Essential role of LAT in T cell development

Redox Regulation of LAT Enhances T Cell-Mediated Inflammation

The positional cloning of single nucleotide polymorphisms (SNPs) of the neutrophil cytosolic factor 1 (Ncf1) gene, advocating that a low oxidative burst drives autoimmune disease, demands an understanding of the underlying molecular causes. A cellular target could be T cells, which have been shown to be regulated by reactive oxygen species (ROS). However, the pathways by which ROS mediate T cell signaling remain unclear. The adaptor molecule linker for activation of T cells (LAT) is essential for coupling T cell receptor-mediated antigen recognition to downstream responses, and it contains several cysteine residues that have previously been suggested to be involved in redox regulation. To address the possibility that ROS regulate T cell-dependent inflammation through LAT, we established a mouse strain with cysteine-to-serine mutations at positions 120 and 172 (LATSS). We found that redox regulation of LAT through C120 and C172 mediate its localization and phosphorylation. LATSS mice had reduced numbers of double-positive thymocytes and naïve peripheral T cells. Importantly, redox insensitivity of LAT enhanced T cell-dependent autoimmune inflammation in collagen-induced arthritis (CIA), a mouse model of rheumatoid arthritis (RA). This effect was reversed on an NCF1-mutated (NCF1m1j), ROS-deficient, background. Overall, our data show that LAT is redox-regulated, acts to repress T cell activation, and is targeted by ROS induced by NCF1 in antigen-presenting cells (APCs).

Influence of different conjugation methods for activating antibodies on polymeric nanoparticles: Effects for polyclonal expansion of human CD8+ T cells

Particle-based systems have become a state-of-the-art method for in vitro expanding cytotoxic T cells by tailoring their surface with activating molecules. However, commonly used methods utilize facile carbodiimide chemistry leading to uncontrolled orientation of the immobilized antibodies on the particle surface that can lead to poor binding to target cells. To address this, selective coupling strategies utilizing regioselective chemical groups such as disulfide bridges offer a simple approach. In this work we present a set of methods to investigate the effect of polymeric nanoparticles, conjugated with either regioselective- or randomly-immobilized antiCD3 and antiCD28 antibodies, on the activation potential, expansion and expression of activation markers in T cells. We show that nanoparticles with well-oriented monovalent antibodies conjugated via maleimide require fewer ligands on the surface to efficiently expand T cells compared to bivalent antibodies randomly-immobilized via carbodiimide conjugation. Analysis of the T cell expression markers reveal that the T cell phenotype can be fine-tuned by adjusting the surface density of well-oriented antibodies, while randomly immobilized antibodies showed no differences despite their ligand density. Both conjugation techniques induced cytotoxic T cells, evidenced by analyzing their Granzyme B secretion. Furthermore, antibody orientation affects the immunological synapse and T cell activation by changing the calcium influx profile upon activation. Nanoparticles with well-oriented antibodies showed lower calcium influx compared to their bivalent randomly-immobilized counterparts. These results highlight the importance of controlling the antibody density and orientation on the nanoparticle surface via controlled coupling chemistries, helping to develop improved particle-based expansion protocols to enhance T cell therapies.

[Understanding New Regulatory Mechanism of TCR Signal Transduction]

Signal-transducing adaptor protein-2 (STAP-2) is a unique scaffold protein that regulates several immunological signaling pathways, including LIF/LIF receptor and LPS/TLR4 signals. STAP-2 is required for Fas/FasL-dependent T cell apoptosis and SDF-1α-induced T cell migration. Conversely, STAP-2 modulates integrin-mediated T cell adhesion, suggesting that STAP-2 is essential for several negative and positive T cell functions. However, whether STAP-2 is involved in T cell-antigen receptor (TCR)-mediated T cell activation is unknown. STAP-2 deficiency was recently reported to suppress TCR-mediated T cell activation by inhibiting LCK-mediated CD3ζ and ZAP-70 activation. Using STAP-2 deficient mice, it was demonstrated that STAP-2 is required for the pathogenesis of Propionibacterium acnes-induced granuloma formation and experimental autoimmune encephalomyelitis. Here, detailed functions of STAP-2 in TCR-mediated T cell activation, and how STAP-2 affects the pathogenesis of T cell-mediated inflammation and immune diseases, are reviewed.

TCR Signals Controlling Adaptive Immunity against Toxoplasma and Cancer

T cells play a crucial role in adaptive immunity by recognizing and eliminating foreign pathogens and abnormal cells such as cancer cells. T cell receptor (TCR), which is expressed on the surface of T cells, recognizes and binds to specific antigens presented by major histocompatibility complex (MHC) molecules on antigen-presenting cells (APCs). This activation process leads to the proliferation and differentiation of T cells, allowing them to carry out their specific immune response functions. This chapter outlines the TCR signaling pathways that are common to different T cell subsets, as well as the recently elucidated TCR signaling pathway specific to CD8+ T cells and its role in controlling anti-Toxoplasma and anti-tumor immunity.

Integrated omics analysis of coronary artery calcifications and myocardial infarction: the Framingham Heart Study

Gene function can be described using various measures. We integrated association studies of three types of omics data to provide insights into the pathophysiology of subclinical coronary disease and myocardial infarction (MI). Using multivariable regression models, we associated: (1) single nucleotide polymorphism, (2) DNA methylation, and (3) gene expression with coronary artery calcification (CAC) scores and MI. Among 3106 participants of the Framingham Heart Study, 65 (2.1%) had prevalent MI and 60 (1.9%) had incident MI, median CAC value was 67.8 [IQR 10.8, 274.9], and 1403 (45.2%) had CAC scores > 0 (prevalent CAC). Prevalent CAC was associated with AHRR (linked to smoking) and EXOC3 (affecting platelet function and promoting hemostasis). CAC score was associated with VWA1 (extracellular matrix protein associated with cartilage structure in endomysium). For prevalent MI we identified FYTTD1 (down-regulated in familial hypercholesterolemia) and PINK1 (linked to cardiac tissue homeostasis and ischemia-reperfusion injury). Incident MI was associated with IRX3 (enhancing browning of white adipose tissue) and STXBP3 (controlling trafficking of glucose transporter type 4 to plasma). Using an integrative trans-omics approach, we identified both putatively novel and known candidate genes associated with CAC and MI. Replication of findings is warranted.

A Story of Kinases and Adaptors: The Role of Lck, ZAP-70 and LAT in Switch Panel Governing T-Cell Development and Activation

Specific antigen recognition is one of the immune system's features that allows it to mount intense yet controlled responses to an infinity of potential threats. T cells play a relevant role in the host defense and the clearance of pathogens by means of the specific recognition of peptide antigens presented by antigen-presenting cells (APCs), and, to do so, they are equipped with a clonally distributed antigen receptor called the T-cell receptor (TCR). Upon the specific engagement of the TCR, multiple intracellular signals are triggered, which lead to the activation, proliferation and differentiation of T lymphocytes into effector cells. In addition, this signaling cascade also operates during T-cell development, allowing for the generation of cells that can be helpful in the defense against threats, as well as preventing the generation of autoreactive cells. Early TCR signals include phosphorylation events in which the tyrosine kinases Lck and ZAP70 are involved. The sequential activation of these kinases leads to the phosphorylation of the transmembrane adaptor LAT, which constitutes a signaling hub for the generation of a signalosome, finally resulting in T-cell activation. These early signals play a relevant role in triggering the development, activation, proliferation and apoptosis of T cells, and the negative regulation of these signals is key to avoid aberrant processes that could generate inappropriate cellular responses and disease. In this review, we will examine and discuss the roles of the tyrosine kinases Lck and ZAP70 and the membrane adaptor LAT in these cellular processes.

