Strategies for analysis of glycoprotein glycosylation

Glycoproteins are known to exhibit multiple biological functions. In order to assign distinct functional properties to defined structural features, detailed information on the respective carbohydrate moieties is required. Chemical and biochemical analyses, however, are often impeded by the small amounts of sample available and the vast structural heterogeneity of these glycans, thus necessitating highly sensitive and efficient methods for detection, separation and structural investigation. The aim of this article is to briefly review suitable strategies for characterization of glycosylation at the levels of intact proteins, glycopeptides and free oligosaccharides. Furthermore, methods commonly used for isolation, fractionation and carbohydrate structure analysis of liberated glycoprotein glycans are discussed in the context of potential applications in glycoproteomics.     

Free zinc inhibits transport of vitamin C in differentiated HL-60 cells during respiratory burst

Zinc is an essential trace element for the immune system. It is known to be essential for highly proliferating cells, especially for cells of the immune system. However, zinc and other divalent cations are known to inhibit the human neutrophilic NADPH oxidase. Differentiated HL-60 cells were found to accumulate large quantities of vitamin C (ascorbate) after activation of the NADPH oxidase by phorbol esters (PMA). This increase in vitamin C transport is due to the generation of superoxide and subsequent oxidation of ascorbate to dehydroascorbate (DHA) which is preferentially taken up by the cells. We found that zinc reversibly inhibits both PMA-stimulated ascorbate uptake and superoxide generation with a half-maximal effect at 20 microM of free zinc ions. Higher residual extracellular ascorbate concentrations were measured with increasing zinc concentrations, indicating that less ascorbate was oxidized and taken up by the cells. When the fluorescent dye diSC3(5) was used to monitor shifts in membrane potential, we found that depolarization with PMA was prolonged after preincubation of the cells with zinc. Suppression of the respiratory burst as well as inhibition of the uptake of the antioxidant vitamin C may disturb the balance between oxidative damage of invading particles and antioxidant protection in activated neutrophils.     

G to C transition at position −173 of MIF gene of the recipient is associated with reduced relapse rates after allogeneic stem cell transplantation

Pro-inflammatory and dendritic cell-activating properties of macrophage migration inhibitory factor (MIF) suggest a potentially important role for MIF in alloantigen-specific immune responses after allogeneic stem cell transplantation (allo-SCT). We tested whether MIF −173 G/C gene polymorphism of donor or patient had impacts on the outcomes after allo-SCT. Four hundred and fifty-four donor–patient pairs were genotyped and mortality, relapse, and development of complications were analyzed. Patient but not donor MIF −173*C allele was associated with improved overall survival (OS) (5 years: 60.8% versus 46.3%, p = 0.042) and disease free survival (DFS) (5 years: 55.4% versus 39.5%; p = 0.014) due to a reduction in relapse (day 2000: 22.8% versus 42.0% p = 0.006) but not due to decreased transplantation-related mortality (TRM) (p = 0.44). Multivariate analysis proved patient −173*C allele as an independent factor for reducing relapse after allo-SCT (p = 0.023). Subgroup analysis showed a clear MIF −173*C allele-related reduction in relapse for those patients who did not receive T cell depleted (TCD) SCT (p = 0.01) in contrast to patients receiving TCD SCT (p = 0.20). In summary, patient MIF −173*C allele may be linked to specific, yet unrevealed functions in tumor biology and graft versus leukemia and lymphoma effects and potentially presents a novel prognostic marker for patient-tailored counseling and therapy in allo-SCT.     

Molecular characterization of the pericentric inversion that causes differences between chimpanzee chromosome 19 and human chromosome 17

A comparison of the human genome with that of the chimpanzee is an attractive approach to attempts to understand the specificity of a certain phenotype's development. The two karyotypes differ by one chromosome fusion, nine pericentric inversions, and various additions of heterochromatin to chromosomal telomeres. Only the fusion, which gave rise to human chromosome 2, has been characterized at the sequence level. During the present study, we investigated the pericentric inversion by which chimpanzee chromosome 19 differs from human chromosome 17. Fluorescence in situ hybridization was used to identify breakpoint-spanning bacterial artificial chromosomes (BACs) and plasmid artificial chromosomes (PACs). By sequencing the junction fragments, we localized breakpoints in intergenic regions rich in repetitive elements. Our findings suggest that repeat-mediated nonhomologous recombination has facilitated inversion formation. No addition or deletion of any sequence element was detected at the breakpoints or in the surrounding sequences. Next to the break, at a distance of 10.2-39.1 kb, the following genes were found: NGFR and NXPH3 (on human chromosome 17q21.3) and GUC2D and ALOX15B (on human chromosome 17p13). The inversion affects neither the genomic structure nor the gene-activity state with regard to replication timing of these genes.     

Rotifers in aging research: use of rotifers to test various theories of aging

Four theories of aging are discussed to examine how effectively they might explain the aging process in rotifers. One of the early theories, the rate of living theory of aging can perhaps be discounted. Although the theory predicts that increased biological energy expenditure, in the form of increased activity or reproduction, would lead to a shorter lifespan, these predictions are not born out by experimental evidence. At the whole animal level, a case can be made for a theory of programmed aging, where the end of reproduction signals the end of the lifespan. Support for this view comes from the observation that lifespan is positively correlated with reproductive parameters, that treatments that extend lifespan usually act to extend the reproductive period, and that the end of reproduction is associated with high mortality and senescent biochemical changes. Two molecular theories of aging are also discussed; the free radical theory of aging and the calcium theory of aging. These theories point to the fact that molecular damage accumulates and that calcium influx increases in the course of aging. When free radical buildup or calcium homeostasis is reduced, lifespan is extended. A molecular explanation of aging does not necessarily exclude the idea of programmed aging. It is probable that an eventual understanding of the aging process will rest on both a physiological and molecular basis.