Galectin-8 in IgA Nephritis: Decreased Binding of IgA by Galectin-8 Affinity Chromatography and Associated Increased Binding in Non-IgA Serum Glycoproteins

Background Immunoglobulin A nephritis (IgAN) is the most common primary glomerulonephritis worldwide. It is caused by accumulation of IgA1-containing immune complexes in the kidney resulting in renal failure, which is thought to be due to altered glycosylation of IgA with a decrease of 2-3-sialylated galactosides (NeuAc alpha 2-3Gal). less thanbrgreater than less thanbrgreater thanPurpose The purpose of this study was to analyze whether altered glycosylation of IgA would lead to an altered binding to galectin-8, an endogenous lectin with strong affinity for 2-3-sialylated galactosides. Galectins are a family of beta-galactoside-binding proteins; by binding various glycoproteins, they play important roles in the regulation of cellular functions in inflammation and immunity. Hence, an altered binding of IgA to galectin-8 could lead to pathologic immune functions, such as glomerulonephritis. less thanbrgreater than less thanbrgreater thanMethods Affinity chromatography of serum glycoproteins on the human sialogalactoside-binding lectin galectin-8N permitted quantitation of bound and unbound fractions, including IgA. less thanbrgreater than less thanbrgreater thanResults Analysis of similar to 100 IgA nephritis sera showed that the galectin-8N unbound fraction of IgA increased compared to similar to 100 controls, consistent with the known loss of galactosylation. A subgroup of similar to 15% of the IgAN patients had a ratio of galectin-8 bound/unbound IgA andlt;0.09, not found for any of the controls. Unexpectedly, the galectin-8N-binding fraction of serum glycoproteins other than IgA increased in the sera of IgAN patients but not in controls, suggesting a previously unrecognized change in this disease. less thanbrgreater than less thanbrgreater thanConclusion This is the first study that relates a galectin, an endogenous lectin family, to IgA nephritis and thus should stimulate new avenues of research into the pathophysiology of the disease.Funding Agencies|Swedish Research Council (Vetenskapsradet)|2008-3356|Swedish Foundation for Swedish Research|FFL4|Swedish Healthcare System (ALF)||Region Skane||</p

Identification of a new European rabbit IgA with a serine-rich hinge region

<div><p>In mammals, the most striking IgA system belongs to Lagomorpha. Indeed, 14 IgA subclasses have been identified in European rabbits, 11 of which are expressed. In contrast, most other mammals have only one IgA, or in the case of hominoids, two IgA subclasses. Characteristic features of the mammalian IgA subclasses are the length and amino acid sequence of their hinge regions, which are often rich in Pro, Ser and Thr residues and may also carry Cys residues. Here, we describe a new IgA that was expressed in New Zealand White domestic rabbits of <i>IGHV</i>a1 allotype. This IgA has an extended hinge region containing an intriguing stretch of nine consecutive Ser residues and no Pro or Thr residues, a motif exclusive to this new rabbit IgA. Considering the amino acid properties, this hinge motif may present some advantage over the common IgA hinge by affording novel functional capabilities. We also sequenced for the first time the IgA14 CH2 and CH3 domains and showed that IgA14 and IgA3 are expressed.</p></div

Pathogenesis of Henoch-Schönlein purpura nephritis

The severity of renal involvement is the major factor determining the long-term outcome of children with Henoch-Schönlein purpura (HSP) nephritis (HSPN). Approximately 40% children with HSP develop nephritis, usually within 4 to 6 weeks after the initial onset of the typical purpuric rashes. Although the pathogenetic mechanisms are still not fully delineated, several studies suggest that galactose-deficient IgA1 (Gd-IgA1) is recognized by anti-glycan antibodies, leading to the formation of the circulating immune complexes and their mesangial deposition that induce renal injury in HSPN

Uptake of Aortic 18F-FDG Is Correlated with Low-Density Lipoprotein Cholesterol and Leptin in a General Population

