Biomedical subjects

Laurie H Glimcher

Publications and source records attributed to Laurie H Glimcher.

At least 19 recordsLinked to original sources

PubMed2006

T-bet controls pathogenicity of CTLs in the heart by separable effects on migration and effector activity.

CD8+ CTL contribute to the pathogenesis of myocarditis and cardiac allograft rejection. Using a transgenic model of myocarditis, we examined the role of the transcription factor T-bet in the differentiation of pathogenic cardiac Ag-specific CTL. We demonstrate that T-bet-deficient CTL are significantly impaired in their ability to cause disease, despite intact proliferation and activation phenotypes. In the absence of T-bet, there is markedly reduced expression of the chemokine receptor CXCR3, and CXCR3-gene knockout CTL are significantly less pathogenic than control CTL. Retroviral-mediated CXCR3 expression in T-bet-deficient CD8+ T cells reconstitutes their ability to infiltrate but not to damage the heart, establishing that CD8+ T cell pathogenicity is related to T-bet-dependent CXCR3 expression, reduced cytotoxicity, and enhanced regulation. These findings highlight the potential therapeutic benefit of targeting T-bet-regulated gene expression and CXCR3-dependent migration in immune-mediated heart disease.

Animals↗

PubMed2006

Cutting edge: STAT1 and T-bet play distinct roles in determining outcome of visceral leishmaniasis caused by Leishmania donovani.

T-bet and STAT1 regulate IFN-gamma gene transcription in CD4+ T cells, which mediate protection against Leishmania. Here we show that T-bet and STAT1 are required for the induction of an efficient Th1 response during Leishmania donovani infection, but they play distinct roles in determining disease outcome. Both STAT1(-/-) and T-bet(-/-) mice failed to mount a Th1 response, but STAT1(-/-) mice were highly resistant to L. donovani and developed less immunopathology, whereas T-bet(-/-) mice were highly susceptible and eventually developed liver inflammation. Adoptive cell transfer studies showed that RAG2(-/-) recipients receiving STAT1(+/+) or STAT1(-/-) T cells developed comparable liver pathology, but those receiving STAT1(-/-) T cells were significantly more susceptible to infection. These unexpected findings reveal distinct roles for T-bet and STAT1 in mediating host immunity and liver pathology during visceral leishmaniasis.

Animals↗

PubMed2006

Regulation of adult bone mass by the zinc finger adapter protein Schnurri-3.

Genetic mutations that disrupt osteoblast function can result in skeletal dysmorphogenesis or, more rarely, in increased postnatal bone formation. Here we show that Schnurri-3 (Shn3), a mammalian homolog of the Drosophila zinc finger adapter protein Shn, is an essential regulator of adult bone formation. Mice lacking Shn3 display adult-onset osteosclerosis with increased bone mass due to augmented osteoblast activity. Shn3 was found to control protein levels of Runx2, the principal transcriptional regulator of osteoblast differentiation, by promoting its degradation through recruitment of the E3 ubiquitin ligase WWP1 to Runx2. By this means, Runx2-mediated extracellular matrix mineralization was antagonized, revealing an essential role for Shn3 as a central regulator of postnatal bone mass.

Animals↗

PubMed2006

RETRACTED: Proapoptotic BAX and BAK modulate the unfolded protein response by a direct interaction with IRE1alpha.

Accumulation of misfolded protein in the endoplasmic reticulum (ER) triggers an adaptive stress response-termed the unfolded protein response (UPR)-mediated by the ER transmembrane protein kinase and endoribonuclease inositol-requiring enzyme-1alpha (IRE1alpha). We investigated UPR signaling events in mice in the absence of the proapoptotic BCL-2 family members BAX and BAK [double knockout (DKO)]. DKO mice responded abnormally to tunicamycin-induced ER stress in the liver, with extensive tissue damage and decreased expression of the IRE1 substrate X-box-binding protein 1 and its target genes. ER-stressed DKO cells showed deficient IRE1alpha signaling. BAX and BAK formed a protein complex with the cytosolic domain of IRE1alpha that was essential for IRE1alpha activation. Thus, BAX and BAK function at the ER membrane to activate IRE1alpha signaling and to provide a physical link between members of the core apoptotic pathway and the UPR.

