217 research outputs found

    Dextran Sulfate Sodium Inhibits Alanine Synthesis in Caco-2 Cells

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    To understand and characterize the pathogenic mechanisms of inflammatory bowel disease, dextran sulfate sodium (DSS) has been used to induce acute and chronic colitis in animal models by causing intestinal epithelium damage. The mechanism of action of DSS in producing this outcome is not well understood. In an effort to understand how DSS might impact epithelial cell metabolism, we studied the intestinal epithelial cell line Caco-2 incubated with 1% DSS over 56 hours using 1H NMR spectroscopy. We observed no difference in cell viability as compared to control cultures, and an approximately 1.5-fold increase in IL-6 production upon incubation with 1% DSS. The effect on Caco-2 cell metabolism as measured through changes in the concentration of metabolites in the cell supernatant included a three-fold decrease in the concentration of alanine. Given that the concentrations of other amino acids in the cell culture supernatant were not different between treated and control cultures over 56 hours suggest that DSS inhibits alanine synthesis, specifically alanine aminotransferase, without affecting other key metabolic pathways. The importance of alanine aminotransferase in inflammatory bowel disease is discussed

    Metabolomic profiles are gender, disease and time specific in the interleukin-10 gene-deficient mouse model of inflammatory bowel disease.

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    Metabolomic profiling can be used to study disease-induced changes in inflammatory bowel diseases (IBD). The aim of this study was to investigate the difference in the metabolomic profile of males and females as they developed IBD. Using the IL-10 gene-deficient mouse model of IBD and wild-type mice, urine at age 4, 6, 8, 12, 16, and 20 weeks was collected and analyzed by nuclear magnetic resonance (NMR) spectroscopy. Multivariate data analysis was employed to assess differences in metabolomic profiles that occurred as a consequence of IBD development and severity (at week 20). These changes were contrasted to those that occurred as a consequence of gender. Our results demonstrate that both IL-10 gene-deficient and wild-type mice exhibit gender-related changes in urinary metabolomic profile over time. Some male-female separating metabolites are common to both IL-10 gene-deficient and control wild-type mice and, therefore, appear to be related predominantly to gender maturation. In addition, we were able to identify gender-separating metabolites that are unique for IL-10 gene-deficient and wild-type mice and, therefore, may be indicative of a gender-specific involvement in the development and severity of the intestinal inflammation. The comparison of the gender-separating metabolomic profile from IL-10 gene-deficient mice and wild-type mice during the development of IBD allowed us to identify changes in profile patterns that appear to be imperative in the development of intestinal inflammation, but yet central to gender-related differences in IBD development. The knowledge of metabolomic profile differences by gender and by disease severity has potential clinical implications in the design of both biomarkers of disease as well as the development of optimal therapies

    Cdc4p, a contractile ring protein essential for cytokinesis in Schizosaccharomyces pombe, interacts with a phosphatidylinositol 4-kinase.

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    The proposed function of Cdc4p, an essential contractile ring protein in Schizosaccharomyces pombe, is that of a myosin essential light chain. However, five conditionally lethal cdc4 alleles exhibit complementation in diploids. Such interallelic complementation is not readily explained if the sole function of Cdc4p is that of a myosin essential light chain. Complementation of cdc4 alleles could occur only if different mutant forms can assemble into an active oligomeric complex or if Cdc4p has more than one essential function. To search for other proteins that may interact with Cdc4p, we performed a two-hybrid screen and identified two such candidates: one similar to Saccharomyces cerevisiae Vps27p and the other a putative phosphatidylinositol (PI) 4-kinase. Binding of Cdc4p to the latter and to myosin heavy chain (Myo2p) was confirmed by immunosorbent assays. Deletion studies demonstrated interaction between the Cdc4p C-terminal domain and the PI 4-kinase C-terminal domain. Furthermore, interaction was abolished by the Cdc4p C-terminal domain point mutation, Gly107 to Ser. This allele also causes failure of cytokinesis. Ectopic expression of the PI 4-kinase C-terminal domain caused cytokinesis defects that were most extreme in cells carrying the G107S allele. We suggest that Cdc4p plays multiple roles in cytokinesis and that interaction with a PI 4-kinase may be important for contractile ring assembly and/or function

    Structure of Cdc4p, a Contractile Ring Protein Essential for Cytokinesis in Schizosaccharomyces pombe

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    The Schizosaccharomyces pombe Cdc4 protein is required for the formation and function of the contractile ring, presumably acting as a myosin light chain. By using NMR spectroscopy, we demonstrate that purified Cdc4p is a monomeric protein with two structurally independent domains, each exhibiting a fold reminiscent of the EF-hand class of calcium-binding proteins. Although Cdc4p has one potentially functional calcium-binding site, it does not bind calcium in vitro. Three variants of Cdc4p containing single point mutations responsible for temperature-sensitive arrest of the cell cycle at cytokinesis (Gly-19 to Glu, Gly-82 to Asp, and Gly-107 to Ser) were also characterized by NMR and circular dichroism spectroscopy. In each case, the amino acid substitution only leads to small perturbations in the conformation of the protein. Furthermore, thermal unfolding studies indicate that, like wild-type Cdc4p, the three mutant forms are all extremely stable, remaining completely folded at temperatures significantly above those causing failure of cytokinesis in intact cells. Therefore, the altered phenotype must arise directly from a disruption of the function of Cdc4p rather than indirectly through a disruption of its overall structure. Several mutant alleles of Cdc4p also show interallelic complementation in diploid cells. This phenomenon can be explained if Cdcp4 has more than one essential function or, alternatively, if two mutant proteins assemble to form a functional complex. Based on the structure of Cdc4p, possible models for interallelic complementation including interactions with partner proteins and the formation of a myosin complex with Cdc4p fulfilling the role of both an essential and regulatory light chain are proposed
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