[A case of intragastric wall abscess formation during bevacizumab combined chemotherapy]

A 38-year-old man was given a diagnosis of as sigmoid colon cancer and underwent sigmoid colectomy. Post-operative pathological staging was stage IIIb. He then underwent adjuvant chemotherapy. One year and 4 months after the surgery, CT scans revealed multiple liver and lung metastases. He was given mFOLFOX6+bevacizumab, which was changed later to FOLFIRI+bevacizumab. After these chemotherapies, he was admitted to the hospital due to sudden abdominal pain and high grade fever. Obstructive jaundice was initially diagnosed, but detailed study of initial CT revealed intragastric wall abscess. After the drainage of the abscess, his conditions improved. We speculated that the abscess formation was caused by mucosal damage due to bevacizumab.

An assay for α 1,6-fucosyltransferase (FUT8) activity based on the HPLC separation of a reaction product with fluorescence detection

N-Glycans with an α-fucose unit linked to the 6-position of the innermost GlcNAc are widely distributed among the animal kingdom, from worms and insects to human. This α1,6-linked fucosyl residue, frequently referred to as a core fucose, is formed via the action of an α1,6-fucosyltransferase, the mammalian ortholog which is systematically called FUT8. In mammals, it is well known that the extent of core-fucosylation in cellular and secreted glycoproteins varies, e.g., according to differentiation and carcinogenesis of the cells. This chapter describes a method for the sensitive and quantitative assay of FUT8 activity using a fluorescence-labeled oligosaccharyl asparagine derivative as the glycosyl acceptor substrate.

Measurement of peroxiredoxin-4 serum levels in rat tissue and its use as a potential marker for hepatic disease

Peroxiredoxin (Prx)-4, a secretable endoplasmic reticulum (ER)-resident isoform of the mammalian Prx family, functions as a thioredoxin-dependent peroxidase. It is acknowledged that Prx-4 plays a role in the detoxification of hydrogen peroxide, and potentially other peroxides, which may be generated during the oxidative folding of proteins and oxidative stress in the ER. The present study was undertaken in order to specifically quantify the tissue levels of Prx-4. To accomplish this, an enzyme-linked immunosorbent assay was developed using a specific polyclonal antibody produced by immunizing a rabbit with native recombinant rat Prx-4 protein. The assay was used to detect Prx-4 in the range of 0.1 and 10 ng/ml, and to investigate tissue distribution in rats. Using this immunoassay, we found that the serum levels of Prx-4 were substantially lower in asymptomatic Long-Evans Cinnamon rats, a rat model of Wilson's disease, compared to normal rats. In addition, the treatment of rat hepatoma cells with N-acetylcysteine led to a significant increase in the release of Prx-4 protein into the medium; thus, it appears likely that the secretion of Prx-4 is associated with the redox state within cells. These results suggest that serum Prx-4 has potential for use as a biomarker for hepatic oxidative stress.

Multiple potential regulatory sites of TLR4 activation induced by LPS as revealed by novel inhibitory human TLR4 mAbs

Recognition of LPS by the toll-like receptor 4 (TLR4)/MD-2 complex is a trigger of innate immune defense against bacterial invasion. However, excessive immune activation by this receptor complex causes septic shock and autoimmunity. Manipulation of TLR4 signaling represents a potential therapy that would avoid the detrimental consequences of unnecessary immune responses. In this study, we established two novel mAbs that inhibit LPS-induced human TLR4 activation. HT52 and HT4 mAbs inhibited LPS-induced nuclear factor-κB activation in TLR4/MD-2-expressing Ba/F3-transfected cells and cytokine production and up-regulation of CD86 in the human cell line U373 and PBMCs. These inhibitory activities were stronger than that of HTA125 mAb, which we previously reported. Immunofluorescent and biochemical studies using TLR4 deletion mutants revealed that HT52 and HT4 recognized spatially distinct regions on TLR4 irrespective of MD-2 association. The HT52 and HTA125 epitopes were localized within aa 50-190, while the HT4 epitope was formed only by the full length of TLR4. In addition, we demonstrated that HT52 and HT4 failed to compete with LPS for binding to TLR4/MD-2 but inhibited LPS-induced TLR4 internalization. Inhibitory activities were not due to the interaction with the Fcγ receptor CD32. Our finding that binding of mAbs to at least two distinct regions on TLR4 inhibits LPS-dependent activation provides a novel method for manipulating TLR4 activation and also a rationale for designing drugs targeted to TLR4.

