A mouse model of Salmonella typhi infection.

Salmonella spp. are gram-negative flagellated bacteria that can cause food- and waterborne gastroenteritis and typhoid fever in humans. We now report that flagellin from Salmonella spp. is recognized in mouse intestine by Toll-like receptor 11 (TLR11). Absence of TLR11 renders mice more susceptible to infection by S. Typhimurium, with increased dissemination of the bacteria and enhanced lethality. Unlike S. Typhimurium, S. Typhi, a human obligatory pathogen that causes typhoid fever, is normally unable to infect mice. TLR11 is expressed in mice, but not in humans, and remarkably, we find that tlr11(-/-) mice are efficiently infected with orally administered S. Typhi. We also find that tlr11(-/-) mice can be immunized against S. Typhi. Therefore, tlr11(-/-) mice represent a small-animal model for the study of the immune response to S. Typhi and for the development of vaccines against this important human pathogen.

PDK1 Is Required for Maintenance of CD4+ Foxp3+ Regulatory T Cell Function.

Regulatory T (Treg) cells have an essential role in maintaining immune homeostasis, in part by suppressing effector T cell functions. Phosphoinositide-dependent kinase 1 (PDK1) is a pleiotropic kinase that acts as a key effector downstream of PI3K in many cell types. In T cells, PDK1 has been shown to be critical for activation of NF-κB and AKT signaling upon TCR ligation and is therefore essential for effector T cell activation, proliferation, and cytokine production. Using Treg cell-specific conditional deletion, we now demonstrate that PDK1 is also essential for Treg cell suppressive activity in vivo. Ablation of Pdk1 specifically in Treg cells led to systemic, lethal, scurfy-like inflammation in mice. Genome-wide analysis confirmed that PDK1 is essential for the regulation of key Treg cell signature gene expression and, further, suggested that PDK1 acts primarily to control Treg cell gene expression through regulation of the canonical NF-κB pathway. Consistent with these results, the scurfy-like phenotype of mice lacking PDK1 in Treg cells was rescued by enforced activation of NF-κB downstream of PDK1. Therefore, PDK1-mediated activation of the NF-κB signaling pathway is essential for regulation of Treg cell signature gene expression and suppressor function.

Entry inhibition of hepatitis B virus using cyclosporin O derivatives with peptoid side chain incorporation.

Hepatitis B virus (HBV) infection is a serious worldwide health problem causing liver cirrhosis and hepatocellular carcinoma. The development of novel therapeutics targeting distinct steps of the HBV life cycle and combination therapy with approved drugs (i.e., nucleot(s)ides, interferon-α) are considered effective strategies for curing HBV. Among these strategies is the development of entry inhibitors that interfere with the host entry step of HBV to prevent viral infection and transmission. Herein, we generated a novel library of cyclosporin O (CsO) derivatives that incorporate peptoid side chains. Twenty-two CsO derivatives were evaluated for membrane permeability, cytotoxicity, and in vitro HBV entry inhibitory activity. The lead compound (i.e., compound 21) showed the greatest potency in the in vitro HBV entry inhibition assay (IC50 = 0.36 ± 0.01 µM) with minimal cytotoxicity. Our peptide-peptoid hybrid CsO scaffold can readily expand chemical diversity and is applicable for screening various targets requiring macrocyclic chemical entities.

The kinase PDK1 integrates T cell antigen receptor and CD28 coreceptor signaling to induce NF-kappaB and activate T cells.

In addition to ligation of the T cell antigen receptor (TCR), activation of the CD28 coreceptor by the costimulatory molecule B7 is required for induction of the transcription factor NF-kappaB and robust T cell activation, although the contribution of CD28 to this process remains incompletely understood. We show here that phosphoinositide-dependent kinase 1 (PDK1) is essential for integrating the TCR and CD28 signals. After we deleted PDK1 from T cells, TCR-CD28 signals were unable to induce activation of NF-kappaB or phosphorylation of protein kinase C-theta, although T cell survival and pathways dependent on the kinases p38 and Jnk or the transcription factor NFAT were unaffected. CD28 facilitated NF-kappaB activation by regulating recruitment and phosphorylation of PDK1, which are necessary for efficient binding of PDK1 to protein kinase C-theta and the adaptor CARMA1 and thus for NF-kappaB induction.

