Modulation of T Cell Metabolism and Function through Calcium Signaling

Development of an anoikis-related gene signature and prognostic model for predicting the tumor microenvironment and response to immunotherapy in colorectal cancer

The effect of anoikis-related genes (ARGs) on clinicopathological characteristics and tumor microenvironment remains unclear. We comprehensively analyzed anoikis-associated gene signatures of 1057 colorectal cancer (CRC) samples based on 18 ARGs. Anoikis-related molecular subtypes and gene features were identified through consensus clustering analysis. The biological functions and immune cell infiltration were assessed using the GSVA and ssGSEA algorithms. Prognostic risk score was constructed using multivariate Cox regression analysis. The immunological features of high-risk and low-risk groups were compared. Finally, DAPK2-overexpressing plasmid was transfected to measure its effect on tumor proliferation and metastasis in vitro and in vivo. We identified 18 prognostic ARGs. Three different subtypes of anoikis were identified and demonstrated to be linked to distinct biological processes and prognosis. Then, a risk score model was constructed and identified as an independent prognostic factor. Compared to the high-risk group, patients in the low-risk group exhibited longer survival, higher enrichment of checkpoint function, increased expression of CTLA4 and PD-L1, higher IPS scores, and a higher proportion of MSI-H. The results of RT-PCR indicated that the expression of DAPK2 mRNA was significantly downregulated in CRC tissues compared to normal tissues. Increased DAPK2 expression significantly suppressed cell proliferation, promoted apoptosis, and inhibited migration and invasion. The nude mice xenograft tumor model confirmed that high expression of DAPK2 inhibited tumor growth. Collectively, we discovered an innovative anoikis-related gene signature associated with prognosis and TME. Besides, our study indicated that DAPK2 can serve as a promising therapeutic target for inhibiting the growth and metastasis of CRC.

Extracellular Delivery of Functional Mitochondria Rescues the Dysfunction of CD4+ T Cells in Aging

Mitochondrial dysfunction alters cellular metabolism, increases tissue oxidative stress, and may be principal to the dysregulated signaling and function of CD4+ T lymphocytes in the elderly. In this proof of principle study, it is investigated whether the transfer of functional mitochondria into CD4+ T cells that are isolated from old mice (aged CD4+ T cells), can abrogate aging-associated mitochondrial dysfunction, and improve the aged CD4+ T cell functionality. The results show that the delivery of exogenous mitochondria to aged non-activated CD4+ T cells led to significant mitochondrial proteome alterations highlighted by improved aerobic metabolism and decreased cellular mitoROS. Additionally, mito-transferred aged CD4+ T cells showed improvements in activation-induced TCR-signaling kinetics displaying markers of activation (CD25), increased IL-2 production, enhanced proliferation ex vivo. Importantly, immune deficient mouse models (RAG-KO) showed that adoptive transfer of mito-transferred naive aged CD4+ T cells, protected recipient mice from influenza A and Mycobacterium tuberculosis infections. These findings support mitochondria as targets of therapeutic intervention in aging.

Prediction of Protein Ion-Ligand Binding Sites with ELECTRA

Interactions between proteins and ions are essential for various biological functions like structural stability, metabolism, and signal transport. Given that more than half of all proteins bind to ions, it is becoming crucial to identify ion-binding sites. The accurate identification of protein-ion binding sites helps us to understand proteins' biological functions and plays a significant role in drug discovery. While several computational approaches have been proposed, this remains a challenging problem due to the small size and high versatility of metals and acid radicals. In this study, we propose IonPred, a sequence-based approach that employs ELECTRA (Efficiently Learning an Encoder that Classifies Token Replacements Accurately) to predict ion-binding sites using only raw protein sequences. We successfully fine-tuned our pretrained model to predict the binding sites for nine metal ions (Zn2+, Cu2+, Fe2+, Fe3+, Ca2+, Mg2+, Mn2+, Na+, and K+) and four acid radical ion ligands (CO32-, SO42-, PO43-, NO2-). IonPred surpassed six current state-of-the-art tools by over 44.65% and 28.46%, respectively, in the F1 score and MCC when compared on an independent test dataset. Our method is more computationally efficient than existing tools, producing prediction results for a hundred sequences for a specific ion in under ten minutes.

Linking antigen specific T-cell dynamics in a microfluidic chip to single cell transcription patterns

A new non-invasive screening profile has been realized that can aid in determining T-cell activation state at single-cell level. Production of activated T-cells with good specificity and stable proliferation is greatly beneficial for advancing adoptive immunotherapy as innate immunological cells are not effective in recognizing and eliminating cancer as expected. The screening method is realized by relating intracellular Ca²⁺ intensity and motility of T-cells interacting with APC (Antigen Presenting Cells) in a microfluidic chip. The system is tested using APC pulsed with OVA_257-264 peptide and its modified affinities (N4, Q4, T4 and V4), and the T-cells from OT-1 mice. In addition, single cell RNA sequencing reveals the activation states of the cells and the clusters from the derived profiles can be indicative of the T-cell activation state. The presented system here can be versatile for a comprehensive application to proceed with T-cell-based immunotherapy and screen the antigen-specific T-cells with excellent efficiency and high proliferation.

Immune determinants of the pre-metastatic niche

Primary tumors actively and specifically prime pre-metastatic niches (PMNs), the future sites of organotropic metastasis, preparing these distant microenvironments for disseminated tumor cell arrival. While initial studies of the PMN focused on extracellular matrix alterations and stromal reprogramming, it is increasingly clear that the far-reaching effects of tumors are in great part achieved through systemic and local PMN immunosuppression. Here, we discuss recent advances in our understanding of the tumor immune microenvironment and provide a comprehensive overview of the immune determinants of the PMN's spatiotemporal evolution. Moreover, we depict the PMN immune landscape, based on functional pre-clinical studies as well as mounting clinical evidence, and the dynamic, reciprocal crosstalk with systemic changes imposed by cancer progression. Finally, we outline emerging therapeutic approaches that alter the dynamics of the interactions driving PMN formation and reverse immunosuppression programs in the PMN ensuring early anti-tumor immune responses.

DRAK2 contributes to type 1 diabetes by negatively regulating IL-2 sensitivity to alter regulatory T cell development

Drak2-deficient (Drak2-/-) mice are resistant to multiple models of autoimmunity yet effectively eliminate pathogens and tumors. Thus, DRAK2 represents a potential target to treat autoimmune diseases. However, the mechanisms by which DRAK2 contributes to autoimmunity, particularly type 1 diabetes (T1D), remain unresolved. Here, we demonstrate that resistance to T1D in non-obese diabetic (NOD) mice is due to the absence of Drak2 in T cells and requires the presence of regulatory T cells (Tregs). Contrary to previous hypotheses, we show that DRAK2 does not limit TCR signaling. Rather, DRAK2 regulates IL-2 signaling by inhibiting STAT5A phosphorylation. We further demonstrate that enhanced sensitivity to IL-2 in the absence of Drak2 augments thymic Treg development. Overall, our data indicate that DRAK2 contributes to autoimmunity in multiple ways by regulating thymic Treg development and by impacting the sensitivity of conventional T cells to Treg-mediated suppression.

