Binding specificities of the lectins PNA, WGA and UEA I to polyvinylchloride-adsorbed glycosphingolipids

Abnormal B cell glycosylation in autoimmunity: A new potential treatment strategy

Systemic lupus erythematosus (SLE) and primary Sjögren’s syndrome (pSS) are two autoimmune diseases characterised by the production of pathogenic autoreactive antibodies. Their aetiology is poorly understood. Nevertheless, they have been shown to involve several factors, such as infections and epigenetic mechanisms. They also likely involve a physiological process known as glycosylation. Both SLE T cell markers and pSS-associated autoantibodies exhibit abnormal glycosylation. Such dysregulation suggests that defective glycosylation may also occur in B cells, thereby modifying their behaviour and reactivity. This study aimed to investigate B cell subset glycosylation in SLE, pSS and healthy donors and to extend the glycan profile to serum proteins and immunoglobulins. We used optimised lectin-based tests to demonstrate specific glycosylation profiles on B cell subsets that were specifically altered in both diseases. Compared to the healthy donor B cells, the SLE B cells exhibited hypofucosylation, whereas only the pSS B cells exhibited hyposialylation. Additionally, the SLE B lymphocytes had more galactose linked to N-acetylglucosamine or N-acetylgalactosamine (Gal-GlcNAc/Gal-GalNAc) residues on their cell surface markers. Interestingly, some similar alterations were observed in serum proteins, including immunoglobulins. These findings indicate that any perturbation of the natural glycosylation process in B cells could result in the development of pathogenic autoantibodies. The B cell glycoprofile can be established as a preferred biomarker for characterising pathologies and adapted therapeutics can be used for patients if there is a correlation between the extent of these alterations and the severity of the autoimmune diseases.

Generation of glycans depleted decellularized porcine pericardium, using digestive enzymatic supplements and enzymatic mixtures for food industry

BACKGROUND

Xenogeneic pericardium has been used largely for various applications in cardiovascular surgery. Nevertheless, xenogeneic pericardial patches fail mainly due to their antigenic components. The xenoantigens identified as playing a major role in recipient immune response are the Galα1-3Gal (α-Gal) epitope, the non-human sialic acid N-glycolylneuraminic acid (Neu5Gc), and the porcine SDa antigen, associated with both proteins and lipids. The reduction in glycans from porcine pericardium might hinder or reduce the immunogenicity of xenogeneic scaffolds.

METHODS

Decellularized porcine pericardia were further treated at different time points and dilutions with digestive enzymatic supplements and enzymatic mixtures applied for food industry, for the removal of potentially immunogenic carbohydrates. Carbohydrates removal was investigated using up to 8 different lectin stains for the identification of N- and O-glycosylations, as well as glycolipids. Histoarchitectural changes in the ECM were assessed using Elastica van Gieson stain, whereas changes in mechanical properties were investigated via uniaxial tensile test and burst pressure test.

RESULTS

Tissues after enzymatic treatments showed a dramatic decrease in lectin stainings in comparison to tissues which were only decellularized. Histological assessment revealed cell-nuclei removal after decellularization. Some of the enzymatic treatments induced elastic lamellae disruption. Tissue strength decreased after enzymatic treatment; however, treated tissues showed values of burst pressure higher than physiological transvalvular pressures.

CONCLUSIONS

The application of these enzymatic treatments for tissue deglycosylation is totally novel, low cost, and appears to be very efficient for glycan removal. The immunogenic potential of treated tissues will be further investigated in subsequent studies, in vitro and in vivo.

Xenopus epidermal and endodermal epithelia as models for mucociliary epithelial evolution, disease, and metaplasia

The Xenopus embryonic epidermis is a powerful model to study mucociliary biology, development, and disease. Particularly, the Xenopus system is being used to elucidate signaling pathways, transcription factor functions, and morphogenetic mechanisms regulating cell fate specification, differentiation and cell function. Thereby, Xenopus research has provided significant insights into potential underlying molecular mechanisms for ciliopathies and chronic airway diseases. Recent studies have also established the embryonic epidermis as a model for mucociliary epithelial remodeling, multiciliated cell trans-differentiation, cilia loss, and mucus secretion. Additionally, the tadpole foregut epithelium is lined by a mucociliary epithelium, which shows remarkable features resembling mammalian airway epithelia, including its endodermal origin and a variable cell type composition along the proximal-distal axis. This review aims to summarize the advantages of the Xenopus epidermis for mucociliary epithelial biology and disease modeling. Furthermore, the potential of the foregut epithelium as novel mucociliary model system is being highlighted. Additional perspectives are presented on how to expand the range of diseases that can be modeled in the frog system, including proton pump inhibitor-associated pneumonia as well as metaplasia in epithelial cells of the airway and the gastroesophageal region.

