Endo-α-Mannosidase-Catalyzed Transglycosylation.

In order for facilitating the synthesis of oligosaccharides, transglycosylation reactions mediated by glycoside hydrolases have been studied in various contexts. In this study, we examined the transglycosylating activity of a Golgi endo-α-mannosidase. We prepared various glycosyl donors and acceptors, and recombinant human Golgi endo-α-mannosidase and its various mutants were expressed. The enzyme was able to mediate transglycosylation from α-glycosyl-fluorides. Systematic screening of various point mutants revealed that the E407D mutant had excellent transglycosylation activity and extremely low hydrolytic activity. Substrate specificity analysis revealed that minimum motif required for glycosyl acceptor is Manα1- 2Man. The synthetic utility of the enzyme was demonstrated by generation of a high-mannose-type undecasaccharide (Glc1 Man9 GlcNAc2 ).

A diverse range of bacterial and eukaryotic chitinases hydrolyzes the LacNAc (Galß1-4GlcNAc) and LacdiNAc (GalNAcß1-4GlcNAc) motifs found on vertebrate and insect cells.

There is emerging evidence that chitinases have additional functions beyond degrading environmental chitin, such as involvement in innate and acquired immune responses, tissue remodeling, fibrosis, and serving as virulence factors of bacterial pathogens. We have recently shown that both the human chitotriosidase and a chitinase from Salmonella enterica serovar Typhimurium hydrolyze LacNAc from Galß1-4GlcNAcß-tetramethylrhodamine (LacNAc-TMR (Galß1-4GlcNAcß(CH2)8CONH(CH2)2NHCO-TMR)), a fluorescently labeled model substrate for glycans found in mammals. In this study we have examined the binding affinities of the Salmonella chitinase by carbohydrate microarray screening and found that it binds to a range of compounds, including five that contain LacNAc structures. We have further examined the hydrolytic specificity of this enzyme and chitinases from Sodalis glossinidius and Polysphondylium pallidum, which are phylogenetically related to the Salmonella chitinase, as well as unrelated chitinases from Listeria monocytogenes using the fluorescently labeled substrate analogs LacdiNAc-TMR (GalNAcß1-4GlcNAcß-TMR), LacNAc-TMR, and LacNAcß1-6LacNAcß-TMR. We found that all chitinases examined hydrolyzed LacdiNAc from the TMR aglycone to various degrees, whereas they were less active toward LacNAc-TMR conjugates. LacdiNAc is found in the mammalian glycome and is a common motif in invertebrate glycans. This substrate specificity was evident for chitinases of different phylogenetic origins. Three of the chitinases also hydrolyzed the ß1-6 bond in LacNAcß1-6LacNAcß-TMR, an activity that is of potential importance in relation to mammalian glycans. The enzymatic affinities for these mammalian-like structures suggest additional functional roles of chitinases beyond chitin hydrolysis.

Statin use and risk of cerebral aneurysm rupture: a hospital-based case-control study in Japan.

BACKGROUND: Recent reports have showed that some statins have protective effects in experimental cerebral aneurysm models. We conducted a case-control study to investigate an association between statin use and the rupture risk of cerebral aneurysm in Japanese population. METHODS: This was a multihospital case-control study; cases and controls were collected from 15 hospitals in Japan. Cases consisted of patients with aneurysmal subarachnoid hemorrhage hospitalized from April 2009 to March 2011. Controls were selected from patients who had newly diagnosed unruptured saccular aneurysms from April 2006 to March 2011. The primary exposure of interest was statin use. Multivariable logistic regression was used to assess the relationship between stain use and the rupture risk of cerebral aneurysm. RESULTS: A total of 117 cases and 304 controls were included in the analyses. Statin was used in 9.4% of cases and 26.0% of controls. Controls had a significantly higher rate of use of statin. The use of any statin was associated with cerebral aneurysm rupture after adjustment of potential confounders (adjusted odds ratio: .30, 95% confidence interval: .14-.66). The association was similar in each stratum of total cholesterol level. CONCLUSIONS: This observation from a hospital-based case-control study in Japan suggested that there is inverse relationship between use of statins and cerebral aneurysm rupture. Future clinical studies are needed.

Selective Transarterial Embolization for a Ruptured Persistent Trigeminal Artery Variant Aneurysm.

We report a male patient with a ruptured persistent primitive trigeminal artery variant aneurysm that resulted in a fistula with the cavernous sinus. He presented with left conjunctival hyperemia and exophthalmos. Cerebral angiography revealed a left direct carotid-cavernous fistula; however, a balloon occlusion test determined that the source was actually a ruptured aneurysm located on the trunk of a persistent primitive trigeminal artery. Endovascular trapping of the persistent primitive trigeminal artery was performed, which resulted in fistula occlusion and symptom resolution.

