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Satoshi Kaneko

Publications and source records attributed to Satoshi Kaneko.

At least 19 recordsLinked to original sources
PubMed2005

Molecular and genetic studies imply Akt-mediated signaling promotes protein kinase CbetaII alternative splicing via phosphorylation of serine/arginine-rich splicing factor SRp40.

Insulin regulates alternative splicing of PKCbetaII mRNA by phosphorylation of SRp40 via a phosphatidylinositol 3-kinase pathway (Patel, N. A., Chalfant, C. E., Watson, J. E., Wyatt, J. R., Dean, N. M., Eichler, D. C., and Cooper, D. C. (2001) J. Biol. Chem. 276, 22648-22654). Transient transfection of constitutively active Akt2 kinase promotes PKCbetaII exon inclusion. Serine/arginine-rich (SR) RNA-binding proteins regulating the selection of alternatively spliced exons are potential substrates of Akt kinase because many of them contain RXRXX(S/T) motifs. Here we show that Akt2 kinase phosphorylated SRp40 in vivo and in vitro. Mutation of Ser86 on SRp40 blocked in vitro phosphorylation. In control Akt2(+/+) fibroblasts, insulin treatment increased the phosphorylation of endogenous SR proteins, but their phosphorylation state remained unaltered by insulin in fibroblasts from Akt2(-/-) mice. Levels of PKCbetaII protein were up-regulated by insulin in Akt2(+/+) cells; however, only very low levels of PKCbetaII were detected in Akt2(-/-) cells and did not change following insulin treatment. Endogenous PKCbetaI and -betaII mRNA levels in Akt2(+/+) and Akt2(-/-) gastrocnemius muscle tissues were compared using quantitative real time PCR. The results indicated a 54% decrease in the expression of PKCbetaII levels in Akt(-/-), whereas PKCbetaI levels remained unchanged in both samples. Further, transfection of Akt2(-/-) cells with a PKCbetaII splicing minigene revealed defective betaII exon inclusion. Co-transfection of the mutated SRp40 attenuated betaII exon inclusion. This study provides in vitro and in vivo evidence showing Akt2 kinase directly phosphorylated SRp40, thereby connecting the insulin, PI 3-kinase/Akt pathway with phosphorylation of a site on a nuclear splicing protein promoting exon inclusion. This model is upheld in Akt2-deficient mice with insulin resistance leading to diabetes mellitus.

Alternative Splicing↗
PubMed2005

AKT/PKB signaling mechanisms in cancer and chemoresistance.

During the past decade, Akt (also known as protein kinase B, PKB) has been extensively studied. It regulates a variety of cellular processes by mediating extracellular (mitogenic growth factor, insulin and stress) and intracellular (altered tyrosine receptor kinases, Ras and Src) signals. Activation of Akt by these signals is via its pleckstrin homology (PH) domain binding to products of phosphatidylinositol 3-kinase (PI3K). This process is negatively regulated by a dual phosphatase PTEN tumor suppressor. Today, more than 30 Akt substrates have been identified. These phosphorylation events mediate the effects of Akt on cell survival, growth, differentiation, angiogenesis, migration and metabolism. Further, PI3K/PTEN/Akt pathway is frequently altered in many human malignancies and overexpression of Akt induces malignant transformation and chemoresistance. Thus, the Akt pathway is a major target for anti-cancer drug development. This review focuses on Akt signaling mechanism in oncogenesis and chemoresistance, and ongoing translational efforts to therapeutically target Akt.

Animals↗
PubMed2004

Aurora-A abrogation of p53 DNA binding and transactivation activity by phosphorylation of serine 215.

The tumor suppressor p53 is important in the decision to either arrest cell cycle progression or induce apoptosis in response to a variety of stimuli. p53 posttranslational modifications and association with other proteins have been implicated in the regulation of its stability and transactivation activity. Here we show that p53 is phosphorylated by the mitotic kinase Aurora-A at serine 215. Unlike most identified phosphorylation sites of p53 that positively associate with p53 function (Brooks, C. L., and Gu, W. (2003) Curr. Opin. Cell Biol. 15, 164-171), the phosphorylation of p53 by Aurora-A at Ser-215 abrogates p53 DNA binding and transactivation activity. Downstream target genes of p53, such as p21Cip/WAF1 and PTEN, were inhibited by Aurora-A in a Ser-215 phosphorylation-dependent manner (i.e. phosphomimic p53-S215D lost and non-phosphorylatable p53-S215A retained normal p53 function). As a result, Aurora-A overrides the apoptosis and cell cycle arrest induced by cisplatin and gamma-irradiation, respectively. However, the effect of Aurora-A on p53 DNA binding and transactivation activity was not affected by phosphorylation of Ser-315, a recently identified Aurora-A phosphorylation site of p53 (Katayama, H., Sasai, K., Kawai, H., Yuan, Z. M., Bondaruk, J., Suzuki, F., Fujii, S., Arlinghaus, R. B., Czerniak, B. A., and Sen, S. (2004) Nat. Genet. 36, 55-62). Our data indicate that phosphorylation of p53 at Ser-215 by Aurora-A is a major mechanism to inactivate p53 and can provide a molecular insight for Aurora-A function.

