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S Koide

Publications and source records attributed to S Koide.

At least 19 recordsLinked to original sources
PubMed2001

Comparison of remnant-like lipoprotein particles in postmenopausal women with and without coronary artery disease and in men with coronary artery disease.

It is known that hypertriglyceridemia is a risk factor of coronary artery disease (CAD) in postmenopausal women. This study prospectively examined whether remnant lipoprotein, an atherogenic triglyceride-rich lipoprotein, may have a significant risk and prognostic values in postmenopausal women with angiographically verified CAD. Remnant-like lipoprotein particles cholesterol (RLP cholesterol) levels in fasting serum were measured in 134 consecutive postmenopausal women with (n = 56) or without (n = 78) CAD by an immunoseparation method. The women with CAD were followed for < or =24 months until occurrence of the following clinical coronary events: readmission or coronary revascularization due to recurrent or refractory angina pectoris, nonfatal myocardial infarction, and cardiac death. Multivariate logistic regression analysis showed that high RLP cholesterol levels (>5.7 mg/dl cholesterol; 90th percentile of the distribution of RLP cholesterol levels in controls) were a significant risk factor for the presence of CAD independent of low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, and other traditional risk factors. Kaplan-Meier analysis demonstrated that women with CAD and higher RLP cholesterol levels had a significantly higher probability of developing coronary events (p <0.001). In multivariate Cox hazard analysis, high RLP cholesterol levels as well as diabetes and hypercholesterolemia were a significant predictor of future coronary events independent of other risk factors in women with CAD (odds ratio 9.7, 95% confidence intervals 1.3 to 20.3, p = 0.02). In conclusion, increased levels of RLP cholesterol are a significant and independent risk factor of CAD and predict future coronary events in postmenopausal women with CAD.

Aged↗
PubMed2001

Proprotein convertase PACE4 is down-regulated by the basic helix-loop-helix transcription factor hASH-1 and MASH-1.

PACE4 is a mammalian subtilisin-like proprotein convertase that activates transforming growth factor (TGF)-beta-related proteins such as bone morphogenetic protein 2 (BMP2), BMP4 and Nodal and exhibits a dynamic expression pattern during embryogenesis. We recently determined that the 1 kb 5'-upstream region of the PACE4 gene contains 12 E-box (E1-E12) elements and that an E-box cluster (E4-E9) acts as a negative regulator [Tsuji, Yoshida, Hasegawa, Bando, Yoshida, Koide, Mori and Matsuda (1999) J. Biochem. (Tokyo) 126, 494-502]. It is known that the mammalian achaete-scute homologue 1 (MASH-1) binds specifically to an E-box (CACCTG) sequence in collaboration with E47, a ubiquitously expressed basic helix-loop-helix (bHLH) factor. To identify the roles of the bHLH factor and E-box elements in regulating PACE4 gene expression in neural development, we analysed the effects of human achaete-scute homologue 1 (hASH-1) on PACE4 gene expression with various neuroblastoma cell lines. The expressions of PACE4 and hASH-1 are correlated inversely in these cell lines. The overexpression of hASH-1 or MASH-1 causes a marked decrease in endogenous PACE4 gene expression but has no effect on the expression of other subtilisin-like proprotein convertases such as furin, PC5/6 and PC7/8. In contrast, other neural bHLH factors (MATH-1, MATH-2, neurogenin 1, neurogenin 2, neurogenin 3 and E47) did not affect PACE4 gene expression. Furthermore, an E-box cluster was a negative regulatory element for the promoter activity in NBL-S cells expressing hASH-1 at high level as determined by a luciferase assay. Binding of hASH-1 to the E-box cluster was confirmed by gel mobility-shift assay. In the present study we identified the PACE4 gene as one of the targets of hASH-1, which is a key factor in the initiation of neural differentiation. These results suggest that the alteration of PACE4 gene expression by hASH-1 causes rapid changes in the biological activities of TGF-beta-related proteins via post-translational modification of these proteins.

Basic Helix-Loop-Helix Proteins↗
PubMed2001

Stabilization of a fibronectin type III domain by the removal of unfavorable electrostatic interactions on the protein surface.

