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S Aono

Publications and source records attributed to S Aono.

At least 37 records · Page 2Linked to original sources
PubMed1999

p120(ctn) acts as an inhibitory regulator of cadherin function in colon carcinoma cells.

p120(ctn) binds to the cytoplasmic domain of cadherins but its role is poorly understood. Colo 205 cells grow as dispersed cells despite their normal expression of E-cadherin and catenins. However, in these cells we can induce typical E-cadherin-dependent aggregation by treatment with staurosporine or trypsin. These treatments concomitantly induce an electrophoretic mobility shift of p120(ctn) to a faster position. To investigate whether p120(ctn) plays a role in this cadherin reactivation process, we transfected Colo 205 cells with a series of p120(ctn) deletion constructs. Notably, expression of NH2-terminally deleted p120(ctn) induced aggregation. Similar effects were observed when these constructs were introduced into HT-29 cells. When a mutant N-cadherin lacking the p120(ctn)-binding site was introduced into Colo 205 cells, this molecule also induced cell aggregation, indicating that cadherins can function normally if they do not bind to p120(ctn). These findings suggest that in Colo 205 cells, a signaling mechanism exists to modify a biochemical state of p120(ctn) and the modified p120(ctn) blocks the cadherin system. The NH2 terminus-deleted p120(ctn) appears to compete with the endogenous p120(ctn) to abolish the adhesion-blocking action.

Alkaloids↗
PubMed1999

Two cases of inflammatory bowel disease with multiple myeloma.

A significant increase has been reported in reticuloendothelial neoplasms in patients with inflammatory bowel diseases. We present two rare cases of multiple myeloma in patients with inflammatory bowel diseases. One was in a 58-year-old woman with ulcerative colitis, and the other was in a 59-year old woman with Crohn's disease. In both patients, multiple myeloma occurred during long-term observation of inflammatory bowel disease and during the inactive stage of intestinal inflammation. The multiple myeloma appeared to have resulted from monoclonal gammopathy of undertermined significance in both patients, and was diagnosed by characteristic serum and bone marrow findings. Our findings suggested that multiple myeloma should be particularly considered in women of middle or advanced age with ulcerative colitis or Crohn's colitis and serum monoclonal gammopathy.

Female↗
PubMed1998

Solution structure of an artificial Fe8S8 ferredoxin: the D13C variant of Bacillus schlegelii Fe7S8 ferredoxin.

The solution structure of the D13C variant of the thermostable Fe7S8 ferredoxin from Bacillus schlegelii has been determined by 1H-NMR spectroscopy in its oxidized form. In a variable-temperature NMR study the D13C variant was as thermostable (up to 90 degrees C) as the wild-type protein (WT). Seventy-five out of 77 amino acid residues and 81% of all theoretically expected proton resonances in the D13C Fe8S8 protein have been assigned. Its structure was determined through torsion angle dynamics calculations with the program DYANA, using 935 meaningful NOEs (from a total of 1251), hydrogen bond constraints, and NMR-derived dihedral angle constraints for the cluster-ligating cysteines. Afterwards, restrained energy minimization and restrained molecular dynamics were applied to each conformer of the family. The final family of 20 structures has RMSD values from the mean structure of 0.055 nm for the backbone atoms and of 0.099 nm for all heavy atoms. The overall folding of the WT is maintained in the mutant, except for the immediate vicinity of the new cysteine, which becomes much more similar to native Fe8S8 proteins. The two residues at positions 11 and 12, which constitute an insertion with respect to all known Fe8S8 proteins, assume a conformation that does not prevent the preceding and following residues from folding like in native Fe8S8 proteins. Clear evidence for the existence of two conformations involving almost half of the amino acid residues was found. The two conformations are structurally indistinguishable. Temperature-dependent NMR experiments show that one of them is thermodynamically more stable than the other.

Amino Acid Sequence↗
PubMed1998

Redox-controlled ligand exchange of the heme in the CO-sensing transcriptional activator CooA.

The transcriptional activator CooA from Rhodospirillum rubrum contains a b-type heme that acts as a CO sensor in vivo. CooA is the first example of a transcriptional regulator containing a heme as a prosthetic group and of a hemeprotein in which CO plays a physiological role. In this study, we constructed an in vivo reporter system to measure the transcriptional activator activity of CooA and prepared some CooA mutants in which a mutation was introduced at Cys, His, Met, Lys, or Tyr. Only the mutations of Cys75 and His77 affected the electronic absorption spectra of the heme in CooA. The electronic absorption spectra, EPR spectra, and the transcriptional activator activity of the wild-type and mutant CooA proteins indicate that 1) the thiolate derived from Cys75 is the axial ligand in the ferric heme, but it is not coordinated to the CO-bound ferrous heme; 2) Cys75 is protonated or displaced in the ferrous heme; and 3) His77 is the proximal ligand in the CO-bound ferrous heme and probably also in the ferrous heme, but it is not coordinated to the ferric heme. NMR spectra reveal that the conformational change around the heme, which will trigger the activation of CooA by CO, takes place upon the binding of CO to the heme.

