Identification and characterization of endo-β-N-acetylglucosaminidase from methylotrophic yeast Ogataea minuta

In four yeast strains, Ogataea minuta, Candida parapolymorpha, Pichia anomala and Zygosaccharomyces rouxii, we identified endo-β-N-acetylglucosaminidase (ENGase) homologous sequences by database searches; in each of the four species, a corresponding enzyme activity was also confirmed in crude cell extract obtained from each strain. The O. minuta ENGase (Endo-Om)-encoding gene was directly amplified from O. minuta genomic DNA and sequenced. The Endo-Om-encoding gene contained a 2319-bp open-reading frame; the deduced amino acid sequence indicated that the putative protein belonged to glycoside hydrolase family 85. The gene was introduced into O. minuta, and the recombinant Endo-Om was overexpressed and purified. When the enzyme assay was performed using an agalacto-biantennary oligosaccharide as a substrate, Endo-Om exhibited both hydrolysis and transglycosylation activities. Endo-Om exhibited hydrolytic activity for high-mannose, hybrid, biantennary and (2,6)-branched triantennary N-linked oligosaccharides, but not for tetraantennary, (2,4)-branched triantennary, bisecting N-acetylglucosamine structure and core-fucosylated biantennary N-linked oligosaccharides. Endo-Om also was able to hydrolyze N-glycans attached to RNase B and human transferrin under both denaturing and nondenaturing conditions. Thus, the present study reports the detection and characterization of a novel yeast ENGase.

A serum "sweet-doughnut" protein facilitates fibrosis evaluation and therapy assessment in patients with viral hepatitis

Although liver fibrosis reflects disease severity in chronic hepatitis patients, there has been no simple and accurate system to evaluate the therapeutic effect based on fibrosis. We developed a glycan-based immunoassay, FastLec-Hepa, to fill this unmet need. FastLec-Hepa automatically detects unique fibrosis-related glyco-alteration in serum hyperglycosylated Mac-2 binding protein within 20 min. The serum FastLec-Hepa counts increased with advancing fibrosis and illustrated significant differences in medians between all fibrosis stages. FastLec-Hepa is sufficiently sensitive and quantitative to evaluate the effects of PEG-interferon-α/ribavirin therapy in a short post-therapeutic interval. The obtained fibrosis progression is equivalent to -0.30 stages/year in patients with sustained virological response, and 0.01 stages/year in relapse/nonresponders. Furthermore, long-term follow-up of the severely affected patients found hepatocellular carcinoma developed in patients after therapy whose FastLec-Hepa counts remained above a designated cutoff value. FastLec-Hepa is the only assay currently available for clinically beneficial therapy evaluation through quantitation of disease severity.

Construction of a chondroitin sulfate library with defined structures and analysis of molecular interactions

Chondroitin sulfate (CS) is a linear acidic polysaccharide, composed of repeating disaccharide units of glucuronic acid and N-acetyl-D-galactosamine and modified with sulfate residues at different positions, which plays various roles in development and disease. Here, we chemo-enzymatically synthesized various CS species with defined lengths and defined sulfate compositions, from chondroitin hexasaccharide conjugated with hexamethylenediamine at the reducing ends, using bacterial chondroitin polymerase and recombinant CS sulfotransferases, including chondroitin-4-sulfotransferase 1 (C4ST-1), chondroitin-6-sulfotransferase 1 (C6ST-1), N-acetylgalactosamine 4-sulfate 6-sulfotransferase (GalNAc4S-6ST), and uronosyl 2-sulfotransferase (UA2ST). Sequential modifications of CS with a series of CS sulfotransferases revealed their distinct features, including their substrate specificities. Reactions with chondroitin polymerase generated non-sulfated chondroitin, and those with C4ST-1 and C6ST-1 generated uniformly sulfated CS containing >95% 4S and 6S units, respectively. GalNAc4S-6ST and UA2ST generated highly sulfated CS possessing ∼90% corresponding disulfated disaccharide units. Sequential reactions with UA2ST and GalNAc4S-6ST generated further highly sulfated CS containing a mixed structure of disulfated units. Surprisingly, sequential reactions with GalNAc4S-6ST and UA2ST generated a novel CS molecule containing ∼29% trisulfated disaccharide units. Enzyme-linked immunosorbent assay and surface plasmon resonance analysis using the CS library and natural CS products modified with biotin at the reducing ends, revealed details of the interactions of CS species with anti-CS antibodies, and with CS-binding molecules such as midkine and pleiotrophin. Chemo-enzymatic synthesis enables the generation of CS chains of the desired lengths, compositions, and distinct structures, and the resulting library will be a useful tool for studies of CS functions.

LecT-Hepa, a glyco-marker derived from multiple lectins, as a predictor of liver fibrosis in chronic hepatitis C patients

Assessment of liver fibrosis in patients with chronic hepatitis C (CHC) is critical for predicting disease progression and determining future antiviral therapy. LecT-Hepa, a new glyco-marker derived from fibrosis-related glyco-alteration of serum alpha 1-acid glycoprotein, was used to differentiate cirrhosis from chronic hepatitis in a single-center study. Herein, we aimed to validate this new glyco-marker for estimating liver fibrosis in a multicenter study. Overall, 183 CHC patients were recruited from 5 liver centers. The parameters Aspergillus oryzae lectin (AOL) / Dature stramonium lectin (DSA) and Maackia amurensis lectin (MAL)/DSA were measured using a bedside clinical chemistry analyzer in order to calculate LecT-Hepa levels. The data were compared with those of seven other noninvasive biochemical markers and tests (hyaluronic acid, tissue inhibitor of metalloproteases-1, platelet count, aspartate aminotransferase-to-platelet ratio index [APRI], Forns index, Fib-4 index, and Zeng's score) for assessing liver fibrosis using the receiver-operating characteristic curve. LecT-Hepa correlated well with the fibrosis stage as determined by liver biopsy. The area under the curve (AUC), sensitivity, and specificity of LecT-Hepa were 0.802, 59.6%, and 89.9%, respectively, for significant fibrosis; 0.882, 83.3%, and 80.0%, respectively, for severe fibrosis; and 0.929, 84.6%, and 88.5%, respectively, for cirrhosis. AUC scores of LecT-Hepa at each fibrosis stage were greater than those of the seven aforementioned noninvasive tests and markers.