Clinical, immunological and molecular findings of 8 patients with typical and atypical severe combined immunodeficiency: identification of 7 novel mutations by whole exome sequencing

Severe combined immunodeficiency (SCID) is one of the severe inborn errors of the immune system associated with life-threatening infections. Variations in SCID phenotypes, especially atypical SCID, may cause a significant delay in diagnosis. Therefore, SCID patients need to receive an early diagnosis. Here, we describe the clinical manifestations and genetic results of four SCID and atypical SCID patients. All patients (4 males and 4 females) in early infancy presented with SCID phenotypes within 6 months of birth. The mutations include RAG2 (p.I273T,p.G44X), IL7R (p.F361WfsTer17), ADA (c.780+1G>A), JAK3 (p.Q228Ter), LIG4 (p.G428R), and LAT (p.Y207fsTer33), as well as a previously reported missense mutation in RAG1 (p.A444V). The second report of LAT deficiency in SCID patients is presented in this study. Moreover, all variants were confirmed in patients and their parents as a heterozygous state by Sanger sequencing. The results of our study expand the clinical and molecular spectrum associated with SCID and leaky SCID phenotypes and provide valuable information for the clinical management of the patients.

Heterogeneity of Signaling Complex Nanostructure in T Cells Activated Via the T Cell Antigen Receptor

Activation of the T cell antigen receptor (TCR) is a key step in initiating the adaptive immune response. Single-molecule localization techniques have been used to investigate the arrangement of proteins within the signaling complexes formed around activated TCRs, but a clear picture of nanoscale organization in stimulated T cells has not emerged. Here, we have improved the examination of T cell nanostructure by visualizing individual molecules of six different proteins in a single sample of activated Jurkat T cells using the multiplexed antibody-size limited direct stochastic optical reconstruction microscopy (madSTORM) technique. We formally define irregularly shaped regions of interest, compare areas where signaling complexes are concentrated with other areas, and improve the statistical analyses of the locations of molecules. We show that nanoscale organization of proteins is mainly confined to the areas with dense concentrations of TCR-based signaling complexes. However, randomly distributed molecules are also found in some areas containing concentrated signaling complexes. These results are consistent with the view that the proteins within signaling complexes are connected by numerous weak interactions, leading to flexible, dynamic, and mutable structures which produce large variations in the nanostructure found in activated T cells.

Mapping the SLP76 interactome in T cells lacking each of the GRB2-family adaptors reveals molecular plasticity of the TCR signaling pathway

The propagation and diversification of signals downstream of the T cell receptor (TCR) involve several adaptor proteins that control the assembly of multimolecular signaling complexes (signalosomes). The global characterization of changes in protein-protein interactions (PPI) following genetic perturbations is critical to understand the resulting phenotypes. Here, by combining genome editing techniques in T cells and interactomics studies based on affinity purification coupled to mass spectrometry (AP-MS) analysis, we determined and quantified the molecular reorganization of the SLP76 interactome resulting from the ablation of each of the three GRB2-family adaptors. Our data showed that the absence of GADS or GRB2 induces a major remodeling of the PPI network associated with SLP76 following TCR engagement. Unexpectedly, this PPI network rewiring minimally affects proximal molecular events of the TCR signaling pathway. Nevertheless, during prolonged TCR stimulation, GRB2- and GADS-deficient cells displayed a reduced level of activation and cytokine secretion capacity. Using the canonical SLP76 signalosome, this analysis highlights the plasticity of PPI networks and their reorganization following specific genetic perturbations.

Expression of Non-T Cell Activation Linker (NTAL) in Jurkat Cells Negatively Regulates TCR Signaling: Potential Role in Rheumatoid Arthritis

T lymphocytes are key players in adaptive immune responses through the recognition of peptide antigens through the T Cell Receptor (TCR). After TCR engagement, a signaling cascade is activated, leading to T cell activation, proliferation, and differentiation into effector cells. Delicate control of activation signals coupled to the TCR is needed to avoid uncontrolled immune responses involving T cells. It has been previously shown that mice deficient in the expression of the adaptor NTAL (Non-T cell activation linker), a molecule structurally and evolutionarily related to the transmembrane adaptor LAT (Linker for the Activation of T cells), develop an autoimmune syndrome characterized by the presence of autoantibodies and enlarged spleens. In the present work we intended to deepen investigation into the negative regulatory functions of the NTAL adaptor in T cells and its potential relationship with autoimmune disorders. For this purpose, in this work we used Jurkat cells as a T cell model, and we lentivirally transfected them to express the NTAL adaptor in order to analyze the effect on intracellular signals associated with the TCR. In addition, we analyzed the expression of NTAL in primary CD4+ T cells from healthy donors and Rheumatoid Arthritis (RA) patients. Our results showed that NTAL expression in Jurkat cells decreased calcium fluxes and PLC-γ1 activation upon stimulation through the TCR complex. Moreover, we showed that NTAL was also expressed in activated human CD4+ T cells, and that the increase of its expression was reduced in CD4+ T cells from RA patients. Our results, together with previous reports, suggest a relevant role for the NTAL adaptor as a negative regulator of early intracellular TCR signaling, with a potential implication in RA.

T cell receptor signaling in the differentiation and plasticity of CD4+ T cells

CD4⁺ T cells are critical components of the adaptive immune system. The T cell receptor (TCR) and co-receptor signaling cascades shape the phenotype and functions of CD4⁺ T cells. TCR signaling plays a crucial role in T cell development, antigen recognition, activation, and differentiation upon recognition of foreign- or auto-antigens. In specific autoimmune conditions, altered TCR repertoire is reported and can predispose autoimmunity with organ-specific inflammation and tissue damage. TCR signaling modulates various signaling cascades and regulates epigenetic and transcriptional regulation during homeostasis and disease conditions. Understanding the mechanism by which coreceptors and cytokine signals control the magnitude of TCR signal amplification will aid in developing therapeutic strategies to treat inflammation and autoimmune diseases. This review focuses on the role of the TCR signaling cascade and its components in the activation, differentiation, and plasticity of various CD4⁺ T cell subsets.

Screening patients with autoimmune endocrine disorders for cytokine autoantibodies reveals monogenic immune deficiencies

BACKGROUND

Autoantibodies against type I interferons (IFN) alpha (α) and omega (ω), and interleukins (IL) 17 and 22 are a hallmark of autoimmune polyendocrine syndrome type 1 (APS-1), caused by mutations in the autoimmune regulator (AIRE) gene. Such antibodies are also seen in a number of monogenic immunodeficiencies.

OBJECTIVES

To determine whether screening for cytokine autoantibodies (anti-IFN-ω and anti-IL22) can be used to identify patients with monogenic immune disorders.

METHODS

A novel ELISA assay was employed to measure IL22 autoantibodies in 675 patients with autoimmune primary adrenal insufficiency (PAI) and a radio immune assay (RIA) was used to measure autoantibodies against IFN-ω in 1778 patients with a variety of endocrine diseases, mostly of autoimmune aetiology. Positive cases were sequenced for all coding exons of the AIRE gene. If no AIRE mutations were found, we applied next generation sequencing (NGS) to search for mutations in immune related genes.

RESULTS

We identified 29 patients with autoantibodies against IFN-ω and/or IL22. Of these, four new APS-1 cases with disease-causing variants in AIRE were found. In addition, we identified two patients with pathogenic heterozygous variants in CTLA4 and NFKB2, respectively. Nine rare variants in other immune genes were identified in six patients, although further studies are needed to determine their disease-causing potential.

CONCLUSION

Screening of cytokine autoantibodies can efficiently identify patients with previously unknown monogenic and possible oligogenic causes of autoimmune and immune deficiency diseases. This information is crucial for providing personalised treatment and follow-up of patients and their relatives.