[Systemic amyloidosis associated with IgD-λ multiple myeloma]

We describe here a case of systemic amyloidosis associated with IgD multiple myeloma. A 59-year-old man was admitted to our hospital in April 2009, because of macroglossia and swelling in both wrists and fingers. He had difficulty moving his limbs and was aware of peripheral neuropathy. Skin biopsy revealed extensive deposition of amyloidosis, which was positive by Congo red staining. Laboratory findings were as follows: serum electrophoresis revealed IgD λ monoclonal protein, and Bence-Jones protein was detected. Monoclonal IgD protein had a concentration of 727 mg/dl, and a bone marrow aspiration revealed 49.6% of plasma cells. These findings led to a diagnosis of IgD multiple myeloma with systemic amyloidosis. The patient was treated with MP (melphalan and methylprednisolone), high-dose dexamethasone and VAD therapy (vincristine, adriamycin and dexamethasone), but systemic amyloidosis progressed, and his general condition deteriorated. Coexistence of IgD multiple myeloma and systemic amyloidosis is rare, and accumulation of case reports is needed to gain a better understanding of this condition.

Different consequences of reactions with hydrogen peroxide and t-butyl hydroperoxide in the hyperoxidative inactivation of rat peroxiredoxin-4

Eukaryotic typical 2-Cys type peroxiredoxin (Prx) is inactivated by hyperoxidation of the peroxidatic cysteine to a sulphinic acid in a catalytic cycle-dependent manner. This inactivation process has been well documented for cytosolic isoforms of Prx. However, such a hyperoxidative inactivation has not fully been investigated in Prx-4, a secretable endoplasmic reticulum-resident isoform, in spite of being a typical 2-Cys type, and details of this process are reported herein. As has been observed in many peroxiredoxins, the peroxidase activity of Prx-4 was almost completely inhibited in the reaction with t-butyl hydroperoxide. On the other hand, when H(2)O(2) was used as the substrate, the peroxidase activity significantly remained after oxidative damage. In spite of these different consequences, mass spectrometric analyses indicated that both reactions resulted in the same oxidative damage, i.e. sulphinic acid formation at the peroxidatic cysteine, suggesting that another cysteine in the active site confers the peroxidase activity. As suggested by the analyses using cysteine-substituted mutants sulphinic acid formation at the peroxidatic cysteine may play a role in the development of the possible alternative mechanism, thereby sustaining the peroxidase activity that prefers H(2)O(2).

Suppressive effect of sulindac on branch duct-intraductal papillary mucinous neoplasms

BACKGROUND

When considering surgery for branch duct-intraductal papillary mucinous neoplasms (BD-IPMNs) with suspected malignancy, it should be recognized that these lesions are frequently multifocal and are usually found in elderly patients with potential comorbidities that could affect the outcome of surgery. Clinical trials of chemoprevention have been conducted for a wide variety of malignancies.

METHODS

Twenty-two BD-IPMN patients participated in the trial at our institution from June 2004 to January 2007. Ten of the 22 patients who rejected surgical therapy although their lesions or clinical symptoms met the criteria for surgical resection of the International Association of Pancreatology guidelines were assigned to the treatment group. Sulindac (150 mg twice daily) and omeprazole (20 mg once daily) were administered to these patients for 18 months. The remaining 12 patients comprised the control group. Branch duct diameter and mural nodule heights were monitored by either magnetic resonance cholangiopancreatography (MRCP) or computed tomography (CT) and by endoscopic ultrasonography (EUS).

RESULTS

Both branch duct diameter and mural nodule height of BD-IPMNs in the treatment group were significantly reduced, while those in the control group were unchanged. Immunohistochemical staining for cyclooxygenase-1 and -2 was negative in hyperplasia, adenoma and carcinoma portions of resected pancreatic specimens but was clearly positive for glutathione-S-transferase pi (GST-pi), suggesting that GST-pi is a putative target molecule for sulindac.

CONCLUSIONS

Although a larger scale randomized controlled study is needed in future, the present results suggest the promise of chemoprevention of carcinoma derived from BD-IPMNs by sulindac.

[Mucinous cystic adenoma of the pancreas with short-term morphological changes due to hemorrhage]

A 31-year-old woman with epigastric pain was given a diagnosis of a pseudocyst associated with pancreatitis. Despite treatment, symptoms did not completely improve and she was referred to our hospital. Since imaging examinations demonstrated findings characteristic of mucinous cystic neoplasm, the lesion was resected. Histopathologic examinations revealed mucinous cystic adenoma. Remains of intracystic hemorrhage were evident and short-term morphological changes were presumed to be associated with hemorrhage.

