Genomic structure and promoter analysis of the human alpha1, 6-fucosyltransferase gene (FUT8)

Exogenous L-fucose attenuates depression induced by chronic unpredictable stress: Implicating core fucosylation has an antidepressant potential

Core fucosylation is one of the most essential modifications of the N-glycans, catalyzed by α1,6-fucosyltransferase (Fut8), which transfers fucose from guanosine 5'-diphosphate (GDP)-fucose to the innermost N-acetylglucosamine residue of N-glycans in an α1-6 linkage. Our previous studies demonstrated that lipopolysaccharide (LPS) can induce a more robust neuroinflammatory response in Fut8 homozygous knockout (KO) (Fut8-/-) and heterozygous KO (Fut8+/-) mice contrasted to the wild-type (Fut8+/+) mice. Exogenous administration of L-fucose suppressed LPS-induced neuroinflammation. Numerous studies indicate that neuroinflammation plays a vital role in the development of depression. Here, we investigated whether core fucosylation regulates depression induced by chronic unpredictable stress (CUS), a well-established model for depression. Our results showed that Fut8+/- mice exhibited depressive-like behaviors and increased neuroinflammation earlier than Fut8+/+ mice. Administration of L-fucose significantly reduced CUS-induced depressive-like behaviors and pro-inflammatory cytokine levels in Fut8+/- mice. The L-fucose treatment produced antidepressant effects by attenuating the complex formation between gp130 and the interleukin-6 (IL-6) receptor and the JAK2/STAT3 signaling pathway. Notably, L-fucose treatment increased dendritic spine density and postsynaptic density protein 95 (PSD-95) expression, which were suppressed in CUS-induced depression. Furthermore, the effects of L-fucose on the CUS-induced depression were also observed in Fut8+/+ mice. Our results clearly demonstrate that L-fucose ameliorates neuroinflammation and synaptic defects in CUS-induced depression, implicating that core fucosylation has significant anti-neuroinflammatory activity and an antidepressant potential.

Roles of core fucosylation modification in immune system and diseases

Core fucosylation, catalyzed by α1,6-fucosyltransferase (FUT8), is an important N-glycosylation modification process that attaches a fucose residue via an α1,6-linkage to the core N-acetylglucosamine of N-glycans in mammals. Research over the past three decades has revealed the critical role of FUT8-mediated core fucosylation modification in various physiological and pathological processes, including cell growth, adhesion, receptor activation, antibody-dependent cellular cytotoxicity (ADCC), tumor metastasis and infections. This review discusses the immune system function involving FUT8 and the mechanisms by which core fucosylation regulates immunity and contributes to disease. A deeper understanding of these mechanisms can provide insights into cellular biology and suggest new therapeutic approaches and targets for related diseases.

The Multifaceted Role of FUT8 in Tumorigenesis: From Pathways to Potential Clinical Applications

FUT8, the sole glycosyltransferase responsible for N-glycan core fucosylation, plays a crucial role in tumorigenesis and development. Aberrant FUT8 expression disrupts the function of critical cellular components and triggers the abnormality of tumor signaling pathways, leading to malignant transformations such as proliferation, invasion, metastasis, and immunosuppression. The association between FUT8 and unfavorable outcomes in various tumors underscores its potential as a valuable diagnostic marker. Given the remarkable variation in biological functions and regulatory mechanisms of FUT8 across different tumor types, gaining a comprehensive understanding of its complexity is imperative. Here, we review how FUT8 plays roles in tumorigenesis and development, and how this outcome could be utilized to develop potential clinical therapies for tumors.

IgG1-Dominant Antibody Response Induced by Recombinant Trimeric SARS-CoV-2 Spike Protein with PIKA Adjuvant

Recombinant trimeric SARS-CoV-2 Spike protein with PIKA (polyI:C) adjuvant induces potent and durable neutralizing antibodies that protect against multiple SARS-CoV-2 variants. The immunoglobulin subclasses of viral-specific antibodies remain unknown, as do their glycosylation status on Fc regions. In this study, we analyzed immunoglobulins adsorbed by plate-bound recombinant trimeric SARS-CoV-2 Spike protein from serum of Cynomolgus monkey immunized by recombinant trimeric SARS-CoV-2 Spike protein with PIKA (polyI:C) adjuvant. The results showed that IgG1 was the dominant IgG subclass as revealed by ion mobility mass spectrometry. The average percentage of Spike protein-specific IgG1 increased to 88.3% as compared to pre-immunization. Core fucosylation for Fc glycopeptide of Spike protein-specific IgG1 was found to be higher than 98%. These results indicate that a unique Th1-biased, IgG1-dominant antibody response was responsible for the effectiveness of PIKA (polyI:C) adjuvant. Vaccine-induced core-fucosylation of IgG1 Fc region may reduce incidence of severe COVID-19 disease associated with overstimulation of FCGR3A by afucosylated IgG1.

