Antibodies that recognize bisected complex N-glycans on cell surface glycoproteins can be made in mice lacking N-acetylglucosaminyltransferase III

In Situ Fucosylation of the Wnt Co-receptor LRP6 Increases Its Endocytosis and Reduces Wnt/β-Catenin Signaling

Wnt/β-catenin signaling regulates critical, context-dependent transcription in numerous physiological events. Among the well-documented mechanisms affecting Wnt/β-catenin activity, modification of N-glycans by L-fucose is the newest and the least understood. Using a combination of Chinese hamster ovary cell mutants with different fucosylation levels and cell-surface fucose editing (in situ fucosylation [ISF]), we report that α(1-3)-fucosylation of N-acetylglucosamine (GlcNAc) in the Galβ(1-4)-GlcNAc sequences of complex N-glycans modulates Wnt/β-catenin activity by regulating the endocytosis of low-density lipoprotein receptor-related protein 6 (LRP6). Pulse-chase experiments reveal that ISF elevates endocytosis of lipid-raft-localized LRP6, leading to the suppression of Wnt/β-catenin signaling. Remarkably, Wnt activity decreased by ISF is fully reversed by the exogenously added fucose. The combined data show that in situ cell-surface fucosylation can be exploited to regulate a specific signaling pathway via endocytosis promoted by a fucose-binding protein, thereby linking glycosylation of a receptor with its intracellular signaling.

The Genomes of Three Uneven Siblings: Footprints of the Lifestyles of Three Trichoderma Species

The genus Trichoderma contains fungi with high relevance for humans, with applications in enzyme production for plant cell wall degradation and use in biocontrol. Here, we provide a broad, comprehensive overview of the genomic content of these species for "hot topic" research aspects, including CAZymes, transport, transcription factors, and development, along with a detailed analysis and annotation of less-studied topics, such as signal transduction, genome integrity, chromatin, photobiology, or lipid, sulfur, and nitrogen metabolism in T. reesei, T. atroviride, and T. virens, and we open up new perspectives to those topics discussed previously. In total, we covered more than 2,000 of the predicted 9,000 to 11,000 genes of each Trichoderma species discussed, which is >20% of the respective gene content. Additionally, we considered available transcriptome data for the annotated genes. Highlights of our analyses include overall carbohydrate cleavage preferences due to the different genomic contents and regulation of the respective genes. We found light regulation of many sulfur metabolic genes. Additionally, a new Golgi 1,2-mannosidase likely involved in N-linked glycosylation was detected, as were indications for the ability of Trichoderma spp. to generate hybrid galactose-containing N-linked glycans. The genomic inventory of effector proteins revealed numerous compounds unique to Trichoderma, and these warrant further investigation. We found interesting expansions in the Trichoderma genus in several signaling pathways, such as G-protein-coupled receptors, RAS GTPases, and casein kinases. A particularly interesting feature absolutely unique to T. atroviride is the duplication of the alternative sulfur amino acid synthesis pathway.

Comparative genomics of the major fungal agents of human and animal Sporotrichosis: Sporothrix schenckii and Sporothrix brasiliensis

BACKGROUND

The fungal genus Sporothrix includes at least four human pathogenic species. One of these species, S. brasiliensis, is the causal agent of a major ongoing zoonotic outbreak of sporotrichosis in Brazil. Elsewhere, sapronoses are caused by S. schenckii and S. globosa. The major aims on this comparative genomic study are: 1) to explore the presence of virulence factors in S. schenckii and S. brasiliensis; 2) to compare S. brasiliensis, which is cat-transmitted and infects both humans and cats with S. schenckii, mainly a human pathogen; 3) to compare these two species to other human pathogens (Onygenales) with similar thermo-dimorphic behavior and to other plant-associated Sordariomycetes.