CONCLUSION

The efficacy of LecT-Hepa, a glyco-marker developed using glycoproteomics, for estimating liver fibrosis was demonstrated in a multicenter study. LecT-Hepa given by a combination of the two glyco-parameters is a reliable method for determining the fibrosis stage and is a potential substitute for liver biopsy.

Large-scale identification of target proteins of a glycosyltransferase isozyme by Lectin-IGOT-LC/MS, an LC/MS-based glycoproteomic approach

Model organisms containing deletion or mutation in a glycosyltransferase-gene exhibit various physiological abnormalities, suggesting that specific glycan motifs on certain proteins play important roles in vivo. Identification of the target proteins of glycosyltransferase isozymes is the key to understand the roles of glycans. Here, we demonstrated the proteome-scale identification of the target proteins specific for a glycosyltransferase isozyme, β1,4-galactosyltransferase-I (β4GalT-I). Although β4GalT-I is the most characterized glycosyltransferase, its distinctive contribution to β1,4-galactosylation has been hardly described so far. We identified a large number of candidates for the target proteins specific to β4GalT-I by comparative analysis of β4GalT-I-deleted and wild-type mice using the LC/MS-based technique with the isotope-coded glycosylation site-specific tagging (IGOT) of lectin-captured N-glycopeptides. Our approach to identify the target proteins in a proteome-scale offers common features and trends in the target proteins, which facilitate understanding of the mechanism that controls assembly of a particular glycan motif on specific proteins.

Chondroitin sulfate synthase-2 is necessary for chain extension of chondroitin sulfate but not critical for skeletal development

Chondroitin sulfate (CS) is a linear polysaccharide consisting of repeating disaccharide units of N-acetyl-D-galactosamine and D-glucuronic acid residues, modified with sulfated residues at various positions. Based on its structural diversity in chain length and sulfation patterns, CS provides specific biological functions in cell adhesion, morphogenesis, neural network formation, and cell division. To date, six glycosyltransferases are known to be involved in the biosynthesis of chondroitin saccharide chains, and a hetero-oligomer complex of chondroitin sulfate synthase-1 (CSS1)/chondroitin synthase-1 and chondroitin sulfate synthase-2 (CSS2)/chondroitin polymerizing factor is known to have the strongest polymerizing activity. Here, we generated and analyzed CSS2^−/− mice. Although they were viable and fertile, exhibiting no overt morphological abnormalities or osteoarthritis, their cartilage contained CS chains with a shorter length and at a similar number to wild type. Further analysis using CSS2^−/− chondrocyte culture systems, together with siRNA of CSS1, revealed the presence of two CS chain species in length, suggesting two steps of CS chain polymerization; i.e., elongation from the linkage region up to Mr ∼10,000, and further extension. There, CSS2 mainly participated in the extension, whereas CSS1 participated in both the extension and the initiation. Our study demonstrates the distinct function of CSS1 and CSS2, providing a clue in the elucidation of the mechanism of CS biosynthesis.

Comparison of LecT-Hepa and FibroScan for assessment of liver fibrosis in hepatitis B virus infected patients with different ALT levels

BACKGROUND

FibroScan is one of the noninvasive techniques based on the transient elastography that can assess the progression of liver fibrosis in chronic hepatitis patients in daily clinical practice. Recently, LecT-Hepa was validated as a serological glycomarker correlating well with the fibrosis stage determined by liver biopsy, and was superior to many other noninvasive biochemical markers and tests. We compared the reliability of LecT-Hepa with that of FibroScan for evaluation of liver fibrosis.

METHODS

The effects of increased alanine aminotransferase (ALT) activities on LecT-Hepa and FibroScan were investigated.

RESULTS

The areas under the receiver-operating characteristic curves, sensitivity and specificity for detecting cirrhosis, which is one of the outcomes of fibrosis estimation, were 0.82, 72.5% and 78.2% of LecT-Hepa, 0.85, 87.0% and 74.1% of FibroScan; these did not differ significantly. The count distribution of LecT-Hepa in non-cirrhosis group or cirrhosis group did not differ between the patients grouped according to their ALT levels, whereas that of FibroScan was substantially affected.

CONCLUSION

LecT-Hepa was confirmed as a reliable noninvasive test for the evaluation of liver fibrosis in hepatitis B virus-infected patients with comparable performance to that of FibroScan and proved to be unaffected by inflammation.

Abstract 4155: Comprehensive glucan profile exploration of mutated K-ras knockdown in colorectal cancer

(Background) In colorectal cancer (CRC), K-ras mutation is found in nearly 40% of the patients, and it is of prognostic significance (Onozato W et al, J Surg Oncol, 2010). Moreover, its knockdown in CRC cell lines with mutated K-ras gene results in robust reduction of ability of cell proliferation and anchorage independent growth (Shirasawa S, Science, 1993), both of which reflect metastatic ability. On the other hand, robust alterations of glycan structures have been reported in CRC promotion steps, accompanied by remarkable phenotypic changes, however there is no report that mentions the relationship of K-ras mutation and glycan change. (Materials and Methods) We examined glycan change of CRC cell lines (DLD1 and HCT116) somatically knocked out for K-ras gene by lectin array including 41 lectins to elucidate whether K-ras mutation-induced glycan changes play a critical role in CRC promotion. (Result) (1) In DLD1, we compared DLD1 wild type genotype cells (DLD1, DKS-5) with those that were knocked out for mutated K-ras gene (DKO-3, DKS-8), and the signals of MAL, MPA, UEA-I, and TJA-II were remarkably decreased in the knockdown cells. (2) In HCT116, we compared HCT116 wild type genotypic cells (HCT116, Hk2-10) with those that were knocked out for the mutated K-ras gene (Hke-3), and both MAL and MPA were remarkably declined. (3) In both cell lines, expression changes of glycans which can bind with MAL and MPA were consistent with the results of the lectin blotting, and both lectin signals were confirmed to be commonly altered by removing the mutated K-ras gene. (Conclusion) Mutated K-ras may be involved in critical phenotype change of CRC, accompanied by abnormal sialic acid recognition.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4155. doi:1538-7445.AM2012-4155