Targeting Post-Translational Modifications to Improve Combinatorial Therapies in Breast Cancer: The Role of Fucosylation

Various tumors rely on post-translational modifications (PTMs) to promote invasiveness and angiogenesis and to reprogram cellular energetics to abate anti-cancer immunity. Among PTMs, fucosylation is a particular type of glycosylation that has been linked to different aspects of immune and hormonal physiological functions as well as hijacked by many types of tumors. Multiple tumors, including breast cancer, have been linked to dismal prognoses and increased metastatic potential due to fucosylation of the glycan core, namely core-fucosylation. Pre-clinical studies have examined the molecular mechanisms regulating core-fucosylation in breast cancer models, its negative prognostic value across multiple disease stages, and the activity of in vivo pharmacological inhibition, instructing combinatorial therapies and translation into clinical practice. Throughout this review, we describe the role of fucosylation in solid tumors, with a particular focus on breast cancer, as well as physiologic conditions on the immune system and hormones, providing a view into its potential as a biomarker for predicating or predicting cancer outcomes, as well as a potential clinical actionability as a biomarker.

Milk glycan metabolism by intestinal bifidobacteria: insights from comparative genomics

Bifidobacteria are early colonizers of the human neonatal gut and provide multiple health benefits to the infant, including inhibiting the growth of enteropathogens and modulating the immune system. Certain Bifidobacterium species prevail in the gut of breastfed infants due to the ability of these microorganisms to selectively forage glycans present in human milk, specifically human milk oligosaccharides (HMOs) and N-linked glycans. Therefore, these carbohydrates serve as promising prebiotic dietary supplements to stimulate the growth of bifidobacteria in the guts of children suffering from impaired gut microbiota development. However, the rational formulation of milk glycan-based prebiotics requires a detailed understanding of how bifidobacteria metabolize these carbohydrates. Accumulating biochemical and genomic data suggest that HMO and N-glycan assimilation abilities vary remarkably within the Bifidobacterium genus, both at the species and strain levels. This review focuses on the delineation and genome-based comparative analysis of differences in respective biochemical pathways, transport systems, and associated transcriptional regulatory networks, providing a foundation for genomics-based projection of milk glycan utilization capabilities across a rapidly growing number of sequenced bifidobacterial genomes and metagenomic datasets. This analysis also highlights remaining knowledge gaps and suggests directions for future studies to optimize the formulation of milk-glycan-based prebiotics that target bifidobacteria.

Inhibition of α(1,6)fucosyltransferase: Effects on Cell Proliferation, Migration, and Adhesion in an SW480/SW620 Syngeneic Colorectal Cancer Model

The present study explored the impact of inhibiting α(1,6)fucosylation (core fucosylation) on the functional phenotype of a cellular model of colorectal cancer (CRC) malignization formed by the syngeneic SW480 and SW620 CRC lines. Expression of the FUT8 gene encoding α(1,6)fucosyltransferase was inhibited in tumor line SW480 by a combination of shRNA-based antisense knockdown and Lens culinaris agglutinin (LCA) selection. LCA-resistant clones were subsequently assayed in vitro for proliferation, migration, and adhesion. The α(1,6)FT-inhibited SW480 cells showed enhanced proliferation in adherent conditions, unlike their α(1,6)FT-depleted SW620 counterparts, which displayed reduced proliferation. Under non-adherent conditions, α(1,6)FT-inhibited SW480 cells also showed greater growth capacity than their respective non-targeted control (NTC) cells. However, cell migration decreased in SW480 after FUT8 knockdown, while adhesion to EA.hy926 cells was significantly enhanced. The reported results indicate that the FUT8 knockdown strategy with subsequent selection for LCA-resistant clones was effective in greatly reducing α(1,6)FT expression in SW480 and SW620 CRC lines. In addition, α(1,6)FT impairment affected the proliferation, migration, and adhesion of α(1,6)FT-deficient clones SW480 and SW620 in a tumor stage-dependent manner, suggesting that core fucosylation has a dynamic role in the evolution of CRC.