Amino Acid Sequence↗
PubMed2004

Crystal structure of aspartic proteinase from Irpex lacteus in complex with inhibitor pepstatin.

The crystal structure of Irpex lacteus aspartic proteinase (ILAP) in complex with pepstatin (a six amino acid residue peptide-like inhibitor) was determined at 1.3A resolution. ILAP is a pepsin-like enzyme, widely distributed in nature, with high milk-clotting activity relative to proteolytic activity. The overall structure was in good topological agreement with pepsin and other aspartic proteases. The structure and interaction pattern around the catalytic site were conserved, in agreement with the other aspartic proteinase/inhibitor complex structures reported previously. The high-resolution data also supported the transition state model, as proposed previously for the catalytic mechanism of aspartic proteinase. Unlike the other aspartic proteinases, ILAP was found to require hydrophobic residues either in the P(1) or P(1') site, and also in the P(4) and/or P(3) site(s) for secondary interactions. The inhibitor complex structure also revealed the substrate binding mechanism of ILAP at the P(3) and P(4) site of the substrate, where the inserted loop built up the unique hydrophobic pocket at the P(4) site.

Amino Acid Sequence↗
PubMed2004

UDP-sugar pyrophosphorylase with broad substrate specificity toward various monosaccharide 1-phosphates from pea sprouts.

UDP-sugars, activated forms of monosaccharides, are synthesized through de novo and salvage pathways and serve as substrates for the synthesis of polysaccharides, glycolipids, and glycoproteins in higher plants. A UDP-sugar pyrophosphorylase, designated PsUSP, was purified about 1,200-fold from pea (Pisum sativum L.) sprouts by conventional chromatography. The apparent molecular mass of the purified PsUSP was 67,000 Da. The enzyme catalyzed the formation of UDP-Glc, UDP-Gal, UDP-glucuronic acid, UDP-l-arabinose, and UDP-xylose from respective monosaccharide 1-phosphates in the presence of UTP as a co-substrate, indicating that the enzyme has broad substrate specificity toward monosaccharide 1-phosphates. Maximum activity of the enzyme occurred at pH 6.5-7.5, and at 45 degrees C in the presence of 2 mm Mg(2+). The apparent K(m) values for Glc 1-phosphate and l-arabinose 1-phosphate were 0.34 and 0.96 mm, respectively. PsUSP cDNA was cloned by reverse transcriptase-PCR. PsUSP appears to encode a protein with a molecular mass of 66,040 Da (600 amino acids) and possesses a uridine-binding site, which has also been found in a human UDP-N-acetylhexosamine pyrophosphorylase. Phylogenetic analysis revealed that PsUSP can be categorized in a group together with homologues from Arabidopsis and rice, which is distinct from the UDP-Glc and UDP-N-acetylhexosamine pyrophosphorylase groups. Recombinant PsUSP expressed in Escherichia coli catalyzed the formation of UDP-sugars from monosaccharide 1-phosphates and UTP with efficiency similar to that of the native enzyme. These results indicate that the enzyme is a novel type of UDP-sugar pyrophosphorylase, which catalyzes the formation of various UDP-sugars at the end of salvage pathways in higher plants.

Amino Acid Sequence↗
PubMed2004

Rational affinity purification of native Streptomyces family 10 xylanase.