Bacterial Proteins↗
PubMed1998

Heme environmental structure of CooA is modulated by the target DNA binding. Evidence from resonance Raman spectroscopy and CO rebinding kinetics.

In order to investigate the gene activation mechanism triggered by the CO binding to CooA, a heme-containing transcriptional activator, the heme environmental structure and the dynamics of the CO rebinding and dissociation have been examined in the absence and presence of its target DNA. In the absence of DNA, the Fe-CO and C=O stretching Raman lines of the CO-bound CooA were observed at 487 and 1969 cm-1, respectively, suggesting that a neutral histidine is an axial ligand trans to CO. The frequency of nu(Fe-CO) implies an open conformation of the distal heme pocket, indicating that the ligand replaced by CO is located away from the bound CO. When the target DNA was added to CO-bound CooA, an appearance of a new nu(Fe-CO) line at 519 cm-1 and narrowing of the main line at 486 cm-1 were observed. Although the rate of the CO dissociation was insensitive to the additions of DNA, the CO rebinding was decelerated in the presence of the target DNA, but not in the presence of nonsense DNA. These observations demonstrate the structural alterations in the heme distal site in response to binding of the target DNA and support the activation mechanism proposed for CooA, which is triggered by the movement of the heme distal ligand to modify the conformation of the DNA binding domain.

Bacterial Proteins↗
PubMed1998

Solution structure of the oxidized Fe7S8 ferredoxin from the thermophilic bacterium Bacillus schlegelii by 1H NMR spectroscopy.

The solution structure of the paramagnetic seven-iron ferredoxin from Bacillus schlegelii in its oxidized form has been determined by 1H NMR. The protein, which contains 77 amino acids, is thermostable. Seventy-two residues and 79% of all theoretically expected proton resonances have been assigned. The structure has been determined through torsion angle dynamics calculations with the program DYANA, using 966 meaningful NOEs (from a total of 1305), hydrogen bond constraints, and NMR derived dihedral angle constraints for the cluster ligating cysteines, and by using crystallographic information to build up the two clusters. Afterwards, restrained energy minimization and restrained molecular dynamics were applied to each conformer of the family. The final family of 20 structures has RMSD values from the mean structure of 0.68 A for the backbone atoms and of 1.16 A for all heavy atoms. The contributions to the thermal stability of the B. schlegelii ferredoxin are discussed by comparing the present structure to that of the less stable Azotobacter vinelandii ferredoxin I which is the only other available structure of a bacterial seven-iron ferredoxin. It is proposed that the hydrophobic interactions and the hydrogen bond network linking the N-terminus and the C-terminus together and a high number of salt bridges contribute to the stability.

Amino Acid Sequence↗
PubMed1998

Occurrence of a N-terminal proteolytic fragment of neurocan, not a C-terminal half, in a perineuronal net in the adult rat cerebrum.

Neurocan is a nervous tissue-unique chondroitin sulfate proteoglycan (CSPG) whose expression and proteolytic cleavage are developmentally regulated. In the adult rat brain, neurocan is completely cleaved into some proteoglycan fragments including the C-terminal half known as neurocan-C and a N-terminal fragment with a 130 kDa core glycoprotein (neurocan-130). We describe here the differential distribution of these two neurocan-derived CSPGs in the adult rat cerebrum and the occurrence of neurocan-130 as a new member of a perineuronal net-constituting molecule. At the light microscopic level, neurocan-130 exhibited pericellular localization around a subset of neurons in addition to diffuse distribution in the neuropil. In contrast, neurocan-C was distributed only diffusely in the neuropil. Double staining with anti-neurocan-130 and anti-synaptophysin antibodies suggested that neurocan-130 was localized in the vicinity of the synapses, but not at the synapses. Immunoelectron microscopy showed that neurocan-130 was mainly localized in the cytoplasm of glial cell processes, the so-called glial perineuronal net, encompassing the cell bodies of certain neurons. The presence of neurocan-130 in a limited number of glial cells may reflect some functional heterogeneity of the glia.

