Faculty Bibliography

Macrophages respond to several subcellular products of Mycobacterium tuberculosis (Mtb) through TLR2 or TLR4. However, primary mouse macrophages respond to viable, virulent Mtb by pathways largely independent of MyD88, the common adaptor molecule for TLRs. Using microarrays, quantitative PCR, and ELISA with gene-disrupted macrophages and mice, we now show that viable Mtb elicits the expression of inducible NO synthase, RANTES, IFN-inducible protein 10, immune-responsive gene 1, and many other key genes in macrophages substantially independently of TLR2, TLR4, their combination, or the TLR adaptors Toll-IL-1R domain-containing adapter protein and Toll-IL-1R domain-containing adapter inducing IFN-beta. Mice deficient in both TLR2 and TLR4 handle aerosol infection with viable Mtb as well as congenic controls. Viable Mtb also up-regulates inducible NO synthase, RANTES, IFN-inducible protein 10, and IRG1 in macrophages that lack mannose receptor, complement receptors 3 and 4, type A scavenger receptor, or CD40. These MyD88, TLR2/4-independent transcriptional responses require IFN-alphabetaR and STAT1, but not IFN-gamma. Conversely, those genes whose expression is MyD88 dependent do not depend on IFN-alphabetaR or STAT1. Transcriptional induction of TNF is TLR2/4, MyD88, STAT1, and IFN-alphabetaR independent, but TNF protein release requires the TLR2/4-MyD88 pathway. Thus, macrophages respond transcriptionally to viable Mtb through at least three pathways. TLR2 mediates the responses of a numerically minor set of genes that collectively do not appear to affect the course of infection in mice; regulation of TNF requires TLR2/4 for post-transcriptional control, but not for transcriptional induction; and many responding genes are regulated through an unknown, TLR2/4-independent pathway that may involve IFN-alphabetaR and STAT1

Signal transducers and activators of transcription (STAT) regulate a plethora of cytokine responses. Recently, aberrant signaling by STAT proteins has been demonstrated to play important roles in the pathogenesis of many neoplasms, by promoting cell cycle progression and survival, stimulating angiogenesis, and impairing immunological responses and tumor surveillance. We have developed genetic tools to evaluate STAT-dependent malignancy and showed that survival and growth of lymphoid malignancies requires expression of STAT3. In contrast, loss of STAT3 in normal cells does not impair their growth or survival; but in spite of this apparent dispensability of STAT3, STAT3-null fibroblasts are resistant to transformation by a variety of oncogenes. The precise molecular mechanisms responsible for the tumorigenic activity of STAT3 have been only partially elucidated. While the tyrosine phosphorylation of STAT3, which is indicative of its signal-dependent activation, is a common occurrence in tumors, and appears to play a crucial role in some malignancies, a variety of new data suggest that it can be dispensable under some circumstances and STAT3 can participate in transformation through novel and non-canonical mechanisms. The discovery and dissection of non-canonical modes of STAT3 action will open new avenues for the design of effective therapeutics capable of neutralizing the tumorigenic properties of this molecule

beta-cells under immune attack are destroyed by the aberrant activation of key intracellular signaling cascades. The aim of the present study was to evaluate the contribution of the signal transducer and activator of transcription (STAT)-1 pathway for beta-cell apoptosis by studying the sensitivity of beta-cells from STAT-1 knockout (-/-) mice to immune-mediated cell death in vitro and in vivo. Whole islets from STAT-1-/- mice were completely resistant to interferon (IFN)-gamma (studied in combination with interleukin [IL]-1beta)-mediated cell death (92 +/- 4% viable cells in STAT-1-/- mice vs. 56 +/- 3% viable cells in wild-type controls, P < or = 0.001) and had preserved insulin release after exposure to IL-1beta and IFN-gamma. Moreover, analysis of cell death in cytokine-exposed purified beta-cells confirmed that protection was due to absence of STAT-1 in the beta-cells themselves. Deficiency of STAT-1 in islets completely prevented cytokine-induced upregulation of IL-15, interferon inducible protein 10, and inducible nitric oxide synthase transcription but did not interfere with monocyte chemoattractant protein 1 and macrophage inflammatory protein 3alpha expression. In vivo, STAT-1-/- mice were partially resistant to development of diabetes after multiple low-dose streptozotocin injections as reflected by mean blood glucose at 12 days after first injection (159 +/- 28 vs. 283 +/- 81 mg/dl in wild-type controls, P < or = 0.05) and diabetes incidence at the end of the follow-up period (39 vs. 73% in wild-type controls, P < or = 0.05). In conclusion, the present results indicate that STAT-1 is a crucial transcription factor in the process of IFN-gamma-mediated beta-cell death and the subsequent development of immune-mediated diabetes

