B cells play critical roles in humoral immunity to infection, vaccination, and autoimmunity. The differentiation of B cells into antibody-producing plasma cells (PCs) has been extensively studied, but the role of metabolic transporters that mediate nutrient uptake during PC differentiation is not well-understood. Here, we characterized the dependence of B cells and PC differentiation on the neutral amino acid transporter SLC7A5. We demonstrate that SLC7A5 promotes B cell functions including proliferation and PC differentiation in vitro and in vivo after immunization with T dependent and independent antigens. Deletion of SLC7A5 in B cells suppressed the function of mTORC1 and enforced mTORC1 activity rescued PC differentiation. The role of SLC7A5 in B cells appears to be unrelated to leucine uptake because B cells were insensitive to extracellular leucine depletion. Defects in SLC7A5-deficient B cells could, however, be rescued by extracellular methionine supplementation, suggesting a role for methionine in SLC7A5-dependent B cell function and PC differentiation. Our study provides evidence for a leucine-independent role of SLC7A5 in B cell function and PC differentiation.

Background: Zinc (Zn2+) is the second most abundant trace metal in eukaryotes and essential for many cellular functions. It possesses well-established immunomodulatory properties and disruption of Zn2+ signaling compromises immune functions resulting in immunodeficiency. In addition, Zn2+ has been implicated in several autoimmune diseases such as multiple sclerosis (MS). Methods: We used a forward genomic screen to identify Zn2+ transporters that control the function of encephalitogenic T helper (Th) 17 cells, and thus, drive CNS inflammation in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. We measured cytosolic Zn2+ levels in T cells with a genetically encoded Zn2+ reporter and used confocal microscopy to determine the subcellular localization of ZIP3. We used shRNA and CRISPR gene editing to delete Slc39a3 (encoding ZIP3) to determine its role in CD4+ T cells in vitro and pathogenic Th17 (pTh17) cells in vivo in EAE. Results: Using a shRNA screen in myelin-specific pTh17 cells in vivo, we found that ZIP3 is required for their expansion in the CNS of mice with EAE. When ectopically expressed, ZIP3 was located predominantly in the Golgi apparatus. Deletion of Slc39a3 resulted in decreased cytosolic Zn2+ levels selectively in pTh17 cells without affecting those in non-polarized CD4+ T cells. Slc39a3-deficient pTh17 cells showed an increased susceptibility to apoptotic cell death and reduced CD69 expression in vitro, while proliferation and cytokine production remained intact. Slc39a3 deletion in pTh17 cells significantly reduced the severity of EAE by reducing leukocyte infiltration of the CNS. Conclusions: ZIP3 is essential for the encephalitogenic function of pTh17 cells and promoting EAE, likely by regulating cytosolic Zn2+ levels.

The Ca2+ release-activated Ca2+ (CRAC) channel mediates store-operated calcium entry (SOCE), a ubiquitous pathway essential for many cell types, including immune cells. Three Orai (Orai1/2/3) proteins constitute the plasma membrane pore-forming units of CRAC channels that are activated by the endoplasmic reticulum (ER) Ca2+-sensing STIM1/2 proteins when ER Ca2+ stores are depleted. Orai1/2/3 are differentially expressed across primary cells with discernible differences in their structures and biophysical properties. Further, Orai1 has two alternatively translated isoforms: long mammalian-specific Orai1α and the 63-residue shorter Orai1β, which is evolutionarily older and conserved across vertebrates. Whether Orai1α/1β/2/3 produce unique cytosolic Ca2+ signatures that bias transcriptional responses through effectors like NFAT is unclear. Here, we used HEK293 cells engineered to express one native Orai isoform and show that all Orai isoforms couple to NFAT1/4 induction. The magnitude of NFAT1/4 induction for each Orai isoform matches that of SOCE, with the following profile: Orai1β>Orai1α>>Orai2>Orai3. Near-native re-expression of either Orai1α or Orai1β in primary murine Orai1 -/- CD4+ T cells restored SOCE, NFAT activation, cytokine production and promoted near identical transcriptional responses enriched for immune activation pathways. An analysis of genetic and clinical data of human individuals showed that homozygous null mutations selectively abolishing Orai1α are not associated with disease resembling CRAC channelopathy. Primary T cells from individuals homozygous or heterozygous for an Orai1α null mutation showed enhanced, rather than impaired, SOCE and NFAT induction. Our data indicate that NFAT activation and transcriptional outputs are primarily driven by the graded strength of SOCE mediated by each isoform of the Orai quartet.