Altered glycosylation of glycodelin in endometrial carcinoma

Glycodelin is a major glycoprotein expressed in reproductive tissues, like secretory and decidualized endometrium. It has several reproduction related functions that are dependent on specific glycosylation, but it has also been found to drive differentiation of endometrial carcinoma cells toward a less malignant phenotype. Here we aimed to elucidate whether the glycosylation and function of glycodelin is altered in endometrial carcinoma as compared with a normal endometrium. We carried out glycan structure analysis of glycodelin expressed in HEC-1B human endometrial carcinoma cells (HEC-1B Gd) by mass spectrometry glycomics strategies. Glycans of HEC-1B Gd were found to comprise a typical mixture of high-mannose, hybrid, and complex-type N-glycans, often containing undecorated LacNAc (Galβ1-4GlcNAc) antennae. However, several differences, as compared with previously reported glycan structures of normal human decidualized endometrium-derived glycodelin isoform, glycodelin-A (GdA), were also found. These included a lower level of sialylation and more abundant poly-LacNAc antennae, some of which are fucosylated. This allowed us to select lectins that showed different binding to these classes of glycodelin. Despite the differences in glycosylation between HEC-1B Gd and GdA, both showed similar inhibitory activity on trophoblast cell invasion and peripheral blood mononuclear cell proliferation. For the detection of cancer associated glycodelin, we established a novel in situ proximity-ligation based histochemical staining method using a specific glycodelin antibody and UEAI lectin. We found that the UEAI reactive glycodelin was abundant in endometrial carcinoma, but virtually absent in normal endometrial tissue even when glycodelin was strongly expressed. In conclusion, we established a histochemical staining method for the detection of endometrial carcinoma-associated glycodelin and showed that this specific glycodelin is exclusively expressed in cancer, not in normal endometrium. Similar methods can be used for studies of other glycoproteins.

Crumbs3 regulates the expression of glycosphingolipids on the plasma membrane to promote colon cancer cell migration

The cell polarity regulator Crumbs3 (Crb3) promotes colon cancer cell migration and metastasis. However, the underlying mechanism of cancer cell migration regulated by Crb3 has not been fully elucidated. Here, we demonstrated that Crb3 is associated with cell migration by regulating glycosphingolipid (GSL) expression in human colon cancer cells. Crb3-knockout (KO) cells showed a remarkable increase in ganglioside GM3 (GM3) on the cell surface. Reduced migration by Crb3-KO cells was restored by forced expression of both Crb3 and Neuraminidase3 (Neu3). Immunofluorescent staining revealed that most Crb3 is colocalized with the recycling endosome marker Rab11. These findings show that Crb3 may promote colon cancer cell migration by regulating the expression of GSLs on the cell surface.

Increased galactose expression and enhanced clearance in patients with low von Willebrand factor

Glycan determinants on von Willebrand factor (VWF) play critical roles in regulating its susceptibility to proteolysis and clearance. Abnormal glycosylation has been shown to cause von Willebrand disease (VWD) in a number of different mouse models. However, because of the significant technical challenges associated with accurate assessment of VWF glycan composition, the importance of carbohydrates in human VWD pathogenesis remains largely unexplored. To address this, we developed a novel lectin-binding panel to enable human VWF glycan characterization. This methodology was then used to study glycan expression in a cohort of 110 patients with low VWF compared with O blood group-matched healthy controls. Interestingly, significant interindividual heterogeneity in VWF glycan expression was seen in the healthy control population. This variation included terminal sialylation and ABO(H) blood group expression on VWF. Importantly, we also observed evidence of aberrant glycosylation in a subgroup of patients with low VWF. In particular, terminal α(2-6)-linked sialylation was reduced in patients with low VWF, with a secondary increase in galactose (Gal) exposure. Furthermore, an inverse correlation between Gal exposure and estimated VWF half-life was observed in those patients with enhanced VWF clearance. Together, these findings support the hypothesis that loss of terminal sialylation contributes to the pathophysiology underpinning low VWF in at least a subgroup of patients by promoting enhanced clearance. In addition, alterations in VWF carbohydrate expression are likely to contribute to quantitative and qualitative variations in VWF levels in the normal population. This trial was registered at www.clinicaltrials.gov as #NCT03167320.