Enhancement of metastatic ability by ectopic expression of ST6GalNAcI on a gastric cancer cell line in a mouse model

ST6GalNAcI is a sialyltransferase responsible for the synthesis of sialyl Tn (sTn) antigen which is expressed in a variety of adenocarcinomas including gastric cancer especially in advanced cases, but the roles of ST6GalNAcI and sTn in cancer progression are largely unknown. We generated sTn-expressing human gastric cancer cells by ectopic expression of ST6GalNAcI to evaluate metastatic ability of these cells and prognostic effect of ST6GalNAcI and sTn in a mouse model, and identified sTn carrier proteins to gain insight into the function of ST6GalNAcI and sTn in gastric cancer progression. A green fluorescent protein-tagged human gastric cancer cell line was transfected with ST6GalNAcI to produce sTn-expressing cells, which were transplanted into nude mice. STn-positive gastric cancer cells showed higher intraperitoneal metastatic ability in comparison with sTn-negative control, resulting in shortened survival time of the mice, which was mitigated by anti-sTn antibody administration. Then, sTn-carrying proteins were immunoprecipitated from culture supernatants and lysates of these cells, and identified MUC1 and CD44 as major sTn carriers. It was confirmed that MUC1 carries sTn also in human advanced gastric cancer tissues. Identification of sTn carrier proteins will help understand mechanisms of metastatic phenotype acquisition of gastric cancer cells by ST6GalNAcI and sTn.

A chemoenzymatic approach toward the identification of fucosylated glycoproteins and mapping of N-glycan sites

Fucose (Fuc)-containing glycoconjugates play important roles in numerous physiological and pathological processes. Given the biological importance of post-translational glycosylation, a specific and robust strategy for the identification of fucosylated glycoproteins is highly desirable. In this study, we demonstrate an alternative way of labeling of fucosylated structures by metabolic engineering, using a chemoenzymatic approach. In this approach, the activities of Bacteroides fragilis 9343 L-fucokinase/guanosine-5'-diphosphate-Fuc pyrophosphorylase and human α1,3-fucosyltransferase 9 are combined in a Namalwa cellular model. Interestingly, this system could be applied to labeling of alkyne-modified fucosylated glycoproteins. N-Glycan site mapping and identification were done using an in vitro selective chemical ligation reaction and isotope-coded glycosylation site-specific tagging, subsequent to liquid chromatography-tandem mass spectrometry analysis. This work illustrates the use of a click chemistry-based strategy combined with a glycoproteomic technique to get further insight into the pattern of Fuc-mediated biological processes and functions.

Characterization of ppGalNAc-T18, a member of the vertebrate-specific Y subfamily of UDP-N-acetyl-α-D-galactosamine:polypeptide N-acetylgalactosaminyltransferases

The first step of mucin-type O-glycosylation is catalyzed by members of the UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase (ppGalNAc-T; EC 2.4.1.41) family. Each member of this family has unique substrate specificity and expression profiles. In this report, we describe a new subfamily of ppGalNAc-Ts, designated the Y subfamily. The Y subfamily consists of four members, ppGalNAc-T8, -T9, -T17 and -T18, in which the conserved YDX(5)WGGENXE sequence in the Gal/GalNAc-T motif of ppGalNAc-Ts is mutated to LDX(5)YGGENXE. Phylogenetic analysis revealed that the Y subfamily members only exist in vertebrates. All four Y subfamily members lack in vitro GalNAc-transferase activity toward classical substrates possibly because of the UDP-GalNAc-binding pocket mutants. However, ppGalNAc-T18, the newly identified defining member, was localized in the endoplasmic reticulum rather than the Golgi apparatus in lung carcinoma cells. The knockdown of ppGalNAc-T18 altered cell morphology, proliferation potential and changed cell O-glycosylation. ppGalNAc-T18 can also modulate the in vitro GalNAc-transferase activity of ppGalNAc-T2 and -T10, suggesting that it may be a chaperone-like protein. These findings suggest that the new Y subfamily of ppGalNAc-Ts plays an important role in protein glycosylation; characterizing their functions will provide new insight into the role of ppGalNAc-Ts.

Membrane sialidase NEU3 is highly expressed in human melanoma cells promoting cell growth with minimal changes in the composition of gangliosides

NEU3 is a membrane sialidase specific for gangliosides. Its increased expression and implication in some cancers have been reported. Here, we analyzed NEU3 expression in malignant melanoma cell lines and its roles in the cancer phenotypes. Quantitative RT-PCR revealed that high levels of the NEU3 gene were expressed at almost equivalent levels with those in colon cancers. To examine the effects of overexpression of NEU3, NEU3 cDNA-transfectant cells were established using a melanoma cell line SK-MEL-28 and its mutant N1 lacking GD3. SK-MEL-28 sublines overexpressing both the NEU3 gene and NEU3 enzyme activity showed no changes in both cell growth and ganglioside expression, while N1 cells showed a mild increase in cell proliferation with increased phosphorylation of the EGF receptor and neo-synthesis of Gb3 after NEU3 transfection. In contrast, NEU3 silencing resulted in a definite reduction in cell growth in a melanoma line MeWo, while ganglioside patterns underwent minimal changes. Phosphorylation levels of ERK1/2 with serum stimulation decreased in the NEU3-silenced cells. All these results suggest that NEU3 is highly expressed to enhance malignant phenotypes including apoptosis inhibition in malignant melanomas.

