Regulation of T cell survival through coronin-1-mediated generation of inositol-1,4,5-trisphosphate and calcium mobilization after T cell receptor triggering

Coronin 1a-mediated F-actin disassembly controls effector function in murine neutrophils

The double-edged role of neutrophils in effective host defense and harmful pathology is an emerging topic in clinical research. Neutrophils release highly potent antimicrobial granule compounds and reactive oxygen species (ROS) that can also be detrimental to the host and promote inflammatory diseases and cancer. Here we show that disassembly of F-actin greatly facilitates ROS production and degranulation in neutrophils. Utilizing neutrophils from Coronin 1a (Coro1a)-deficient mice, our data reveal that the actin-regulatory protein Coro1a controls this spatial F-actin deconstruction and concomitantly forms a signaling complex with Rac-GTPases, thereby promoting activation and translocation of Rac to the membrane during neutrophil activation. This functional activity of Coro1a was critical for neutrophil granule exocytosis and the activation of the NADPH oxidase complex. Consistent with these findings, impaired ROS production in Coro1a-deficient neutrophils was rescued by pharmacological promotion of actin depolymerization or activation of Rac. Together, our findings suggest that the Coro1a/Rac signaling hub acts as a central regulatory element that coordinates actin cytoskeletal reorganization required for the execution of neutrophil effector functions. Since Coro1a is highly conserved between mice and humans and associated with human immunodeficiency, our results are also relevant for human biomedical studies.

T cell population size control by coronin 1 uncovered: from a spot identified by two-dimensional gel electrophoresis to quantitative proteomics

INTRODUCTION

Recent work identified members of the evolutionarily conserved coronin protein family as key regulators of cell population size. This work originated ~25 years ago through the identification, by two-dimensional gel electrophoresis, of coronin 1 as a host protein involved in the virulence of Mycobacterium tuberculosis. We here describe the journey from a spot on a 2D gel to the recent realization that coronin proteins represent key controllers of eukaryotic cell population sizes, using ever more sophisticated proteomic techniques.

AREAS COVERED

We discuss the value of 'old school' proteomics using relatively simple and cost-effective technologies that allowed to gain insights into subcellular proteomes and describe how label-free quantitative (phospho)proteomics using mass spectrometry allowed to disentangle the role for coronin 1 in eukaryotic cell population size control. Finally, we mention potential implications of coronin-mediated cell population size control for health and disease.

EXPERT OPINION

Proteome analysis has been revolutionized by the advent of modern-day mass spectrometers and is indispensable for a better understanding of biology. Here, we discuss how careful dissection of physio-pathological processes by a combination of proteomics, genomics, biochemistry and cell biology may allow to zoom in on the unexplored, thereby possibly tackling hitherto unasked questions and defining novel mechanisms.

Coronin 1-dependent cell density sensing and regulation of the peripheral T cell population size

The establishment and maintenance of peripheral T cells is important to ensure appropriate immunity. In mammals, T cells are produced in the thymus before seeding the periphery early in life, and thereafter progressive thymus involution impairs new T cell production. Yet, peripheral T cells are maintained lifelong at approximately similar cell numbers. The question thus arises: what are the mechanisms that enable the maintenance of the appropriate number of circulating T cells, ensuring that T cell numbers are neither too low nor too high? Here, we highlight recent research suggesting a key role for coronin 1, a member of the evolutionarily conserved family of coronin proteins, in both allowing T cells to reach as well as maintain their appropriate cell population size. This cell population size controlling pathway was found to be conserved in amoeba, mice and human. We propose that coronin 1 is an integral part of a cell-intrinsic pathway that couples cell density information with prosurvival signalling thereby regulating the appropriate number of peripheral T cells.

Novel hemizygous CORO1A variant leads to combined immunodeficiency with defective platelet calcium signaling and cell mobility

Background

To date, fewer than 20 patients have been identified as having germline biallelic mutations in the coronin-1A gene (CORO1A) and its protein with clinical features of combined immunodeficiency characterized by T-cell lymphopenia ranging from the severe phenotype to the mild phenotype, recurrent infections, and lymphoproliferative disorders. However, the effects of CORO1A protein disruption on actin-dependent functions in primary cells have not been fully delineated.

Objective

We sought to characterize the underlying defects of actin-dependent cellular functions in a female patient with combined immunodeficiency caused by a novel missense variant in the CORO1A gene in combination with a de novo heterozygous microdeletion of chromosome 16p11.2 and also to provide evidence of the pathogenicity of this gene mutation.

Methods

To identify the genetic defect, next-generation sequencing followed by Sanger confirmation and array comparative genomic hybridization were performed. Western blot and quantitative PCR tests were used to assess the effects on the protein. Flow cytometry and live microscopy were performed to investigate cellular motility and immune cell counts and function.

Results

We demonstrated that the CORO1A hemizygous variant c.19C>T, p. A7C induces significant decreases in cellular levels of the CORO1A protein while leaving mRNA concentrations unaffected. The observed mutation resulted in impaired natural killer cell cytotoxicity and platelet calcium signaling. In addition, primary granulocytes and mesenchymal cells showed significant defects in motility.

Conclusion

Collectively, we added new data about the CORO1A gene as a key player in actin cytoskeleton dynamics and cell signaling. Our findings expand the clinical spectrum regarding CORO1A protein deficiency and confirm the importance of a personalized therapeutic approach for each patient.

Changes of the salivary and serum proteome in canine hypothyroidism

In this study, changes in salivary and serum proteome of dogs with hypothyroidism were studied using tandem mass tags (TMT) labelling and liquid chromatography-mass spectrometry (LC-MS/MS). Saliva and serum proteome from 10 dogs with hypothyroidism were compared with 10 healthy dogs. In saliva, a total of seven proteins showed significant changes between the two groups, being six downregulated and one upregulated, meanwhile, in serum, a total of six proteins showed significant changes, being five downregulated and one upregulated. The altered proteins reflected metabolic and immunologic changes, as well as, skin and coagulation alterations, and these proteins were not affected by gender. One of the proteins that were downregulated in saliva, lactate dehydrognease (LDH), was measured by a spectrophotometric assay in saliva samples from 42 dogs with hypothyroidism, 42 dogs with non-thyroid diseases and 46 healthy dogs. The activity of LDH was lower in the saliva of hypothyroid dogs when compared to non-thyroid diseased dogs and healthy controls. This study indicates that canine hypothyroidism can produce changes in the proteome of saliva and serum. These two sample types showed different variations in their proteins reflecting physiopathological changes that occur in this disease, mainly related to the immune system, metabolism, skin and coagulation. In addition, some of the proteins identified in this study, specially LDH in saliva, should be further explored as potential biomarkers of canine hypothyroidism.

Evidence that fish death after Vibrio vulnificus infection is due to an acute inflammatory response triggered by a toxin of the MARTX family

Vibrio vulnificus is an emerging zoonotic pathogen associated with fish farms that is capable of causing a hemorrhagic septicemia known as warm-water vibriosis. According to a recent transcriptomic and functional study, the death of fish due to vibriosis is more related to the inflammatory response of the host than to the tissue lesions caused by the pathogen. In this work, we hypothesize that the RtxA1 toxin (a V. vulnificus toxin of the MARTX (Multifunctional Autoprocessing Repeats in Toxin) family) is the key virulence factor that would directly or indirectly trigger this fatal inflammatory response. Our hypothesis was based on previous studies that showed that rtxA1-deficient mutants maintained their ability to colonize and invade, but were unable to kill fish. To demonstrate this hypothesis, we infected eels (model of fish vibriosis) by immersion with a mutant deficient in RtxA1 production and analyzed their transcriptome in blood, red blood cells and white blood cells during early vibriosis (0, 3 and 12 h post-infection). The transcriptomic results were compared with those obtained in the previous study in which eels were infected with the V. vulnificus parental strain, and were functionally validated. Overall, our results confirm that fish death after V. vulnificus infection is due to an acute, early and atypical inflammatory response triggered by RtxA1 in which red blood cells seem to play a central role. These results could be relevant to other vibriosis as the toxins of this family are widespread in the Vibrio genus.

