The implication of adiponectin and resistin in gastrointestinal diseases

Adiponectin and resistin, members of the adipokine family, are multi-task hormones involved in several disorders, including those of the alimentary tract. In the present review, eligible studies focusing on the role of adiponectin and resistin in gastrointestinal diseases are manifested together and classified according to anatomic criteria. In addition, similarities and common patterns have been recognized, ultimately revealing an inverse association: the down-regulation of adiponectin and up-regulation of resistin - both in vitro and in vivo - in gastrointestinal disorders, irrespective of their diverse nature - inflammatory, autoimmune or malignant - or anatomic position - esophageal, gastric, of the small intestine, colonic. Finally, a potential role for both adipokines in alimentary tract-related carcinogenesis has been identified, possibly representing a missing link between obesity and cancer.     

Expression of an HCV Core Antigen Coding Gene in Tobacco (N. tabacum L.)

Abstract

Hepatitis C virus (HCV) is the major agent causing chronic liver disease. The core gene is the most conserved sequence in the HCV genome and proved immunoreactive when expressed in bacteria and antigenic in humans. In order to test the ability of plants to express the core gene for the production of core antigen, transgenic tobacco plants carrying the core gene were generated. The core protein was stably synthesized in T₀ and T₁ generations and was found to be immunoreactive, not only with anti-core polyclonal and monoclonal antibodies, but also was able to recognize the HCV virus in infected human serum. The prospects of producing a plant based vaccine and/or a food vaccine for this important virus are discussed.     

Cysteine-scanning analysis of the nucleobase-ascorbate transporter signature motif in YgfO permease of Escherichia coli: Gln-324 and Asn-325 are essential, and Ile-329-Val-339 form an alpha-helix

The nucleobase-ascorbate transporter (NAT) signature motif is a conserved sequence motif of the ubiquitous NAT/NCS2 family implicated in defining the function and selectivity of purine translocation pathway in the major fungal homolog UapA. To analyze the role of NAT motif more systematically, we employed Cys-scanning mutagenesis of the Escherichia coli xanthine-specific homolog YgfO. Using a functional mutant devoid of Cys residues (C-less), each amino acid residue in sequence (315)GSIPITTFAQNNGVIQMTGVASRYVG(340) (motif underlined) was replaced individually with Cys. Of the 26 single-Cys mutants, 16 accumulate xanthine to > or =50% of the steady state observed with C-less YgfO, 4 accumulate to low levels (10-25% of C-less), F322C, N325C, and N326C accumulate marginally (5-8% of C-less), and P318C, Q324C, and G340C are inactive. When transferred to wild type, F322C(wt) and N326C(wt) are highly active, but P318G(wt), Q324C(wt), N325C(wt), and G340C(wt) are inactive, and G340A(wt) displays low activity. Immunoblot analysis shows that replacements at Pro-318 or Gly-340 are associated with low or negligible expression in the membrane. More extensive mutagenesis reveals that Gln-324 is critical for high affinity uptake and ligand recognition, and Asn-325 is irreplaceable for active xanthine transport, whereas Thr-332 and Gly-333 are important determinants of ligand specificity. All single-Cys mutants react with N-ethylmaleimide, but regarding sensitivity to inactivation, they fall to three regions; positions 315-322 are insensitive to N-ethylmaleimide, with IC(50) values > or =0.4 mM, positions 323-329 are highly sensitive, with IC(50) values of 15-80 microM, and sensitivity of positions 330-340 follows a periodicity, with mutants sensitive to inactivation clustering on one face of an alpha-helix.     

The role of protein phosphorylation in alpha2,6(N)-sialyltransferase activity

Sialoglycoproteins play a key role in both brain development and neuronal plasticity with their sialylation state being controlled by the sialyltransferase (STN) family of enzymes. In this study, we have determined the role of specific kinase enzymes in the expression and catalytic activity of the alpha2,6 STN (ST6N) isozyme. The catalytic activity was moderately decreased following the inhibition of GSK3beta with LiCl. However, there was a significant increase in catalytic activity following activation of protein kinase C (PKC) by phorbol ester. There was no change in the expression levels of the enzyme protein following any of the treatments. The changes in enzyme catalytic activity were also mirrored by the expression of both protein-bound sialic acid and the polysialic acid oligosaccharide group attached to the neural cell adhesion molecule, NCAM. These results provide further evidence for the role of second messenger-associated kinase enzymes in the modulation of the cell glycosylation potential.     

Human mitochondrial tRNAMet is exported to the cytoplasm and associates with the Argonaute 2 protein

Argonaute (Ago) proteins are the effector proteins of RNA interference (RNAi) and related silencing mechanisms that are mediated by small RNAs. Ago proteins bind directly to microRNAs (miRNAs) and to short interfering RNAs and are the core protein components of RNA induced silencing complexes (RISCs) and microRNPs (miRNPs). Here we report that an ~70-nt RNA associates specifically with immunopurified Ago2 expressed in human 293 cells. By directional cloning we identified this RNA as the mitochondrial tRNA(Met) (mt tRNA(Met)). Various exported (mt) tRNAs were detected in the cytosol of 293 cells, but Ago2 was found selectively bound to (mt) tRNA(Met). The association in the cytosol of exported (mt) tRNA(Met) with Ago2 complements genetic and microscopic data that link mitochondria with RNAi-related components and events.     

