Arabidopsis XXT5 gene encodes a putative alpha-1,6-xylosyltransferase that is involved in xyloglucan biosynthesis

The function of a putative xyloglucan xylosyltransferase from Arabidopsis thaliana (At1g74380; XXT5) was studied. The XXT5 gene is expressed in all plant tissues, with higher levels of expression in roots, stems and cauline leaves. A T-DNA insertion in the XXT5 gene generates a readily visible root hair phenotype (root hairs are shorter and form bubble-like extrusions at the tip), and also causes the alteration of the main root cellular morphology. Biochemical characterization of cell wall polysaccharides isolated from xxt5 mutant seedlings demonstrated decreased xyloglucan quantity and reduced glucan backbone substitution with xylosyl residues. Immunohistochemical analyses of xxt5 plants revealed a selective decrease in some xyloglucan epitopes, whereas the distribution patterns of epitopes characteristic for other cell wall polysaccharides remained undisturbed. Transformation of xxt5 plants with a 35S::HA-XXT5 construct resulted in complementation of the morphological, biochemical and immunological phenotypes, restoring xyloglucan content and composition to wild-type levels. These data provide evidence that XXT5 is a xyloglucan alpha-1,6-xylosyltransferase, and functions in the biosynthesis of xyloglucan.     

Acquired Antibody Responses against Plasmodium vivax Infection Vary with Host Genotype for Duffy Antigen Receptor for Chemokines (DARC)

Background

Polymorphism of the Duffy Antigen Receptor for Chemokines (DARC) is associated with susceptibility to and the severity of Plasmodium vivax malaria in humans. P. vivax uses DARC to invade erythrocytes. Individuals lacking DARC are ‘resistant’ to P. vivax erythrocytic infection. However, susceptibility to P. vivax in DARC+ individuals is reported to vary between specific DARC genotypes. We hypothesized that the natural acquisition of antibodies to P. vivax blood stages may vary with the host genotype and the level of DARC expression. Furthermore, high parasitemia has been reported to effect the acquisition of immunity against pre-erythrocytic parasites. We investigated the correlation between host DARC genotypes and the frequency and magnitude of antibodies against P. vivax erythrocytic stage antigens.

Methodology/Findings

We assessed the frequencies and magnitudes of antibody responses against P. vivax and P. falciparum sporozoite and erythrocytic antigens in Colombian donors from malaria-endemic regions. The frequency and level of naturally-acquired antibodies against the P. vivax erythrocytic antigens merozoite surface protein 1 (PvMSP1) and Duffy binding protein (PvDBP) varied with the host DARC genotypes. Donors with one negative allele (FY*B/FY*Bnull and FY*A/FY*Bnull) were more likely to have anti-PvMSP1 and anti-PvDBP antibodies than those with two positive alleles (FY*B/FY*B and FY*A/FY*B). The lower IgG3 and IgG1 components of the total IgG response may account for the decreased responses to P. vivax erythrocytic antigens with FY*A/FY*B and FY*B/FY*B genotypes. No such association was detected with P. falciparum erythrocytic antigens, which does not use DARC for erythrocyte invasion.

Conclusion/Significance

Individuals with higher DARC expression, which is associated with higher susceptibility to P. vivax infection, exhibited low frequencies and magnitudes of P. vivax blood-stage specific antibody responses. This may indicate that one of the primary mechanisms by which P. vivax evades host immunity is through DARC indirectly down-regulating humoral responses against erythrocytic invasion and development.     

Early myocardial deformation changes associated to isolated obesity: a study based on 3D-wall motion tracking analysis

Obesity is considered as a strong risk factor for cardiovascular morbidity and mortality. 3D-wall motion tracking echocardiography (3D-WMT) provides information regarding different parameters of left ventricular (LV) myocardial deformation. Our aim was to assess the presence of early myocardial deformation abnormalities in nonselected obese children free from other cardiovascular risk factors. Thirty consecutive nonselected obese children and 42 healthy volunteer children were enrolled. None of them had any cardiovascular risk factor. Every subject underwent a 2D-echo examination and a 3D-WMT study. Mean age was 13.9 ± 2.56 and 13.25 ± 2.68 years in the nonobese and obese groups, respectively (59.7% and 40.3% male). Statistically significant differences were found for: interventricular septum thickness, LV posterior wall thickness, LV end-diastolic volume, LV end-systolic volume, left atrium volume, LV mass, and lateral annulus peak velocity. Regarding the results obtained by 3D-WMT assessment, all the evaluated parameters were statistically significantly different between the two groups. When the influence of obesity on the different echocardiographic variables was evaluated by means of multivariate logistic regression analysis, the strongest relationship with obesity was found for LV average circumferential strain (β-coefficient: 0.74; r(2): 0.55; P: 0.003). Thus, obesity cardiomyopathy is associated not only with structural cardiac changes, but also with myocardial deformation changes. Furthermore, this association occurs as early as in the childhood and it is independent from any other cardiovascular risk factor. The most related parameter to obesity is LV circumferential strain.     