Bidirectional N-acetylglucosamine transfer mediated by beta-1,4-N-acetylglucosaminyltransferase III

beta-1,4-N-Acetylglucosaminyltransferase III (GnT-III) catalyzes the formation of the bisecting GlcNAc and plays a regulatory role in the biosynthesis of the N-linked oligosaccharide. In this study, we examined whether the glycosyl transfer catalyzed by GnT-III is reversible, and, in addition, investigated the equilibrium of the GnT-III-catalyzed reaction. Incubation of the agalactosyl-bisected biantennary oligosaccharide with GnT-III in the presence of the sufficiently high concentration of uridine diphosphate (UDP) resulted in conversion of the bisected oligosaccharide into the nonbisected one. This reaction was accompanied by the stoichiometric formation of UDP-GlcNAc, which appeared to result from the transfer of GlcNAc from the oligosaccharide to UDP. Thus, these results indicate that GnT-III is capable of perceivably catalyzing the reverse reaction in vitro, as found in some glycosyltransferases. When the equilibrium of the reaction was kinetically analyzed, it was found that the state of the equilibrium is greatly displaced toward the formation of the bisecting GlcNAc. In terms of free energy change, as estimated, the reaction by GnT-III can be comparable to the hydrolysis of ATP. Although GnT-III catalyzes bidirectional transfer of GlcNAc between the oligosaccharide and UDP, the removal of the bisecting GlcNAc is unlikely in vivo, due to the displacement of the equilibrium. It is known that equilibria of certain glycosyltransferase reactions are not biased as greatly as the case of GnT-III, and thus it seems likely that there are a variety of equilibrium states in glycosyltransferase reactions. In living cells, the assembly of oligosaccharides could be regulated by not only rate control but also equilibrium control.

A Phase I trial of arterial infusion chemotherapy with gemcitabine and 5-fluorouracil for unresectable advanced pancreatic cancer after vascular supply distribution via superselective embolization

BACKGROUND

We previously reported that arterial infusion chemotherapy improved the response rate and survival of the patients with pancreatic cancer at advanced stages in an open trial. We conducted a Phase I trial of arterial infusion chemotherapy with gemcitabine and 5-fluorouracil for advanced pancreatic cancer after vascular supply distribution via superselective embolization.

METHODS

Patients were treated after arterial embolization for hemodynamic change to restrict the blood flow into the pancreas (mainly to the great pancreatic artery and the caudal pancreatic artery). Arterial infusion chemotherapy consisted of gemcitabine in doses that were increased from 600 to 1000 mg/m(2) in subsequent cohorts on Day 1 plus continuous infusion of 5-fluorouracil 300 mg/m(2)/day on Days 1-5 every 2 weeks. Result Twelve patients were enrolled. The maximum tolerated dose of gemcitabine was determined to be Level 3 (1000 mg/m(2)). Only very mild hematological and non-hematological toxicities were noted. The overall response rate was 33.3%. The median survival time was 22.7 (95% CI; 9.5-24.5) months and the 1- and 2-year overall survival rates were 83.3 and 25.0%, respectively.

CONCLUSION

Arterial infusion chemotherapy using 1000 mg/m(2) gemcitabine on Day 1 and 300 mg/m(2)/day 5-fluorouracil on Days 1-5 every 2 weeks warrants a Phase II study.

Crystal structure of mammalian α1,6-fucosyltransferase, FUT8

Mammalian alpha1,6-fucosyltransferase (FUT8) catalyses the transfer of a fucose residue from a donor substrate, guanosine 5'-diphosphate-beta-L-fucose to the reducing terminal N-acetylglucosamine (GlcNAc) of the core structure of an asparagine-linked oligosaccharide. Alpha1,6-fucosylation, also referred to as core fucosylation, plays an essential role in various pathophysiological events. Our group reported that FUT8 null mice showed severe growth retardation and emphysema-like lung-destruction as a result of the dysfunction of epidermal growth factor and transforming growth factor-beta receptors. To elucidate the molecular basis of FUT8 with respect to pathophysiology, the crystal structure of human FUT8 was determined at 2.6 A resolution. The overall structure of FUT8 was found to consist of three domains: an N-terminal coiled-coil domain, a catalytic domain, and a C-terminal SH3 domain. The catalytic region appears to be similar to GT-B glycosyltransferases rather than GT-A. The C-terminal part of the catalytic domain of FUT8 includes a Rossmann fold with three regions that are conserved in alpha1,6-, alpha1,2-, and protein O-fucosyltransferases. The SH3 domain of FUT8 is similar to other SH3 domain-containing proteins, although the significance of this domain remains to be elucidated. The present findings of FUT8 suggest that the conserved residues in the three conserved regions participate in the Rossmann fold and act as the donor binding site, or in catalysis, thus playing key roles in the fucose-transferring reaction.

Clinical and endoscopic features of acute hemorrhagic rectal ulcer

BACKGROUND

Acute hemorrhagic rectal ulcer (AHRU) has increasingly been reported in Japan, whereas it has rarely been reported in the English literature and is not yet established as a disease entity. The aim of this study was to elucidate clinical and endoscopic characteristics of patients with AHRU.

