Stroke, systemic embolism and bleeding rate in non-valvular atrial fibrillation patients without anticoagulation on the real world data in Japan

Background

Anticoagulant therapy is recommended in patients with non-valvular atrial fibrillation (NVAF) for those with CHADS2 ≥2. However, there have been significant number of subjects with CHADS2 ≥2 who receive no anticoagulation. Most of reported real world data have been collected mainly before wide spread use of DOAC. This study evaluated the clinical outcome of no anticoagulant drug therapy in NVAF.

Methods

This study is a non-interventional, observational, retrospective cohort study of NVAF patients in Mie-LIP Database, which is a regional clinical database joining 1 university hospital and 8 general hospitals in Mie prefecture in Japan. Patient enrolment was conducted from 1st Jan. 2016 to 31st Dec. 2018. The primary outcome events are ischemic stroke, systemic embolism, and bleeding events (bleeding to need a blood transfusion, intracranial bleeding, intraocular bleeding, and gastrointestinal bleeding).

Results

7001 patients were included in the current analysis, 2550 patients, 36.4% were treated without any anticoagulant drug therapy. Table 1 shows patients with no anticoagulant drug therapy, mean age was 75.4 years and 42.2% of patients were female. The most frequent comorbidities included hypertension (50.0%), diabetes mellitus (28.2%), heart failure (14.0%), ischemic stroke (12.7%), vascular disease (14.4%) respectively. The annual incidence of ischemic stroke, systemic embolism per 100 person-years is 3.7, and that in each CHADS2 group is 0: 1.4, 1: 1.4, 2: 3.2, 3–6: 8, respectively in Figure 1. The annual incidence of bleeding events is 1.5, and that in each CHADS2 group is 0: 0.7, 1: 1.0, 2: 1.2, 3–6: 2.9, respectively.

Conclusions

Approximately one-thirds of subjects have not received any anticoagulation in the modern DOAC in daily clinical practice in Japan. The rate of ischemic stroke and systemic embolism increased by CHADS2. Stroke or SEE rate was very low in subjects with CHADS2 ≤1, supporting no indication of anticoagulation in current guidelines. Regarding subjects with CHADS2>2, considering the higher risk of stroke, use of anticoagulant drug therapy is recommended.

Funding Acknowledgement

Type of funding source: None

Demonstration of a 3-dB directional coupler with enhanced robustness to gap variations for silicon wire waveguides

We demonstrate a robust 3-dB directional coupler which has a narrow silicon wire core and a wide gap. Sensitivity to the gap variation is decreased to one tenth that of a conventional directional coupler. Better spectral stability due to the enhanced robustness to waveguide geometrical fluctuations was experimentally verified.

A CD40 single-nucleotide polymorphism affects the lymphocyte profiles in the bronchoalveolar lavage of Japanese patients with sarcoidosis

CD40 plays a critical role in adaptive immunity, and alveolar macrophages in patients with sarcoidosis express higher levels of CD40. This study investigated the association of rs1883832, a functional single-nucleotide polymorphism in the CD40 gene with susceptibility to sarcoidosis and phenotypes of sarcoidosis. Genotyping of rs1883832 in 175 Japanese patients with sarcoidosis and 150 age- and sex-matched controls revealed no significant difference between the genotypes of the patient and control groups (CC/CT/TT, 32.8/52.0/14.7% in the patients; 37.3/48.0/14.7% in the controls, P = 0.66; allele C, 59.1% in the patients, 61.3% in the controls, P = 0.57). T-cell and CD4+ cell counts in the bronchoalveolar lavage fluid were significantly higher in the TT genotype group than in the CC and CT genotype group.

Significance of plasma NT-proBNP levels as a biomarker in the assessment of cardiac involvement and pulmonary hypertension in patients with sarcoidosis

BACKGROUND

Cardiac involvement and pulmonary hypertension (PH) are life-threatening complications in sarcoidosis.

OBJECTIVE

This study aimed to investigate the utility of plasma NT-proBNP in the assessment of these conditions in sarcoidosis patients.

STUDY DESIGN AND METHODS

A prospective, observational study was performed on 150 consecutive Japanese sarcoidosis patients. Doppler echocardiography was performed in all subjects, and those who were successfully evaluated for PH status were included in the analysis. Cardiac sarcoidosis was diagnosed based on Japanese guidelines, and PH was defined as estimated systolic pulmonary artery pressure (sPAP) > or = 35 mmHg. The diagnostic accuracy of NT-proBNP according to the presence of cardiac sarcoidosis and PH was assessed based on receiver-operator characteristic (ROC) curves.