High Throughput ELISAs to Measure a Unique Glycan on Transferrin in Cerebrospinal Fluid: A Possible Extension toward Alzheimer's Disease Biomarker Development

We have established high-throughput lectin-antibody ELISAs to measure different glycans on transferrin (Tf) in cerebrospinal fluid (CSF) using lectins and an anti-transferrin antibody (TfAb). Lectin blot and precipitation analysis of CSF revealed that PVL (Psathyrella velutina lectin) bound an unique N-acetylglucosamine-terminated N-glycans on “CSF-type” Tf whereas SSA (Sambucus sieboldiana agglutinin) bound α2,6-N-acetylneuraminic acid-terminated N-glycans on “serum-type” Tf. PVL-TfAb ELISA of 0.5 μL CSF samples detected “CSF-type” Tf but not “serum-type” Tf whereas SSA-TfAb ELISA detected “serum-type” Tf but not “CSF-type” Tf, demonstrating the specificity of the lectin-TfAb ELISAs. In idiopathic normal pressure hydrocephalus (iNPH), a senile dementia associated with ventriculomegaly, amounts of the SSA-reactive Tf were significantly higher than in non-iNPH patients, indicating that Tf glycan analysis by the high-throughput lectin-TfAb ELISAs could become practical diagnostic tools for iNPH. The lectin-antibody ELISAs of CSF proteins might be useful for diagnosis of the other neurological diseases.

LecT-Hepa: A triplex lectin-antibody sandwich immunoassay for estimating the progression dynamics of liver fibrosis assisted by a bedside clinical chemistry analyzer and an automated pretreatment machine

BACKGROUND

A quantitative analysis of glyco-alteration in serum glycoproteins provides glyco-parameters for estimating the progression of liver fibrosis. In the analysis of glycans, a manual pretreatment process for clinical specimens leads to a complicated manipulation and loss-of-clinical implementation of the assay.

METHOD

We evaluated an automated triplex lectin-antibody sandwich immunoassay assisted by an automated protein purification system (ED-01) and a bedside clinical chemistry analyzer (HISCL) for the acquisition of two glyco-parameters (AOL/DSA and MAL/DSA) derived from a fibrosis-related glyco-alteration of serum alpha1-acid glycoprotein (AGP).

RESULTS

We adjusted the auto-machines with their accuracy set to CV <5.0% (ED-01) and <1.0% (HISCL). AGP samples were enriched from 275 serum specimens. Two glyco-parameters obtained by HISCL showed a linear correlation with that from a reported assay (R>0.90). The formula for monitoring fibrosis (LecT-Hepa) was given by a combination of the glyco-parameters. This correlated with the fibrosis stage from biopsy (R=0.68) and diagnosed severe fibrosis and cirrhosis. It was superior to that of FIB-4 index.

CONCLUSIONS

We automated a multilectin-assisted immunoassay with an order of magnitude reduction of operation time without any loss-of-accuracy. LecT-Hepa is a reliable method to assess fibrosis-dynamics from moderate fibrosis to cirrhosis.

Functional expression of L-fucokinase/guanosine 5'-diphosphate-L-fucose pyrophosphorylase from Bacteroides fragilis in Saccharomyces cerevisiae for the production of nucleotide sugars from exogenous monosaccharides

The biosynthesis of glycoconjugates requires the relevant glycosyltransferases and nucleotide sugars that can act as donors. Given the biological importance of posttranslational glycosylation, a facile, robust and cost-effective strategy for the synthesis of nucleotide sugars is highly desirable. In this study, we demonstrate the synthesis of nucleotide sugars from corresponding monosaccharides in a highly efficient manner via metabolic engineering, using an enzymatic approach. This method exploits l-fucokinase/guanosine 5'-diphosphate (GDP)-l-fucose (L-Fuc) pyrophosphorylase (FKP), a bifunctional enzyme isolated from Bacteroides fragilis 9343, which converts l-Fuc into GDP-L-Fuc via an L-Fuc-1-phosphate intermediate. Because L-Fuc and d-arabinose (D-Ara) are structurally similar, it is assumed that the biosynthesis of GDP-D-Ara in a recombinant Saccharomyces cerevisiae strain harboring the FKP gene can occur through a mechanism akin to that of GDP-L-Fuc via the salvage pathway. Thus, we reasoned that by exogenously supplying different monosaccharides structurally related to L-Fuc, it should be possible to produce the corresponding nucleotide sugars with this recombinant yeast strain, regardless of internal acquisition of nucleotide sugars through expression of additive enzymes in the de novo pathway.

Combination use of anti-CD133 antibody and SSA lectin can effectively enrich cells with high tumorigenicity

Glycans exhibit characteristic changes in their structures during development and thus have been used as markers for stem/progenitor cells. However, the glycan structures unique to cancer stem cells (CSC) remain unknown. In the present study, we examined glycan structures in CD133+ CD13+ CSC, which were recently found to have a high CSC ability, by means of a lectin microarray. Seven sialylated glycan-recognizing lectins, MAL-I, SNA, SSA, TJA-I, ACG, ABA and MAH, showed higher affinity to CD133+ CD13+ CSC than CD133+ cells with a lower CSC ability. In addition, we demonstrated that CD133+ SSA+ cells isolated from Huh7 cells had a significantly higher ability to form tumors in non-obese diabetic/severe combined immunodeficiency disease (NOD/SCID) mice and spheres under serum-free conditions than CD133+ SSA- cells. These results suggest that hepatic CSC highly express sialylated glycans and that SSA lectin can be used as a tool for isolating CSC. This study is the first report to demonstrate the characteristic glycan structures in CSC and to indicate a new methodology involving lectins for isolating CSC.