Biotechnological Production of 2'-Fucosyllactose: A Prevalent Fucosylated Human Milk Oligosaccharide

Human milk oligosaccharide (HMO) is a key component of human milk carbohydrates and is closely related to the nutrition and health benefits of breastfeeding in infants. 2'-Fucosyllactose (2'-FL) is the most abundant fucosylated HMO, which has remarkable value in nutrition and medicine, such as suppressing pathogen infection, regulating intestinal flora, and boosting immunity. However, 2'-FL production via the method of extraction or chemical synthesis cannot meet its large demand, and as a result, environmentally friendly and efficient biotechnological approaches, including in vitro enzymatic synthesis and microbial cell factory production, have been developed and applied to its commercialized production. This review introduces, summarizes, and discusses the recent advances in the biotechnological production of 2'-FL. Furthermore, future research directions for the biotechnological production of 2'-FL as well as the strategies to further improve its concentration are highlighted and discussed.

True significance of N-acetylglucosaminyltransferases GnT-III, V and α1,6 fucosyltransferase in epithelial-mesenchymal transition and cancer

It is well known that numerous cancer-related changes occur in glycans that are attached to glycoproteins, glycolipids and proteoglycans on the cell surface and these changes in structure and the expression of the glycans are largely regulated by glycosyl-transferases, glycosidases, nucleotide sugars and their related genes. Such structural changes in glycans on cell surface proteins may accelerate the progression, invasion and metastasis of cancer cells. Among the over 200 known glycosyltransferases and related genes, β 1,6 N-acetylglucosaminyltransferase V (GnT-V) (the MGAT5 gene) and α 1,6 fucosyltransferase (FUT8) (the FUT8 gene) are representative enzymes in this respect because changes in glycans caused by these genes appear to be related to cancer metastasis and invasion in vitro as well as in vivo, and a number of reports on these genes in related to epithelial-mesenchymal transition (EMT) have also appeared. Another enzyme, one of the N-glycan branching enzymes, β1,4 N-acetylglucosaminyltransferase III (GnT-III) (the MGAT3 gene) has been reported to suppress EMT. However, there are intermediate states between EMT and mesenchymal-epithelial transition (MET) and some of these genes have been implicated in both EMT and MET and are also probably in an intermediate state. Therefore, it would be difficult to clearly define which specific glycosyltransferase is involved in EMT or MET or an intermediate state. The significance of EMT and N-glycan branching glycosyltransferases needs to be reconsidered and the inhibition of their corresponding genes would also be desirable in therapeutics. This review mainly focuses on GnT-III, GnT-V and FUT8, major players as N-glycan branching enzymes in cancer in relation to EMT programs, and also discusses the catalytic mechanisms of GnT-V and FUT8 whose crystal structures have now been obtained.

Core Fucosylation of Maternal Milk N-Glycan Evokes B Cell Activation by Selectively Promoting the l-Fucose Metabolism of Gut Bifidobacterium spp. and Lactobacillus spp

This study provides novel evidence for the critical role of maternal milk protein glycosylation in shaping early-life gut microbiota and promoting B cell activation of neonates. The special core-fucosylated oligosaccharides might be promising prebiotics for the personalized nutrition of infants.

The maternal milk glycobiome is crucial for shaping the gut microbiota of infants. Although high core fucosylation catalyzed by fucosyltransferase 8 (Fut8) is a general feature of human milk glycoproteins, its role in the formation of a healthy microbiota has not been evaluated. In this study, we found that the core-fucosylated N-glycans in milk of Chinese mothers selectively promoted the colonization of specific gut microbial groups, such as Bifidobacterium spp. and Lactobacillus spp. in their breast-fed infants during lactation. Compared with Fut8^+/+ (WT) mouse-fed neonates, the offspring fed by Fut8^+/− maternal mice had a distinct gut microbial profile, which was featured by a significant reduction of Lactobacillus spp., Bacteroides spp., and Bifidobacterium spp. and increased abundance of members of the Lachnospiraceae NK4A136 group and Akkermansia spp. Moreover, these offspring mice showed a lower proportion of splenic CD19⁺ CD69⁺ B lymphocytes and attenuated humoral immune responses upon ovalbumin (OVA) immunization. In vitro studies demonstrated that the chemically synthesized core-fucosylated oligosaccharides possessed the ability to promote the growth of tested Bifidobacterium and Lactobacillus strains in minimal medium. The resulting L-fucose metabolites, lactate and 1,2-propanediol, could promote the activation of B cells via the B cell receptor (BCR)-mediated signaling pathway.

