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    CARD11 is dispensable for homeostatic responses and suppressive activity of peripherally induced FOXP3+ regulatory T cells
    Polichen, A ; Horikawa, K ; Milla, L ; Kofler, J ; Bouillet, P ; Belz, GT ; O'Reilly, LA ; Goodnow, CC ; Strasser, A ; Gray, DHD (WILEY, 2019-09)
    FOXP3+ regulatory T (Treg) cells are essential for immunological tolerance and immune homeostasis. Despite a great deal of interest in modulating their number and function for the treatment of autoimmune disease or cancer, the precise mechanisms that control the homeostasis of Treg cells remain unclear. We report a new ENU-induced mutant mouse, lack of costimulation (loco), with atopic dermatitis and Treg cell deficiency typical of Card11 loss-of-function mutants. Three distinct single nucleotide variants were found in the Card11 introns 2, 10 and 20 that cause the loss of CARD11 expression in these mutant mice. These mutations caused the loss of thymic-derived, Neuropilin-1+ (NRP1+ ) Treg cells in neonatal and adult loco mice; however, residual peripherally induced NRP1- Treg cells remained. These peripherally generated Treg cells could be expanded in vivo by the administration of IL-2:anti-IL-2 complexes, indicating that this key homeostatic signaling axis remained intact in CARD11-deficient Treg cells. Furthermore, these expanded Treg cells could mediate near-normal suppression of activated, conventional CD4+ T cells, suggesting that CARD11 is dispensable for Treg cell function. In addition to shedding light on the requirements for CARD11 in Treg cell homeostasis and function, these data reveal novel noncoding Card11 loss-of-function mutations that impair the expression of this critical immune-regulatory protein.
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    The linear ubiquitin chain assembly complex: a new function in thymic T cell differentiation and regulatory T cell homeostasis
    Teh, C ; Lalaoui, N ; Jain, R ; Policheni, A ; Heinlein, M ; Alvarez-Diaz, S ; Rieser, E ; Deuser, S ; Koay, H-F ; Hu, Y ; Kupresanin, F ; O'Reilly, L ; Godfrey, D ; Smyth, G ; Bouillet, P ; Strasser, A ; Walczak, H ; Silke, J ; Gray, D (WILEY-BLACKWELL, 2016-08)
    The linear ubiquitin chain assembly complex (LUBAC) is essential for innate immunity in mice and humans, yet its role in adaptive immunity is unclear. Here we show that the LUBAC components HOIP, HOIL-1 and SHARPIN have essential roles in late thymocyte differentiation, FOXP3+ regulatory T (Treg)-cell development and Treg cell homeostasis. LUBAC activity is not required to prevent TNF-induced apoptosis or necroptosis but is necessary for the transcriptional programme of the penultimate stage of thymocyte differentiation. Treg cell-specific ablation of HOIP causes severe Treg cell deficiency and lethal immune pathology, revealing an ongoing requirement of LUBAC activity for Treg cell homeostasis. These data reveal stage-specific requirements for LUBAC in coordinating the signals required for T-cell differentiation.
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    MCL-1 is essential for survival but dispensable for metabolic fitness of FOXP3+regulatory T cells
    Teh, CE ; Robbins, AK ; Henstridge, DC ; Dewson, G ; Diepstraten, ST ; Kelly, G ; Febbraio, MA ; Gabriel, SS ; O'Reilly, LA ; Strasser, A ; Gray, DHD (SPRINGERNATURE, 2020-12)
    FOXP3+ regulatory T (Treg) cells are essential for maintaining immunological tolerance. Given their importance in immune-related diseases, cancer and obesity, there is increasing interest in targeting the Treg cell compartment therapeutically. New pharmacological inhibitors that specifically target the prosurvival protein MCL-1 may provide this opportunity, as Treg cells are particularly reliant upon this protein. However, there are two distinct isoforms of MCL-1; one located at the outer mitochondrial membrane (OMM) that is required to antagonize apoptosis, and another at the inner mitochondrial membrane (IMM) that is reported to maintain IMM structure and metabolism via ATP production during oxidative phosphorylation. We set out to elucidate the relative importance of these distinct biological functions of MCL-1 in Treg cells to assess whether MCL-1 inhibition might impact upon the metabolism of cells able to resist apoptosis. Conditional deletion of Mcl1 in FOXP3+ Treg cells resulted in a lethal multiorgan autoimmunity due to the depletion of the Treg cell compartment. This striking phenotype was completely rescued by concomitant deletion of the apoptotic effector proteins BAK and BAX, indicating that apoptosis plays a pivotal role in the homeostasis of Treg cells. Notably, MCL-1-deficient Treg cells rescued from apoptosis displayed normal metabolic capacity. Moreover, pharmacological inhibition of MCL-1 in Treg cells resistant to apoptosis did not perturb their metabolic function. We conclude that Treg cells require MCL-1 only to antagonize apoptosis and not for metabolism. Therefore, MCL-1 inhibition could be used to manipulate Treg cell survival for clinical benefit without affecting the metabolic fitness of cells resisting apoptosis.
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    Linear ubiquitin chain assembly complex coordinates late thymic T-cell differentiation and regulatory T-cell homeostasis
    Teh, CE ; Lalaoui, N ; Jain, R ; Policheni, AN ; Heinlein, M ; Alvarez-Diaz, S ; Sheridan, JM ; Rieser, E ; Deuser, S ; Darding, M ; Koay, H-F ; Hu, Y ; Kupresanin, F ; O'Reilly, LA ; Godfrey, DI ; Smyth, GK ; Bouillet, P ; Strasser, A ; Walczak, H ; Silke, J ; Gray, DHD (NATURE PUBLISHING GROUP, 2016-11-18)
    The linear ubiquitin chain assembly complex (LUBAC) is essential for innate immunity in mice and humans, yet its role in adaptive immunity is unclear. Here we show that the LUBAC components HOIP, HOIL-1 and SHARPIN have essential roles in late thymocyte differentiation, FOXP3+ regulatory T (Treg)-cell development and Treg cell homeostasis. LUBAC activity is not required to prevent TNF-induced apoptosis or necroptosis but is necessary for the transcriptional programme of the penultimate stage of thymocyte differentiation. Treg cell-specific ablation of HOIP causes severe Treg cell deficiency and lethal immune pathology, revealing an ongoing requirement of LUBAC activity for Treg cell homeostasis. These data reveal stage-specific requirements for LUBAC in coordinating the signals required for T-cell differentiation.