The immune response to RNA suppresses nucleic acid synthesis by limiting ribose 5-phosphate.

During infection viruses hijack host cell metabolism to promote their replication. Here, analysis of metabolite alterations in macrophages exposed to poly I:C recognises that the antiviral effector Protein Kinase RNA-activated (PKR) suppresses glucose breakdown within the pentose phosphate pathway (PPP). This pathway runs parallel to central glycolysis and is critical to producing NADPH and pentose precursors for nucleotides. Changes in metabolite levels between wild-type and PKR-ablated macrophages show that PKR controls the generation of ribose 5-phosphate, in a manner distinct from its established function in gene expression but dependent on its kinase activity. PKR phosphorylates and inhibits the Ribose 5-Phosphate Isomerase A (RPIA), thereby preventing interconversion of ribulose- to ribose 5-phosphate. This activity preserves redox control but decreases production of ribose 5-phosphate for nucleotide biosynthesis. Accordingly, the PKR-mediated immune response to RNA suppresses nucleic acid production. In line, pharmacological targeting of the PPP during infection decreases the replication of the Herpes simplex virus. These results identify an immune response-mediated control of host cell metabolism and suggest targeting the RPIA as a potential innovative antiviral treatment.

Retracted: FoxP3 acts as a cotranscription factor with STAT3 in tumor-induced regulatory T cells.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the authors. This study provided an explanation for why loss of FoxP3 in inducible regulatory T cells results in reduced expression of interleukin (IL)-10 despite the absence of FoxP3 binding sites in the IL-10 promoter. STAT3 binding sites do exist in the promoter, and evidence for a direct molecular interaction between FoxP3 and STAT3 proteins was provided as an explanation of the effect of loss of FoxP3. As supporting evidence, we reported modeling of a structural interaction between these two transcription factors in Figure 4D. As the N-terminal region of FoxP3, which consists of the Exon-2 region, had not been solved at structural resolution, we mistakenly used what we deduced to be a FoxP3 related transcription factor, NFAT, in the modeling. The model depicted in Figure 4D therefore did not represent a putative interaction between FoxP3 and STAT3 as labeled, but rather a putative interaction between NFAT and STAT3. Given the incorrect labeling of Figure 4D, the lack of documentation in the paper describing exactly how the modeling was performed, the lack of evidence shown in the paper for the choice of NFAT as the modeling partner, and the limited supporting evidence for a cooperative interaction between FoxP3 and STAT3, the editors have concluded with the corresponding author that the appropriate course of action is to retract the paper. We apologize for any confusion and inconvenience caused to readers.

Insulin's other life: an autoantigen in type 1 diabetes.

One hundred years ago, Frederick Banting, John Macleod, Charles Best and James Collip, and their collaborators, discovered insulin. This discovery paved the way to saving countless lives and ushered in the "Insulin Era." Since the discovery of insulin, we have made enormous strides in understanding its role in metabolism and diabetes. Insulin has played a dramatic role in the treatment of people with diabetes; particularly type 1 diabetes (T1D). Insulin replacement is a life-saving therapy for people with T1D and some with type 2 diabetes. T1D is an autoimmune disease caused by the T-cell-mediated destruction of the pancreatic insulin-producing beta cells that leads to a primary insulin deficiency. It has become increasingly clear that insulin, and its precursors preproinsulin (PPI) and proinsulin (PI), can play another role-not as a hormone but as an autoantigen in T1D. Here we review the role played by the products of the INS gene as autoantigens in people with T1D. From many elegant animal studies, it is clear that T-cell responses to insulin, PPI and PI are essential for T1D to develop. Here we review the evidence that autoimmune responses to insulin and PPI arise in people with T1D and discuss the recently described neoepitopes derived from the products of the insulin gene. Finally, we look forward to new approaches to deliver epitopes derived from PPI, PI and insulin that may allow immune tolerance to pancreatic beta cells to be restored in people with, or at risk of, T1D.

GPR81, a Cell-Surface Receptor for Lactate, Regulates Intestinal Homeostasis and Protects Mice from Experimental Colitis.