It is generally considered that electrostatic interactions on the protein surface, such as ion pairs, contribute little to protein stability, although they may play important roles in conformational specificity. We found that the tenth fibronectin type III domain of human fibronectin (FNfn10) is more stable at acidic pH than neutral pH, with an apparent midpoint of transition near pH 4. Determination of pK(a)'s for all the side chain carboxyl groups of Asp and Glu residues revealed that Asp 23 and Glu 9 have an upshifted pK(a). These residues and Asp 7 form a negatively charged patch on the surface of FNfn10, with Asp 7 centrally located between Asp 23 and Glu 9, suggesting repulsive electrostatic interactions among these residues at neutral pH. Mutant proteins, D7N and D7K, in which Asp 7 was replaced with Asn and Lys, respectively, exhibited a modest but significant increase in stability at neutral pH, compared to the wild type, and they no longer showed pH dependence of stability. The pK(a)'s of Asp 23 and Glu 9 in these mutant proteins shifted closer to their respective unperturbed values, indicating that the unfavorable electrostatic interactions have been reduced in the mutant proteins. Interestingly, the wild-type and mutant proteins were all stabilized to a similar degree by the addition of 1 M sodium chloride at both neutral and acidic pH, suggesting that the repulsive interactions between the carboxyl groups cannot be effectively shielded by 1 M sodium chloride. These results indicate that repulsive interactions between like charges on the protein surface can destabilize a protein, and protein stability can be significantly improved by relieving these interactions.

Amino Acid Sequence↗
PubMed2001

Formation of the single-layer beta-sheet of Borrelia burgdorferi OspA in the absence of the C-terminal capping globular domain.

Borrelia outer surface protein A (OspA) contains a unique single-layer beta-sheet that connects N and C-terminal globular domains. This single-layer beta-sheet segment (beta-strands 8-10) is highly stable in solution, although it is exposed to the solvent on both faces of the sheet and thus it does not contain a hydrophobic core. Here, we tested whether interactions with the C-terminal domain are essential for the formation of the single-layer beta-sheet. We characterized the solution structure, dynamics and stability of an OspA fragment corresponding to beta-strands 1-12 (termed OspA[27-163]), which lacks a majority of the C-terminal globular domain. Analyses of NMR chemical shifts and backbone nuclear Overhauser effect (NOE) connectivities showed that OspA[27-163] is folded except the 12th and final beta-strand. (1)H-(15)N heteronuclear NOE measurements and amide H-(2)H exchange revealed that the single-layer beta-sheet in this fragment is more flexible than the corresponding region in full-length OspA. Thermal-denaturation experiments using differential scanning calorimetry and NMR spectroscopy revealed that the N-terminal globular domain in the fragment has a conformational stability similar to that of the same region in the full-length protein, and that the single-layer beta-sheet region also has a modest thermal stability. These results demonstrate that the unique single-layer beta-sheet retains its conformation in the absence of its interactions with the C-terminal domain. This fragment is significantly smaller than the full-length OspA, and thus it is expected to facilitate studies of the folding mechanism of this unusual beta-sheet structure.

Amino Acid Sequence↗
PubMed2001

Crystal structure of outer surface protein C (OspC) from the Lyme disease spirochete, Borrelia burgdorferi.

Outer surface protein C (OspC) is a major antigen on the surface of the Lyme disease spirochete, Borrelia burgdorferi, when it is being transmitted to humans. Crystal structures of OspC have been determined for strains HB19 and B31 to 1.8 and 2.5 A resolution, respectively. The three-dimensional structure is predominantly helical. This is in contrast to the structure of OspA, a major surface protein mainly present when spirochetes are residing in the midgut of unfed ticks, which is mostly beta-sheet. The surface of OspC that would project away from the spirochete's membrane has a region of strong negative electrostatic potential which may be involved in binding to positively charged host ligands. This feature is present only on OspCs from strains known to cause invasive human disease.

Amino Acid Sequence↗
PubMed2001

Magnetohydrodynamic production of relativistic jets.

A number of astronomical systems have been discovered that generate collimated flows of plasma with velocities close to the speed of light. In all cases, the central object is probably a neutron star or black hole and is either accreting material from other stars or is in the initial violent stages of formation. Supercomputer simulations of the production of relativistic jets have been based on a magnetohydrodynamic model, in which differential rotation in the system creates a magnetic coil that simultaneously expels and pinches some of the infalling material. The model may explain the basic features of observed jets, including their speed and amount of collimation, and some of the details in the behavior and statistics of different jet-producing sources.

Journal Article↗
PubMed2001

Partial left ventriculectomy. The First Japanese Registry Report 1999.