FUT8: from biochemistry to synthesis of core-fucosylated N-glycans

Glycosylation is a major posttranslational modification of proteins. Modification in structure on N-glycans leads to many diseases. One of such modifications is core α-1,6 fucosylation, which is only found in eukaryotes. For this reason, lots of research has been done on approaches to synthesize core-fucosylated N-glycans both chemically and enzymatically, in order to have well defined structures that can be used as probes for glycan analysis and identifying functions of glycan-binding proteins. This review will focus on FUT8, the enzyme responsible for core fucosylation in mammals and the strategies that have been developed for the synthesis of core fucosylated N-glycans have been synthesized so far.

A Systems Biology Approach Identifies FUT8 as a Driver of Melanoma Metastasis

Association of aberrant glycosylation with melanoma progression is based mainly on analyses of cell lines. Here we present a systems-based study of glycomic changes and corresponding enzymes associated with melanoma metastasis in patient samples. Upregulation of core fucosylation (FUT8) and downregulation of α-1,2 fucosylation (FUT1, FUT2) were identified as features of metastatic melanoma. Using both in vitro and in vivo studies, we demonstrate FUT8 is a driver of melanoma metastasis which, when silenced, suppresses invasion and tumor dissemination. Glycoprotein targets of FUT8 were enriched in cell migration proteins including the adhesion molecule L1CAM. Core fucosylation impacted L1CAM cleavage and the ability of L1CAM to support melanoma invasion. FUT8 and its targets represent therapeutic targets in melanoma metastasis.

Glycosyltransferases and non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease and its incidence is increasing worldwide. However, the underlying mechanisms leading to the development of NAFLD are still not fully understood. Glycosyltransferases (GTs) are a diverse class of enzymes involved in catalyzing the transfer of one or multiple sugar residues to a wide range of acceptor molecules. GTs mediate a wide range of functions from structure and storage to signaling, and play a key role in many fundamental biological processes. Therefore, it is anticipated that GTs have a role in the pathogenesis of NAFLD. In this article, we present an overview of the basic information on NAFLD, particularly GTs and glycosylation modification of certain molecules and their association with NAFLD pathogenesis. In addition, the effects and mechanisms of some GTs in the development of NAFLD are summarized.

α-1,6-Fucosyltransferase (FUT8) inhibits hemoglobin production during differentiation of murine and K562 human erythroleukemia cells

Erythropoiesis results from a complex combination of the expression of several transcription factor genes and cytokine signaling. However, the overall view of erythroid differentiation remains unclear. First, we screened for erythroid differentiation-related genes by comparing the expression profiles of high differentiation-inducible and low differentiation-inducible murine erythroleukemia cells. We identified that overexpression of α-1,6-fucosyltransferase (Fut8) inhibits hemoglobin production. FUT8 catalyzes the transfer of a fucose residue to N-linked oligosaccharides on glycoproteins via an α-1,6 linkage, leading to core fucosylation in mammals. Expression of Fut8 was down-regulated during chemically induced differentiation of murine erythroleukemia cells. Additionally, expression of Fut8 was positively regulated by c-Myc and c-Myb, which are known as suppressors of erythroid differentiation. Second, we found that FUT8 is the only fucosyltransferase family member that inhibits hemoglobin production. Functional analysis of FUT8 revealed that the donor substrate-binding domain and a flexible loop play essential roles in inhibition of hemoglobin production. This result clearly demonstrates that core fucosylation inhibits hemoglobin production. Third, FUT8 also inhibited hemoglobin production of human erythroleukemia K562 cells. Finally, a short hairpin RNA study showed that FUT8 down-regulation induced hemoglobin production and increase of transferrin receptor/glycophorin A-positive cells in human erythroleukemia K562 cells. Our findings define FUT8 as a novel factor for hemoglobin production and demonstrate that core fucosylation plays an important role in erythroid differentiation.