The Functional Roles and Applications of Immunoglobulins in Neurodegenerative Disease.

Natural autoantibodies, immunoglobulins (Igs) that target self-proteins, are common in the plasma of healthy individuals; some of the autoantibodies play pathogenic roles in systemic or tissue-specific autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus. Recently, the field of autoantibody-associated diseases has expanded to encompass neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD), with related studies examining the functions of Igs in the central nervous system (CNS). Recent evidence suggests that Igs have various effects in the CNS; these effects are associated with the prevention of neurodegeneration, as well as induction. Here, we summarize the functional roles of Igs with respect to neurodegenerative disease (AD and PD), focusing on the target antigens and effector cell types. In addition, we review the current knowledge about the roles of these antibodies as diagnostic markers and immunotherapies.

Oxidatively Modified Protein-Disulfide Isomerase-Associated 3 Promotes Dyskerin Pseudouridine Synthase 1-Mediated Malignancy and Survival of Hepatocellular Carcinoma Cells.

Dyskerin pseudouridine synthase 1 (DKC1) is a conserved gene encoding the RNA-binding protein dyskerin, which is an essential component of the telomerase holoenzyme. DKC1 up-regulation is frequently observed in many different human cancers including hepatocellular carcinoma (HCC); however, its regulatory mechanisms remain unclear. Thus, we investigated the regulatory mechanism of DKC1 in HCC progression. We found that protein-disulfide isomerase-associated 3 (PDIA3) interacted with the DKC1 regulatory DNA in HCC cells but not in HCC cells with elevated reactive oxygen species (ROS) levels, using liquid chromatographic-tandem mass spectrometric analysis after isolating the DKC1 regulatory region binding proteins. PDIA3 repressed DKC1 expression in HCC cells by recognizing the G-quadruplex DNA at the DKC1 location. However, oxidative modification of PDIA3 induced by ROS redistributed this protein into the cytosolic regions, which stimulated DKC1 expression. We also identified Met338 in PDIA3 as the oxidatively modified residue and validated the effect of oxidative modification using an ectopic expression system, a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 knock-in system, and a xenograft mouse model. We observed that oxidatively modified PDIA3 promoted DKC1-mediated malignancy and survival of HCC cells in vitro and in vivo. HCC tissues showed a positive association with ROS, cytoplasmic PDIA3, and nuclear DKC1 levels. HCC patients with high PDIA3 protein and DKC1 mRNA levels also displayed reduced recurrence-free survival rates. Cumulatively, the results showed that cytoplasmic PDIA3 activity could be essential in raising DKC1 expression in HCC progression and predicting poor prognoses in HCC patients. Conclusion: Our study indicates that the elevated ROS levels in HCC modulate cytoplasmic PDIA3 levels, resulting in HCC cell survival through DKC1 up-regulation.

T regulatory cells maintain intestinal homeostasis by suppressing γδ T cells.

Immune tolerance against enteric commensal bacteria is important for preventing intestinal inflammation. Deletion of phosphoinositide-dependent protein kinase 1 (Pdk1) in T cells via Cd4-Cre induced chronic inflammation of the intestine despite the importance of PDK1 in T cell activation. Analysis of colonic intraepithelial lymphocytes of PDK1-deficient mice revealed markedly increased CD8α(+) T cell receptor (TCR)γδ(+) T cells, including an interleukin-17 (IL-17)-expressing population. TCRγδ(+) T cells were responsible for the inflammatory colitis as shown by the fact that deletion of Tcrd abolished spontaneous colitis in the PDK1-deficient mice. This dysregulation of intestinal TCRγδ(+) T cells was attributable to a reduction in the number and functional capacity of PDK1-deficient T regulatory (Treg) cells. Adoptive transfer of wild-type Treg cells abrogated the spontaneous activation and proliferation of intestinal TCRγδ(+) T cells observed in PDK1-deficient mice and prevented the development of colitis. Therefore, suppression of intestinal TCRγδ(+) T cells by Treg cells maintains enteric immune tolerance.

Epigenetic regulation of Kcna3-encoding Kv1.3 potassium channel by cereblon contributes to regulation of CD4+ T-cell activation.

