The α1,6-fucosyltransferase gene (fut8) from the Sf9 lepidopteran insect cell line: insights into fut8 evolution

Assembly and synthesis of the extracellular matrix in brown algae

In brown algae, the extracellular matrix (ECM) and its constitutive polymers play crucial roles in specialized functions, including algal growth and development. In this review we offer an integrative view of ECM construction in brown algae. We briefly report the chemical composition of its main constituents, and how these are interlinked in a structural model. We examine the ECM assembly at the tissue and cell level, with consideration on its structure in vivo and on the putative subcellular sites for the synthesis of its main constituents. We further discuss the biosynthetic pathways of two major polysaccharides, alginates and sulfated fucans, and the progress made beyond the candidate genes with the biochemical validation of encoded proteins. Key enzymes involved in the elongation of the glycan chains are still unknown and predictions have been made at the gene level. Here, we offer a re-examination of some glycosyltransferases and sulfotransferases from published genomes. Overall, our analysis suggests novel investigations to be performed at both the cellular and biochemical levels. First, to depict the location of polysaccharide structures in tissues. Secondly, to identify putative actors in the ECM synthesis to be functionally studied in the future.

Involvement of the α-helical and Src homology 3 domains in the molecular assembly and enzymatic activity of human α1,6-fucosyltransferase, FUT8

BACKGROUND

Previous structural analyses showed that human α1,6-fucosyltransferase, FUT8 contains a catalytic domain along with two additional domains, N-terminal α-helical domain and C-terminal Src homology 3 domain, but these domains are unique to FUT8 among glycosyltransferases. The role that these domains play in formation of the active form of FUT8 has not been investigated. This study reports on attempts to determine the involvement of these domains in the functions of FUT8.

METHODS

Based on molecular modeling, the domain mutants were constructed by truncation and site-directed mutagenesis, and were heterologously expressed in Sf21 or COS-1 cells. The mutants were analyzed by SDS-PAGE and assayed for enzymatic activity. In vivo cross-linking experiments by introducing disulfide bonds were also carried out to examine the orientation of the domains in the molecular assembly.

RESULTS

Mutagenesis and molecular modeling findings suggest that human FUT8 potentially forms homodimer in vivo via intermolecular hydrophobic interactions involving α-helical domains. Truncation or site-directed mutagenesis findings indicated that α-helical and SH3 domains are all required for enzymatic activity. In addition, in vivo cross-linking experiments clearly indicated that the SH3 domain located in close proximity to the α-helical domain in an intermolecular manner.

CONCLUSIONS

α-Helical and SH3 domains are required for a fully active enzyme, and are also involved in homophilic dimerization, which probably results in the formation of the active form of human FUT8.

GENERAL SIGNIFICANCE

α-Helical and SH3 domains, which are not commonly found in glycosyltransferases, play roles in the formation of the functional quaternary structure of human FUT8.

Characterization of MiFUT11 from Mangifera indica L.: A functional core α1,3-fucosyltransferase potentially involved in the biosynthesis of immunogenic carbohydrates in mango fruit

In higher plants, asparagine-linked oligosaccharides (N-glycans) in glycoproteins carry unique carbohydrate epitopes, namely, a core α1,3-fucose and/or a β1,2-xylose, which are common determinants responsible for the cross-reactivity of plant glycoproteins due to their strong immunogenicity. While these determinants and the relevant genes have been well characterized for herbaceous plants, information concerning whether many food plants cross-react with airborne pollens is not available. In this paper, we report on the characterization of a novel core α1,3-fucosyltransferase gene identified from Mangifera indica L., one of the major plants potentially related to food allergy. Based on sequence information of plant homologues, we amplified a candidate cDNA (MiFUT11) from pericarp tissue. An in vitro assay demonstrated that the recombinant MiFUT11 protein transfers a fucose unit onto both non-fucosylated and core α1,6-fucosylated oligosaccharides. A glycoform analysis using MALDI-TOF mass spectrometry showed that the introduction of the MiFUT11 cDNA increased the production of a core α1,3- and α1,6-fucosylated pauci-mannosidic oligosaccharide in Spodoptera Sf21 cells. Our findings suggest that MiFUT11 is a functional core α1,3-fucosyltransferase gene that is involved in the assembly of cross-reactive N-glycans in mango fruit.

How Fucose of Blood Group Glycotopes Programs Human Gut Microbiota

Formation of appropriate gut microbiota is essential for human health. The first two years of life is the critical period for this process. Selection of mutualistic microorganisms of the intestinal microbiota is controlled by the FUT2 and FUT3 genes that encode fucosyltransferases, enzymes responsible for the synthesis of fucosylated glycan structures of mucins and milk oligosaccharides. In this review, the mechanisms of the selection and maintenance of intestinal microorganisms that involve fucosylated oligosaccharides of breast milk and mucins of the newborn's intestine are described. Possible reasons for the use of fucose, and not sialic acid, as the major biological signal for the selection are also discussed.

