Allosteric Changes Underlie the Outside-In Transmission of Activatory Signals in the TCR.

Rather than being contained in a single polypeptide, and unlike receptor tyrosine kinases, the T cell receptor (TCR) divides its signaling functions among its subunits: TCRα/β bind the extracellular ligand, an antigenic peptide-MHC complex (pMHC), and the CD3 subunits (CD3γ, CD3δ, CD3ε, and CD3ζ) transmit this information to the cytoplasm. How information about the quality of pMHC binding outside is transmitted to the cytoplasm remains a matter of debate. In this review, we compile data generated using a wide variety of experimental systems indicating that TCR engagement by an appropriate pMHC triggers allosteric changes transmitted from the ligand-binding loops in the TCRα and TCRβ subunits to the cytoplasmic tails of the CD3 subunits.

From TCR fundamental research to innovative chimeric antigen receptor design.

Engineered T cells that express chimeric antigen receptors (CARs) have transformed the treatment of haematological cancers. CARs combine the tumour-antigen-binding function of antibodies with the signalling functions of the T cell receptor (TCR) ζ chain and co-stimulatory receptors. The resulting constructs aim to mimic the TCR-based and co-receptor-based activation of T cells.

TCR/CD3-based synthetic antigen receptors (TCC) convey superior antigen sensitivity combined with high fidelity of activation.

Low antigen sensitivity and a gradual loss of effector functions limit the clinical applicability of chimeric antigen receptor (CAR)-modified T cells and call for alternative antigen receptor designs for effective T cell-based cancer immunotherapy. Here, we applied advanced microscopy to demonstrate that TCR/CD3-based synthetic constructs (TCC) outperform second-generation CAR formats with regard to conveyed antigen sensitivities by up to a thousandfold. TCC-based antigen recognition occurred without adverse nonspecific signaling, which is typically observed in CAR-T cells, and did not depend-unlike sensitized peptide/MHC detection by conventional T cells-on CD4 or CD8 coreceptor engagement.

Sodium chloride in the tumor microenvironment enhances T cell metabolic fitness and cytotoxicity.

The efficacy of antitumor immunity is associated with the metabolic state of cytotoxic T cells, which is sensitive to the tumor microenvironment. Whether ionic signals affect adaptive antitumor immune responses is unclear. In the present study, we show that there is an enrichment of sodium in solid tumors from patients with breast cancer.

The potential of γδ CAR and TRuC T cells: An unearthed treasure.

Recent years have witnessed the success of αβ T cells engineered to express chimeric antigen receptors (CARs) in treating haematological cancers. CARs combine the tumour antigen binding capability of antibodies with the signalling functions of the T-cell receptor (TCR) ζ chain and co-stimulatory receptors. Despite the success, αβ CAR T cells face limitations.

Phospho-mimetic CD3ε variants prevent TCR and CAR signaling.

Introduction: Antigen binding to the T cell antigen receptor (TCR) leads to the phosphorylation of the immunoreceptor tyrosine-based activation motifs (ITAMs) of the CD3 complex, and thereby to T cell activation. The CD3ε subunit plays a unique role in TCR activation by recruiting the kinase LCK and the adaptor protein NCK prior to ITAM phosphorylation. Here, we aimed to investigate how phosphorylation of the individual CD3ε ITAM tyrosines impacts the CD3ε signalosome.

Empowering γδ T-cell functionality with vitamin C.

Vitamin C (ascorbic acid) is a potent antioxidant and a cofactor for various enzymes including histone demethylases and methylcytosine dioxygenases. Vitamin C also exerts direct cytotoxicity toward selected tumor cells including colorectal carcinoma. Moreover, vitamin C has been shown to impact immune cell differentiation at various levels including maturation and/or functionality of T cells and their progenitors, dendritic cells, B cells, and NK cells.

Type I Interferon, Induced by Adenovirus or Adenoviral Vector Infection, Regulates the Cytokine Response to Lipopolysaccharide in a Macrophage Type-Specific Manner.