METHODS

We enrolled 20 patients with 26 ulcers diagnosed as AHRU in our department between January 2001 and October 2005. Clinical features such as the underlying disorder, Karnofsky performance status (PS), and presence or absence of anticoagulant or antiplatelet therapy, as well as endoscopic findings and type of bleeding, were evaluated. Strategies for hemostasis were also reviewed.

RESULTS

The most prevalent underlying disorder was diabetes mellitus, and the number of bedridden patients with PS 4 was relatively high. In addition, more than half of the patients had been treated with anticoagulant or antiplatelet agents. Endoscopically, ulcers were characteristically solitary and irregularly shaped, and they did not show any typical localization pattern. As a hemostatic strategy, clipping alone showed a favorable result, with a hemostatic success rate as high as 76.9%.

CONCLUSIONS

This study may support the establishment of AHRU as a new clinical entity. In aged patients being treated with anticoagulant or antiplatelet agents, especially bedridden patients using aspirin, the possible appearance of this disease should be kept in mind.

Expression of foreign type I ribulose-1,5-bisphosphate carboxylase/ oxygenase (EC 4.1.1.39) stimulates photosynthesis in cyanobacterium Synechococcus PCC7942 cells

A reporter gene assay revealed that promoters derived from Synechococcus PCC7942 (S.7942) psbAI and Synechocystis PCC6803 (S.6803) psbAII were suitable for the expression of foreign ribulose-bisphosphate carboxylase (RuBisCO; EC 4.1.1.39) in S.7942 cells. Transformational vectors with a promoter and a foreign RuBisCO gene, cvrbc originated from Allochromatium vinosum, were constructed on a binary vector, pUC303, and introduced to S.7942 cells. When the cvrbc was expressed with the S.7942 psbAI promoter, the total RuBisCO activity increased 2.5- to 4-fold than that of the wild type cell. The S.6803 psbAII promoter increased the activity of the transformant 1.5-2 times of that of wild type cell. There was a significant increase in the rate of photosynthesis depending on the increase of RuBisCO activity. The maximum rate of photosynthesis of the transformant cell was 1.63 times higher than that of the wild type under the illumination of 400 micromol m(-2) s(-1), at 20 mM bicarbonate and at 30 degrees C. Although the photosynthesis of the higher plant is limited by the ability of photosystems under high irradiance and the high CO(2 )concentration, that of the S.7942 cell is limited by the RuBisCO activity, even at high CO(2) concentrations and under high irradiance.

Cell-Cell Interaction-dependent Regulation of N-Acetylglucosaminyltransferase III and the Bisected N-Glycans in GE11 Epithelial Cells

Changes in oligosaccharide structures are associated with numerous physiological and pathological events. In this study, the effects of cell-cell interactions on N-linked oligosaccharides (N-glycans) were investigated in GE11 epithelial cells. N-glycans were purified from whole cell lysates by hydrazinolysis and then detected by high performance liquid chromatography and mass spectrometry. Interestingly, the population of the bisecting GlcNAc-containing N-glycans, the formation of which is catalyzed by N-acetylglucosaminyltransferase III (GnT-III), was substantially increased in cells cultured under dense conditions compared with those cultured under sparse conditions. The expression levels and activities of GnT-III but not other glycosyltransferases, such as GnT-V and alpha1,6-fucosyltransferase, were also consistently increased in these cells. However, this was not observed in mouse embryonic fibroblasts or MDA-MB231 cells, in which E-cadherin is deficient. In contrast, perturbation of E-cadherin-mediated adhesion by treatment with EDTA or a neutralizing anti-E-cadherin antibody abolished the up-regulation of expression of GnT-III. Furthermore, we observed the significant increase in GnT-III activity under dense growth conditions after restoration of the expression of E-cadherin in MDA-MB231 cells. Our data together indicate that a E-cadherin-dependent pathway plays a critical role in regulation of GnT-III expression. Given the importance of GnT-III and the dynamic regulation of cell-cell interaction during tissue development and homeostasis, the changes in GnT-III expression presumably contribute to intracellular signaling transduction during such processes.

beta1,4-N-Acetylglucosaminyltransferase III potentiates beta1 integrin-mediated neuritogenesis induced by serum deprivation in Neuro2a cells

Aspects of the biological significance of the bisecting N-acetylglucosamine (GlcNAc) structure on N-glycans introduced by beta1,4-N-acetylglucosaminyltransferase III (GnT-III) in Neuro2a cell differentiation are demonstrated. The overexpression of GnT-III in the cells led to the induction of axon-like processes with numerous neurites and swellings, in which beta1 integrin was localized, under conditions of serum starvation. This enhancement in neuritogenesis was suppressed by either the addition of a bisecting GlcNAc-containing N-glycan or erythroagglutinating phytohemagglutinin (E(4)-PHA), which preferentially recognizes the bisecting GlcNAc. GnT-III-promoted neuritogenesis was also significantly perturbed by treatment with a functional blocking anti-beta1 integrin antibody. In fact, beta1 integrin was found to be one of the target proteins of GnT-III, as confirmed by a pull-down assay with E(4)-PHA. These data suggest that N-glycans with a bisecting GlcNAc on target molecules, such as beta1 integrin, play important roles in the regulation of neuritogenesis.

