Themis regulates metabolic signaling and effector functions in CD4+ T cells by controlling NFAT nuclear translocation

CD26 CAR-T cells have attenuated mitochondrial and glycolytic metabolic profiling

BACKGROUND

Multiple targets of chimeric antigen receptor T cells (CAR-T cells) are shared expressed by tumor cells and T cells, these self-antigens may stimulate CAR-T cells continuously during the expansion. Persistent exposure to antigens is considered to cause metabolic reprogramming of T cells and the metabolic profiling is critical in determining the cell fate and effector function of CAR-T cells. However, whether the stimulation of self-antigens during CAR-T cell generation could remodel the metabolic profiling is unclear. In this study, we aim to investigate the metabolic characteristics of CD26 CAR-T cells, which expressed CD26 antigens themselves.

METHODS

The mitochondrial biogenesis of CD26 and CD19 CAR-T cells during expansion was evaluated by the mitochondrial content, mitochondrial DNA copy numbers and genes involved in mitochondrial regulation. The metabolic profiling was investigated by the ATP production, mitochondrial quality and the expression of metabolism-related genes. Furthermore, we assessed the phenotypes of CAR-T cells through memory-related markers.

RESULTS

We reported that CD26 CAR-T cells had elevated mitochondrial biogenesis, ATP production and oxidative phosphorylation at early expansion stage. However, the mitochondrial biogenesis, mitochondrial quality, oxidative phosphorylation and glycolytic activity were all weakened at later expansion stage. On the contrary, CD19 CAR-T cells did not exhibit such characteristics.

CONCLUSION

CD26 CAR-T cells showed distinctive metabolic profiling during expansion that was extremely unfavorable to cell persistence and function. These findings may provide new insights for the optimization of CD26 CAR-T cells in terms of metabolism.

Themis controls T cell activation, effector functions, and metabolism of peripheral CD8+ T cells

Themis is important in regulating positive selection of thymocytes during T cell development, but its role in peripheral T cells is less understood. Here, we investigated T cell activation and its sequelae using a tamoxifen-mediated, acute Themis deletion mouse model. We find that proliferation, effector functions including anti-tumor killing, and up-regulation of energy metabolism are severely compromised. This study reveals the phenomenon of peripheral adaptation to loss of Themis, by demonstrating direct TCR-induced defects after acute deletion of Themis that were not evident in peripheral T cells chronically deprived of Themis in dLck-Cre deletion model. Peripheral adaptation to long-term loss was compared using chronic versus acute tamoxifen-mediated deletion and with the (chronic) dLck-Cre deletion model. We found that upon chronic tamoxifen-mediated Themis deletion, there was modulation in the gene expression profile for both TCR and cytokine signaling pathways. This profile overlapped with (chronic) dLck-Cre deletion model. Hence, we found that peripheral adaptation induced changes to both TCR and cytokine signaling modules. Our data highlight the importance of Themis in the activation of CD8+ T cells.

The relationship between CD4+ T cell glycolysis and their functions

CD4⁺ T cells are effector T cells (Teffs) produced by the differentiation of initial T cells in peripheral lymphoid tissue after being attacked by antigens, and have an indispensable role in the development and activation of B cells and CD8⁺ T cells to regulate and assist immunity. In this review, we provide a new perspective on the relationship between CD4⁺ T cell glycolysis and its function. We summarize the effects of changes in the glycolysis level of CD4⁺ T cells on their activation, differentiation, proliferation, and survival. In addition, we emphasize that regulation of the glycolysis level of CD4⁺ T cells changes their inflammatory phenotypes and function. The study of immune metabolism has received more attention recently, but more work is needed to answer many open questions.

Themis suppresses the effector function of CD8+ T cells in acute viral infection

CD8⁺ T cells play a central role in antiviral immune responses. Upon infection, naive CD8⁺ T cells differentiate into effector cells to eliminate virus-infected cells, and some of these effector cells further differentiate into memory cells to provide long-term protection after infection is resolved. Although extensively investigated, the underlying mechanisms of CD8⁺ T-cell differentiation remain incompletely understood. Themis is a T-cell-specific protein that plays critical roles in T-cell development. Recent studies using Themis T-cell conditional knockout mice also demonstrated that Themis is required to promote mature CD8⁺ T-cell homeostasis, cytokine responsiveness, and antibacterial responses. In this study, we used LCMV Armstrong infection as a probe to explore the role of Themis in viral infection. We found that preexisting CD8⁺ T-cell homeostasis defects and cytokine hyporesponsiveness do not impair viral clearance in Themis T-cell conditional knockout mice. Further analyses showed that in the primary immune response, Themis deficiency promoted the differentiation of CD8⁺ effector cells and increased their TNF and IFNγ production. Moreover, Themis deficiency impaired memory precursor cell (MPEC) differentiation but promoted short-lived effector cell (SLEC) differentiation. Themis deficiency also enhanced effector cytokine production in memory CD8⁺ T cells while impairing central memory CD8⁺ T-cell formation. Mechanistically, we found that Themis mediates PD-1 expression and its signaling in effector CD8⁺ T cells, which explains the elevated cytokine production in these cells when Themis is disrupted.