A conserved major facilitator superfamily member orchestrates a subset of O-glycosylation to aid macrophage tissue invasion

Aberrant display of the truncated core1 O-glycan T-antigen is a common feature of human cancer cells that correlates with metastasis. Here we show that T-antigen in Drosophila melanogaster macrophages is involved in their developmentally programmed tissue invasion. Higher macrophage T-antigen levels require an atypical major facilitator superfamily (MFS) member that we named Minerva which enables macrophage dissemination and invasion. We characterize for the first time the T and Tn glycoform O-glycoproteome of the Drosophila melanogaster embryo, and determine that Minerva increases the presence of T-antigen on proteins in pathways previously linked to cancer, most strongly on the sulfhydryl oxidase Qsox1 which we show is required for macrophage tissue entry. Minerva's vertebrate ortholog, MFSD1, rescues the minerva mutant's migration and T-antigen glycosylation defects. We thus identify a key conserved regulator that orchestrates O-glycosylation on a protein subset to activate a program governing migration steps important for both development and cancer metastasis.

Engineered Glycocalyx Regulates Stem Cell Proliferation in Murine Crypt Organoids

At the base of the intestinal crypt, long-lived Lgr5⁺ stem cells are intercalated by Paneth cells that provide essential niche signals for stem cell maintenance. This unique epithelial anatomy makes the intestinal crypt one of the most accessible models for the study of adult stem cell biology. The glycosylation patterns of this compartment are poorly characterized, and the impact of glycans on stem cell differentiation remains largely unexplored. We find that Paneth cells, but not Lgr5⁺ stem cells, express abundant terminal N-acetyllactosamine (LacNAc). Employing an enzymatic method to edit glycans in cultured crypt organoids, we assess the functional role of LacNAc in the intestinal crypt. We discover that blocking access to LacNAc on Paneth cells leads to hyperproliferation of the neighboring Lgr5⁺ stem cells, which is accompanied by the downregulation of genes that are known as negative regulators of proliferation.

Dengue Virus NS1 Disrupts the Endothelial Glycocalyx, Leading to Hyperpermeability

Dengue is the most prevalent arboviral disease in humans and a major public health problem worldwide. Systemic plasma leakage, leading to hypovolemic shock and potentially fatal complications, is a critical determinant of dengue severity. Recently, we and others described a novel pathogenic effect of secreted dengue virus (DENV) non-structural protein 1 (NS1) in triggering hyperpermeability of human endothelial cells in vitro and systemic vascular leakage in vivo. NS1 was shown to activate toll-like receptor 4 signaling in primary human myeloid cells, leading to secretion of pro-inflammatory cytokines and vascular leakage. However, distinct endothelial cell-intrinsic mechanisms of NS1-induced hyperpermeability remained to be defined. The endothelial glycocalyx layer (EGL) is a network of membrane-bound proteoglycans and glycoproteins lining the vascular endothelium that plays a key role in regulating endothelial barrier function. Here, we demonstrate that DENV NS1 disrupts the EGL on human pulmonary microvascular endothelial cells, inducing degradation of sialic acid and shedding of heparan sulfate proteoglycans. This effect is mediated by NS1-induced expression of sialidases and heparanase, respectively. NS1 also activates cathepsin L, a lysosomal cysteine proteinase, in endothelial cells, which activates heparanase via enzymatic cleavage. Specific inhibitors of sialidases, heparanase, and cathepsin L prevent DENV NS1-induced EGL disruption and endothelial hyperpermeability. All of these effects are specific to NS1 from DENV1-4 and are not induced by NS1 from West Nile virus, a related flavivirus. Together, our data suggest an important role for EGL disruption in DENV NS1-mediated endothelial dysfunction during severe dengue disease.

Dengue is the most prevalent mosquito-borne disease in humans and represents a major public health problem worldwide. Leakage of fluids and molecules from the bloodstream into tissues can lead to shock and potentially death and is a critical determinant of dengue disease severity. Recently, we showed that a secreted protein from dengue virus (DENV)-infected cells, non-structural protein 1 (NS1), can trigger increased leakage both in human cell culture and mouse models. It has been shown that NS1 can activate toll-like receptor 4 on peripheral blood mononuclear cells, leading to secretion of pro-inflammatory cytokines that can result in vascular leak. However, the mechanism by which NS1 triggers hyperpermeability directly in human endothelial cells remained undefined. The endothelial glycocalyx layer (EGL) is a network of membrane-bound molecules that lines endothelial cells on the inside of blood vessels, helping to regulate proper vascular function. Here, we show that DENV NS1 can disrupt the integrity of the EGL, inducing breakdown and shedding of key components. This is mediated by NS1 induction of cellular enzymes (e.g., sialidases, heparanase, and cathepsin L) that contribute to EGL alterations. Inhibitors that block these enzymes prevent both EGL disruption and endothelial permeability. These effects were all demonstrated to be specific to NS1 from DENV serotypes 1–4, as NS1 from the related West Nile Virus did not produce EGL alterations or increased leakage. Our study suggests a novel role for DENV NS1 in inducing EGL disruption to increase fluid leakage during severe dengue disease.