OBJECTIVE: Partial left ventriculectomy has been performed without standardized inclusion/exclusion criteria. A registry has been established to accumulate experience with this procedure to identify indications, risks and benefits. METHODS: In response to a mailed inquiry, 90 cases were voluntarily registered from 28 Japanese institutions. RESULTS: Males (n = 67, 74.4%) predominated, and 29 (32.2%) patients were over 60 years old. The underlying cardiac pathologies included dilated cardiomyopathy (n = 75, 83.3%), valvular disease (n = 8, 8.9%), the dilated phase of hypertrophic cardiomyopathy (n = 4, 4.5%), and others (n = 3, 3.3%). Gender, age, etiology, papillary muscle excision and absent transplant indication did not significantly affect survival. Poorer preoperative condition, reduced contraction and decompensation necessitating emergency operation were each associated with a significantly higher risk. Hospitals performing less than 5 cases had poorer results than more experienced institutions (p = .0019), which showed a tendency towards improved survival in the second half of their experience (p = .096). Hospital mortality (n = 29, 32.6%) and late death (n = 10, 11.2%) were mainly from ventricular failure with few sudden deaths over a period of 63.6 patient years follow-up. Late mortality was equally distributed in the first year and leveled off with significantly improved cardiac functional class in survivors. CONCLUSION: Partial left ventriculectomy was associated with better survival in less symptomatic patients with better contractile reserve undergoing an elective operation preserving the papillary muscles. Avoidance of identified risk factors may allow better patient selection and improved survival in the current environment where rescue transplantation is not readily available. Long-term follow-up is warranted with more registry data.

Aged↗
PubMed2001

Preventing estrogen receptor action with dimer-interface peptides.

The human estrogen receptor-alpha (hER) is a ligand-activated transcription factor that functions as a homodimer. We sought to further understand the molecular processes involved in dimerization, and to develop a reagent that may function as an antiestrogen independent of the ligand binding site. To this end, we designed a 16-residue 'dimer-interface' oligopeptide derived from the helical region of the hER which is directly involved in dimerization. This peptide, termed the I-box peptide, has a high helical propensity in aqueous solution. The I-box peptide blocks hER action by causing aggregation and precipitation of both the ligand-bound and apo-hER. This effect is dependent on the helical nature of the peptide. A single Ile to Pro mutation in the helical region of the I-box peptide significantly reduces the helical content and abolishes the precipitation activity. Furthermore, the peptide activity appears to be specific for the hER. The I-box peptide does not significantly affect other proteins or steroid receptors tested. A homologous peptide derived from the nuclear receptor RXRalpha dimer interface, and a LXXLL-containing peptide from the coactivator TIF2 have no detectable in vitro effect on hER function or solubility. Our data suggest that rationally designed molecules capable of affecting steroid receptor quaternary structures may be potential avenues for the development of specific inhibitors of this class of proteins.

Amino Acid Sequence↗
PubMed2001

An improved method for distinguishing between anisotropic tumbling and chemical exchange in analysis of 15N relaxation parameters.

Although an accurate description of global tumbling of a protein is essential for correct analysis of internal motions. proper distinction between the effects of anisotropic rotational diffusion and conformational exchange has remained a challenge. We present a novel two-part filtering procedure designed specifically to distinguish between the effects of anisotropy and conformational exchange. The efficacy of this method is assessed using synthetic data sets. The method is then applied to two proteins of dramatically different size and shape, OspA and SH3. The large size and extreme anisotropy of OspA provide a challenging case, where conformational exchange is a small perturbation of the effects of anisotropy on transverse relaxation rates. Conversely, in the chicken c-Src SH3 domain, with its small size and nearly spherical shape, anisotropy is a small perturbation of the effects of conformational exchange on transverse relaxation rates. Accurate extraction of the global tumbling parameters for each protein allows optimal characterization of conformational exchange processes, as well as ps-ns time scale motions.

Animals↗
PubMed2001

FDG accumulation in aortic walls.

A 65-year-old woman with no symptoms underwent whole-body F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) for cancer screening. FDG accumulation was detected incidentally in her arterial walls, including the aortic wall. She had no history of inflammatory or cardiovascular disease. Although accumulation of FDG is well recognized in the aortic wall when vasculitis is present, this patient showed no symptoms of active vasculitis during the 22-month follow-up period after the PET study. The aortic wall might be a site where FDG accumulates physiologically in elderly persons.

Aged↗
PubMed2001

The roles of turn formation and cross-strand interactions in fibrillization of peptides derived from the OspA single-layer beta-sheet.