The Functional Properties and Physiological Roles of Signal-Transducing Adaptor Protein-2 in the Pathogenesis of Inflammatory and Immune Disorders

Adaptor molecules play a crucial role in signal transduction in immune cells. Several adaptor molecules, such as the linker for the activation of T cells (LAT) and SH2 domain-containing leukocyte protein of 76 kDa (SLP-76), are essential for T cell development and activation following T cell receptor (TCR) aggregation, suggesting that adaptor molecules are good therapeutic targets for T cell-mediated immune disorders, such as autoimmune diseases and allergies. Signal-transducing adaptor protein (STAP)-2 is a member of the STAP family of adaptor proteins. STAP-2 functions as a scaffold for various intracellular proteins, including BRK, signal transducer, and activator of transcription (STAT)3, STAT5, and myeloid differentiation primary response protein (MyD88). In T cells, STAP-2 is involved in stromal cell-derived factor (SDF)-1α-induced migration, integrin-dependent cell adhesion, and Fas-mediated apoptosis. We previously reported the critical function of STAP-2 in TCR-mediated T cell activation and T cell-mediated autoimmune diseases. Here, we review how STAP-2 affects the pathogenesis of T cell-mediated inflammation and immune diseases in order to develop novel STAP-2-targeting therapeutic strategies.

Targeting Endocytosis and Cell Communications in the Tumor Immune Microenvironment

The existence of multiple endocytic pathways is well known, and their exact biological effects in tumors have been intensively investigated. Endocytosis can affect the connection between tumor cells and determine the fate of tumor cells. Many relationships between endocytosis and tumor cells have been elucidated, but the mechanism of endocytosis between different types of cells in tumors needs to be explored in greater depth. Endocytic receptors sense the environment and are induced by specific ligands to trigger communication between tumor and immune cells. Crosstalk in the tumor microenvironment can occur through direct contact between cell adhesion molecules or indirectly through exosomes. So a better understanding of the endocytic pathways that control cell adhesion molecules and function is expected to lead to new candidates for cancer treatment. In additional, tumor-derived exosomes may changes immune cell function, which may be a key role for tumors to evade immune detection and response. The overall understanding of exosomes through endocytosis is also expected to bring new candidates for therapeutic regulation of tumor immune microenvironment. In this case, endocytic pathways coordinate cell adhesion molecules and exosomes and can be used as targets in the tumor immune microenvironment for cancer treatment.

The perception and response of T cells to a changing environment are based on the law of initial value

αβ T cells are critical components of the adaptive immune system and are capable of inducing sterilizing immunity after pathogen infection and eliminating transformed tumor cells. The development and function of T cells are controlled through the T cell antigen receptor, which recognizes peptides displayed on major histocompatibility complex (MHC) molecules. Here, we review how T cells generate the ability to recognize self-peptide-bound MHC molecules and use signals derived from these interactions to instruct cellular development, activation thresholds, and functional specialization in the steady state and during immune responses. We argue that the basic tenants of T cell development and function follow Weber-Fetcher's law of just noticeable differences and Wilder's law of initial value. Together, these laws argue that the ability of a system to respond and the quality of that response are scalable to the basal state of that system. Manifestation of these laws in T cells generates clone-specific activation thresholds that are based on perceivable differences between homeostasis and pathogen encounter (self versus nonself discrimination), as well as poised states for subsequent differentiation into specific effector cell lineages.

Regulating the discriminatory response to antigen by T-cell receptor

The cell-mediated immune response constitutes a robust host defense mechanism to eliminate pathogens and oncogenic cells. T cells play a central role in such a defense mechanism and creating memories to prevent any potential infection. T cell recognizes foreign antigen by its surface receptors when presented through antigen-presenting cells (APCs) and calibrates its cellular response by a network of intracellular signaling events. Activation of T-cell receptor (TCR) leads to changes in gene expression and metabolic networks regulating cell development, proliferation, and migration. TCR does not possess any catalytic activity, and the signaling initiates with the colocalization of several enzymes and scaffold proteins. Deregulation of T cell signaling is often linked to autoimmune disorders like severe combined immunodeficiency (SCID), rheumatoid arthritis, and multiple sclerosis. The TCR remarkably distinguishes the minor difference between self and non-self antigen through a kinetic proofreading mechanism. The output of TCR signaling is determined by the half-life of the receptor antigen complex and the time taken to recruit and activate the downstream enzymes. A longer half-life of a non-self antigen receptor complex could initiate downstream signaling by activating associated enzymes. Whereas, the short-lived, self-peptide receptor complex disassembles before the downstream enzymes are activated. Activation of TCR rewires the cellular metabolic response to aerobic glycolysis from oxidative phosphorylation. How does the early event in the TCR signaling cross-talk with the cellular metabolism is an open question. In this review, we have discussed the recent developments in understanding the regulation of TCR signaling, and then we reviewed the emerging role of metabolism in regulating T cell function.

Single-cell transcriptomics uncovers an instructive T-cell receptor role in adult γδ T-cell lineage commitment

After entering the adult thymus, bipotent T‐cell progenitors give rise to αβ or γδ T cells. To determine whether the γδ T‐cell receptor (TCR) has an instructive role in γδ T‐cell lineage commitment or only “confirms” a pre‐established γδ Τ‐cell lineage state, we exploited mice lacking expression of LAT, an adaptor required for γδ TCR signaling. Although these mice showed a T‐cell development block at the CD4⁻CD8⁻ double‐negative third (DN3) stage, 0.3% of their DN3 cells expressed intermediate levels of γδ TCR (further referred to as γδ^int) at their surface. Single‐cell transcriptomics of LAT‐deficient DN3 γδ^int cells demonstrated no sign of commitment to the γδ T‐cell lineage, apart from γδ TCR expression. Although the lack of LAT is thought to tightly block DN3 cell development, we unexpectedly found that 25% of LAT‐deficient DN3 γδ^int cells were actively proliferating and progressed up to the DN4 stage. However, even those cells failed to turn on the transcriptional program associated with the γδ T‐cell lineage. Therefore, the γδ TCR‐LAT signaling axis builds upon a γδ T‐cell uncommitted lineage state to fully instruct adult γδ T‐cell lineage specification.

Single-Cell RNA-Seq Reveals a Crosstalk between Hyaluronan Receptor LYVE-1-Expressing Macrophages and Vascular Smooth Muscle Cells

Background: Atherosclerosis is a chronic inflammatory disease where macrophages participate in the progression of the disease. However, the role of resident-like macrophages (res-like) in the atherosclerotic aorta is not completely understood. Methods: A single-cell RNA sequencing analysis of CD45⁺ leukocytes in the atherosclerotic aorta of apolipoprotein E–deficient (Apoe^−/−) mice on a normal cholesterol diet (NCD) or a high cholesterol diet (HCD), respecting the side-to-specific predisposition to atherosclerosis, was performed. A population of res-like macrophages expressing hyaluronan receptor LYVE-1 was investigated via flow cytometry, co-culture experiments, and immunofluorescence in human atherosclerotic plaques from carotid artery disease patients (CAD). Results: We identified 12 principal leukocyte clusters with distinct atherosclerosis disease-relevant gene expression signatures. LYVE-1⁺ res-like macrophages, expressing a high level of CC motif chemokine ligand 24 (CCL24, eotaxin-2), expanded under hypercholesteremia in Apoe^−/− mice and promoted VSMC phenotypic modulation to osteoblast/chondrocyte-like cells, ex vivo, in a CCL24-dependent manner. Moreover, the abundance of LYVE-1⁺CCL24⁺ macrophages and elevated systemic levels of CCL24 were associated with vascular calcification and CAD events. Conclusions: LYVE-1 res-like macrophages, via the secretion of CCL24, promote the transdifferentiation of VSMC to osteogenic-like cells with a possible role in vascular calcification and likely a detrimental role in atherosclerotic plaque destabilization.