Risk factors for dysbaric osteonecrosis

OBJECTIVES

Dysbaric osteonecrosis (DON) is a complication of ineffective decompression following exposure to high-pressure environments. This study was designed to determine risk factors for the occurrence of DON in divers.

METHODS

Fifty-six male divers received skeletal examinations by radiography to assess the occurrence of DON. A questionnaire was used to obtain clinical and diving information, including diving experience and maximum diving depth. Blood samples were collected to analyse the levels of plasminogen activator inhibitor (PAI)-1, cholesterol, triglyceride, low-density lipoprotein, very low-density lipoprotein, high-density lipoprotein, apolipoprotein A1 and apolipoprotein B.

RESULTS

Lesions of DON were detected in 31 of the 56 (55%) divers. Multivariate logistic regression analysis showed that high levels of PAI-1, a coagulation marker (odds ratio 4.281; P=0.0296) and great maximum diving depth (odds ratio 5.627; P=0.0231) were independent predictors of DON.

CONCLUSIONS

This study has shown the presence of coagulation abnormality in divers with DON. This result suggests that a pharmacological approach incorporating the use of an anticoagulant may represent a potential strategy for the prevention of DON.

A specific detection of GlcNAcbeta1-6Manalpha1 branches in N-linked glycoproteins based on the specificity of N-acetylglucosaminyltransferase VI

Malignant transformation is often accompanied by an aberrant glycosylation profile of the cell surface-in particular, the production of GlcNAcbeta1-6Manalpha1 branches in N-linked glycoproteins. To identify the target glycoproteins, we show a method using recombinant chicken N-acetylglucosaminyltransferase VI (GnT VI) and radiolabeled uridine (5'-)diphosphate-GlcNAc. The assay exploits the fact that GnT VI has a strict requirement for the GlcNAcbeta1-6Manalpha1 structure for activity, when a pyridylaminated free N-glycan is used as the acceptor substrate. Human asialo-agalacto alpha1-acid glycoprotein (AGP), which is known to contain GlcNAcbeta1-6Manalpha1 branches in its N-linked glycan chains, was radiolabeled when reacted with GnT VI, whereas human asialo-agalacto transferrin and bovine fetuin, neither of which contains a GlcNAcbeta1-6Manalpha1 structure were not, thus corroborating the specificity of the assay. Several proteins from human serum after pretreatment with sialidase and beta-galactosidase could be detected using the assay. One was identified as AGP from its mobility on SDS-PAGE, demonstrating the potential of this assay even with crude materials. Furthermore, this method could detect a protein that was also positively stained with leukoagglutinating phytohemagglutinin (L(4)-PHA) using glycoproteins prepared from WiDr human colon cancer cells. This method should provide a useful complement to the current method, which relies on the specificity of L(4)-PHA.

Analysis of parameter variations in L-Q equations for river runoff processes from the viewpoint of spatial and temporal conditions

This study aims to find out variation characteristics of the parameters of 'a' and 'b' in L = a x Q(b), an empirical equation for run-off loading (L) and flow rate (Q), by evaluating the effects of flow conditions and regional properties of the watersheds on the values. We selected the Kamo River basin (155 km2) as a study field, and conducted various kinds of investigations, such as 80 day high frequency observations, continuous monitoring for more than 2 years, storm event surveys, and simultaneous surveys of 39 stations. Then, we obtained 7-170 data in each of 39 sampling stations. The main results obtained are as follows: (1) L-Q equation with a range of 'a' can express L-Q relation in most of the WQIs (water quality indices); (2) 'a' receives temporal (flow condition) effects more in SS, VSS and Al, while it receives regional effect more in inorganic carbon, TN, Ca and Fe; (3) both of flow change in storm events, and base flow levels affect the L-Q relation, and their effects can classify the WQIs into several groups; (4) the effects of regional properties were obviously observed in 'a', and quantitatively evaluated, especially for density of population.