Age-associated remodeling of T cell immunity and metabolism

Aging results in remodeling of T cell immunity and is associated with poor clinical outcomes in age-related diseases such as cancer. Among the hallmarks of aging, changes in host and cellular metabolism critically affect the development, maintenance, and function of T cells. Although metabolic perturbations impact anti-tumor T cell responses, the link between age-associated metabolic dysfunction and anti-tumor immunity remains unclear. In this review, we summarize recent advances in our understanding of aged T cell metabolism, with a focus on the bioenergetic and immunologic features of T cell subsets unique to the aging process. We also survey insights into mechanisms of metabolic T cell dysfunction in aging and discuss the impacts of aging on the efficacy of cancer immunotherapy. As the average life expectancy continues to increase, understanding the interplay between age-related metabolic reprogramming and maladaptive T cell immunity will be instrumental for the development of therapeutic strategies for older patients.

Mitochondria dysfunction in CD8+ T cells as an important contributing factor for cancer development and a potential target for cancer treatment: a review

CD8+ T cells play a central role in anti-tumor immunity. Naïve CD8+ T cells are active upon tumor antigen stimulation, and then differentiate into functional cells and migrate towards the tumor sites. Activated CD8+ T cells can directly destroy tumor cells by releasing perforin and granzymes and inducing apoptosis mediated by the death ligand/death receptor. They also secrete cytokines to regulate the immune system against tumor cells. Mitochondria are the central hub of metabolism and signaling, required for polarization, and migration of CD8+ T cells. Many studies have demonstrated that mitochondrial dysfunction impairs the anti-tumor activity of CD8+ T cells through various pathways. Mitochondrial energy metabolism maladjustment will cause a cellular energy crisis in CD8+ T cells. Abnormally high levels of mitochondrial reactive oxygen species will damage the integrity and architecture of biofilms of CD8+ T cells. Disordered mitochondrial dynamics will affect the mitochondrial number and localization within cells, further affecting the function of CD8+ T cells. Increased mitochondria-mediated intrinsic apoptosis will decrease the lifespan and quantity of CD8+ T cells. Excessively low mitochondrial membrane potential will cause the release of cytochrome c and apoptosis of CD8+ T cells, while excessively high will exacerbate oxidative stress. Dysregulation of mitochondrial Ca2+ signaling will affect various physiological pathways in CD8+ T cells. To some extent, mitochondrial abnormality in CD8+ T cells contributes to cancer development. So far, targeting mitochondrial energy metabolism, mitochondrial dynamics, mitochondria-mediated cell apoptosis, and other mitochondrial physiological processes to rebuild the anti-tumor function of CD8+ T cells has proved effective in some cancer models. Thus, mitochondria in CD8+ T cells may be a potential and powerful target for cancer treatment in the future.

New insights into the characteristics of DRAK2 and its role in apoptosis: From molecular mechanisms to clinically applied potential

As a member of the death-associated protein kinase (DAPK) family, DAP kinase-associated apoptosis-inducing kinase 2 (DRAK2) performs apoptosis-related functions. Compelling evidence suggests that DRAK2 is involved in regulating the activation of T lymphocytes as well as pancreatic β-cell apoptosis in type I diabetes. In addition, DRAK2 has been shown to be involved in the development of related tumor and non-tumor diseases through a variety of mechanisms, including exacerbation of alcoholic fatty liver disease (NAFLD) through SRSF6-associated RNA selective splicing mechanism, regulation of chronic lymphocytic leukemia and acute myeloid leukemia, and progression of colorectal cancer. This review focuses on the structure, function, and upstream pathways of DRAK2 and discusses the potential and challenges associated with the clinical application of DRAK2-based small-molecule inhibitors, with the aim of advancing DRAK2 research.

Molecular hydrogen has a positive impact on pregnancy maintenance through enhancement of mitochondrial function and immunomodulatory effects on T cells

AIMS

Molecular hydrogen (H₂) has attracted growing interest because of its implications in various diseases. However, the molecular mechanisms underlying the remarkable effect of a small amount of H₂ remain elusive. No knowledge has been available on the role of H₂ in the etiology of pregnancy disorders or its direct influence on human immune cells. Since maternal immunity, T cells in particular, plays a critical role in pregnancy maintenance. We investigated the effects of H₂ on T cells and its relation to preterm birth (PTB).

MAIN METHODS

Exhaled H₂ concentrations in pregnant women were measured and correlated with cytokine concentrations in maternal and umbilical cord blood. H₂ was added to T cells collected from healthy donors, and differentiation and proliferation were examined. Energy metabolism was also examined. H₂ was administered to mice and cytokine expression was compared.

KEY FINDINGS

Our prospective observational study revealed that maternal production of H₂ is significantly lower in pregnant women with PTB, suggesting its potential as a biomarker for predicting PTB. We found that H₂ has clear associations with several maternal cytokines, and acts as an immunomodulator by exerting mitochondrial function in human T cells. Moreover, in vivo administration of H₂ to pregnant mice regulated inflammatory responses and reduced PTB caused by T cell activation, which further supports the notion that H₂ may contribute to prolonged gestation through its immunomodulatory effect.

SIGNIFICANCE

Measuring maternal H₂-production could be a potential clinical tool in the management of PTB, and H₂ may have positive impact on pregnancy maintenance.

A Dual-Purpose Real-Time Indicator and Transcriptional Integrator for Calcium Detection in Living Cells

Calcium is a ubiquitous second messenger in eukaryotes, correlated with neuronal activity and T-cell activation among other processes. Real-time calcium indicators such as GCaMP have recently been complemented by newer calcium integrators that convert transient calcium activity into stable gene expression. Here we introduce LuCID, a dual-purpose real-time calcium indicator and transcriptional calcium integrator that combines the benefits of both calcium detection technologies. We show that the calcium-dependent split luciferase component of LuCID provides a real-time bioluminescence readout of calcium dynamics in cells, while the GI/FKF1 split GAL4 component of LuCID converts calcium-generated bioluminescence into stable gene expression. We also show that LuCID's modular design enables it to read out other cellular events such as protein-protein interactions. LuCID adds to the arsenal of tools for studying cells and cell populations that utilize calcium for signaling.

Nuclear Transporting Factor 2 as a Novel Biomarker of Head and Neck Squamous Cell Carcinoma and Associated with T/B Cell Receptor Signaling Pathway

Objective

This study is aimed at exploring the role of nuclear transporting factor 2 (NUTF2) in head and neck squamous cell carcinoma (HNSCC) based on The Cancer Genome Atlas (TCGA) database.

Methods

We obtained 528 HNSCC patients' clinical data from TCGA and performed expression level analysis of NUTF2. Gene Sets Enrichment Analysis (GSEA) was conducted to identify NUTF2-associated regulatory mechanisms in HNSCC. In addition, several other tools were used to enrich the regulatory network.

Results

We found that NUTF2 was significantly upregulated (P < 0.001) in HNSCC. We then observed that higher NUTF2 is associated with poorer overall survival and disease-free survival. Further, by using Cox analyses, we determined high NUTF2 as an independent risk factor of predicting poorer overall survival. Tumor immune infiltration analysis revealed a significantly negative correlation between NUTF2 expression and the level of tumor infiltrated CD8⁺ T cell and B cell, suggesting that NUTF2 may be involved in the immune regulation of HNSCC. Gene sets related to T/B cell receptor signaling pathways were differentially enriched based on the NUTF2 expression phenotype. KEGG pathways were used to show that NUTF2 may affect proliferation, differentiation, and immune response of T/B cell through regulating PI3K/AKT, NFκB, MAPK, and Calcium signaling pathways.

Conclusion

NUTF2 might be a valuable biomarker for HNSCC and correlated with T/B cell receptor signaling pathway.

