Interleukin-10 inhibits tumor necrosis factor-alpha production in lipopolysaccharide-stimulated RAW 264.7 cells through reduced MyD88 expression

The mechanism of interleukin (IL)-10-mediated inhibition of tumor necrosis factor (TNF)-alpha production was studied by lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophage cells. IL-10 inhibited TNF-alpha production transiently at an early stage after LPS stimulation. IL-10 inhibited the activation of nuclear factor (NF)-kappaB, p38 and stress-activated protein kinase (SAPK) in LPS-stimulated RAW 264.7 cells. Although the level of MyD88 protein increased in response to LPS, IL-10 prevented the LPS-induced MyD88 augmentation. There was no significant difference in the MyD88 mRNA expression between the cells pretreated with or without IL-10 in response to LPS. Therefore, IL-10 was suggested to inhibit LPS-induced TNF-alpha production via reduced MyD88 expression.     

Comprehensive analysis of the effects of Escherichia coli ORFs on protein translation reaction

Protein synthesis is one of the most important reactions in the cell. Recent experimental studies indicated that this complex reaction can be achieved with a minimum complement of 36 proteins and ribosomes by reconstituting an Escherichia coli-based in vitro translation system with these protein components highly purified on an individual basis. From the protein-protein interaction (PPI) network of E. coli proteins, these minimal protein components are known to interact physically with large numbers of proteins. However, it is unclear what fraction of E. coli proteins are linked functionally with the minimal protein synthesis system. We investigated the effects of each of the 4194 E. coli ORF products on the minimal protein synthesis system; at least 12% of the entire ORF products, a significant fraction of the gene product of E. coli, affect the activity of this system. Furthermore 34% of these functional modifiers present in the PPI network were shown by mapping to be directly linked (i.e. to interact physically) with the minimal components of the PPI network. Topological analysis of the relationships between modifiers and the minimal components in the PPI network indicated clustering of the minimal components. The modifiers showed no such clustering, indicating that the location of functional modifiers is spread across the PPI network rather than clustering close to the minimal protein components. These observations may reflect the evolutionary process of the protein synthesis system.     

Promotion of reprogramming to ground state pluripotency by signal inhibition

Induced pluripotent stem (iPS) cells are generated from somatic cells by genetic manipulation. Reprogramming entails multiple transgene integrations and occurs apparently stochastically in rare cells over many days. Tissue stem cells may be subject to less-stringent epigenetic restrictions than other cells and might therefore be more amenable to deprogramming. We report that brain-derived neural stem (NS) cells acquire undifferentiated morphology rapidly and at high frequency after a single round of transduction with reprogramming factors. However, critical attributes of true pluripotency—including stable expression of endogenous Oct4 and Nanog, epigenetic erasure of X chromosome silencing in female cells, and ability to colonise chimaeras—were not attained. We therefore applied molecularly defined conditions for the derivation and propagation of authentic pluripotent stem cells from embryos. We combined dual inhibition (2i) of mitogen-activated protein kinase signalling and glycogen synthase kinase-3 (GSK3) with the self-renewal cytokine leukaemia inhibitory factor (LIF). The 2i/LIF condition induced stable up-regulation of Oct4 and Nanog, reactivation of the X chromosome, transgene silencing, and competence for somatic and germline chimaerism. Using 2i /LIF, NS cell reprogramming required only 1–2 integrations of each transgene. Furthermore, transduction with Sox2 and c-Myc is dispensable, and Oct4 and Klf4 are sufficient to convert NS cells into chimaera-forming iPS cells. These findings demonstrate that somatic cell state influences requirements for reprogramming and delineate two phases in the process. The ability to capture pre-pluripotent cells that can advance to ground state pluripotency simply and with high efficiency opens a door to molecular dissection of this remarkable phenomenon.     