Alternate translation occurs within the core coding region of the hepatitis C viral genome

The majority of hepatitis C virus (HCV) isolates contain an open reading frame (ORF) overlapping with the core coding sequences in the +1 frame, which was assumed to be untranslated. We present evidence supporting the expression of this ORF (designated core+1 ORF) via novel translation mechanisms. First, fusion of the luciferase gene with the HCV-1 core+1 ORF followed by in vitro translation resulted in the synthesis of a chimeric protein (core+1-luciferase) that exhibited approximately 54% luciferase activity relative to the positive control (core-luciferase). Second, antisera raised against two different synthetic core+1 peptides recognized the previously identified p16 (but not p21) core protein band expressed from HCV-1, indicating the presence of epitopes from the core+1 ORF within the p16 protein. Third, HCV-positive sera specifically recognized lysates of Escherichia coli cells expressing recombinant core+1 protein, suggesting the presence of anti-core+1 antibodies in HCV-infected patients. Finally, luciferase tagging experiments designed to assess for -1 frameshifting combined with site-directed mutagenesis experiments supported the presence of +1/-1 ribosomal frameshift translation mechanisms within the core coding region. In conclusion, our data provide evidence for novel translation mechanisms within the core coding region and demonstrate the expression of the core+1 ORF, at least for some HCV isolates.     

Overexpression of α2,3 sialyltransferase in neuroblastoma cells results in an upset in the glycosylation process

Glycosylation is key posttranslational modification for membrane-bound and secreted proteins that can influence both the secondary structure and the function of the protein backbone. In order to investigate the effect of altered cellular glycosylation potential, we have generated a number of clonal cell lines over-expressing the 2,3(N) sialyltransferase enzyme (ST3N). In general, there was a decrease in total sialyltransferase (ST) enzyme activity in the clones transfected with the ST3N cDNA, with this decrease being inversely proportional to the quantity of the mRNA coding for the enzyme. The ST3N enzyme was, however, functional and there was an increase in both MAA lectin staining and the expression of polysialic acid, which is attached to the NCAM protein backbone primarily via an 2,3 linkage. These results suggest that the overexpression of a sialyltransferase may upset the sialylation potential of the cell.     

The generation and characterization of a rat neural cell line overexpressing the α2,6(N) sialyltransferase

In order to examine the effects of altered protein sialylation on neural cell function, B104 rat neuroblastoma cells were stably transfected with the cDNA coding for 2,6(N) sialyltransferase (ST(6)N). Lectin blot analysis of the clones demonstrated an increase in staining of the Sambucus nigra lectin, which detects 2,6 linked sialic acid, in parallel with enzyme activity. There was a concomitant decrease in staining by the Maackia amurensis lectin which labels 2,3-linked sialic acid, indicating that the individual sialyltransferase enzymes may compete for penultimate galactose acceptor sites. While there was an initial increase in protein-bound sialic acid in parallel with enzyme activity, the sialylation of the cells was demonstrated to be saturable. There was an inverse relationship between cell adhesion to a fibronectin substrate and ST(6)N activity suggesting that the negatively charged sugar acts to modulate cell-substrate interaction. These cells will provide an ideal model system with which to further investigate the effect of altered sialic acid on neural cell function.     

Benthic foraminiferal assemblages in the severely polluted coastal environment of Drapetsona-Keratsini,Saronikos Gulf (Greece)

Surface sediments were collected from the coastal zone of Drapetsona–Keratsini (Saronikos Gulf, Greece) in December 2012 for determining the local benthic foraminiferal community, identifying their spatial distribution patterns, and evaluating the response of foraminiferal species to geochemical composition through the hierarchical cluster analysis, principal component analysis and Spearman's rho correlation. Foraminifera can be classified into three distinct assemblages associated with the granulometry, elemental geochemistry, particulate organic carbon content and degree of sediment contamination. A relatively low-diversity assemblage, dominated by stress-tolerant taxa with Ammonia tepida Bolivina spathulata and Bulimina elongata being the prevailing species, is characteristic of the silty seabed of the main part of Drapetsona coastal zone and the Keratsini Port central basin, where organic carbon content, aliphatic and polycyclic aromatic hydrocarbons concentrations and trace metal loads are greatly elevated. On the sandy bottom of the investigated area, relatively high frequencies of miliolids prevail. An epiphytic rotaliid-dominated assemblage is recorded in the slightly-polluted sedimentary bottom of the inner and western part of the Keratsini Port.