Evaluation of the role of the GPIb-IX-V receptor complex in development of the platelet storage lesion

BACKGROUND AND OBJECTIVES

In mice, loss of sialic acid resulting in shedding of glycoprotein (GP) Ibα and GPV has been linked to platelet survival. The aim of this study was to determine whether loss of sialic acid and the GPIb-IX-V complex contributes to development of the platelet storage lesion (PSL) in human platelet concentrates (PCs).

MATERIALS AND METHODS

PCs (stored in plasma (with or without Mirasol treatment); PAS-C or PAS-E) were stored at room temperature. Flow cytometry was used to monitor membrane expression of the GPIb-IX-V complex, CD62P, surface glycans and PS exposure. The functionality of stored platelets was determined employing aggregometry and ristocetin-induced VWF binding.

RESULTS

Storage time of PCs in blood banks is limited to 7 days. During this time period, a minor but gradually increasing subpopulation of GPIbα-negative platelets was observed. Also, ristocetin-induced VWF binding was impaired in a small population of platelets. Mean surface expression of GPIbα and GPV remained stable until day 9, whereas CD62P expression increased; also a rapid decrease in ADP-induced aggregation was observed for PAS-C, PAS-E and Mirasol-treated PCs. Upon prolonged storage (>9 days), a slow decline in surface expression of GPIbα and GPV was observed; no major changes were observed in surface sialylation with the exception of Mirasol-treated platelets.

CONCLUSION

In a small population of stored platelets, changes in GPIbα occur from day 2 onwards. Loss of sialic acid and subsequent shedding of GPIbα and GPV is not an early event during the development of the PSL.

Characterization of Cryptopygus antarcticus endo-β-1,4-glucanase from Bombyx mori expression systems

Endo-β-1,4-glucanase (CaCel) from Antarctic springtail, Cryptopygus antarcticus, a cellulase with high activity at low temperature, shows potential industrial use. To obtain sufficient active cellulase for characterization, CaCel gene was expressed in Bombyx mori-baculovirus expression systems. Recombinant CaCel (rCaCel) has been expressed in Escherichia coli (Ec-CaCel) at temperatures below 10°C, but the expression yield was low. Here, rCaCel with a silkworm secretion signal (Bm-CaCel) was successfully expressed and secreted into pupal hemolymph and purified to near 90% purity by Ni-affinity chromatography. The yield and specific activity of rCaCel purified from B. mori were estimated at 31 mg/l and 43.2 U/mg, respectively, which is significantly higher than the CaCel yield obtained from E. coli (0.46 mg/l and 35.8 U/mg). The optimal pH and temperature for the rCaCels purified from E. coli and B. mori were 3.5 and 50°C. Both rCaCels were active at a broad range of pH values and temperatures, and retained more than 30% of their maximal activity at 0°C. Oligosaccharide structural analysis revealed that Bm-CaCel contains elaborated N- and O-linked glycans, whereas Ec-CaCel contains putative O-linked glycans. Thermostability of Bm-CaCel from B. mori at 60°C was higher than that from E. coli, probably due to glycosylation.

Determination of multivalent protein-ligand binding kinetics by second-harmonic correlation spectroscopy

Binding kinetics of the multivalent proteins peanut agglutinin (PnA) and cholera toxin B subunit (CTB) to a GM1-doped 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipid bilayer were investigated by both second-harmonic correlation spectroscopy (SHCS) and a traditional equilibrium binding isotherm. Adsorption and desorption rates, as well as binding affinity and binding free energy, for three bulk protein concentrations were determined by SHCS. For PnA binding to GM1, the measured adsorption rate decreased with increasing bulk PnA concentration from (3.7 ± 0.3) × 10(6) M(-1)·s(-1) at 0.43 μM PnA to (1.1 ± 0.1) × 10(5) M(-1)·s(-1) at 12 μM PnA. CTB-GM1 exhibited a similar trend, decreasing from (1.0 ± 0.1) × 10(9) M(-1)·s(-1) at 0.5 nM CTB to (3.5 ± 0.2) × 10(6) M(-1)·s(-1) at 240 nM CTB. The measured desorption rates in both studies did not exhibit any dependence on initial protein concentration. As such, 0.43 μM PnA and 0.5 nM CTB had the strongest measured binding affinities, (3.7 ± 0.8) × 10(9) M(-1) and (2.8 ± 0.5) × 10(13) M(-1), respectively. Analysis of the binding isotherm data suggests there is electrostatic repulsion between protein molecules when PnA binds GM1, while CTB-GM1 demonstrates positive ligand-ligand cooperativity. This study provides additional insight into the complex interactions between multivalent proteins and their ligands and showcases SHCS for examining these complex yet technologically important protein-ligand complexes used in biosensors, immunoassays, and other biomedical diagnostics.