Wip1 inhibits neutrophil extracellular traps to promote abscess formation in mice by directly dephosphorylating Coronin-1a

Neutrophil extracellular traps (NETs) participate in the rapid inhibition and clearance of pathogens during infection; however, the molecular regulation of NET formation remains poorly understood. In the current study, we found that inhibition of the wild-type p53-induced phosphatase 1 (Wip1) significantly suppressed the activity of Staphylococcus aureus (S. aureus) and accelerated abscess healing in S. aureus-induced abscess model mice by enhancing NET formation. A Wip1 inhibitor significantly enhanced NET formation in mouse and human neutrophils in vitro. High-resolution mass spectrometry and biochemical assays demonstrated that Coro1a is a substrate of Wip1. Further experiments also revealed that Wip1 preferentially and directly interacts with phosphorylated Coro1a than compared to unphosphorylated inactivated Coro1a. The phosphorylated Ser426 site of Coro1a and the 28-90 aa domain of Wip1 are essential for the direct interaction of Coro1a and Wip1 and for Wip1 dephosphorylation of p-Coro1a Ser426. Wip1 deletion or inhibition in neutrophils significantly upregulated the phosphorylation of Coro1a-Ser426, which activated phospholipase C and subsequently the calcium pathway, the latter of which promoted NET formation after infection or lipopolysaccharide stimulation. This study revealed Coro1a to be a novel substrate of Wip1 and showed that Wip1 is a negative regulator of NET formation during infection. These results support the potential application of Wip1 inhibitors to treat bacterial infections.

The intrinsically disordered region of coronins fine-tunes oligomerization and actin polymerization

Coronins play critical roles in actin network formation. The diverse functions of coronins are regulated by the structured N-terminal β propeller and the C-terminal coiled coil (CC). However, less is known about a middle "unique region" (UR), which is an intrinsically disordered region (IDR). The UR/IDR is an evolutionarily conserved signature in the coronin family. By integrating biochemical and cell biology experiments, coarse-grained simulations, and protein engineering, we find that the IDR optimizes the biochemical activities of coronins in vivo and in vitro. The budding yeast coronin IDR plays essential roles in regulating Crn1 activity by fine-tuning CC oligomerization and maintaining Crn1 as a tetramer. The IDR-guided optimization of Crn1 oligomerization is critical for F-actin cross-linking and regulation of Arp2/3-mediated actin polymerization. The final oligomerization status and homogeneity of Crn1 are contributed by three examined factors: helix packing, the energy landscape of the CC, and the length and molecular grammar of the IDR.

An evolutionarily conserved coronin-dependent pathway defines cell population size

Maintenance of cell population size is fundamental to the proper functioning of multicellular organisms. Here, we describe a cell-intrinsic cell density–sensing pathway that enabled T cells to reach and maintain an appropriate population size. This pathway operated “kin-to-kin” or between identical or similar T cell populations occupying a niche within a tissue or organ, such as the lymph nodes, spleen, and blood. We showed that this pathway depended on the cell density–dependent abundance of the evolutionarily conserved protein coronin 1, which coordinated prosurvival signaling with the inhibition of cell death until the cell population reached threshold densities. At or above threshold densities, coronin 1 expression peaked and remained stable, thereby resulting in the initiation of apoptosis through kin-to-kin intercellular signaling to return the cell population to the appropriate cell density. This cell population size-controlling pathway was conserved from amoeba to humans, thus providing evidence for the existence of a coronin-regulated, evolutionarily conserved mechanism by which cells are informed of and coordinate their relative population size.

Identifying tumor immunity-associated molecular features in liver hepatocellular carcinoma by multi-omics analysis

Background: Although current immunotherapies have achieved some successes for hepatocellular carcinoma (HCC) patients, their benefits are limited for most HCC patients. Therefore, the identification of biomarkers for promoting immunotherapeutic responses in HCC is urgently needed.

Methods: Using the TCGA HCC cohort, we investigated correlations of various molecular features with antitumor immune signatures (CD8⁺ T cell infiltration and cytolytic activity) and an immunosuppressive signature (PD-L1 expression) in HCC. These molecular features included mRNAs, microRNAs (miRNAs), long non-coding RNAs (lncRNAs), proteins, and pathways.

Results: We found that the mutations of several oncogenes and tumor suppressor genes significantly correlated with reduced antitumor immune signatures, including TTN, CTNNB1, RB1, ZFHX4, and TP53. It indicates that these genes’ mutations may inhibit antitumor immune responses in HCC. Four proteins (Syk, Lck, STAT5, and Caspase-7) had significant positive expression correlations with CD8⁺ T cell enrichment, cytolytic activity, and PD-L1 expression in HCC. It suggests that these proteins’ expression could be useful biomarkers for the response to immune checkpoint inhibitors Similiarly, we identified other types of biomarkers potentially useful for predicting the response to ICIs, including miRNAs (hsa-miR-511-5p, 150-3p, 342-3p, 181a-3p, 625-5p, 4772-3p, 155-3p, 142-5p, 142-3p, 155-5p, 625-3p, 1976, 7702), many lncRNAs, and pathways (apoptosis, cytokine-cytokine receptor interaction, Jak-STAT signaling, MAPK signaling, PI3K-AKT signaling, HIF-1 signaling, ECM receptor interaction, focal adhesion, and estrogen signaling). Further, tumor mutation burden showed no significant correlation with antitumor immunity, while tumor aneuploidy levels showed a significant negative correlation with antitumor immunity.

Conclusion: The molecular features significantly associated with HCC immunity could be predictive biomarkers for immunotherapeutic responses in HCC patients. They could also be potential intervention targets for boosting antitumor immunity and immunotherapeutic responses in HCC.

The prognostic marker FLVCR2 associated with tumor progression and immune infiltration for acute myeloid leukemia

Acute myeloid leukemia (AML) is one of the most common hematopoietic malignancies in adults. The tumor microenvironment (TME) has a critical effect on AML occurrence, recurrence, and progression. The gene feline leukemia virus subgroup C cellular receptor family member 2 (FLVCR2) belongs to the major facilitator superfamily of transporter protein members, which is primarily involved in transporting small molecules. The potential role of FLVCR2 in the TME in AML has not been investigated. To clarify the expression and role of FLVCR2 in AML, we analyzed the Gene Expression Omnibus and The Cancer Genome Atlas databases and found that FLVCR2 mRNA expression significantly increased among patients with AML. Furthermore, based on an analysis of the Gene Expression Profiling Interactive Analysis database, FLVCR2 upregulation predicted dismal overall survival of patients with AML. Our validation analysis revealed the significant upregulation of FLVCR2 within the bone marrow of AML relative to healthy controls by western blotting and qPCR assays. Gene set enrichment analysis was conducted to explore FLVCR2's related mechanism in AML. We found that high FLVCR2 expression was related to infiltration degrees of immune cells and immune scores among AML cases, indicating that FLVCR2 possibly had a crucial effect on AML progression through the immune response. Specifically, FLVCR2 upregulation was negatively related to the immune infiltration degrees of activated natural killer cells, activated memory CD4+ T cells, activated dendritic cells, and CD8+ T cells using CIBERSORT analysis. According to the in vitro research, FLVCR2 silencing suppressed AML cell growth and promoted their apoptosis. This study provides insights into FLVCR2's effect on tumor immunity, indicating that it might serve as an independent prognostic biomarker and was related to immune infiltration within AML.

Activation and regulation of alloreactive T cell immunity in solid organ transplantation

Transplantation is the only curative treatment for patients with kidney failure but it poses unique immunological challenges that must be overcome to prevent allograft rejection and ensure long-term graft survival. Alloreactive T cells are important contributors to graft rejection, and a clearer understanding of the mechanisms by which these cells recognize donor antigens - through direct, indirect or semi-direct pathways - will facilitate their therapeutic targeting. Post-T cell priming rejection responses can also be modified by targeting pathways that regulate T cell trafficking, survival cytokines or innate immune activation. Moreover, the quantity and quality of donor-reactive memory T cells crucially shape alloimmune responses. Of note, many fundamental concepts in transplant immunology have been derived from models of infection. However, the programmed differentiation of allograft-specific T cell responses is probably distinct from that of pathogen-elicited responses, owing to the dearth of pathogen-derived innate immune activation in the transplantation setting. Understanding the fundamental (and potentially unique) immunological pathways that lead to allograft rejection is therefore a prerequisite for the rational development of therapeutics that promote transplantation tolerance.

