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Mitochondrial Arginase-2 deletion enhances the function of in vivo activated murine CD8+ T cells

ABSTRACT: As sufficient extracellular arginine is crucial for T cell function, depletion of extracellular arginine by elevated Arginase 1 (Arg1) activity has emerged as a hallmark immunosuppressive mechanism. However, the potential cell-autonomous roles of arginases in T cells have remained unexplored. Here we show that the arginase isoform expressed by T cells, the mitochondrial Arginase 2 (Arg2), is a cell-intrinsic regulator of CD8+ T cell activity. Both germ-line Arg2 deletion and adoptive transfer of Arg2-/- CD8+ T cells significantly reduced tumor growth in preclinical cancer models by enhancing CD8+ T cell activation, effector function and persistence. Transcriptomic, proteomic and high-dimensional flow cytometry characterization revealed a CD8+ T cell-intrinsic role of Arg2 in modulating T cell activation, anti-tumor cytoxicity and memory formation, independently of extracellular arginine availability. Furthermore, specific deletion of Arg2 in CD8+ T cells strongly synergized with PD-1 blockade for the control of tumor growth and animal survival. These observations coupled with the finding that pharmacologic arginase inhibition accelerates activation of ex vivo human T cells unveil Arg2 as a new therapeutic target for T cell-based cancer therapies.

ORGANISM(S): Mus musculus

PROVIDER: GSE139811 | GEO | 2019/11/02

REPOSITORIES: GEO

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Project description:Most available knowledge on fungal arginine metabolism is derived from studies on Saccharomyces cerevisiae, in which arginine catabolism is initiated by releasing urea via the arginase reaction. Orthologs of the S. cerevisiae genes encoding the first three enzymes in the arginase pathway were cloned from Kluyveromyces lactis and shown to functionally complement the corresponding deletion in S. cerevisiae. Surprisingly, deletion of the single K. lactis arginase gene KlCAR1 did not completely abolish growth on arginine as nitrogen source. Growth rate of mutant strongly increased during serial transfer in shake-flask cultures. A combination of RNAseq-based transcriptome analysis and 13C-15N-based flux analysis was used to elucidate the arginase-independent pathway. Isotopic 13C15N-enrichment in ?-aminobutyrate revealed succinate as the entry point in the TCA cycle of the alternative pathway. Transcript analysis combined with enzyme activity measurements indicated increased expression in the Klcar1? mutant of a guanidinobutyrase (EC.3.5.3.7), an enzyme not previously demonstrated in fungi. Expression of the K. lactis KLLA0F27995g (renamed KlGBU1) encoding guanidinobutyrase enabled S. cerevisiae to use guanidinobutyrate as sole nitrogen source and its deletion in K. lactis almost completely abolish growth on this nitrogen source. Phylogenetic analysis suggests that this enzyme activity is widespread in fungi. The goal of the present study was to characterize arginine catabolism in K. lactis. To this end, CAR1, CAR2 and PRO3 orthologs in K. lactis were identified and functionally analysed by deletion, expression in S. cerevisiae and enzyme activity assays. Since deletion of the arginase gene in K. lactis was found not to completely abolish growth on arginine as a sole nitrogen source, the alternative pathway for arginine catabolism operating in this yeast was studied by a combination of transcriptome analysis, 13C and 15N isotope-based flux analysis and enzyme activity assays in cell extracts. To investigate arginine metabolism in the arginase-negative K. lactis strain, strains GG1632 (Klku80? KlCAR1 reference strain) and IMS0367 (Klcar1? Arg+) were grown in aerobic bioreactor batch cultures on glucose chemically defined medium with arginine as sole nitrogen source. RNA sequencing of samples taken during the exponential phase of growth on glucose-arginine media of the reference strain G1631 and the arginase less strain IMS0367 were compared resulting in the characterization of a new function.

Project description:A favourable immunotherapeutic strategy in the treatment of chronic inflammatory disease, is to dampen the pro-inflammatory macrophage response and upregulate the anti-inflammatory macrophage response. Previous studies have shown that Arginase-2 (Arg2), a mitochondrial enzyme, is a key regulator of the macrophage anti-inflammatory response with an essential role in IL-10 signalling. Here we show that IL-10 in the presence of LPS increased Arg2 expression in human macrophages and peripheral blood mononuclear cells. Target site blockers (TSBs) (locked nucleic acid antisense oligonucleotides) specifically designed to target the 3’ UTR of Arg2 messenger RNA were used to inhibit binding of specific microRNAs thus enhancing Arg2 expression. Eleven Arg2-TSBs were screened and the TSB targeting miR-155 (TSB-155) and the TSB targeting miR-3202 (TSB-3202) were found to increase Arg2 expression in human macrophages resulting in decreased gene expression and cytokine production of TNF-α and CCL2. In addition, following TSB-3202 stimulation, there were statistically significant increases in the ‘M2-like’ macrophage marker, CD206; and CD16, associated with an IL-10 response, and a decrease in the ‘M1-like’ macrophage marker, HLA-DR, indicating a shift in the macrophage phenotype. Proteomic analysis demonstrated that multiple pro-inflammatory responsive proteins including Signal Transducer and Activator of Transcription 1 (STAT-1), Toll-like receptors, Signalling Lymphocytic Activation Molecule F7 (SLAMF7) and Interferon Induced Protein with Tetratricopeptide Repeats 3 (IFIT3), were downregulated by TSB-155 and TSB-3202 while Sequestomsome-1 (SQSTM1) was increased after treatment. In silico analysis of significantly dysregulated proteins predicted that TSB-3202 supressed several upstream pro-inflammatory regulators including STAT-1 and Interferon α2 (IFNA2) while enhancing anti-inflammatory associated interleukin 1 receptor antagonist (IL1RN) and STAT-3. Proteomic data was validated by confirming increased levels of SQSTM1, decreased levels of phosphoylated-STAT-1 and STAT-1, and downregulation of Ifit3 and Slamf7 by TSB treatment. In conclusion, upregulation of Arg2 protein by TSBs inhibits several pro-inflammatory signalling proteins resulting in reduced pro-inflammatory cytokine secretion, reduced ‘M1-like’ marker expression and enhanced ‘M2-like’ macrophage marker expression. Arg2 is a promising novel therapeutic target to modulate inflammatory signalling in macrophages.

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Mitochondrial Arginase-2 deletion enhances the function of in vivo activated murine CD8+ T cells

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