GlmS and NagB Regulate Amino Sugar Metabolism in Opposing Directions and Affect Streptococcus mutans Virulence

Streptococcus mutans is a cariogenic pathogen that produces an extracellular polysaccharide (glucan) from dietary sugars, which allows it to establish a reproductive niche and secrete acids that degrade tooth enamel. While two enzymes (GlmS and NagB) are known to be key factors affecting the entrance of amino sugars into glycolysis and cell wall synthesis in several other bacteria, their roles in S. mutans remain unclear. Therefore, we investigated the roles of GlmS and NagB in S. mutans sugar metabolism and determined whether they have an effect on virulence. NagB expression increased in the presence of GlcNAc while GlmS expression decreased, suggesting that the regulation of these enzymes, which functionally oppose one another, is dependent on the concentration of environmental GlcNAc. A glmS-inactivated mutant could not grow in the absence of GlcNAc, while nagB-inactivated mutant growth was decreased in the presence of GlcNAc. Also, nagB inactivation was found to decrease the expression of virulence factors, including cell-surface protein antigen and glucosyltransferase, and to decrease biofilm formation and saliva-induced S. mutans aggregation, while glmS inactivation had the opposite effects on virulence factor expression and bacterial aggregation. Our results suggest that GlmS and NagB function in sugar metabolism in opposing directions, increasing and decreasing S. mutans virulence, respectively

TRAF6 Establishes Innate Immune Responses by Activating NF-κB and IRF7 upon Sensing Cytosolic Viral RNA and DNA

BACKGROUND:In response to viral infection, the innate immune system recognizes viral nucleic acids and then induces production of proinflammatory cytokines and type I interferons (IFNs). Toll-like receptor 7 (TLR7) and TLR9 detect viral RNA and DNA, respectively, in endosomal compartments, leading to the activation of nuclear factor kappaB (NF-kappaB) and IFN regulatory factors (IRFs) in plasmacytoid dendritic cells. During such TLR signaling, TNF receptor-associated factor 6 (TRAF6) is essential for the activation of NF-kappaB and the production of type I IFN. In contrast, RIG-like helicases (RLHs), cytosolic RNA sensors, are indispensable for antiviral responses in conventional dendritic cells, macrophages, and fibroblasts. However, the contribution of TRAF6 to the detection of cytosolic viral nucleic acids has been controversial, and the involvement of TRAF6 in IRF activation has not been adequately addressed. PRINCIPAL FINDINGS:Here we first show that TRAF6 plays a critical role in RLH signaling. The absence of TRAF6 resulted in enhanced viral replication and a significant reduction in the production of IL-6 and type I IFNs after infection with RNA virus. Activation of NF-kappaB and IRF7, but not that of IRF3, was significantly impaired during RLH signaling in the absence of TRAF6. TGFbeta-activated kinase 1 (TAK1) and MEKK3, whose activation by TRAF6 during TLR signaling is involved in NF-kappaB activation, were not essential for RLH-mediated NF-kappaB activation. We also demonstrate that TRAF6-deficiency impaired cytosolic DNA-induced antiviral responses, and this impairment was due to defective activation of NF-kappaB and IRF7. CONCLUSIONS/SIGNIFICANCE:Thus, TRAF6 mediates antiviral responses triggered by cytosolic viral DNA and RNA in a way that differs from that associated with TLR signaling. Given its essential role in signaling by various receptors involved in the acquired immune system, TRAF6 represents a key molecule in innate and antigen-specific immune responses against viral infection

Effect of Relative Strength of Two Networks on the Internal Fracture Process of Double Network Hydrogels As Revealed by in Situ Small-Angle X-ray Scattering

Double network hydrogels (DN gels) exhibit extraordinarily high strength and toughness by interplay of the two contrasting networks: the rigid, brittle network serves as a sacrificial bond that fractures at a relatively low strain, while the soft, stretchable network serves as hidden length that sustains stress by large extension afterward. The internal fracture process of the brittle network strongly depends on the relative strength of the two networks. In this study, we study the internal fracturing process of typical DN gels that show yielding or necking under uniaxial stretching using in situ small-angle X-ray scattering. Two samples consisting of the same brittle first network from poly(2-acrylamido-2-methylpropanesulfonic acid) but stretchable second network from poly(N,N-dimethylacrylamide) of different concentrations were adopted. We found that (1) the brittle network shows nonaffine deformation even far below the yield strain by local fracture; (2) for the sample of low second network concentration, significant strain amplification occurs around the submicrometer-scale voids (defects) preexisting in the brittle network, which induces the fracture percolation of brittle network from voids to show the necking phenomenon; and (3) the strain amplification at voids is suppressed in the sample of high second network concentration, and fracture of brittle network occurs dispersedly, showing yielding without necking

Mosaic Image Generation using 3D Models

Mosaic is the art of creating images by arranging small pieces of stone, tile or other material. Many conventional methods are used to generate mosaic images from 2D images. In contrast, this paper proposes a method of mosaic image generation using 3D models. This method consists of the following steps. First, the method calculates normal vectors of surface and depth data from 3D models. Then the feature data of the 3D model, such as edges and ridges, are calculated from these data. Next, the guidelines to control the arrangement of tiling are calculated. Finally, tiles are placed along the guide lines. This method has two advantages; 1) It is possible to render a mosaic image from multiple viewpoints. 2) This method can generate a mosaic image which represents three-dimensional features, such as surface ridges and wrinkles, accurately

Emission properties of Sm(III) complexes having remarkably deep-red emission band

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