Negative times negative equals positive, THEMIS sets the rule on thymic selection and peripheral T cell responses

The activity of T cells is finely controlled by a set of negative regulators of T-cell antigen receptor (TCR)-mediated signaling. However, how those negative regulators are themselves controlled to prevent ineffective TCR-mediated responses remain poorly understood. Thymocyte-expressed molecule involved in selection (THEMIS) has been characterized over a decade ago as an important player of T cell development. Although the molecular function of THEMIS has long remained puzzling and subject to controversies, latest investigations suggest that THEMIS stimulates TCR-mediated signaling by repressing the tyrosine phosphatases SHP-1 and SHP-2 which exert regulatory function on T cell activation. Recent evidences also point to a role for THEMIS in peripheral T cells beyond its role on thymic selection. Here, we present an overview of the past research on THEMIS in the context of T cell development and peripheral T cell function and discuss the possible implication of THEMIS-based mechanisms on TCR-dependent and independent signaling outcomes.

Themis is indispensable for IL-2 and IL-15 signaling in T cells

To perform their antiviral and antitumor functions, T cells must integrate signals both from the T cell receptor (TCR), which instruct the cell to remain quiescent or become activated, and from cytokines that guide cellular proliferation and differentiation. In mature CD8⁺ T cells, Themis has been implicated in integrating TCR and cytokine signals. We investigated whether Themis plays a direct role in cytokine signaling in mature T cells. Themis was required for IL-2- and IL-15-driven CD8⁺ T cell proliferation both in mice and in vitro. Mechanistically, we found that Themis promoted the activation of the transcription factor Stat and mechanistic target of rapamycin signaling downstream of cytokine receptors. Metabolomics and stable isotope tracing analyses revealed that Themis deficiency reduced glycolysis and serine and nucleotide biosynthesis, demonstrating a receptor-proximal requirement for Themis in triggering the metabolic changes that enable T cell proliferation. The cellular, metabolic, and biochemical defects caused by Themis deficiency were corrected in mice lacking both Themis and the phosphatase Shp1, suggesting that Themis mediates IL-2 and IL-15 receptor-proximal signaling by restraining the activity of Shp1. Together, these results not only shed light on the mechanisms of cytokine signaling but also provide new clues on manipulating T cells for clinical applications.

Function and Molecular Mechanism of the DNA Damage Response in Immunity and Cancer Immunotherapy

The DNA damage response (DDR) is an organized network of multiple interwoven components evolved to repair damaged DNA and maintain genome fidelity. Conceptually the DDR includes damage sensors, transducer kinases, and effectors to maintain genomic stability and accurate transmission of genetic information. We have recently gained a substantially improved molecular and mechanistic understanding of how DDR components are interconnected to inflammatory and immune responses to stress. DDR shapes both innate and adaptive immune pathways: (i) in the context of innate immunity, DDR components mainly enhance cytosolic DNA sensing and its downstream STimulator of INterferon Genes (STING)-dependent signaling; (ii) in the context of adaptive immunity, the DDR is needed for the assembly and diversification of antigen receptor genes that is requisite for T and B lymphocyte development. Imbalances between DNA damage and repair impair tissue homeostasis and lead to replication and transcription stress, mutation accumulation, and even cell death. These impacts from DDR defects can then drive tumorigenesis, secretion of inflammatory cytokines, and aberrant immune responses. Yet, DDR deficiency or inhibition can also directly enhance innate immune responses. Furthermore, DDR defects plus the higher mutation load in tumor cells synergistically produce primarily tumor-specific neoantigens, which are powerfully targeted in cancer immunotherapy by employing immune checkpoint inhibitors to amplify immune responses. Thus, elucidating DDR-immune response interplay may provide critical connections for harnessing immunomodulatory effects plus targeted inhibition to improve efficacy of radiation and chemotherapies, of immune checkpoint blockade, and of combined therapeutic strategies.