The role of cereblon (CRBN) in T cells is not well understood. We generated mice with a deletion in Crbn and found cereblon to be an important antagonist of T-cell activation. In mice lacking CRBN, CD4(+) T cells show increased activation and IL-2 production on T-cell receptor stimulation, ultimately resulting in increased potassium flux and calcium-mediated signaling. CRBN restricts T-cell activation via epigenetic modification of Kcna3, which encodes the Kv1.3 potassium channel required for robust calcium influx in T cells. CRBN binds directly to conserved DNA elements adjacent to Kcna3 via a previously uncharacterized DNA-binding motif. Consequently, in the absence of CRBN, the expression of Kv1.3 is derepressed, resulting in increased Kv1.3 expression, potassium flux, and CD4(+) T-cell hyperactivation. In addition, experimental autoimmune encephalomyelitis in T-cell-specific Crbn-deficient mice was exacerbated by increased T-cell activation via Kv1.3. Thus, CRBN limits CD4(+) T-cell activation via epigenetic regulation of Kv1.3 expression.

Nuclear factor-kappaB modulates regulatory T cell development by directly regulating expression of Foxp3 transcription factor.

Naturally derived regulatory T (Treg) cells are characterized by stable expression of the transcription factor Foxp3 and characteristic epigenetic imprinting at the Foxp3 gene locus. Here, we found that enhancing nuclear factor (NF)-kappaB activity via a constitutive active inhibitor of kappaB kinase beta (IKKbeta) transgene in T cells led to increased number of Foxp3(+) cells in the thymus and can rescue Foxp3 expression in thymocytes deficient in other pleiotropic signaling molecules. Enhancing the signal strength of the NF-kappaB pathway also induced Foxp3 expression in otherwise conventionally selected T cells. NF-kappaB directly promoted the transcription of Foxp3, and upon T cell receptor (TCR) stimulation, c-Rel, a NF-kappaB family member, bound to Foxp3 enhancer region, which is specifically demethylated in natural Treg cells. Hence, NF-kappaB signaling pathway is a key regulator of Foxp3 expression during natural Treg cell development.

Immunomodulatory Function of Myeloid-Derived Suppressor Cells during B Cell-Mediated Immune Responses.

Myeloid-derived suppressor cells (MDSCs) play roles in immune regulation during neoplastic and non-neoplastic inflammatory responses. This immune regulatory function is directed mainly toward T cells. However, MDSCs also regulate other cell populations, including B cells, during inflammatory responses. Indeed, B cells are essential for antibody-mediated immune responses. MDSCs regulate B cell immune responses directly via expression of effector molecules and indirectly by controlling other immune regulatory cells. B cell-mediated immune responses are a major component of the overall immune response; thus, MDSCs play a prominent role in their regulation. Here, we review the current knowledge about MDSC-mediated regulation of B cell responses.

Characterization of Multiple Cytokine Combinations and TGF-ß on Differentiation and Functions of Myeloid-Derived Suppressor Cells.

Myeloid-derived suppressor cells (MDSCs) regulate T cell immunity, and this population is a new therapeutic target for immune regulation. A previous study showed that transforming growth factor-ß (TGF-ß) is involved in controlling MDSC differentiation and immunoregulatory function in vivo. However, the direct effect of TGF-ß on MDSCs with various cytokines has not previously been tested. Thus, we examined the effect of various cytokine combinations with TGF-ß on MDSCs derived from bone marrow cells. The data show that different cytokine combinations affect the differentiation and immunosuppressive functions of MDSCs in different ways. In the presence of TGF-ß, interleukin-6 (IL-6) was the most potent enhancer of MDSC function, whereas granulocyte colony-stimulating factors (G-CSF) was the most potent in the absence of TGF-ß. In addition, IL-4 maintained MDSCs in an immature state with an increased expression of arginase 1 (Arg1). However, regardless of the cytokine combinations, TGF-ß increased expansion of the monocytic MDSC (Mo-MDSC) population, expression of immunosuppressive molecules by MDSCs, and the ability of MDSCs to suppress CD4⁺ T cell proliferation. Thus, although different cytokine combinations affected the MDSCs in different ways, TGF-ß directly affects monocytic-MDSCs (Mo-MDSCs) expansion and MDSCs functions.