Possible association of 16p11.2 copy number variation with altered lymphocyte and neutrophil counts

Recurrent copy-number variations (CNVs) at chromosome 16p11.2 are associated with neurodevelopmental diseases, skeletal system abnormalities, anemia, and genitourinary defects. Among the 40 protein-coding genes encompassed within the rearrangement, some have roles in leukocyte biology and immunodeficiency, like SPN and CORO1A. We therefore investigated leukocyte differential counts and disease in 16p11.2 CNV carriers. In our clinically-recruited cohort, we identified three deletion carriers from two families (out of 32 families assessed) with neutropenia and lymphopenia. They had no deleterious single-nucleotide or indel variant in known cytopenia genes, suggesting a possible causative role of the deletion. Noticeably, all three individuals had the lowest copy number of the human-specific BOLA2 duplicon (copy-number range: 3–8). Consistent with the lymphopenia and in contrast with the neutropenia associations, adult deletion carriers from UK biobank (n = 74) showed lower lymphocyte (Padj = 0.04) and increased neutrophil (Padj = 8.31e-05) counts. Mendelian randomization studies pinpointed to reduced CORO1A, KIF22, and BOLA2-SMG1P6 expressions being causative for the lower lymphocyte counts. In conclusion, our data suggest that 16p11.2 deletion, and possibly also the lowest dosage of the BOLA2 duplicon, are associated with low lymphocyte counts. There is a trend between 16p11.2 deletion with lower copy-number of the BOLA2 duplicon and higher susceptibility to moderate neutropenia. Higher numbers of cases are warranted to confirm the association with neutropenia and to resolve the involvement of the deletion coupled with deleterious variants in other genes and/or with the structure and copy number of segments in the CNV breakpoint regions.

Modulation of autoimmune diabetes by N-ethyl-N-nitrosourea- induced mutations in non-obese diabetic mice

Genetic association studies of type 1 diabetes (T1D) in humans, and in congenic non-obese diabetic (NOD) mice harboring DNA segments from T1D-resistant mice, face the challenge of assigning causation to specific gene variants among many within loci that affect disease risk. Here, we created random germline mutations in NOD/NckH mice and used automated meiotic mapping to identify mutations modifying T1D incidence and age of onset. In contrast with association studies in humans or congenic NOD mice, we analyzed a relatively small number of genetic changes in each pedigree, permitting implication of specific mutations as causative. Among 844 mice from 14 pedigrees bearing 594 coding/splicing changes, we identified seven mutations that accelerated T1D development, and five that delayed or suppressed T1D. Eleven mutations affected genes not previously known to influence T1D (Xpnpep1, Herc1, Srrm2, Rapgef1, Ppl, Zfp583, Aldh1l1, Col6a1, Ccdc13, Cd200r1, Atrnl1). A suppressor mutation in Coro1a validated the screen. Mutagenesis coupled with automated meiotic mapping can detect genes in which allelic variation influences T1D susceptibility in NOD mice. Variation of some of the orthologous/paralogous genes may influence T1D susceptibility in humans.

The Actin Regulators Involved in the Function and Related Diseases of Lymphocytes

Actin is an important cytoskeletal protein involved in signal transduction, cell structure and motility. Actin regulators include actin-monomer-binding proteins, Wiskott-Aldrich syndrome (WAS) family of proteins, nucleation proteins, actin filament polymerases and severing proteins. This group of proteins regulate the dynamic changes in actin assembly/disassembly, thus playing an important role in cell motility, intracellular transport, cell division and other basic cellular activities. Lymphocytes are important components of the human immune system, consisting of T-lymphocytes (T cells), B-lymphocytes (B cells) and natural killer cells (NK cells). Lymphocytes are indispensable for both innate and adaptive immunity and cannot function normally without various actin regulators. In this review, we first briefly introduce the structure and fundamental functions of a variety of well-known and newly discovered actin regulators, then we highlight the role of actin regulators in T cell, B cell and NK cell, and finally provide a landscape of various diseases associated with them. This review provides new directions in exploring actin regulators and promotes more precise and effective treatments for related diseases.

Coronin 1A facilitates calcium mobilization and promotes astrocyte reactivity in HIV-1 neuropathogenesis

Astrocyte reactivity, a phenomenon observed in a variety of neurodegenerative disorders, can have both beneficial and detrimental manifestations which significantly affect neuronal physiology. In neuroAIDS, reactive astrocytes have been observed to severely affect the neuronal population present in their vicinity. Calcium signaling plays a central role in mediating astrocyte reactivity. Coronin 1A, an actin-binding protein, majorly reported in hematopoietic cells, regulates cell activity in a calcium-dependent manner, but its role in astrocyte physiology and reactivity is largely unknown. Using a well-characterized primary culture of human astroglia and neurons, we explored the roles of coronin 1A in astrocyte physiology and its involvement in facilitating astrocyte reactivity. In this study, we report coronin 1A expression in human primary astrocytes and autopsy brain sections, and that it plays activity-dependent roles by facilitating calcium mobilization from the intracellular stores. HIV-1 Tat, a potent neurotoxicant that turns astrocytes reactive, augments coronin 1A expression, apart from affecting GFAP and pro-inflammatory molecules. Also, the autopsy brain tissue of HIV-1 infected individuals has a higher expression of coronin 1A. Downregulation of coronin 1A attenuated the HIV-1 Tat-induced deleterious effects of reactive astrocytes, measured as the upregulated expression of GFAP, pro-inflammatory molecules, and enhanced release of IL-6, and hence reduced astrocyte-mediated neurodegeneration. Our findings also suggest that out of a pool of dysregulated miRNAs studied by us, hsa-miR-92b-5p regulates coronin 1A expression under the effect of HIV-1 Tat. These findings highlight the novel roles of coronin 1A in regulating astrocyte activity in stimulated conditions and astrocyte reactivity observed in HIV-1 neuropathogenesis.

Suppression of caspase 8 activity by a coronin 1-PI3Kδ pathway promotes T cell survival independently of TCR and IL-7 signaling

The control of T cell survival is crucial for defense against infectious pathogens or emerging cancers. Although the survival of peripheral naïve T cells has been proposed to be controlled by interleukin-7 (IL-7) signaling and T cell receptor (TCR) activation by peptide-loaded major histocompatibility complexes (pMHC), the essential roles for these pathways in thymic output and T cell proliferation have complicated the analysis of their contributions to T cell survival. Here, we showed that the WD repeat–containing protein coronin 1, which is dispensable for thymic selection and output, promoted naïve T cell survival in the periphery in a manner that was independent of TCR and IL-7 signaling. Coronin 1 was required for the maintenance of the basal activity of phosphoinositide 3-kinase δ (PI3Kδ), thereby suppressing caspase 8–mediated apoptosis. These results therefore reveal a coronin 1–dependent PI3Kδ pathway that is independent of pMHC:TCR and IL-7 signaling and essential for peripheral T cell survival.

Major Outer Membrane Protein from Legionella pneumophila Inhibits Phagocytosis but Enhances Chemotaxis of RAW 264.7 Macrophages by Regulating the FOXO1/Coronin-1 Axis

Legionella pneumophila is an intracellular pathogen that can cause Legionnaire's disease by invading alveolar epithelial cells and macrophages. The major outer membrane protein (MOMP) plays an important role in the interaction between bacteria and host cells. However, the role of MOMP in the process of L. pneumophila invasion of macrophages and its working mechanism remain unknown. We aimed to explore the effects of MOMP on phagocytosis and chemotaxis of RAW 264.7 macrophages. The chemotactic activity, toxicity, and phagocytosis of RAW 264.7 cocultured with different concentrations of MOMP were determined by Transwell, CCK-8, and neutral red uptake assays, respectively. Target genes were detected by double-luciferase and pull down assays. qRT-PCR and Western blot were performed to analyze the expression of several important proteins involved in the immune response pathway, including coronin-1, interleukins (IL-10), forkhead transcription factor 1 (FOXO1), nucleotide-binding oligomerization domain protein (NOD) 1, NOD2, and receptor-interacting protein (RIP) 2. After coculturing with MOMP, cytological observation indicated a decrease of phagocytosis and a marked increase of chemotaxis in RAW 264.7 macrophages. The phagocytosis degree of RAW 264.7 macrophage varied with the concentration gradient of MOMP in a time-dependent manner. MOMP could increase the expression levels of MCP-1, IL-10, NOD2, and RIP2 and decrease the expression levels of FOXO1 and coronin-1 in cell culture supernatants. In addition, we found that FOXO1 could promote its transcription by binding to the promoter of coronin-1. The results of the present study suggested that MOMP could inhibit phagocytosis and facilitate chemotaxis of RAW 264.7 macrophage, which might be associated with the FOXO1/coronin-1 axis.