Objective: This study investigated the relationship between aortic 18F-fluoro-2-deoxy-D-glucose (18F-FDG) uptake and clinical and laboratory findings related to atherosclerosis in a general population. Copyright:Methods: 18F-FDG uptake in the ascending aorta was measured on the positron emission tomography/computed tomography (PET/CT) scans of 211 Japanese adults. The maximum target-to-background ratio (TBR) was compared with clinical and laboratory atherosclerosis findings.Results: By multivariate regression analysis adjusted for age and sex, TBR-ascending aorta (TBR-A) was significantly correlated with various clinical and laboratory parameters, such as body mass index, log visceral fat area, low-density lipoprotein cholesterol (LDL-C), log fasting immunoreactive insulin, log homeostasis model assessment of insulin resistance, log total adiponectin and log-leptin, in all subjects. Furthermore, by multivariate linear regression analysis adjusted for confounding factors, TBR-A was significantly correlated with LDL-C (β=0.001, p=0.03) and log-leptin (β =0.336, p<0.01) in all subjects.Conclusion: TBR-A was significantly correlated with LDL-C and log-leptin independent from confounding factors. Our results suggest that aortic 18F-FDG uptake is a good marker of atherosclerosis, even in a general population

"Internal residue loss": rearrangements occurring during the fragmentation of carbohydrates derivatized at the reducing terminus.

Rearrangement reactions involving migration of fucose and, occasionally, other residues have been found in the CID spectra of [M + H]+ and [M + 2H]2+ ions, but not [M + Na]+ ions, generated from several O-linked carbohydrates and milk sugars derivatized at their reducing termini with aromatic amines such as 2-aminobenzamide. Such rearrangements, which are similar to those reported by other investigators from several underivatized carbohydrates and glycosides, cause an apparent loss of sugar residues from within a carbohydrate chain and can produce ambiguous results during spectral interpretation. A mechanism, involving initial protonation of the amine nitrogen atom of the derivative, is proposed to account for the formation of the observed ions

Glycoproteins: rapid sequencing technology for N-linked and GPI anchor glycans

Recent advances in oligosaccharide sequencing technology have made routine glycan analysis of glycoproteins and the glycan moieties of glycosylphosphatidylinositol (GPI) anchors a real possibility for many laboratories. The strategies described here have been developed specifically to address the need for a rapid and robust method of glycan analysis which can be applied routinely to microgram levels of glycoproteins with the minimum requirement for specialised equipment or expertise. This strategy also allows the possibility of isolating individual sugars of particular interest for more detailed analysis. We discuss the N~glycosy[ation ofCD48. IgO and IgA I, the Fab and Fc fragments of [gO and also the small (S) and middle (M) glycoproteins of the hepatitiS B virus coat protein. We describe the analysis of the major O·glycans of neutrophil gelatinase B and also present a novel method for analysing the gIycans attached to the GPI anchor of a variant surface glycoprotein of Trypcl1Z0S()mlllmlcei directly from a Western blot. The underlying aim of these analytical strategies is to obtain oligosaccharide sequencing data which. in combination with oligosaccharide and protein structural data. can be visualised in a molecular model. In this way, oligo saccharides can be viewed in the context of the proteins to which they are attached. and some insight can be gained into the roles which sugars might play in the structure and function of the glycoproteins

O-glycan analysis of natural human neutrophil gelatinase B using a combination of normal phase-HPLC and online tandem mass spectrometry: implications for the domain organization of the enzyme.

Gelatinase B is a matrix metalloproteinase (MMP-9) expressed under strict control by many cell types including neutrophils, monocytes, macrophages, and tumor cells. MMP-9 is a key mediator in the physiological maintenance of the extracellular matrix both in tissue remodeling and development, while uncontrolled enzyme activity contributes to pathologies such as cancer and inflammation. Neutrophils release MMP-9 from granules in response to IL-8 stimulation. Human MMP-9 has three potential N-linked glycosylation sites and contains a Ser/Pro/Thr rich domain, known as the type V collagen-like domain, which is expected to be heavily O-glycosylated. Indeed, approximately 85% of the total sugars on human neutrophil MMP-9 are O-linked. This paper presents the detailed analysis of picomole amounts of these O-glycans using a novel HPLC-based strategy for O-glycan analysis that provides linkage and arm specific information in addition to monosaccharide sequence. The initial structural assignments were confirmed using HPLC with online MS/MS fragmentation analysis. Twelve sugars were identified that contained from two to nine monosaccharide residues. Most of these contained type 2 core structures with Galbeta1-4GlcNAc (N-acetyl lactosamine) extensions, with or without sialic acid or fucose. The O-glycans were modeled using the oligosaccharide structural database. On the basis of the structure of gelatinase A (MMP-2), a model of MMP-9 suggests that the type V collagen-like domain in gelatinase B is located on a loop remote from the active site. Fourteen potential O-glycosylation sites are multiply presented on this loop of 52 amino acids. Many of the O-glycans identified contain terminal galactose residues that may provide recognition epitopes. Importantly, heavy glycosylation of this loop region, absent in gelatinase A, has considerable implications for the domain organization of MMP-9