At mucosal sites such as the intestine, the immune system launches robust immunity against invading pathogens while maintaining a state of tolerance to commensal flora and ingested food Ags. The molecular mechanisms underlying this phenomenon remain poorly understood. In this study, we report that signaling by GPR81, a receptor for lactate, in colonic dendritic cells and macrophages plays an important role in suppressing colonic inflammation and restoring colonic homeostasis. Genetic deletion of GPR81 in mice led to increased Th1/Th17 cell differentiation and reduced regulatory T cell differentiation, resulting in enhanced susceptibility to colonic inflammation. This was due to increased production of proinflammatory cytokines (IL-6, IL-1ß, and TNF-α) and decreased expression of immune regulatory factors (IL-10, retinoic acid, and IDO) by intestinal APCs lacking GPR81. Consistent with these findings, pharmacological activation of GPR81 decreased inflammatory cytokine expression and ameliorated colonic inflammation. Taken together, these findings identify a new and important role for the GPR81 signaling pathway in regulating immune tolerance and colonic inflammation. Thus, manipulation of the GPR81 pathway could provide novel opportunities for enhancing regulatory responses and treating colonic inflammation.

WITHDRAWN: Curcumin shifts RAS-induced pro-proliferative MEK/ERK-signaling toward pro-apoptotic p38MAPK/JNK1-signaling, triggering p53 activation and apoptosis.

This article has been withdrawn by the authors. A mistake was made during the preparation of Fig 1C, NKE panel. The Western blot data shown for p-ERK1/2 and actin are not from this set, but rather a similar set of data from a different experiment. The authors apologize to the readers.

Providence of the CD25+ KIR+ CD127- FOXP3- CD8+ T-cell subset determines the dynamics of tumor immune surveillance.

CD8+ T-regulatory (Treg) cells are emerging as crucial components of immune system. Previous studies have reported the presence of FOXP3+ CD8+ Treg cells, similar to CD4+ Tregs, in cancer patients which produce high levels of the immunosuppressive cytokines, IL10 and TGFß. At an early stage of tumor development, we have identified a subset of FOXP3- CD8+ CD25+ KIR+ CD127- Treg-like cells, which are IFNγ+ . However, this early-induced CD8+ CD25+ CD127- T-cell subset is certainly distinct from the IFNγ+ CD8+ T-effector cells. These CD8+ CD25+ CD127- T cells express other FOXP3- CD8+ Treg cell signature markers, and can selectively suppress autoreactive HLA-E+ TFH cells as well as tumor-induced CD4+ Treg cells. In contrast to FOXP3+ CD8+ Tregs, this subset does not inhibit effector T-cell proliferation or their functions as they are HLA-E- . Adoptive transfer of this early-CD8+ Treg-like subset restrained tumor growth and inhibited CD4+ Treg generation that impedes the immune surveillance and impairs cancer immunotherapy. At the late stage of tumor development, when CD4+ Treg cells dominate the tumor-microenvironment, CD4+ Tregs mediate the clonal deletion of these tumor-suppressive FOXP3- IFNγ+ CD8+ CD25+ CD127- T cells and ensure tumor immune evasion. Our findings suggest that at an early stage of the tumor, this tumor-induced IFNγ-producing FOXP3- CD8+ CD25+ CD127- T-cell subset can potentiate immune surveillance by targeting HLA-E-restricted CD4+ Treg cells while leaving the effector T-cell population unaffected. Hence, manipulating their profile can open up a new avenue in cancer immunotherapy.

Cross-talk between endoplasmic reticulum (ER) stress and the MEK/ERK pathway potentiates apoptosis in human triple negative breast carcinoma cells: role of a dihydropyrimidone, nifetepimine.