Interferon regulatory factor (IRF)7 is a key transcription factor required for establishment of antiviral resistance. In response to infection, IRF7 is activated by phosphorylation through the action of the non-canonical IkappaB kinases, IkappaB kinase-epsilon and TANK-binding kinase 1. Activation leads to nuclear retention, DNA binding, and derepression of transactivation ability. Clusters of serine residues located in the carboxyl-terminal regulatory domain of IRF7 are putative targets of virus-activated kinases. However, the exact sites of phosphorylation have not yet been established. Here, we report a comprehensive structure-activity examination of potential IRF7 phosphorylation sites through analysis of mutant proteins in which specific serine residues were altered to alanine or aspartate. Phosphorylation patterns of these mutants were analyzed by two-dimensional gel electrophoresis, and their transcriptional activity was monitored by reporter assays. Essential phosphorylation events were mapped to amino acids 437-438 and a redundant set of sites at either amino acids 429-431 or 441. IRF7 recovered from infected cells was heterogeneously phosphorylated at these sites, and greater phosphorylation correlated with increased transactivation. Interestingly, a distinct serine cluster conserved in the related protein IRF3 was also essential for IRF7 activation and distal phosphorylation. However, the essential role of this motif did not appear to be fulfilled by phosphorylation. Rather, these serine residues and an adjacent leucine were required for phosphorylation at distal sites and may determine a conformational element required for function

Phosphorylation on Y705 is obligatory for STAT3 activation, but full transcriptional activity of this widely expressed protein also requires phosphorylation on S727. We described earlier the STAT3 SA/- mice (SA, S727A allele) on a Black 6 (Bl6) background that showed 75% perinatal lethality and early growth retardation presumably due to the decreased transcription supported by STAT3 S727A. We now report additional analyses of long-term surviving SA/- animals which show no important tissue abnormalities. However, we have found a much greater susceptibility to doxorubicin-induced heart failure in the SA/- mice. Also we introduced the SA allele into strain 129 and found the SA/- mice showed greater susceptibility to LPS-induced toxicity. These results suggest a continued need for normal STAT3 transcriptional activity to resist two different noxious challenges that mimic the conditions necessary to induce adult diseases