Discovery and structure-activity relationship studies of quinolinone derivatives as potent IL-2 suppressive agents.

The quinolinone skeleton has been utilized to develop various mechanism-based immune modulators. However, the effects of quinolinone derivatives on the release of T cell-associated interleukin-2 (IL-2) have not been established. In this study, a series of novel quinolinone derivatives was synthesized, and their immunosuppressive activity was evaluated by measuring suppression of IL-2 release from activated Jurkat T cells. Optimizing the three side chains around the quinolinone skeleton revealed the most active compound: 11l. This compound exhibits potent inhibitory activity toward IL-2 release in both 12-o-tetradecanoylphorbol-13-acetate (PMA)/A23187 (ionomycin) (IC50=80±10nM) and anti-CD3/CD28-stimulated Jurkat T cells (83% inhibition at 10µM) without cytotoxic effects. Further investigation into the underlying mechanism of 11l indicated the suppression of NF-κB and nuclear factor of activated T cells (NFAT) promoter activities in Jurkat T cells.

Arhgef16, a novel Elmo1 binding partner, promotes clearance of apoptotic cells via RhoG-dependent Rac1 activation.

Elmo is an evolutionarily conserved mammalian ortholog of Caenorhabditis elegans CED-12 with proposed roles during the removal of apoptotic cells, cell migration, neurite outgrowth, and myoblast fusion (Katoh and Negishi (2003) [1], Park and Tosello (2007) [2], Grimsley et al. (2004) [3], Hamoud et al. (2014) [4]). Elmo mediates these cellular processes by interacting with various proteins located in the plasma membrane, cytoplasm and nucleus, and by modulating their activities although it has no intrinsic catalytic activity (Park and Tosello (2007) [2], Hamoud et al. (2014) [4], Li et al. (2013) [5], Margaron, Fradet and Cote (2013) [6], and Mauldin et al. (2013)[7]). Because there are a limited number of proteins known to interact with Elmo, we performed a yeast two-hybrid screen using Elmo1 as bait to identify Elmo1-interacting proteins and to evaluate their mode of regulation. Arhgef16 was one of the proteins identified through the screen and subsequent analyses revealed that Arhgef16 interacted with Elmo1 in mammalian cells as well. Expression of Arhgef16 in phagocytes promoted engulfment of apoptotic cells, and engulfment mediated by Arhgef16 increased synergistically in the presence of Elmo1 but was abrogated in the absence of Elmo1. In addition, Arhgef16-mediated removal of apoptotic cells was dependent on RhoG, but independent of Dock1. Taken together, this study suggests that the newly identified Elmo1-interacting protein, Arhgef16, functions synergistically with Elmo1 to promote clearance of apoptotic cells in a RhoG-dependent and Dock1-independent manner.

Transition from heterotypic to homotypic PDK1 homodimerization is essential for TCR-mediated NF-κB activation.

Strong NF-κB activation requires ligation of both the CD28 coreceptor and TCR. Phosphoinositide-dependent kinase 1 (PDK1) acts as a scaffold by binding both protein kinase Cθ (PKCθ) and CARMA1, and is therefore essential for signaling to NF-κB. In this article, we demonstrate the importance of PDK1 Thr(513) phosphorylation in regulating the intermolecular organization of PDK1 homodimers. Thr(513) is directly involved in heterotypic PDK1 homodimer formation, in which binding is mediated through the pleckstrin homology (PH) and kinase domains. Upon activation, phosphorylated Thr(513) instead mediates homotypic intermolecular binding through the PH domains. Consequently, cell-permeable peptides with a Thr(513) to Ile derivative (protein transduction domain [PTD]-PDK1-Thr(513)-Ile) bound the kinase domain, whereas a Thr(513)-to-Asp peptide (PTD-PDK1-Thr(513)-Asp) bound the PH domain. PTD-PDK1-Thr(513)-Ile blocked binding between PDK1 and PKCθ, phosphorylation of PKCθ Thr(538), and activation of both NF-κB and AKT. In contrast, PTD-PDK1- Thr(513)-Asp selectively inhibited binding between PDK1 and CARMA1, and blocked TCR/CD28-induced NF-κB activation. Therefore, Thr(513) phosphorylation regulates a critical intermolecular switch governing PDK1 homodimer structure and the capacity to interact with downstream signaling pathway components. Given the pleiotropic functions of PDK1, these data may open the door to the development of immunosuppressive therapies that selectively target the PDK1 to NF-κB pathway in T cell activation.

