Overexpression of AMPKγ2 increases AMPK signaling to augment human T cell metabolism and function

Cellular therapies are currently employed to treat a variety of disease processes. For T cell-based therapies, success often relies on the metabolic fitness of the T cell product, where cells with enhanced metabolic capacity demonstrate improved in vivo efficacy. AMP-activated protein kinase (AMPK) is a cellular energy sensor which combines environmental signals with cellular energy status to enforce efficient and flexible metabolic programming. We hypothesized that increasing AMPK activity in human T cells would augment their oxidative capacity, creating an ideal product for adoptive cellular therapies. Lentiviral transduction of the regulatory AMPKγ2 subunit stably enhanced intrinsic AMPK signaling and promoted mitochondrial respiration with increased basal oxygen consumption rates, higher maximal oxygen consumption rate, and augmented spare respiratory capacity. These changes were accompanied by increased proliferation and inflammatory cytokine production, particularly within restricted glucose environments. Introduction of AMPKγ2 into bulk CD4 T cells decreased RNA expression of canonical Th2 genes, including the cytokines interleukin (IL)-4 and IL-5, while introduction of AMPKγ2 into individual Th subsets universally favored proinflammatory cytokine production and a downregulation of IL-4 production in Th2 cells. When AMPKγ2 was overexpressed in regulatory T cells, both in vitro proliferation and suppressive capacity increased. Together, these data suggest that augmenting intrinsic AMPK signaling via overexpression of AMPKγ2 can improve the expansion and functional potential of human T cells for use in a variety of adoptive cellular therapies.

PD-1 licenses activated Treg for lymphatic migration

Rather than serving as fluid transport conduits, the lymphatic vessels have been proved to be critical portals for immune cell migration. As non-immune cell, the lymphatic endothelial cell (LEC) constitutively express high level of programmed death-1 (PD-1) ligand (PD-L1), known as an immune checkpoint protein. We hypothesized that LECs use PD-L1 to regulate PD-1-expressing immune cells during transendothelial migration (TEM). Activated T cells expressed substantially elevated levels of both PD-1 and PD-L1. For human and mouse Tregs PD-1 was in excess of PD-L1, while effector CD4 T cells (Teffs) expressed PD-L1 in excess of PD-1. PD-1−/− but not PD-L1−/− Tregs had reduced migration and motility compared to WT. Engagement by PD-L1 Fc induced rapid activation of Akt but suppressed classical NFkB-P65 signaling in Tregs. WT LECs constitutively expressed high level of surface PD-L1. PD-L1−/− LEC or lymphatic vessels (LV) had increased adhesion and junction proteins VCAM-1 and zonulin-1, and had more zipper junctions. PD-1 triggered PD-L1 signaling in LEC result in strong PI3K/Akt and NFkB-p65 responses that regulated endothelial structure and enhanced TEM. Similar changes to LEC junctions were observed when PD-1high Tregs migrated across LEC layers, resulting in rapidly induced NFkB-p65 translocation into the LEC nucleus. PD-1-induced PD-L1 signaling decreased VE-cadherin expression, which was restored by blocking ERK and PI3K/Akt. Importantly, PD-1-blockade of intra-tumoral Tregs reduced tumor egress and the detained Tregs converted to IFN-g-producing Th1Tregs. These data demonstrate novel roles for Treg PD-1 and LEC PD-L1 in regulation of lymphatic migration and ultimately Treg suppressive function.

Supported by grants from NIH (2R37AI062765-17A1)

Differential effects of 2-deoxy-D-glucose on in vitro expanded human regulatory T cell subsets

Regulatory T cells (Tregs) are required for the maintenance of immune tolerance and adoptive Treg infusion therapy has become a promising approach to suppress immune responses in diseases such as autoimmunity and transplant rejection. However, one critical challenge of Treg therapy is the requirement of in vitro expansion of functionally stable Tregs while preventing either the contamination of T effector and/or emergence of unstable pathogenic Tregs. Recent studies showing distinct metabolic requirements of T effectors and Tregs suggest that manipulation of cell metabolism may be an attractive strategy to achieve this goal. Here we show that human thymically derived Tregs (tTregs) and in vitro induced Tregs (iTregs) from naive T cells engage glycolysis equivalently upon activation. However, inhibiting glucose metabolism via 2-deoxy-D-glucose (2DG) has distinct effects on each of these subsets. While 2DG treatment at the onset of activation significantly reduced the proliferation and expression of suppressive molecules such as ICOS and CTLA-4 in tTregs, its effect on FOXP3 expression was small. In contrast, 2DG treatment during iTreg induction modestly decreased their proliferation but strongly reduced both ICOS and FOXP3 expression. Importantly, both Treg subsets became insensitive to 2DG after day 3 post activation with little effect on either proliferation or FOXP3 expression while T conventional Th0 cells showed reduced proliferation under the same conditions. Moreover, 2DG treatment at day 3 did not impair the suppressive capabilities of Treg subsets. Collectively, these findings suggest that there is a distinct temporal requirement of glycolysis in each of the activated human Treg subsets and T conventional cells. Furthermore, 2DG treatment at the onset as a strategy to impair contaminating T effector cell proliferation is unfavorable for optimal Treg generation as well.

