Immunoglobulin G galactosylation and sialylation are associated with pregnancy-induced improvement of rheumatoid arthritis and the postpartum flare: results from a large prospective cohort study

Introduction  

Improvement of rheumatoid arthritis (RA) during pregnancy has been causatively associated with increased galactosylation of immunoglobulin G (IgG) N-glycans. Since previous studies were small, did not include the postpartum flare and did not study sialylation, these issues were addressed in the present study.     

Field experiments on seed dispersal by wind in ten umbelliferous species (Apiaceae)

This report presents data from experiments on seed dispersal by wind for ten species of the family Apiaceae. Seed shadows were obtained in the field under natural conditions, using wind speeds between four and ten m/s. The flight of individual seeds was followed by eye, and seed shadows were acquired, with median distances varying from 0.7 to 3.1 m between species. Multiple regression models of wind speed and seed weight on dispersal distance were significant for six out of ten species; wind speed had significant effects in seven cases, but seed weight only once. A good correlation between mean terminal falling velocity of the seeds of a species and median dispersal distance, indicates the promising explanatory power that individual terminal velocity data might have on dispersal distance, together with wind speed and turbulence. The theory that seeds that seem to be adapted to wind dispersal travel much longer distances than seeds that have no adaptation was tested. Flattened and winged seeds were indeed found to be transported further by wind, but not much further. Moreover, the species with wind-adapted seeds were also taller, being an alternative explanation since their seeds experienced higher wind speeds at these greater heights. Furthermore, flattened and winged seeds were disseminated from ripe umbels at lower wind speeds in the laboratory. This means that the observed difference in dispersal distance would have been smaller when species specific thresholds for wind speed were incorporated in the field experiments. We argue therefore, that seed morphology is not always the best predictor in classifying species in groups with distinctly different dispersal ability.     

Regulation of rat liver microsomal glutathione S-transferase activity by thiol/disulfide exchange

The regulation of purified glutathione S-transferase from rat liver microsomes was studied by examining the effects of various sulfhydryl reagents on enzyme activity with 1-chloro-2,4-dinitrobenzene as the substrate. Diamide (4 mM), cystamine (5 mM), and N-ethylmaleimide (1 mM) increased the microsomal glutathione S-transferase activity by 3-, 2-, and 10-fold, respectively, in absence of glutathione; glutathione disulfide had no effect. In presence of glutathione, microsomal glutathione S-transferase activity was increased 10-fold by diamide (0.5 mM), but the activation of the transferase by N-ethylmaleimide or cystamine was only slightly affected by presence of glutathione. The activation of microsomal glutathione S-transferase by diamide or cystamine was reversed by the addition of dithiothreitol. Glutathione disulfide increased microsomal glutathione S-transferase activity only when membrane-bound enzyme was used. These results indicate that microsomal glutathione S-transferase activity may be regulated by reversible thiol/disulfide exchange and that mixed disulfide formation of the microsomal glutathione S-transferase with glutathione disulfide may be catalyzed enzymatically in vivo.     

Tyrosine phosphoproteomics of fibroblast growth factor signaling: a role for insulin receptor substrate-4

Signal transduction by receptor tyrosine kinases is initiated by recruitment of a variety of signaling proteins to tyrosine-phosphorylated motifs in the activated receptors. Several signaling pathways are thus activated in parallel, the combination of which decides the cellular response. Here, we present a dual strategy for extensive mapping of tyrosine-phosphorylated proteins and probing of signal-dependent protein interactions of a signaling cascade. The approach relies on labeling of cells with "heavy" and "light" isotopic forms of Arg to distinguish two cell populations. First, tyrosine-phosphorylated proteins from stimulated ("heavy"-labeled) and control samples ("normal"-labeled) are isolated and subjected to high sensitivity Fourier transform ion cyclotron resonance mass spectrometry analysis. Next, phosphopeptides corresponding to tyrosine phosphorylation sites identified during the tyrosine phosphoproteomic analysis are used as baits to isolate phosphospecific protein binding partners, which are subsequently identified by mass spectrometry. We used this approach to identify 28 components of the signaling cascade induced by stimulation with the basic fibroblast growth factor. Insulin receptor substrate-4 was identified as a novel candidate in fibroblast growth factor receptor signaling, and we defined phosphorylation-dependent interactions with other components, such as adaptor protein Grb2, of the signaling cascade. Finally, we present evidence for a complex containing insulin receptor substrate-4 and ShcA in signaling by the fibroblast growth factor receptor.     