Donor substrate binding and enzymatic mechanism of human core α1,6-fucosyltransferase (FUT8)

BACKGROUND

Fucosylation is essential for various biological processes including tumorigenesis, inflammation, cell-cell recognition and host-pathogen interactions. Biosynthesis of fucosylated glycans is accomplished by fucosyltransferases. The enzymatic product of core α1,6-fucosyltransferase (FUT8) plays a major role in a plethora of pathological conditions, e.g. in prognosis of hepatocellular carcinoma and in colon cancer. Detailed knowledge of the binding mode of its substrates is required for the design of molecules that can modulate the activity of the enzyme.

METHODS

We provide a detailed description of binding interactions of human FUT8 with its natural donor substrate GDP-fucose and related compounds. GDP-Fuc was placed in FUT8 by structural analogy to the structure of protein-O-fucosyltransferase (cePOFUT) co-crystallized with GDP-Fuc. The epitope of the donor substrate bound to FUT8 was determined by STD NMR. The in silico model is further supported by experimental data from SPR binding assays. The complex was optimized by molecular dynamics simulations.

RESULTS

Guanine is specifically recognized by His363 and Asp453. Furthermore, the pyrophosphate is tightly bound via numerous hydrogen bonds and contributes affinity to a major part. Arg365 was found to bind both the β-phosphate and the fucose moiety at the same time.

CONCLUSIONS

Discovery of a novel structural analogy between cePOFUT and FUT8 allows the placement of the donor substrate GDP-Fuc. The positioning was confirmed by various experimental and computational techniques.

GENERAL SIGNIFICANCE

The model illustrates details of the molecular basis of substrate recognition for a human fucosyltransferase for the first time and, thus, provides a basis for structure-based design of inhibitors.

Molecular cloning, characterization, genomic organization and promoter analysis of the α1,6-fucosyltransferase gene (fut8) expressed in the rat hybridoma cell line YB2/0

Background

The rat hybridoma cell line YB2/0 appears a good candidate for the large-scale production of low fucose recombinant mAbs due to its lower expression of fut8 gene than other commonly used rodent cell lines. However, important variations of the fucose content of recombinant mAbs are observed in production culture conditions. To improve our knowledge on the YB2/0 fucosylation capacity, we have cloned and characterized the rat fut8 gene.

Results

The cDNAs encoding the rat α1,6-fucosyltransferase (FucT VIII) were cloned from YB2/0 cells by polymerase chain reaction-based and 5' RNA-Ligase-Mediated RACE methods. The cDNAs contain an open reading frame of 1728 bp encoding a 575 amino acid sequence showing 94% and 88% identity to human and pig orthologs, respectively. The recombinant protein expressed in COS-7 cells exhibits a α1,6-fucosyltransferase activity toward human asialo-agalacto-apotransferrin. The rat fut8 gene is located on chromosome 6 q and spans over 140 kbp. It contains 9 coding exons and four 5'-untranslated exons. FISH analysis shows a heterogeneous copy number of fut8 in YB2/0 nuclei with 2.8 ± 1.4 mean copy number. The YB2/0 fut8 gene is expressed as two main transcripts that differ in the first untranslated exon by the usage of distinct promoters and alternative splicing. Luciferase assays allow defining the minimal promoting regions governing the initiation of the two transcripts, which are differentially expressed in YB2/0 as shown by duplex Taqman QPCR analysis. Bioinformatics analysis of the minimal promoter regions upstream exons E-2 and E-3, governing the transcription of T1 and T2 transcripts, respectively, evidenced several consensus sequences for potential transcriptional repressors. Transient transfections of Rat2 cells with transcription factor expression vectors allowed identifying KLF15 as a putative repressor of T1 transcript in Rat2 cells.

Conclusion

Altogether, these data contribute to a better knowledge of fut8 expression in YB2/0 that will be useful to better control the fucosylation of recombinant mAbs produced in these cells.

Congenital dyserythropoietic anemia type II (CDAII/HEMPAS): where are we now?