Triple negative breast cancers (TNBC) are among the most aggressive and therapy-resistant breast tumors and currently possess almost no molecular targets for therapeutic options in this horizon. In the present study we discerned the molecular mechanisms of potential interaction between the endoplasmic reticulum (ER) stress response and the MEK/ERK pathway in inducing apoptosis in TNBC cells. Here we observed that induction of ER stress alone was not sufficient to trigger significant apoptosis but simultaneous inhibition of the MEK/ERK pathway enhanced ER stress-induced apoptosis via a caspase-dependent mechanism. Our study also demonstrated nifetepimine, a dihydropyrimidone derivative as a potent anti-cancer agent in TNBC cells. Nifetepimine down-regulated the MEK/ERK pathway in MDAMB-231 and MDAMB-468 cells and resulted in blockage of ER stress-mediated GRP78 up-regulation. Detailed mechanistic studies also revealed that nifetepimine by down-regulating pERK expression also declined the promoter binding activity of TFII-I to the GRP78 promoter and in turn regulated GRP78 transcription. Studies further extended to in vivo Swiss albino and SCID mice models also revalidated the anti-carcinogenic property of nifetepimine. Thus our findings cumulatively suggest that nifetepimine couples two distinct signaling pathways to induce the apoptotic death cascade in TNBC cells and raises the possibility for the use of nifetepimine as a potent anti-cancer agent with strong immune-restoring properties for therapeutic intervention for this group of cancer bearers.

MEK inhibition prevents tumour-shed transforming growth factor-ß-induced T-regulatory cell augmentation in tumour milieu.

Tumour progression is associated with immune-suppressive conditions that facilitate the escape of tumour cells from the regimen of immune cells, subsequently paralysing the host defence mechanisms. Induction of CD4(+)  CD25(+)  FoxP3(+) T regulatory (Treg) cells has been implicated in the tumour immune escape mechanism, although the novel anti-cancer treatment strategies targeting Treg cells remain unknown. The focus of this study is to define the interaction between tumour and immune system, i.e. how immune tolerance starts and gradually leads to the induction of adaptive Treg cells in the tumour microenvironment. Our study identified hyperactivated mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) -signalling as a potential target for reversing Treg cell augmentation in breast cancer patients. In more mechanistic detail, pharmacological inhibitors of MEK/ERK signalling inhibited transforming growth factor-ß (TGF-ß) production in tumour cells that essentially blocked TGF-ß-SMAD3/SMAD4-mediated induction of CD25/interleukin-2 receptor α on CD4(+) T-cell surface. As a result high-affinity binding of interleukin-2 on those cells was prohibited, causing lack of Janus kinase 1 (JAK1)/JAK3-mediated signal transducer and activator of transcription 3 (STAT3)/STAT5 activation required for FoxP3 expression. Finally, for a more radical approach towards a safe MEK inhibitor, we validate the potential of multi-kinase inhibitor curcumin, especially the nano-curcumin made out of pure curcumin with greater bioavailability; in repealing tumour-shed TGF-ß-induced Treg cell augmentation.

The novel immunotherapeutic molecule T11TS modulates glioma-induced changes of key components of the immunological synapse in favor of T cell activation and glioma abrogation.

T-cell-mediated immune responses are typically low in conditions of malignant glioma which has been known to cause marked immunesuppression and dysregulate major T-cell signaling molecules. Thus, T-cell-based immunotherapies are currently in vogue in the treatment of malignant glioma. The novel glycopeptide, T11TS/S-LFA-3/S-CD58 has previously been shown by our group to be highly efficacious in glioma abrogation in in vivo and in vitro conditions. This glycopeptide ligands to the costimulatory CD2 molecule on T-cells, causing profound immune stimulation leading to glioma abrogation, suggesting probable involvement of T11TS in modulation of the T-cell signaling pathway. The present study offers a multi-targeted approach towards repair of some of the key components of the immunological synapse at the T-cell-APC interface and is therefore the first of its kind to offer a holistic model of restoration of immunological synapse components so as to trigger T-cells towards activation against glioma. The study thus indicates that the totally dysregulated molecular events at the immunological synapse in glioma are restored back to normal levels with the administration of T11TS, which finally culminates in glioma abrogation. The present study thus delineates an important T-cell signaling approach whereby T11TS acts as an anti-neoplastic agent, thus helping to chart out newer avenues in the fight against gliomas.

Nifetepimine, a dihydropyrimidone, ensures CD4+ T cell survival in a tumor microenvironment by maneuvering sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA).