The E3 ligase Mind bomb-1 (Mib1) modulates Delta-Notch signaling to control neurogenesis and gliogenesis in the developing spinal cord.

The Notch signaling pathway is essential for neuronal and glial specification during CNS development. Mind bomb-1 (Mib1) is an E3 ubiquitin ligase that ubiquitinates and promotes the endocytosis of Notch ligands. Although Mib1 is essential for transmitting the Notch signal, it is still unclear whether it is a primary regulator of Notch ligand activity in the developing spinal cord. In Mib1 conditional knock-out mice, we observed depletion of spinal progenitors, premature differentiation of neurons, and unbalanced specification of V2 interneurons, all of which mimic the conventional Notch phenotype. In agreement with this, the reduction of progenitors in the absence of Mib1 led to a loss of both astrocytes and oligodendrocytes. Late removal of Mib1 using a drug-inducible system suppressed glial differentiation, suggesting that Mib1 continues to play a role in the formation of late progenitors mainly designated for gliogenesis. Finally, misexpression of Mib1 or Mib1 deletion mutants revealed that the ring domain of Mib1 is required for the specification of V2 interneurons in the chick neural tube. Together, these findings suggest that Mib1 is a major component of the signal-sending cells required to provide Notch ligand activity for specifying neurons and glia in the spinal cord.

Notch1 is an important mediator for enhancing of B-cell activation and antibody secretion by Notch ligand.

The roles of Notch1 and Notch2 in T-cell function have been well studied, but the functional roles of Notch in B cells have not been extensively investigated, except for Notch2 involvement in peripheral marginal zone B-cell differentiation. This study examined the roles of Notch1 in murine primary B cells. During B-cell activation by B-cell receptor ligation, Notch1 was up-regulated while Notch2 was not. In addition, Notch1 up-regulation itself did not contribute to the further activation of B cells, but the Notch ligand was important for Notch1-mediated further B-cell activation. Moreover, Notch1 deficiency significantly decreased B-cell activation and antibody secretion under the presence of Notch ligand. These data suggest that Notch1 is an important mediator for enhancing B-cell activation and antibody secretion by Notch ligand.

Peroxisome-localized hepatitis Bx protein increases the invasion property of hepatocellular carcinoma cells.

HBx acts as a multifunctional regulator that modulates various cellular responses, which can lead to development and progression of hepatocellular carcinoma (HCC). Here, we show that the HBx protein is also localized to peroxisomes, and this increases cellular reactive oxygen species (ROS) to levels that are higher than when HBx is localized to other organelles. The elevated ROS strongly activated nuclear factor (NF)-κB. In addition, the peroxisome-localized HBx increased the expressions of matrix metalloproteinases and decreased the expression of E-cadherin, which increased the invasive ability of HCC cells. Thus, a specific distribution of HBx to peroxisomes may contribute to HCC progression by increasing the invasive ability of HCC cells through elevation of the cellular ROS level.

A new compound, phomaherbarine A, induces cytolytic reactivation in epstein-barr virus-positive B cell lines.

Epstein-Barr virus (EBV), the first virus found to induce cancer in humans, has been frequently detected in various types of B cell lymphomas. During its latent phase, EBV expresses a limited set of proteins crucial for its persistence. Induction of the lytic phase of EBV has shown promise in the treatment of EBV-associated malignancies. The present study assessed the ability of phomaherbarine A, a novel compound derived from the endophytic fungus Phoma herbarum DBE-M1, to stimulate lytic replication of EBV in B95-8 cells. Phomaherbarine A was found to efficiently initiate the expression of both early and late EBV lytic genes in B95-8 cells, with this initiation being further heightened by the addition of phorbol myristate acetate and sodium butyrate. Moreover, phomaherbarine A demonstrated notable cytotoxicity against the EBV-associated B cell lymphoma cell lines B95-8 and Raji. Mechanistically, phomaherbarine A induces apoptosis in these cells through the activation of caspase-3/7. When combined with ganciclovir, phomaherbarine A does not interfere with the reduction of viral replication by ganciclovir and sustains its apoptosis induction. In conclusion, these findings indicate that phomaherbarine A may be a promising candidate for therapeutic intervention in patients with EBV-associated B cell lymphomas.