ZAP70, too little, too much can lead to autoimmunity*

Establishing both central and peripheral tolerance requires the appropriate TCR signaling strength to discriminate self‐ from agonist‐peptide bound to self MHC molecules. ZAP70, a cytoplasmic tyrosine kinase, directly interacts with the TCR complex and plays a central and requisite role in TCR signaling in both thymocytes and peripheral T cells. By studying ZAP70 hypomorphic mutations in mice and humans with a spectrum of hypoactive or hyperactive activities, we have gained insights into mechanisms of central and peripheral tolerance. Interestingly, both hypoactive and hyperactive ZAP70 can lead to the development of autoimmune diseases, albeit through distinct mechanisms. Immature thymocytes and mature T cells rely on normal ZAP70 function to complete their development in the thymus and to modulate T cell responses in the periphery. Hypoactive ZAP70 function compromises key developmental checkpoints required to establish central tolerance, allowing thymocytes with potentially self‐reactive TCRs a greater chance to escape negative selection. Such ‘forbidden clones’ may escape into the periphery and may pose a greater risk for autoimmune disease development since they may not engage negative regulatory mechanisms as effectively. Hyperactive ZAP70 enhances thymic negative selection but some thymocytes will, nonetheless, escape negative selection and have greater sensitivity to weak and self‐ligands. Such cells must be controlled by mechanisms involved in anergy, expansion of Tregs, and upregulation of inhibitory receptors or signaling molecules. However, such potentially autoreactive cells may still be able to escape control by peripheral negative regulatory constraints. Consistent with findings in Zap70 mutants, the signaling defects in at least one ZAP70 substrate, LAT, can also lead to autoimmune disease. By dissecting the similarities and differences among mouse models of patient disease or mutations in ZAP70 that affect TCR signaling strength, we have gained insights into how perturbed ZAP70 function can lead to autoimmunity. Because of our work and that of others on ZAP70, it is likely that perturbations in other molecules affecting TCR signaling strength will be identified that also overcome tolerance mechanisms and cause autoimmunity. Delineating these molecular pathways could lead to the development of much needed new therapeutic targets in these complex diseases.

T cell receptor (TCR) signaling in health and disease

Interaction of the T cell receptor (TCR) with an MHC-antigenic peptide complex results in changes at the molecular and cellular levels in T cells. The outside environmental cues are translated into various signal transduction pathways within the cell, which mediate the activation of various genes with the help of specific transcription factors. These signaling networks propagate with the help of various effector enzymes, such as kinases, phosphatases, and phospholipases. Integration of these disparate signal transduction pathways is done with the help of adaptor proteins that are non-enzymatic in function and that serve as a scaffold for various protein-protein interactions. This process aids in connecting the proximal to distal signaling pathways, thereby contributing to the full activation of T cells. This review provides a comprehensive snapshot of the various molecules involved in regulating T cell receptor signaling, covering both enzymes and adaptors, and will discuss their role in human disease.

Novel LAT Pathogenic Variants in a POI Family and Its Role in the Ovary

Premature ovarian insufficiency (POI) affects about 1% of women under 40 years and leads most often to definitive infertility with adverse health outcomes. Genetic factor has been reported to play an important role in POI. However, the genetic etiology remains unknown in the majority of the POI patients. Whole-exome sequencing and variant analysis were carried out in a POI pedigree. In vitro studies of the wild-type and mutant proteins were conducted in primary granulosa cells (GCs) and granulosa cell line. The result showed that the patients carried compound heterozygous nonsynonymous mutations (c.245C > T and c.181C > G) in LAT gene, which were identified to be transmitted from their parents. The two variants were assessed to affect residues that were conserved across different species examined, and were predicted to be deleterious by software predictions. Protein structure predicting result indicated that the two variants could alter their interactions with surrounding residues, which may change the internal structure of the LAT protein. Moreover, LAT protein expression in GCs was demonstrated for the first time, and further functional assays suggested that this mutation could reduce LAT expression and influence GC survival, which may contribute to the etiology of POI. In summary, we detect novel LAT pathogenic variants in a POI pedigree and report for the first time that LAT is present and functional in the GCs of the ovary. Our findings not only shed new light on the role of LAT in GCs, but also broaden the spectrum of genetic causes of POI.

The Clinical Aspect of Adaptor Molecules in T Cell Signaling: Lessons Learnt From Inborn Errors of Immunity

Adaptor molecules lack enzymatic and transcriptional activities. Instead, they exert their function by linking multiple proteins into intricate complexes, allowing for transmitting and fine-tuning of signals. Many adaptor molecules play a crucial role in T-cell signaling, following engagement of the T-cell receptor (TCR). In this review, we focus on Linker of Activation of T cells (LAT) and SH2 domain-containing leukocyte protein of 76 KDa (SLP-76). Monogenic defects in these adaptor proteins, with known roles in T-cell signaling, have been described as the cause of human inborn errors of immunity (IEI). We describe the current knowledge based on defects in cell lines, murine models and human patients. Germline mutations in Adhesion and degranulation adaptor protein (ADAP), have not resulted in a T-cell defect.

A comparative analysis of the intrauterine transcriptome in fertile and subfertile mares using cytobrush sampling

Background

Subfertility is a major problem in modern horse breeding. Especially, mares without clinical signs of reproductive diseases, without known uterine pathogens and no evidence of inflammation but not becoming pregnant after several breeding attempts are challenging for veterinarians. To obtain new insights into the cause of these fertility problems and aiming at improving diagnosis of subfertile mares, a comparative analysis of the intrauterine transcriptome in subfertile and fertile mares was performed. Uterine cytobrush samples were collected during estrus from 57 mares without clinical signs of uterine diseases. RNA was extracted from the cytobrush samples and samples from 11 selected subfertile and 11 fertile mares were used for Illumina RNA-sequencing.

Results

The cytobrush sampling was a suitable technique to isolate enough RNA of high quality for transcriptome analysis. Comparing subfertile and fertile mares, 114 differentially expressed genes (FDR = 10%) were identified. Metascape enrichment analysis revealed that genes with lower mRNA levels in subfertile mares were related to ‘extracellular matrix (ECM)’, ‘ECM-receptor interaction’, ‘focal adhesion’, ‘immune response’ and ‘cytosolic calcium ion concentration’, while DEGs with higher levels in subfertile mares were enriched for ‘monocarboxyl acid transmembrane transport activity’ and ‘protein targeting’.

Conclusion

Our study revealed significant differences in the uterine transcriptome between fertile and subfertile mares and provides leads for potential uterine molecular biomarkers of subfertility in the mare.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07701-3.

Uncovering a novel role of PLCβ4 in selectively mediating TCR signaling in CD8+ but not CD4+ T cells

Because of their common signaling molecules, the main T cell receptor (TCR) signaling cascades in CD4⁺ and CD8⁺ T cells are considered qualitatively identical. Herein, we show that TCR signaling in CD8⁺ T cells is qualitatively different from that in CD4⁺ T cells, since CD8α ignites another cardinal signaling cascade involving phospholipase C β4 (PLCβ4). TCR-mediated responses were severely impaired in PLCβ4-deficient CD8⁺ T cells, whereas those in CD4⁺ T cells were intact. PLCβ4-deficient CD8⁺ T cells showed perturbed activation of peripheral TCR signaling pathways downstream of IP₃ generation. Binding of PLCβ4 to the cytoplasmic tail of CD8α was important for CD8⁺ T cell activation. Furthermore, GNAQ interacted with PLCβ4, mediated double phosphorylation on threonine 886 and serine 890 positions of PLCβ4, and activated CD8⁺ T cells in a PLCβ4-dependent fashion. PLCβ4-deficient mice exhibited defective antiparasitic host defense and antitumor immune responses. Altogether, PLCβ4 differentiates TCR signaling in CD4⁺ and CD8⁺ T cells and selectively promotes CD8⁺ T cell–dependent adaptive immunity.