Alpha1,6-fucosyltransferase-deficient mice exhibit multiple behavioral abnormalities associated with a schizophrenia-like phenotype: importance of the balance between the dopamine and serotonin systems

Previously, we reported that α1,6-fucosyltransferase (Fut8)-deficient (Fut8(-/-)) mice exhibit emphysema-like changes in the lung and severe growth retardation due to dysregulation of TGF-β1 and EGF receptors and to abnormal integrin activation, respectively. To study the role of α1,6-fucosylation in brain tissue where Fut8 is highly expressed, we examined Fut8(-/-) mice using a combination of neurological and behavioral tests. Fut8(-/-) mice exhibited multiple behavioral abnormalities consistent with a schizophrenia-like phenotype. Fut8(-/-) mice displayed increased locomotion compared with wild-type (Fut8(+/+)) and heterozygous (Fut8(+/-)) mice. In particular, Fut8(-/-) mice showed strenuous hopping behavior in a novel environment. Working memory performance was impaired in Fut8(-/-) mice as evidenced by the Y-maze tests. Furthermore, Fut8(-/-) mice showed prepulse inhibition (PPI) deficiency. Intriguingly, although there was no significant difference between Fut8(+/+) and Fut8(+/-) mice in the PPI test under normal conditions, Fut8(+/-) mice showed impaired PPI after exposure to a restraint stress. This result suggests that reduced expression of Fut8 is a plausible cause of schizophrenia and related disorders. The levels of serotonin metabolites were significantly decreased in both the striatum and nucleus accumbens of the Fut8(-/-) mice. Likewise, treatment with haloperidol, which is an antipsychotic drug that antagonizes dopaminergic and serotonergic receptors, significantly reduced hopping behaviors. The present study is the first to clearly demonstrate that α1,6-fucosylation plays an important role in the brain, and that it might be related to schizophrenia-like behaviors. Thus, the results of the present study provide new insights into the underlying mechanisms responsible for schizophrenia and related disorders.

Formation of microvilli and phosphorylation of ERM family proteins by CD43, a potent inhibitor for cell adhesion: cell detachment is a potential cue for ERM phosphorylation and organization of cell morphology

CD43/sialophorin/leukosialin, a common leukocyte antigen, is known as an inhibitor for cell adhesion. The ectodomain of CD43 is considered as a molecular barrier for cell adhesion, while the cytoplasmic domain has a binding site for Ezrin/Radixin/Moesin (ERM). We found expression of CD43 induced cell rounding, inhibition of cell re-attachment, augmentation of microvilli, and phosphorylation of ERM in HEK293T cells. Mutant studies revealed the ectodomain of CD43, but not the intracellular domain, essential and sufficient for all these phenomena. We also found that forced cell detachment by itself induced phosphorylation of ERM in HEK293T cells. Taken together, these findings indicate that inhibition of cell adhesion by the ectodomain of CD43 induces phosphorylation of ERM, microvilli formation, and eventual cell rounding. Furthermore, our study suggests a novel possibility that cell detachment itself induces activation of ERM and modification of cell shape.

Expression and the role of 3'-phosphoadenosine 5'-phosphosulfate transporters in human colorectal carcinoma

Sulfation represents an essential modification for various molecules and regulates many biological processes. The sulfation of glycans requires a specific transporter for 3'-phosphoadenosine 5'-phosphosulfate (PAPS) on the Golgi apparatus. This study investigated the expression of PAPS transporter genes in colorectal carcinomas and the significance of Golgi-specific sulfation in the proliferation of colorectal carcinoma cells. The relative amount of PAPST1 transcripts was found to be higher than those of PAPST2 in colorectal cancerous tissues. Immunohistochemically, the enhanced expression of PAPST1 was observed in fibroblasts in the vicinity of invasive cancer cells, whereas the expression of PAPST2 was decreased in the epithelial cells. RNA interference of either of the two PAPS transporter genes reduced the extent of sulfation of cellular proteins and cellular proliferation of DLD-1 human colorectal carcinoma cells. Silencing the PAPS transporter genes reduced fibroblast growth factor signaling in DLD-1 cells. These findings indicate that PAPS transporters play a role in the proliferation of colorectal carcinoma cells themselves and take part in a desmoplastic reaction to support cancer growth by controlling their sulfation status.

Lectin microarray analysis of pluripotent and multipotent stem cells

Stem cells have a capability to self-renew and differentiate into multiple types of cells; specific markers are available to identify particular stem cells for developmental biology research. In this study, we aimed to define the status of somatic stem cells and the pluripotency of human embryonic stem (hES) and induced pluripotent stem (iPS) cells using a novel molecular methodology, lectin microarray analysis. Our lectin microarray analysis successfully categorized murine somatic stem cells into the appropriate groups of differentiation potency. We then classified hES and iPS cells by the same approach. Undifferentiated hES cells were clearly distinguished from differentiated hES cells after embryoid formation. The pair-wise comparison means based on 'false discovery rate' revealed that three lectins -Euonymus europaeus lectin (EEL), Maackia amurensis lectin (MAL) and Phaseolus vulgaris leucoagglutinin [PHA(L)]- generated maximal values to define undifferentiated and differentiated hES cells. Furthermore, to define a pluripotent stem cell state, we generated a discriminant for the undifferentiated state with pluripotency. The discriminant function based on lectin reactivities was highly accurate for judgment of stem cell pluripotency. These results suggest that glycomic analysis of stem cells leads to a novel comprehensive approach for quality control in cell-based therapy and regenerative medicine.

Chondroitin sulfate N-acetylgalactosaminyltransferase 1 is necessary for normal endochondral ossification and aggrecan metabolism

Chondroitin sulfate (CS) is a glycosaminoglycan, consisting of repeating disaccharide units of N-acetylgalactosamine and glucuronic acid residues, and plays important roles in development and homeostasis of organs and tissues. Here, we generated and analyzed mice lacking chondroitin sulfate N-acetylgalactosaminyltransferase 1 (CSGalNAcT-1). Csgalnact1(-/-) mice were viable and fertile but exhibited slight dwarfism. Biochemically, the level of CS in Csgalnact1(-/-) cartilage was reduced to ∼50% that of wild-type cartilage, whereas its chain length was similar to wild-type mice, indicating that CSGalNAcT-1 participates in the CS chain initiation as suggested in the previous study (Sakai, K., Kimata, K., Sato, T., Gotoh, M., Narimatsu, H., Shinomiya, K., and Watanabe, H. (2007) J. Biol. Chem. 282, 4152-4161). Histologically, the growth plate of Csgalnact1(-/-) mice contained shorter and slightly disorganized chondrocyte columns with a reduced volume of the extracellular matrix principally in the proliferative layer. Immunohistochemical analysis revealed that the level of both aggrecan and link protein 1 were decreased in Csgalnact1(-/-) cartilage. Western blot analysis demonstrated an increase in processed forms of aggrecan core protein. These results suggest that CSGalNAcT-1 is required for normal levels of CS biosynthesis in cartilage. Our observations suggest that CSGalNAcT-1 is necessary for normal levels of endochondral ossification, and the decrease in CS amount in the growth plate by its absence causes a rapid catabolism of aggrecan.