Ca²⁺ release-activated Ca²⁺ (CRAC) channels facilitate store-operated Ca²⁺ entry in both immune and nonimmune cells. They are crucial for the function of many immune cell types and strongly associated with the pathophysiology of immune-related disorders. Inherited null mutations in the genes encoding the CRAC channel, ORAI1, and its activator STIM1, are linked to inborn errors of immunity in patients, highlighting the essential role of these channels in immunity. Preclinical studies using knockout mice and CRAC channel inhibitors (CRACi) have further demonstrated their pivotal function in the pathophysiology of immune-related conditions, including immunity to infection, autoimmunity, allergy, and other inflammatory diseases. Clinical trials in patients with inflammatory disorders underscore the potential utility of CRACi for immunotherapy. Here, we provide an overview of CRAC channels in immune cell function, review their roles in preclinical models of immune diseases, and discuss the outcomes of clinical trials involving CRACi.

Abstract Introduction Pathogenic T helper 17 (pTh17) cells are a subset of CD4+ T cells driving autoimmune diseases including multiple sclerosis (MS). Methods To identify transporters controlling pTh17 cells, we conducted an in vivo shRNA-based forward genetic screen using the experimental autoimmune encephalomyelitis (EAE) model of MS. Copper Transporter 1 (CTR1), essential for copper uptake, emerged as a key regulator of pTh17 cell differentiation and function. Copper supports different cellular processes including mitochondrial metabolism and reactive oxygen species (ROS) balance. Results Deletion of CTR1 in CD4 T cells decreased intracellular copper levels, disrupting mitochondrial respiration and rewiring metabolism. These changes disrupted the epigenetic landscape of pTh17 cells by inducing DNA hypermethylation and altered chromatin accessibility, impairing transcription factor binding. As a result, CTR1-deficient T cells showed defective differentiation into pTh17 cells, with decreased production of IL-17A and expression of Th17 signature genes, while differentiation of other CD4 subsets remained unaffected. Moreover, T cell-specific deletion of CTR1 protected mice from EAE by suppressing clonal expansion of autoreactive CD4+ T cells and CNS inflammation. Conclusion These findings establish copper as a critical regulator of pTh17 differentiation and function, revealing a previously unknown molecular link between copper homeostasis, metabolism and epigenetic regulation governing Th17-mediated autoimmunity. Funding Source Colton Autoimmunity Center Topic Categories Immune Response Regulation: Molecular Mechanisms (IRM)

Individuals with Down syndrome (DS) produce less saliva for unknown reasons resulting in chronic periodontal disease with systemic detrimental effects. Using the (Dp(16)1Yey) mouse model of DS we define the molecular mechanisms of hyposalivation and potential links to periodontal disease. We show that Dp(16)1Yey mice produce less saliva and have a higher immune burden in the salivary glands. We demonstrate that store operated calcium entry (SOCE), required for saliva secretion, is deficient in the salivary glands of Dp(16)1Yey mice. SOCE is also reduced in iPSCs from an individual with DS. We show that the oral and gut microbiomes of Dp(16)1Yey mice have abundant succinate-associated microbes and high succinate levels in the serum. We highlight associations between altered Ca2+ handling and hyposalivation, dysbiosis, and periodontal disease in DS. The administration of pilocarpine in Dp(16)1Yey mice increased salivation, suggesting that cholinergic agonists might be useful to improve the oral health of individual with DS.