Bongkrekic acid and atractyloside inhibits chloride channels from mitochondrial membranes of rat heart

The aim of this work was to characterize the effect of bongkrekic acid (BKA), atractyloside (ATR) and carboxyatractyloside (CAT) on single channel properties of chloride channels from mitochondria. Mitochondrial membranes isolated from a rat heart muscle were incorporated into a bilayer lipid membrane (BLM) and single chloride channel currents were measured in 250/50 mM KCl cis/trans solutions. BKA (1-100 microM), ATR and CAT (5-100 microM) inhibited the chloride channels in dose-dependent manner. The inhibitory effect of the BKA, ATR and CAT was pronounced from the trans side of a BLM and it increased with time and at negative voltages (trans-cis). These compounds did not influence the single channel amplitude, but decreased open dwell time of channels. The inhibitory effect of BKA, ATR and CAT on the mitochondrial chloride channel may help to explain some of their cellular and/or subcellular effects.     

Structural analysis of mycolic acids from phenol-degrading strain of Rhodococcus erythropolis by liquid chromatography–tandem mass spectrometry

We used reversed phase liquid chromatography?Celectrospray ionization tandem mass spectrometry for direct analysis of mycolic acids (MAs) from four different cultivations of Rhodococcus erythropolis. This technique enabled us to identify and quantify the specific molecular species of MAs directly from lipid extracts of the bacterium, including the determination of their basic characteristics such as retention time and mass spectra. We identified a total of 60 molecular species of MAs by means of LC/MS. In collision-induced dissociation tandem mass spectrometry, the [M-H]^? ions eliminated two residues, i.e., meroaldehyde and carboxylate anions containing ??-alkyl chains. The structural information from these fragment ions affords structural assignment of the mycolic acids, including the lengths and number of double bond(s). Two strains, i.e., R. erythropolis CCM 2595 and genetically modified strain CCM 2595 pSRK 21 phe were cultivated on two different substrates (phenol and phenol with addition of humic acids as a sole carbon source). The addition of humic acids showed that there is a marked increase of unsaturated mycolic acids, mostly in the range of 20?C100?%. This effect is more pronounced in the R. erythropolis CCM 2595 strain.     

Differential Binding of IgG and IgA to Mucus of the Female Reproductive Tract

Cells of the endocervix are responsible for the secretion of mucins, which provide an additional layer of protection to the female reproductive tract (FRT). This barrier is likely fortified with IgA as has previously been shown in the gastrointestinal tract and lungs of mice. Mucus associated IgA can facilitate clearance of bacteria. While a similar function for IgG has been proposed, an association with mucus has not yet been demonstrated. Here we find that IgA and IgG are differentially associated with the different types of mucus of the FRT. We observed that while both IgA and IgG are stably associated with cervical mucus, only IgG is associated with cervicovaginal mucus. These findings reveal that antibodies can bind tightly to mucus, where they can play a significant role in the fortification of the mucus barriers of the FRT. It may be possible to harness this interaction in the development of vaccines designed to protect the FRT mucosal barriers from sexually transmitted diseases such as HIV.     

Interaction with Tsg101 Is Necessary for the Efficient Transport and Release of Nucleocapsids in Marburg Virus-Infected Cells