TMEM115 is an integral membrane protein of the Golgi complex involved in retrograde transport

Searching and evaluating the Human Protein Atlas for transmembrane proteins enabled us to identify an integral membrane protein, TMEM115, that is enriched in the Golgi complex. Biochemical and cell biological analysis suggested that TMEM115 has four candidate transmembrane domains located in the N-terminal region. Both the N- and C-terminal domains are oriented towards the cytoplasm. Immunofluorescence analysis supports that TMEM115 is enriched in the Golgi cisternae. Functionally, TMEM115 knockdown or overexpression delays Brefeldin-A-induced Golgi-to-ER retrograde transport, phenocopying cells with mutations or silencing of the conserved oligomeric Golgi (COG) complex. Co-immunoprecipitation and in vitro binding experiments reveals that TMEM115 interacts with the COG complex, and might self-interact to form dimers or oligomers. A short region (residues 206–229) immediately to the C-terminal side of the fourth transmembrane domain is both necessary and sufficient for Golgi targeting. Knockdown of TMEM115 also reduces the binding of the lectins peanut agglutinin (PNA) and Helix pomatia agglutinin (HPA), suggesting an altered O-linked glycosylation profile. These results establish that TMEM115 is an integral membrane protein of the Golgi stack regulating Golgi-to-ER retrograde transport and is likely to be part of the machinery of the COG complex.

Biocompatible carbohydrate-functionalized stainless steel surfaces: a new method for passivating biomedical implants

A convenient method for passivating and functionalizing stainless steel is described. Several methods of coating stainless steel (SS) samples with silica were investigated and of these methods, a thin (less than 15 nm thick) layer of silica created by atomic layer deposition (ALD) was found to give superior performance in electrochemical testing. These interfaces were then used as a platform for further functionalization with molecules of biological interest. Specifically, the SS samples were functionalized with biologically significant carbohydrates [N-acetyl-D-glucosamine (GlcNAc) and D-galactose (Gal)] that contain trialkoxysilane derivatives as chemical handles for linking to the surface. The presence and biological availability of these moieties on the silica coated SS were confirmed by XPS analysis and an enzyme-linked lectin assay (ELLA) using complementary lectins that specifically recognize the surface-bound carbohydrate. This method has the potential of being adapted to the functionalization of stainless steel biomedical implants with other biologically relevant carbohydrates.

Development of lipid particles targeted via sugar-lipid conjugates as novel nuclear gene delivery system

Efficient nuclear gene delivery is essential for successful gene therapy. This study developed a novel system that mimics the mechanism of nuclear entry of adenovirus (Ad) by means of a Multifunctional Envelope-type Nano Device (MEND). In this system, plasmid DNA (pDNA) was condensed with polycation, followed by encapsulation in a lipid membrane. To target MEND to the nuclear pore complex (NPC), sugar served as a NPC-mediated nuclear targeting device was modified on the surface of the lipid envelope. This was accomplished via synthesis of a sugar-cholesterol conjugate. After binding of the MEND to the NPC, the pDNA core was transferred into the nucleus in conjunction with a breakdown of the lipid envelope. Sugar-modified MEND showed higher transfection efficiency compared with unmodified MEND, in non-dividing and dividing cells. Confocal microscopy confirmed that nuclear transfer of pDNA was improved by sugar modification of MEND. Furthermore, destabilization of the lipid envelope significantly enhanced transfection activity: therefore, nuclear-delivery efficiency was closely related to lipid envelope stability. Moreover, quantitative evaluation of cellular uptake and nuclear transfer processes by real-time PCR confirmed that the surface sugars affected nuclear transfer, but not cellular uptake. In summary, a novel system for the nuclear delivery of pDNA was successfully developed by using a sugar-modified MEND and by optimizing the lipid envelope stability.