RESULTS

130 subjects were successfully evaluated for PH status. Of these, 29 met the diagnostic criteria of cardiac sarcoidosis, and 21 were diagnosed with PH. Plasma NT-proBNP levels were significantly higher in patients with cardiac sarcoidosis (p < 0.0001). Stepwise regression analysis showed that presence of cardiac sarcoidosis, decreased ejection fraction and increased sPAP were all independently associated with higher plasma NT-proBNP levels. Plasma NT-proBNP showed good accuracy in identifying patients with cardiac sarcoidosis (area under the ROC curve; AURC = 0.913). However, even when patients with cardiac sarcoidosis were excluded, plasma NT-proBNP levels could not be used reliably to identify patients with PH (AURC = 0.681).

CONCLUSION

In patients with sarcoidosis, plasma NT-proBNP levels are a useful biomarker to identify cardiac involvement, but not to identify PH.

Gene therapy of liver tumors with human liver-specific nanoparticles

The development of safe and efficient liver-specific gene delivery approaches offers new perspectives for the treatment of liver disease, in particular, liver cancer. We evaluated the therapeutic potential of hepatotropic nanoparticles for gene therapy of liver tumor. These nanoparticles do not contain a viral genome and display the hepatitis B virus L antigen, which is essential to confer hepatic specificity. It has not been shown whether a therapeutic effect could be obtained using L nanoparticles in a human liver tumor xenograft model. Rats bearing human hepatic (NuE) and non-hepatic tumors were injected with L nanoparticles containing a green fluorescent protein (GFP) expression plasmid. GFP expression was observed only in NuE-derived tumors but not in the non-hepatic tumor. The potential for treatment of liver tumors was analyzed using L nanoparticles containing the herpes simplex virus thymidine kinase gene, in conjunction with ganciclovir pro-drug administration. The growth of NuE-derived tumors in L particle-injected rats was significantly suppressed, but not of the non-hepatic tumor control. In summary, this is the first demonstration that nanoparticles could be used for delivery of therapeutic genes with anti-tumor activity into human liver tumors. This intravenous delivery system may be one of the major advantages as compared to many other viral vector systems.

Over-expression system for secretory phospholipase D by Streptomyces lividans

The structural gene for phospholipase D (PLD) of an actinomycete, Streptoverticillium cinnamoneum, together with its promoter region was introduced into Streptomyces lividans using a shuttle vector-pUC702-for Escherichia coli and S. lividans. The transformant was found to secrete a large amount of PLD (about 2.0x10(4) U/l, 42 mg/l) when cultured in a jar fermentor. Both an initial glucose concentration of 17.5 g/l and the feeding of carbon and nitrogen sources are effective for efficient secretion of PLD; under these culture conditions, the amount of PLD secreted reached a maximum level (about 5.5x10(4) U/l, 118 mg/l) after about 60 h. In contrast to the original producer, Stv. cinnamoneum, which secretes only a small amount of PLD (about 1.1x10(3) U/l, 2 mg/l) along with other extracellular proteins, this heterologous expression system is markedly more efficient in production of secretory PLD.

Chum salmon trypsin-catalyzed preferential formation of peptides containing D-amino acid

Chum salmon trypsin-catalyzed peptide synthesis has been studied by using nine series of "inverse substrates," i.e., p-amidinophenyl, p- and m-guanidinophenyl, p- and m-(guanidinomethyl)phenyl, and four position isomers of guanidinonaphthyl esters derived from Nalpha-(tertbutyloxycarbonyl)amino acid as acyl donor components. They were found to couple with an acyl acceptor such as L-alanine p-nitroanilide to produce dipeptide in the presence of trypsin. All substrates tested in this study undergo less enantioselective coupling reaction, and the coupling product was the favorably obtained D-series rather than L-series (in the present case; Nalpha-Boc-D-Ala and Nalpha-Boc-L-Ala). The optimum condition for the coupling reaction was studied by changing the organic solvent, buffer solution, pH, and acyl acceptor concentration. It was found that the enzymatic hydrolysis of the resulting product was negligible.

