Pyridoxamine protects proteins from functional damage by 3-deoxyglucosone: mechanism of action of pyridoxamine

Pyridoxamine (PM) is a promising drug candidate for treatment of diabetic nephropathy. The therapeutic effect of PM has been demonstrated in multiple animal models of diabetes and in phase II clinical trials. However, the mechanism of PM therapeutic action is poorly understood. One potential mechanism is scavenging of pathogenic reactive carbonyl species (RCS) found to be elevated in diabetes. We have suggested previously that the pathogenicity of RCS methylglyoxal (MGO) may be due to modification of critical arginine residues in matrix proteins and interference with renal cell-matrix interactions. We have also shown that this MGO effect can be inhibited by PM (Pedchenko et al. (2005) Diabetes 54, 2952-2960). These findings raised the questions of whether the effect is specific to MGO, whether other structurally different physiological RCS can act via the same mechanism, and whether their action is amenable to PM protection. In the present study, we have shown that the important physiological RCS 3-deoxyglucosone (3-DG) can damage protein functionality, including the ability of collagen IV to interact with glomerular mesangial cells. We have also demonstrated that PM can protect against 3-DG-induced protein damage via a novel mechanism that includes transient adduction of 3-DG by PM followed by irreversible PM-mediated oxidative cleavage of 3-DG. Our results suggest that, in diabetic nephropathy, the therapeutic effect of PM is achieved, in part, via protection of renal cell-matrix interactions from damage by a variety of RCS. Our data emphasize the potential importance of the contribution by 3-DG, along with other more reactive RCS, to this pathogenic mechanism.     

Goodpasture antigen-binding protein and its spliced variant, ceramide transfer protein, have different functions in the modulation of apoptosis during zebrafish development

Human Goodpasture antigen-binding protein (GPBP) is an atypical protein kinase that phosphorylates the Goodpasture auto-antigen, the alpha3 chain of collagen IV. The COL4A3BP gene is alternatively spliced producing two protein isoforms: GPBP and GPBPDelta26. The latter lacks a serine-rich domain composed of 26 amino acid residues. Both isoforms also function as ceramide transfer proteins (CERT). Here, we explored the function of Gpbp and GpbpDelta26/CERT during embryogenesis in zebrafish. We cloned both splice variants of the zebrafish gene and found that they are differentially expressed during development. We used antisense oligonucleotide-mediated loss-of-function and synthetic mRNA-based gain-of-function approaches. Our results show that the loss-of-function phenotype is linked to cell death, evident primarily in the muscle of the somites, extensive loss of myelinated tracks, and brain edema. These results indicate that disruption of the nonvesicular ceramide transport is detrimental to normal embryonic development of somites and brain because of increased apoptosis. Moreover, this phenotype is mediated by Gpbp but not GpbpDelta26/CERT, suggesting that Gpbp is an important factor for normal skeletal muscle and brain development.     

Identification of noncollagenous sites encoding specific interactions and quaternary assembly of alpha 3 alpha 4 alpha 5(IV) collagen: implications for Alport gene therapy

Defective assembly of alpha 3 alpha 4 alpha 5(IV) collagen in the glomerular basement membrane causes Alport syndrome, a hereditary glomerulonephritis progressing to end-stage kidney failure. Assembly of collagen IV chains into heterotrimeric molecules and networks is driven by their noncollagenous (NC1) domains, but the sites encoding the specificity of these interactions are not known. To identify the sites directing quaternary assembly of alpha 3 alpha 4 alpha 5(IV) collagen, correctly folded NC1 chimeras were produced, and their interactions with other NC1 monomers were evaluated. All alpha1/alpha 5 chimeras containing alpha 5 NC1 residues 188-227 replicated the ability of alpha 5 NC1 to bind to alpha3NC1 and co-assemble into NC1 hexamers. Conversely, substitution of alpha 5 NC1 residues 188-227 by alpha1NC1 abolished these quaternary interactions. The amino-terminal 58 residues of alpha3NC1 encoded binding to alpha 5 NC1, but this interaction was not sufficient for hexamer co-assembly. Because alpha 5 NC1 residues 188-227 are necessary and sufficient for assembly into alpha 3 alpha 4 alpha 5 NC1 hexamers, whereas the immunodominant alloantigenic sites of alpha 5 NC1 do not encode specific quaternary interactions, the findings provide a basis for the rational design of less immunogenic alpha 5(IV) collagen constructs for the gene therapy of X-linked Alport patients.     

Signaling mechanisms of secretin receptor

Secretin, a 27-amino acid gastrointestinal peptide, was initially discovered based on its activities in stimulating pancreatic juice. In the past 20 years, secretin was demonstrated to exhibit pleiotropic functions in many different tissues and more importantly, its role as a neuropeptide was substantiated. To carry out its activities in the central nervous system and in peripheral organs, secretin interacts specifically with one known receptor. Secretin receptor, a member of guanine nucleotide-binding protein (G protein)-coupled receptor (GPCR) in the secretin/VIP/glucagon subfamily, possesses the characteristics of GPCR with seven conserved transmembrane domains, a relatively large amino-terminal extracellular domain and an intracellular carboxyl terminus. The structural features and signal transduction pathways of the secretin receptor in various tissues are reviewed in this article.     