Glycosylation patterns are sexually dimorphic throughout development of the olfactory system in Manduca sexta

In the moth Manduca sexta, development of the adult olfactory system depends on complex interactions between olfactory receptor neurons in the antenna, antennal-lobe neurons in the brain, and several classes of glial cells. As one approach to characterizing molecules that may play roles in these interactions, we used lectins to screen antennae and antennal lobes at different stages of adult development. We find that each of the major neural cell types has a distinct pattern of labeling by lectins. Effects of enzymatic and other treatments on lectin labeling lead us to conclude that the predominant lectin ligands are: glycosphingolipids and an O-linked, fucose-containing glycoprotein on axons of olfactory receptor neurons, O-linked glycoproteins on antennal-lobe neurons, and N-linked glycoproteins on all classes of glial cells in the primary olfactory pathway. Wheat germ agglutinin labels all olfactory axons uniformly during much of development, but labeling becomes restricted to the pheromone-responsive olfactory receptor neurons in the adult male. Succinylated WGA reveals differences in these axon classes earlier, as glomerului develop from protoglomeruli. The adult female displays a less pronounced difference in labeling of axons targeting ordinary and sexually dimorphic glomeruli. Differences in labeling of receptor axons targeted to ordinary and sexually dimorphic glomeruli may be correlated with differences in function or connectivity in different regions of the antennal lobe.

Piezoelectric Mass-Sensing Devices as Biosensors-An Alternative to Optical Biosensors?

In the early days of electronic communication-as a result of the limited number of quartz resonators available-frequency adjustment was accomplished by a pencil mark depositing a foreign mass layer on the crystal. In 1959, Sauerbrey showed that the shift in resonance frequency of thickness-shear-mode resonators is proportional to the deposited mass. This was the starting point for the development of a new generation of piezoelectric mass-sensitive devices. However, it was the development of new powerful oscillator circuits that were capable of operating thickness shear mode resonators in fluids that enabled this technique to be introduced into bioanalytic applications. In the last decade adsorption of biomolecules on functionalized surfaces turned in to one of the paramount applications of piezoelectric transducers. These applications include the study of the interaction of DNA and RNA with complementary strands, specific recognition of protein ligands by immobilized receptors, the detection of virus capsids, bacteria, mammalian cells, and last but not least the development of complete immunosensors. Piezoelectric transducers allow a label-free detection of molecules; they are more than mere mass sensors since the sensor response is also influenced by interfacial phenomena, viscoelastic properties of the adhered biomaterial, surface charges of adsorbed molecules, and surface roughness. These new insights have recently been used to investigate the adhesion of cells, liposomes, and proteins onto surfaces, thus allowing the determination of the morphological changes of cells as a response to pharmacological substances and changes in the water content of biopolymers without employing labor-intense techniques. However, the future will show whether the quartz-crystal microbalance will assert itself against established label-free sensor devices such as surface plasmon resonance spectroscopy and interferometry.

Quantitative determination of globotriaosylceramide by immunodetection of glycolipid-bound recombinant verotoxin B subunit

An assay for the neutral glycosphingolipid, globotriaosylceramide (Galalpha1-4Galbeta1-4Glcbeta1-1Cer; GL-3), was developed based on the B subunit of Escherichia coli verotoxin (VTB). The VTB gene was isolated, overexpressed in E. coli, and purified by a single immunoaffinity chromatographic step using a monoclonal anti-VTB IgG-agarose column. Purified recombinant VTB was used to develop an enzyme-linked immunosorbent assay (ELISA) to determine the GL-3 concentrations in plasma and tissue extracts from normal individuals and patients and mice with alpha-galactosidase A deficiency (human Fabry disease). The mean (+/-1 SD) plasma GL-3 concentrations in affected male and female heterozygotes with Fabry disease were 12.6 +/- 3.7 and 1.1 +/- 0.7 microg/ml, respectively, whereas normal individuals had 0.9 +/- 0.4 microg/ml. In 5- to 6-month-old mice with alpha-galactosidase A deficiency, the average GL-3 concentrations in spleen, kidney, liver, heart, and plasma were 2790 +/- 400, 1100 +/- 93, 378 +/- 67, and 196 +/- 28 ng/mg wet wt and 5. 1 +/- 2.0 microg/ml, respectively, whereas tissues from wild-type mice contained very low or undetectable GL-3 levels. This ELISA assay should prove useful for determining the GL-3 levels, as well as for monitoring the effectiveness of therapeutic endeavors in patients with Fabry disease.