Adapting T Cell Receptor Ligand Discrimination Capability via LAT

Self- and non-self ligand discrimination is a core principle underlying T cell-mediated immunity. Mature αβ T cells can respond to a foreign peptide ligand presented by major histocompatibility complex molecules (pMHCs) on antigen presenting cells, on a background of continuously sensed self-pMHCs. How αβ T cells can properly balance high sensitivity and high specificity to foreign pMHCs, while surrounded by a sea of self-peptide ligands is not well understood. Such discrimination cannot be explained solely by the affinity parameters of T cell antigen receptor (TCR) and pMHC interaction. In this review, we will discuss how T cell ligand discrimination may be molecularly defined by events downstream of the TCR-pMHC interaction. We will discuss new evidence in support of the kinetic proofreading model of TCR ligand discrimination, and in particular how the kinetics of specific phosphorylation sites within the adaptor protein linker for activation of T cells (LAT) determine the outcome of TCR signaling. In addition, we will discuss emerging data regarding how some kinases, including ZAP-70 and LCK, may possess scaffolding functions to more efficiently direct their kinase activities.

Spontaneous Differentiation of T Follicular Helper Cells in LATY136F Mutant Mice

Mice with a mutation at the LAT-PLCγ1 binding site (Y136) have a defect in thymocyte development due to dampened TCR signaling. CD4⁺ T cells that do reach the periphery are hyper-activated and skewed to Th2. Over time, these mice develop an autoimmune-like syndrome, characterize by overproduction of Th2 cytokines, T cell infiltration into various organs, and B cell activation, isotype switching, and autoantibody production. In this study, we examined IL4 production by CD4⁺ T cells in the LATY136F mice using the KN2 reporter mice, in which human CD2 expression marks T cells that are actively producing IL4 protein. We showed that these mice had spontaneous Tfh differentiation. Despite the fact that the majority of CD4⁺ T cells were skewed to Th2 and were GATA3⁺, only a small subset of them were actively secreting IL4. These T cells were Tfh cells that expressed BCL6 and were localized to B cell-rich germinal centers within the spleen. Interestingly, these Tfh cells expressed high levels of both BCL6 and GATA3. By using LAT conditional knockout mice that inducibly express only the LATY136F allele, we further showed that Tfh cell differentiation was likely the result of defective LAT-PLCγ1 signaling in the periphery. In addition, B cells were required for spontaneous development of Tfh cells and uncontrolled T cell expansion in these mice. Together, these results indicated a novel role for tonic LAT-PLCγ1 signaling in modulating Tfh cell differentiation during development of autoimmune syndrome.

Transcriptomic analysis reveals the molecular mechanisms of rumen wall morphological and functional development induced by different solid diet introduction in a lamb model

Background

This study aimed to elucidate the molecular mechanisms of solid diet introduction initiating the cellular growth and maturation of rumen tissues and characterize the shared and unique biological processes upon different solid diet regimes.

Methods

Twenty-four Hu lambs were randomly allocated to three groups fed following diets: goat milk powder only (M, n = 8), goat milk powder + alfalfa hay (MH, n = 8), and goat milk powder + concentrate starter (MC, n = 8). At 42 days of age, the lambs were slaughtered. Ruminal fluid sample was collected for analysis of concentration of volatile fatty acid (VFA) and microbial crude protein (MCP). The sample of the rumen wall from the ventral sac was collected for analysis of rumen papilla morphology and transcriptomics.

Results

Compared with the M group, MH and MC group had a higher concentration of VFA, MCP, rumen weight, and rumen papilla area. The transcriptomic results of rumen wall showed that there were 312 shared differentially expressed genes (DEGs) between in “MH vs. M” and “MC vs. M”, and 232 or 796 unique DEGs observed in “MH vs. M” or “MC vs. M”, respectively. The shared DEGs were most enriched in VFA absorption and metabolism, such as peroxisome proliferator-activated receptor (PPAR) signaling pathway, butanoate metabolism, and synthesis and degradation of ketone bodies. Additionally, a weighted gene co-expression network analysis identified M16 (2,052 genes) and M18 (579 genes) modules were positively correlated with VFA and rumen wall morphology. The M16 module was mainly related to metabolism pathway, while the M18 module was mainly associated with signaling transport. Moreover, hay specifically depressed expression of genes involved in cytokine production, immune response, and immunocyte activation, and concentrate starter mainly altered nutrient transport and metabolism, especially ion transport, amino acid, and fatty acid metabolism.

Conclusions

The energy production during VFA metabolism may drive the rumen wall development directly. The hay introduction facilitated establishment of immune function, while the concentrate starter enhanced nutrient transport and metabolism, which are important biological processes required for rumen development.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00556-4.

Retrograde and Anterograde Transport of Lat-Vesicles during the Immunological Synapse Formation: Defining the Finely-Tuned Mechanism

LAT is an important player of the signaling cascade induced by TCR activation. This adapter molecule is present at the plasma membrane of T lymphocytes and more abundantly in intracellular compartments. Upon T cell activation the intracellular pool of LAT is recruited to the immune synapse (IS). We previously described two pathways controlling LAT trafficking: retrograde transport from endosomes to the TGN, and anterograde traffic from the Golgi to the IS. We address the specific role of four proteins, the GTPase Rab6, the t-SNARE syntaxin-16, the v-SNARE VAMP7 and the golgin GMAP210, in each pathway. Using different methods (endocytosis and Golgi trap assays, confocal and TIRF microscopy, TCR-signalosome pull down) we show that syntaxin-16 is regulating the retrograde transport of LAT whereas VAMP7 is regulating the anterograde transport. Moreover, GMAP210 and Rab6, known to contribute to both pathways, are in our cellular context, specifically and respectively, involved in anterograde and retrograde transport of LAT. Altogether, our data describe how retrograde and anterograde pathways coordinate LAT enrichment at the IS and point to the Golgi as a central hub for the polarized recruitment of LAT to the IS. The role that this finely-tuned transport of signaling molecules plays in T-cell activation is discussed.

A Novel, LAT/Lck Double Deficient T Cell Subline J.CaM1.7 for Combined Analysis of Early TCR Signaling

Intracellular signaling through the T cell receptor (TCR) is essential for T cell development and function. Proper TCR signaling requires the sequential activities of Lck and ZAP-70 kinases, which result in the phosphorylation of tyrosine residues located in the CD3 ITAMs and the LAT adaptor, respectively. LAT, linker for the activation of T cells, is a transmembrane adaptor protein that acts as a scaffold coupling the early signals coming from the TCR with downstream signaling pathways leading to cellular responses. The leukemic T cell line Jurkat and its derivative mutants J.CaM1.6 (Lck deficient) and J.CaM2 (LAT deficient) have been widely used to study the first signaling events upon TCR triggering. In this work, we describe the loss of LAT adaptor expression found in a subline of J.CaM1.6 cells and analyze cis-elements responsible for the LAT expression defect. This new cell subline, which we have called J.CaM1.7, can re-express LAT adaptor after Protein Kinase C (PKC) activation, which suggests that activation-induced LAT expression is not affected in this new cell subline. Contrary to J.CaM1.6 cells, re-expression of Lck in J.CaM1.7 cells was not sufficient to recover TCR-associated signals, and both LAT and Lck had to be introduced to recover activatory intracellular signals triggered after CD3 crosslinking. Overall, our work shows that the new LAT negative J.CaM1.7 cell subline could represent a new model to study the functions of the tyrosine kinase Lck and the LAT adaptor in TCR signaling, and their mutual interaction, which seems to constitute an essential early signaling event associated with the TCR/CD3 complex.