Chaperone-mediated autophagy (CMA) contributes to proteostasis maintenance by selectively degrading a subset of proteins in lysosomes. CMA declines with age in most tissues, including skeletal muscle. However, the role of CMA in skeletal muscle and the consequences of its decline remain poorly understood. Here we demonstrate that CMA regulates skeletal muscle function. We show that CMA is upregulated in skeletal muscle in response to starvation, exercise and tissue repair, but declines in ageing and obesity. Using a muscle-specific CMA-deficient mouse model, we show that CMA loss leads to progressive myopathy, including reduced muscle force and degenerative myofibre features. Comparative proteomic analyses reveal CMA-dependent changes in the mitochondrial proteome and identify the sarcoplasmic–endoplasmic reticulum Ca2+-ATPase (SERCA) as a CMA substrate. Impaired SERCA turnover in CMA-deficient skeletal muscle is associated with defective calcium (Ca2+) storage and dysregulated Ca2+ dynamics. We confirm that CMA is also downregulated with age in human skeletal muscle. Remarkably, genetic upregulation of CMA activity in old mice partially ameliorates skeletal muscle ageing phenotypes. Together, our work highlights the contribution of CMA to skeletal muscle homoeostasis and myofibre integrity. Chaperone-mediated autophagy declines with age in skeletal muscle of humans and mice, leading to muscle dysfunction characterized by impaired calcium homoeostasis and mitochondrial function.

Stromal interaction molecule 1 (STIM1) is critical for store-operated Ca2+ entry (SOCE) and T cell activation. T helper 1 (TH1) cells, which express T-bet (encoded by TBX21), mediate immunity to intracellular pathogens. Although SOCE is known to regulate other TH lineages, its role in Th1 differentiation remains unclear. Here, we report a patient with an intronic loss-of-function mutation in STIM1, which abolishes SOCE and causes immunodeficiency. We demonstrate that SOCE promotes nuclear factor of activated T cells (NFAT) binding to conserved noncoding sequence (CNS)-12 in the TBX21 enhancer and enables NFAT to synergize with STAT1 to mediate TBX21 expression. While SOCE-deficient CD4+ T cells have reduced expression of TBX21 in the absence of interleukin-12 (IL-12), their expression of IL-12 receptors beta 1 and beta 2 is increased, sensitizing them to IL-12 signaling and allowing IL-12 to rescue T-bet expression. Our study reveals that the STIM1-SOCE-NFAT signaling axis is essential for the differentiation of Th1 cells depending on the cytokine milieu.

Pathogenic T helper 17 (pTh17) cells are a subset of CD4+ T cells that is critical for the pathogenesis of several autoimmune diseases including multiple sclerosis (MS). To identify transporters controlling pTh17 cells in autoimmune disease, we conducted an in vivo forward genetic screen in pTh17 cells using the experimental autoimmune encephalomyelitis (EAE) model of MS. We identified several new transporters including the copper transporter 1 (CTR1). Inside cells, copper binds to cuproenzymes that control cellular processes including oxidative phosphorylation (OXPHOS) via cytochrome C oxidase and reactive oxygen species (ROS) homeostasis via superoxide dismutase 1 (SOD1). Here we show that deletion of CTR1 in murine CD4+ T cells decreases intracellular copper levels affecting mitochondrial ROS production and respiration. Deletion of CTR1 suppresses CD4+ T cell differentiation into pTh17 cells, production of IL-17A and expression of Th17 signature genes in vitro. These effects appear to be specific to pTh17 cells because Th1 differentiation and function were not affected. Additionally, T cell-specific deletion of CTR1 protects mice from EAE in vivo which is associated with strongly reduced clonal expansion of autoreactive CD4+ T cells and CNS inflammation. Taken together, our data demonstrate that maintaining intracellular copper homeostasis is essential for the differentiation and function of pTh17 cells and their ability to cause autoimmune inflammation. Immune Response Regulation: Cellular Mechanisms (IRC)