Minimum Information about T Regulatory Cells: A Step toward Reproducibility and Standardization

Cellular therapies with CD4+ T regulatory cells (Tregs) hold promise of efficacious treatment for the variety of autoimmune and allergic diseases as well as posttransplant complications. Nevertheless, current manufacturing of Tregs as a cellular medicinal product varies between different laboratories, which in turn hampers precise comparisons of the results between the studies performed. While the number of clinical trials testing Tregs is already substantial, it seems to be crucial to provide some standardized characteristics of Treg products in order to minimize the problem. We have previously developed reporting guidelines called minimum information about tolerogenic antigen-presenting cells, which allows the comparison between different preparations of tolerance-inducing antigen-presenting cells. Having this experience, here we describe another minimum information about Tregs (MITREG). It is important to note that MITREG does not dictate how investigators should generate or characterize Tregs, but it does require investigators to report their Treg data in a consistent and transparent manner. We hope this will, therefore, be a useful tool facilitating standardized reporting on the manufacturing of Tregs, either for research purposes or for clinical application. This way MITREG might also be an important step toward more standardized and reproducible testing of the Tregs preparations in clinical applications.

Scaffold protein Disc-Large Homolog 1 is required for T cell receptor-induced activation of regulatory T cell function (121.14)

Foxp3+CD4+CD25high regulatory T cell (Treg) suppression of inflammation depends on T cell receptor (TCR)-mediated NFAT activation with reduced Akt activity. We investigated the role of the scaffold protein Dlgh1 in linking the TCR to this unique signaling outcome. The Treg immunological synapse (IS) recruited 4-fold more Dlgh1 than conventional CD4+ T cell IS. Tregs isolated from patients with active rheumatoid arthritis, or treated with tumor necrosis factor-α, display reduced function and diminished Dlgh1 recruitment to the IS. Furthermore, Dlgh1 silencing abrogated Treg function, impaired NFATc1 activation, reduced PTEN levels and increased Akt activation. Dlgh1 operates independently of the negative feedback pathway mediated by the related adapter protein Carma-1 and thus presents an array of novel targets to selectively manipulate Treg function.

PKC-θ mediates negative feedback on regulatory T cell function (139.1)

T cell receptor (TCR) dependent regulatory T cell (Treg) activity controls effector T cell (Teff) function and is acutely inhibited by tumor necrosis factor (TNF). Protein kinase C-θ (PKC-θ) recruitment to the immunological synapse is required in effector cells to recruit Carma-1 in the pathway to NF-κB activation. Surprisingly, PKC-θ was sequestered away from the Treg immunological synapse. Furthermore, PKC-θ inhibition or suppression by RNAi enhanced Treg function, demonstrating PKC-θ mediated negative feedback. Treg integrate TCR and TNF signals through control of PKC-θ location such that inhibition of PKC-θ protected Treg from inactivation by TNF, restored activity of defective Treg from rheumatoid arthritis patients, and enhanced protection of mice from inflammatory colitis. Treg freed of PKC-θ mediated negative feedback can function in the presence of TNF and thus have therapeutic potential in control of inflammatory diseases.