Epstein-Barr Virus in Inborn Immunodeficiency-More Than Infection

Simple Summary

Epstein–Barr Virus (EBV) is a common virus that is readily controlled by a healthy immune system and rarely causes serious problems in infected people. However, patients with certain genetic defects of their immune system might have difficulties controlling EBV and often develop severe and life-threatening conditions, such as severe inflammation and malignancies. In this review, we provide a summary of inherited immune diseases that lead to a high susceptibility to EBV infection and discuss how this infection is associated with cancer development.

Abstract

Epstein–Barr Virus (EBV) is a ubiquitous virus affecting more than 90% of the world’s population. Upon infection, it establishes latency in B cells. It is a rather benign virus for immune-competent individuals, in whom infections usually go unnoticed. Nevertheless, EBV has been extensively associated with tumorigenesis. Patients suffering from certain inborn errors of immunity are at high risk of developing malignancies, while infection in the majority of immune-competent individuals does not seem to lead to immune dysregulation. Herein, we discuss how inborn mutations in TNFRSF9, CD27, CD70, CORO1A, CTPS1, ITK, MAGT1, RASGRP1, STK4, CARMIL2, SH2D1A, and XIAP affect the development, differentiation, and function of key factors involved in the immunity against EBV, leading to increased susceptibility to lymphoproliferative disease and lymphoma.

Tumor Immune Microenvironment Characterization of Primary Lung Adenocarcinoma and Lymph Node Metastases

Background

The essential roles of the tumor microenvironment (TME) have been recognized during the initiation and progression of primary lung adenocarcinoma (LUAD). The aim of the present study was to delineate the immune landscape in both primary cancer and matched lymph node metastasis from a cohort of locally advanced stage LUAD patients with distinct outcomes.

Methods

Formalin-fixed, paraffin-embedded samples were collected from 36 locally advanced LUAD patients. Transcriptome data of the tumor immune microenvironment were resolved using an immune oncology panel RNA sequencing platform. Bioinformatics approaches were used to determine the differentially expressed genes (DEGs), dysregulated pathways, and immune cell fraction between patients with early recurrence (ER) and late recurrence (LR).

Results

Here, we showed that in primary cancer tissues, 23 DEGs were obtained between patients with ER and LR. Functional analysis revealed that the LR in LUAD patients may be associated with enriched gene sets belonging to the antigen presentation and MHC protein complex, innate immune response, and IFN-γ signaling pathways. Next, the transcriptome data were adopted to quantify immune cell fractions, indicating that high infiltration of mast cells and neutrophils was correlated with ER. Interestingly, similar findings were observed in metastatic lymph nodes from patients suffering from ER or LR. By analyzing the shared immune features of primary cancers and lymphatic metastases, we unraveled the prognostic value and joint utility of two DEGs, CORO1A and S100A8.

Conclusions

In LUAD, the enrichment in antigen presentation, MHC protein complex, and IFN-γ signaling, and low infiltration of neutrophils in primary or metastatic nodules may be indications for a favorable prognosis. Integrated with bioinformatics approaches, transcriptome data of immune-related genes from formalin-fixed, paraffin-embedded (FFPE) samples can effectively profile the landscape of the tumor immune microenvironment and help predict clinical outcomes.

The Actin-Disassembly Protein Glia Maturation Factor γ Enhances Actin Remodeling and B Cell Antigen Receptor Signaling at the Immune Synapse

Signaling by the B cell antigen receptor (BCR) initiates actin remodeling. The assembly of branched actin networks that are nucleated by the Arp2/3 complex exert outward force on the plasma membrane, allowing B cells to form membrane protrusions that can scan the surface of antigen-presenting cells (APCs). The resulting Arp2/3 complex-dependent actin retrograde flow promotes the centripetal movement and progressive coalescence of BCR microclusters, which amplifies BCR signaling. Glia maturation factor γ (GMFγ) is an actin disassembly-protein that releases Arp2/3 complex-nucleated actin filaments from actin networks. By doing so, GMFγ could either oppose the actions of the Arp2/3 complex or support Arp2/3 complex-nucleated actin polymerization by contributing to the recycling of actin monomers and Arp2/3 complexes. We now show that reducing the levels of GMFγ in human B cell lines via transfection with a specific siRNA impairs the ability of B cells to spread on antigen-coated surfaces, decreases the velocity of actin retrograde flow, diminishes the coalescence of BCR microclusters into a central cluster at the B cell-APC contact site, and decreases APC-induced BCR signaling. These effects of depleting GMFγ are similar to what occurs when the Arp2/3 complex is inhibited. This suggests that GMFγ cooperates with the Arp2/3 complex to support BCR-induced actin remodeling and amplify BCR signaling at the immune synapse.

Actin Dynamics at the T Cell Synapse as Revealed by Immune-Related Actinopathies

The actin cytoskeleton is composed of dynamic filament networks that build adaptable local architectures to sustain nearly all cellular activities in response to a myriad of stimuli. Although the function of numerous players that tune actin remodeling is known, the coordinated molecular orchestration of the actin cytoskeleton to guide cellular decisions is still ill defined. T lymphocytes provide a prototypical example of how a complex program of actin cytoskeleton remodeling sustains the spatio-temporal control of key cellular activities, namely antigen scanning and sensing, as well as polarized delivery of effector molecules, via the immunological synapse. We here review the unique knowledge on actin dynamics at the T lymphocyte synapse gained through the study of primary immunodeficiences caused by mutations in genes encoding actin regulatory proteins. Beyond the specific roles of individual actin remodelers, we further develop the view that these operate in a coordinated manner and are an integral part of multiple signaling pathways in T lymphocytes.

Genome-wide interference of ZNF423 with B-lineage transcriptional circuitries in acute lymphoblastic leukemia

Aberrant expression of the transcriptional modulator and early B-cell factor 1 (EBF1) antagonist ZNF423 has been implicated in B-cell leukemogenesis, but its impact on transcriptional circuitries in lymphopoiesis has not been elucidated in a comprehensive manner. Herein, in silico analyses of multiple expression data sets on 1354 acute leukemia samples revealed a widespread presence of ZNF423 in various subtypes of acute lymphoblastic leukemia (ALL). Average expression of ZNF423 was highest in ETV6-RUNX1, B-other, and TCF3-PBX1 ALL followed by BCR-ABL, hyperdiploid ALL, and KMT2A-rearranged ALL. In a KMT2A-AFF1 pro-B ALL model, a CRISPR-Cas9-mediated genetic ablation of ZNF423 decreased cell viability and significantly prolonged survival of mice upon xenotransplantation. For the first time, we characterized the genome-wide binding pattern of ZNF423, its impact on the chromatin landscape, and differential gene activities in a B-lineage context. In general, chromatin-bound ZNF423 was associated with a depletion of activating histone marks. At the transcriptional level, EBF1-dependent transactivation was disrupted by ZNF423, whereas repressive and pioneering activities of EBF1 were not discernibly impeded. Unexpectedly, we identified an enrichment of ZNF423 at canonical EBF1-binding sites also in the absence of EBF1, which was indicative of intrinsic EBF1-independent ZNF423 activities. A genome-wide motif search at EBF1 target gene loci revealed that EBF1 and ZNF423 co-regulated genes often contain SMAD1/SMAD4-binding motifs as exemplified by the TGFB1 promoter, which was repressed by ZNF423 outcompeting EBF1 by depending on its ability to bind EBF1 consensus sites and to interact with EBF1 or SMADs. Overall, these findings underscore the wide scope of ZNF423 activities that interfere with B-cell lymphopoiesis and contribute to leukemogenesis.

Dissecting heterogeneous cell populations across drug and disease conditions with PopAlign

Single-cell measurement techniques can now probe gene expression in heterogeneous cell populations from the human body across a range of environmental and physiological conditions. However, new mathematical and computational methods are required to represent and analyze gene-expression changes that occur in complex mixtures of single cells as they respond to signals, drugs, or disease states. Here, we introduce a mathematical modeling platform, PopAlign, that automatically identifies subpopulations of cells within a heterogeneous mixture and tracks gene-expression and cell-abundance changes across subpopulations by constructing and comparing probabilistic models. Probabilistic models provide a low-error, compressed representation of single-cell data that enables efficient large-scale computations. We apply PopAlign to analyze the impact of 40 different immunomodulatory compounds on a heterogeneous population of donor-derived human immune cells as well as patient-specific disease signatures in multiple myeloma. PopAlign scales to comparisons involving tens to hundreds of samples, enabling large-scale studies of natural and engineered cell populations as they respond to drugs, signals, or physiological change.