Loss of function mutations of ORAI1 suppress store-operated Ca2+ entry (SOCE) and cause an immunodeficiency disorder called Ca2+ release-activated Ca2+ (CRAC) channelopathy. Here we report an infant patient who is compound heterozygous for p.His134Pro and p.Leu194Pro mutations in ORAI1 and whose T cells have strongly reduced SOCE. Whereas the p.Leu194Pro mutant ORAI1 protein is not expressed at the plasma membrane, the p.His134Pro mutation results in a constitutively open channel that is unresponsive to activation by stromal interaction molecule 1 (STIM1). The patient suffered from a severe form of combined immunodeficiency (CID), hemophagocytic lymphohistiocytosis (HLH) and fatal chronic cytomegalovirus infection. His immunodeficiency was characterized by an altered composition of T and NK cell compartments, impaired stimulation-induced cytokine production and signs of CD4+ T cell and NK cell activation but attenuated CD8+ T effector memory cell function. Our findings demonstrate that small constitutive SOCE through a mutant ORAI1 channel is not sufficient to provide immunity to viral infection.

A novel mutation in ORAI1 results in constitutive CRAC channel activation while abolishing stimulation-induced channel opening. The mutation is associated with severe immune dysregulation, altered T and NK cell phenotypes and function, and attenuated CD8+ T effector memory cell function.

Ca2+ signaling via the store-operated Ca2+ entry (SOCE) mediated by STIM1 and STIM2 proteins and the ORAI1 Ca2+ channel is important in saliva fluid secretion and has been associated with Sjogren's disease (SjD). However, there are no studies addressing STIM1/2 dysfunction in salivary glands or SjD in animal models. We report that mice lacking Stim1 and Stim2 [Stim1/2K14Cre(+)] in salivary glands exhibited reduced Ca2+ levels and hyposalivate. SOCE was functionally required for the activation of the Ca2+ activated Cl- channel ANO1. Ageing Stim1/2K14Cre(+) mice showed no evidence of lymphocytic infiltration or increased levels of autoantibodies characteristic of SjD, possibly associated with a downregulation of toll-like receptor 8 (Tlr8) expression. Salivary gland biopsies of SjD patients showed increased expression of STIM1 and TLR7/8. Our study shows that SOCE activates ANO1 function and fluid secretion in salivary glands and highlights a potential link between SOCE and TLR signaling in SjD.

Pathogenic CD4 T cells drive autoimmunity in diseases such as multiple sclerosis (MS) and inflammatory bowel disease (IBD). Through a forward genetic screen, we identified chloride nucleotide-sensitive channel 1A (CLNS1A) as a key regulator of inflammation in the experimental autoimmune encephalomyelitis (EAE) model of MS. CLNS1A is expressed in several subsets of CD4 T cells, including pathogenic T helper 17 (pTH17) cells. Deletion of Clns1a in T cells resulted in DNA damage, cell cycle arrest, impaired T cell proliferation, and effector function, thereby protecting mice from both EAE and IBD. We found that CLNS1A interacts with protein arginine methyl transferase 5 (PRMT5). Moreover, CLNS1A regulates symmetric histone dimethylation and the expression of genes involved in DNA repair, replication, and cell cycle progression. Thus, CLNS1A plays an important role in CD4 T cells by promoting genome stability and cell cycle progression.

Sjogren's Disease (SjD) is an autoimmune disorder characterized by salivary and lacrimal gland dysfunction and immune cell infiltration leading to gland inflammation and destruction. Although SjD is a common disease, its pathogenesis is not fully understood. In this study, we conducted a single-cell transcriptome analysis of peripheral blood mononuclear cells (PBMC) from patients with SjD and symptomatic non-SjD controls to identify cell types and functional changes involved in SjD pathogenesis. All PBMCs populations showed marked differences in gene expression between SjD patients and controls, particularly an increase in interferon (IFN) signaling gene signatures. T and B cells of SjD patients displayed a depletion of ribosomal gene expression and pathways linked to protein translation. SjD patients had increased frequencies of naive B cells, which featured a unique gene expression profile (GEP) distinct from controls and had hallmarks of B cell hyperactivation. Non-negative matrix factorization (NMF) also identified several non-overlapping GEPs in CD4+ and CD8+ T cells with differential usage in SjD patients and controls. Of these, only the Th1 activation GEP was enriched in T cells of SjD patients whereas the other two GEPs were depleted in T cells, emphasizing the important role of Th1 cells in SjD. Our study provides evidence for aberrant and unique gene expression patterns in both B and T lymphocytes of SjD patients that point to their altered activation states and may provide new insights into the pathogenesis of SjD.