Xylanase SoXyn10A from Streptomyces olivaceoviridis E-86 comprises a family 10 catalytic module linked to a family 13 carbohydrate-binding module (SoCBM13). The SoCBM13 has a beta-trefoil structure, with binding sites in each subdomain (alpha, beta and gamma). Subdomain alpha, but not subdomains beta and gamma, binds tightly to lactose. It was, therefore, thought that immobilized lactose could be used for the affinity purification of SoXyn10A. Lactosyl-Sepharose was prepared and tested as an affinity matrix. SoXyn10A produced from the cloned xyn10A gene by Escherichia coli, and native SoXyn10A in culture supernatants from S. olivaceoviridis, were purified to homogeneity in a single step by affinity chromatography using this matrix. This simple purification of SoXyn10A makes the enzyme an attractive candidate for applications requiring xylanase. The CBM also has the potential for use as an affinity tag for the purification of other proteins.

Blotting, Western↗
PubMed2004

Structure and function of a family 10 beta-xylanase chimera of Streptomyces olivaceoviridis E-86 FXYN and Cellulomonas fimi Cex.

The catalytic domain of xylanases belonging to glycoside hydrolase family 10 (GH10) can be divided into 22 modules (M1 to M22; Sato, Y., Niimura, Y., Yura, K., and Go, M. (1999) Gene (Amst.) 238, 93-101). Inspection of the crystal structure of a GH10 xylanase from Streptomyces olivaceoviridis E-86 (SoXyn10A) revealed that the catalytic domain of GH10 xylanases can be dissected into two parts, an N-terminal larger region and C-terminal smaller region, by the substrate binding cleft, corresponding to the module border between M14 and M15. It has been suggested that the topology of the substrate binding clefts of GH10 xylanases are not conserved (Charnock, S. J., Spurway, T. D., Xie, H., Beylot, M. H., Virden, R., Warren, R. A. J., Hazlewood, G. P., and Gilbert, H. J. (1998) J. Biol. Chem. 273, 32187-32199). To facilitate a greater understanding of the structure-function relationship of the substrate binding cleft of GH10 xylanases, a chimeric xylanase between SoXyn10A and Xyn10A from Cellulomonas fimi (CfXyn10A) was constructed, and the topology of the hybrid substrate binding cleft established. At the three-dimensional level, SoXyn10A and CfXyn10A appear to possess 5 subsites, with the amino acid residues comprising subsites -3 to +1 being well conserved, although the +2 subsites are quite different. Biochemical analyses of the chimeric enzyme along with SoXyn10A and CfXyn10A indicated that differences in the structure of subsite +2 influence bond cleavage frequencies and the catalytic efficiency of xylooligosaccharide hydrolysis. The hybrid enzyme constructed in this study displays fascinating biochemistry, with an interesting combination of properties from the parent enzymes, resulting in a low production of xylose.

Catalytic Domain↗
PubMed2004

Trends in reported incidences of gastric cancer by tumour location, from 1975 to 1989 in Japan.

BACKGROUND: This study was performed to estimate the incidence of gastric cancer by tumour location and to clarify whether the relative and absolute rates of gastric cancer in Japan changed between 1975 and 1989. METHODS: The stomach was anatomically divided into the upper, middle, and lower thirds. Age- and sex-specific incidences by tumour location were estimated by multiplying the age- and sex-specific national incidences of gastric cancer by the corresponding proportions of tumour location. We studied 171 721 cases of gastric cancer from the Gastric Cancer Registry of Japan. RESULTS: Over 15 years, the proportion of tumours in the upper third of the stomach increased in men but did not change much in women. The proportion of tumours in the middle third of the stomach increased among both men and women while the proportion of tumours in the lower third of the stomach decreased among both men and women. The incidence of tumours in the upper third of the stomach showed an increasing trend among elderly men and women but not among young ones. The incidence of tumours in the lower third of the stomach decreased significantly among men and women of most age groups. CONCLUSIONS: The present study added evidence of disparate trends in the incidence of gastric cancer by tumour location. The separate epidemiological features may indicate different aetiologies as well as changes in the degree of influence of these aetiologies.

Adenocarcinoma↗
PubMed2004

Molecular cloning and expression in Escherichia coli of a Trichoderma viride endo-beta-(1-->6)-galactanase gene.