The role of prolines and glycine in the transmembrane domain of LAT

Linker for activation in T cells (LAT) is a critical regulator of T-cell development and function. It organises signalling events at the plasma membrane. However, the mechanism, which controls LAT localisation at the plasma membrane, is not fully understood. Here, we studied the impact of helix-breaking amino acids, two prolines and one glycine, in the transmembrane segment on localisation and function of LAT. Using in silico analysis, confocal and super-resolution imaging and flow cytometry, we demonstrate that central proline residue destabilises transmembrane helix by inducing a kink. The helical structure and dynamics are further regulated by glycine and another proline residue in the luminal part of LAT transmembrane domain. Replacement of these residues with aliphatic amino acids reduces LAT dependence on palmitoylation for sorting to the plasma membrane. However, surface expression of these mutants is not sufficient to recover function of nonpalmitoylated LAT in stimulated T cells. These data indicate that geometry and dynamics of LAT transmembrane segment regulate its localisation and function in immune cells.

Epidermal resident γδ T cell development and function in skin

Epidermal resident γδ T cells, or dendritic epidermal T cells (DETCs) in mice, are a unique and conserved population of γδ T cells enriched in the epidermis, where they serve as the regulators of immune responses and sense skin injury. Despite the great advances in the understanding of the development, homeostasis, and function of DETCs in the past decades, the origin and the underlying molecular mechanisms remain elusive. Here, we reviewed the recent research progress on DETCs, including their origin and homeostasis in the skin, especially at transcriptional and epigenetic levels, and discuss the involvement of DETCs in skin diseases.

The Transmembrane Adaptor Protein LIME Is Essential for Chemokine-Mediated Migration of Effector T Cells to Inflammatiory Sites

Lck-interacting transmembrane adaptor 1 (LIME) has been previously identified as a raft-associated transmembrane protein expressed predominantly in T and B lymphocytes. Although LIME is shown to transduce the immunoreceptor signaling and immunological synapse formation via its tyrosine phosphorylation by Lck, a Src-family kinase, the in vivo function of LIME has remained elusive in the previous studies. Here we report that LIME is preferentially expressed in effector T cells and mediates chemokine-mediated T cell migration. Interestingly, in LIME-/- mice, while T cell receptor stimulation-dependent proliferation, differentiation to effector T cells, cytotoxic T lymphocyte (CTL) function and regulatory T lymphocyte (Treg) function were normal, only T cell-mediated inflammatory response was significantly defective. The reduced inflammation was accompanied by the impaired infiltration of leukocytes and T cells to the inflammatory sites of LIME-/- mice. More specifically, the absence of LIME in effector T cells resulted in the reduced migration and defective morphological polarization in response to inflammatory chemokines such as CCL5 and CXCL10. Consistently, LIME-/- effector T cells were found to be defective in chemokine-mediated activation of Rac1 and Rap1, and dysregulated phosphorylation of Pyk2 and Cas. Taken together, the present findings show that LIME is a critical regulator of inflammatory chemokine-mediated signaling and the subsequent migration of effector T cells to inflammatory sites.

The membrane proximal proline-rich region and correct order of C-terminal tyrosines on the adaptor protein LAT are required for TCR-mediated signaling and downstream functions

The primary activating receptor for T cells is the T cell receptor (TCR), which is stimulated upon binding to an antigen/MHC complex. TCR activation results in the induction of regulated signaling pathways vital for T cell differentiation, cellular adhesion and cytokine release. A critical TCR-induced signaling protein is the adaptor protein LAT. Upon TCR stimulation, LAT is phosphorylated on conserved tyrosines, which facilitates the formation of multiprotein complexes needed for propagation of signaling pathways. Although the role of the conserved tyrosines in LAT-mediated signaling has been investigated, few studies have examined the role of larger regions of LAT in TCR-induced pathways. In this study, a sequence alignment of 97 mammalian LAT proteins was used to identify several "functional" domains on LAT. Using LAT mutants expressed in Jurkat E6.1 cells, we observed that the membrane proximal, proline-rich region of LAT and the correct order of domains containing conserved tyrosines are necessary for optimal TCR-mediated early signaling, cytokine production, and cellular adhesion. Together, these data show that LAT contains distinct regions whose presence and correct order are required for the propagation of TCR-mediated signaling pathways.

Targeting NF-κB pathway for the therapy of diseases: mechanism and clinical study

NF-κB pathway consists of canonical and non-canonical pathways. The canonical NF-κB is activated by various stimuli, transducing a quick but transient transcriptional activity, to regulate the expression of various proinflammatory genes and also serve as the critical mediator for inflammatory response. Meanwhile, the activation of the non-canonical NF-κB pathway occurs through a handful of TNF receptor superfamily members. Since the activation of this pathway involves protein synthesis, the kinetics of non-canonical NF-κB activation is slow but persistent, in concordance with its biological functions in the development of immune cell and lymphoid organ, immune homeostasis and immune response. The activation of the canonical and non-canonical NF-κB pathway is tightly controlled, highlighting the vital roles of ubiquitination in these pathways. Emerging studies indicate that dysregulated NF-κB activity causes inflammation-related diseases as well as cancers, and NF-κB has been long proposed as the potential target for therapy of diseases. This review attempts to summarize our current knowledge and updates on the mechanisms of NF-κB pathway regulation and the potential therapeutic application of inhibition of NF-κB signaling in cancer and inflammatory diseases.

Increased Protein Stability and Interleukin-2 Production of a LATG131D Variant With Possible Implications for T Cell Anergy

The adaptor LAT plays a crucial role in the transduction of signals coming from the TCR/CD3 complex. Phosphorylation of some of its tyrosines generates recruitment sites for other cytosolic signaling molecules. Tyrosine 132 in human LAT is essential for PLC-γ activation and calcium influx generation. It has been recently reported that a conserved glycine residue preceding tyrosine 132 decreases its phosphorylation kinetics, which constitutes a mechanism for ligand discrimination. Here we confirm that a LAT mutant in which glycine 131 has been substituted by an aspartate (LAT^G131D) increases phosphorylation of Tyr132, PLC-γ activation and calcium influx generation. Interestingly, the LAT^G131D mutant has a slower protein turnover while being equally sensitive to Fas-mediated protein cleavage by caspases. Moreover, J.CaM2 cells expressing LAT^G131D secrete greater amounts of interleukin-2 (IL-2) in response to CD3/CD28 engagement. However, despite this increased IL-2 secretion, J.CaM2 cells expressing the LAT^G131D mutant are more sensitive to inhibition of IL-2 production by pre-treatment with anti-CD3, which points to a possible role of this residue in the generation of anergy. Our results suggest that the increased kinetics of LAT Tyr132 phosphorylation could contribute to the establishment of T cell anergy, and thus constitutes an earliest known intracellular event responsible for the induction of peripheral tolerance.