Age Factors↗
PubMed1998

Cloning and chromosomal mapping of the human gene of neuroglycan C (NGC), a neural transmembrane chondroitin sulfate proteoglycan with an EGF module.

Neuroglycan C (NGC) is a 150 kDa transmembrane chondroitin sulfate proteoglycan with a 120 kDa core glycoprotein that was originally isolated from the developing rat brain. A rabbit antiserum, raised against a recombinant polypeptide representing a protein of the rat NGC core protein, recognized an NGC homolog in homogenates of brains of various vertebrates including humans. Because of the possible involvement of this proteoglycan in the etiology of a human neuronal disease, we cloned a complete coding sequence from a human brain cDNA library using a rat NGC cDNA as a probe. The predicted protein contains 539 amino acids and shows 86% homology with the rat counterpart. The domain structure characteristic of rat NGC was completely conserved in human NGC, which consisted of an N-terminal signal sequence, a chondroitin sulfate-attachment domain, an acidic amino acid cluster, an EGF-like domain, a transmembrane domain and a cytoplasmic tail. Northern blot analysis revealed that a single transcript of 2.4 kb was detectable in the brain, but not in other human tissues. By fluorescence in situ hybridization (FISH) analysis, the human NGC gene was assigned to the chromosomal 3p21.3 band, where the Sotos syndrome has been mapped. Involvement of the NGC gene in the etiology of the Sotos syndrome remains to be examined.

Amino Acid Sequence↗
PubMed1997

Single transduction in the transcriptional activator CooA containing a heme-based CO sensor: isolation of a dominant positive mutant which is active as the transcriptional activator even in the absence of CO.

We constructed an in vivo reporter system to measure the activity of CooA as the transcriptional activator and showed that the recombinant CooA was active as the transcriptional activator in the presence of CO even in E. coli cells. A dominant positive mutant of CooA, in which Met131 was replaced by Leu, was isolated by a random mutagenesis with this reporter system. The electronic absorption spectra of M131L mutant were identical to those of wild type CooA in oxidized (Fe3+), reduced (Fe2+), and CO-bound (CO-Fe2+) state, indicating that the coordination structure and environment of the heme were not changed by this mutation. Methionine at position 131 was the carboxyl-terminal end of the heme-binding domain of CooA, which would be adjacent to the hinge region connecting the heme-binding domain and the DNA-binding domain.

Bacterial Proteins↗
PubMed1997

The D13C variant of Bacillus schlegelii 7Fe ferredoxin is an 8Fe ferredoxin as revealed by 1H-NMR spectroscopy.

The N-terminal cluster binding motif Cys8XXXXXXXCys16....Cys49 of Bacillus schlegelii 7Fe ferredoxin, which provides the ligands to the [Fe3S4]+ cluster, was modified by the mutation Asp13 --> Cys. The mutant D13C is expressed in Escherichia coli as an 8Fe ferredoxin, with NMR properties similar to those of clostridial-type ferredoxins. The full assignment of the hyperfine shifted resonances indicates that Cys13 serves as ligand to the new fourth iron atom in the N-terminal cluster despite the atypical binding sequence CysXXXXCysXXCys....Cys. The C alpha-C beta-S-Fe dihedral angles of all cysteine ligands to the two [Fe4S4]2+ clusters of the D13C variant are similar to those observed in other 8Fe and 4Fe ferredoxins.

Aspartic Acid↗
PubMed1997

Persistent organochlorines in minke whale (Balaenoptera acutorostrata) and their prey species from the Antarctic and the North Pacific.

Persistent organochlorines such as polychlorinated biphenyls (PCBs), DDTs, chlordane compounds (CHLs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were determined in the blubber of minke whale and its diet collected from the Antarctic and the North Pacific Oceans. Residue levels of these compounds (except HCB) in minke whale from the Antarctic were apparently lower than those from the North Pacific. This is due to the lower levels of these pollutants in the southern hemisphere than in the northern hemisphere and the specific feeding habit of the minke whale from the Antarctic which feeds on lower trophic organisms, primarily euphausiids. The north-south difference for HCB residue levels was small, reflecting its dispersible nature through long-range atmospheric transport. Compositions of DDT and CHL compounds in minke whale from the Antarctic were similar to those from the North Pacific. However, the composition of HCH isomers was different between the Antarctic and the North Pacific as was observed in their diet, suggesting a larger or on-going usage of lindane in the southern hemisphere countries. In minke whale from the Antarctic, the elevated level of PCBs residues was noted during a period of 1984 to 1993, implying a continuous discharge of PCBs in the southern hemisphere. A similar discharge was also suggested in the North Pacific, while a decreasing contamination by DDTs was apparent.