RESULTS

The genomes of S. schenckii and S. brasiliensis were pyrosequenced to 17x and 20x coverage comprising a total of 32.3 Mb and 33.2 Mb, respectively. Pair-wise genome alignments revealed that the two species are highly syntenic showing 97.5% average sequence identity. Phylogenomic analysis reveals that both species diverged about 3.8-4.9 MYA suggesting a recent event of speciation. Transposable elements comprise respectively 0.34% and 0.62% of the S. schenckii and S. brasiliensis genomes and expansions of Gypsy-like elements was observed reflecting the accumulation of repetitive elements in the S. brasiliensis genome. Mitochondrial genomic comparisons showed the presence of group-I intron encoding homing endonucleases (HE's) exclusively in S. brasiliensis. Analysis of protein family expansions and contractions in the Sporothrix lineage revealed expansion of LysM domain-containing proteins, small GTPases, PKS type1 and leucin-rich proteins. In contrast, a lack of polysaccharide lyase genes that are associated with decay of plants was observed when compared to other Sordariomycetes and dimorphic fungal pathogens, suggesting evolutionary adaptations from a plant pathogenic or saprobic to an animal pathogenic life style.

CONCLUSIONS

Comparative genomic data suggest a unique ecological shift in the Sporothrix lineage from plant-association to mammalian parasitism, which contributes to the understanding of how environmental interactions may shape fungal virulence. . Moreover, the striking differences found in comparison with other dimorphic fungi revealed that dimorphism in these close relatives of plant-associated Sordariomycetes is a case of convergent evolution, stressing the importance of this morphogenetic change in fungal pathogenesis.

Immunization with recombinantly expressed glycan antigens from Schistosoma mansoni induces glycan-specific antibodies against the parasite

Schistosomiasis caused by infection with parasitic helminths of Schistosoma spp. is a major global health problem due to inadequate treatment and lack of a vaccine. The immune response to schistosomes includes glycan antigens, which could be valuable diagnostic markers and vaccine targets. However, no precedent exists for how to design vaccines targeting eukaryotic glycoconjugates. The di- and tri-saccharide motifs LacdiNAc (GalNAcβ1,4GlcNAc; LDN) and fucosylated LacdiNAc (GalNAcβ1,4(Fucα1-3)GlcNAc; LDNF) are the basis for several important schistosome glycan antigens. They occur in monomeric form or as repeating units (poly-LDNF) and as part of a variety of different glycoconjugates. Because chemical synthesis and conjugation of such antigens is exceedingly difficult, we sought to develop a recombinant expression system for parasite glycans. We hypothesized that presentation of parasite glycans on the cell surface would induce glycan-specific antibodies. We generated Chinese hamster ovary (CHO) Lec8 cell lines expressing poly-LDN (L8-GT) and poly-LDNF (L8-GTFT) abundantly on their membrane glycoproteins. Sera from Schistosoma mansoni-infected mice were highly cross-reactive with the cells and with cell-surface N-glycans. Immunizing mice with L8-GT and L8-GTFT cells induced glycan-specific antibodies. The L8-GTFT cells induced a sustained booster response, with antibodies that bound to S. mansoni lysates and recapitulated the exquisite specificity of the anti-parasite response for particular presentations of LDNF antigen. In summary, this recombinant expression system promotes successful generation of antibodies to the glycans of S. mansoni, and it can be adapted to study the role of glycan antigens and anti-glycan immune responses in many other infections and pathologies.

Generation of anti-sulfated glycan antibodies using sulfotransferase-deficient mice

Anti-carbohydrate monoclonal antibodies (mAbs) are very useful in the functional analysis of complex carbohydrates in vivo. However, such mAbs are difficult to generate, largely because a wide variety of complex carbohydrates is intrinsically expressed in mice and rats and because the antigenicities of glycans are generally poor. In this chapter, I describe an efficient method for generating anti-carbohydrate mAbs using glycan--synthesizing enzyme-knockout mice in which the glycan structures formed by the missing enzymes should be highly antigenic. As an application of this method, I describe the generation of anti-sulfated glycan mAbs using sulfotransferase-deficient mice and the immunohistochemical detection of sulfated glycans involved in lymphocyte homing in both humans and mice.

Multiplexed analytical glycomics: rapid and confident IgG N-glycan structural elucidation

N-glycans attached to the C(H)2 domains of the Fc or the antigen binding regions of IgG play an important role in stabilizing and modulating antibody activity. Exhaustive elucidation of 32 IgG N-glycans using a combination of weak anion exchange enrichment and exoglycosidase array digestion with subsequent profiling exceeded 48 h. Pursuing increased throughput and associated structural annotation confidence, we compared the 1.7 μm hydrophilic interaction phase for UPLC with CE-LIF for the rapid and comprehensive characterization of N-glycans released from healthy human serum polyclonal IgG. Combination of the data individually generated using each technique demonstrated that complete structural annotation was possible within a total analysis time of 20 min due to the advantageous orthogonality of the separation mechanisms. The parallel use of both analytical techniques provides a powerful platform for rapid and comprehensive analysis of IgG N-glycosylation present on therapeutic antibodies or on antibodies of biomedical or pathological significance.