Spectroscopic observation of intermediates formed during the oxidative half-reaction of copper/topa quinone-containing phenylethylamine oxidase

The catalytic reaction of copper/topa quinone (TPQ) containing amine oxidase consists of the initial, well-characterized, reductive half-reaction and the following, less studied, oxidative half-reaction. We have analyzed the oxidative half-reaction catalyzed by phenylethylamine oxidase from Arthrobacter globiformis (AGAO) by rapid-scan stopped-flow measurements. Upon addition of dioxygen to the substrate-reduced AGAO at pH 8.2, the absorption bands derived from the semiquinone (TPQ(sq)) and aminoresorcinol forms of the TPQ cofactor disappeared within the dead time (<1 ms) of the measurements, indicating that the reaction of the substrate-reduced enzyme with dioxygen is very rapid. Concomitantly, an early intermediate exhibiting an absorption band at about 410 nm was formed, which then decayed with a rate constant of 390 +/- 50 s(-1). This intermediate was detected more prominently in the reaction in D2O buffer (pD 8.1) and was assigned to a Cu(II)-peroxy species. The assignment was based on the observation that addition of H2O2 to the substrate-reduced AGAO under anaerobic conditions led to the formation of a new band at about 415 nm, accompanied by partial quenching of absorption bands derived from TPQ(sq). Other intermediates exhibiting absorption bands at about 310 and 340 nm were also observed in the oxidative half-reaction. Kinetics of the disappearance of these latter bands did not correspond with that of the Cu(II)-peroxy band at 410 nm but did well with that of the increase of the 480 nm absorption band due to the reoxidized TPQ. Rapid increase of the absorption in the 320-370 nm region was also observed for the reaction of the substrate-reduced, Ni-substituted enzyme with dioxygen. On the basis of these results, a possible mechanism is proposed for the oxidative half-reaction of the bacterial copper amine oxidase.

Structure of a quinohemoprotein amine dehydrogenase with an uncommon redox cofactor and highly unusual crosslinking

The crystal structure of the heterotrimeric quinohemoprotein amine dehydrogenase from Paracoccus denitrificans has been determined at 2.05-A resolution. Within an 82-residue subunit is contained an unusual redox cofactor, cysteine tryptophylquinone (CTQ), consisting of an orthoquinone-modified tryptophan side chain covalently linked to a nearby cysteine side chain. The subunit is surrounded on three sides by a 489-residue, four-domain subunit that includes a diheme cytochrome c. Both subunits sit on the surface of a third subunit, a 337-residue seven-bladed beta-propeller that forms part of the enzyme active site. The small catalytic subunit is internally crosslinked by three highly unusual covalent cysteine to aspartic or glutamic acid thioether linkages in addition to the cofactor crossbridge. The catalytic function of the enzyme as well as the biosynthesis of the unusual catalytic subunit is discussed.

The covalent structure of the small subunit from Pseudomonas putida amine dehydrogenase reveals the presence of three novel types of internal cross-linkages, all involving cysteine in a thioether bond

Pseudomonas putida contains an amine dehydrogenase that is called a quinohemoprotein as it contains a quinone and two hemes c as redox active groups. Amino acid sequence analysis of the smallest (8.5 kDa), quinone-cofactor-bearing subunit of this heterotrimeric enzyme encountered difficulties in the interpretation of the results at several sites of the polypeptide chain. As this suggested posttranslational modifications of the subunit, the structural genes for this enzyme were determined and mass spectrometric de novo sequencing was applied to several peptides obtained by chemical or enzymatic cleavage. In agreement with the interpretation of the X-ray electronic densities in the diffraction data for the holoenzyme, our results show that the polypeptide of the small subunit contains four intrachain cross-linkages in which the sulfur atom of a cysteine residue is involved. Two of these cross-linkages occur with the beta-carbon atom of an aspartic acid, one with the gamma-carbon atom of a glutamic acid and the fourth with a tryptophanquinone residue, this adduct constituting the enzyme's quinone cofactor, CTQ. The thioether type bond in all four of these adducts has never been found in other proteins. CTQ is a novel cofactor in the series of the recently discovered quinone cofactors.