Multiple mechanisms have been proposed by which tumors induce T cell apoptosis to circumvent tumor immune-surveillance. Although sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) have long been known to regulate intracellular Ca(2+) homeostasis, few studies have examined the role of SERCA in processes of T lymphocyte survival and activation. In this context it remains largely unexplored as to how tumors jeopardize SERCA function to disable T cell-mediated anti-tumor immunity. Here, we show that human CD4(+) T cells in the presence of tumor conditions manifested an up-regulation of SERCA3 expression that resulted in development of endoplasmic reticulum stress leading to CD4(+) T cell apoptosis. Prostaglandin E(2) produced by the tumor cell plays a critical role in up-regulating SERCA3 by enhancing the binding of its transcription factor Sp1. Gene manipulation and pharmacological approaches further established that an increase in SERCA expression also resulted in subsequent inhibition of PKCα and -θ and retention of NFκB in the cytosol; however, down-modulation of SERCA3 expression by a dihydropyrimidone derivative, ethyl-4-(3-nitro)-phenyl-6-methyl-2-oxo-1,2,3,4-tetrahydropyrimidine-5 carboxylate (nifetepimine), protected the CD4(+) T cells from tumor-induced apoptosis. In fact, nifetepimine-mediated restoration of PKC activity resulted in nuclear translocation of p65NFκB, thereby ensuring its survival. Studies further undertaken in a tumor-bearing mice model revalidated the immunoprotective role of nifetepimine. Our present study thus strongly suggests that imbalance in cellular calcium homeostasis is an important factor leading to CD4(+) T cell death during cancer and holds promise that nifetepimine may have the potential to be used as an immunorestoring agent in cancer bearers.

Targeting RET to induce medullary thyroid cancer cell apoptosis: an antagonistic interplay between PI3K/Akt and p38MAPK/caspase-8 pathways.

Mutations in REarranged during Transfection (RET) receptor tyrosine, followed by the oncogenic activation of RET kinase is responsible for the development of medullary thyroid carcinoma (MTC) that responds poorly to conventional chemotherapy. Targeting RET, therefore, might be useful in tailoring surveillance of MTC patients. Here we showed that theaflavins, the bioactive components of black tea, successfully induced apoptosis in human MTC cell line, TT, by inversely modulating two molecular pathways: (i) stalling PI3K/Akt/Bad pathway that resulted in mitochondrial transmembrane potential (MTP) loss, cytochrome-c release and activation of the executioner caspases-9 and -3, and (ii) upholding p38MAPK/caspase-8/caspase-3 pathway via inhibition of Ras/Raf/ERK. Over-expression of either constitutively active myristoylated-Akt-cDNA (Myr-Akt-cDNA) or dominant-negative-caspase-8-cDNA (Dn-caspase-8-cDNA) partially blocked theaflavin-induced apoptosis, while co-transfection of Myr-Akt-cDNA and Dn-caspase-8-cDNA completely eradicated the effect of theaflavins thereby negating the possibility of existence of other pathways. A search for the upstream signaling revealed that theaflavin-induced disruption of lipid raft caused interference in anchorage of RET in lipid raft that in turn stalled phosphorylation of Ras and PI3Kinase. In such anti-survival cellular micro-environment, pro-apoptotic signals were triggered to culminate into programmed death of MTC cell. These findings not only unveil a hitherto unexplained mechanism underlying theaflavin-induced MTC death, but also validate RET as a promising and potential target for MTC therapy.

Glutamine deamidation does not increase the immunogenicity of C-peptide in people with type 1 diabetes.

Type 1 diabetes (T1D) is a T-cell mediated autoimmune disease in which the insulin-producing beta cells are destroyed. While it is clear that full-length C-peptide, derived from proinsulin, is a major antigen in human T1D it is not clear how and why C-peptide becomes a target of the autoimmune CD4+ T-cell responses in T1D. Neoepitopes formed by the conversion of glutamine (Q) residues to glutamic acid (E) by deamidation are central to the immune pathogenesis of coeliac disease and have been implicated in autoimmune responses in T1D. Here, we asked if the immunogenicity of full-length C-peptide, which comprises four glutamine residues, was enhanced by deamidation, which we mimicked by substituting glutamic acid for glutamine residue. First, we used a panel of 18 well characterized CD4+ T-cell lines specific for epitopes derived from human C-peptide. In all cases, when the substitution fell within the cognate epitope the response was diminished, or in a few cases unchanged. In contrast, when the substitution fell outside the epitope recognized by the TCR responses were unchanged or slightly augmented. Second, we compared CD4+ T-cell proliferation responses, against deamidated and unmodified C-peptide, in the peripheral blood of people with or without T1D using the CFSE-based proliferation assay. While, as reported previously, responses were detected to unmodified C-peptide, no deamidated C-peptide was consistently more stimulatory than native C-peptide. Overall responses were weaker to deamidated C-peptide compared to unmodified C-peptide. Hence, we conclude that deamidated C-peptide does not play a role in beta-cell autoimmunity in people with T1D.