Interaction between desialylated hepatitis B virus and asialoglycoprotein receptor on hepatocytes may be indispensable for viral binding and entry

The cellular receptor for hepatitis B virus (HBV) infection has not yet been identified. The purpose of this study was to address the possibility of participation by desialylated HBV and the asialoglycoprotein receptor (ASGP-R) exclusively expressed on liver parenchymal cells, in infection. Assays for viral binding and entry were performed by culturing a hepatoblastoma cell line, HepG2, and HBV particles derived from the HBV carrier in the presence or absence of neuraminidase (NA). Viral binding and entry were clearly enhanced in the presence of NA, and the enhancement of the binding could be blocked by asialo-fetuin and ethylenediamine-tetraacetic acid (EDTA). In addition, covalently closed circular (CCC)-DNA, as a marker of infectivity, was detected in the presence of NA, but not in its absence. The optimal concentration of NA raised infectivity more than 1000 times. We concluded that this method makes it feasible to evaluate the infectivity of HBV in vitro and that ASGP-R may be a specific HBV receptor once viral particles are desialylated.

Estimation of annual pollutant loadings in two small catchments and examination of their differences caused by regional properties

A series of runoff surveys was conducted for more than one year in two small catchments of the Kamo River basin (75.4 km2) and the Takano River basin (66.8 km2) in Kyoto, Japan, which adjoin each other, and may have the same precipitation pattern. The investigation consisted of a high-frequency periodic survey, a long-term regular survey and a storm event survey. The survey results were compared with the regional properties of the basins, and the following results were obtained. (1) Pollutant loadings were successfully estimated as two portions of base discharge and storm events discharge from the survey results. (2) Estimated annual loading of the sites was 2.9-4.5, 1.3-1.8, 17-27, 1.3-2.2, 0.076-0.97 t/km2/y, respectively for COD(Mn), DOC, SS, TN and TP. (3) 52-53% of the whole flow, which was caused by rainfall events, conveyed 81-87, 68-73, 92-95, 64-67, 76-81% of the whole loading, respectively for COD(Mn), DOC, SS, TN and TP. (4) Differences of regional properties in two basins cause different runoff patterns, but the differences in runoff patterns also depend on the rainfall patterns. In general, a more urbanized basin receives early and strong influence of precipitation on the storm event runoff.

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.

Core fucosylation regulates epidermal growth factor receptor-mediated intracellular signaling

alpha1,6-Fucosyltransferase (Fut8) catalyzes the transfer of a fucose residue to N-linked oligosaccharides on glycoproteins via an alpha1,6-linkage to form core fucosylation in mammals. We recently found that disruption of the Fut8 gene induces severe growth retardation and early postnatal death. To investigate the molecular mechanism involved, we have established embryonic fibroblasts of Fut8+/+ and Fut8-/-, derived from wild-type and Fut8-null mice, respectively. Interestingly, the epidermal growth factor (EGF)-induced phosphorylation levels of the EGF receptor (EGFR) were substantially blocked in Fut8-/- cells, compared with Fut8+/+ cells, while there are no significant changes in the total activities of tyrosine phosphatase for phosphorylated EGFR between two cells. The inhibition of EGFR phosphorylation was completely restored by re-introduction of the Fut8 gene to Fut8-/- cells. Consistent with this, EGFR-mediated JNK or ERK activation was significantly suppressed in Fut8-/- cells. Finally, we found that the core fucosylation of N-glycans is required for the binding of the EGF to its receptor, whereas no effect was observed for the expression levels of EGFR on the cell surface. Collectively, these results strongly suggest that core fucosylation is essential for EGF receptor-mediated biological functions.

Preparation and characterization of spherical polymer packings from polybutadiene for size-exclusion chromatography

Porous polymer spherical particles for column packings in nonaqueous size-exclusion chromatography (SEC) were prepared from 1,2-syndiotactic polybutadiene by suspension and evaporation method. The polymer microbeads obtained were crosslinked by radical reaction between 2-vinyl groups in polybutadiene with ultraviolet radiation, to render them insoluble. These microbeads have wider chromatographic separation width than polystyrene column packings. In addition, the polybutadiene microbeads did not show the excessive retention observed with commercial polystyrene columns for polycyclic aromatic compounds. Therefore, a close correlation between the elution volume and M, for polycyclic aromatic compounds was observed with polybutadiene microbeads columns.

The association between negative and dysexecutive syndromes in schizophrenia: a cross-cultural study

This paper examined the relationship between the ‘negative syndrome’ (NS) and the neuropsychological ‘dysexecutive syndrome’ (DES) in schizophrenia. The study also examined whether any relationship that exists between the NS and the DES holds equally for British and Japanese subjects. We compared 26 Japanese with 17 British schizophrenic patients, divided into ‘mild’ and ‘severe’ NS groups, on the basis of performance on neuropsychological tests, including the ‘Behavioural Assessment of Dysexecutive Syndrome’ (BADS). We found that patients with severe NS showed more everyday executive deficits than those with mild NS. The severity of NS was correlated with executive competence. The association between NS and the BADS performance was closer than that between NS and other conventional executive measures. These findings were not influenced by cultural differences between Japanese and British subjects, and, hence, suggested the existence of culture-neutral neurobehavioural processes.