LRCH1 deficiency enhances LAT signalosome formation and CD8+ T cell responses against tumors and pathogens

CD8⁺ T cells play pivotal roles in eradicating pathogens and tumor cells. T cell receptor (TCR) signaling is vital for the optimal activation of CD8⁺ T cells. Upon TCR engagement, the transmembrane adapter protein LAT (linker for activation of T cells) recruits other key signaling molecules and forms the "LAT signalosome" for downstream signal transduction. However, little is known about which functional partners could restrain the formation of the LAT signalosome and inhibit CD8⁺ cytotoxic T lymphocyte (CTL)-mediated cytotoxicity. Here we have demonstrated that LRCH1 (leucine-rich repeats and calponin homology domain containing 1) directly binds LAT, reduces LAT phosphorylation and interaction with GRB2, and also promotes the endocytosis of LAT. Lrch1 ^-/- mice display better protection against influenza virus and Listeria infection, with enhanced CD8⁺ T cell proliferation and cytotoxicity. Adoptive transfer of Lrch1 ^-/- CD8⁺ CTLs leads to increased B16-MO5 tumor clearance in vivo. Furthermore, knockout of LRCH1 in human chimeric antigen receptor (CAR) T cells that recognize the liver tumor-associated antigen glypican-3 could improve CAR T cell migration and proliferation in vitro. These findings suggest LRCH1 as a potential translational target to improve T cell immunotherapy against infection and tumors.

Vessel-derived angiocrine IGF1 promotes Meckel's cartilage proliferation to drive jaw growth during embryogenesis

Craniofacial development is a complex morphogenic process that requires highly orchestrated interactions between multiple cell types. Blood vessel-derived angiocrine factors are known to promote proliferation of chondrocytes in Meckel's cartilage to drive jaw outgrowth, however the specific factors controlling this process remain unknown. Here, we use in vitro and ex vivo cell and tissue culture, as well as genetic mouse models, to identify IGF1 as a novel angiocrine factor directing Meckel's cartilage growth during embryonic development. We show that IGF1 is secreted by blood vessels and that deficient IGF1 signalling underlies mandibular hypoplasia in Wnt1-Cre; Vegfa^fl/fl mice that exhibit vascular and associated jaw defects. Furthermore, conditional removal of IGF1 from blood vessels causes craniofacial defects including a shortened mandible, and reduced proliferation of Meckel's cartilage chondrocytes. This demonstrates a crucial angiocrine role for IGF1 during craniofacial cartilage growth, and identifies IGF1 as a putative therapeutic for jaw and/or cartilage growth disorders.

Impaired T cell receptor signaling and development of T cell-mediated autoimmune arthritis

Mutations of the genes encoding T-cell receptor (TCR)-proximal signaling molecules, such as ZAP-70, can be causative of immunological diseases ranging from T-cell immunodeficiency to T-cell-mediated autoimmune disease. For example, SKG mice, which carry a hypomorphic point mutation of the Zap-70 gene, spontaneously develop T-cell-mediated autoimmune arthritis immunopathologically similar to human rheumatoid arthritis (RA). The Zap-70 mutation alters the sensitivity of developing T cells to thymic positive/negative selection by self-peptides/MHC complexes, shifting self-reactive TCR repertoire to include a dominant arthritogenic specificity and also affecting thymic development and function of autoimmune suppressive regulatory T (Treg) cells. Polyclonal self-reactive T cells, including potentially arthritogenic T cells, thus produced by the thymus recognize self-peptide/MHC complexes on antigen-presenting cells (APCs) in the periphery and stimulate them to produce cytokines including IL-6 to drive the arthritogenic T cells to differentiate into arthritogenic T-helper 17 (Th17) cells. Insufficient Treg suppression or activation of APCs via microbial and other environmental stimuli evokes arthritis by activating granulocyte-macrophage colony-stimulating factor-secreting effector Th17 cells, mediating chronic bone-destructive joint inflammation by activating myeloid cells, innate lymphoid cells, and synoviocytes in the joint. These findings obtained from the study of SKG mouse arthritis are instrumental in understanding how arthritogenic T cells are produced, become activated, and differentiate into effector T cells mediating arthritis, and may help devising therapeutic measures targeting autoimmune pathogenic Th17 cells or autoimmune-suppressing Treg cells to treat and prevent RA.

Two Successive Inversional Vβ Rearrangements on a Single Tcrb Allele Can Contribute to the TCRβ Repertoire

Mammalian TCRβ loci contain 30 Vβ gene segments upstream and in the same transcriptional orientation as two DJCβ clusters, and a downstream Vβ (TRBV31) in the opposite orientation. The textbook view is upstream Vβs rearrange only by deletion and TRBV31 rearranges only by inversion to create VβDJCβ genes. In this study, we show in mice that upstream Vβs recombine through inversion to the DJCβ2 cluster on alleles carrying a preassembled Trbv31-DJCβ1 gene. When this gene is in-frame, Trbv5 evades TCRβ-signaled feedback inhibition and recombines by inversion to the DJCβ2 cluster, creating αβ T cells that express assembled Trbv5-DJCβ2 genes. On alleles with an out-of-frame Trbv31-DJCβ1 gene, most upstream Vβs recombine at low levels and promote αβ T cell development, albeit with preferential expansion of Trbv1-DJβ2 rearrangements. Finally, we show wild-type Tcrb alleles produce mature αβ T cells that express upstream Vβ peptides in surface TCRs and carry Trbv31-DJβ2 rearrangements. Our study indicates two successive inversional Vβ-to-DJβ rearrangements on the same allele can contribute to the TCRβ repertoire.

Bridging the Gap: Modulatory Roles of the Grb2-Family Adaptor, Gads, in Cellular and Allergic Immune Responses

Antigen receptor signaling pathways are organized by adaptor proteins. Three adaptors, LAT, Gads, and SLP-76, form a heterotrimeric complex that mediates signaling by the T cell antigen receptor (TCR) and by the mast cell high affinity receptor for IgE (FcεRI). In both pathways, antigen recognition triggers tyrosine phosphorylation of LAT and SLP-76. The recruitment of SLP-76 to phospho-LAT is bridged by Gads, a Grb2 family adaptor composed of two SH3 domains flanking a central SH2 domain and an unstructured linker region. The LAT-Gads-SLP-76 complex is further incorporated into larger microclusters that mediate antigen receptor signaling. Gads is positively regulated by dimerization, which promotes its cooperative binding to LAT. Negative regulation occurs via phosphorylation or caspase-mediated cleavage of the linker region of Gads. FcεRI-mediated mast cell activation is profoundly impaired in LAT- Gads- or SLP-76-deficient mice. Unexpectedly, the thymic developmental phenotype of Gads-deficient mice is much milder than the phenotype of LAT- or SLP-76-deficient mice. This distinction suggests that Gads is not absolutely required for TCR signaling, but may modulate its sensitivity, or regulate a particular branch of the TCR signaling pathway; indeed, the phenotypic similarity of Gads- and Itk-deficient mice suggests a functional connection between Gads and Itk. Additional Gads binding partners include costimulatory proteins such as CD28 and CD6, adaptors such as Shc, ubiquitin regulatory proteins such as USP8 and AMSH, and kinases such as HPK1 and BCR-ABL, but the functional implications of these interactions are not yet fully understood. No interacting proteins or function have been ascribed to the evolutionarily conserved N-terminal SH3 of Gads. Here we explore the biochemical and functional properties of Gads, and its role in regulating allergy, T cell development and T-cell mediated immunity.

Tethering of vesicles to the Golgi by GMAP210 controls LAT delivery to the immune synapse

The T cell immune synapse is a site of intense vesicular trafficking. Here we show that the golgin GMAP210, known to capture vesicles and organize membrane traffic at the Golgi, is involved in the vesicular transport of LAT to the immune synapse. Upon activation, more GMAP210 interact with LAT-containing vesicles and go together with LAT to the immune synapse. Regulating LAT recruitment and LAT-dependent signaling, GMAP210 controls T cell activation. Using a rerouting and capture assay, we show that GMAP210 captures VAMP7-decorated vesicles. Overexpressing different domains of GMAP210, we also show that GMAP210 allows their specific delivery to the immune synapse by tethering LAT-vesicles to the Golgi. Finally, in a model of ectopic expression of LAT in ciliated cells, we show that GMAP210 tethering activity controls the delivery of LAT to the cilium. Hence, our results reveal a function for the golgin GMAP210 conveying specific vesicles to the immune synapse.