Animals↗

PubMed2006

Osteopontin expression is essential for interferon-alpha production by plasmacytoid dendritic cells.

The observation that the T-bet transcription factor allows tissue-specific upregulation of intracellular osteopontin (Opn-i) in plasmacytoid dendritic cells (pDCs) suggests that Opn might contribute to the expression of interferon-alpha (IFN-alpha) in those cells. Here we show that Opn deficiency substantially reduced Toll-like receptor 9 (TLR9)-dependent IFN-alpha responses but spared expression of transcription factor NF-kappaB-dependent proinflammatory cytokines. Shortly after TLR9 engagement, colocalization of Opn-i and the adaptor molecule MyD88 was associated with induction of transcription factor IRF7-dependent IFN-alpha gene expression, whereas deficient expression of Opn-i was associated with defective nuclear translocation of IRF7 in pDCs. The importance of the Opn-IFN-alpha pathway was emphasized by its essential involvement in cross-presentation in vitro and in anti-herpes simplex virus 1 IFN-alpha response in vivo. The finding that Opn-i selectively coupled TLR9 signaling to expression of IFN-alpha but not to that of other proinflammatory cytokines provides new molecular insight into the biology of pDCs.

Animals↗

PubMed2006

Transcription factor T-bet regulates inflammatory arthritis through its function in dendritic cells.

The transcription factor T-bet (Tbx21) plays a major role in adaptive immunity and is required for optimal IFN-gamma production by DCs. Here we demonstrate an essential function for T-bet in DCs in controlling inflammatory arthritis. We show that collagen antibody-induced arthritis (CAIA), a model of human RA, is a bipartite disease characterized by an early innate immune system component intact in RAG2 mice and a later adaptive immune system phase. Mice lacking T-bet had markedly reduced joint inflammation at both early and late time points and RAG2T-bet double-deficient mice were essentially resistant to disease. Remarkably, adoptive transfer of T-bet-expressing DCs reconstituted inflammation in a T-bet deficient and T-bet/RAG2-deficient milieu. T-bet regulates the production of proinflammatory cytokine IL-1alpha and chemokines macrophage inflammatory protein-1alpha (MIP-1alpha) and thymus- and activation-related chemokine (TARC) by DCs. Further, T-bet expression in DCs is required for T helper cell activation. We conclude that T-bet plays a vital function in DCs that links innate and adaptive immunity to regulate inflammatory responses. T-bet provides an attractive new target for the development of novel therapeutics for inflammatory arthritis.

Adoptive Transfer↗

PubMed2006

Gout: new insights into an old disease.

Gout is an autoinflammatory disorder associated with deposition of monosodium urate (MSU) crystals in joints and periarticular tissues. Recent advances suggest that the innate immune system may drive the gouty inflammatory response to MSU. These findings prompt questions concerning how the innate immune system recognizes MSU and the identities of the receptors involved. In this issue of the JCI, Chen et al. show that the IL-1 receptor and its signaling protein myeloid differentiation primary response protein 88 (MyD88) but not the "classical" innate immune receptors, TLRs, are central for MSU-induced inflammation (see the related article beginning on page 2262).

Adaptor Proteins, Signal Transducing↗

PubMed2005

XBP-1 is required for biogenesis of cellular secretory machinery of exocrine glands.

The secretory function of cells relies on the capacity of the endoplasmic reticulum (ER) to fold and modify nascent polypeptides and to synthesize phospholipids for the subsequent trafficking of secretory proteins through the ER-Golgi network. We have previously demonstrated that the transcription factor XBP-1 activates the expression of certain ER chaperone genes and initiates ER biogenesis. Here, we have rescued the embryonic lethality of XBP-1 deficient fetuses by targeting an XBP-1 transgene selectively to hepatocytes (XBP-1-/-;LivXBP1). XBP-1-/-;LivXBP1 mice displayed abnormalities exclusively in secretory organs such as exocrine pancreas and salivary gland that led to early postnatal lethality from impaired production of pancreatic digestive enzymes. The ER was poorly developed in pancreatic and salivary gland acinar cells, accompanied by decreased expression of ER chaperone genes. Marked apoptosis of pancreatic acinar cells was observed during embryogenesis. Thus, the absence of XBP-1 results in an imbalance between the cargo load on the ER and its capacity to handle it, leading to the activation of ER stress-mediated proapoptotic pathways. These data lead us to propose that XBP-1 is both necessary and sufficient for the full biogenesis of the secretory machinery in exocrine cells.