Deregulated calcium signaling in blood cancer: Underlying mechanisms and therapeutic potential

Intracellular calcium signaling regulates diverse physiological and pathological processes. In solid tumors, changes to calcium channels and effectors via mutations or changes in expression affect all cancer hallmarks. Such changes often disrupt transport of calcium ions (Ca²⁺) in the endoplasmic reticulum (ER) or mitochondria, impacting apoptosis. Evidence rapidly accumulates that this is similar in blood cancer. Principles of intracellular Ca²⁺ signaling are outlined in the introduction. We describe different Ca²⁺-toolkit components and summarize the unique relationship between extracellular Ca²⁺ in the endosteal niche and hematopoietic stem cells. The foundational data on Ca²⁺ homeostasis in red blood cells is discussed, with the demonstration of changes in red blood cell disorders. This leads to the role of Ca²⁺ in neoplastic erythropoiesis. Then we expand onto the neoplastic impact of deregulated plasma membrane Ca²⁺ channels, ER Ca²⁺ channels, Ca²⁺ pumps and exchangers, as well as Ca²⁺ sensor and effector proteins across all types of hematologic neoplasms. This includes an overview of genetic variants in the Ca²⁺-toolkit encoding genes in lymphoid and myeloid cancers as recorded in publically available cancer databases. The data we compiled demonstrate that multiple Ca²⁺ homeostatic mechanisms and Ca²⁺ responsive pathways are altered in hematologic cancers. Some of these alterations may have genetic basis but this requires further investigation. Most changes in the Ca²⁺-toolkit do not appear to define/associate with specific disease entities but may influence disease grade, prognosis, treatment response, and certain complications. Further elucidation of the underlying mechanisms may lead to novel treatments, with the aim to tailor drugs to different patterns of deregulation. To our knowledge this is the first review of its type in the published literature. We hope that the evidence we compiled increases awareness of the calcium signaling deregulation in hematologic neoplasms and triggers more clinical studies to help advance this field.

Continuous Modeling of T CD4 Lymphocyte Activation and Function

T CD4+ cells are central to the adaptive immune response against pathogens. Their activation is induced by the engagement of the T-cell receptor by antigens, and of co-stimulatory receptors by molecules also expressed on antigen presenting cells. Then, a complex network of intracellular events reinforce, diversify and regulate the initial signals, including dynamic metabolic processes that strongly influence both the activation state and the differentiation to effector cell phenotypes. The regulation of cell metabolism is controlled by the nutrient sensor adenosine monophosphate-activated protein kinase (AMPK), which drives the balance between oxidative phosphorylation (OXPHOS) and glycolysis. Herein, we put forward a 51-node continuous mathematical model that describes the temporal evolution of the early events of activation, integrating a circuit of metabolic regulation into the main routes of signaling. The model simulates the induction of anergy due to defective co-stimulation, the CTLA-4 checkpoint blockade, and the differentiation to effector phenotypes induced by external cytokines. It also describes the adjustment of the OXPHOS-glycolysis equilibrium by the action of AMPK as the effector function of the T cell develops. The development of a transient phase of increased OXPHOS before induction of a sustained glycolytic phase during differentiation to the Th1, Th2 and Th17 phenotypes is shown. In contrast, during Treg differentiation, glycolysis is subsequently reduced as cell metabolism is predominantly polarized towards OXPHOS. These observations are in agreement with experimental data suggesting that OXPHOS produces an ATP reservoir before glycolysis boosts the production of metabolites needed for protein synthesis, cell function, and growth.

Prediction of Metal Ion Binding Sites of Transmembrane Proteins

The metal ion binding of transmembrane proteins (TMPs) plays a fundamental role in biological processes, pharmaceutics, and medicine, but it is hard to extract enough TMP structures in experimental techniques to discover their binding mechanism comprehensively. To predict the metal ion binding sites for TMPs on a large scale, we present a simple and effective two-stage prediction method TMP-MIBS, to identify the corresponding binding residues using TMP sequences. At present, there is no specific research on the metal ion binding prediction of TMPs. Thereby, we compared our model with the published tools which do not distinguish TMPs from water-soluble proteins. The results in the independent verification dataset show that TMP-MIBS has superior performance. This paper explores the interaction mechanism between TMPs and metal ions, which is helpful to understand the structure and function of TMPs and is of great significance to further construct transport mechanisms and identify potential drug targets.

A calmodulin targeted by miRNA scaffold659_26519 regulates IL-17 expression in the early immune response of oyster Crassostrea gigas

Calmodulin (CaM) is a highly conserved second messenger protein transducing calcium signals by binding and modulating intracellular calcium ions (Ca²⁺), and involves in the Ca²⁺-dependent physical processes including host defense in vertebrates. In the present study, a CaM homologue (designated as CgCaM) was identified from Pacific oyster Crassostrea gigas. The open reading frame of CgCaM cDNA was of 471 bp encoding a polypeptide of 156 amino acid residues. There were four EFh domains predicted in CgCaM, which shared high homologies with those in CaMs from oyster C. virginica and other invertebrates. The mRNA transcripts of CgCaM were constitutively expressed in all the tested tissues including labellum, mantle, gonad, gills, adductor muscle, haemocytes and hepatopancreas, with the highest expression level in haemocytes. The mRNA expression level of CgCaM in haemocytes decreased significantly (0.31-fold of that in blank, p < 0.05) at 3 h after LPS stimulation, while the intracellular Ca²⁺ (1.57-fold of that in blank, p < 0.05) and the mRNA expression of cytokine CgIL17-1 (4.87-fold of that in blank, p < 0.05) both increased in haemocytes. Meanwhile, an oyster miRNA scaffold659_26519 was identified, and it was proved to target the 3'-untranslated regions (3'-UTR) of CgCaM mRNA by luciferase reporter assay. The expression of scaffold659_26519 increased significantly at 3 h (43.523-fold of that of blank, p < 0.05) and 6 h (55.91-fold of that of blank, p < 0.05) after LPS stimulation. When the expression of scaffold659_26519 was inhibited by transfection with its inhibitor in vitro, the expression of CgIL17-1 declined significantly to 0.58-fold of that in LPS stimulation group. These findings indicated that the miRNA scaffold659_26519 targeted CaM was involved in the early inflammatory response of oyster immunity, and provided a new evidence for CaM-mediated immune mechanism in molluscs.

Regulatory T cells are less sensitive to glucocorticoid hormone induced apoptosis than CD4+ T cells

Earlier we have reported that thymic regulatory T cells (Treg) are resistant to in vivo glucocorticoid hormone (GC)-induced apoptosis, while the most GC-sensitive DP thymocytes died through the activation of mitochondrial apoptotic pathway. Here we analyzed the apoptosis-inducing effect of high dose (10^-6 M) in vitro dexamethasone (DX) treatment in mouse thymic- and splenic Tregs and CD4⁺ T cells. Activation of both extrinsic and intrinsic apoptotic pathways started after 2 h of DX treatment in CD4 SP thymocytes and was 3 × higher than in CD4⁺ splenocytes, while in Treg cells, weak activation of the extrinsic apoptotic pathway started only after 3 h. We also investigated the expression of 21 apoptosis-related molecules using a protein array and found higher level of both pro-and anti-apoptotic molecules in Tregs compared to CD4⁺ T cells. 4 h in vitro DX treatment induced upregulation of most apoptosis-related molecules both in Tregs and CD4⁺ T cells, except for the decrease of Bcl-2 expression in CD4⁺ T cells. We found high basal cytosolic Ca²⁺ levels in untreated Treg cells, which further increased after DX treatment, while the specific TCR-induced Ca²⁺ signal was lower in Tregs than in CD4⁺ T cells. Our results suggest that in the background of the relative apoptosis resistance of Treg cells to GCs might be their high basal cytosolic Ca²⁺ level and upregulated Bcl-2 expression. In contrast, downregulation of Bcl-2 expression in CD4⁺ T cells can explain their higher, DX-induced apoptosis sensitivity.

