RESUMO
T cell receptor (TCR) sensitivity to peptide-major histocompatibility complex (MHC) dictates T cell fate. Canonical models of TCR sensitivity cannot be fully explained by transcriptional regulation. In this work, we identify a posttranscriptional regulatory mechanism of TCR sensitivity that guides alternative splicing of TCR signaling transcripts through an evolutionarily ultraconserved poison exon (PE) in the RNA-binding protein (RBP) TRA2ß in mouse and human. TRA2ß-PE splicing, seen during cancer and infection, was required for TCR-induced effector T cell expansion and function. Tra2ß-PE skipping enhanced T cell response to antigen by increasing TCR sensitivity. As antigen levels decreased, Tra2ß-PE reinclusion allowed T cell survival. Finally, we found that TRA2ß-PE was first included in the genome of jawed vertebrates that were capable of TCR gene rearrangements. We propose that TRA2ß-PE splicing acts as a gatekeeper of TCR sensitivity to shape T cell fate.
Assuntos
Processamento Alternativo , Éxons , Receptores de Antígenos de Linfócitos T , Fatores de Processamento de Serina-Arginina , Animais , Humanos , Camundongos , Sobrevivência Celular , Sequência Conservada , Proteínas do Tecido Nervoso/metabolismo , Proteínas do Tecido Nervoso/genética , Receptores de Antígenos de Linfócitos T/metabolismo , Proteínas de Ligação a RNA/metabolismo , Proteínas de Ligação a RNA/genética , Fatores de Processamento de Serina-Arginina/genética , Linfócitos T/imunologia , Linfócitos T/metabolismoRESUMO
The search for dementia treatments, including treatments for neuropsychiatric lupus (NPSLE), has not yet uncovered useful therapeutic targets that mitigate underlying inflammation. Currently, NPSLE's limited treatment options are often accompanied by severe toxicity. Blocking toll-like receptor (TLR) and IL-1 receptor signal transduction by inhibiting interleukin-1 receptor-associated kinase 4 (IRAK4) offers a new pathway for intervention. Using a pre-clinical NPSLE model, we compare lupus-like B6.MRL-Faslpr (MRL) mice with B6.MRL-Faslpr-IRAK4 kinase-dead (MRL-IRAK4-KD) mice, which are were less prone to 'general' lupus-like symptoms. We demonstrate that lupus-prone mice with a mutation in the kinase domain of IRAK4 no longer display typical lupus hallmarks such as splenomegaly, inflammation, production of hormones, and anti-double-stranded (ds)DNA antibody. water maze behavioral testing, which measures contextual associative learning, revealed that mice without functional IRAK4 displayed a recovery in memory acquisition deficits. RNA-seq approach revealed that cytokine and hormone signaling converge on the JAK/STAT pathways in the mouse hippocampus. Ultimately, the targets identified in this work may result in broad clinical value that can fill the significant scientific and therapeutic gaps precluding development of cures for dementia.
Assuntos
Quinases Associadas a Receptores de Interleucina-1 , Vasculite Associada ao Lúpus do Sistema Nervoso Central , Animais , Quinases Associadas a Receptores de Interleucina-1/metabolismo , Quinases Associadas a Receptores de Interleucina-1/genética , Camundongos , Vasculite Associada ao Lúpus do Sistema Nervoso Central/imunologia , Vasculite Associada ao Lúpus do Sistema Nervoso Central/metabolismo , Modelos Animais de Doenças , Feminino , Transdução de SinaisRESUMO
MicroRNA-150 (miR-150) has been shown to play a general role in the immune system, but very little is known about its role on CD4+ T cell responses. During T cell responses against superantigen Staphylococcal Enterotoxin A, miR-150 expression was down-regulated in antigen-specific CD4+ T cells but up-regulated in CD8+ T cells. CD4+ and CD8+ T cell clonal expansion was greater in miR-150-KO mice than in WT mice, but miR-150 selectively repressed IL-2 production in CD4+ T cells. Transcriptome analysis of CD4+ T cells demonstrated that apoptosis and mTOR pathways were highly enriched in the absence of miR-150. Mechanistic studies confirmed that miR-150 promoted apoptosis specifically in antigen-specific CD4+ T cells, but not in bystander CD4+ nor in CD8+ T cells. Furthermore, inhibition of mTOR-linked mitochondrial superoxidedismutase-2 increased apoptosis in miR-150-/- antigen-specific CD4+ T. Thus, miR-150 impacts CD4+ T cell helper activity by attenuating IL-2 production along with clonal expansion, and suppresses superoxidedismutase to promote apoptosis.