Identification of a novel human UDP-GalNAc transferase with unique catalytic activity and expression profile

A novel member of the human ppGalNAc-T family, ppGalNAc-T20, was identified and characterized. Amino acid alignment revealed a high sequence identity between ppGalNAc-T20 and -T10. In the GalNAc transfer assay towards mucin-derived peptide substrates, the recombinant ppGalNAc-T20 demonstrated to be a typical glycopeptide GalNAc-transferase that exhibits activity towards mono-GalNAc-glycosylated peptide EA2 derived from rat submandibular gland mucin but no activity towards non-modified EA2. The in vitro catalytic property of ppGalNAc-T20 was compared with that of ppGalNAc-T10 to show different acceptor substrate specificities and kinetic constants. The ppGalNAc-T20 transcript was found exclusively in testis and brain. In situ hybridization further reveals that ppGalNAc-T20 was specifically localized in primary and secondary spermatocytes of the two meiotic periods, suggesting that it may involve in O-glycosylation during mouse spermatogenesis.

Multilectin assay for detecting fibrosis-specific glyco-alteration by means of lectin microarray

BACKGROUND

Despite the progress made in understanding glyco-alterations of specific glycoproteins such as α1-acid glycoprotein (AGP) associated with liver fibrosis, there has been no useful diagnostic assay with a lectin recognizing the fibrosis-specific alteration and an antibody against the core protein. We therefore developed a compatible multiple lectin-antibody sandwich immunoassay on the basis of the results obtained by the lectin microarray analysis for monitoring fibrosis.

METHODS

AGP-enriched fractions derived from 0.5-μL sera of 125 patients with staging-determined fibrosis (26.4% F0-F1, 25.6% F2, 24% F3, and 23.2% F4) were subjected to systematic analysis by antibody-overlay lectin microarray. Data were analyzed to statistically relate to the degree of fibrosis progression. Additionally, we applied an optimal lectin signal set on the microarray to distinguish 45 patients with cirrhosis from 43 patients with chronic hepatitis.

RESULTS

Signal patterns of the 12 selected lectins reflected fibrosis-associated glyco-alteration of AGP. Among the 12 lectins, we found a specific lectin at each stage of fibrosis (i.e., significant fibrosis, severe fibrosis, and cirrhosis) (P < 0.0001). The test for the detection of cirrhosis showed that combinational use of 3 lectins (AOL, MAL, and DSA) on the array enhanced the diagnostic value for liver cirrhosis to 95% diagnostic sensitivity and 91% diagnostic specificity.

CONCLUSIONS

The multiple lectin-antibody sandwich immunoassay targeting AGP enables monitoring of disease progression in chronic hepatitis patients at risk of developing hepatocellular carcinoma.

Glycomic analyses of glycoproteins in bile and serum during rat hepatocarcinogenesis

Fucosylated alpha-fetoprotein (AFP) is a specific tumor marker for hepatocellular carcinomas (HCC). However, the mechanisms underlying the increase in fucosylated AFP in serum of patients with HCC are largely unknown. Recently, we reported that fucosylation is a possible signal for the secretion of glycoproteins into bile in the liver. This finding might lead to the selective secretion of fucosylated AFP into bile and the selective secretion might be disrupted in hepatocarcinogenesis. In this study, therefore, we analyzed the oligosaccharide structures of glycoproteins in bile and serum of LEC rats, which are a rat model of spontaneous hepatocarcinogenesis. Lectin microarraying showed enhanced binding of 13 lectins to bile, compared with in serum from normal LEC rats, and the binding of these lectins to serum of LEC rats bearing HCC was higher than in normal rats. Structural analyses involving HPLC and mass spectrometry showed that the fucosylation levels of serum glycoproteins were not increased in CH rats but were in HCC rats, although the fucosylation levels of biliary glycoproteins were increased in both CH and HCC rats. These results suggested that the sorting machinery through fucosylation might be disrupted in the liver with HCC.

Differential expression of glycogenes in tonsillar B lymphocytes in association with proteinuria and renal dysfunction in IgA nephropathy

Aberrant O-glycosylation of serum and tonsillar IgA1 is one of the main pathogeneses of IgA nephropathy (IgAN). However, the synthesis of underglycosylated IgA1 in tonsils has not yet been characterized. This study examined tonsillar B lymphocytes of IgAN (n=34) using tonsils derived from patients with chronic tonsillitis (n=24) and sleep apnea syndrome (n=14) as a control. Gene expression of beta1,3-galactosyltransferase (beta3GalT), and the core 1 beta3GalT-specific molecular chaperone, Cosmc, UDP-N-acetyl-alpha-D-galactosamine: polypeptide N-acetylgalactosaminyl-transferase 2, were significantly decreased in tonsillar CD19-positive B lymphocytes from IgAN patients compared to control tonsillar tissues as determined by real-time RT-PCR. Tonsillar B cell beta3GalT gene expression significantly correlated with estimated GFR and negatively correlated with proteinuria and histological injury score. Western blotting showed the protein expression of beta3GalT in the tonsils to significantly decrease in IgAN in comparison to the controls. These data suggest the downregulation of beta3GalT in tonsillar B lymphocytes to be closely associated with the clinical characteristics of IgAN.