Induction of Allograft Tolerance While Maintaining Immunity Against Microbial Pathogens: Does Coronin 1 Hold a Key?

Selective suppression of graft rejection while maintaining anti-pathogen responses has been elusive. Thus far, the most successful strategies to induce suppression of graft rejection relies on inhibition of T-cell activation. However, the very same mechanisms that induce allograft-specific T-cell suppression are also important for immunity against microbial pathogens as well as oncogenically transformed cells, resulting in significant immunosuppression-associated comorbidities. Therefore, defining the pathways that differentially regulate anti-graft versus antimicrobial T-cell responses may allow the development of regimen to induce allograft-specific tolerance. Recent work has defined a molecular pathway driven by the immunoregulatory protein coronin 1 that regulates the phosphodiesterase/cyclic adenosine monophosphate pathway and modulates T cell responses. Interestingly, disruption of coronin 1 promotes allograft tolerance while immunity towards a range of pathogenic microbes is maintained. Here, we briefly review the work leading up to these findings as well as their possible implications for transplantation medicine.

Wnt5a regulates Ameloblastoma Cell Migration by modulating Mitochondrial and Cytoskeletal Dynamics

Objective: Abnormal expression of Wnt5a has been detected in various tumors, including ameloblastoma (AB). Yet, there is no specific mechanistic evidence for the functional role of Wnt5a in AB. In this study, we aimed to conduct a mechanistic examination of the importance of Wnt5a in AB development. Methods: The expressions of Wnt5a and Coro1A were examined by Western blot and immunohistochemistry both in AB tissues and AM-1 cells. The number and size of mitochondria were detected by electronic transmission microscope and confocal microscope. Gain-of-function and loss-of-function assays were used to explore the biological roles of Wnt5a and Coro1A in organelle dynamics changes and cell migration. Cell migration was detected by wound healing and transwell assay. Results: We found that in AM-1 cells, up-regulation of Wnt5a led to enhanced mitochondrial energy production and altered calcium homeostasis, with elevated calcium levels directly leading to altered mitochondrial dynamics and interactions between the cytoskeleton and the mitochondria. When Wnt5a or its downstream cytoskeleton-associated protein Coro1A was knocked down, the migration capacity of AM-1 cells was markedly impaired. Conclusion: Together, these results suggest that Wnt5a plays mitochondria and cytoskeleton specific roles in regulating the development of human AB, with its down-regulation leading to impaired tumor development, thus highlighting Wnt5a or Coro1A as potentially viable therapeutic targets for the treatment of AB.

Proteomic analysis in lupus mice identifies Coronin-1A as a potential biomarker for lupus nephritis

BACKGROUND

Approximately 50% of systemic lupus erythematosus (SLE) patients develop nephritis, which is among the most severe and frequent complications of the disease and a leading cause of morbidity and mortality. Despite intensive research, there are still no reliable lupus nephritis (LN) markers in clinical use that can assess renal damage and activity with a high sensitivity and specificity. To this end, the aim of this study was to identify new clinically relevant tissue-specific protein biomarkers and possible underlying molecular mechanisms associated with renal involvement in SLE, using mass spectrometry (MS)-based proteomics.

METHODS

Kidneys were harvested from female triple congenic B6.NZMsle1/sle2/sle3 lupus mice model, and the respective sex- and age-matched C57BL/6 control mice at 12, 24 and 36 weeks of age, representing pre-symptomatic, established and end-stage LN, respectively. Proteins were extracted from kidneys, purified, reduced, alkylated and digested by trypsin. Purified peptides were separated by liquid chromatography and analysed by high-resolution MS. Data were processed by the Progenesis QIp software, and functional annotation analysis was performed using DAVID bioinformatics resources. Immunofluorescence and multiple reaction monitoring (MRM) MS methods were used to confirm prospective biomarkers in SLE mouse strains as well as human serum samples.

RESULTS

Proteomic profiling of kidney tissues from SLE and control mice resulted in the identification of more than 3800 unique proteins. Pathway analysis revealed a number of dysregulated molecular pathways that may be mechanistically involved in renal pathology, including phagosome and proximal tubule bicarbonate reclamation pathways. Proteomic analysis supported by human transcriptomic data and pathway analysis revealed Coronin-1A, Ubiquitin-like protein ISG15, and Rho GDP-dissociation inhibitor 2, as potential LN biomarkers. These results were further validated in other SLE mouse strains using MRM-MS. Most importantly, experiments in humans showed that measurement of Coronin-1A in human sera using MRM-MS can segregate LN patients from SLE patients without nephritis with a high sensitivity (100%) and specificity (100%).

CONCLUSIONS

These preliminary findings suggest that serum Coronin-1A may serve as a promising non-invasive biomarker for LN and, upon validation in larger cohorts, may be employed in the future as a screening test for renal disease in SLE patients.

Severe combined immunodeficiency pig as an emerging animal model for human diseases and regenerative medicines

Severe combined immunodeficiency (SCID) is a group of inherited disorders characterized by compromised T lymphocyte differentiation related to abnormal development of other lymphocytes [i.e., B and/or natural killer (NK) cells], leading to death early in life unless treated immediately with hematopoietic stem cell transplant. Functional NK cells may impact engraftment success of life-saving procedures such as bone marrow transplantation in human SCID patients. Therefore, in animal models, a T cell−/B cell−/NK cell+ environment provides a valuable tool for understanding the function of the innate immune system and for developing targeted NK therapies against human immune diseases. In this review, we focus on underlying mechanisms of human SCID, recent progress in the development of SCID animal models, and utilization of SCID pig model in biomedical sciences. Numerous physiologies in pig are comparable to those in human such as immune system, X-linked heritability, typical T−B+NK− cellular phenotype, and anatomy. Due to analogous features of pig to those of human, studies have found that immunodeficient pig is the most appropriate model for human SCID.

Interactome and F-Actin Interaction Analysis of Dictyostelium discoideum Coronin A

Coronin proteins are evolutionary conserved WD repeat containing proteins that have been proposed to carry out different functions. In Dictyostelium, the short coronin isoform, coronin A, has been implicated in cytoskeletal reorganization, chemotaxis, phagocytosis and the initiation of multicellular development. Generally thought of as modulators of F-actin, coronin A and its mammalian homologs have also been shown to mediate cellular processes in an F-actin-independent manner. Therefore, it remains unclear whether or not coronin A carries out its functions through its capacity to interact with F-actin. Moreover, the interacting partners of coronin A are not known. Here, we analyzed the interactome of coronin A as well as its interaction with F-actin within cells and in vitro. Interactome analysis showed the association with a diverse set of interaction partners, including fimbrin, talin and myosin subunits, with only a transient interaction with the minor actin10 isoform, but not the major form of actin, actin8, which was consistent with the absence of a coronin A-actin interaction as analyzed by co-sedimentation from cells and lysates. In vitro, however, purified coronin A co-precipitated with rabbit muscle F-actin in a coiled-coil-dependent manner. Our results suggest that an in vitro interaction of coronin A and rabbit muscle actin may not reflect the cellular interaction state of coronin A with actin, and that coronin A interacts with diverse proteins in a time-dependent manner.

Coronin 1 Is Required for Integrin β2 Translocation in Platelets

Remodeling of the actin cytoskeleton is one of the critical events that allows platelets to undergo morphological and functional changes in response to receptor-mediated signaling cascades. Coronins are a family of evolutionarily conserved proteins implicated in the regulation of the actin cytoskeleton, represented by the abundant coronins 1, 2, and 3 and the less abundant coronin 7 in platelets, but their functions in these cells are poorly understood. A recent report revealed impaired agonist-induced actin polymerization and cofilin phosphoregulation and altered thrombus formation in vivo as salient phenotypes in the absence of an overt hemostasis defect in vivo in a knockout mouse model of coronin 1. Here we show that the absence of coronin 1 is associated with impaired translocation of integrin β2 to the platelet surface upon stimulation with thrombin while morphological and functional alterations, including defects in Arp2/3 complex localization and cAMP-dependent signaling, are absent. Our results suggest a large extent of functional overlap among coronins 1, 2, and 3 in platelets, while aspects like integrin β2 translocation are specifically or predominantly dependent on coronin 1.