Coexpression of YY1 Is Required to Elaborate the Effector Functions Controlled by PLZF in NKT Cells

The promyelocytic leukemia zinc-finger transcription factor (PLZF) is essential for nearly all of the unique, innate-like functions and characteristics of NKT cells. It is not known, however, if the activity of PLZF is regulated by other factors. In this article, we show that the function of PLZF is completely dependent on the transcription factor Yin Yang 1 (YY1). Mouse NKT cells expressing wild-type levels of PLZF, but deficient for YY1, had developmental defects, lost their characteristic "preformed" mRNA for cytokines, and failed to produce cytokine protein upon primary activation. Immunoprecipitation experiments showed that YY1 and PLZF were coassociated. Taken together, these biochemical and genetic data show that the broadly expressed transcription factor, YY1, is required for the cell-specific "master regulator" functions of PLZF.

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.

Alternative polyadenylation of single cells delineates cell types and serves as a prognostic marker in early stage breast cancer

Alternative polyadenylation (APA) in 3’ untranslated regions (3’ UTR) plays an important role in regulating transcript abundance, localization, and interaction with microRNAs. Length-variation of 3’UTRs by APA contributes to efficient proliferation of cancer cells. In this study, we investigated APA in single cancer cells and tumor microenvironment cells to understand the physiological implication of APA in different cell types. We analyzed APA patterns and the expression level of genes from the 515 single-cell RNA sequencing (scRNA-seq) dataset from 11 breast cancer patients. Although the overall 3’UTR length of individual genes was distributed equally in tumor and non-tumor cells, we found a differential pattern of polyadenylation in gene sets between tumor and non-tumor cells. In addition, we found a differential pattern of APA across tumor types using scRNA-seq data from 3 glioblastoma patients and 1 renal cell carcinoma patients. In detail, 1,176 gene sets and 53 genes showed the distinct pattern of 3’UTR shortening and over-expression as signatures for five cell types including B lymphocytes, T lymphocytes, myeloid cells, stromal cells, and breast cancer cells. Functional categories of gene sets for cellular proliferation demonstrated concordant regulation of APA and gene expression specific to cell types. The expression of APA genes in breast cancer was significantly correlated with the clinical outcome of earlier stage breast cancer patients. We identified cell type-specific APA in single cells, which allows the identification of cell types based on 3’UTR length variation in combination with gene expression. Specifically, an immune-specific APA signature in breast cancer could be utilized as a prognostic marker of early stage breast cancer.

T cell receptor signaling for γδT cell development

T cells are central to the vertebrate immune system. Two distinct types of T cells, αβT and γδT cells, express different types of T cell antigen receptors (TCRs), αβTCR and γδTCR, respectively, that are composed of different sets of somatically rearranged TCR chains and CD3 subunits. γδT cells have recently attracted considerable attention due to their ability to produce abundant cytokines and versatile roles in host defense, tissue regeneration, inflammation, and autoimmune diseases. Both αβT and γδT cells develop in the thymus. Unlike the development of αβT cells, which depends on αβTCR-mediated positive and negative selection, the development of γδT cells, including the requirement of γδTCR, has been less well understood. αβT cells differentiate into effector cells in the peripheral tissues, whereas γδT cells acquire effector functions during their development in the thymus. In this review, we will discuss the current state of knowledge of the molecular mechanism of TCR signal transduction and its role in the thymic development of γδT cells, particularly highlighting a newly discovered mechanism that controls proinflammatory γδT cell development.

Bridging the Gap: Modulatory Roles of the Grb2-Family Adaptor, Gads, in Cellular and Allergic Immune Responses

Antigen receptor signaling pathways are organized by adaptor proteins. Three adaptors, LAT, Gads, and SLP-76, form a heterotrimeric complex that mediates signaling by the T cell antigen receptor (TCR) and by the mast cell high affinity receptor for IgE (FcεRI). In both pathways, antigen recognition triggers tyrosine phosphorylation of LAT and SLP-76. The recruitment of SLP-76 to phospho-LAT is bridged by Gads, a Grb2 family adaptor composed of two SH3 domains flanking a central SH2 domain and an unstructured linker region. The LAT-Gads-SLP-76 complex is further incorporated into larger microclusters that mediate antigen receptor signaling. Gads is positively regulated by dimerization, which promotes its cooperative binding to LAT. Negative regulation occurs via phosphorylation or caspase-mediated cleavage of the linker region of Gads. FcεRI-mediated mast cell activation is profoundly impaired in LAT- Gads- or SLP-76-deficient mice. Unexpectedly, the thymic developmental phenotype of Gads-deficient mice is much milder than the phenotype of LAT- or SLP-76-deficient mice. This distinction suggests that Gads is not absolutely required for TCR signaling, but may modulate its sensitivity, or regulate a particular branch of the TCR signaling pathway; indeed, the phenotypic similarity of Gads- and Itk-deficient mice suggests a functional connection between Gads and Itk. Additional Gads binding partners include costimulatory proteins such as CD28 and CD6, adaptors such as Shc, ubiquitin regulatory proteins such as USP8 and AMSH, and kinases such as HPK1 and BCR-ABL, but the functional implications of these interactions are not yet fully understood. No interacting proteins or function have been ascribed to the evolutionarily conserved N-terminal SH3 of Gads. Here we explore the biochemical and functional properties of Gads, and its role in regulating allergy, T cell development and T-cell mediated immunity.

CD6, a Rheostat-Type Signalosome That Tunes T Cell Activation

Following T cell receptor triggering, T cell activation is initiated and amplified by the assembly at the TCR/CD3 macrocomplex of a multitude of stimulatory enzymes that activate several signaling cascades. The potency of signaling is, however, modulated by various inhibitory components already at the onset of activation, long before co-inhibitory immune checkpoints are expressed to help terminating the response. CD5 and CD6 are surface glycoproteins of T cells that have determinant roles in thymocyte development, T cell activation and immune responses. They belong to the superfamily of scavenger receptor cysteine-rich (SRCR) glycoproteins but whereas the inhibitory role of CD5 has been established for long, there is still controversy on whether CD6 may have similar or antagonistic functions on T cell signaling. Analysis of the structure and molecular associations of CD5 and CD6 indicates that these molecules assemble at the cytoplasmic tail a considerable number of signaling effectors that can putatively transduce diverse types of intracellular signals. Biochemical studies have concluded that both receptors can antagonize the flow of TCR-mediated signaling; however, the impact that CD5 and CD6 have on T cell development and T cell-mediated immune responses may be different. Here we analyze the signaling function of CD6, the common and also the different properties it exhibits comparing with CD5, and interpret the functional effects displayed by CD6 in recent animal models.

Immunity and ultrasonic vocalization in rodents

Ultrasonic vocalizations (USVs) serve important communicative functions in rodents. Different types of USVs can be triggered in the sender, for example, by maternal separation, social interactions, or exposure to predators, and they evoke affiliative or alarming behaviors in recipients. This review focusses on studies evaluating possible links between immunity and USVs. Most studies have been performed in a murine model of maternal immune activation and subsequent evaluation of effects in the offspring. This model has received large attention in recent years because it mimics behavioral abnormalities observed in certain human neuropsychiatric disorders, including autism spectrum disorder. Although there is still some controversy, the results indicate that stimulation of the immune system of mice and rats during pregnancy affects ultrasonic calling in pups. Few studies are available on immunization during adulthood and USVs. In most cases, immune stimulation led to disease, complicating conclusions about a possible direct link between vocalization and immunity. Although much work is still needed, this is certainly a rather new and promising aspect of interactions between the immune system and behavior.