Congenital diserythropoietic anemias (CDA) were classified according to bone marrow changes and biochemical features 40 years ago. A consistent finding in CDA type II, the most frequent subgroup of CDAs is a relevant hypoglycosylation of erythrocyte membrane proteins. It is a matter of debate if the hypoglycosylation is the primary cause of the disorder or a phenomenon secondary to other pathomechanisms. The molecular cause of the disorder is still unknown although some enzyme deficiencies have been proposed to cause CDA II in the last 2 decades and a linkage analysis locating the CDA II gene in a 5 cM region on chromosome 20 was done in 1997. In this review biochemical and genetic data are discussed and diagnostic methods based on biochemical observations of the recent years are reviewed.

Fucosylation in prokaryotes and eukaryotes

Fucosylated carbohydrate structures are involved in a variety of biological and pathological processes in eukaryotic organisms including tissue development, angiogenesis, fertilization, cell adhesion, inflammation, and tumor metastasis. In contrast, fucosylation appears less common in prokaryotic organisms and has been suggested to be involved in molecular mimicry, adhesion, colonization, and modulating the host immune response. Fucosyltransferases (FucTs), present in both eukaryotic and prokaryotic organisms, are the enzymes responsible for the catalysis of fucose transfer from donor guanosine-diphosphate fucose to various acceptor molecules including oligosaccharides, glycoproteins, and glycolipids. To date, several subfamilies of mammalian FucTs have been well characterized; these enzymes are therefore delineated and used as models. Non-mammalian FucTs that possess different domain construction or display distinctive acceptor substrate specificity are highlighted. It is noteworthy that the glycoconjugates from plants and schistosomes contain some unusual fucose linkages, suggesting the presence of novel FucT subfamilies as yet to be characterized. Despite the very low sequence homology, striking functional similarity is exhibited between mammalian and Helicobacter pylori alpha1,3/4 FucTs, implying that these enzymes likely share a conserved mechanistic and structural basis for fucose transfer; such conserved functional features might also exist when comparing other FucT subfamilies from different origins. Fucosyltranferases are promising tools used in synthesis of fucosylated oligosaccharides and glycoconjugates, which show great potential in the treatment of infectious and inflammatory diseases and tumor metastasis.

Reaction mechanism and substrate specificity for nucleotide sugar of mammalian alpha1,6-fucosyltransferase--a large-scale preparation and characterization of recombinant human FUT8

FUT8, mammalian alpha1,6-fucosyltransferase, catalyzes the transfer of a fucose residue from the donor substrate, guanosine 5'-diphosphate (GDP)-beta-L-fucose, to the reducing terminal GlcNAc of the core structure of asparagine-linked oligosaccharide via an alpha1,6-linkage. FUT8 is a typical type II membrane protein, which is localized in the Golgi apparatus. We have previously shown that two neighboring arginine residues that are conserved among alpha1,2-, alpha1,6-, and protein O-fucosyltransferases play an important role in donor substrate binding. However, details of the catalytic and reaction mechanisms and the ternary structure of FUT8 are not understood except for the substrate specificity of the acceptor. To develop a better understanding of FUT8, we established a large-scale production system for recombinant human FUT8, in which the enzyme is produced in soluble form by baculovirus-infected insect cells. Kinetic analyses and inhibition studies using derivatives of GDP-beta-L-fucose revealed that FUT8 catalyzes the reaction which depends on a rapid equilibrium random mechanism and strongly recognizes the base portion and diphosphoryl group of GDP-beta-L-fucose. These results may also be applicable to other fucosyltransferases and glycosyltransferases.

Expression of alpha1,6-fucosyltransferase (FUT8) in papillary carcinoma of the thyroid: its linkage to biological aggressiveness and anaplastic transformation

Previous studies have demonstrated that terminal fucosylation is associated with the biological aggressiveness of carcinomas, but the significance of core fucosylation (alpha1,6-fucosylation) through alpha1,6-fucosyltransferase (FUT8) has not been studied in depth. Herein, we investigated the expression of alpha1,6-fucosyltransferase (FUT8) in 133 cases of thyroid carcinomas using an immunohistochemical approach. The expression of FUT8 was quite low in normal follicules. A high expression of FUT8 was observed in 33.3% of papillary carcinoma and the incidence was directly linked to tumor size and lymph node metastasis. In contrast, this phenomenon was less frequently observed in follicular carcinoma and anaplastic (undifferentiated) carcinoma. These results suggest that FUT8 expression may be a key factor in the progression of thyroid papillary carcinomas, but not follicular carcinomas, and decreases in FUT8 expression might be linked to anaplastic transformation.