Introduction: While TLR ligands derived from microbial flora and pathogens are important activators of the innate immune system, a variety of factors such as intracellular bacteria, viruses, and parasites can induce a state of hyperreactivity, causing a dysregulated and potentially life-threatening cytokine over-response upon TLR ligand exposure. Type I interferon (IFN-αβ) is a central mediator in the induction of hypersensitivity and is strongly expressed in splenic conventional dendritic cells (cDC) and marginal zone macrophages (MZM) when mice are infected with adenovirus. This study investigates the ability of adenoviral infection to influence the activation state of the immune system and underlines the importance of considering this state when planning the treatment of patients.

Kidins220 and Aiolos promote thymic iNKT cell development by reducing TCR signals.

Development of T cells is controlled by the signal strength of the TCR. The scaffold protein kinase D-interacting substrate of 220 kilodalton (Kidins220) binds to the TCR; however, its role in T cell development was unknown. Here, we show that T cell-specific Kidins220 knockout (T-KO) mice have strongly reduced invariant natural killer T (iNKT) cell numbers and modest decreases in conventional T cells.

OptoREACT: Optogenetic Receptor Activation on Nonengineered Human T Cells.

Optogenetics is a versatile and powerful tool for the control and analysis of cellular signaling processes. The activation of cellular receptors by light using optogenetic switches usually requires genetic manipulation of cells. However, this considerably limits the application in primary, nonengineered cells, which is crucial for the study of physiological signaling processes and for controlling cell fate and function for therapeutic purposes.

Vdelta1 T cells are more resistant than Vdelta2 T cells to the immunosuppressive properties of galectin-3.

Ovarian carcinomas have the highest lethality amongst gynecological tumors. A problem after primary resection is the recurrence of epithelial ovarian carcinomas which is often associated with chemotherapy resistance. To improve the clinical outcome, it is of high interest to consider alternative therapy strategies.

Reprogramming of human γδ T cells by expression of an anti-CD19 TCR fusion construct (εTRuC) to enhance tumor killing.

We have developed a new format of a chimeric antigen receptor for αβ T cells, in which the single-chain variable fragment recognizing the tumor antigen is directly fused to the T cell receptor, called T cell receptor fusion construct (TRuC). Here, we express an anti-CD19 εTRuC in primary γδ T cells that were expanded using zoledronate (Zol) or concanavalin A. We show that the resulting εTRuC γδ T cells were reprogrammed to better recognize CD19-positive B cell tumors and-in case of the Zol-expanded cells-a CD19-expressing colon adenocarcinoma-derived cell line in vitro.

A distinct topology of BTN3A IgV and B30.2 domains controlled by juxtamembrane regions favors optimal human γδ T cell phosphoantigen sensing.

Butyrophilin (BTN)-3A and BTN2A1 molecules control the activation of human Vγ9Vδ2 T cells during T cell receptor (TCR)-mediated sensing of phosphoantigens (PAg) derived from microbes and tumors. However, the molecular rules governing PAg sensing remain largely unknown. Here, we establish three mechanistic principles of PAg-mediated γδ T cell activation.

A partial human LCK defect causes a T cell immunodeficiency with intestinal inflammation.

Lymphocyte-specific protein tyrosine kinase (LCK) is essential for T cell antigen receptor (TCR)-mediated signal transduction. Here, we report two siblings homozygous for a novel LCK variant (c.1318C>T; P440S) characterized by T cell lymphopenia with skewed memory phenotype, infant-onset recurrent infections, failure to thrive, and protracted diarrhea.

Harnessing CD3 diversity to optimize CAR T cells.

Current US Food and Drug Administration-approved chimeric antigen receptor (CAR) T cells harbor the T cell receptor (TCR)-derived ζ chain as an intracellular activation domain in addition to costimulatory domains. The functionality in a CAR format of the other chains of the TCR complex, namely CD3δ, CD3ε and CD3γ, instead of ζ, remains unknown. In the present study, we have systematically engineered new CD3 CARs, each containing only one of the CD3 intracellular domains.