Activated protein C attenuates coagulation-associated over-expression of fibrinolytic activity by suppressing the thrombin-dependent inactivation of PAI-1

Several activated coagulation factors have been reported to enhance fibrinolysis by neutralizing plasminogen activator inhibitor type 1 (PAI-1) activity. We evaluated the physiological relevance of this mechanism using the euglobulin clot lysis time (ECLT) assay in the presence and absence of Ca2+, which is controlled by PAI-1 and mimics physiological thrombolysis. We found that the ECLT (18.5 +/- 0.6 h) was shortened by Ca2+ (5 mm) (6.6 +/- 0.1 h). A significant difference was observed in thrombin generation by the presence of Ca2+ in the euglobulin fraction. Prothrombin was almost fully converted to thrombin within 15 min in the presence of Ca2+, whereas essentially no conversion was observed without Ca2+. The presence of activated protein C (aPC) suppressed thrombin generation, and attenuated the shortening of ECLT in a dose-dependent manner, an effect enhanced by phospholipid and protein S. In the absence of Ca2+, aPC did not prolong the ECLT. After addition of biotin-labeled recombinant PAI-1 to the euglobulin fraction, PAI-1 was cleaved to lower molecular weight forms only in the presence of Ca2+. This cleavage did not occur in the presence of aPC, suggesting that thrombin was the catalyst for PAI-1 cleavage. The cleavage and inactivation of PAI-1 by generated thrombin is proposed to be responsible for the shortening of ECLT by Ca2+ and for coagulation-associated over-expression of fibrinolysis. Under such conditions, aPC appeared to suppress thrombin generation and to normalize highly activated fibrinolysis.

A cold-adapted endo-arabinanase from Penicillium chrysogenum

Previously, three arabinan-degrading enzymes were isolated from Penicillium chrysogenum 31B. Here we describe another arabinan-degrading enzyme, termed Abnc, from the culture filtrate of the same organism. Analysis of the reaction products of debranched arabinan by high-performance anion-exchange chromatography (HPAEC) revealed that Abnc cleaved the substrate in an endo manner and that the final major product was arabinotriose. The molecular mass of Abnc was estimated to be 35 kDa by SDS-PAGE. Enzyme activity of Abnc was highest at pH 6.0 to 7.0. The enzyme was stable up to 30 degrees C and showed optimum activity at 30 to 40 degrees C. Compared with a mesophilic counterpart from Aspergillus niger, Abnc exhibited a lower thermal stability and optimum enzyme activity at lower temperatures. Production of Abnc in P. chrysogenum was found to be strongly induced by arabinose-containing polymers and required a longer culture time than did other arabinanase isozymes in this strain.

1,4-N-Acetylglucosaminyltransferase III down-regulates neurite outgrowth induced by costimulation of epidermal growth factor and integrins through the Ras/ERK signaling pathway in PC12 cells

A rat pheochromocytoma cell line (PC12), when transfected with beta1,4-N-acetylglucosaminyltransferase III (GnT-III), which catalyzes the formation of a bisecting GlcNAc structure in N-glycans, resulted in the suppression of neurite outgrowth induced by costimulation of epidermal growth factor (EGF) and integrins. The neurite outgrowth was restored by the overexpression of a constitutively activated mitogen- or extracellular signal-regulated kinase kinase-1 (MEK-1). Consistent with this, the EGF receptor (EGFR)-mediated ERK activation was blocked in GnT-III transfectants. Conversely, the overexpression of dominant negative MEK-1 or treatment with PD98059, a specific inhibitor of MEK-1, inhibited neurite outgrowth in controls transfected with mock. Furthermore GnT-III activity is required for these inhibitions, because the overexpression of a dominant negative GnT-III mutant (D321A) failed to reduce neurite outgrowth and EGFR-mediated ERK activation. Lectin blot analysis confirmed that EGFR from wild-type GnT-III transfectants had been modified by bisecting GlcNAc in its N-glycan structures. This modification led to a significant decrease in EGF binding and EGFR autophosphorylation. Collectively, the results constitute a comprehensive body of evidence to show clearly that the overexpression of GnT-III prevents neurite outgrowth induced by costimulation of EGF and integrins through the Ras/MAPK activation pathway and indicates that GnT-III may be an important regulator for cell differentiation in neural tissues.