Inhibition of copper amine oxidases by pyridine-derived aldoximes and ketoximes

The reactions of pea diamine oxidase (PSAO) and 2-phenylethylamine oxidase from Arthrobacter globiformis (AGAO) with pyridine-derived oximes were studied. Pyridine carbaldoximes and alkyl pyridyl ketoximes act as strong non-competitive inhibitors of the enzymes. The inhibition constants K(i) of these compounds vary between 10(-4) and 10(-5) M, for AGAO and some of the studied oximes were found even micromolar K(i) values. The presence of pyridine moiety in the studied compounds has remarkable influence on the inhibition potency. Elementary oximes lacking the heterocyclic ring, i.e., aliphatic (acetone oxime), alicyclic (cyclohexanone oxime) and aromatic (benzaldoxime), are considerably weaker non-competitive inhibitors (K(i) similar to 10(-3) or 10(-2) M). The position of the pyridine ring substitution by -C(R)=NOH group does not play a significant role for the inhibition potency of the studied oxime compounds. If the pyridine nitrogen is quaternised (in hydroxyiminomethyl-1-methylpyridinium iodides), the compound looses its inhibitory properties. Extended length of alkyl substituents on the ketoxime group of alkyl pyridyl ketoximes increases the K(i) value. The enzyme-bound copper represents one of possible target sites for pyridine-derived oxime inhibitors. The addition of an alkyl pyridyl ketoxime or a pyridine carbaldoxime to a native PSAO sample perturbs the absorption spectrum of the enzyme (by an absorption increase in the region 300-400 nm) that is not observed in the spectrum of reacted PSAO apoenzyme. However, an additional formation of hydrogen bonds with amino acid side-chains at the active site should be considered, namely for 3- and 4-substituted pyridine derivatives.

Physicochemical and immunological characterization of hepatitis B virus envelope particles exclusively consisting of the entire L (pre-S1 + pre-S2 + S) protein

The hepatitis B virus (HBV) envelope (env) protein is composed of three regions; the 108- or 119-residue pre-S1 region involved in the direct interaction with hepatocytes, the 55-residue pre-S2 region associated with the polymerized albumin-mediated interaction, and the major 226-residue S protein region. Thus, to improve the immunogenic potency of conventional HB vaccines, development of a new vaccine containing the entire pre-S1 region in addition to pre-S2 and S is desired. We previously reported the efficient production of the HBV env L (pre-S1 + pre-S2 + S) protein in the recombinant yeast cells [J Biol Chem 267 (1992) 1953]. In this study, the HBV env L protein produced as nano-particles in yeast has been purified and characterized. By equilibrium sedimentation, an average molecular weight of L particle was estimated to be approximately 6.4 x 10(6), indicating that about 110 molecules of L proteins are assembled into an L particle. By atomic force microscopy in a moist atmosphere, the L particles were observed as large spherical particles with a diameter of 50-500 nm. The L particles were stable on short-time heating at a high temperature and long-time storage at a low temperature but rather unstable on repeated freezing and thawing and treatment with dithiothreitol. When immunized in mice, L particles elicited efficiently and simultaneously the anti-S, anti-pre-S2, and anti-pre-S1 antibodies. The ED(50) values in mice for the anti-S and anti-pre-S2 antibodies were similar to those elicited by the M (pre-S2 + S) particles. Furthermore, the anti-pre-S1 rabbit antibodies were found to recognize various segments of the pre-S1 region, including the pre-S1 (21-47) segment. These results show the high ability of L particles to induce all antibodies against HBV env proteins, hence promising the future application of L particles for the next generation HB vaccine.

X-ray crystallographic analyses of complexes between bovine beta-trypsin and Schiff base copper(II) or iron(III) chelates

To establish the structural basis underlying the activity of a novel series of metal-chelate trypsin inhibitors, the structures of p-amidinosalicylidene-l-alaninato(aqua)copper(II) (1a), m-amidinosalicylidene-l-alaninato(aqua)copper(II) (1b), bis(p-amidinosalicylidene-l-alaninato)iron(III) (2a), and bis(m-amidinosalicylidene-l-alaninato)iron(III) (2b) bound to bovine beta-trypsin were studied by X-ray crystallography. The amidinium group of the inhibitor donates hydrogen bonds to Asp189, Gly219 and Ser190, as seen before in trypsin-benzamidine complexes. The copper(II) ion of 1a is situated away from trypsin's catalytic triad residues, and is octahedrally coordinated by a Schiff base and three water molecules. In contrast, the copper(II) ion of 1b is situated close to the catalytic triad and adopts a square pyramidal coordination geometry. The iron(III) ion of 2a is octahedrally coordinated by two Schiff base ligands and, like the copper(II) ion of 1a, is situated away from the catalytic triad. The p-amidinophenyl ring of a second Schiff base ligand of 2a is directed toward a hydrophobic groove formed by Trp215 and Leu99. Finally, the iron(III) ion of 2b appears to be replaced by magnesium(II), which is octahedrally coordinated by a Schiff base, Gln192 and two water molecules. One of the Schiff base ligands seen in the trypsin-2a complex or in the unbound form of 2b is replaced by water molecules and Gln192. His57 and Ser195 form water-mediated interactions with the magnesium(II) ion of 2b, and Ser195 also forms a hydrogen bond with the phenolic oxygen atom of the Schiff base ligand. These structures reveal a novel mode of interaction between metal-chelate inhibitors and serine proteases, thus providing a structural basis for the development of more potent inhibitors against a variety of trypsin-like enzymes.