Comparison of glycosyltransferase families using the profile hidden Markov model

In order to investigate the relationship between glycosyltransferase families and the motif for them, we classified 47 glycosyltransferase families in the CAZy database into four superfamilies, GTS-A, -B, -C, and -D, using a profile Hidden Markov Model method. On the basis of the classification and the similarity between GTS-A and nucleotidylyltransferase family catalyzing the synthesis of nucleotide-sugar, we proposed that ancient oligosaccharide might have been synthesized by the origin of GTS-B whereas the origin of GTS-A might be the gene encoding for synthesis of nucleotide-sugar as the donor and have evolved to glycosyltransferases to catalyze the synthesis of divergent carbohydrates. We also suggested that the divergent evolution of each superfamily in the corresponding subcellular component has increased the complexities of eukaryotic carbohydrate structure.

Chemical modifications of alpha1,6-fucosyltransferase define amino acid residues of catalytic importance

alpha1,6-Fucosyltransferase (alpha6FucT) of human platelets was subjected to the action of phenylglyoxal (PLG), pyridoxal-5'-phosphate/NaBH(4) (PLP), and diethyl pyrocarbonate (DEPC) the reagents that selectively modify the structure of amino acids arginine, lysine and histidine, respectively, as well as to N-ethylmaleimide (NEM), mersalyl, p-chloromercuribenzoate (pCMB), iodoacetate, iodoacetamide, and methyl iodide that react with sulfhydryl group of cysteine. In addition, we treated the enzyme with beta-mercaptoethanol, a reagent that disrupts disulfide bonds. All reagents except NEM significantly inactivated alpha6FucT. Protection against the action of PLG, PLP and sulfhydryl modifying reagents was offered by GDP-fucose, GDP, and the acceptor substrate, a transferrin-derived biantennary glycopeptide with terminal GlcNAc residues. Neither donor nor acceptor substrate offered, however, any protection against inactivation by DEPC or beta-mercaptoethanol. We conclude that arginine, cysteine and probably lysine residues are present in, or closely by, the donor and acceptor substrate binding domains of the enzyme, whereas histidine may be a part of its catalytic domain. However, the primary structure of alpha6FucT does not show cysteine residues in proximity to the postulated GDP-fucose-binding site and acceptor substrate binding site of the enzyme that contains two neighboring arginine residues and one lysine residue (Glycobiol. 10 (2000) 503). To rationalize our results we postulate that platelet alpha6FucT is folded through disulfide bonds that bring together donor/acceptor-binding- and cysteine- and lysine-rich, presumably acceptor substrate binding sites, thus creating a catalytic center of the enzyme.

alpha1,6fucosyltransferase is highly and specifically expressed in human ovarian serous adenocarcinomas

An elevated level of alpha1,6fucosylation in N-glycans represents one of the cancer-related alterations of oligosaccharides and is associated with the metastatic potential of hepatoma cells. However, expression of alpha1,6fucosyltransferase (alpha1,6FucT), which is involved in this aberrant glycosylation, has not been intensively explored in other malignant tumors. We report on a study of the expression of alpha1,6FucT in various types of epithelial ovarian carcinoma tissue, as well as normal ovary, benign and borderline ovarian tumors. The activity assay showed that alpha1,6FucT is highly and specifically elevated in serous adenocarcinomas but not in normal and other ovarian tumor tissues. This elevation was due to enhancement of mRNA expression, as evidenced by Northern blot analysis. Furthermore, we have shown immunohistochemically that alpha1,6FucT expression is localized predominantly in cancer cells. Lectin blot analysis using Lens culinaris agglutinin, which preferentially recognizes alpha1,6fucose residue, suggested that several glycoproteins were likely targets for modification by alpha1, 6fucosylation in serous adenocarcinoma tissues. These findings suggest that the elevated expression of alpha1,6FucT and the resulting modification of N-glycans are distinctive features of this type of ovarian cancer and may be related to the progression of this malignancy.