Unveiling the Impact of the Genomic Architecture on the Evolution of Vertebrate microRNAs

Eukaryotic genomes frequently exhibit interdependency between transcriptional units, as evidenced by regions of high gene density. It is well recognized that vertebrate microRNAs (miRNAs) are usually embedded in those regions. Recent work has shown that the genomic context is of utmost importance to determine miRNA expression in time and space, thus affecting their evolutionary fates over long and short terms. Consequently, understanding the inter- and intraspecific changes on miRNA genomic architecture may bring novel insights on the basic cellular processes regulated by miRNAs, as well as phenotypic evolution and disease-related mechanisms.

The underestimated N-glycomes of lepidopteran species

BACKGROUND

Insects are significant to the environment, agriculture, health and biotechnology. Many of these aspects display some relationship to glycosylation, e.g., in case of pathogen binding or production of humanised antibodies; for a long time, it has been considered that insect N-glycosylation potentials are rather similar and simple, but as more species are glycomically analysed in depth, it is becoming obvious that there is indeed a large structural diversity and interspecies variability.

METHODS

Using an off-line LC-MALDI-TOF MS approach, we have analysed the N-glycomes of two lepidopteran species (the cabbage looper Trichoplusia ni and the gypsy moth Lymantria dispar) as well as of the commonly-used T. ni High Five cell line.

RESULTS

We detected not only sulphated, glucuronylated, core difucosylated and Lewis-like antennal fucosylated structures, but also the zwitterion phosphorylcholine on antennal GlcNAc residues, a modification otherwise familiar from nematodes; in L. dispar, N-glycans with glycolipid-like antennae containing α-linked N-acetylgalactosamine were also revealed.

CONCLUSION

The lepidopteran glycomes analysed not only display core α1,3-fucosylation, which is foreign to mammals, but also up to 5% anionic and/or zwitterionic glycans previously not found in these species.

SIGNIFICANCE

The occurrence of anionic and zwitterionic glycans in the Lepidoptera data is not only of glycoanalytical and evolutionary interest, but is of biotechnological relevance as lepidopteran cell lines are potential factories for recombinant glycoprotein production.

Mammalian α-1,6-Fucosyltransferase (FUT8) Is the Sole Enzyme Responsible for the N-Acetylglucosaminyltransferase I-independent Core Fucosylation of High-mannose N-Glycans

Understanding the biosynthetic pathway of protein glycosylation in various expression cell lines is important for controlling and modulating the glycosylation profiles of recombinant glycoproteins. We found that expression of erythropoietin (EPO) in a HEK293S N-acetylglucosaminyltransferase I (GnT I)(-/-) cell line resulted in production of the Man5GlcNAc2 glycoforms, in which more than 50% were core-fucosylated, implicating a clear GnT I-independent core fucosylation pathway. Expression of GM-CSF and the ectodomain of FcγIIIA receptor led to ∼30% and 3% core fucosylation, suggesting that the level of core fucosylation also depends on the nature of the recombinant proteins. To elucidate the GnT I-independent core fucosylation pathway, we generated a stable HEK293S GnT I(-/-) cell line with either knockdown or overexpression of FUT8 by a highly efficient lentivirus-mediated gene transfer approach. We found that the EPO produced from the FUT8 knockdown cell line was the pure Man5GlcNAc2 glycoform, whereas that produced from the FUT8-overexpressing cell line was found to be fully core-fucosylated oligomannose glycan (Man5GlcNAc2Fuc). These results provide direct evidence that FUT8, the mammalian α1,6-fucosyltransferase, is the sole enzyme responsible for the GnT I-independent core fucosylation pathway. The production of the homogeneous core-fucosylated Man5GlcNAc2 glycoform of EPO in the FUT8-overexpressed HEK293S GnT I(-/-) cell line represents the first example of production of fully core-fucosylated high-mannose glycoforms.

The fucomic potential of mosquitoes: Fucosylated N-glycan epitopes and their cognate fucosyltransferases

Fucoconjugates are key mediators of protein-glycan interactions in prokaryotes and eukaryotes. As examples, N-glycans modified with the non-mammalian core α1,3-linked fucose have been detected in various organisms ranging from plants to insects and are immunogenic in mammals. The rabbit polyclonal antibody raised against plant horseradish peroxidase (anti-HRP) is able to recognize the α1,3-linked fucose epitope and is also known to specifically stain neural tissues in the fruit fly Drosophila melanogaster. In this study, we have detected and localized the anti-HRP cross-reactivity in another insect species, the malaria mosquito vector Anopheles gambiae. We were able to identify and structurally elucidate fucosylated N-glycans including core mono- and difucosylated structures (responsible for anti-HRP cross reactivity) as well as a Lewis-type antennal modification on mosquito anionic N-glycans by applying enzymatic and chemical treatments. The three mosquito fucosyltransferase open reading frames (FucT6, FucTA and FucTC) required for the in vivo biosynthesis of the fucosylated N-glycan epitopes were identified in the Anopheles gambiae genome, cloned and recombinantly expressed in Pichia pastoris. Using a robust MALDI-TOF MS approach, we characterised the activity of the three recombinant fucosyltransferases in vitro and demonstrate that they share similar enzymatic properties as compared to their homologues from D. melanogaster and Apis mellifera. Thus, not only do we confirm the neural reactivity of anti-HRP in a mosquito species, but also demonstrate enzymatic activity for all its α1,3- and α1,6-fucosyltransferase homologues, whose specificity matches the results of glycomic analyses.