Phylogeny of Laniarius: molecular data reveal L. liberatus synonymous with L. erlangeri and "plumage coloration" as unreliable morphological characters for defining species and species groups

Laniarius is one of the larger genera within the avian bush-shrike radiation, the family Malaconotidae. Fairly homogenous by size and shape but highly variable by colours, these have been classified mainly on basis of plumage colours. In the present study, which is the first taxon-dense analysis of the genus Laniarius based on molecular sequence data (nuclear BRM15 intron-15, and mitochondrial ND2 and ATPase6 genes), we investigate interrelationships between 16 species and 34 subspecies of Laniarius. Altogether 2094 bp were aligned and subjected to maximum likelihood and Bayesian inference analyses. Results strongly support the monophyly of Laniarius, and place it close to Chlorophoneus, but without outlining a precise sister-group. In a generally well-resolved phylogeny of Laniarius, L. leucorhynchus and L. atrococcineus constitute deep branches and the remaining species form five clades which are not concordant with previously defined superspecies. The black and white boubous belong to two different clades. L. aethiopicus appears polyphyletic and our results support the resurrection of Laniarius major, Laniarius erlangeri and Laniarius sublacteus. We also find that L. liberatus, described in 1991 based on the only known live individual, is identified as an unusual colour morph from L. erlangeri. The black boubous are not monophyletic; L. funebris and L. leucorhynchus appear as isolated species whereas L. poensis and L. fuelleborni are sister-taxa. We recovered the polyphyly of crimson boubous and new hypotheses on their relationships have been generated. Overall, the variation in pigments and patterns does not follow phylogenetic lineages. The plumage coloration could be thoroughly subject to modification and it could not reflect exactly colour plumages of the parents. From then on, the plumage coloration appears as an unreliable morphological character for defining species and species groups.     

Hydrodynamic and sediment transport modeling with emphasis on shallow-water,vegetated areas (lakes,reservoirs, estuaries and lagoons)

Modeling capabilities for shallow, vegetated, systems are reviewed to assess hydrodynamic, wind and wave, submersed plant friction, and sediment transport aspects. Typically, ecosystems with submersed aquatic vegetation are relatively shallow, physically stable and of moderate hydrodynamic energy. Wind-waves are often important to sediment resuspension. These are open systems that receive flows of material and energy to various degrees around their boundaries. Bed shear-stress, erosion, light extinction and submersed aquatic vegetation influence each other. Therefore, it is difficult to uncouple these components in model systems. Spatial changes in temperature, salinity, dissolved and particulate material depend on hydrodynamics. Water motions range from wind-wave scales on the small end, which might be important to erosion, to sub-tidal or seasonal scales on the large end, which are generally important to flushing. Seagrass modifies waves and, therefore, affects the relationships among the non-dimensional scaling parameters commonly used in wave analysis. Seagrass shelters the bed, often causing aggradation and changes in grain size, while increasing total resistance to flow. Hydrodynamic friction can not be well characterized by a single-parameter equation in seagrass beds, and models need appropriate enhancement when applied to these systems.Presently, modeling is limited by computational power, which is, however, improving. Other limitations include information on seagrass effects expressed in frictional resistance to currents, bed-sheltering, and wave damping in very shallow water under conditions of both normal and high bed roughness. Moreover, quantitative information on atmospheric friction and shear stress in shallow water and seagrass areas are needed. So far, various empirical equations have been used with wind or wave forcing to describe resuspension in shallow water. Although these equations have been reasonably successful in predicting suspended sediment concentrations, they require site-specific data. More detailed laboratory and field measurements are needed to improve the resuspension equations and model formulation pertaining to seagrass beds.     

Association of pneumococcal carriage in infants with the risk of carriage among their contacts in Nha Trang,Vietnam: A nested cross-sectional survey

BackgroundInfants are at highest risk of pneumococcal disease. Their added protection through herd effects is a key part in the considerations on optimal pneumococcal vaccination strategies. Yet, little is currently known about the main transmission pathways to this vulnerable age group. Hence, this study investigates pneumococcal transmission routes to infants in the coastal city of Nha Trang, Vietnam.Methods and findingsIn October 2018, we conducted a nested cross-sectional contact and pneumococcal carriage survey in randomly selected 4- to 11-month-old infants across all 27 communes of Nha Trang. Bayesian logistic regression models were used to estimate age specific carriage prevalence in the population, a proxy for the probability that a contact of a given age could lead to pneumococcal exposure for the infant. We used another Bayesian logistic regression model to estimate the correlation between infant carriage and the probability that at least one of their reported contacts carried pneumococci, controlling for age and locality. In total, 1,583 infants between 4 and 13 months old participated, with 7,428 contacts reported. Few infants (5%, or 86 infants) attended day care, and carriage prevalence was 22% (353 infants). Most infants (61%, or 966 infants) had less than a 25% probability to have had close contact with a pneumococcal carrier on the surveyed day. Pneumococcal infection risk and contact behaviour were highly correlated: If adjusted for age and locality, the odds of an infant’s carriage increased by 22% (95% confidence interval (CI): 15 to 29) per 10 percentage points increase in the probability to have had close contact with at least 1 pneumococcal carrier. Moreover, 2- to 6-year-old children contributed 51% (95% CI: 39 to 63) to the total direct pneumococcal exposure risks to infants in this setting. The main limitation of this study is that exposure risk was assessed indirectly by the age-dependent propensity for carriage of a contact and not by assessing carriage of such contacts directly.ConclusionsIn this study, we observed that cross-sectional contact and infection studies could help identify pneumococcal transmission routes and that preschool-age children may be the largest reservoir for pneumococcal transmission to infants in Nha Trang, Vietnam.