Animals↗

PubMed2005

Rapid turnover of unspliced Xbp-1 as a factor that modulates the unfolded protein response.

The mammalian and yeast unfolded protein responses (UPR) share the characteristic of rapid elimination of unspliced Xbp-1 (Xbp-1u) and unspliced Hac1p, respectively. These polypeptides derive from mRNAs, whose splicing is induced upon onset of the UPR, so as to allow synthesis of transcription factors essential for execution of the UPR itself. Whereas in yeast translation of unspliced Hac1p is blocked, mammalian Xbp-1u is synthesized constitutively and eliminated by rapid proteasomal degradation. Here we show that the rate of Xbp-1u degradation approaches its rate of synthesis. The C terminus of XBP-1u ensures its trafficking to the cytoplasm, and is sufficient to impose rapid degradation. Degradation of XBP-1u involves both ubiquitin-dependent and ubiquitin-independent mechanisms, which might explain its unusually rapid turnover. Xbp-1(-/-) mouse embryonic fibroblasts reconstituted with mutants of XBP-1u that show improved stability differentially activate UPR target genes. Unexpectedly, we found that one of the mutants activates transcription of both Xbp-1-specific and non-Xbp-1-dependent UPR targets in response to tunicamycin treatment, even more potently than does wild type Xbp-1. We suggest that the degradation of Xbp-1u is required to prevent uncontrolled activation of the UPR while allowing short dwell times for initiation of this response.

Animals↗

PubMed2005

T-bet-dependent expression of osteopontin contributes to T cell polarization.

The osteopontin (Opn) glycoprotein has been implicated in diverse physiological processes, including vascularization, bone formation, and inflammatory responses. Studies of its role in immune responses has suggested that Opn can set the early stage of type-1 immune (cell-mediated) responses through differential regulation of IL-12 and IL-10 cytokine gene expression in macrophages. Although Opn has been suggested to play a role in the development of type-1 immunity, little is known about control of Opn gene expression. Here, we report that Opn gene expression in activated T cells, but not macrophages, is regulated by T-bet, a transcription factor that controls CD4+ T helper (Th1) cell lineage commitment. We also find that T-bet-dependent expression of Opn in T cells is essential for efficient skewing of CD4+ T and CD8+ T cells toward the Th1 and type 1 CD8+ T cells (Tc1) pathway, respectively. Taken together, these findings begin to delineate the genetic basis of Opn expression in T cells and further clarify the role of Opn in Th and Tc1 development.

Amino Acid Sequence↗

PubMed2005

IL-2 production in developing Th1 cells is regulated by heterodimerization of RelA and T-bet and requires T-bet serine residue 508.

Interleukin (IL)-2 is the predominant cytokine that is produced by naive Th cells in a primary response. It is required for proliferation and differentiation of Th precursor cells into effector cells. Initial high-level IL-2 production is followed by its decline, and the concomitant induction of cytokines that are typical of the differentiated state. Although the factors that are responsible for the early induction of IL-2 are well defined, the mechanisms that are responsible for its down-regulation in later stages of Th development have not been studied as much. Previous work from our laboratory revealed a repressor function for the T-box transcription factor, T-bet, in IL-2 gene transcription. Here, we report that T-bet(S508) is required for the optimal repression of IL-2 production in developing Th1 cells. Phosphorylation of T-bet(S508) by casein kinase I and glycogen synthase kinase-3 kinases accompanies T-bet's interaction with the RelA nuclear factor-kappaB transcription factor. Heterodimerization of T-bet and RelA interferes with the binding of RelA to the IL-2 promoter, and hence, transcriptional activation of the IL-2 gene by RelA.

Animals↗

PubMed2005

Increased susceptibility of mice lacking T-bet to infection with Mycobacterium tuberculosis correlates with increased IL-10 and decreased IFN-gamma production.