Genome-Wide Association Study Identifies Genomic Loci Affecting Filet Firmness and Protein Content in Rainbow Trout

Filet quality traits determine consumer satisfaction and affect profitability of the aquaculture industry. Soft flesh is a criterion for fish filet downgrades, resulting in loss of value. Filet firmness is influenced by many factors, including rate of protein turnover. A 50K transcribed gene SNP chip was used to genotype 789 rainbow trout, from two consecutive generations, produced in the USDA/NCCCWA selective breeding program. Weighted single-step GBLUP (WssGBLUP) was used to perform genome-wide association (GWA) analyses to identify quantitative trait loci affecting filet firmness and protein content. Applying genomic sliding windows of 50 adjacent SNPs, 212 and 225 SNPs were associated with genetic variation in filet shear force and protein content, respectively. Four common SNPs in the ryanodine receptor 3 gene (RYR3) affected the aforementioned filet traits; this association suggests common mechanisms underlying filet shear force and protein content. Genes harboring SNPs were mostly involved in calcium homeostasis, proteolytic activities, transcriptional regulation, chromatin remodeling, and apoptotic processes. RYR3 harbored the highest number of SNPs (n = 32) affecting genetic variation in shear force (2.29%) and protein content (4.97%). Additionally, based on single-marker analysis, a SNP in RYR3 ranked at the top of all SNPs associated with variation in shear force. Our data suggest a role for RYR3 in muscle firmness that may be considered for genomic- and marker-assisted selection in breeding programs of rainbow trout.

From the "missing self" hypothesis to adaptive NK cells: Insights of NK cell-mediated effector functions in immune surveillance

The original discovery of NK cells approximately 40 yr ago was based on their unique capability to kill tumor cells without prior sensitization or priming, a process named natural cytotoxicity. Since then, several studies have documented that NK cells can kill hematopoietic and nonhematopoietic cancer cells. NK cells also recognize and kill cells that have undergone viral infections. Besides natural cytotoxicity, NK cells are also major effectors of antibody-dependent cell cytotoxicity (ADCC). Therefore, NK cells are well "armed" to recognize and mount immune responses against "insults" that result from cell transformation and viral infections. Because of these attributes, an essential role of NK cells in tumor surveillance was noted. Indeed, several studies have shown a correlation between impaired NK cell cytotoxicity and a higher risk of developing cancer. This evidence led to the idea that cancer initiation and progress is intimately related to an abnormal or misdirected immune response. Whereas all these ideas remain current, it is also true that NK cells represent a heterogeneous population with different abilities to secrete cytokines and to mediate cytotoxic functions. In addition, recent data has shown that NK cells are prone to suffer epigenetic modifications resulting in the acquisition of previously unrecognized attributes such as memory and long-term survival. Such NK cells, referred as "adaptive" or "memory-like," also display effector functions that are not necessarily equal to those observed in conventional NK cells. Given the new evidence available, it is essential to discuss the conceptual reasoning and misconceptions regarding the role of NK cells in immune surveillance and immunotherapy.

Disruption of Coronin 1 Signaling in T Cells Promotes Allograft Tolerance while Maintaining Anti-Pathogen Immunity

The ability of the immune system to discriminate self from non-self is essential for eradicating microbial pathogens but is also responsible for allograft rejection. Whether it is possible to selectively suppress alloresponses while maintaining anti-pathogen immunity remains unknown. We found that mice deficient in coronin 1, a regulator of naive T cell homeostasis, fully retained allografts while maintaining T cell-specific responses against microbial pathogens. Mechanistically, coronin 1-deficiency increased cyclic adenosine monophosphate (cAMP) concentrations to suppress allo-specific T cell responses. Costimulation induced on microbe-infected antigen presenting cells was able to overcome cAMP-mediated immunosuppression to maintain anti-pathogen immunity. In vivo pharmacological modulation of this pathway or a prior transfer of coronin 1-deficient T cells actively suppressed allograft rejection. These results define a coronin 1-dependent regulatory axis in T cells important for allograft rejection and suggest that modulation of this pathway may be a promising approach to achieve long-term acceptance of mismatched allografts.

Naïve CD8+ T-Cells Engage a Versatile Metabolic Program Upon Activation in Humans and Differ Energetically From Memory CD8+ T-Cells

Background: Characterization of the intracellular biochemical processes that regulate the generation and maintenance of effector and memory CD8⁺ T-cells from naïve precursors is essential for our understanding of adaptive immune responses and the development of immunotherapies. However, the metabolic determinants of antigen-driven activation and differentiation remain poorly defined, especially in humans.

Methods: We used a variety of different approaches, including gene expression profiling and measurements of nutrient flux, to characterize the basal and activation-induced energetic requirements of naïve and phenotypically-defined subsets of human memory CD8⁺ T-cells.

Findings: Profound metabolic differences were apparent as a function of differentiation status, both at rest and in response to stimulation via the T cell receptor (TCR). Of particular note, resting naïve CD8⁺ T cells were largely quiescent, but rapidly upregulated diverse energetic pathways after ligation of surface-expressed TCRs. Moreover, autophagy and the mechanistic target of rapamycin (mTOR)-dependent glycolytic pathway were identified as critical mediators of antigen-driven priming in the naïve CD8⁺ T cell pool, the efficiency of which was dampened by the presence of neutral lipids and fatty acids.

Interpretation: These observations provide a metabolic roadmap of the CD8⁺ T-cell compartment in humans and reveal potentially selective targets for novel immunotherapies.

Macrophage-microbe interaction: lessons learned from the pathogen Mycobacterium tuberculosis

Macrophages, being the cornerstone of the immune system, have adapted the ancient nutrient acquisition mechanism of phagocytosis to engulf various infectious organisms thereby helping to orchestrate an appropriate host response. Phagocytosis refers to the process of internalization and degradation of particulate material, damaged and senescent cells and microorganisms by specialized cells, after which the vesicle containing the ingested particle, the phagosome, matures into acidic phagolysosomes upon fusion with hydrolytic enzyme-containing lysosomes. The destructive power of the macrophage is further exacerbated through the induction of macrophage activation upon a variety of inflammatory stimuli. Despite being the end-point for many phagocytosed microbes, the macrophage can also serve as an intracellular survival niche for a number of intracellular microorganisms. One microbe that is particularly successful at surviving within macrophages is the pathogen Mycobacterium tuberculosis, which can efficiently manipulate the macrophage at several levels, including modulation of the phagocytic pathway as well as interfering with a number of immune activation pathways that normally would lead to eradication of the internalized bacilli. M. tuberculosis excels at circumventing destruction within macrophages, thus establishing itself successfully for prolonged times within the macrophage. In this contribution, we describe a number of general features of macrophages in the context of their function to clear an infection, and highlight the strategies employed by M. tuberculosis to counter macrophage attack. Interestingly, research on the evasion tactics employed by M. tuberculosis within macrophages not only helps to design strategies to curb tuberculosis, but also allows a better understanding of host cell biology.

Getting in and Staying Alive: Role for Coronin 1 in the Survival of Pathogenic Mycobacteria and Naïve T Cells

There are many different pathogenic stimuli that are able to activate the immune system, ranging from microbes that include bacteria, viruses, fungi, and parasites to host-derived triggers such as autoantigens that can induce autoimmunity as well as neoantigens involved in tumorigenesis. One of the key interactions shaping immunity toward these triggers involves the encounter of antigen-processing and -presenting cells such as macrophages and dendritic cells with T cells, resulting in immune responses that are highly selective for the antigenic trigger. Research over the past few years has implicated members of the coronin protein family, in particular coronin 1, in responses against several pathogenic triggers. While coronin 1 was initially described as a host factor allowing the intracellular survival of the pathogen Mycobacterium tuberculosis, subsequent work showed it to be a crucial factor for naïve T cell homeostasis. The activity of coronin 1 in allowing the intracellular survival of pathogenic mycobacteria is relatively well characterized, involving the activation of the Ca²⁺/calcineurin pathway, while coronin 1’s role in modulating naïve T cell homeostasis remains more enigmatic. In this mini review, we discuss the knowledge on the role for coronin 1 in immune cell functioning and provide a number of potential scenarios via which coronin 1 may be able to regulate naïve T cell homeostasis.