Peripheral sensitization is one of the primary mechanisms underlying the pathogenesis of chronic pain. However, candidate molecules involved in peripheral sensitization remain incompletely understood. We have shown that store-operated calcium channels (SOCs) are expressed in the dorsal root ganglion (DRG) neurons. Whether SOCs contribute to peripheral sensitization associated with chronic inflammatory pain is elusive. Here we report that global or conditional deletion of Orai1 attenuates Complete Freunds adjuvant (CFA)-induced pain hypersensitivity in both male and female mice. To further establish the role of Orai1 in inflammatory pain, we performed calcium imaging and patch-clamp recordings in wild-type (WT) and Orai1 knockout (KO) DRG neurons. We found that SOC function was significantly enhanced in WT but not in Orai1 KO DRG neurons from CFA- and carrageenan-injected mice. Interestingly, the Orai1 protein level in L3/4 DRGs was not altered under inflammatory conditions. To understand how Orai1 is modulated under inflammatory pain conditions, prostaglandin E2 (PGE2) was used to sensitize DRG neurons. PGE2-induced increase in neuronal excitability and pain hypersensitivity was significantly reduced in Orai1 KO mice. PGE2-induced potentiation of SOC entry (SOCE) was observed in WT, but not in Orai1 KO DRG neurons. This effect was attenuated by a PGE2 receptor 1 (EP1) antagonist and mimicked by an EP1 agonist. Inhibition of Gq/11, PKC, or ERK abolished PGE2-induced SOCE increase, indicating PGE2-induced SOCE enhancement is mediated by EP1-mediated downstream cascade. These findings demonstrate that Orai1 plays an important role in peripheral sensitization. Our study also provides new insight into molecular mechanisms underlying PGE2-induced modulation of inflammatory pain. Significance Statement Store-operated calcium channel (SOC) Orai1 is expressed and functional in dorsal root ganglion (DRG) neurons. Whether Orai1 contributes to peripheral sensitization is unclear. The present study demonstrates that Orai1-mediated SOC function is enhanced in DRG neurons under inflammatory conditions. Global and conditional deletion of Orai1 attenuates complete Freunds adjuvant (CFA)-induced pain hypersensitivity. We also demonstrate that prostaglandin E2 (PGE2) potentiates SOC function in DRG neurons through EP1-mediated signaling pathway. Importantly, we have found that Orai1 deficiency diminishes PGE2-induced SOC function increase and reduces PGE2-induced increase in neuronal excitability and pain hypersensitivity. These findings suggest that Orai1 plays an important role in peripheral sensitization associated with inflammatory pain. Our study reveals a novel mechanism underlying PGE2/EP1-induced peripheral sensitization. Orai1 may serve as a potential target for pathological pain.

Sjogrens disease (SjD) is an autoimmune disease characterized by xerostomia (dry mouth), lymphocytic infiltration into salivary glands and the presence of SSA and SSB autoantibodies. Xerostomia is caused by hypofunction of the salivary glands and has been involved in the development of SjD. Saliva production is regulated by parasympathetic input into the glands initiating intracellular Ca2+ signals that activate the store operated Ca2+ entry (SOCE) pathway eliciting sustained Ca2+ influx. SOCE is mediated by the STIM1 and STIM2 proteins and the ORAI1 Ca2+ channel. However, there are no studies on the effects of lack of STIM1/2 function in salivary acini in animal models and its impact on SjD. Here we report that male and female mice lacking Stim1 and Stim2 (Stim1/2K14Cre) in salivary glands showed reduced intracellular Ca2+ levels via SOCE in parotid acini and hyposalivate upon pilocarpine stimulation. Bulk RNASeq of the parotid glands of Stim1/2K14Cre mice showed a decrease in the expression of Stim1/2 but no other Ca2+ associated genes mediating saliva fluid secretion. SOCE was however functionally required for the activation of the Ca2+ activated chloride channel ANO1. Despite hyposalivation, ageing Stim1/2K14Cre mice showed no evidence of lymphocytic infiltration in the glands or elevated levels of SSA or SSB autoantibodies in the serum, which may be linked to the downregulation of the toll-like receptor 8 (Tlr8). By contrast, salivary gland biopsies of SjD patients showed increased STIM1 and TLR8 expression, and induction of SOCE in a salivary gland cell line increased the expression of TLR8. Our data demonstrate that SOCE is an important activator of ANO1 function and saliva fluid secretion in salivary glands. They also provide a novel link between SOCE and TLR8 signaling which may explain why loss of SOCE does not result in SjD.