A sustained CD4+ Th1-dominated type 1 immune response is required to successfully control Mycobacterium tuberculosis infection. Considerable work has demonstrated that the transcription factor, T-bet, is required for IFN-gamma expression and fundamental to the generation of type 1 immunity in multiple cell types. Mice lacking T-bet are susceptible to virulent M. tuberculosis infection. Susceptibility of T-bet-deficient mice is associated with increased systemic bacterial burden, diminished IFN-gamma production, and the striking accumulation of eosinophilic macrophages and multinucleated giant cells in the lung. Interestingly, T-bet(-/-) mice did not develop a fully polarized Th2 response toward M. tuberculosis, but exhibited selective elevation of IL-10 production. These results indicate that T-bet plays a central role in controlling M. tuberculosis disease progression, in part through the regulation of both IFN-gamma and IL-10.

Animals↗

PubMed2005

Expression of T-bet by CD4 T cells is essential for resistance to Salmonella infection.

Despite the recognized role of the T-bet transcription factor in the differentiation of Th1 cells, T-bet-deficient mice can develop small numbers of IFN-gamma-producing CD4 T cells. Although these are not sufficient to allow normal handling of some pathogens, T-bet-deficient mice do resolve infection with the intracellular pathogen Listeria monocytogenes. In contrast, we report that expression of T-bet is required for resistance to Salmonella infection. T-bet-deficient mice succumbed to infection with attenuated Salmonella and did not generate IFN-gamma-producing CD4 T cells or isotype-switched Salmonella-specific Ab responses. Spleen cells from Salmonella-infected T-bet-deficient mice secreted increased levels of IL-10, but not IL-4, upon in vitro restimulation. A Salmonella-specific TCR transgenic adoptive transfer system was used to further define the involvement of T-bet expression in the development of Salmonella-specific Th1 cells. Wild-type Salmonella-specific CD4 T cells activated in T-bet-deficient recipient mice displayed no defect in clonal expansion, contraction, or IFN-gamma production. In contrast, T-bet-deficient, Salmonella-specific CD4 T cells activated in wild-type recipient mice produced less IFN-gamma and more IL-2 upon in vivo restimulation. Therefore, expression of T-bet by CD4 T cells is required for the development of Salmonella-specific Th1 cells, regulation of IL-10 production, and resistance to Salmonella infection.

Animals↗

PubMed2005

T-bet polymorphisms are associated with asthma and airway hyperresponsiveness.

RATIONALE: T-bet (TBX21 or T-box 21) is a critical regulator of T-helper 1 lineage commitment and IFN-gamma production. Knockout mice lacking T-bet develop airway hyperresponsiveness (AHR) to methacholine, peribronchial eosinophilic and lymphocytic inflammation, and increased type III collagen deposition below the bronchial epithelium basement membrane, reminiscent of both acute and chronic asthma histopathology. Little is known regarding the role of genetic variation surrounding T-bet in the development of human AHR. OBJECTIVES: To assess the relationship between T-bet polymorphisms and asthma-related phenotypes using family-based association. METHODS: Single nucleotide polymorphism discovery was performed by resequencing the T-bet genomic locus in 30 individuals (including 22 patients with asthma). Sixteen variants were genotyped in 580 nuclear families ascertained through offspring with asthma from the Childhood Asthma Management Program clinical trial. Haplotype patterns were determined from this genotype data. Family-based tests of association were performed with asthma, AHR, lung function, total serum immunoglobulin E, and blood eosinophil levels. MAIN RESULTS: We identified 24 variants. Evidence of association was observed between c.-7947 and asthma in white families using both additive (p = 0.02) or dominant models (p = 0.006). c.-7947 and three other variants were also associated with AHR (log-methacholine PC(20), p = 0.02-0.04). Haplotype analysis suggested that an AHR locus is in linkage disequilibrium with variants in the 3'UTR. Evidence of association of AHR with c.-7947, but not with other 3'UTR SNPs, was replicated in an independent cohort of adult males with AHR. CONCLUSIONS: These data suggest that T-bet variation contributes to airway responsiveness in asthma.

Adolescent↗

PubMed2005

The adjuvant activity of CpG DNA requires T-bet expression in dendritic cells.