Quantitative measurements of the interaction between monosialoganglioside monolayers and wheat germ agglutinin (WGA) by a quartz-crystal microbalance

Monosialogangliosides (GM1, GM2, GM3 and GM4) were reconstituted in lipid monolayers at the air-water interface. The binding amounts and the initial binding rates of wheat germ agglutinin (WGA) to the monosialoganglioside monolayers were quantitatively studied by use of a quartz-crystal microbalance (QCM). A QCM was horizontally attached to the monolayer from the air phase, and the binding behavior (mass increase) was followed by the frequency decrease of the QCM. WGA binding affinities for the ganglioside monolayers were influenced by hydrophilic head groups of lipid matrices, densities of gangliosides, and sequences of oligosaccharide in gangliosides. Binding of WGA to the gangliosides reconstituted in a phosphatidylcholine (sphingomyelin and distearoylphosphatidylcholine) matrix was strongly suppressed, but not in a neutral glycolipids (GlcCer, GalCer, and LacCer), dipalmitoylphosphatidylethanolamine, and dipalmitoylphosphatidylethanolamine matrix. WGA showed high affinity for monolayers containing 20 mol% gangliosides, but only low affinity for 100% ganglioside monolayers. WGA preferably binds to gangliosides in the following sequence: GM3 > GM4 >> GM2 = GM1. No affinities of WGA for GM2 and GM1 were observed. The combined techniques of monolayer and QCM have the advantages of investigating recognition properties of gangliosides.

High-resolution thin-layer chromatography of gangliosides

In this review an updated overview of current improvements on thin-layer chromatography (TLC) of gangliosides over the past decade is provided. Basic general techniques and special advice is given for successful separation of glycosphingolipids. New approaches concerning continuous and multiple development, and several preparative TLC methods are also included. Emphasis is placed on TLC immunostaining and related techniques, i.e. practical applications of carbohydrate-specific antibodies, toxins and bacteria, viruses, lectins and eukaryotic cells. Thus, this review on ganglioside TLC summarizes its power as an analytical tool for a wide range of purposes.

Study of lectin-ganglioside interactions by high-performance liquid affinity chromatography

A high-performance affinity column containing immobilized modified GM1 (lyso-GM1) was used to study the binding of an endogenous human brain lectin (HBL) in comparison with other carbohydrate-binding proteins. The proteins are previously converted into biotinylated derivatives. Detection of biotinylated proteins in the eluates by a microtitre plate assay ensures good sensitivity. The maximum binding capacity of the adsorbent for HBL is obtained in Tris buffer supplemented with beta-mercaptoethanol. The binding is inhibitable by specific sugar. It is concluded that the use of immobilized glycolipids in analytical high-performance liquid affinity chromatographic methods may serve as models in the study of interactions between gangliosides and carbohydrate-binding proteins.

Developmental changes in neutral glycosphingolipids of mouse placenta

The mammalian placenta is a unique organ for the study of developmental changes. Placentas of laboratory animals such as the mouse allow for the determination of the exact stage of pregnancy, which cannot be achieved with human placenta. In this study, neutral glycosphingolipids were isolated from mouse (inbred strain C57BL/6) placentas, from day 10 to day 18 of gestation, and were separated by high performance thin layer chromatography. Densitometric measurements after orcinol staining showed, at day 10 of gestation, the presence of mono-, tetra-, tri- and dihexosylceramide in decreasing quantities, as well as four unidentified spots. On day 12, the glycosphingolipid composition changed with the disappearance of the unidentified spots and the appearance of an orcinol positive migrating similarly to the Forssman antigen; no further changes occurred between days 12 and 18 of gestation. The identity of the Forssman-like glycosphingolipid with the Forssman antigen was established by binding of 125I labelled Helix pomatia agglutinin (alpha-GalNAc specific) to glycosphingolipids separated on high performance thin layer chromatography plates, and by the reaction of the isolated glycosphingolipid with a monoclonal anti-Forssman antibody. The appearance of the Forssman antigen at day 12 of gestation coincided with the day of final maturation of the mouse placenta and subsequent cessation of growth, suggesting a possible role of the glycosphingolipid during embryonic development.

Serine protease immunohistochemistry and lectin histochemistry in the small intestine of weaned and unweaned pigs

The distribution of goblet cells containing serine protease and of those binding the lectin Ulex europaeus agglutinin-1 (UEA-1) in the pig small intestine is altered during the period after weaning. Goblet cells exhibiting binding of other lectins were not altered. These alterations and other changes in goblet cells may reflect the effects of a hypersensitivity response to dietary antigen.

