Phospholipase Cγ1 is required for pre-TCR signal transduction and pre-T cell development

A lineage-specific requirement for YY1 Polycomb Group protein function in early T cell development

Yin Yang 1 (YY1) is a ubiquitous transcription factor and mammalian Polycomb Group protein (PcG) with important functions for regulating lymphocyte development and stem cell self-renewal. YY1 mediates stable PcG-dependent transcriptional repression via recruitment of PcG proteins that result in histone modifications. Many questions remain unanswered regarding how cell- and tissue-specificity is achieved by PcG proteins. Here, we demonstrate that a conditional knockout of Yy1 in the hematopoietic system results in an early T cell developmental blockage at the double negative (DN) 1 stage with reduced Notch1 signaling. There is a lineage-specific requirement for YY1 PcG function. YY1 PcG domain is required for T and B cell development but not necessary for myeloid cells. YY1 functions in early T cell development are multicomponent and involve both PcG-dependent and -independent regulations. Although YY1 promotes early T cell survival through its PcG function, its function to promote the DN1-to-DN2 transition and Notch1 expression and signaling is independent of its PcG function. Our results reveal how a ubiquitously expressed PcG protein mediates lineage-specific and context-specific functions to control early T cell development.

Neurokinin-1 Receptor Signaling Is Required for Efficient Ca2+ Flux in T-Cell-Receptor-Activated T Cells

Efficient Ca²⁺ flux induced during cognate T cell activation requires signaling the T cell receptor (TCR) and unidentified G-protein-coupled receptors (GPCRs). T cells express the neurokinin-1 receptor (NK1R), a GPCR that mediates Ca²⁺ flux in excitable and non-excitable cells. However, the role of the NK1R in TCR signaling remains unknown. We show that the NK1R and its agonists, the neuropeptides substance P and hemokinin-1, co-localize within the immune synapse during cognate activation of T cells. Simultaneous TCR and NK1R stimulation is necessary for efficient Ca²⁺ flux and Ca²⁺-dependent signaling that sustains the survival of activated T cells and helper 1 (Th1) and Th17 bias. In a model of contact dermatitis, mice with T cells deficient in NK1R or its agonists exhibit impaired cellular immunity, due to high mortality of activated T cells. We demonstrate an effect of the NK1R in T cells that is relevant for immunotherapies based on pro-inflammatory neuropeptides and its receptors.

The neurokinin 1 receptor (NK1R) induces Ca²⁺ flux in excitable cells. Here, Morelli et al. show that NK1R signaling in T cells promotes optimal Ca²⁺ flux triggered by TCR stimulation, which is necessary to sustain T cell survival and the efficient Th1- and Th17-based immunity that is relevant for immunotherapies based on pro-inflammatory neuropeptides.

Potential role of diacylglycerol kinases in immune-mediated diseases

The mechanism promoting exacerbated immune responses in allergy and autoimmunity as well as those blunting the immune control of cancer cells are of primary interest in medicine. Diacylglycerol kinases (DGKs) are key modulators of signal transduction, which blunt diacylglycerol (DAG) signals and produce phosphatidic acid (PA). By modulating lipid second messengers, DGK modulate the activity of downstream signaling proteins, vesicle trafficking and membrane shape. The biological role of the DGK α and ζ isoforms in immune cells differentiation and effector function was subjected to in deep investigations. DGK α and ζ resulted in negatively regulating synergistic way basal and receptor induced DAG signals in T cells as well as leukocytes. In this way, they contributed to keep under control the immune response but also downmodulate immune response against tumors. Alteration in DGKα activity is also implicated in the pathogenesis of genetic perturbations of the immune function such as the X-linked lymphoproliferative disease 1 and localized juvenile periodontitis. These findings suggested a participation of DGK to the pathogenetic mechanisms underlying several immune-mediated diseases and prompted several researches aiming to target DGK with pharmacologic and molecular strategies. Those findings are discussed inhere together with experimental applications in tumors as well as in other immune-mediated diseases such as asthma.

Protein 4.1R negatively regulates CD8+ T-cell activation by modulating phosphorylation of linker for activation of T cells

Protein 4.1R, an 80 000 MW membrane skeleton protein, is a vital component of the red blood cell membrane cytoskeleton that stabilizes the spectrin-actin network and regulates membrane properties of deformability and mechanical stability. It has been shown that 4.1R is expressed in T cells, including CD8⁺ T cells, but its role in CD8⁺ T cells remains unclear. Here, we have explored the role of 4.1R in CD8⁺ T cells using 4.1R^-/- mice. Our results showed that cell activation, proliferation and secretion levels of interleukin-2 and interferon-γ were significantly increased in 4.1R^-/- CD8⁺ T cells. Furthermore, the phosphorylation levels of linker for activation of T cells (LAT) and its downstream signaling molecule extracellular signal-regulated kinase were enhanced in the absence of 4.1R. In vitro co-immunoprecipitation experiments showed a direct interaction between 4.1R and LAT. Moreover, 4.1R^-/- CD8⁺ T cells and mice exhibited an enhanced T-cell-dependent immune response. These data enabled the identification of a negative regulation function for 4.1R in CD8⁺ T cells by a direct association between 4.1R and LAT, possibly through inhibiting phosphorylation of LAT and then modulating intracellular signal transduction.