Identification of novel membrane-bound phospholipase D from Streptoverticillium cinnamoneum, possessing only hydrolytic activity

A membrane-bound phospholipase D (PLD) has been identified and isolated in a soluble form from an actinomycete, Streptoverticillium cinnamoneum. The enzyme has a monomeric structure with a molecular size of about 37 kDa, being the smallest among the enzymes so far reported. The enzyme catalyzes the hydrolysis of phosphatidylethanolamine and phosphatidylserine as preferred substrates, but not the transphosphatidylation reaction of their phospholipid groups to ethanol. Together with the absence of immunochemical cross-reactivity, these enzymatic properties demonstrate that the membrane-bound enzyme is distinct from the extracellular enzyme recently characterized and cloned from the same bacterial strain [C. Ogino et al., J. Biochem. 125 (1999) 263-269] and is therefore regarded as a novel prokaryotic PLD.

Anionic trypsin from chum salmon: activity with p-amidinophenyl ester and comparison with bovine and Streptomyces griseus trypsins

An anionic trypsin from pyloric caeca of chum salmon (Oncorhynchus keta) was purified by ammonium sulfate and acetone fractionation followed by affinity chromatography, gel-filtration, and DEAE-anion exchange chromatography. The apparent molecular mass was about 24 kDa as determined by SDS-PAGE. The anionic chum salmon trypsin was moderately active toward esterase substrates such as tosyl-L-arginine methyl ester and tosyl-L-lysine methyl ester. Its amidase activity for benzoyl-L-arginine p-nitroanilide was comparative to those of bovine and Streptomyces griseus trypsins. Kinetic characteristics of anionic chum salmon, bovine, and Streptomyces griseus trypsins toward inverse substrate (p-amidinophenyl ester) were compared. Inverse substrate behaved as a specific substrate for anionic chum salmon trypsin with specific binding, efficient acylation, and relatively slow deacylation.

ENH, containing PDZ and LIM domains, heart/skeletal muscle-specific protein, associates with cytoskeletal proteins through the PDZ domain

The Enigma homologue protein (ENH), containing an N-terminal PDZ domain and three C-terminal LIM domains, is a heart and skeletal muscle-specific protein that has been shown to preferentially interact with protein kinase C beta (PKCbeta) through the LIM domains (Kuroda et al., J. Biol. Chem. 271, 31029-31032, 1996). We here demonstrate that ENH is colocalized with a cytoskeletal protein alpha-actinin in the Z-disk region of rat neonatal cardiomyocytes. Pull-down assays using the glutathione-S-transferase-fusion system also showed the interaction of the PDZ domain of ENH with actin and alpha-actinin. Furthermore, by combined use of the in silico and conventional cDNA cloning methods, we have isolated three ENH-related clones from a mouse heart-derived cDNA library: mENH1 (591 amino acid residues) corresponding to rat ENH, mENH2 (337 residues), and mENH3 (239 residues); the latter two containing only a single PDZ domain. Deciphering their cDNA sequences, these mENH1-3 mRNAs appear to be generated from a single mENH gene by alternative splicing. Northern blot analyses using human cancer cells and mouse embryos have shown expression of each mENH mRNA to vary considerably among the cell types and during the developmental stage. Together with a recent finding that PKCbeta is markedly activated in the cardiac hypertrophic signaling, these results suggest that ENH1 plays an important role in the heart development by scaffolding PKCbeta to the Z-disk region and that ENH2 and ENH3 negatively modulate the scaffolding activity of ENH1.