Methylome Patterns of Cattle Adaptation to Heat Stress

Heat stress has a detrimental impact on cattle health, welfare and productivity by affecting gene expression, metabolism and immune response, but little is known on the epigenetic mechanisms mediating the effect of temperature at the cellular and organism level. In this study, we investigated genome-wide DNA methylation in blood samples collected from 5 bulls of the heat stress resilient Nellore breed and 5 bulls of the Angus that are more heat stress susceptible, exposed to the sun and high temperature-high humidity during the summer season of the Brazilian South-East region. The methylomes were analyzed during and after the exposure by Reduced Representation Bisulfite Sequencing, which provided genome-wide single-base resolution methylation profiles. Significant methylation changes between stressful and recovery periods were observed in 819 genes. Among these, 351 were only seen in Angus, 366 were specific to Nellore, and 102 showed significant changes in methylation patterns in both breeds. KEGG and Gene Ontology (GO) enrichment analyses showed that responses were breed-specific. Interestingly, in Nellore significant genes and pathways were mainly involved in stress responses and cellular defense and were under methylated during heat stress, whereas in Angus the response was less focused. These preliminary results suggest that heat challenge induces changes in methylation patterns in specific loci, which should be further scrutinized to assess their role in heat tolerance.

Single-cell analysis by mass cytometry reveals metabolic states of early-activated CD8+ T cells during the primary immune response

Memory T cells are thought to rely on oxidative phosphorylation and short-lived effector T cells on glycolysis. Here, we investigated how T cells arrive at these states during an immune response. To understand the metabolic state of rare, early-activated T cells, we adapted mass cytometry to quantify metabolic regulators at single-cell resolution in parallel with cell signaling, proliferation, and effector function. We interrogated CD8+ T cell activation in vitro and in response to Listeria monocytogenes infection in vivo. This approach revealed a distinct metabolic state in early-activated T cells characterized by maximal expression of glycolytic and oxidative metabolic proteins. Cells in this transient state were most abundant 5 days post-infection before rapidly decreasing metabolic protein expression. Analogous findings were observed in chimeric antigen receptor (CAR) T cells interrogated longitudinally in advanced lymphoma patients. Our study demonstrates the utility of single-cell metabolic analysis by mass cytometry to identify metabolic adaptations of immune cell populations in vivo and provides a resource for investigations of metabolic regulation of immune responses across a variety of applications.

Control of T Cell Metabolism by Cytokines and Hormones

Dynamic, coordinated changes in metabolic pathway activity underpin the protective and inflammatory activity of T cells, through provision of energy and biosynthetic precursors for effector functions, as well as direct effects of metabolic enzymes, intermediates and end-products on signaling pathways and transcriptional mechanisms. Consequently, it has become increasingly clear that the metabolic status of the tissue microenvironment directly influences T cell activity, with changes in nutrient and/or metabolite abundance leading to dysfunctional T cell metabolism and interlinked immune function. Emerging evidence now indicates that additional signals are integrated by T cells to determine their overall metabolic phenotype, including those arising from interaction with cytokines and hormones in their environment. The impact of these on T cell metabolism, the mechanisms involved and the pathological implications are discussed in this review article.

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

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

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

The venom proteome of three common scyphozoan jellyfishes (Chrysaora caliparea, Cyanea nozakii and Lychnorhiza malayensis) (Cnidaria: Scyphozoa) from the coastal waters of India

The jellyfish venom stored in nematocysts contains highly toxic compounds comprising of polypeptides, enzymes and other proteins, which form their chemical defence armoury against predators. We have characterized the proteome of crude venom extract from three bloom-forming scyphozoan jellyfish along the south-west coast of India, Chrysaora caliparea, Cyanea nozakii and Lychnorhiza malayensis using a Quadrupole-Time of Flight (Q/TOF) mass spectrometry analysis. The most abundant toxin identified from Chrysaora caliparea and Lychnorhiza malayensis is similar to the pore-forming toxins and metalloproteinases. A protective antioxidant enzyme called peroxiredoxin was found abundantly in Cyanea nozakii. Metalloproteinase identified from the C. caliparea shows similarity with the venom of pit viper (Bothrops pauloensis), while that of L. malayensis was similar to the venom of snakes such as the Bothrops insularis and Bothrops asper. Kininogen-1 is a secreted protein, identified for the first time from the jellyfish L. malayensis. The proteome analysis of Cyanea nozakii, Chrysaora caliparea and Lychnorhiza malayensis contained 20, 12, 8 unique proteins, respectively. Our study characterized the proteome map of crude venom extract from L. malayensis and C. caliparea for the first time, and the venom profile is compared with published information elsewhere. Proteomic data from this study has been made available in the public domain.

Targeting age-specific changes in CD4+ T cell metabolism ameliorates alloimmune responses and prolongs graft survival

Age impacts alloimmunity. Effects of aging on T-cell metabolism and the potential to interfere with immunosuppressants have not been explored yet. Here, we dissected metabolic pathways of CD4⁺ and CD8⁺ T cells in aging and offer novel immunosuppressive targets. Upon activation, CD4⁺ T cells from old mice failed to exhibit adequate metabolic reprogramming resulting into compromised metabolic pathways, including oxidative phosphorylation (OXPHOS) and glycolysis. Comparable results were also observed in elderly human patients. Although glutaminolysis remained the dominant and age-independent source of mitochondria for activated CD4⁺ T cells, old but not young CD4⁺ T cells relied heavily on glutaminolysis. Treating young and old murine and human CD4⁺ T cells with 6-diazo-5-oxo-l-norleucine (DON), a glutaminolysis inhibitor resulted in significantly reduced IFN-γ production and compromised proliferative capacities specifically of old CD4⁺ T cells. Of translational relevance, old and young mice that had been transplanted with fully mismatched skin grafts and treated with DON demonstrated dampened Th1- and Th17-driven alloimmune responses. Moreover, DON diminished cytokine production and proliferation of old CD4⁺ T cells in vivo leading to a significantly prolonged allograft survival specifically in old recipients. Graft prolongation in young animals, in contrast, was only achieved when DON was applied in combination with an inhibition of glycolysis (2-deoxy-d-glucose, 2-DG) and OXPHOS (metformin), two alternative metabolic pathways. Notably, metabolic treatment had not been linked to toxicities. Remarkably, immunosuppressive capacities of DON were specific to CD4⁺ T cells as adoptively transferred young CD4⁺ T cells prevented immunosuppressive capacities of DON on allograft survival in old recipients. Depletion of CD8⁺ T cells did not alter transplant outcomes in either young or old recipients. Taken together, our data introduce an age-specific metabolic reprogramming of CD4⁺ T cells. Targeting those pathways offers novel and age-specific approaches for immunosuppression.

ORMDL3 and Asthma: Linking Sphingolipid Regulation to Altered T Cell Function

Orosomucoid like 3 (ORMDL3) encodes an ER-resident transmembrane protein that regulates the activity of serine palmitoyltransferase (SPT), the first and rate-limiting enzyme for sphingolipid biosynthesis in cells. A decade ago, several genome wide association studies revealed single nucleotide polymorphisms associated with increased ORMDL3 protein expression and susceptibility to allergic asthma. Since that time, numerous studies have investigated how altered ORMDL3 expression might predispose to asthma and other autoimmune/inflammatory diseases. In this brief review, we focus on growing evidence suggesting that heightened ORMDL3 expression specifically in CD4⁺ T lymphocytes, the central orchestrators of adaptive immunity, constitutes a major underlying mechanism of asthma pathogenesis by skewing their differentiation and function. Furthermore, we explore how sphingolipid modulation in T cells might be responsible for these effects, and how further studies may interrogate this intriguing hypothesis.