Capillary electrophoresis with three-color fluorescence detection for the analysis of glycosphingolipid metabolism.

A capillary electrophoresis system with an ultrasensitive three-color laser-induced fluorescence detector was constructed for the simultaneous measurement of glycosphingolipids conjugated with a family of BODIPY fluorophores. The compounds were separated by capillary electrophoresis and detected by laser-induced fluorescence excited within a sheath-flow cuvette. Diode-pumped solid-state lasers operating at 473 nm and 532 nm, and a diode laser operating at 633 nm were used to excite glycosphingolipids tagged with BODIPY-FL, BODIPY-TMR, and BODIPY-650/665 fluorophores. Detection limits were 34 ± 1 molecules, 67 ± 7 molecules, and 36 ± 13 molecules of BODIPY-FL, BODIPY-TMR, and BODIPY-650/665 labeled glycosphingolipids. Separation efficiencies were typically one million theoretical plates. To test the ability of the system to analyze cellular contents in an in vitro biological model, differentiated PC12 cells were co-incubated with BODIPY-FL, BODIPY-TMR, and BODIPY-650/665 labeled lactosylceramide substrates. Cells were homogenized. The metabolic products originating from the glycosphingolipid substrates were simultaneously analyzed using the system.

Elucidation of the sugar recognition ability of the lectin domain of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase 3 by using unnatural glycopeptide substrates.

Mucin-type glycosylation [α-N-acetyl-D-galactosamine (α-GalNAc)-O-Ser/Thr] on proteins is initiated biosynthetically by 16 homologous isoforms of GalNAc-Ts (uridine diphosphate-GalNAc:polypeptide N-acetylgalactosaminyltransferases). All the GalNAc-Ts consist of a catalytic domain and a lectin domain. Previous reports of GalNAc-T assays toward peptides and α-GalNAc glycopeptides showed that the lectin domain recognized the sugar on the substrates and affected the reaction; however, the details are not clear. Here, we report a new strategy to give insight on the sugar recognition ability and the function of the GalNAc-T3 lectin domain using chemically synthesized natural-type (α-GalNAc-O-Thr) and unnatural-type [ß-GalNAc-O-Thr, α-Fuc-O-Thr and ß-GlcNAc-O-Thr] MUC5AC glycopeptides. GalNAc-T3 is one of isoforms expressed in various organs, its substrate specificity extensively characterized and its anomalous expression has been identified in several types of cancer (e.g. pancreas and stomach). The glycopeptides used in this study were designed based on a preliminary peptide assay with a sequence derived from the MUC5AC tandem repeat. Through GalNAc-T3 and lectin-inactivated GalNAc-T3, competition assays between the glycopeptide substrates and product analyses (MALDI-TOF MS, RP-HPLC and ETD-MS/MS), we show that the lectin domain strictly recognized GalNAc on the substrate and this specificity controlled the glycosylation pathway.

Thiogalactopyranosides are resistant to hydrolysis by α-galactosidases.

Fluorescently tagged glycosides containing terminal α(1→3) and α(1→4)-linked thiogalactopyranosides have been prepared and tested for resistance to hydrolysis by α-galactosidases. Eight fluorescent glycosides containing either galactose or 5-thiogalactose as the terminal sugar were enzymatically synthesized using galactosyltransferases, with lactosyl glycosides as acceptors and UDP-galactose or UDP-5'-thiogalactose, respectively, as donors. The glycosides were incubated with human α-galactosidase A (CAZy family GH27, a retaining glycosidase), Bacteroides fragilis α-1,3-galactosidase (GH110, an inverting glycosidase), or homogenates of MCF-7 human breast cancer cells or NG108-15 rat glioma cells. Substrate hydrolysis was monitored by capillary electrophoresis with fluorescence detection. All compounds containing terminal O-galactose were readily degraded. Their 5-thiogalactose counterparts were resistant to hydrolysis by human α-galactosidase A and the enzymes present in the cell extracts. B. fragilis α-1,3-galactosidase hydrolyzed both thio- and O-galactoside substrates; however, the thiogalactosides were hydrolyzed at only 1-3 % of the rate of O-galactosides. The hydrolytic resistance of 5-thiogalactose was also confirmed by an in vivo study using cells in culture. The results suggest that 5-thiogalactosides may be useful tools for the study of anabolic pathways in cell extracts or in single cells.

Rupture of Anterior Communicating Artery Aneurysm after Intravenous Thrombolysis for Acute Ischemic Stroke: A Case Report.