The nucleotide sequence depicted in Figure 1 has been submitted to the DDBJ nucleotide sequence database under the accession no. AB104898. A gene encoding endo-beta-(1-->6)-galactanase from Trichoderma viride was cloned by reverse transcriptase-PCR and expressed in Escherichia coli. The gene contained an open reading frame consisting of 1437 bp (479 amino acids). The deduced amino acid sequence of the protein showed little similarity with other known glycoside hydrolases. A signal sequence (20 amino acids) was found at the N-terminal region of the protein and the molecular mass of the mature form was calculated to be 50.488 kDa. The gene product expressed in E. coli as a recombinant protein fused with thioredoxin and His(6) tags had almost the same substrate specificity and mode of action as native enzyme purified from a commercial cellulase preparation of T. viride, i.e. recombinant enzyme endo-hydrolysed beta-(1-->6)-galacto-oligomers with a DP (degree of polymerization) higher than 3, and it could also hydrolyse alpha-L-arabinofuranosidase-treated arabinogalactan protein from radish. It produced beta-(1-->6)-galacto-oligomers ranging from DP 2 to at least 8 at the initial hydrolysis stage and galactose and beta-(1-->6)-galactobiose as the major products at the final reaction stage. These results indicate that the cloned gene encodes an endo-beta-(1-->6)-galactanase. As far as we know, this is the first time an endo-beta-(1-->6)-galactanase has been cloned.

Amino Acid Sequence↗
PubMed2004

Module shuffling.

Explore the source record for details and available documents.

Amino Acid Sequence↗
PubMed2004

Catalytic activity of tripeptidase from Lactococcus lactis to which amino acid substitution was introduced according to natural mutation.

Four mutations observed between tripeptidases from Lactococcus lactis subsp. lactis and subsp. cremoris were introduced one by one to the corresponding points in wild-type tripeptidase from L. lactis subsp. lactis. The k(cat) values of four resultant mutants were analyzed and discussed in stereographical terms. Change in catalytic activity appeared to be related to the sequential and steric location of mutation point within the enzyme protein, even though no drastic change was observed with one point mutation.

Amino Acid Sequence↗
PubMed2004

[Analysis of facial lesions on adult type atopic dermatitis with anti-fungus drug (terbinafine hydrochloride) -- analysis of serum anti-Malassezia IgE antibody titers and histamine release test].

Malassezia furfur has been described as an aggravating factor in facial lesions of atopic dermatitis, and oral antifungal agents have been reported to be effective against these lesions. We used terbinafine hydrochloride to treat 15 patients with adult-type atopic dermatitis and evaluated its efficacy by measuring the improvement in facial skin manifestations, serum IgE values, and serum anti-Malassezia IgE antibody titers. A histamine release test (HRT) for Malassezia. was also performed in 6 of the 15 patients. The facial skin manifestations improved in 8 (53.3%) of the 15 patients, and there were significant simultaneous decreases in their serum IgE values. The serum anti-Malassezia IgE antibody titer decreased significantly in all 15 patients. However, no significant correlation was observed between the HRT and the facial skin manifestations. We concluded that oral terbinafine hydrochloride is effective against the facial lesions of atopic dermatitis patients and this is possibly caused by decrease of Malassezia antigen in the facial lesions.

Adult↗
PubMed2003

Crystal structures of decorated xylooligosaccharides bound to a family 10 xylanase from Streptomyces olivaceoviridis E-86.

The family 10 xylanase from Streptomyces olivaceoviridis E-86 (SoXyn10A) consists of a GH10 catalytic domain, which is joined by a Gly/Pro-rich linker to a family 13 carbohydrate-binding module (CBM13) that interacts with xylan. To understand how GH10 xylanases and CBM13 recognize decorated xylans, the crystal structure of SoXyn10A was determined in complex with alpha-l-arabinofuranosyl- and 4-O-methyl-alpha-d-glucuronosyl-xylooligosaccharides. The bound sugars were observed in the subsites of the catalytic cleft and also in subdomains alpha and gamma of CBM13. The data reveal that the binding mode of the oligosaccharides in the active site of the catalytic domain is entirely consistent with the substrate specificity and, in conjunction with the accompanying paper, demonstrate that the accommodation of the side chains in decorated xylans is conserved in GH10 xylanases of SoXyn10A against arabinoglucuronoxylan. CBM13 was shown to bind xylose or xylooligosaccharides reversibly by using nonsymmetric sugars as the ligands. The independent multiple sites in CBM13 may increase the probability of substrate binding.

Binding Sites↗
PubMed2003

Crystallization and preliminary X-ray crystallographic studies of alpha-galactosidase I from Mortierella vinacea.

alpha-Galactosidases catalyze the hydrolysis of a galactosyl residue from galactooligosaccharides and galactopolysaccharides. alpha-Galactosidase I from Mortierella vinacea was crystallized in two crystal forms using the hanging-drop vapour-diffusion method. Type 1 crystals belonged to space group I422, with unit-cell parameters a = b = 142.4, c = 131.5 A, and diffracted to beyond 2.1 A resolution, while type 2 crystals belonged to space group P4, with unit-cell parameters a = b = 100.9, c = 102.7 A, and diffracted to beyond 1.6 A resolution. This enzyme crystallized as a glycoprotein tetramer and the tetrameric structure was located around the crystallographic fourfold axis.