Inherited Immunodeficiencies With High Predisposition to Epstein-Barr Virus-Driven Lymphoproliferative Diseases

Epstein–Barr Virus (EBV) is a gamma-herpes virus that infects 90% of humans without any symptoms in most cases, but has an oncogenic potential, especially in immunocompromised individuals. In the past 30 years, several primary immunodeficiencies (PIDs) associated with a high risk to develop EBV-associated lymphoproliferative disorders (LPDs), essentially consisting of virus-associated hemophagocytic syndrome, non-malignant and malignant B-cell LPDs including non-Hodgkin and Hodgkin’s types of B lymphomas have been characterized. Among them are SH2D1A (SAP), XIAP, ITK, MAGT1, CD27, CD70, CTPS1, RASGRP1, and CORO1A deficiencies. Penetrance of EBV infection ranges from 50 to 100% in those PIDs. Description of large cohorts and case reports has refined the specific phenotypes associated with these PIDs helping to the diagnosis. Specific pathways required for protective immunity to EBV have emerged from studies of these PIDs. SLAM-associated protein-dependent SLAM receptors and MAGT1-dependent NKG2D pathways are important for T and NK-cell cytotoxicity toward EBV-infected B-cells, while CD27–CD70 interactions are critical to drive the expansion of EBV-specific T-cells. CTPS1 and RASGRP1 deficiencies further strengthen that T-lymphocyte expansion is a key step in the immune response to EBV. These pathways appear to be also important for the anti-tumoral immune surveillance of abnormal B cells. Monogenic PIDs should be thus considered in case of any EBV-associated LPDs.

From Phagocytes to Immune Defense: Roles for Coronin Proteins in Dictyostelium and Mammalian Immunity

Microbes have interacted with eukaryotic cells for as long as they have been co-existing. While many of these interactions are beneficial for both the microbe as well as the eukaryotic cell, several microbes have evolved into pathogenic species. For some of these pathogens, host cell invasion results in irreparable damage and thus host cell destruction, whereas others use the host to avoid immune detection and elimination. One of the latter pathogens is Mycobacterium tuberculosis, arguably one of the most notorious pathogens on earth. In mammalian macrophages, M. tuberculosis manages to survive within infected macrophages by avoiding intracellular degradation in lysosomes using a number of different strategies. One of these is based on the recruitment and phagosomal retention of the host protein coronin 1, that is a member of the coronin protein family and a mammalian homolog of coronin A, a protein identified in Dictyostelium. Besides mediating mycobacterial survival in macrophages, coronin 1 is also an important regulator of naïve T cell homeostasis. How, exactly, coronin 1 mediates its activity in immune cells remains unclear. While in lower eukaryotes coronins are involved in cytoskeletal regulation, the functions of the seven coronin members in mammals are less clear. Dictyostelium coronins may have maintained multiple functions, whereas the mammalian coronins may have evolved from regulators of the cytoskeleton to modulators of signal transduction. In this minireview, we will discuss the different studies that have contributed to understand the molecular and cellular functions of coronin proteins in mammals and Dictyostelium.

Beta and Gamma Human Herpesviruses: Agonistic and Antagonistic Interactions with the Host Immune System

Viruses are the most abundant and diverse biological entities in the planet. Historically, our main interest in viruses has focused on their pathogenic role, recognized by pandemics that have decimated the world population. However, viral infections have also played a major role in the evolution of cellular organisms, both through interchanging of genes with novel functions and shaping the immune system. Examples abound of infections that seriously compromise the host integrity, but evidence of plant and insect viruses mutualistic relationships have recently surfaced in which infected hosts are better suited for survival, arguing that virus-host interactions are initially parasitic but become mutualistic over years of co-evolution. A similar mutual help scenario has emerged with commensal gut bacteria. EBV is a herpesvirus that shares more than a hundred million years of co-evolution with humans, today successfully infecting close to 100% of the adult world population. Infection is usually acquired early in childhood persisting for the host lifetime mostly without apparent clinical symptoms. Disturbance of this homeostasis is rare and results in several diseases, of which the best understood are infectious mononucleosis and several EBV-associated cancers. Less understood are recently found inborn errors of the immune system that result in primary immunodeficiencies with an increased predisposition almost exclusive to EBV-associated diseases. Puzzling to these scenarios of broken homeostasis is the co-existence of immunosuppression, inflammation, autoimmunity and cancer. Homologous to EBV, HCMV, HHV-6 and HHV-7 are herpesviruses that also latently infect most individuals. Several lines of evidence support a mutualistic equilibrium between HCMV/EBV and hosts, that when altered trigger diseases in which the immune system plays a critical role. Interestingly, these beta and gamma herpesviruses persistently infect all immune lineages and early precursor cells. In this review, we will discuss the evidence of the benefits that infection of immune cells with these herpesviruses brings to the host. Also, the circumstances in which this positive relationship is broken, predisposing the host to diseases characterized by an abnormal function of the host immune system.

Coronin 1A, a novel player in integrin biology, controls neutrophil trafficking in innate immunity

Trafficking of polymorphonuclear neutrophils (PMNs) during inflammation critically depends on the β₂ integrins lymphocyte function-associated antigen 1 (LFA-1) (CD11a/CD18) and macrophage-1 antigen (CD11b/CD18). Here, we identify coronin 1A (Coro1A) as a novel regulator of β₂ integrins that interacts with the cytoplasmic tail of CD18 and is crucial for induction of PMN adhesion and postadhesion events, including adhesion strengthening, spreading, and migration under flow conditions. Transition of PMN rolling to firm adhesion critically depends on Coro1A by regulating the accumulation of high-affinity LFA-1 in focal zones of adherent cells. Defective integrin affinity regulation in the genetic absence of Coro1A impairs leukocyte adhesion and extravasation in inflamed cremaster muscle venules in comparison with control animals. In a Helicobacter pylori mouse infection model, PMN infiltration into the gastric mucosa is dramatically reduced in Coro1A^-/- mice, resulting in an attenuated gastric inflammation. Thus, Coro1A represents an important novel player in integrin biology, with key functions in PMN trafficking during innate immunity.

Actin-binding protein coronin 1A controls osteoclastic bone resorption by regulating lysosomal secretion of cathepsin K

Osteoclasts degrade bone matrix proteins via the secretion of lysosomal enzymes. However, the precise mechanisms by which lysosomal components are transported and fused to the bone-apposed plasma membrane, termed ruffled border membrane, remain elusive. Here, we identified coronin 1A as a negative regulator of exocytotic release of cathepsin K, one of the most important bone-degrading enzymes in osteoclasts. The modulation of coronin 1A expression did not alter osteoclast differentiation and extracellular acidification, but strongly affected the secretion of cathepsin K and osteoclast bone-resorption activity, suggesting the coronin 1A-mediated regulation of lysosomal trafficking and protease exocytosis. Further analyses suggested that coronin 1A prevented the lipidation-mediated sorting of the autophagy-related protein LC3 to the ruffled border and attenuated lysosome-plasma membrane fusion. In this process, the interactions between coronin 1A and actin were crucial. Collectively, our findings indicate that coronin 1A is a pivotal component that regulates lysosomal fusion and the secretion pathway in osteoclast-lineage cells and may provide a novel therapeutic target for bone diseases.

Role for coronin 1 in mouse NK cell function

Coronin 1, a member of the evolutionary conserved WD repeat protein family of coronin proteins is expressed in all leukocytes, but a role for coronin 1 in natural killer (NK) cell homeostasis and function remains unclear. Here, we have analyzed the number and functionality of NK cells in the presence and absence of coronin 1. In coronin 1-deficient mice, absolute NK cell numbers and phenotype were comparable to wild type mice in blood, spleen and liver. Following in vitro stimulation of the activating NK cell receptors NK1.1, NKp46, Ly49D and NKG2D, coronin 1-deficient NK cells were functional with respect to interferon-γ production, degranulation and intracellular Ca2+ mobilization. Also, both wild type as well as coronin 1-deficient NK cells showed comparable cytotoxic activity. Furthermore, activation and functionality of NK cells following Vesicular Stomatitis Virus (VSV) infection was similar between wild type and coronin 1-deficient mice. Taken together these data suggest that coronin 1 is dispensable for mouse NK cell homeostasis and function.