Objective: Rupture of intracranial aneurysms after tissue plasminogen activator (t-PA) administration for acute ischemic stroke with an unruptured cerebral aneurysm is rare. We report a case of ruptured cerebral aneurysm after t-PA administration. Case Presentation: A 74-year-old woman with dysarthria and left hemiparesis was admitted to our hospital, and acute lacunar infarction was found in the right corona radiata. One hour after t-PA administration, she complained of sudden headache and nausea, and her consciousness level deteriorated. Subarachnoid hemorrhage due to rupture of the anterior communicating aneurysm was confirmed and coil embolization was performed. Conclusion: T-PA administration for acute ischemic stroke with an unruptured cerebral aneurysm risks rupture of the cerebral aneurysm, and careful judgment is needed in each case.

Carotid Cavernous Fistula during Thrombectomy for Acute Ischemic Stroke: A Case Report.

Objective: We report a rare complication, carotid cavernous fistula (CCF), due to vessel perforation during thrombectomy for acute ischemic stroke (AIS). Case Presentation: An 88-year-old woman underwent thrombectomy for left C4 occlusion of the internal carotid artery. There was strong resistance at the medial C4 while the microguidewire was guided distally, and a CCF was found after deploying and retrieving the stent. It was thought to have been caused by perforation due to intracranial atherosclerotic stenosis of the internal carotid artery. Conclusion: During thrombectomy for intracranial large vessel occlusion underlying intracranial atherosclerotic stenosis, the risk of vascular injury should be kept in mind.

Brainstem Venous Congestion Due to Transverse-sigmoid Sinus Dural Arteriovenous Fistula: Case Report and Literature Review.

Brainstem venous congestion due to dural arteriovenous fistula (dAVF) can mimic brainstem glioma and infarction. We report a case of a 56-year-old woman with a transverse-sigmoid sinus (TS) dAVF. On MRI, she presented with brainstem edema that was difficult to distinguish from brainstem glioma and infarction. She was referred to our hospital for mild dysarthria with right hemiparesis and a suspected left pontine glioma. On MRI, contrast enhancement of the lesion was demarcated by the pontine raphe, and the ipsilateral vein of Rosenthal was dilated. Cerebral angiography revealed TS dAVF with an isolated sinus. Transarterial followed by transvenous coil embolization was performed to reduce shunt flow, resulting in symptom improvement and normal findings on MRI and cerebral angiography. Brainstem venous congestion due to TS dAVF is as rare as adult brainstem glioma. Differentiating the above-mentioned three diseases on the basis of diagnostic imaging findings and clinical course is necessary for appropriate and timely treatment.

Unexpected tolerance of glycosylation by UDP-GalNAc:polypeptide alpha-N-acetylgalactosaminyltransferase revealed by electron capture dissociation mass spectrometry: carbohydrate as potential protective groups.

UDP-GalNAc:polypeptide alpha-N-acetylgalactosaminyltransferases (ppGalNAcTs, EC 2.4.1.41), a family of key enzymes that initiate posttranslational modification with O-glycans in mucin synthesis by introduction of alpha-GalNAc residues, are structurally composed of a catalytic domain and a lectin domain. It has been known that multiple Ser/Thr residues are assigned in common mucin glycoproteins as potential O-glycosylation sites and more than 20 distinct isoforms of this enzyme family contribute to produce densely O-glycosylated mucin glycoproteins. However, it seems that the functional role of the lectin domain of ppGalNAcTs remains unclear. We considered that electron capture dissociation mass spectrometry (ECD-MS), a promising method for highly selective fragmentation at peptide linkages of glycopeptides to generate unique c and z series of ions, should allow for precise structural characterization to uncover the mechanism in O-glycosylation of mucin peptides by ppGalNAcTs. In the present study, it was demonstrated that a system composed of an electrospray source, a linear RFQ ion trap that isolates precursor ions, the ECD device, and a TOF mass spectrometer is a nice tool to identify the preferential O-glycosylation sites without any decomposition of the carbohydrate moiety. It should be noted that electrons used for ECD are accelerated within a range from 1.75 to 9.75 eV depending on the structures of glycopeptides of interest. We revealed for the first time that additional installation of a alpha-GalNAc residue at potential glycosylation sites by ppGalNAcT2 proceeds smoothly in various unnatural glycopeptides having alpha-Man, alpha-Fuc, and beta-Gal residues as well as alpha-GalNAc residues. The results may suggest that ppGalNAcT2 did not differentiate totally presubstituted sugar residues in terms of configuration of functional groups, d-, l-configuration, and even alpha-, beta-stereochemistry at an anomeric carbon atom when relatively short synthetic peptides were employed for the acceptor substrates. Unexpected characteristics of ppGalNAcT2 motivated us to challenge site-directed installation of alpha-GalNAc residues at desired position(s) by protecting some hydroxyl groups of Thr/Ser residues with selectively removable sugars, notably a novel concept as "carbohydrate as protective groups", toward a goal of the systematic chemical and enzymatic synthesis of biologically important mucin glycopeptides.