The IL-6–gp130–STAT3 signaling axis is a major regulator of inflammation. Activating mutations in the gene encoding gp130 and germline gain-of-function mutations in STAT3 (STAT3 GOF ) are associated with multi-organ autoimmunity, severe morbidity, and adverse prognosis. To dissect crucial cellular subsets and disease biology involved in activated gp130 signaling, the gp130-JAK-STAT3 axis was constitutively activated using a transgene, L-gp130 , specifically targeted to T cells. Activating gp130 signaling in T cells in vivo resulted in fatal, early onset, multi-organ autoimmunity in mice that resembled human STAT3 GOF disease. Female mice had more rapid disease progression than male mice. On a cellular level, gp130 signaling induced the activation and effector cell differentiation of T cells, promoted the expansion of T helper type 17 (T H 17) cells, and impaired the activity of regulatory T cells. Transcriptomic profiling of CD4 + and CD8 + T cells from these mice revealed commonly dysregulated genes and a gene signature that, when applied to human transcriptomic data, improved the segregation of patients with transcriptionally diverse STAT3 GOF mutations from healthy controls. The findings demonstrate that increased gp130-STAT3 signaling leads to T H 17-driven autoimmunity that phenotypically resembles human STAT3 GOF disease.

ABSTRACT Objectives Sjögren’s Disease (SjD) is an autoimmune disorder characterized by progressive dysfunction, inflammation and destruction of salivary and lacrimal glands, and by extraglandular manifestations. Its etiology and pathophysiology remain incompletely understood, though a role for autoreactive B cells has been considered key. Here, we investigated the role of effector and regulatory T cells in the pathogenesis of SjD. Methods Histological analysis, RNA-sequencing and flow cytometry were conducted on glands, lungs, eyes and lymphoid tissues of mice with regulatory T cell-specific deletion of stromal interaction proteins (STIM) 1 and 2 ( Stim1/2 Foxp3 ), which play key roles in calcium signaling and T cell function. The pathogenicity of T cells from Stim1/2 Foxp3 mice was investigated through adoptively transfer into lymphopenic host mice. Additionally, single-cell transcriptomic analysis was performed on peripheral blood mononuclear cells (PBMCs) of patients with SjD and control subjects. Results Stim1/2 Foxp3 mice develop a severe SjD-like disorder including salivary gland (SG) and lacrimal gland (LG) inflammation and dysfunction, autoantibodies and extraglandular symptoms. SG inflammation in Stim1/2 Foxp3 mice is characterized by T and B cell infiltration, and transcriptionally by a Th1 immune response that correlates strongly with the dysregulation observed in patients with SjD. Adoptive transfer of effector T cells from Stim1/2 Foxp3 mice demonstrates that the SjD-like disease is driven by interferon (IFN)-γ producing autoreactive CD4 + T cells independently of B cells and autoantiboodies. scRNA-seq analysis identifies increased Th1 responses and attenuated memory Treg function in PBMCs of patients with SjD. Conclusions We report a more accurate mouse model of SjD while providing evidence for a critical role of Treg cells and IFN-γ producing Th1 cells in the pathogenesis of SjD, which may be effective targets for therapy.