Molecular cloning and heterologous expression of pea seedling copper amine oxidase

The cDNA coding for copper amine oxidase has been cloned from etiolated pea seedlings (Pisum sativum). The deduced amino acid sequence, consisting of 674 residues including the signal peptide, agreed well with those reported for the enzymes from a different cultivar of P. sativum and other plant sources, except for several evolutionary replacements located mostly on the molecular surface. A heterologous expression system for the cloned pea enzyme was constructed with the yeast Pichia pastoris, using the AOX1 promoter and the yeast alpha-factor secretion signal. Adding copper to the culture medium increased the secretion of an active, quinone-containing enzyme. Furthermore, the inactive enzyme produced in a copper-deficient medium was activated considerably by subsequent incubation with excess cupric ions. These results strongly suggest that the Tyr-derived redox cofactor, 2,4,5-trihydroxyphenylalanylquinone (topa quinone, TPQ), is produced in the plant enzyme by post-translational modification that proceeds through the copper-dependent, self-processing mechanism, as in the enzymes from bacteria and yeast.

Trypsin-catalyzed peptide synthesis with m-guanidinophenyl and m-(guanidinomethyl)phenyl esters as acyl donor component

Two series of inverse substrates, m-guanidinophenyl and m-(guanidinomethyl)phenyl esters derived from N-(tert-butyloxycarbonyl)-amino acid, were prepared as an acyl donor component for trypsin-catalyzed peptide synthesis. The kinetic behavior of these esters toward tryptic hydrolysis was analyzed. They were found to couple with an acyl acceptor such as L-alanine p-nitroanilide to produce dipeptide in the presence of trypsin. Streptomyces griseus trypsin was a more efficient catalyst than the bovine trypsin. Within the enzymatic peptide coupling methods, this approach was shown to be advantageous, since the resulting peptides are resistant to the enzymatic hydrolysis.

Involvement of epidermal growth factor-like domain of NELL proteins in the novel protein-protein interaction with protein kinase C

NELL proteins are the thrombospondin-1-like proteins that are strongly expressed in neural tissues, containing six epidermal growth factor (EGF)-like domains. By radiolabeling of the NELL protein-expressing COS-7 cells with [(32)P]orthophosphate, here we demonstrate that NELL proteins are synthesized as phosphoproteins by interacting with protein kinases in the cells. By immunoprecipitation and in vitro phosphorylation assays, we have also found that NELL proteins expressed in COS-7 cells are associated with and phosphorylated by protein kinase C betaI (PKCbetaI). Further analysis using various deletion mutants of NELL proteins by the yeast two-hybrid assay has revealed their EGF-like domains to be involved in the isoform-specific interaction with PKC. Conversely, the NH(2)-terminal variable region of PKC isoforms has been found essential for the interaction with NELL proteins. Because NELL proteins are expressed mainly in the cytoplasm of neuronal cells, unlike most EGF-like domain-containing extracellular proteins, the novel protein-protein interaction identified here between the EGF-like domains of NELL proteins and PKC suggests that EGF-like domains of intracellular proteins can be a target of PKC that mediates various signaling pathways.

Biochemical characterization and expression analysis of neural thrombospondin-1-like proteins NELL1 and NELL2

Two closely related genes coding for NELL proteins (NELL1 and NELL2) have been cloned by the yeast two-hybrid screening of a rat brain cDNA library with the regulatory domain of protein kinase C betaI (PKCbetaI) as bait. The rat NELL proteins show about 55% identity with each other and contain several protein motifs assigned to a secretion signal peptide, an NH(2)-terminal thrombospondin-1 (TSP-1)-like module, five von Willebrand factor C domains, and six epidermal growth factor-like domains; the NELL proteins share many protein motifs with TSP-1. The NELL proteins expressed in COS-7 cells are homotrimeric glycoproteins and possess heparin-binding activity. Furthermore, while NELL1 and NELL2 show distinct subcellular localization in cytoplasm, they both are partially secreted into the culture medium of COS-7 cells. Although the NELL1 mRNA is faintly expressed in adult neural cells, the NELL2 mRNA is expressed abundantly, particularly in the pyramidal cells of rat hippocampus, showing neuronal high plasticity. During mouse embryogenesis, expression of the NELL2 mRNA is initiated 7-11 days postcoitum, simultaneously with neural plate formation. These results strongly suggest that the NELL2 protein, similar to but not identical with TSP-1, is involved in the growth and differentiation of neural cells. Additionally, the NELL1 and NELL2 mRNAs were found to be expressed abundantly in Burkitt's lymphoma Raji cells and colorectal adenocarcinoma SW480 cells, respectively. Thus, it is likely that the NELL proteins also participate in the growth, differentiation, and oncogenesis of cancer cell lines.