A new strategy for the chemoenzymatic synthesis of glycopeptides by De-O-acetylation with an esterase and glycosylations with glycosyltransferases.

Glycopeptides are fragments of glycoproteins and are important in evaluating the biological roles of carbohydrates in glycoproteins. Fmoc solid-phase peptide synthesis using acetyl-protected glycosylated amino acids is a common strategy for the preparation of glycopeptides, but this approach normally requires chemical de-O-acetylation with a base that ß-eliminates sugar residues and epimerizes the peptide backbone. Here we demonstrate a facile new chemoenzymatic synthetic strategy for glycopeptides, using an esterase for the de-O-acetylation of sugar residues and glycosyltransferases for successive sugar elongations at neutral pH.

Products of Chemoenzymatic Synthesis Representing MUC1 Tandem Repeat Unit with T-, ST- or STn-antigen Revealed Distinct Specificities of Anti-MUC1 Antibodies.

Anti-mucin1 (MUC1) antibodies have long been used clinically in cancer diagnosis and therapy and specific bindings of some of them are known to be dependent on the differential glycosylation of MUC1. However, a systematic comparison of the binding specificities of anti-MUC1 antibodies was not previously conducted. Here, a total of 20 glycopeptides including the tandem repeat unit of MUC1, APPAHGVTSAPDTRPAPGSTAPPAHGV with GalNAc (Tn-antigen), Galß1-3GalNAc (T-antigen), NeuAcα2-3Galß1-3GalNAc (sialyl-T-antigen), or NeuAcα2-6GalNAc (sialyl-Tn-antigen) at each threonine or serine residue were prepared by a combination of chemical glycopeptide synthesis and enzymatic extension of carbohydrate chains. These glycopeptides were tested by the enzyme-linked immunosorbent assay (ELISA) for their capacity to bind 13 monoclonal antibodies (mAbs) known to be specific for MUC1. The results indicated that anti-MUC1 mAbs have diverse specificities but can be classified into a few characteristic groups based on their binding pattern toward glycopeptides in some cases having a specific glycan at unique glycosylation sites. Because the clinical significance of some of these antibodies was already established, the structural features identified by these antibodies as revealed in the present study should provide useful information relevant to their further clinical use and the biological understanding of MUC1.

Intraventricular Epithelioid Glioblastoma: A Case Report.

BACKGROUND: Epithelioid glioblastoma, a high-grade, diffuse astrocytic tumor variant, comprises closely packed epithelioid cells and rhabdoid cells. This rare tumor usually develops in the cerebral cortex and diencephalon; however, in the case reported here, it was located intraventricularly. CASE DESCRIPTION: A 47-year-old woman was referred to our hospital with a right intraventricular mass that had rapidly increased in size. On discovery of the tumor 3 years earlier at the referring hospital, the mass was small, calcified, and attached to the periventricular parenchyma. Over the next 2 years, the mass grew slowly, as observed on periodic magnetic resonance imaging scans. Forty days before the referral, the patient experienced headache and nausea, and marked growth and intratumoral hemorrhage were visible on a computed tomography scan of the head. The tumor was partially removed via a superior parietal lobule corticotomy. Histopathological examination confirmed an isocitrate dehydrogenase-wild-type epithelioid glioblastoma with a BRAF V600E mutation, but the original slow-growing lesion was no longer detected. Consequently, we assume that in this case, a low-grade glioma transformed into an aggressively malignant epithelioid glioblastoma. CONCLUSIONS: We present the first case of an intraventricular epithelioid glioblastoma that might have arisen from a low-grade glioma with calcification. We recommend including this tumor variant in the differential diagnosis of lateral ventricle tumors.

Arsenic trioxide sensitizes glioblastoma to a myc inhibitor.