Requirement for sialic acid on the endothelial ligand of a lymphocyte homing receptor

The entry of blood-borne lymphocytes into most secondary lymphoid organs is initiated by a highly specific adhesive interaction with the specialized cuboidal endothelial cells of high endothelial venules (HEV). The adhesive receptors on lymphocytes that dictate interactions with HEV in different lymphoid organs are called homing receptors, signifying their critical role in controlling organ-selective lymphocyte migration. Considerable work has established that the mouse peripheral lymph node homing receptor (pnHR), defined by the mAb MEL-14, functions as a lectin-like adhesive protein. We have previously shown that sialidase treatment of peripheral lymph node (PN) HEV abrogates lymphocyte attachment to the HEV both in vivo and in vitro. We extend this evidence by demonstrating that Limax agglutinin (LA), a sialic acid-specific lectin, when reacted with HEV exposed in cryostat-cut tissue sections, blocks lymphocyte attachment to PN HEV and, unexpectedly, to the HEV of Peyer's patches (PP) as well. Using a recombinant form of the pnHR as a histochemical probe for its cognate adhesive site (HEV-ligand) on PN HEV, we demonstrate that both sialidase and Limax agglutinin functionally inactive this ligand. It is concluded that the requirement for sialic acid is at the level of the pnHR interaction with its HEV ligand. A distinct sialyloligosaccharide may encode the recognition determinant of a PP HEV ligand.

Specific staining on thin-layer chromatograms of glycosphingolipids of neolacto series and gangliosides with a terminal N-acetylneuraminyl residue by different procedures with wheat germ agglutinin

Sensitive staining methods with wheat germ agglutinin were developed for the detection of glycosphingolipids of neolacto series (A) and gangliosides with a terminal N-acetylneuraminyl residue (B) on thin-layer chromatograms. (A) Neolacto series glycosphingolipids were treated by beta-galactosidase on the chromatograms in the presence of taurodeoxycholate. Then the chromatograms were incubated with biotinated wheat germ agglutinin followed by incubation with a complex of avidin and biotinated horseradish peroxidase, and the reaction was detected by 4-chloro-1-naphthol. In the case of gangliosides, sialidase treatment on the chromatograms was performed before the beta-galactosidase treatment. The sensitivity of the method for Lc3Cer, nLc4Cer, sialyl-nLc4Cer, and sialyl-nLc6Cer was 4 pmol, 7.6 pmol, 2.9 pmol and 1.4 pmol, respectively. (B) The gangliosides on the chromatograms were oxidized by periodic acid and reduced by NaBH4. Then the chromatograms were stained with wheat germ agglutinin as mentioned above. As little as 0.5 pmol of GM3, NeuAc-nLc4Cer, and NeuAc-nLc6Cer was detected by this method, whereas the detected limits for these gangliosides were 10 pmol, 10 pmol and 2 pmol, respectively, when periodate oxidation was omitted. GM4, GD3 and GD1a were an order less reactive than GM3, GM2, GM1 or GD1b were not stained under the same condition. In contrast to NeuAc-containing gangliosides, any gangliosides with N-glycolylneuraminic acid were not stained by the method in (B).

Serological activity against galactosyl-alpha(1-3)galactose in sera from patients with several kinetoplastida infections

Using rabbit erythrocyte-derived neutral glycosphingolipids enriched for a defined ceramide pentasaccharide as antigens, we have detected elevated anti-galactosyl-alpha(1-3)galactose (anti-G alpha G) antibody values in patients with American cutaneous leishmaniasis (ACL), chronic Chagas' disease, and Trypanosoma rangeli infections compared with normal subjects or with patients suffering from any of 15 other infectious diseases. The specificity of the G alpha G antibodies was determined by inhibition enzyme-linked immunosorbent assays, which revealed that several alpha-galactosyl- but not beta-galactosyl-bearing sugars blocked absorption of G alpha G antibodies to the specific antigen used. G alpha G antibodies were mainly distributed between immunoglobulin classes G and M in three Kinetoplastida infections studied, with a lower increase in reactivity detected in immunoglobulin A. Absorption of highly reactive G alpha G antibodies with purified murine laminin and nidogen, two basement membrane proteins, almost abolished G alpha G reactivity, suggesting the identity of anti-G alpha G with laminin and nidogen antibodies previously reported as elevated in Kinetoplastida infections. In ACL, G alpha G antibodies were detected in 71% of patients having skin lesions with a clinical evolution time of 0.5 month. This percentage increased with the time of evolution of skin lesions, reaching 93% in lesions older than 3 months, and tended to decrease inversely to the induration diameter in the skin leishmanin test. It is proposed that similar epitopes may exist on kinetoplast protozoa and that the determination of G alpha G antibodies may be a highly sensitive assay for the detection of humoral responses to Kinetoplastida infections.