We previously demonstrated that a beta-hairpin peptide, termed BH(9-10), derived from a single-layer beta-sheet of Borrelia OspA protein, formed a native-like beta-turn in trifluoroethanol (TFE) solution, and it assembled into amyloid-like fibrils at higher TFE concentrations. This peptide is highly charged, and fibrillization of such a hydrophilic peptide is quite unusual. In this study, we designed a circularly permutated peptide of BH(9-10), termed BH(10-9). When folded into their respective beta-hairpin structures found in OspA, these peptides would have identical cross-strand interactions but different turns connecting the strands. NMR study revealed that BH(10-9) had little propensity to form a turn structure both in aqueous and TFE solutions. At higher TFE concentration, BH(10-9) precipitated with a concomitant alpha-to-beta conformational conversion, in a similar manner to the BH(9-10) fibrillization. However, the BH(10-9) precipitates were nonfibrillar aggregation. The precipitation kinetics of BH(10-9) was exponential, consistent with a first-order molecular assembly reaction, while the fibrillization of BH(9-10) showed sigmoidal kinetics, indicative of a two-step reaction consisting of nucleation and molecular assembly. The correlation between native-like turn formation and fibrillization of our peptide system strongly suggests that BH(9-10) adopts a native-like beta-hairpin conformation in the fibrils. Remarkably, seeding with the preformed BH(10-9) precipitates changed the two-step BH(9-10) fibrillization to a one-step molecular assembly reaction, and disrupted the BH(9-10) fibril structure, indicating interactions between the BH(10-9) aggregates and the BH(9-10) peptide. Our results suggest that, in these peptides, cross-strand interactions are the driving force for molecular assembly, and turn formation limits modes of peptide assembly.

Antigens, Surface↗
PubMed2001

An inferior mesenteric-caval shunt via the internal iliac vein with portosystemic encephalopathy.

We report here a case of an unusual extrahepatic portosystemic venous shunt in a 37-year-old woman without liver cirrhosis or portal hypertension, who developed portal systemic encephalopathy. Angiography demonstrated an inferior mesenteric-caval shunt characterized by the presence of direct communication of the inferior mesenteric vein with the left internal iliac vein. After the treatment with percutaneous transcatheter embolization of the shunt via a femoral vein approach using coils, she had no episode of portal systemic encephalopathy.

Adult↗
PubMed2000

Structural identification of a key protective B-cell epitope in Lyme disease antigen OspA.

Outer surface protein A (OspA) is a major lipoprotein of the Borrelia burgdorferi spirochete, the causative agent of Lyme disease. Vaccination with OspA generates an immune response that can prevent bacterial transmission to a mammalian host during the attachment of an infected tick. However, the protective capacity of immune sera cannot be predicted by measuring total anti-OspA antibody. The murine monoclonal antibody LA-2 defines an important protective B-cell epitope of OspA against which protective sera have strong levels of reactivity. We have now mapped the LA-2 epitope of OspA using both NMR chemical-shift perturbation measurements in solution and X-ray crystal structure determination. LA-2 recognizes the three surface-exposed loops of the C-terminal domain of OspA that are on the tip of the elongated molecule most distant from the lipid-modified N terminus. The structure suggests that the natural variation at OspA sequence position 208 in the first loop is a major limiting factor for antibody cross-reactivity between different Lyme disease-causing Borrelia strains. The unusual Fab-dominated lattice of the crystal also permits a rare view of antigen flexibility within an antigen:antibody complex. These results provide a rationale for improvements in OspA-based vaccines and suggest possible designs for more direct tests of antibody protective levels in vaccinated individuals.

Amino Acid Sequence↗
PubMed2000

Solution conformation and amyloid-like fibril formation of a polar peptide derived from a beta-hairpin in the OspA single-layer beta-sheet.