Spectroscopic characterization of carbon monoxide complexes generated for copper/topa quinone-containing amine oxidases

Carbon monoxide complexes have been generated for copper/topa quinone (TPQ)-containing amine oxidases from Arthrobactor globiformis (AGAO) and Aspergillus niger (AO-I) and characterized by various spectroscopic measurements. Addition of CO to AGAO anaerobically reduced with its substrate 2-phenylethylamine led to a slight increase of absorption bands at 440 and 470 nm derived from the semiquinone form (TPQ(sq)) of the TPQ cofactor, concomitantly giving rise to new CO-related absorption bands at 334 and 434 nm. The intensity of the TPQ(sq) radical EPR signal at g = 2.004 also increased in the presence of CO, while its hyperfine coupling structure was affected insignificantly. FT-IR measurements revealed C-O stretching bands (nu(CO)) at 2063 and 2079 cm(-1) for the CO complex of the substrate-reduced AGAO (at 2085 cm(-1) for AO-I), which shifted nearly 100 cm(-1) to lower frequencies upon using (13)C(18)O. Collectively, these results suggest that CO is bound to the Cu(I) ion in the Cu(I)/TPQ(sq) species formed in the reductive half-reaction of amine oxidation, thereby shifting the Cu(II)/aminoresorcinol right arrow over left arrow Cu(I)/semiquinone equilibrium toward the latter. When AGAO was reduced with dithionite, an intermediary form of the enzyme with Cu(II) reduced to Cu(I) but TPQ still in the oxidized state (TPQ(ox)) was produced. Dithionite reduction of AGAO in the presence of CO resulted in the immediate formation of FT-IR bands at 2064 and 2083 cm(-1), which were assigned to the nu(CO) bands of the CO bound to the TPQ(ox) enzyme. The intense 2083 cm(-1) band was then displaced by a new band at 2077 cm(-1), corresponding to the formation of the fully reduced topa. Significant variation of these nu(CO) frequencies indicates that vibrational properties of CO bound to copper amine oxidases are sensitively influenced by the coordination structure of the Cu(I) ion, which may be modulated by the chemical and redox states of the TPQ cofactor.

Ligation errors in DNA computing

DNA computing is a novel method of computing proposed by Adleman (1994), in which the data is encoded in the sequences of oligonucleotides. Massively parallel reactions between oligonucleotides are expected to make it possible to solve huge problems. In this study, reliability of the ligation process employed in the DNA computing is tested by estimating the error rate at which wrong oligonucleotides are ligated. Ligation of wrong oligonucleotides would result in a wrong answer in the DNA computing. The dependence of the error rate on the number of mismatches between oligonucleotides and on the combination of bases is investigated.

Mammalian homologue of the Caenorhabditis elegans UNC-76 protein involved in axonal outgrowth is a protein kinase C zeta-interacting protein

By the yeast two-hybrid screening of a rat brain cDNA library with the regulatory domain of protein kinase C zeta (PKCzeta) as a bait, we have cloned a gene coding for a novel PKCzeta-interacting protein homologous to the Caenorhabditis elegans UNC-76 protein involved in axonal outgrowth and fasciculation. The protein designated FEZ1 (fasciculation and elongation protein zeta-1) consisting of 393 amino acid residues shows a high Asp/Glu content and contains several regions predicted to form amphipathic helices. Northern blot analysis has revealed that FEZ1 mRNA is abundantly expressed in adult rat brain and throughout the developmental stages of mouse embryo. By the yeast two-hybrid assay with various deletion mutants of PKC, FEZ1 was shown to interact with the NH2-terminal variable region (V1) of PKCzeta and weakly with that of PKCepsilon. In the COS-7 cells coexpressing FEZ1 and PKCzeta, FEZ1 was present mainly in the plasma membrane, associating with PKCzeta and being phosphorylated. These results indicate that FEZ1 is a novel substrate of PKCzeta. When the constitutively active mutant of PKCzeta was used, FEZ1 was found in the cytoplasm of COS-7 cells. Upon treatment of the cells with a PKC inhibitor, staurosporin, FEZ1 was translocated from the cytoplasm to the plasma membrane, suggesting that the cytoplasmic translocation of FEZ1 is directly regulated by the PKCzeta activity. Although expression of FEZ1 alone had no effect on PC12 cells, coexpression of FEZ1 and constitutively active PKCzeta stimulated the neuronal differentiation of PC12 cells. Combined with the recent finding that a human FEZ1 protein is able to complement the function of UNC-76 necessary for normal axonal bundling and elongation within axon bundles in the nematode, these results suggest that FEZ1 plays a crucial role in the axon guidance machinery in mammals by interacting with PKCzeta.