Treatment with synthetic oligodeoxynucleotides containing CpG motifs (CpG ODNs) is remarkably protective against otherwise lethal infection. Here, we describe an essential role for the transcription factor T-bet in mediating the protective function of CpG ODNs. Loss of T-bet in conventional CD11c(hi) dendritic cells (DCs) and in plasmacytoid DCs impaired production of IFNs. Strikingly, in contrast to Rag2-/- mice, Rag2-/- mice that also lacked T-bet (DKO) could not be rescued from lethal Listeria monocytogenes infection by prior treatment with CpG ODN. Rescue was achieved by adoptive transfer of CD11c(hi) DCs from WT, but not T-bet-/-, CpG ODN-treated donor mice. We conclude that T-bet in DCs is required for the adjuvant activity of CpG ODN in infection, revealing its vital role in innate immunity.

Adoptive Transfer↗

PubMed2005

XBP-1 specifically promotes IgM synthesis and secretion, but is dispensable for degradation of glycoproteins in primary B cells.

Differentiation of B cells into plasma cells requires X-box binding protein-1 (XBP-1). In the absence of XBP-1, B cells develop normally, but very little immunoglobulin is secreted. XBP-1 controls the expression of a large set of genes whose products participate in expansion of the endoplasmic reticulum (ER) and in protein trafficking. We define a new role for XBP-1 in exerting selective translational control over high and sustained levels of immunoglobulin M (IgM) synthesis. XBP-1(-/-) and XBP-1(+/+) primary B cells synthesize IgM at comparable levels at the onset of stimulation with lipopolysaccharide or CpG. However, later there is a profound depression in synthesis of IgM in XBP-1(-/-) B cells, notwithstanding similar levels of micromRNA. In marked contrast, lack of XBP-1 does not affect synthesis and trafficking of other glycoproteins, or of immunoglobulin light chains. Contrary to expectation, degradation of proteins from the ER, using TCRalpha or US11-mediated degradation of class I major histocompatibility complex molecules as substrates, is normal in XBP-1(-/-) B cells. Furthermore, degradation of membrane mu was unaffected by enforced expression of XBP-1. We conclude that in primary B cells, the XBP-1 pathway promotes synthesis and secretion of IgM, but does not seem to be involved in the degradation of ER proteins, including that of mu chains themselves.

Animals↗

PubMed2005

T-bet is required for optimal proinflammatory CD4+ T-cell trafficking.

Inflammatory responses are controlled by T helper 1 (Th1) lymphocytes. An important function of this polarity is the ability of T cells to traffick appropriately in vivo. This differential trafficking is dependent upon the binding of P-selectin glycoprotein ligand-1 to P- and E-selectin on inflamed endothelium as well as the expression of specific chemokine receptors. Here we show that in the absence of T-box expressed in T cells (T-bet), selective migration of T cells in vivo is completely abrogated and that T-bet regulates the binding of CD4(+) T cells to P-selectin. T-bet is also required for the expression of the chemokine receptor CXCR3. Thus, T-bet controls Th1-cell migration to inflammatory sites, which has fundamental consequences for the control of immunologic disease.

Animals↗

PubMed2005

Asthmatic changes in mice lacking T-bet are mediated by IL-13.

Mice with a targeted deletion of the T-bet gene exhibit spontaneous airway hyperresponsiveness (AHR), airway inflammation, enhanced recovery of T(h)2 cytokines from bronchoalveolar lavage fluid, sub-epithelial collagen deposition and myofibroblast transformation. Here we analyze the mechanisms responsible for the chronic airway remodeling observed in these mice. CD4+ T cells isolated from the lung of T-bet-deficient mice were spontaneously activated CD44(high)CD69(high) memory T cells, with a typical T(h)2 cytokine profile. Neutralization of IL-13 but not IL-4 resulted in amelioration of AHR in airways of mice lacking T-bet. IL-13 blockade also led to reduced eosinophilia and decreased vimentin, transforming growth factor beta (TGF-beta) and alpha smooth muscle actin (alphaSMA) levels. T-bet(-/-) lung fibroblasts proliferated very rapidly and released increased amounts of TGF-beta. Interestingly, neutralization of TGF-beta ameliorated aspects of the chronic airway remodeling phenotype but did not reduce AHR. These data highlight a T-bet-directed function for IL-13 in controlling lung remodeling that is both dependent on and independent of its interaction with TGF-beta in the asthmatic airway.

Actins↗