to the discovery that proteins are organized in distinct membrane domains prior and during T cell activation. Evidently, plasma membrane structures and signaling molecule distributions at all length scales (molecular to cellular) are intrinsic to the mechanisms that govern signaling initiation, transduction, and inhibition. Here we provide an overview of possible plasma membrane models, molecular assemblies that have been described to date, how they can be visualized and how they might contribute to T cell signaling.
    Frontiers in Immunology 09/2012; 3:291. DOI:10.3389/fimmu.2012.00291
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