Use of bioinformatic analyses in identifying characteristic genes and mechanisms active in the progression of idiopathic thrombocytopenic purpura in individuals with different phenotypes

OBJECTIVE

To explore the mechanism underlying the progression of newly diagnosed idiopathic thrombocytopenic purpura (ITP) to its chronic or remission state using bioinformatic methods.

METHODS

GSE56232 and GSE46922 gene expression profile datasets were downloaded from Gene Expression Omnibus (GEO). Differentially expressed genes were identified and characteristic genes were screened by weighted gene co-expression network analysis. These genes were used for function enrichment analysis and construction of a protein-protein interaction network. Finally, characteristic genes were verified to determine potential molecular mechanisms underlying ITP progression.

RESULTS

We found that characteristic genes in the chronic ITP group were mainly involved in intracellular processes and ion binding, while characteristic genes in the remission ITP group were involved in intracellular processes and nuclear physiological activities. We identified a sub-network of characteristic genes, LMNA, JUN, PRKACG, SMC3, which may indicate the mechanism by which newly diagnosed ITP progresses to chronic. Although no meaningful signaling pathways were found, the expression of NR3C1, TPR, SMC4, PANBP2, CHD1, and U2SURP may affect ITP progression from newly diagnosed to remission.

CONCLUSION

Our findings improve the understanding of the pathogenesis and progression of ITP, and may provide new directions for the development of treatment strategies.

General Aspects of Metal Ions as Signaling Agents in Health and Disease

This review focuses on the current knowledge on the involvement of metal ions in signaling processes within the cell, in both physiological and pathological conditions. The first section is devoted to the recent discoveries on magnesium and calcium-dependent signal transduction-the most recognized signaling agents among metals. The following sections then describe signaling pathways where zinc, copper, and iron play a key role. There are many systems in which changes in intra- and extra-cellular zinc and copper concentrations have been linked to important downstream events, especially in nervous signal transduction. Iron signaling is mostly related with its homeostasis. However, it is also involved in a recently discovered type of programmed cell death, ferroptosis. The important differences in metal ion signaling, and its disease-leading alterations, are also discussed.

Calcium regulation of T cell metabolism

T cells are an essential component of the immune system that provide antigen-specific acute and long lasting immune responses to infections and tumors, ascertain the maintenance of immunological tolerance and, on the flipside, mediate autoimmunity in a variety of diseases. The activation of T cells through antigen recognition by the T cell receptor (TCR) results in transient and sustained Ca2+ signals that are shaped by the opening of Ca2+ channels in the plasma membrane and cellular organelles. The dynamic regulation of intracellular Ca2+ concentrations controls a variety of T cell functions on the timescale of seconds to days after signal initiation. Among the more recently identified roles of Ca2+ signaling in T cells is the regulation of metabolic pathways that control the function of many T cell subsets. In this review, we discuss how Ca2+ regulates several metabolic programs in T cells such as the activation of AMPK and the PI3K-AKT-mTORC1 pathway, aerobic glycolysis, mitochondrial metabolism including tricarboxylic acid (TCA) cycle function and oxidative phosphorylation (OXPHOS), as well as lipid metabolism.

Bcl-2-Protein Family as Modulators of IP3 Receptors and Other Organellar Ca2+ Channels

The pro- and antiapoptotic proteins belonging to the B-cell lymphoma-2 (Bcl-2) family exert a critical control over cell-death processes by enabling or counteracting mitochondrial outer membrane permeabilization. Beyond this mitochondrial function, several Bcl-2 family members have emerged as critical modulators of intracellular Ca²⁺ homeostasis and dynamics, showing proapoptotic and antiapoptotic functions. Bcl-2 family proteins specifically target several intracellular Ca²⁺-transport systems, including organellar Ca²⁺ channels: inositol 1,4,5-trisphosphate receptors (IP₃Rs) and ryanodine receptors (RyRs), Ca²⁺-release channels mediating Ca²⁺ flux from the endoplasmic reticulum, as well as voltage-dependent anion channels (VDACs), which mediate Ca²⁺ flux across the mitochondrial outer membrane into the mitochondria. Although the formation of protein complexes between Bcl-2 proteins and these channels has been extensively studied, a major advance during recent years has been elucidating the complex interaction of Bcl-2 proteins with IP₃Rs. Distinct interaction sites for different Bcl-2 family members were identified in the primary structure of IP₃Rs. The unique molecular profiles of these Bcl-2 proteins may account for their distinct functional outcomes when bound to IP₃Rs. Furthermore, Bcl-2 inhibitors used in cancer therapy may affect IP₃R function as part of their proapoptotic effect and/or as an adverse effect in healthy cells.

High-Dose Vitamin D-Mediated Hypercalcemia as a Potential Risk Factor in Central Nervous System Demyelinating Disease

The exact cause of multiple sclerosis (MS) is unknown; however, it is considered to be an inflammatory disease of the central nervous system (CNS) triggered by a combination of both environmental and genetic factors. Vitamin D deficiency is also discussed as a possible disease-promoting factor in MS, as low vitamin D status is associated with increased formation of CNS lesions, elevated number of relapses and accelerated disease progression. However, it remains unclear whether this association is causal and related and most importantly, whether vitamin D supplementation in MS is of direct therapeutic benefit. Recently, we could show that in a murine model of MS, administration of a moderate vitamin D dose was of clinical benefit, while excessive vitamin D supplementation had a negative effect on disease severity. Of note, disease exacerbation was associated with high-dose vitamin D caused secondary hypercalcemia. Mechanistically dissecting this outcome, we found that hypercalcemia independent of vitamin D similarly triggered activation of disease-perpetuating T cells. These findings caution that vitamin D should be supplemented in a controlled and moderate manner in patients with MS and concomitantly highlight calcium as a novel potential MS risk factor by itself. In this review, we will summarize the current evidence from animal and clinical studies aiming to assess whether vitamin D may be of benefit in patients with MS. Furthermore, we will discuss any possible secondary effects of vitamin D with a particular focus on the role of calcium on immune cells and in the pathogenesis of CNS demyelinating disease.

What's Bred in the Bone: Calcium Channels in Lymphocytes

Calcium (Ca²⁺) is an important second messenger in lymphocytes and is essential in regulating various intracellular pathways that control critical cell functions. Ca²⁺ channels are located in the plasma membrane and intracellular membranes, facilitating Ca²⁺ entry into the cytoplasm. Upon Ag receptor stimulation, Ca²⁺ can enter the lymphocyte via the Ca²⁺ release-activated Ca²⁺ channel found in the plasma membrane. The increase of cytosolic Ca²⁺ modulates signaling pathways, resulting in the transcription of target genes implicated in differentiation, activation, proliferation, survival, and apoptosis of lymphocytes. Along with Ca²⁺ release-activated Ca²⁺ channels, several other channels have been found in the membranes of T and B lymphocytes contributing to key cellular events. Among them are the transient receptor potential channels, the P2X receptors, voltage-dependent Ca²⁺ channels, and the inositol 1,4,5-trisphosphate receptor as well as the N-methyl-d-aspartate receptors. In this article, we review the contributions of these channels to mediating Ca²⁺ currents that drive specific lymphocyte functions.