Soluble M1 protein of Streptococcus pyogenes triggers potent T cell activation

Streptococcus pyogenes of the M1 serotype is commonly associated with large outbreaks of invasive streptococcal infections and development of streptococcal toxic shock syndrome (STSS). The pathogenesis behind these infections is believed to involve bacterial superantigens that induce potent inflammatory responses, but the reason why strains of the M1 serotype are over-represented in STSS is still not understood. In the present investigation, we show that a highly purified soluble form of the M1 protein from S. pyogenes , which lacks the membrane-spanning region, is a potent inducer of T cell proliferation and release of Th1 type cytokines. M1 protein-evoked T cell proliferation was HLA class II-dependent but not MHC-restricted, did not require intracellular processing and was Vβ-restricted. Extensive mass spectrometry studies indicated that there were no other detectable proteins in the preparation. Taken together, our data demonstrate that soluble M1 protein is a novel streptococcal superantigen, which likely contributes to the excessive T cell activation and hyperinflammatory response seen in severe invasive streptococcal infections.     

Lactic acid bacteria as prime candidates for codon optimization

In species having a strong correlation of expressivity and codon bias it has been shown that heterologous expression can be optimized by changing codons of the introduced gene towards the set of codons that the host organism naturally uses in its highly expressed genes. Even though two lactic acid bacteria are fully sequenced, there are no reports on attempts of codon optimization in the literature. In this report it is demonstrated that codons used in highly expressed genes tend to differ from the codons in lowly expressed genes, and that there is a strong correlation of codon bias and empirical expressivity (codon adaptation index) in Lactococcus lactis and Lactobacillus plantarum. This strongly suggests that codon optimization strategies could be applied to expression systems with lactic acid bacteria as producer strains. A good example of a candidate for codon optimization is the mouse interleukin-2 gene, which in its natural form has an extremely low codon adaptation index for expression in Lc. lactis.     

Binding,internalization, and degradation of antiproliferative heparan sulfate by human embryonic lung fibroblasts

Binding, internalization, and degradation of ¹²⁵I-labeled, antiproliferative, or nonantiproliferative heparan sulfate by human embryonic lung fibroblasts was investigated. Both L-iduronate-rich, antiproliferative heparan sulfate species as well as L-iduronate-poor, inactive ones were bound to trypsin-releasable, cell-surface sites. Both heparan sulfate types were bound with approximately the same affinity to one high-affinity site (K_d approximately 10⁻⁸ M) and to one (K_d approximately 10⁻⁶ M), respectively. Results of Hill-plot analysis suggested that the two sites are independent. Competition experiments with unlabeled glycosaminoglycans indicated that the binding sites had a selective specificity for sulfated, L-iduronate-rich heparan sulfate. Dermatan sulfate, which is also antiproliferative, was weakly bound to the cells. The antiproliferative effects of heparan and dermatan sulfate appeared to be additive. Hence, the two glycosaminoglycans probably exert their effect through different mechanisms. At concentrations above 5 μg/ml (approximately 10⁻⁷ M), heparan sulfate was taken up by human embryonic lung fibroblasts, suggesting that the low-affinity site represents an endocytosis receptor. The antiproliferative effect of L-iduronate-rich heparan sulfate species was also exerted at the same concentrations. The antiproliferative species was taken up to a greater degree than the inactive one, suggesting a requirement for internalization. However, competition experiments with dextran sulfate suggested that both the high-affinity and the low-affinity sites are involved in mediating the antiproliferative effect. Structural analysis of the inactive and active heparan sulphate preparations indicated that although sulphated L-iduronate appears essential for antiproliferative activity, it is not absolutely required for binding to the cells. Degradation of internalized heparan sulfate was analyzed by polyacrylamide gel electrophoresis using a sensitive detection technique. The inactive species was partially degraded, whereas the antiproliferative one was only marginally affected. J. Cell. Biochem. 64:595–604. © 1997 Wiley-Liss, Inc.     

Two msbB genes encoding maximal acylation of lipid A are required for invasive Shigella flexneri to mediate inflammatory rupture and destruction of the intestinal epithelium

Shigella flexneri is a Gram-negative pathogen that invades and causes inflammatory destruction of the human colonic epithelium, thus leading to bloody diarrhea and dysentery. A type III secretion system that delivers effector proteins into target eukaryotic cells is largely responsible for cell and tissue invasion. However, the respective role of this invasive phenotype and of lipid A, the endotoxin of the Shigella LPS, in eliciting the inflammatory cascade that leads to rupture and destruction of the epithelial barrier, was unknown. We investigated whether genetic detoxification of lipid A would cause significant alteration in pathogenicity. We showed that S. flexneri has two functional msbB genes, one carried by the chromosome (msbB1) and the other by the virulence plasmid (msbB2), the products of which act in complement to produce full acyl-oxy-acylation of the myristate at the 3' position of the lipid A glucosamine disaccharide. A mutant in which both the msbB1 and msbB2 genes have been inactivated was impaired in its capacity to cause TNF-alpha production by human monocytes and to cause rupture and inflammatory destruction of the epithelial barrier in the rabbit ligated intestinal loop model of shigellosis, indicating that lipid A plays a significant role in aggravating inflammation that eventually destroys the intestinal barrier. In addition, neutralization of TNF-alpha during invasion by the wild-type strain strongly impaired its ability to cause rupture and inflammatory destruction of the epithelial lining, thus indicating that TNF-alpha is a major effector of epithelial destruction by Shigella.