Pathogenic Mutations in the C2A Domain of Dysferlin form Amyloid that Activates the Inflammasome.

Limb-Girdle Muscular Dystrophy Type-2B/2R is caused by mutations in the dysferlin gene ( DYSF ). This disease has two known pathogenic missense mutations that occur within dysferlin's C2A domain, namely C2A W52R and C2A V67D . Yet, the etiological rationale to explain the disease linkage for these two mutations is still unclear. In this study, we have presented evidence from biophysical, computational, and immunological experiments which suggest that these missense mutations interfere with dysferlin's ability to repair cells. The failure of C2A W52R and C2A V67D to initiate membrane repair arises from their propensity to form stable amyloid. The misfolding of the C2A domain caused by either mutation exposes ß-strands, which are predicted to nucleate classical amyloid structures. When dysferlin C2A amyloid is formed, it triggers the NLRP3 inflammasome, leading to the secretion of inflammatory cytokines, including IL-1ß. The present study suggests that the muscle dysfunction and inflammation evident in Limb-Girdle Muscular Dystrophy types-2B/2R, specifically in cases involving C2A W52R and C2A V67D , as well as other C2 domain mutations with considerable hydrophobic core involvement, may be attributed to this mechanism.

Curcumin enhances the efficacy of chemotherapy by tailoring p65NFκB-p300 cross-talk in favor of p53-p300 in breast cancer.

Breast cancer cells often develop multiple mechanisms of drug resistance during tumor progression, which is the major reason for the failure of breast cancer therapy. High constitutive activation of NFκB has been found in different cancers, creating an environment conducive for chemotherapeutic resistance. Here we report that doxorubicin-induced SMAR1-dependent transcriptional repression and SMAR1-independent degradation of IkBα resulted in nuclear translocation of p65NFκB and its association with p300 histone acetylase and subsequent transcription of Bcl-2 to impart protective response in drug-resistant cells. Consistently SMAR1-silenced drug-resistant cells exhibited IkBα-mediated inhibition of p65NFκB and induction of p53-dependent apoptosis. Interestingly, curcumin pretreatment of drug-resistant cells alleviated SMAR1-mediated p65NFκB activation and hence restored doxorubicin sensitivity. Under such anti-survival condition, induction of p53-p300 cross-talk enhanced the transcriptional activity of p53 and intrinsic death cascade. Importantly, promyelocyte leukemia-mediated SMAR1 sequestration that relieved the repression of apoptosis-inducing genes was indispensable for such chemo-sensitizing ability of curcumin. A simultaneous decrease in drug-induced systemic toxicity by curcumin might also have enhanced the efficacy of doxorubicin by improving the intrinsic defense machineries of the tumor-bearer. Overall, the findings of this preclinical study clearly demonstrate the effectiveness of curcumin to combat doxorubicin-resistance. We, therefore, suggest curcumin as a potent chemo-sensitizer to improve the therapeutic index of this widely used anti-cancer drug. Taken together, these results suggest that curcumin can be developed into an adjuvant chemotherapeutic drug.

Identifying New Hybrid Insulin Peptides (HIPs) in Type 1 Diabetes.

In 2016 Delong et al. discovered a new type of neoepitope formed by the fusion of two unrelated peptide fragments. Remarkably these neoepitopes, called hybrid insulin peptides, or HIPs, are recognized by pathogenic CD4+ T cells in the NOD mouse and human pancreatic islet-infiltrating T cells in people with type 1 diabetes. Current data implicates CD4+ T-cell responses to HIPs in the immune pathogenesis of human T1D. Because of their role in the immune pathogenesis of human T1D it is important to identify new HIPs that are recognized by CD4+ T cells in people at risk of, or with, T1D. A detailed knowledge of T1D-associated HIPs will allow HIPs to be used in assays to monitor changes in T cell mediated beta-cell autoimmunity. They will also provide new targets for antigen-specific therapies for T1D. However, because HIPs are formed by the fusion of two unrelated peptides there are an enormous number of potential HIPs which makes it technically challenging to identify them. Here we review the discovery of HIPs, how they form and discuss approaches to identifying new HIPs relevant to the immune pathogenesis of human type 1 diabetes.