Strategies for Selection from Protein Libraries Composed of de Novo Designed Secondary Structure Modules

As more and more protein structures are determined, it has become clear that there is only a limited number of protein folds in nature. To explore whether the protein folds found in nature are the only solutions to the protein folding problem, or that a lack of evolutionary pressure causes the paucity of different protein folds found, we set out to construct protein libraries without any restriction on topology. We generated different libraries (all alpha-helix, all beta-strand and alpha-helix plus beta-strand) with an average length of 100 amino acid residues, composed of designed secondary structure modules (alpha-helix, beta-strand and beta-turn) in various proportions, based primarily on the patterning of polar and non-polar residues. From the analysis of proteins chosen randomly from the libraries, we found that a substantial portion of pure alpha-helical proteins show properties similar to native proteins. Using these libraries as a starting point, we aim to establish a selection system which allows us to enrich proteins with favorable folding properties (non-aggregating, compactly folded) from the libraries. We have developed such a method based on ribosome display. This selection is based on two concepts: (1) misfolded proteins are more sensitive to proteolysis, (2) misfolded and/or aggregated proteins are more hydrophobic. We show that by applying each of these selection criteria proteins that are compactly folded and soluble can be enriched over insoluble and random coil proteins.     

Helicobacter pylori-associated gastric pro- and antioxidant formation in Mongolian gerbils

Helicobacter pylori colonized gastric mucosa is manifest in a significant neutrophil infiltration with an extensive level of oxyradical formation. Mongolian gerbil is one of the excellent models for H. pylori-infection. The present study was designed to investigate pro- and antioxidant formation in the stomach of H. pylori-positive gerbils. Fourteen male Mongolian gerbils (MGS/Sea) were orally inoculated with H. pylori (ATCC43504) (Hp group) and 15 gerbils were inoculated with the culture media (Control). H. pylori infection was confirmed by the serum anti-H. pylori IgG test. Each gerbil was evaluated 6 or 12 weeks after the inoculation. Neutrophil infiltration was assessed by the tissue MPO activity. Mucosal oxidative stress was evaluated by thiobarbituric acid-reactive substances (TBARS), total glutathione contents, glutathione peroxidase (GSHPx) activity and Cu-, Zn-superoxide dismutase (SOD) activity. In Hp group, the H. pylori was persistently infected until 12 weeks. The level of MPO activity was significantly higher in Hp group at 6 and 12 weeks. Although the levels of TBARS and total glutathione were within the same range as controls at 6 weeks, they were significantly increased at 12 weeks. However, GSHPx activity was significantly increased at 6 weeks, but became the same range with the controls at 12 weeks. SOD activity showed no significant increase in Hp group at 6 and 12 weeks. In conclusion, H. pylori inoculation induced gastric mucosal neutrophil activation and pro-oxidant formation and also increased total glutathione contents, one of the mucosal antioxidants in gerbils.     

Requirement for Mesorhizobium loti ornithine transcarbamoylase for successful symbiosis with Lotus japonicus as revealed by an unexpected long-range genome deletion

With the original aim of surveying the role of exopolysaccharide (EPS) in Lotus-Mesorhizobium symbiosis, we carried out Tn5 mutagenesis of Mesorhizobium loti and obtained 32 mutants with defects in EPS biosynthesis. One of the mutants, HIA22, formed pseudonodules and failed to fix nitrogen with Lotus japonicus. However, complementation analysis unexpectedly revealed that the potential gene with the locus tag, mll2073, interrupted by Tn5 was responsible for neither normal EPS synthesis nor symbiosis. Further analysis uncovered that HIA22 had a genome deletion of approximately 20 kbp, resulting in the loss of two separate genes responsible for EPS biosynthesis and symbiosis. One gene with the locus tag, mll5669, was needed to synthesize normal EPS that fluoresced on medium containing Calcofluor and encoded a homolog of O-antigen acetyl transferase in Salmonella typhimurium. A specific mutant of mll5669, EMB-B58, successfully fixed nitrogen when infected onto L. japonicus. Another gene, mlr5647, was needed to establish fully functional nodules and encoded ornithine carbamoyl transferase [ArgF (EC 2.1.3.3)], which participates in arginine biosynthesis. A specific mutant of mlr5647, EMB-Y2, showed arginine auxotrophy and formed infection threads, but the nodules formed by this strain had few infected cells filled with bacteroids. These mutant phenotypes were complemented by supplementation of arginine or citrulline to bacterial or plant medium. EMB-Y2 represented a novel class of rhizobial arginine auxotrophs with symbiotic deficiency, and its phenotypes indicated that sufficient supply of citrulline or its derivative is essential for successful infection or for a stage in the infection process in Lotus-Mesorhizobium symbiosis.