Total and ionized calcium and magnesium are significantly lowered in drug-naïve depressed patients: effects of antidepressants and associations with immune activation

Major depressive disorder (MDD) is associated with alterations in calcium (Ca) and magnesium (Mg), as well as circulating pro- and anti-inflammatory cytokines. Anti-inflammatory drugs are commonly used as adjuvant treatments for MDD. However, no studies examined the effects of a combinatorial treatment with sertraline and ketoprofen, an anti-inflammatory drug, on Ca and Mg levels in MDD. The present study examined a) differences in both cations between drug-naïve MDD patients and controls, and b) the effects of sertraline and ketoprofen on Ca and Mg (both total and ionized). In the same patients, we also examined the associations between both cations and IL-1β, IL-4, IL-6, IL-18, IFN-γ, TGF-β1, zinc, and indoleamine 2,3-dioxygenase (IDO). Clinical improvement was assessed using the Beck Depression Inventory-II (BDI-II) at baseline and after follow up for 2 months. Serum Ca and Mg (total and ionized) were significantly lower in MDD patients as compared with controls, while treatment significantly increased calcium but decreased magnesium levels. There were significant and inverse correlations between the BDI-II scores from baseline to endpoint and Ca (both total and ionized), but not Mg, levels. The effects of calcium on the BDI-II score remained significant after considering the effects of zinc, IDO and an immune activation z unit-weighted composite score based on the sum of all cytokines. There was a significant and inverse association between this immune activation index and calcium levels from baseline to endpoint. In conclusion, lowered levels of both cations play a role in the pathophysiology of major depression. Antidepressant-induced increases in Ca are associated with clinical efficacy and attenuation of the immune response. The suppressant effect of antidepressants on Mg levels is probably a side effect of those drugs. New antidepressant treatments should be developed that increase the levels both Ca and Mg. Graphical abstract.

Metabolic reprogramming in memory CD4 T cell responses of old adults

To determine whether aging affects the ability of T cells to undergo metabolic reprogramming upon activation, we compared CD4 T cell responses after polyclonal in vitro stimulation. Compared to younger adults, CD4 memory T cells from healthy older individuals exhibited a higher upregulation of oxidative phosphorylation with increased production of reactive oxygen species and intracellular and secreted ATP. Increased ATP secretion led to increased purinergic signaling and P2X7-dependent increases in cytoplasmic calcium. The increased mitochondrial activity was not due to a difference in activation-induced mitochondrial biogenesis. Expression of carnitine palmitoyl transferase 1 was higher, conversely that of fatty acid synthase was reduced in older T cells, resulting in increased fatty acid oxidation, while depleting intracellular lipid stores. The aged CD4 memory T cells therefore maintain a more catabolic state in lipid metabolism, while their ability to upregulate glycolysis upon activation is preserved.

Creating a New Cancer Therapeutic Agent by Targeting the Interaction between Bcl-2 and IP3 Receptors

Bcl-2 is a member of a family of proteins that regulate cell survival. Expression of Bcl-2 is aberrantly elevated in many types of cancer. Within cells of the immune system, Bcl-2 has a physiological role in regulating immune responses. However, in cancers arising from cells of the immune system Bcl-2 promotes cell survival and proliferation. This review summarizes discoveries over the past 30 years that have elucidated Bcl-2's role in the normal immune system, including its actions in regulating calcium (Ca²⁺) signals necessary for the immune response, and for Ca²⁺-mediated apoptosis at the end of an immune response. How Bcl-2 modulates the release of Ca²⁺ from intracellular stores via inositol 1,4,5-trisphosphate receptors (IP₃R) is discussed, and in particular, the role of Bcl-2/IP₃R interactions in promoting the survival of cancer cells by preventing Ca²⁺-mediated cell death. The development and usage of a peptide, referred to as TAT-Pep8, or more recently, BIRD-2, that induces death of cancer cells by inhibiting Bcl-2's control over IP₃R-mediated Ca²⁺ elevation is discussed. Studies aimed at discovering a small molecule that mimics BIRD-2's anticancer mechanism of action are summarized, along with the prospect of such a compound becoming a novel therapeutic option for cancer.

Role of the Ca2+-Calcineurin-Nuclear Factor of Activated T cell Pathway in Mitofusin-2-Mediated Immune Function of Jurkat Cells

Background:

Mitofusin-2 (MFN2), a well-known mitochondrial fusion protein, has been shown to participate in innate immunity, but its role in mediating adaptive immunity remains poorly characterized. In this study, we explored the potential role of MFN2 in mediating the immune function of T lymphocytes.

Methods:

We manipulated MFN2 gene expression in Jurkat cells via lentiviral transduction of MFN2 small interfering RNA (siRNA) or full-length MFN2. After transduction, the immune response and its underlying mechanism were determined in Jurkat cells. One-way analysis of variance and Student's t-test were performed to determine the statistical significance between the groups.

Results:

Overexpression of MFN2 enhanced the immune response of T lymphocytes by upregulating Ca²⁺ (359.280 ± 10.130 vs. 266.940 ± 10.170, P = 0.000), calcineurin (0.513 ± 0.014 vs. 0.403 ± 0.020 nmol/L, P = 0.024), and nuclear factor of activated T cells (NFATs) activation (1.040 ± 0.086 vs. 0.700 ± 0.115, P = 0.005), whereas depletion of MFN2 impaired the immune function of T lymphocytes by downregulating Ca²⁺ (141.140 ± 14.670 vs. 267.060 ± 9.230, P = 0.000), calcineurin (0.054 ± 0.030 nmol/L vs. 0.404 ± 0.063 nmol/L, P = 0.000), and NFAT activation (0.500 ± 0.025 vs. 0.720 ± 0.061, P = 0.012). Furthermore, upregulated calcineurin partially reversed the negative effects of MFN2 siRNA on T cell-mediated immunity evidenced by elevations in T cell proliferation (1.120 ± 0.048 vs. 0.580 ± 0.078, P = 0.040), interleukin-2 (IL-2) production (473.300 ± 24.100 vs. 175.330 ± 12.900 pg/ml, P = 0.000), and the interferon-γ/IL-4 ratio (3.080 ± 0.156 vs. 0.953 ± 0.093, P = 0.000). Meanwhile, calcineurin activity inhibitor depleted the positive effects of overexpressed MFN2 on T cells function.

Conclusions:

Our findings suggest that MFN2 may regulate T cell immune functions primarily through the Ca²⁺-calcineurin-NFAT pathway. MFN2 may represent a potential therapeutic target for T cell immune dysfunction-related diseases.

TCR and CD28 Concomitant Stimulation Elicits a Distinctive Calcium Response in Naive T Cells

T cell activation is initiated upon ligand engagement of the T cell receptor (TCR) and costimulatory receptors. The CD28 molecule acts as a major costimulatory receptor in promoting full activation of naive T cells. However, despite extensive studies, why naive T cell activation requires concurrent stimulation of both the TCR and costimulatory receptors remains poorly understood. Here, we explore this issue by analyzing calcium response as a key early signaling event to elicit T cell activation. Experiments using mouse naive CD4⁺ T cells showed that engagement of the TCR or CD28 with the respective cognate ligand was able to trigger a rise in fluctuating calcium mobilization levels, as shown by the frequency and average response magnitude of the reacting cells compared with basal levels occurred in unstimulated cells. The engagement of both TCR and CD28 enabled a further increase of these two metrics. However, such increases did not sufficiently explain the importance of the CD28 pathways to the functionally relevant calcium responses in T cell activation. Through the autocorrelation analysis of calcium time series data, we found that combined but not separate TCR and CD28 stimulation significantly prolonged the average decay time (τ) of the calcium signal amplitudes determined with the autocorrelation function, compared with its value in unstimulated cells. This increasement of decay time (τ) uniquely characterizes the fluctuating calcium response triggered by concurrent stimulation of TCR and CD28, as it could not be achieved with either stronger TCR stimuli or by co-engaging both TCR and LFA-1, and likely represents an important feature of competent early signaling to provoke efficient T cell activation. Our work has thus provided new insights into the interplay between the TCR and CD28 early signaling pathways critical to trigger naive T cell activation.