T cell receptor recognition of hybrid insulin peptides bound to HLA-DQ8.

HLA-DQ8, a genetic risk factor in type I diabetes (T1D), presents hybrid insulin peptides (HIPs) to autoreactive CD4+ T cells. The abundance of spliced peptides binding to HLA-DQ8 and how they are subsequently recognised by the autoreactive T cell repertoire is unknown. Here we report, the HIP (GQVELGGGNAVEVLK), derived from splicing of insulin and islet amyloid polypeptides, generates a preferred peptide-binding motif for HLA-DQ8. HLA-DQ8-HIP tetramer+ T cells from the peripheral blood of a T1D patient are characterised by repeated TRBV5 usage, which matches the TCR bias of CD4+ T cells reactive to the HIP peptide isolated from the pancreatic islets of a patient with T1D. The crystal structure of three TRBV5+ TCR-HLA-DQ8-HIP complexes shows that the TRBV5-encoded TCR ß-chain forms a common landing pad on the HLA-DQ8 molecule. The N- and C-termini of the HIP is recognised predominantly by the TCR α-chain and TCR ß-chain, respectively, in all three TCR ternary complexes. Accordingly, TRBV5 + TCR recognition of HIP peptides might occur via a 'polarised' mechanism, whereby each chain within the αßTCR heterodimer recognises distinct origins of the spliced peptide presented by HLA-DQ8.

Anticancer potential of animal venoms and toxins.

Anticancer drug development from natural resources are ventured throughout the world. Animal venoms and toxins a potential bio resource and a therapeutic tool were known to man for centuries through folk and traditional knowledge. The biodiversity of venoms and toxins made it a unique source of leads and structural templates from which new therapeutic agents may be developed. Venoms of several animal species (snake, scorpion, toad, frog etc) and their active components (protein and non protein toxins, peptides, enzymes, etc) have shown therapeutic potential against cancer. In the present review, the anticancer potential of venoms and toxins from snakes, scorpions, toads and frogs has been discussed. Some of these molecules are in the clinical trials and may find their way towards anticancer drug development in the near future. The implications of combination therapy of natural products in cancer have been discussed.

The lactate receptor GPR81 promotes breast cancer growth via a paracrine mechanism involving antigen-presenting cells in the tumor microenvironment.

GPR81 is a G-protein-coupled receptor for lactate, which is upregulated in breast cancer and plays an autocrine role to promote tumor growth by tumor cell-derived lactate. Here we asked whether lactate has any paracrine role via activation of GPR81 in cells present in tumor microenvironment to help tumor growth. First, we showed that deletion of Gpr81 suppresses breast cancer growth in a constitutive breast cancer mouse model (MMTV-PyMT-Tg). We then used a syngeneic transplant model by monitoring tumor growth from a mouse breast cancer cell line (AT-3, Gpr81-negative) implanted in mammary fat pad of wild-type mice and Gpr81-null mice. Tumor growth was suppressed in Gpr81-null mice compared with wild-type mice. There were more tumor-infiltrating T cells and MHCIIhi-immune cells in tumors from Gpr81-null mice compared with tumors from wild-type mice. RNA-seq analysis of tumors indicated involvement of immune cells and antigen presentation in Gpr81-dependent tumor growth. Antigen-presenting dendritic cells expressed Gpr81 and activation of this receptor by lactate suppressed cell-surface presentation of MHCII. Activation of Gpr81 in dendritic cells was associated with decreased cAMP, IL-6 and IL-12. These findings suggest that tumor cell-derived lactate activates GPR81 in dendritic cells and prevents presentation of tumor-specific antigens to other immune cells. This paracrine mechanism is complementary to the recently discovered autocrine mechanism in which lactate induces PD-L1 in tumor cells via activation of GPR81 in tumor cells, thus providing an effective means for tumor cells to evade immune system. As such, blockade of GPR81 signaling could boost cancer immunotherapy.