Assuntos
Linfócitos T CD4-Positivos , MicroRNAs , Camundongos , Animais , Linfócitos T CD8-Positivos , Interleucina-2/metabolismo , Regulação para Baixo , Sobrevivência Celular , Serina-Treonina Quinases TOR/metabolismo , MicroRNAs/metabolismo , Superóxido Dismutase/metabolismoRESUMO
Boosting T cell activation through costimulation directs defense against cancer and viral infections. Despite multiple studies targeting costimulation in clinical trials, the increased potency and reprogramming of T cells endowed by costimulation is poorly understood. Canonical dogma states that transcription mediates T cell activation. Here, we show that the spliceosome, controlling post-transcriptional alternative splicing and alternative polyadenylation, is the most enriched pathway in T cells after CD134/CD137 costimulation. Costimulation of CD8+ T cells significantly increases expression of 29 RNA-binding proteins while RNA-seq uncovers over 1000 differential alternative splicing and polyadenylation events. Using in vivo mouse and in vitro human models, we demonstrate that RNA-binding protein Tardbp is required for effector cytokine production, CD8+ T cell clonal expansion, and isoform regulation after costimulation. The prospect of immune response optimization through reprogramming of mRNA isoform production offered herein opens new avenues for experimentally and therapeutically tuning the activities of T cells.
Assuntos
Linfócitos T CD8-Positivos , Neoplasias , Animais , Humanos , Ativação Linfocitária , Camundongos , Neoplasias/metabolismo , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismoRESUMO
Nicotinamide (NAM) shapes T cell responses but its precise molecular mechanism of action remains elusive. Here, we show that NAM impairs naive T cell effector transition but also effector T cells themselves. Although aerobic glycolysis is a hallmark of activated T cells, CD8+ T cells exposed to NAM displayed enhanced glycolysis, yet producing significantly less IFNγ. Mechanistically, NAM reduced mTORC1 activity independently of NAD+ metabolism, decreasing IFNγ translation and regulating T cell transcriptional factors critical to effector/memory fate. Finally, the role of NAM in a biomedically relevant model of lung injury was tested. Specifically, a NAM-supplemented diet reduced systemic IL-2, antigen-specific T cell clonal expansion, and effector function after inhalation of Staphylococcus aureus enterotoxin A. These findings identify NAM as a potential therapeutic supplement that uncouples glycolysis from effector cytokine production and may be a powerful treatment for diseases associated with T cell hyperactivation.
RESUMO
Our understanding of gene expression has come far since the 'one-gene one-polypeptide' hypothesis proposed by Beadle and Tatum. In this review, we address the gradual recognition that a growing number of polycistronic genes, originally discovered in viruses, are being identified within the mammalian genome, and that these may provide new insights into disease mechanisms and treatment. We carried out a systematic literature review identifying 13 mammalian genes for which there is evidence for polycistronic expression via translation through an internal ribosome entry site (IRES). Although the canonical mechanism of translation initiation has been studied extensively, here we highlight a process of noncanonical translation, IRES-mediated translation, that is a growing source for understanding complex inheritance, the elucidation of disease mechanisms, and the discovery of novel therapeutic targets. Identification of additional polycistronic genes may provide new insights into disease therapy and allow for new discoveries of both translational and disease mechanisms.