There is accumulating evidence that the p38 MAP kinase pathway plays important roles in Type I interferon (IFN) signaling, but the mechanisms regulating p38 activation during engagement of the Type I IFN receptor remain to be defined. We sought to identify the events that lead to activation of the p38 MAP kinase in response to Type I IFNs. Our data demonstrate that treatment of sensitive cell lines with IFNalpha results in activation of both MAP kinase kinase 3 (MKK3) and MAP kinase kinase 6 (MKK6). Such IFN-inducible activation of MKK3 and MKK6 is essential for downstream phosphorylation and activation of the p38 MAP kinase, as shown by studies using mouse embryonic fibroblasts (MEFs) with targeted disruption of the Mkk3 and Mkk6 genes (MKK3-/- MKK6-/-). Similarly, IFN-dependent activation of the downstream effectors of p38, MAPKAPK-2 and MAPKAPK-3, is not detectable in cells lacking Mkk3 and Mkk6, demonstrating that the function of these MAP kinase kinases is required for full activation of the p38 pathway. To define the functional relevance of MKK3/6 engagement in Type I IFN signaling, IFN-inducible gene transcription was evaluated in the MKK3/MKK6 double knock-out cells. IFNalpha- and IFNbeta-dependent transcription via either interferon-stimulated response element or IFNgamma activated site elements was defective in MKK3 -/-/MKK6 -/- MEFs in luciferase reporter assays. In addition, IFN-dependent induction of two genes known to be of importance in the generation of IFN responses, Isg15 and Irf-9, was diminished in the absence of Mkk3 and Mkk6. The effects of Mkk3 and Mkk6 on IFN-dependent transcription were unrelated to any effects on the phosphorylation and activation of STAT proteins, indicating the presence of a STAT-independent mechanism. Altogether, our findings demonstrate that MKK3 and MKK6 are rapidly activated during engagement of the Type I IFN receptor and play important roles in Type I IFN signaling and the generation of IFN responses

Signal transducer and activator of transcription 3 (STAT3) is phosphorylated on tyrosine residue 705 in response to growth factors or cytokines to form activated homodimers that drive gene expression. Because the stat3 promoter has a binding site for STAT3 dimers, the amount of STAT3 protein increases when STAT3 is activated (e.g., in response to interleukin 6). Unphosphorylated STAT1 is known to drive the expression of certain genes. To explore the possibility of a similar role for the induced expression of unphosphorylated STAT3, we overexpressed either Y705F STAT3, which can not be phosphorylated on residue 705, or wild-type STAT3 in normal human mammary epithelial cells or STAT3-null mouse cells. The levels of many mRNAs were affected strongly by high levels of either form of STAT3. Some genes whose expression was increased by overexpressed STAT3, but not by activated STAT3 dimers, encode well-known oncoproteins (e.g., MRAS and MET). In many tumors, STAT3 is activated constitutively, and thus the unphosphorylated form is likely to be expressed highly, driving oncogene expression by a novel mechanism. In addition, expression of the stat3 gene is increased strongly in response to interleukin 6, and the high levels of unphosphorylated STAT3 that result drive a substantial late phase of gene expression in response to this cytokine. Thus, unphosphorylated STAT3, which activates gene expression by a novel mechanism distinct from that used by STAT3 dimers, is very likely to be an important transcription factor both in cancer and in responses to cytokines

This paper explores the influence of visual sources on Roger N. Shepard's 1971 mental rotation experiments and the centrality of ambiguity as one of his experimental and artistic concerns. Sources include Shepard's statements about ambiguity as expressed in the book, Mind Sights, and a recent interview. Parallel investigations of ambiguity by the contemporary artists Al Held and Robert Smithson are considered. Shepard utilized a wide range of visual sources while formulating his experimental design, namely Necker cube illusions, hypnopompic images, Rene Magritte, and M.C. Escher. In addition, he drew upon key art historical theses of the time, such as Ernst Gombrich's theories about schemas. For Shepard as for Gombrich, the world of appearances is a world of ambiguity

In this report, the signaling pathways utilized by interferon (IFN)-gamma in neurons and their respective roles in the inhibition of vesicular stomatitis virus (VSV) replication were studied. The authors have previously shown that IFN-gamma treatment of NB41A3 neuroblastoma cells results in a 2-log inhibition of VSV production. This inhibition of VSV replication is dependent both in vitro and in vivo on nitric oxide (NO) production by NO synthase (NOS)-1. In NB41A3 neuroblastoma cells, IFN-gamma was found to induce the signal transducer and activator of transcription (STAT) STAT1 phosphorylation, interferon regulatory factor (IRF)-1 expression, and p42/p44 mitogen-activated protein kinase (MAPK) phosphorylation; MAPK, however, was not required for inhibition of viral replication. Using olfactory bulb-enriched primary neuronal cultures, the inhibition of VSV replication was found to be STAT1 dependent, but did not require IRF-1