Glioblastoma multiforme (GBM) is associated with high mortality due to infiltrative growth and recurrence. Median survival of the patients is less than 15 months, increasing requirements for new therapies. We found that both arsenic trioxide and 10058F4, an inhibitor of Myc, induced differentiation of cancer stem-like cells (CSC) of GBM and that arsenic trioxide drastically enhanced the anti-proliferative effect of 10058F4 but not apoptotic effects. EGFR-driven genetically engineered GBM mouse model showed that this cooperative effect is higher in EGFRvIII-expressing INK4a/Arf-/- neural stem cells (NSCs) than in control wild type NSCs. In addition, treatment of GBM CSC xenografts with arsenic trioxide and 10058F4 resulted in significant decrease in tumor growth and increased differentiation with concomitant decrease of proneural and mesenchymal GBM CSCs in vivo. Our study was the first to evaluate arsenic trioxide and 10058F4 interaction in GBM CSC differentiation and to assess new opportunities for arsenic trioxide and 10058F4 combination as a promising approach for future differentiation therapy of GBM.

In vitro Biochemical Characterization of All Barley Endosperm Starch Synthases.

Starch is the main storage polysaccharide in cereals and the major source of calories in the human diet. It is synthesized by a panel of enzymes including five classes of starch synthases (SSs). While the overall starch synthase (SS) reaction is known, the functional differences between the five SS classes are poorly understood. Much of our knowledge comes from analyzing mutant plants with altered SS activities, but the resulting data are often difficult to interpret as a result of pleitropic effects, competition between enzymes, overlaps in enzyme activity and disruption of multi-enzyme complexes. Here we provide a detailed biochemical study of the activity of all five classes of SSs in barley endosperm. Each enzyme was produced recombinantly in E. coli and the properties and modes of action in vitro were studied in isolation from other SSs and other substrate modifying activities. Our results define the mode of action of each SS class in unprecedented detail; we analyze their substrate selection, temperature dependence and stability, substrate affinity and temporal abundance during barley development. Our results are at variance with some generally accepted ideas about starch biosynthesis and might lead to the reinterpretation of results obtained in planta. In particular, they indicate that granule bound SS is capable of processive action even in the absence of a starch matrix, that SSI has no elongation limit, and that SSIV, believed to be critical for the initiation of starch granules, has maltoligosaccharides and not polysaccharides as its preferred substrates.

Suppression of cerebral aneurysm formation in rats by a tumor necrosis factor-α inhibitor.

OBJECT: Although cerebral aneurysmal subarachnoid hemorrhage is a devastating disease for humans, effective medical treatments have not yet been established. Recent reports have shown that regression of some inflammatory-related mediators has protective effects in experimental cerebral aneurysm models. This study corroborated the effectiveness of tumor necrosis factor-α (TNF-α) inhibitor for experimentally induced cerebral aneurysms in rats. METHODS: Five-week-old male rats were prepared for induction of cerebral aneurysms and divided into 3 groups, 2 groups administered different concentrations of a TNF-α inhibitor (etanercept), and 1 control group. One month after aneurysm induction, 7-T MRI was performed. The TNF-α inhibitor groups received subcutaneous injection of 25 µg or 2.5 µg of etanercept, and the control group received subcutaneous injection of normal saline every week. The TNF-α inhibitor administrations were started at 1 month after aneurysm induction to evaluate its suppressive effects on preexisting cerebral aneurysms. Arterial circles of Willis were obtained and evaluated 3 months after aneurysm induction. RESULTS: Rats administered a TNF-α inhibitor experienced significant increases in media thickness and reductions in aneurysmal size compared with the control group. Immunohistochemical staining showed that treatment with a TNF-α inhibitor suppressed matrix metalloproteinase (MMP)-9 and inducible nitric oxide synthase (iNOS) expression through the luminal surface of the endothelial cell layer, the media and the adventitia at the site of aneurysmal formation, and the anterior cerebral artery-olfactory artery bifurcation. Quantitative polymerase chain reaction also showed suppression of MMP-9 and iNOS by TNF-α inhibitor administration. CONCLUSIONS: Therapeutic administration of a TNF-α inhibitor significantly reduced the formation of aneurysms in rats. These data also suggest that TNF-α suppression reduced some inflammatory-related mediators that are in the downstream pathway of nuclear factor-κB.

Human chitotriosidase CHIT1 cross reacts with mammalian-like substrates.

Humans do not synthesize chitin, yet they produce a number of active and inactive chitinases. One of the active enzymes is chitotriosidase whose serum levels are elevated in a number of diseases such as Gaucher's disease and upon fungal infection. Since the biological role of chitotriosidase in disease pathogenesis is not understood we screened a panel of mammalian GlcNAc-containing glycoconjugates as alternate substrates. LacNAc and LacdiNAc-terminating substrates are hydrolyzed, the latter with a turnover comparable to that of pNP-chitotriose. Glycolipids or glycoproteins with LacNAc and LacdiNAc represent potential chitinase substrates and the subsequent alteration of glycosylation pattern could be a factor in disease pathogenesis.