Journal Article↗
PubMed1996

A novel heme protein that acts as a carbon monoxide-dependent transcriptional activator in Rhodospirillum rubrum.

The gene coding for a carbon monoxide-dependent transcriptional activator (cooA) in Rhodospirillum rubrum has been expressed in E. coli, and the recombinant CooA has been purified. CooA contains b-type heme which may act as a CO sensor in vivo. CO-bound CooA was formed when reduced CooA was reacted with CO, but not in the case of oxidized CooA. CooA is the first example of the heme protein acting as a DNA-binding transcriptional activator.

Amino Acid Sequence↗
PubMed1996

Crigler-Najjar syndrome type II is inherited both as a dominant and as a recessive trait.

Crigler-Najjar syndrome type II (CN-II) is caused by a severely reduced hepatic activity of bilirubin UDP-glucuronosyltransferase (UGT). Recently, by the analysis of the genetic background of CN-II patients, it has been clarified that the patients carry homozygous missense mutations or nonsense plus missense mutations on the gene for UGT, and CN-II was inherited as an autosomal recessive trait. We encountered a new case which had a nonsense mutation caused by a single nucleotide substitution on one allele. This indicates that CN-II is also inherited as a dominant trait as well as a recessive trait. Expression study in vitro strongly suggests that the disease in this case is caused by a dominant negative mutation by forming a heterologous subunit structure.

Amino Acid Sequence↗
PubMed1995

Analysis of genes for bilirubin UDP-glucuronosyltransferase in Gilbert's syndrome.

Gilbert's and Crigler-Najjar syndromes are characterised by unconjugated hyperbilirubinaemia due to complete and partial absence of bilirubin UDP-glucuronosyltransferase (UGT). Nucleotide sequences of the genes for bilirubin UGT were analysed in six patients with Gilbert's syndrome. All patients had a missense mutation caused by a single nucleotide substitution and the mutations were heterozygous. In addition, relatives of patients with Crigler-Najjar syndrome types I and II, and of those with Gilbert's syndrome were analysed. All ten relatives with mild hyperbilirubinaemia were heterozygotes with respect to each defective allele. These results suggest that Gilbert's syndrome is inherited as a dominant trait.

Adolescent↗
PubMed1995

Distribution of a brain-specific proteoglycan, neurocan, and the corresponding mRNA during the formation of barrels in the rat somatosensory cortex.

Neurocan is a developmentally regulated chondroitin sulphate proteoglycan in the rat brain. In the present study, spatiotemporal patterns of expression of neurocan and the corresponding mRNA were examined in the developing cortical barrel field of the rat brain by using a monoclonal antibody that was highly specific to neurocan and a riboprobe for a portion of the mRNA. Immunohistochemical analysis revealed that neurocan was distributed throughout the cerebral cortex during early postnatal development but was excluded from the centres of cortical barrels at the time of entry and arborization of thalamocortical axons. At this developmental stage, expression of neurocan mRNA was shown by in situ hybridization to be down-regulated in the barrel centres. When a row of whisker follicles was laser-cauterized on postnatal day 1, the pattern of expression of neurocan was disturbed in the row of barrels that corresponded to the lesioned whisker follicles in the contralateral somatosensory cortex. From these observations, it appears that neuronal stimuli through early thalamocortical fibres from the sensory periphery cause reduced expression of neurocan mRNA in neurocan-producing cells in the presumptive barrel centres. Our findings also suggest that the pattern of distribution of neurocan in early postnatal barrel fields may be due mainly to the down-regulation of expression of neurocan mRNA.

Animals↗
PubMed1995

Gilbert's syndrome is caused by a heterozygous missense mutation in the gene for bilirubin UDP-glucuronosyltransferase.

Gilbert's syndrome, which is characterized by chronic, non-hemolytic unconjugated hyperbilirubinemia, is caused by a reduction in the activity of hepatic bilirubin UDP-glucuronosyltransferase (UGT). Here, we report that all examined patients with this disease carried missense mutations in the gene for UGT and that the mutations were heterozygous. An expression study in COS cells in vitro, using the expression vector pcDL that carried the mutated gene for UGT from a patient, indicated that approximately 14% of the normal UGT activity was expressed. However, the UGT activity of the patient with Gilbert's syndrome was unexpectedly < 50% of the normal, perhaps as the result of the dominant negative nature of the mutation.

Adolescent↗