Endosomal sorting complex required for transport (ESCRT) machinery supports the efficient budding of Marburg virus (MARV) and many other enveloped viruses. Interaction between components of the ESCRT machinery and viral proteins is predominantly mediated by short tetrapeptide motifs, known as late domains. MARV contains late domain motifs in the matrix protein VP40 and in the genome-encapsidating nucleoprotein (NP). The PSAP late domain motif of NP recruits the ESCRT-I protein tumor susceptibility gene 101 (Tsg101). Here, we generated a recombinant MARV encoding NP with a mutated PSAP late domain (rMARV_PSAPmut). rMARV_PSAPmut was attenuated by up to one log compared with recombinant wild-type MARV (rMARV_wt), formed smaller plaques and exhibited delayed virus release. Nucleocapsids in rMARV_PSAPmut-infected cells were more densely packed inside viral inclusions and more abundant in the cytoplasm than in rMARV_wt-infected cells. A similar phenotype was detected when MARV-infected cells were depleted of Tsg101. Live-cell imaging analyses revealed that Tsg101 accumulated in inclusions of rMARV_wt-infected cells and was co-transported together with nucleocapsids. In contrast, rMARV_PSAPmut nucleocapsids did not display co-localization with Tsg101, had significantly shorter transport trajectories, and migration close to the plasma membrane was severely impaired, resulting in reduced recruitment into filopodia, the major budding sites of MARV. We further show that the Tsg101 interacting protein IQGAP1, an actin cytoskeleton regulator, was recruited into inclusions and to individual nucleocapsids together with Tsg101. Moreover, IQGAP1 was detected in a contrail-like structure at the rear end of migrating nucleocapsids. Down regulation of IQGAP1 impaired release of MARV. These results indicate that the PSAP motif in NP, which enables binding to Tsg101, is important for the efficient actin-dependent transport of nucleocapsids to the sites of budding. Thus, the interaction between NP and Tsg101 supports several steps of MARV assembly before virus fission.     

Deglutarylation of glutaryl-CoA dehydrogenase by deacylating enzyme SIRT5 promotes lysine oxidation in mice

A wide range of protein acyl modifications has been identified on enzymes across various metabolic processes; however, the impact of these modifications remains poorly understood. Protein glutarylation is a recently identified modification that can be nonenzymatically driven by glutaryl-CoA. In mammalian systems, this unique metabolite is only produced in the lysine and tryptophan oxidative pathways. To better understand the biology of protein glutarylation, we studied the relationship between enzymes within the lysine/tryptophan catabolic pathways, protein glutarylation, and regulation by the deglutarylating enzyme sirtuin 5 (SIRT5). Here, we identify glutarylation on the lysine oxidation pathway enzyme glutaryl-CoA dehydrogenase (GCDH) and show increased GCDH glutarylation when glutaryl-CoA production is stimulated by lysine catabolism. Our data reveal that glutarylation of GCDH impacts its function, ultimately decreasing lysine oxidation. We also demonstrate the ability of SIRT5 to deglutarylate GCDH, restoring its enzymatic activity. Finally, metabolomic and bioinformatic analyses indicate an expanded role for SIRT5 in regulating amino acid metabolism. Together, these data support a feedback loop model within the lysine/tryptophan oxidation pathway in which glutaryl-CoA is produced, in turn inhibiting GCDH function via glutaryl modification of GCDH lysine residues and can be relieved by SIRT5 deacylation activity.     

Visualization of the phylogenetic content of five genomes using dekapentagonal maps

The methods presented here summarize phylogenetic relationships of genomes in visually appealing and informative figures. Dekapentagonal maps depict phylogenetic information for orthologous genes present in five genomes, and provide a pre-screen for putatively horizontally transferred genes. If the majority of individual gene phylogenies are unresolved, bipartition histograms provide a means of uncovering and analyzing the plurality consensus. Analyses of genomes representing five photosynthetic bacterial phyla and of the prokaryotic contributions to the eukaryotic cell illustrate the utility of the methods.     

Preparative route to N-glycolylneuraminic acid phenyl 2-thioglycoside donor and synthesis of Neu5Gc-alpha-(2-->3')-lactosamine 3-aminopropyl glycoside

The spacer-armed trisaccharide, Neu5Gc-alpha-(2-->3')-lactosamine 3-aminopropyl glycoside, was synthesized by regio- and stereoselective sialylation of the suitably protected triol acceptor, 3-trifluoroacetamidopropyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-4-O-(6-O-benzyl-beta-D-galactopyranosyl)-beta-D-glucopyranoside, with the donor methyl [phenyl 5-acetoxyacetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-alpha,beta-D-galacto-2-nonulopyranosid]onate. The donor was obtained, in turn, from methyl [phenyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-alpha,beta-D-galacto-2-nonulopyranosid]onate by N-tert-butoxycarbonylation of the acetamido group followed by total N- and O-deacetylation, per-O-acetylation, subsequent Boc group removal, and N-acetoxyacetylation.