Coronins and their role in immunological phenomena

Coronins are a large family of proteins occurring in many eukaryotes. In mammals, seven coronin genes have been identified, evidencing that coronins 1 to 6 present classic coronin structure, while coronin 7 is a tandem coronin particle, without a spiral domain, although the best characterised coronin, in terms of both structure and function, is the mammalian coronin 1. It has been proven that they are related to regulation of actin dynamics, e.g. as a result of interaction with the complex of proteins Arp2/3. These proteins also modulate the activity of immune system cells, including lymphocyte T and B cells, neutrophils and macrophages. They are involved in bacterial infections with Mycobacterium tuberculosis, M. leprae and Helicobacter pylori and participate in the response to viral infections, e.g. infections of lymphocytic choriomeningitis virus (LCMV) and vesicular stomatitis Indiana virus (VSV). Also their involvement in autoimmune diseases such as lupus erythematosus has been recorded.

Proof of Principle for a T Lymphocyte Intrinsic Function of Coronin 1A

Coronins are evolutionarily conserved proteins that were originally identified as modulators of actin-dependent processes. Studies analyzing complete Coronin 1a knock-out mice have shown that this molecule is an important regulator of naive T cell homeostasis and it has been linked to immune deficiencies as well as autoimmune disorders. Nevertheless, because Coronin 1A is strongly expressed in all leukocyte subsets, it is not conclusive whether or not this phenotype is attributed to a T cell-intrinsic function of Coronin 1A. To address this research question, we have generated a T cell-specific Coronin 1a knock-out mouse (Coro1afl/fl × Cd4[Cre]). Deletion of Coronin 1A specifically in T cells led to a strong reduction in T cell number and a shift toward the effector/memory phenotype in peripheral lymphoid organs when compared with Cd4[Cre] mice expressing wild-type Coronin 1A. In contrast to peripheral lymphoid tissue, thymocyte number and subsets were not affected by the deletion of Coronin 1a Furthermore, T cell-specific Coronin 1a knock-out mice were largely resistant to the induction of autoimmunity when tested in the myelin oligoglycoprotein-induced EAE mouse model of multiple sclerosis. Thus, the phenotype of T cell-specific Coronin 1a deletion resembles the phenotype observed with conventional (whole body) Coronin 1a knock-out mice. In summary, our findings provide formal proof of the predominant T cell-intrinsic role of Coronin 1A.

The Actin Filament-Binding Protein Coronin Regulates Motility in Plasmodium Sporozoites

Parasites causing malaria need to migrate in order to penetrate tissue barriers and enter host cells. Here we show that the actin filament-binding protein coronin regulates gliding motility in Plasmodium berghei sporozoites, the highly motile forms of a rodent malaria-causing parasite transmitted by mosquitoes. Parasites lacking coronin show motility defects that impair colonization of the mosquito salivary glands but not migration in the skin, yet result in decreased transmission efficiency. In non-motile sporozoites low calcium concentrations mediate actin-independent coronin localization to the periphery. Engagement of extracellular ligands triggers an intracellular calcium release followed by the actin-dependent relocalization of coronin to the rear and initiation of motility. Mutational analysis and imaging suggest that coronin organizes actin filaments for productive motility. Using coronin-mCherry as a marker for the presence of actin filaments we found that protein kinase A contributes to actin filament disassembly. We finally speculate that calcium and cAMP-mediated signaling regulate a switch from rapid parasite motility to host cell invasion by differentially influencing actin dynamics.

Parasites causing malaria are transmitted by mosquitoes and need to migrate to cross tissue barriers. The form of the parasite transmitted by the mosquito, the so-called sporozoite, needs motility to enter the salivary glands, to migrate within the skin and to enter into blood capillaries and eventually hepatocytes, where the parasites differentiate into thousands of merozoites that invade red blood cells. Sporozoite motility is based on an actin-myosin motor, as is the case in many other eukaryotic cells. However, most eukaryotic cells move much slower than sporozoites. How these parasites reach their high speed is not clear but current evidence suggests that actin filaments need to be organized by either actin-binding proteins or membrane proteins that link the filaments to an extracellular substrate.

The present study explores the role of the actin filament-binding protein coronin in the motility of sporozoites of the rodent model parasite Plasmodium berghei. We found that the deletion of P. berghei coronin leads to defects in parasite motility and thus lower infection of mosquito salivary glands, which translates into less efficient transmission of the parasites. Our experiments suggest that coronin organizes actin filaments to achieve rapid and directional motility. We also identify two signaling pathways that converge to regulate actin filament dynamics and suggest that they play a role in switching the parasite from its motility mode to a cell invasion mode.

Investigating the Function of Coronin A in the Early Starvation Response of Dictyostelium discoideum by Aggregation Assays

Dictyostelium discoideum amoeba are found in soil, feeding on bacteria. When food sources become scarce, they secrete factors to initiate a multicellular development program, during which single cells chemotax towards aggregation centers(1-4). This process is dependent on the release of cyclic adenosine monophosphate (cAMP)(5). cAMP is produced in waves through the concerted action of adenylate cyclase and phosphodiesterases, and binds to G protein-coupled cAMP receptors(6,7). A widely used assay to analyze the mechanisms involved in the developmental cycle of the lower eukaryote Dictyostelium discoideum is based on the observation of cell aggregation in submerged conditions(8,9). This protocol describes the analysis of the role of coronin A in the developmental cycle by starvation in tissue-culture plates submerged in balanced salt solution (BSS)(10). Coronin A is a member of the widely conserved protein family of coronins that have been implicated in a wide variety of activities(11,12). Dictyostelium cells lacking coronin A are unable to form multicellular aggregates, and this defect can be rescued by supplying pulses of cAMP, suggesting that coronin A acts upstream of the cAMP cascade(10). The techniques described in these studies provide robust tools to investigate functions of proteins during the initial stages of the developmental cycle of Dictyostelium discoideum upstream of the cAMP cascade. Therefore, utilizing this aggregation assay may allow the further study of coronin A function and advance our understanding of coronin biology.

Recurrent viral infections associated with a homozygous CORO1A mutation that disrupts oligomerization and cytoskeletal association

BACKGROUND

Coronin-1A (CORO1A) is a regulator of actin dynamics important for T-cell homeostasis. CORO1A deficiency causes T(-)B(+) natural killer-positive severe combined immunodeficiency or T-cell lymphopenia with severe viral infections. However, because all known human mutations in CORO1A abrogate protein expression, the role of the protein's functional domains in host immunity is unknown.

OBJECTIVE

We sought to identify the cause of the primary immunodeficiency in 2 young adult siblings with a history of disseminated varicella, cutaneous warts, and CD4(+) T-cell lymphopenia.

METHODS

We performed immunologic, genetic, and biochemical studies in the patients, family members, and healthy control subjects.

RESULTS

Both patients had CD4(+) T-cell lymphopenia and decreased lymphocyte proliferation to mitogens. IgG, IgM, IgA, and specific antibody responses were normal. Whole-genome sequencing identified a homozygous frameshift mutation in CORO1A disrupting the last 2 C-terminal domains by replacing 61 amino acids with a novel 91-amino-acid sequence. The CORO1A(S401fs) mutant was expressed in the patients' lymphocytes at a level comparable with that of wild-type CORO1A in normal lymphocytes but did not oligomerize and had impaired cytoskeletal association. CORO1A(S401fs) was associated with increased filamentous actin accumulation in T cells, severely defective thymic output, and impaired T-cell survival but normal calcium flux and cytotoxicity, demonstrating the importance of CORO1A oligomerization and subcellular localization in T-cell homeostasis.

CONCLUSIONS

We describe a truncating mutation in CORO1A that permits protein expression and survival into young adulthood. Our studies demonstrate the importance of intact CORO1A C-terminal domains in thymic egress and T-cell survival, as well as in defense against viral pathogens.

F-actin remodeling defects as revealed in primary immunodeficiency disorders

Primary immunodeficiencies (PIDs) are a heterogeneous group of immune-related diseases. PIDs develop due to defects in gene-products that have consequences to immune cell function. A number of PID-proteins is involved in the remodeling of filamentous actin (f-actin) to support the generation of a contact zone between the antigen-specific T cell and antigen presenting cell (APC): the immunological synapse (IS). IS formation is the first step towards T-cell activation and essential for clonal expansion and acquisition of effector function. We here evaluated PIDs in which aberrant f-actin-driven IS formation may contribute to the PID disease phenotypes as seen in patients. We review examples of such contributions to PID phenotypes from literature, and highlight cases in which PID-proteins were evaluated for a role in f-actin polymerization and IS formation. We conclude with the proposition that patient groups might benefit from stratifying them in distinct functional groups in regard to their f-actin remodeling phenotypes in lymphocytes.