A 23-residue peptide termed BH(9-10) was designed based on a beta-hairpin segment of the single-layer beta-sheet region of Borrelia OspA protein. The peptide contains a large number of charged amino acid residues, and it does not follow the amphipathic pattern that is commonly found in natural beta-sheets. In aqueous solution, the peptide was highly soluble and flexible, with a propensity to form a non-native beta-turn. Trifluoroethanol (TFE) stabilized a native-like beta-turn in BH(9-10). TFE also decreased the level of solubility of the peptide, resulting in peptide precipitation. The precipitation process accompanied a conformational conversion to a beta-sheet structure, as judged with circular dichroism spectroscopy. The precipitate was found to be fibrils similar to those associated with human amyloid diseases. The fibrillization kinetics depended on peptide and TFE concentrations, and had a nucleation step followed by an assembly step. The fibrillization was reversible, and the dissociation reaction involved two phases. TFE appears to induce the fibrils by stabilizing a beta-sheet conformation of the peptide that optimally satisfies hydrogen bonding and electrostatic complementarity. This TFE-induced fibrillization is quite unusual, because most amyloidogenic peptides form fibrils in aqueous solution and TFE disrupts these fibrils. Nevertheless, the BH(9-10) fibrils have similar structure to other fibrils, supporting the emerging idea that polypeptides possess an intrinsic ability to form amyloid-like fibrils. The high level of solubility of BH(9-10), the ability to precisely control fibril formation and dissociation, and the high-resolution structure of the same sequence in the beta-hairpin conformation in the OspA protein provide a tractable experimental system for studying the fibril formation mechanism.

Amyloid↗
PubMed2000

Design of single-layer beta-sheets without a hydrophobic core.

The hydrophobic effect is the main thermodynamic driving force in the folding of water-soluble proteins. Exclusion of nonpolar moieties from aqueous solvent results in the formation of a hydrophobic core in a protein, which has been generally considered essential for specifying and stabilizing the folded structures of proteins. Outer surface protein A (OspA) from Borrelia burgdorferi contains a three-stranded beta-sheet segment which connects two globular domains. Although this single-layer beta-sheet segment is exposed to solvent on both faces and thus does not contain a hydrophobic core, the segment has a high conformational stability. Here we report the engineering of OspA variants that contain larger single-layer beta-sheets (comprising five and seven beta-strands) by duplicating a beta-hairpin unit within the beta-sheet. Nuclear magnetic resonance and small-angle X-ray scattering analyses reveal that these extended single-layer beta-sheets are formed as designed, and amide hydrogen-deuterium exchange and chemical denaturation show that they are stable. Thus, interactions within the beta-hairpin unit and those between adjacent units, which do not involve the formation of a hydrophobic core, are sufficient to specify and stabilize the single-layer beta-sheet structure. Our results provide an expanded view of protein folding, misfolding and design.

Antigens, Surface↗
PubMed2000

Molecular cloning and expression of a novel klotho-related protein.

Klotho protein is a novel beta-glucosidase-like protein produced predominantly in the kidney. The klotho mouse, which genetically lacks klotho gene expression, manifests various systemic phenotypes resembling aging. In the present study we succeeded in isolating a novel human protein structurally related to klotho protein. The protein possesses one beta-glucosidase-like domain and is 42% identical with klotho protein at the amino acid level. Unlike klotho protein, it possesses neither a signal sequence nor a transmembrane domain, suggesting that it is a cytosolic protein, and thus was termed cytosolic beta-glucosidase-like protein-1 (cBGL1). By Northern blot analysis cBGL1 mRNA was expressed most abundantly in the liver, followed by the small intestine, colon, spleen, and kidney. When klotho and cBGL1 gene expression was examined in renal cell carcinoma tissues, both klotho and cBGL1 mRNA levels in tumors were lower than those in nontumor regions, suggesting that renal epithelial cells may lose klotho and cBGL1 gene expression during the course of malignant transformation. In conclusion, we describe the primary structure and gene expression of a novel protein related to klotho protein.

Aged↗
PubMed2000

Expression of prostaglandin E receptor EP4 subtype in rat adrenal zona glomerulosa: involvement in aldosterone release.

We examined the role of prostaglandin (PG) E receptors in the secretion of aldosterone. PGE2 is known to exert its various biological functions by binding to PGE receptors. There are four subtypes of PGE receptors, EP1, EP2, EP3, and EP4. Among the PGE receptors EP2 and EP4 subtypes are coupled to Gs protein and stimulate adenylyl cyclase. In this study, PGE2 caused a dose-dependent increase in aldosterone production from the rat adrenal zona glomerulosa cells in vitro accompanied with an increase in intracellular cAMP concentration. A specific agonist for EP2, butaprost, did not increase the cAMP production or the aldosterone release, suggesting the possibility that EP4 mediates the secretion of aldosterone by PGE2. Northern blot hybridization analysis disclosed that EP4 gene was expressed in the rat adrenal gland but that EP2 gene was not. In situ hybridization revealed that EP4 mRNA is present abundantly in the zona glomerulosa of rat adrenal gland. These findings suggest that the PGE2-EP4 system is involved in the regulation of aldosterone secretion from the rat adrenal gland.

Aldosterone↗