Bacterial Proteins↗
PubMed2003

Akt phosphorylation and stabilization of X-linked inhibitor of apoptosis protein (XIAP).

Akt negatively regulates apoptotic pathways at a premitochondrial level through phosphorylation and modulation of proteins such as Bad, Forkhead proteins, and GSK-3beta. Akt has also been shown to protect cell death at a post-mitochondrial level, although its downstream targets have not been well documented. Here, we demonstrate that Akt, including AKT1 and AKT2, interacts with and phosphorylates X-linked inhibitor of apoptosis protein (XIAP) at residue serine-87 in vitro and in vivo. Phosphorylation of XIAP by Akt protects XIAP from ubiquitination and degradation in response to cisplatin. Moreover, autoubiquitination of XIAP is also inhibited by Akt. Consistent with this, an XIAP mutant introduced into cells which mimics the Akt-phosphorylated form (i.e. XIAP-S87D) displays reduced ubiquitination and degradation as compared with wild type XIAP. The greater stability of XIAP-S87D in cells translated to increased cell survival after cisplatin treatment. Conversely, a mutant that could not be phosphorylated by Akt (XIAP-S87A) was more rapidly degraded and showed increased cisplatin-induced apoptosis. Furthermore, suppression of XIAP by either siRNA or adenovirus of antisense of XIAP induced programmed cell death and inhibited Akt-stimulated cell survival in ovarian cancer cells. These data identify XIAP as a new downstream target of Akt and a potentially important mediator of the effect of Akt on cell survival.

Animals↗
PubMed2003

Prospective study of screening for stomach cancer in Japan.

Although screening for stomach cancer is a widespread community service in Japan, the benefits of the screening program remain unclear. Our study investigated prospectively the relation between participation in stomach-cancer screening during the past 12 months and subsequent deaths. Data was derived from the Japan Collaborative Cohort Study, in which 480 stomach-cancer deaths were identified during an 8-year follow-up period. Cox proportional hazard regression was used to estimate the relative risk of death from stomach cancer and that from other causes while adjusting for potential confounding factors. In men, screening participation was associated significantly with a reduced risk of death from stomach cancer (relative risk [RR] = 0.54; 95% confidence interval [CI] = 0.41-0.70). The extent of the risk reduction was greater than potential health selection (for deaths other than stomach, RR = 0.71). The adjustment for potential confounding variables, however, attenuated the difference in risk of death (stomach cancer, RR = 0.65; other causes, RR = 0.71). In women, the magnitude of the association between screening participation and death from stomach cancer (RR = 0.74; 95% CI = 0.52-1.07) was equal to that for deaths from non-stomach cancers (RR = 0.74). Subgroup analysis showed that women with a parental history of stomach cancer had a reduced risk of death from stomach cancer associated with screening (RR = 0.32; 95% CI = 0.12-0.87). The present results underline the potential for selection bias in observational studies, and thus it remains an open question whether screening for stomach cancer is effective.

Adult↗
PubMed2003

Crystal structure of rice alpha-galactosidase complexed with D-galactose.

alpha-Galactosidases catalyze the hydrolysis of alpha-1,6-linked galactosyl residues from galacto-oligosaccharides and polymeric galacto-(gluco)mannans. The crystal structure of rice alpha-galactosidase has been determined at 1.5A resolution using the multiple isomorphous replacement method. The structure consisted of a catalytic domain and a C-terminal domain and was essentially the same as that of alpha-N-acetylgalactosaminidase, which is the same member of glycosyl hydrolase family 27. The catalytic domain had a (beta/alpha)8-barrel structure, and the C-terminal domain was made up of eight beta-strands containing a Greek key motif. The structure was solved as a complex with d-galactose, providing a mode of substrate binding in detail. The d-galactose molecule was found bound in the active site pocket on the C-terminal side of the central beta-barrel of the catalytic domain. The d-galactose molecule consisted of a mixture of two anomers present in a ratio equal to their natural abundance. Structural comparisons of rice alpha-galactosidase with chicken alpha-N-acetylgalactosaminidase provided further understanding of the substrate recognition mechanism in these enzymes.

Amino Acid Sequence↗