Addition of 1-6 GlcNAc branching to the oligosaccharide attached to Asn 772 in the serine protease domain of matriptase plays a pivotal role in its stability and resistance against trypsin

beta1-6 GlcNAc branching, a product of N-acetylglucosaminyltransferase V (GnT-V), is a key structure that is associated with malignant transformations and cancer metastasis. Although a number of reports concerning tumor metastasis-related glycoproteins that contain beta1-6 GlcNAc branching have appeared, the precise function of beta1-6 GlcNAc branching on glycoproteins remains to be elucidated. We previously reported on the importance of beta1-6 GlcNAc branching on matriptase in terms of proteolytic degradation in tumor metastasis. We report here that matriptase purified from GnT-V transfectant (beta1-6 GlcNAc matriptase) binds strongly to L4-PHA, which preferentially recognizes beta1-6 GlcNAc branches of tri- or tetraantennary sugar chains, indicating that the isolated matriptase contains beta1-6 GlcNAc branching. The beta1-6 GlcNAc matriptase was resistant to autodegradation, as well as trypsin digestion, compared with matriptase purified from mock-transfected cells. Furthermore, N-glycosidase-F treatment of beta1-6 GlcNAc matriptase greatly reduced its resistance to degradation. An analysis of matriptase mutants that do not contain potential N-glycosylation sites clearly shows that the beta1-6 GlcNAc branching on N-glycans attached to Asn 772 in the serine protease domain plays a major role in trypsin resistance. This is the first example of a demonstration of a direct relationship between beta1-6 GlcNAc branching and a biological function at the protein level.

Caveolin-1 regulates the functional localization of N-acetylglucosaminyltransferase III within the golgi apparatus

In an investigation of the mechanism underlying the functional sublocalization of glycosyltransferases within the Golgi apparatus, caveolin-1 was identified as a possible cellular factor. Caveolin-1 appears to regulate the localization of N-acetylglucosaminyltransferase III (GnT-III) in the intra-Golgi subcompartment. Structural analyses of total cellular N-glycans indicated that the overexpression of GnT-III in human hepatoma cells, in which caveolin-1 is not expressed, failed to reduce branch formation, whereas expression of caveolin-1 led to a dramatic decrease in the extent of branching with no enhancement in GnT-III activity. Because the addition of a bisecting GlcNAc by GnT-III to the core beta-Man in N-glycans prevents the action of GnT-IV and GnT-V, both of which are involved in branch formation, this result suggests that caveolin-1 facilitates the prior action of GnT-III, relative to the other GnTs, on the nascent sugar chains in the Golgi apparatus and that GnT-III is redistributed in the earlier Golgi subcompartment by caveolin-1. Indeed, when caveolin-1 was expressed in human hepatoma cells, it was found to be co-localized with GnT-III, as evidenced by the fractionation of Triton X-100-insoluble cellular membranes by density gradient ultracentrifugation. Caveolin-1 may modify the biosynthetic pathway of sugar chains via the regulation of the intra-Golgi subcompartment localization of this key glycosyltransferase.

Rapid, specific and active site-catalyzed effect of tissue-plasminogen activator on hippocampus-dependent learning in mice

In the present study we trained tissue-plasminogen activator (tPA)-knockout (tPA -/-) and wild-type (tPA +/+) male mice in step-down inhibitory avoidance learning, a hippocampus-dependent task. tPA -/- displayed significantly shorter latencies to step down at 90 min, one, two and seven days after training indicating the learning deficit in these animals (P < 0.05 vs tPA +/+). The locomotor activity, the level of anxiety in an elevated-plus maze, as well as the pain threshold did not differ between the two strains of mice. The learning disability of tPA -/- was overcome by more intense training. The learning deficit was also partially restored by limited intrahippocampal delivery of tPA (infused for 2 h before training; P < 0.05 vs control), but not by the delivery of urokinase plasminogen activator, indicating the acute need for tPA in learning. The beneficial effect of tPA was abolished by co-infusion of its inhibitor tPA-STOP, indicating that the facilitatory effect of tPA on learning requires a proteolytic step. However, tPA activity in the hippocampus was not indispensable for effective memory retrieval in tPA-infused tPA -/- mice. Thus, rapid, specific and proteolytic action of tPA facilitates hippocampus-dependent learning, but not retrieval of previously acquired information.

An enzymatic method of analysis for GDP-L-fucose in biological samples, involving high-performance liquid chromatography

To investigate the biological significance of GDP-L-fucose, we established a unique method for the determination of GDP-L-fucose levels in microsomal fractions, using an HPLC assay of alpha 1-6-fucosyltransferase (alpha1-6-FucT), an enzyme that catalyzes the synthesis of core fucosylation in N-glycans. A microsomal protein and a large excess of fluorescence-labeled synthetic oligosaccharide (a substrate) were incubated with a large excess of alpha1-6-FucT. The fluorescent intensity of the fucosylated reaction product, which was analyzed by isocratic reverse phase HPLC, was proportional to the level of GDP-L-fucose in the microsomal fractions over the range 0.20-10 pmol. This assay is applicable to the determination of the GDP-L-fucose content in various cancer cell lines as well as rat liver and would be useful in developing a better understanding of the fucosylation potential of such cells and tissues.