Engineering of an Optogenetic T Cell Receptor Compatible with Fluorescence-Based Readouts.

Optogenetics offers a set of tools for the precise manipulation of signaling pathways. Here we exploit optogenetics to experimentally change the kinetics of protein-protein interactions on demand. We had developed a system in which the interaction of a modified T cell receptor (TCR) with an engineered ligand can be controlled by light.

Opto-APC: Engineering of cells that display phytochrome B on their surface for optogenetic studies of cell-cell interactions.

The kinetics of a ligand-receptor interaction determine the responses of the receptor-expressing cell. One approach to experimentally and reversibly change this kinetics on demand is optogenetics. We have previously developed a system in which the interaction of a modified receptor with an engineered ligand can be controlled by light.

Division of labor and cooperation between different butyrophilin proteins controls phosphoantigen-mediated activation of human γδ T cells.

Butyrophilin (BTN)-3A and BTN2A1 molecules control TCR-mediated activation of human Vγ9Vδ2 T-cells triggered by phosphoantigens (PAg) from microbes and tumors, but the molecular rules governing antigen sensing are unknown. Here we establish three mechanistic principles of PAg-action. Firstly, in humans, following PAg binding to the BTN3A1-B30.

Phenotypic and functional analysis of γδ T cells in the pathogenesis of human T-cell lymphotropic virus type 1 infection.

The human T-cell leukemia virus type 1 (HTLV-1) is the cause of serious malignant and inflammatory diseases, including adult T-cell leukemia and lymphoma and tropical spastic paraparesis. The potential protective role of γδ T cells in HTLV-1 infection remains unclear. Here, demonstrate that there is a decrease in the amount of Vγ9Vδ2 T cells in patients with HTLV-1, especially in those with HTLV-1 associated pathologies.

A set point in the selection of the αβTCR T cell repertoire imposed by pre-TCR signaling strength.

Signaling via the T cell receptor (TCR) is critical during the development, maintenance, and activation of T cells. Quantitative aspects of TCR signaling have an important role during positive and negative selection, lineage choice, and ability to respond to small amounts of antigen. By using a mutant mouse line expressing a hypomorphic allele of the CD3ζ chain, we show here that the strength of pre-TCR–mediated signaling during T cell development determines the diversity of the TCRβ repertoire available for positive and negative selection, and hence of the final αβTCR repertoire.

Cholesterol Binds in a Reversed Orientation to TCRβ-TM in Which Its OH Group is Localized to the Center of the Lipid Bilayer.

T cell receptor (TCR) signaling in response to antigen recognition is essential for the adaptive immune response. Cholesterol keeps TCRs in the resting conformation and mediates TCR clustering by directly binding to the transmembrane domain of the TCRβ subunit (TCRβ-TM), while cholesterol sulfate (CS) displaces cholesterol from TCRβ. However, the atomic interaction of cholesterol or CS with TCRβ remains elusive.

Direct Regulation of the T Cell Antigen Receptor's Activity by Cholesterol.

Biological membranes consist of hundreds of different lipids that together with the embedded transmembrane (TM) proteins organize themselves into small nanodomains. In addition to this function of lipids, TM regions of proteins bind to lipids in a very specific manner, but the function of these TM region-lipid interactions is mostly unknown. In this review, we focus on the role of plasma membrane cholesterol, which directly binds to the αβ T cell antigen receptor (TCR), and has at least two opposing functions in αβ TCR activation.

Tyrosine 192 within the SH2 domain of the Src-protein tyrosine kinase p56 regulates T-cell activation independently of Lck/CD45 interactions.

Background: Upon engagement of the T-cell receptor (TCR), the Src-family protein tyrosine kinase p56Lck phosphorylates components of the TCR (e.g. the TCRζ chains), thereby initiating T-cell activation.