Chondroitin sulfate synthase-2/chondroitin polymerizing factor has two variants with distinct function

Chondroitin sulfate (CS) is a polysaccharide consisting of repeating disaccharide units of N-acetyl-D-galactosamine and d-glucuronic acid residues, modified with sulfated residues at various positions. To date six glycosyltransferases for chondroitin synthesis have been identified, and the complex of chondroitin sulfate synthase-1 (CSS1)/chondroitin synthase-1 (ChSy-1) and chondroitin sulfate synthase-2 (CSS2)/chondroitin polymerizing factor is assumed to play a major role in CS biosynthesis. We found an alternative splice variant of mouse CSS2 in a data base that lacks the N-terminal transmembrane domain, contrasting to the original CSS2. Here, we investigated the roles of CSS2 variants. Both the original enzyme and the splice variant, designated CSS2A and CSS2B, respectively, were expressed at different levels and ratios in tissues. Western blot analysis of cultured mouse embryonic fibroblasts confirmed that both enzymes were actually synthesized as proteins and were localized in both the endoplasmic reticulum and the Golgi apparatus. Pulldown assays revealed that either of CSS2A, CSS2B, and CSS1/ChSy-1 heterogeneously and homogeneously interacts with each other, suggesting that they form a complex of multimers. In vitro glycosyltransferase assays demonstrated a reduced glucuronyltransferase activity in CSS2B and no polymerizing activity in CSS2B co-expressed with CSS1, in contrast to CSS2A co-expressed with CSS1. Radiolabeling analysis of cultured COS-7 cells overexpressing each variant revealed that, whereas CSS2A facilitated CS biosynthesis, CSS2B inhibited it. Molecular modeling of CSS2A and CSS2B provided support for their properties. These findings, implicating regulation of CS chain polymerization by CSS2 variants, provide insight in elucidating the mechanisms of CS biosynthesis.

8th HUPO World Congress: the Human Disease Glycomics/Proteomics Initiative (HGPI) Session 26 September 2009, Toronto, Canada

The Human Disease Glycomics/Proteomics Initiative (HGPI) Session at the HUPO World Congress was held in Toronto on 26 September 2009. In this report, we summarize the presentation of the HGPI workshop as follows: (i) The results of the past HGPI pilot studies (first and second) in which we analyzed N- and O-linked glycans using standard glycoproteins (i.e. first: N-linked glycan analysis of transferrin and IgG; second: O-linked glycan analysis of IgA). (ii) The recent progresses of the current HGPI third pilot study. The third analytical pilot study is in progress to perform the two tasks, which are glycan structural analysis and identification of proteins which carry specific carbohydrate antigen (Lewis X antigen) using cancer cells (i.e. L428, U937, and SK-N-SH), under the theme of "Glyco-Biomarker Discovery". Finally, recently advanced glycomic and glycoproteomic analyses were also reported.

Enrichment method of sulfated glycopeptides by a sulfate emerging and ion exchange chromatography

Sulfated glycoproteins are of growing importance for biomarker discovery, as well as for investigating molecular recognition processes. Mass spectrometry (MS) has become a powerful technique for the characterization of glycans and glycoproteins. However, characterization and detection of sulfated glycopeptides by MS is difficult because of the low abundance and low ionization efficiency of these molecules. To overcome this problem, we developed a novel enrichment procedure for sulfated glycopeptides. The procedure consists of anion exchange chromatography and a sulfate emerging (SE) method which controls the net charge of peptides by utilizing limited proteolyzes and modification with acetohydrazide. Using this procedure, we are able to enrich and characterize the sulfated glycopeptides of bovine luteinizing hormone (bLH). Furthermore, we demonstrate the enrichment and detection of sulfated glycopeptides from a complex mixture comprising human serum spiked with bLH at a concentration of 0.1%.

Wisteria floribunda agglutinin-positive mucin 1 is a sensitive biliary marker for human cholangiocarcinoma

Cholangiocarcinoma (CC) is an aggressive malignant tumor for which useful markers are not presently available for early and precise diagnosis. The aim of this study was therefore to identify a high-performance diagnostic marker with a special focus on glyco-alteration of glycoproteins. In the course of study, we found that Wisteria floribunda agglutinin (WFA) is the best probe to differentiate intrahepatic cholangiocarcinoma (ICC) lesions from normal bile duct epithelia (BDE) (P < 0.0001). The subsequent histochemical study confirmed ICC-specific WFA staining on 165 tissue specimens. On the other hand, the WFA staining was shown to be closely associated with that of MY.1E12 established previously against sialylated mucin 1 (MUC1) by double-staining experiments. Moreover, glyco-alteration of MUC1 could be verified by western blotting of WFA-captured bile samples from patients with CC patients. Thus, we attempted to construct an enzyme-linked immunosorbent assay system for more convenient CC diagnosis, where WFA-coated plates, the specific monoclonal antibody MY.1E12, and the bile specimens from CC including ICC (n = 30) and benign diseases (n = 38) were combined. As a result, CC was clearly distinguished from benign diseases with statistical scores (sensitivity = 90.0%, specificity = 76.3%, and area under the curve = 0.85). As a particular note, the obtained sensitivity is the highest score among those having been so far reported.

CONCLUSION

Our approach focusing significant glyco-alteration of a particular glycoprotein yielded a novel diagnostic system for CC with satisfactory clinical scores.

Renal involvement of monoclonal immunoglobulin deposition disease associated with an unusual monoclonal immunoglobulin A glycan profile

A 38-year-old man was admitted to the hospital for the evaluation of proteinuria, microscopic hematuria, and monoclonal IgA-kappa gammopathy. The initial renal pathological findings showed mesangial proliferative glomerulonephritis with endocapillary proliferation, a necrotizing lesion, and cellular crescent formation accompanied by IgA1-kappa deposition in the mesangium. Neither typical immune-complex deposits nor organized-structure deposits were detected. We diagnosed the patient with monoclonal immunoglobulin deposition disease (MIDD) associated with monoclonal IgA (mIgA). After the initiation of a monthly treatment with melphalan and predonisolone (MP therapy), the patient's serum IgA levels declined, and clinical remission was ultimately achieved. The follow-up renal biopsy showed reduced IgA-kappa staining, and both the endocapillary proliferation and the necrotizing lesion had disappeared. To elucidate the mechanism of IgA deposition, we investigated the glycan profile of the patient's serum mIgA using a mass spectrometry technique. The results revealed an unusual N-glycan profile compared to that of another patient with circulating mIgA lacking renal involvement and that of a healthy control. mIgA deposition in the mesangial area is a rare disease, and the glycan profiling of MIDD with renal involvement has not been reported previously. Thus, the present case suggests that any variation in Ig glycosylation may be a step in the pathogenesis of MIDD with renal involvement and/or contribute to some cases of IgA nephropathy.