Role for Msh5 in the regulation of Ig class switch recombination

Ig class switch recombination (CSR) and somatic hypermutation serve to diversify antibody responses and are orchestrated by the activity of activation-induced cytidine deaminase and many proteins involved in DNA repair and genome surveillance. Msh5, a gene encoded in the central MHC class III region, and its obligate heterodimerization partner Msh4 have a critical role in regulating meiotic homologous recombination and have not been implicated in CSR. Here, we show that MRL/lpr mice carrying a congenic H-2(b/b) MHC interval exhibit several abnormalities regarding CSR, including a profound deficiency of IgG3 in most mice and long microhomologies at Ig switch (S) joints. We found that Msh5 is expressed at low levels on the H-2(b) haplotype and, importantly, a similar long S joint microhomology phenotype was observed in both Msh5 and Msh4-null mice. We also present evidence that genetic variation in MSH5 is associated with IgA deficiency and common variable immune deficiency (CVID) in humans. One of the human MSH5 alleles identified contains two nonsynonymous polymorphisms, and the variant protein encoded by this allele shows impaired binding to MSH4. Similar to the mice, Ig S joints from CVID and IgA deficiency patients carrying disease-associated MSH5 alleles show increased donor/acceptor microhomology, involving pentameric DNA repeat sequences and lower mutation rates than controls. Our findings suggest that Msh4/5 heterodimers contribute to CSR and support a model whereby Msh4/5 promotes the resolution of DNA breaks with low or no terminal microhomology by a classical nonhomologous end-joining mechanism while possibly suppressing an alternative microhomology-mediated pathway.

Phosphorylated immunoreceptor signaling motifs (ITAMs) exhibit unique abilities to bind and activate Lyn and Syk tyrosine kinases

Signal transduction by T and B cell Ag receptors and certain receptors for Ig Fc regions (Fc gamma RI, hFc gamma RIIA, Fc gamma RIII, Fc alpha R, and Fc epsilon RI) involves a conserved sequence motif, termed an immunoreceptor tyrosine-based activation motif (ITAM) and found in multiple receptor chains. Phosphorylation of the two ITAM tyrosines is a critical event in signal transduction. To address the function of this phosphorylation, we assessed the ability of nonphosphorylated and biphosphorylated ((p)2ITAM) ITAM peptides to bind and modify the activity of src and syk family kinases in vivo and in vitro. All (p)2ITAMs, but not their nonphosphorylated counterparts, induced extensive protein tyrosine phosphorylation in permeabilized cells. However, the patterns of proteins phosphorylated differed among (p)2ITAMs. This phosphorylation was found to reflect activation of the src family kinase Lyn, but not Syk. In vitro studies using purified Lyn showed that src family kinase activation resulted from a direct interaction with (p)2ITAM. Binding studies demonstrated clear differences in binding specificity of (p)2ITAMs. Most strikingly, Ig alpha (p)2ITAM and TCR-zeta c and CD3 epsilon (p)2ITAMs exhibit inverse binding preferences for src and syk family kinases. Taken together, these findings demonstrate a novel mechanism by which src family tyrosine kinases are activated, and are consistent with the possibility that different ITAMs may preferentially activate distinct signaling pathways as a consequence of distinct effector Src homology 2 domain (SH2) binding preference.

Phosphorylated immunoreceptor signaling motifs (ITAMs) exhibit unique abilities to bind and activate Lyn and Syk tyrosine kinases

Signal transduction by T and B cell Ag receptors and certain receptors for Ig Fc regions (Fc gamma RI, hFc gamma RIIA, Fc gamma RIII, Fc alpha R, and Fc epsilon RI) involves a conserved sequence motif, termed an immunoreceptor tyrosine-based activation motif (ITAM) and found in multiple receptor chains. Phosphorylation of the two ITAM tyrosines is a critical event in signal transduction. To address the function of this phosphorylation, we assessed the ability of nonphosphorylated and biphosphorylated ((p)2ITAM) ITAM peptides to bind and modify the activity of src and syk family kinases in vivo and in vitro. All (p)2ITAMs, but not their nonphosphorylated counterparts, induced extensive protein tyrosine phosphorylation in permeabilized cells. However, the patterns of proteins phosphorylated differed among (p)2ITAMs. This phosphorylation was found to reflect activation of the src family kinase Lyn, but not Syk. In vitro studies using purified Lyn showed that src family kinase activation resulted from a direct interaction with (p)2ITAM. Binding studies demonstrated clear differences in binding specificity of (p)2ITAMs. Most strikingly, Ig alpha (p)2ITAM and TCR-zeta c and CD3 epsilon (p)2ITAMs exhibit inverse binding preferences for src and syk family kinases. Taken together, these findings demonstrate a novel mechanism by which src family tyrosine kinases are activated, and are consistent with the possibility that different ITAMs may preferentially activate distinct signaling pathways as a consequence of distinct effector Src homology 2 domain (SH2) binding preference.