Alzheimer's disease risk associated with changes in Epstein-Barr virus nuclear antigen 1-specific epitope targeting antibody levels.

BACKGROUND: Alzheimer's disease (AD) is a neurodegenerative disorder influenced by age, sex, genetic factors, immune alterations, and infections. Multiple lines of evidence suggest that changes in antibody response are linked to AD pathology. METHODS: To elucidate the mechanisms underlying AD development, we investigated antibodies that target autoimmune epitopes using high-resolution epitope microarrays. Our study compared two groups: individuals with AD (n = 19) and non-demented (ND) controls (n = 19). To validate the results, we measured antibody levels in plasma samples from AD patients (n = 96), mild cognitive impairment (MCI; n = 91), and ND controls (n = 97). To further explore the invlovement of EBV, we performed epitope masking immunofluorescence microscopy analysis and tests to induce lytic replication using the B95-8 cell line. RESULTS: In this study, we analyzed high-resolution epitope-specific serum antibody levels in AD, revealing significant disparities in antibodies targeting multiple epitopes between the AD and control groups. Particularly noteworthy was the significant down-regulation of antibody (anti-DG#29) targeting an epitope of Epstein-Barr virus nuclear antigen 1 (EBNA1). This down-regulation increased AD risk in female patients (odds ratio up to 6.6), but not in male patients. Our investigation further revealed that the down-regulation of the antibody (anti-DG#29) is associated with EBV reactivation in AD, as indicated by the analysis of EBV VCA IgG or IgM levels. Additionally, our data demonstrated that the epitope region on EBNA1 for the antibody is hidden during the EBV lytic reactivation of B95-8 cells. CONCLUSION: Our findings suggest a potential relationship of EBV in the development of AD in female. Moreover, we propose that antibodies targeting the epitope (DG#29) of EBNA1 could serve as valuable indicators of AD risk in female.

Decoy peptides targeted to protein phosphatase 1 inhibit dephosphorylation of phospholamban in cardiomyocytes.

Cardiac sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a) plays a crucial role in Ca(2+) handling in cardiomyocytes. Phospholamban (PLB) is an endogenous inhibitor of SERCA2a and its inhibitory activity is enhanced via dephosphorylation by protein phosphatase 1 (PP1). Therefore, the inhibition of PP1-mediated dephosphorylation of PLB might be an efficient strategy for the restoration of reduced SERCA2a activity in failing hearts. We sought to develop decoy peptides that would mimic phosphorylated PLB and thus competitively inhibit the PP1-mediated dephosphorylation of endogenous PLB. The phosphorylation sites Ser16 and Thr17 are located within the flexible loop region (amino acids 14-22) of PLB. We therefore synthesized a 9-mer peptide derived from this region (ΨPLB-wt) and two pseudo-phosphorylated peptides where Ser16 was replaced with Glu (ΨPLB-SE) or Thr17 was replaced with Glu (ΨPLB-TE). These peptides were coupled to the cell-permeable peptide TAT to facilitate cellular uptake. Treatment of adult rat cardiomyocytes with ΨPLB-SE or ΨPLB-TE, but not with ΨPLB-wt, significantly elevated the phosphorylation levels of PLB at Ser16 and Thr17. This increased phosphorylation of PLB correlated with an increase in contractile parameters in vitro. Furthermore, the perfusion of isolated rat hearts with ΨPLB-SE or ΨPLB-TE, but not with ΨPLB-wt, significantly improved left ventricular developed pressure that had been previously impaired by ischemia. These data indicate that ΨPLB-SE and ΨPLB-TE efficiently prevented dephosphorylation of PLB by serving as decoys for PP1. Therefore, these peptides may provide an effective modality to regulate SERCA2a activity in failing hearts.