Functional Analysis of an Inducible Promoter Driven by Activation Signals from a Chimeric Antigen Receptor

Adoptive transfer of T cells expressing a chimeric antigen receptor (CAR) is a promising cell-based anticancer therapy. Although clinical studies of this approach show therapeutic efficacy, additional genetic modification is necessary to enhance the efficacy and safety of CAR-T cells. For example, production of an antitumor cytokine from CAR-T cells can potentially enhance their tumor-killing activity, but there are concerns that constitutive expression of anticancer molecules will cause systemic side effects. Therefore, it is important that exogenous gene expression is confined to the tumor locality. Here, we aimed to develop an inducible promoter driven by activation signals from a CAR. Transgene expression in T cells transduced with the CD19-targeted CAR and an inducible promoter, including inducible reporter genes (CAR-T/iReporter), was only induced strongly by co-culture with CD19-positive target cells. CAR-T/iReporter cells also showed redirected cytolysis toward CD19-positive, but not CD19-negative, tumor cells. Overall, our study indicated that the inducible promoter was selectively driven by activation signals from the CAR, and transduction with the inducible promoter did not affect original effector activities including interleukin-2 and interferon-γ production and the antitumor activity of CAR-redirected cytotoxic T lymphocytes. Moreover, this inducible promoter permits visualization and quantification of the activation status in CAR-T cells.

Intramembrane ionic protein-lipid interaction regulates integrin structure and function

Protein transmembrane domains (TMDs) are generally hydrophobic, but our bioinformatics analysis shows that many TMDs contain basic residues at terminal regions. Physiological functions of these membrane-snorkeling basic residues are largely unclear. Here, we show that a membrane-snorkeling Lys residue in integrin αLβ2 (also known as lymphocyte function-associated antigen 1 [LFA-1]) regulates transmembrane heterodimer formation and integrin adhesion through ionic interplay with acidic phospholipids and calcium ions (Ca²⁺) in T cells. The amino group of the conserved Lys ionically interacts with the phosphate group of acidic phospholipids to stabilize αLβ2 transmembrane association, thus keeping the integrin at low-affinity conformation. Intracellular Ca²⁺ uses its charge to directly disrupt this ionic interaction, leading to the transmembrane separation and the subsequent extracellular domain extension to increase adhesion activity. This Ca²⁺-mediated regulation is independent on the canonical Ca²⁺ signaling or integrin inside-out signaling. Our work therefore showcases the importance of intramembrane ionic protein–lipid interaction and provides a new mechanism of integrin activation.

Integrin αLβ2 is the major integrin in T cells and plays a vital role in regulating T-cell activation, adhesion, and migration. The transmembrane association of αL and β2 is crucial for maintaining the integrin at low-affinity conformation. Here, we find that the conserved basic residue (K702) in the transmembrane domain of β2 contributes to transmembrane association through ternary ionic interaction with acidic phospholipid and αL cytoplasmic residue. Upon T-cell activation, influxed calcium ions (Ca²⁺) can directly disrupt the ionic K702–lipid interaction through its positive charges, which leads to transmembrane separation and subsequent extracellular domain extension to switch αLβ2 to high-affinity conformation. This Ca²⁺-mediated regulation is through the modulation of the ionic Lys–lipid interaction but not through the canonical Ca²⁺ signaling or integrin inside-out signaling. Our study thus reports a new regulatory mechanism of integrin activation and showcases the importance of intramembrane ionic protein–lipid interaction. This finding might have general relevance, as bioinformatics analysis shows the presence of membrane-snorkeling basic residue is a common feature of transmembrane proteins.

Adhesive Interactions Delineate the Topography of the Immune Synapse

T cells form adhesive contacts with antigen-presenting cells (APCs) as part of the normal surveillance process that occurs in lymph nodes and other tissues. Most of these adhesive interactions are formed by integrins that interact with ligands expressed on the surface of the APC. The interactive strength of integrins depends on their degree of membrane proximity as well as intracellular signals that dictate the conformation of the integrin. Integrins appear in different conformations that endow them with different affinities for their ligand(s). Integrin conformation and thus adhesive strength between the T cell and the APC is tuned by intracellular signals that are turned on by ligation of the T cell receptor (TCR) and chemokine receptors. During the different stages of the process, integrins, the TCR and chemokine receptors may be interconnected by the actin cytoskeleton underneath the plasma membrane, forming a chemical and physical network that facilitates the spatiotemporal dynamics, positioning, and function of these receptors and supports cell-cell adhesion during T cell activation, allowing it to perform its effector function.

TRPC1 expression and function inhibit ER stress and cell death in salivary gland cells

Disturbances in endoplasmic reticulum (ER) Ca2+ homeostasis have been associated with many diseases including loss of salivary glands. Although significant progress has been accomplished which led to the increase in our understanding of the cellular responses to ER stress, the factors/ion channels that could inhibit ER stress are not yet identified. Here we show that TRPC1 (transient receptor potential canonical 1) is involved in regulating Ca2+ homeostasis and loss of TRPC1 decreased ER Ca2+ levels, inhibited the unfolded protein response (UPR), that induced loss of salivary gland cells. We provide further evidence that ER stress inducing agents (Tunicamycin and Brefeldin A) disrupts Ca2+ homeostasis by directly inhibiting TRPC1-mediated Ca2+ entry, which led to ER stress in salivary gland cells. Moreover, induction of ER stress lead to an increase in CHOP expression, which decreased TRPC1 expression and subsequently attenuated autophagy along with increased apoptosis. Importantly, TRPC1-/- mice showed increased ER stress, increased immune cell infiltration, loss of Ca2+ homeostasis, decreased saliva secretion, and decreased salivary gland survival. Finally, restoration of TRPC1 not only maintained Ca2+ homeostasis, but inhibited ER stress that induced cell survival. Overall these results suggest a significant role of TRPC1 Ca2+ channels in ER stress and homeostatic function/survival of salivary gland cells.

Thapsigargin Increases IL-2 Production in T Cells at Nanomolar Concentrations

Thapsigargin (TGN) is a potent and selective inhibitor of sarco-endoplasmic Ca²⁺-ATPase, leading to rapid elevation of cytoplasmic Ca²⁺ concentration. Previous reports have shown that TGN increases the production of various cytokines from macrophages and dendritic cells. Here, we examine the effects of TGN on murine T cells. Nanomolar concentrations of TGN are a significant inducer of IL-2 production with full activity at 50 nM. Micromolar concentrations of TGN, however, are inhibitory to IL-2 production and T cell proliferation. The IL-2 production-inducing activity of TGN is much more prominent when T cells are primed with concanavalin A or anti-CD3 mAb, and is due to the increase of cytoplasmic Ca²⁺ concentration. TGN at 50 nM does not affect interferon-gamma or IL-4 production from T cells. Thus, the present study shows that low nanomolar concentrations of TGN could be useful in potentiating IL-2 production from antigen-primed T cells.

