Glutamine has been implicated as an immunomodulatory nutrient, but how glutamine uptake is mediated during T-cell activation is poorly understood. We have shown that naïve T-cell activation is coupled with rapid glutamine uptake, which depended on the amino acid transporter ASCT2. ASCT2 deficiency impaired the induction of T helper-1 (Th1) and Th17 cells and attenuated inflammatory T-cell responses in mouse models of immunity and autoimmunity. Mechanistically, ASCT2 was required for T cell receptor (TCR)-stimulated activation of the metabolic kinase mTORC1. We have further shown that TCR-stimulated glutamine uptake and mTORC1 activation also required a TCR signaling complex composed of the scaffold protein CARMA1, the adaptor molecule BCL10, and the paracaspase MALT1. This function was independent of IKK kinase, a major downstream target of the CARMA1 complex. These findings highlight a mechanism of T-cell activation involving ASCT2-dependent integration of the TCR signal and a metabolic signaling pathway.

T-cell activation is subject to tight regulation to avoid inappropriate responses against self-antigens. Here we show that genetic deficiency in an ubiquitin ligase, Peli1, causes hyper activation of T cells and renders T cells refractory to suppression by T regulatory cells and transforming growth factor (TGF)-β. As a result, Peli1 knockout mice spontaneously develop autoimmunity, characterized by multiorgan inflammation and autoantibody production. Peli1 deficiency results in accumulation of nuclear c-Rel, a member of the NF-κB family of transcription factors with pivotal roles in T-cell activation. Peli1 negatively regulates c-Rel by mediating its K48 ubiquitination. These results identify Peli1 as a critical factor in the maintenance of peripheral T-cell tolerance and reveal a novel mechanism of c-Rel regulation.

Microglia are crucial for the pathogenesis of multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis (EAE). Here, we show that the E3 ubiquitin ligase Peli1 is abundantly expressed in microglia and serves as a pivotal mediator of microglial activation during the course of EAE induction. Peli1 mediates the induction of chemokines and proinflammatory cytokines in microglia and, thereby, promotes recruitment of T cells into the central nervous system. Peli1-deficient mice are refractory to EAE induction despite their competent production of Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use: http://www.nature.com/authors/editorial_policies/license.html#terms HHS Public Access

Deubiquitinases (DUBs) represent a new class of drug targets, although the physiological function of only few DUBs has been characterized. Here we identified the DUB USP15 as a crucial negative regulator of T cell activation. USP15 stabilized an E3 ubiquitin ligase, MDM2, which in turn negatively regulated T cell activation by targeting the degradation of the transcription factor NFATc2. USP15 deficiency promoted T cell activation in vitro and enhanced T cell responses to bacterial infection and tumor challenge in vivo. USP15 also stabilized MDM2 in cancer cells and regulated p53 function and cancer cell survival. Our results suggest that inhibition of USP15 may both induce tumor cell apoptosis and boost antitumor T cell responses.

Purpose Aurora A kinase (AAK) is overexpressed in aggressive lymphomas and can correlate with more histologically aggressive forms of disease. We therefore designed a phase II study of alisertib, a selective AAK inhibitor, in patients with relapsed and refractory aggressive non-Hodgkin lymphomas. Patients and Methods Patients age ≥ 18 years were eligible if they had relapsed or refractory diffuse large B-cell lymphoma (DLBCL), mantle-cell lymphoma (MCL), transformed follicular lymphoma, Burkitt's lymphoma, or noncutaneous T-cell lymphoma. Alisertib was administered orally at 50 mg twice daily for 7 days in 21-day cycles. Results We enrolled 48 patients. Histologies included DLBCL (n = 21), MCL (n = 13), peripheral T-cell lymphoma (n = 8), transformed follicular lymphoma (n = 5), and Burkitt's (n = 1). Most common grade 3 to 4 adverse events were neutropenia (63%), leukopenia (54%), anemia (35%), thrombocytopenia (33%), stomatitis (15%), febrile neutropenia (13%), and fatigue (6%). Four deaths during the study were attributed to progressive non-Hodgkin lymphoma (n = 2), treatment-related sepsis (n = 1), and unknown cause (n = 1). The overall response rate was 27%, including responses in three of 21 patients with DLBCL, three of 13 with MCL, one of one with Burkitt's lymphoma, two of five with transformed follicular lymphoma, and four of eight with noncutaneous T-cell lymphoma. The alisertib steady-state trough concentration (n = 25) revealed the expected pharmacokinetic variability, with a trend for higher incidence of adverse event–related dose reductions at higher trough concentrations. Analysis for AAK gene amplification and total AAK protein revealed no differences between histologies or correlation with clinical response. Conclusion The novel AAK inhibitor alisertib seems clinically active in both B- and T-cell aggressive lymphomas. On the basis of these results, confirmatory single-agent and combination studies have been initiated.

Maintenance of immune homeostasis requires regulatory T (Treg) cells. Here we show that Treg-specific ablation of Ubc13, a lysine 63-specific ubiquitin-conjugating enzyme, caused aberrant T cell activation and autoimmunity. Although Ubc13 deficiency did not affect Treg cell survival or Foxp3 expression, it impaired the in vivo suppressive function of Treg cells and rendered them sensitive for acquiring T helper (TH) 1- and TH17-like effector T cell phenotypes. This function of Ubc13 involved its downstream target, IκB kinase (IKK). The Ubc13-IKK signaling axis controlled the expression specific Treg effector molecules, including interleukin 10 (IL-10) and SOCS1. Collectively, these findings suggest that the Ubc13-IKK signaling axis regulates the molecular program that maintains Treg function and prevents Treg cells from acquiring inflammatory phenotypes.

Development of an immune or autoimmune response involves T-cell activation in lymphoid organs and subsequent migration to peripheral tissues. Here we show that T-cell-specific ablation of the kinase TBK1 promotes T-cell activation but causes retention of effector T cells in the draining lymph node in a neuroinflammatory autoimmunity model, experimental autoimmune encephalomyelitis (EAE). At older ages, the T-cell-conditional TBK1-knockout mice also spontaneously accumulate T cells with activated phenotype. TBK1 controls the activation of AKT and its downstream kinase mTORC1 by a mechanism involving TBK1-stimulated AKT ubiquitination and degradation. The deregulated AKT-mTORC1 signalling in turn contributes to enhanced T-cell activation and impaired effector T-cell egress from draining lymph nodes. Treatment of mice with a small-molecule inhibitor of TBK1 inhibits EAE induction. These results suggest a role for TBK1 in regulating T-cell migration and establish TBK1 as a regulator of the AKT-mTORC1 signalling axis.

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