Beta3GnT2 (B3GNT2), a major polylactosamine synthase: analysis of B3GNT2-deficient mice

The polylactosamine structure is a fundamental structure of carbohydrate chains and carries a lot of biofunctional carbohydrate epitopes. To investigate the biological function of polylactosamine chains, here we generated and analyzed knockout mice lacking the gene B3gnt2, which encodes a major polylactosamine synthase. In beta1,3-N-acetylglucosaminyltransferase (B3gnt2) B3gnt2-deficient (B3gnt2-/-) mice, the number of polylactosamine structures was markedly lower than in wild-type mice. Flow cytometry, LEL lectin-blotting, and glycan analysis by metabolic labeling demonstrated that the amount of polylactosamine chains on N-glycans was greatly reduced in the tissues of B3gnt2-/- mice. We examined whether immunological abnormalities were present in B3gnt2-/- mice. We screened polylactosamine-carrying molecules of wild-type mice by lectin microarray analysis and found that polylactosamine was present on CD28 and CD19, two established immune co-stimulatory molecules. Polylactosamine levels on these molecules were lower in B3gnt2-/- mice than in wild-type mice. B3gnt2-/- T cells were more sensitive to the induction of intracellular Ca2+ flux on stimulation with anti-CD3epsilon/CD28 antibodies and proliferated more strongly than wild-type T cells. B3gnt2-/- B cells also showed hyperproliferation on BCR stimulation. These results showed that hyperactivation of lymphocytes occurred due to a lack of polylactosamine on receptor molecules in B3gnt2-/- mice. This finding indicates that polylactosamine has an important role in immunological biofunctions. We can therefore attempt to identify the in vivo biological function of glycans using glycogene-deficient mice.

Comparison of methods for profiling O-glycosylation: Human Proteome Organisation Human Disease Glycomics/Proteome Initiative multi-institutional study of IgA1

The Human Proteome Organisation Human Disease Glycomics/Proteome Initiative recently coordinated a multi-institutional study that evaluated methodologies that are widely used for defining the N-glycan content in glycoproteins. The study convincingly endorsed mass spectrometry as the technique of choice for glycomic profiling in the discovery phase of diagnostic research. The present study reports the extension of the Human Disease Glycomics/Proteome Initiative's activities to an assessment of the methodologies currently used for O-glycan analysis. Three samples of IgA1 isolated from the serum of patients with multiple myeloma were distributed to 15 laboratories worldwide for O-glycomics analysis. A variety of mass spectrometric and chromatographic procedures representative of current methodologies were used. Similar to the previous N-glycan study, the results convincingly confirmed the pre-eminent performance of MS for O-glycan profiling. Two general strategies were found to give the most reliable data, namely direct MS analysis of mixtures of permethylated reduced glycans in the positive ion mode and analysis of native reduced glycans in the negative ion mode using LC-MS approaches. In addition, mass spectrometric methodologies to analyze O-glycopeptides were also successful.

Dual specificity of Langerin to sulfated and mannosylated glycans via a single C-type carbohydrate recognition domain

Langerin is categorized as a C-type lectin selectively expressed in Langerhans cells, playing roles in the first line of defense against pathogens and in Birbeck granule formation. Although these functions are thought to be exerted through glycan-binding activity of the C-type carbohydrate recognition domain, sugar-binding properties of Langerin have not been fully elucidated in relation to its biological functions. Here, we investigated the glycan-binding specificity of Langerin using comprehensive glycoconjugate microarray, quantitative frontal affinity chromatography, and conventional cell biological analyses. Langerin showed outstanding affinity to galactose-6-sulfated oligosaccharides, including keratan sulfate, while it preserved binding activity to mannose, as a common feature of the C-type lectins with an EPN motif. By a mutagenesis study, Lys-299 and Lys-313 were found to form extended binding sites for sulfated glycans. Consistent with the former observation, the sulfated Langerin ligands were found to be expressed in brain and spleen, where the transcript of keratan sulfate 6-O-sulfotransferase is expressed. Moreover, such sulfated ligands were up-regulated in glioblastoma relative to normal brain tissues, and Langerin-expressing cells were localized in malignant brain tissues. Langerin also recognized pathogenic fungi, such as Candida and Malassezia, expressing heavily mannosylated glycans. These observations provide strong evidence that Langerin mediates diverse functions on Langerhans cells through dual recognition of sulfated as well as mannosylated glycans by its uniquely evolved C-type carbohydrate-recognition domain.

Strategy for glycoproteomics: identification of glyco-alteration using multiple glycan profiling tools

Glycan alterations of proteins, a common feature of cancer cells, are associated with carcinogenesis, invasion and metastasis. Glycomics, the study of glycans and glycan-binding proteins in various biological systems, is an emerging field in the postgenome and postproteomics era. However, systematic and robust strategies for glycomics are still not fully established because the structural analysis of glycans, which comprise different patterns of branching, various possible linkage positions as well as monomer anomericity, is technically difficult. Here, we introduce a new strategy for glyco-alteration analysis of glycoproteins by using multiple glycan profiling tools. To understand glycan alterations of proteins by correlating the glycosyltransferase expression profile with the actual glycan structure, we systematically used three glycan profiling tools: (1) multiplex quantitative PCR (qPCR) array format for profiling the expression pattern of glycogenes, (2) lectin microarray as a multiplex glycan-lectin interaction analysis system for profiling either a pool of cell glycoproteins or a target glycoprotein, and (3) tandem mass spectrometry for identifying the glycan structure connected to a target glycoprotein. Using our system, we successfully identified glycan alterations on alpha-fetoprotein (AFP), including a novel LacdiNAc structure in addition to previously reported alterations such as alpha1,6 fucosylation.