Circ_0001944 Contributes to Glycolysis and Tumor Growth by Upregulating NFAT5 Through Acting as a Decoy for miR-142-5p in Non-Small Cell Lung Cancer

Background

Circular RNAs (circRNAs) participate in the tumorigenesis of various cancers. CircRNA hsa_circ_0001944 (circ_0001944), derived from the TCONS_l2_00030860 gene, has been uncovered to be upregulated in NSCLC (non-small cell lung cancer). Nevertheless, the influence of circ_0001944 on glycolysis and tumor growth in NSCLC is unclear.

Methods

Expression trend of circ_0001944 in NSCLC tissues and cells were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). Loss-of-function experiments were performed to assess the influence of circ_0001944 knockdown on proliferation, migration, invasion, and glycolysis of NSCLC cells. Protein levels were assessed by Western blotting. The regulatory mechanism of circ_0001944 was analyzed by bioinformatics analysis, dual-luciferase reporter assay, and/or RNA pull-down assay. The tumorigenicity of circ_0001944 was confirmed by xenograft assay.

Results

Circ_0001944 was highly expressed in NSCLC, and NSCLC patients with high expression of circ_0001944 had a worse prognosis. Circ_0001944 silencing decreased xenograft tumor growth in vivo and repressed proliferation, migration, invasion, and glycolysis of NSCLC cells in vitro. Circ_0001944 was verified as a decoy for microRNA (miR)-142-5p, which targeted NFAT5 (nuclear factor of activated T cells 5). MiR-142-5p was downregulated while NFAT5 was upregulated in NSCLC. Both miR-142-5p inhibition and NFAT5 overexpression offset the suppressive impact of circ_0001944 silencing on proliferation, migration, invasion, and glycolysis of NSCLC cells. Circ_0001944 adsorbed miR-142-5p to elevate NFAT5 expression in NSCLC cells.

Conclusion

Circ_0001944 promotes proliferation, migration, invasion, and glycolysis of NSCLC cells by upregulating NFAT5 through adsorbing miR-142-5p, offering a novel mechanism for understanding the advancement of NSCLC.

Expansion of an Unusual Virtual Memory CD8+ Subpopulation Bearing Vα3.2 TCR in Themis-Deficient Mice

Deletion of the gene for Themis affects T cell selection in the thymus, which would be expected to affect the TCR repertoire. We found an increased proportion of cells expressing Vα3.2 (TRAV9N-3) in the peripheral CD8⁺ T cell population in mice with germline Themis deficiency. Analysis of the TCRα repertoire indicated it was generally reduced in diversity in the absence of Themis, whereas the diversity of sequences using the TRAV9N-3 V-region element was increased. In wild type mice, Vα3.2⁺ cells showed higher CD5, CD6 and CD44 expression than non-Vα3-expressing cells, and this was more marked in cells from Themis-deficient mice. This suggested a virtual memory phenotype, as well as a stronger response to self-pMHC. The Vα3.2⁺ cells responded more strongly to IL-15, as well as showing bystander effector capability in a Listeria infection. Thus, the unusually large population of Vα3.2⁺ CD8⁺ T cells found in the periphery of Themis-deficient mice reflects not only altered thymic selection, but also allowed identification of a subset of bystander-competent cells that are also present in wild-type mice.

The Ups and Downs of Metabolism during the Lifespan of a T Cell

Understanding the various mechanisms that govern the development, activation, differentiation, and functions of T cells is crucial as it could provide opportunities for therapeutic interventions to disrupt immune pathogenesis. Immunometabolism is one such area that has garnered significant interest in the recent past as it has become apparent that cellular metabolism is highly dynamic and has a tremendous impact on the ability of T cells to grow, activate, and differentiate. In each phase of the lifespan of a T-cell, cellular metabolism has to be tailored to match the specific functional requirements of that phase. Resting T cells rely on energy-efficient oxidative metabolism but rapidly shift to a highly glycolytic metabolism upon activation in order to meet the bioenergetically demanding process of growth and proliferation. However, upon antigen clearance, T cells return to a more quiescent oxidative metabolism to support T cell memory generation. In addition, each helper T cell subset engages distinct metabolic pathways to support their functional needs. In this review, we provide an overview of the metabolic changes that occur during the lifespan of a T cell and discuss several important studies that provide insights into the regulation of the metabolic landscape of T cells and how they impact T cell development and function.