Novel anti-carbohydrate antibodies reveal the cooperative function of sulfated N- and O-glycans in lymphocyte homing

Cell surface glycans play pivotal roles in immune cell trafficking and immunity. Here we present an efficient method for generating anti-carbohydrate monoclonal antibodies (mAbs) using gene-targeted mice and describe critical glycans in lymphocyte homing. We immunized sulfotransferase GlcNAc6ST-1 and GlcNAc6ST-2 doubly deficient mice with sulfotransferase-overexpressing Chinese hamster ovary cells and generated two mAbs, termed S1 and S2. Both S1 and S2 bound high endothelial venules (HEVs) in the lymphoid organs of humans and wild-type mice, but not in those of doubly deficient mice. Glycan array analysis indicated that both S1 and S2 specifically bound 6-sulfo sialyl Lewis X and its defucosylated structure. Interestingly, S2 inhibited lymphocyte homing to peripheral lymph nodes by 95%, whereas S1 inhibited it by only 25%. S2 also significantly inhibited contact hypersensitivity responses and L-selectin-dependent leukocyte adhesion to HEVs. Immunohistochemical and Western blot analyses indicated that S1 preferentially bound sulfated O-glycans, whereas S2 bound both sulfated N- and O-glycans in HEVs. Furthermore, S2 strongly inhibited the N-glycan-dependent residual lymphocyte homing in mutant mice lacking sulfated O-glycans, indicating the importance of both sulfated N- and O-glycans in lymphocyte homing. Thus, the two mAbs generated by a novel method revealed the cooperative function of sulfated N- and O-glycans in lymphocyte homing and immune surveillance.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2003-2004

This review is the third update of the original review, published in 1999, on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings the topic to the end of 2004. Both fundamental studies and applications are covered. The main topics include methodological developments, matrices, fragmentation of carbohydrates and applications to large polymeric carbohydrates from plants, glycans from glycoproteins and those from various glycolipids. Other topics include the use of MALDI MS to study enzymes related to carbohydrate biosynthesis and degradation, its use in industrial processes, particularly biopharmaceuticals and its use to monitor products of chemical synthesis where glycodendrimers and carbohydrate-protein complexes are highlighted.

Convenient preparation and characterization of a monoclonal antibody for the N-linked sugar chain of a glycoprotein using a microbial endoglycosidase

We attempted to obtain the monoclonal antibody specific for the N-linked complex-type sialo-oligosaccharide in glycoproteins. We first synthesized a chimeric immunoantigen having an N-linked complex-type of oligosaccharide of glycopeptide, which was bound to a p-formylphenyl compound and conjugated with phosphatidylethanolamine dimyristoyl using the transglycosylation activity of a microbial endoglycosidase (Endo-M) and a reductive amination reaction. This preparative method was convenient and provided a good yield. By immunizing mice with this chimeric neoglycolipid, the monoclonal antibody for the complex-type of sialo-oligosaccharide was obtained in the culture fluid of the cell line even though it was relatively unstable. The monoclonal antibody reacted with various glycoproteins having complex-type sialo-oligosaccharides, but not with those having complex-type asialo-oligosaccharides and high mannose types of oligosaccharides, or with any glycosphingolipids. One of epitopes of this monoclonal antibody seemed to be an alpha-2,6-linked sialic acid at the non-reducing end of the sialo-oligosaccharide of the glycoprotein.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update covering the period 2001-2002

This review is the second update of the original review on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates that was published in 1999. It covers fundamental aspects of the technique as applied to carbohydrates, fragmentation of carbohydrates, studies of specific carbohydrate types such as those from plant cell walls and those attached to proteins and lipids, studies of glycosyl-transferases and glycosidases, and studies where MALDI has been used to monitor products of chemical synthesis. Use of the technique shows a steady annual increase at the expense of older techniques such as FAB. There is an increasing emphasis on its use for examination of biological systems rather than on studies of fundamental aspects and method development and this is reflected by much of the work on applications appearing in tabular form.