Targeting Bcl-2-IP3 receptor interaction to treat cancer: A novel approach inspired by nearly a century treating cancer with adrenal corticosteroid hormones

Bcl-2 inhibits cell death by at least two different mechanisms. On the one hand, its BH3 domain binds to pro-apoptotic proteins such as Bim and prevents apoptosis induction. On the other hand, the BH4 domain of Bcl-2 binds to the inositol 1,4,5-trisphosphate receptor (IP₃R), preventing Ca²⁺ signals that mediate cell death. In normal T-cells, Bcl-2 levels increase during the immune response, protecting against cell death, and then decline as apoptosis ensues and the immune response dissipates. But in many cancers Bcl-2 is aberrantly expressed and exploited to prevent cell death by inhibiting IP₃R-mediated Ca²⁺ elevation. This review summarizes what is known about the mechanism of Bcl-2's control over IP₃R-mediated Ca²⁺ release and cell death induction. Early insights into the role of Ca²⁺ elevation in corticosteroid-mediated cell death serves as a model for how targeting IP₃R-mediated Ca²⁺ elevation can be a highly effective therapeutic approach for different types of cancer. Moreover, the successful development of ABT-199 (Venetoclax), a small molecule targeting the BH3 domain of Bcl-2 but without effects on Ca²⁺, serves as proof of principle that targeting Bcl-2 can be an effective therapeutic approach. BIRD-2, a synthetic peptide that inhibits Bcl-2-IP₃R interaction, induces cell death induction in ABT-199 (Venetoclax)-resistant cancer models, attesting to the value of developing therapeutic agents that selectively target Bcl-2-IP₃R interaction, inducing Ca²⁺-mediated cell death.

Diverse Roles of Mitochondria in Immune Responses: Novel Insights Into Immuno-Metabolism

Lack of immune system cells or impairment in differentiation of immune cells is the basis for many chronic diseases. Metabolic changes could be the root cause for this immune cell impairment. These changes could be a result of altered transcription, cytokine production from surrounding cells, and changes in metabolic pathways. Immunity and mitochondria are interlinked with each other. An important feature of mitochondria is it can regulate activation, differentiation, and survival of immune cells. In addition, it can also release signals such as mitochondrial DNA (mtDNA) and mitochondrial ROS (mtROS) to regulate transcription of immune cells. From current literature, we found that mitochondria can regulate immunity in different ways. First, alterations in metabolic pathways (TCA cycle, oxidative phosphorylation, and FAO) and mitochondria induced transcriptional changes can lead to entirely different outcomes in immune cells. For example, M1 macrophages exhibit a broken TCA cycle and have a pro-inflammatory role. By contrast, M2 macrophages undergo β-oxidation to produce anti-inflammatory responses. In addition, amino acid metabolism, especially arginine, glutamine, serine, glycine, and tryptophan, is critical for T cell differentiation and macrophage polarization. Second, mitochondria can activate the inflammatory response. For instance, mitochondrial antiviral signaling and NLRP3 can be activated by mitochondria. Third, mitochondrial mass and mobility can be influenced by fission and fusion. Fission and fusion can influence immune functions. Finally, mitochondria are placed near the endoplasmic reticulum (ER) in immune cells. Therefore, mitochondria and ER junction signaling can also influence immune cell metabolism. Mitochondrial machinery such as metabolic pathways, amino acid metabolism, antioxidant systems, mitochondrial dynamics, mtDNA, mitophagy, and mtROS are crucial for immune functions. Here, we have demonstrated how mitochondria coordinate to alter immune responses and how changes in mitochondrial machinery contribute to alterations in immune responses. A better understanding of the molecular components of mitochondria is necessary. This can help in the development of safe and effective immune therapy or prevention of chronic diseases. In this review, we have presented an updated prospective of the mitochondrial machinery that drives various immune responses.

T Cell Calcium Signaling Regulation by the Co-Receptor CD5

Calcium influx is critical for T cell effector function and fate. T cells are activated when T cell receptors (TCRs) engage peptides presented by antigen-presenting cells (APC), causing an increase of intracellular calcium (Ca2+) concentration. Co-receptors stabilize interactions between the TCR and its ligand, the peptide-major histocompatibility complex (pMHC), and enhance Ca2+ signaling and T cell activation. Conversely, some co-receptors can dampen Ca2+ signaling and inhibit T cell activation. Immune checkpoint therapies block inhibitory co-receptors, such as cytotoxic T-lymphocyte associated antigen 4 (CTLA-4) and programmed death 1 (PD-1), to increase T cell Ca2+ signaling and promote T cell survival. Similar to CTLA-4 and PD-1, the co-receptor CD5 has been known to act as a negative regulator of T cell activation and to alter Ca2+ signaling and T cell function. Though much is known about the role of CD5 in B cells, recent research has expanded our understanding of CD5 function in T cells. Here we review these recent findings and discuss how our improved understanding of CD5 Ca2+ signaling regulation could be useful for basic and clinical research.

Repurposing ospemifene for potentiating an antigen-specific immune response

OBJECTIVE

Ospemifene, an estrogen receptor agonist/antagonist approved for the treatment of dyspareunia and vaginal dryness in postmenopausal women, has potential new indications as an immune modulator. The overall objective of the present series of preclinical studies was to evaluate the immunomodulatory activity of ospemifene in combination with a peptide cancer vaccine.

METHODS

Immune regulating effects, mechanism of action and structure activity relationships of ospemifene and related compounds were evaluated by examining expression of T-cell activating cytokines in vitro, and antigen-specific immune response and cytotoxic T-lymphocyte activity in vivo. The effects of ospemifene (OSP) on the immune response to a peptide cancer vaccine (PV) were evaluated after chronic [control (n = 22); OSP 50 mg/kg (n = 16); PV (n = 6); OSP+PV (n = 11)], intermittent [control (n = 10); OSP 10 and 50 mg/kg (n = 11); PV (n = 11); combination treatment (n = 11 each dose)] and pretreatment [control; OSP 100 mg/kg; PV 100 μg; combination treatment (n = 8 all groups)] ospemifene oral dosing schedules in a total of 317 mixed-sex tumor-bearing and nontumor-bearing mice.

RESULTS

The results showed that ospemifene induced expression of the key TH1 cytokines interferon gamma and interleukin-2 in vitro, which may be mediated by stimulating T-cells through phosphoinositide 3-kinase and calmodulin signaling pathways. In combination with an antigen-specific peptide cancer vaccine, ospemifene increased antigen-specific immune response and increased cytotoxic T-lymphocyte activity in tumor-bearing and nontumor-bearing mice. The pretreatment, intermittent, and chronic dosing schedules of ospemifene activate naive T-cells, modulate antigen-induced tolerance and reduce tumor-associated, pro-inflammatory cytokines, respectively.

CONCLUSIONS

Taken together, ospemifene's dose response and schedule-dependent immune modulating activity offers a method of tailoring and augmenting the efficacy of previously failed antigen-specific cancer vaccines for a wide range of malignancies.

Mitochondrial Proteins Coded by Human Tumor Viruses

Viruses must exploit the cellular biosynthetic machinery and evade cellular defense systems to complete their life cycles. Due to their crucial roles in cellular bioenergetics, apoptosis, innate immunity and redox balance, mitochondria are important functional targets of many viruses, including tumor viruses. The present review describes the interactions between mitochondria and proteins coded by the human tumor viruses human T-cell leukemia virus type 1, Epstein-Barr virus, Kaposi's sarcoma-associated herpesvirus, human hepatitis viruses B and C, and human papillomavirus, and highlights how these interactions contribute to viral replication, persistence and transformation.