Application of Schiff base copper(II) and iron(III) chelates to site-specific cleavage of a trypsin

Amidine-containing Schiff base iron(III) and copper(II) chelates were prepared from alpha-amino acid, metal ion, and salicylaldehyde. These chelates behaved as specific inhibitors of trypsin, with Ki values in the range 10(-5)-10(-6) M. Selective cleavage of the trypsin backbone resulting from specific binding of the chelate to the trypsin active site was investigated. Cleavage was observed when trypsin was incubated with amidine-containing copper(II) or iron(III) chelate, H2O2, and ascorbate. Examination of the three-dimensional structure of trypsin suggests that cleavage occurred at a peptide bond within the Gly195-Ala204 sequence.

Biologically selective potassium channel openers having 1,1-diethylpropyl group

To find out selective potassium channel openers (PCOs), we synthesized several 3,5-disubstituted phenylcyanoguanidine derivatives and investigated their structure-activity relationships (SAR). As a result, we discovered selective PCOs having 1,1-diethylpropyl group toward antihypertensive activity.

Exploring a channel to the active site of copper/topaquinone-containing phenylethylamine oxidase by chemical modification and site-specific mutagenesis

Copper amine oxidase contains an organic redox cofactor, 2,4, 5-trihydroxyphenylalaninequinone (topaquinone, TPQ), derived by the post-translational modification of a specific tyrosyl residue. To identify amino acid residues participating in the biogenesis of TPQ in the recombinant phenylethylamine oxidase from Arthrobacter globiformis, we have modified the copper/TPQ-less apoenzyme and the copper/TPQ-containing holoenzyme with 4-fluoro-7-nitrobenzo-2-oxa-1, 3-diazole (NBD-F). In the apoenzyme modification, the Cu2+-dependent, self-processing formation of the TPQ cofactor was retarded in accordance with the amount of NBD incorporated. The holoenzyme was also rapidly inactivated by incubation with NBD-F. The inactivation was prevented almost completely in the presence of an oxidation product from phenylethylamine, phenylacetaldehyde. Furthermore, the reaction of an inhibitor, phenylhydrazine, with TPQ was much slower in the NBD-labeled holoenzyme than in the native holoenzyme. Sequence analysis of the NBD-labeled holoenzyme has identified Lys184 and Lys354 as the labeled sites. The two Lys residues are located close to the entrance to a channel, which has been found by recent X-ray crystallographic studies to be suitable for the movement of substrates and products to and from the Cu2+/TPQ-active site buried in the protein interior (Wilce, M. C. J., et al. (1997) Biochemistry 36, 16116-16133). However, site-specific mutant enzymes for Lys184, Lys354, and the neighboring invariant His355 had normal capacities for the TPQ formation in apoenzyme. These residues were also found to be dispensable for catalytic activity of holoenzyme. Thus, modification of Lys184 and Lys354 with NBD-F presumably causes structural perturbations of the substrate channel or steric hindrance for the access of small molecules to the active site through the channel.

Exchange of nucleoside monophosphate-binding domains in adenylate kinase and UMP/CMP kinase

Two types of active chimeric enzymes have been constructed by genetic engineering of chicken cytosolic adenylate kinase (AK) and porcine brain UMP/CMP kinase (UCK): one, designated as UAU, carries an AMP-binding domain of AK in the remaining body of UCK; and the other, designated as AUA, carries a UMP/CMP-binding domain of UCK in the remaining body of AK. Steady-state kinetic analysis of these chimeric enzymes revealed that UAU is 4-fold more active for AMP, 40-fold less active for UMP, and 4-fold less active for CMP than the parental UCK, although AUA has considerably lowered reactivity for both AMP and UMP. Circular dichroism spectra of the two chimeric enzymes suggest that UAU and AUA have similar folding structures to UCK and AK, respectively. Furthermore, proton NMR measurements of the UCK and UAU proteins indicate that significant differences in proton signals are limited to the aromatic region, where an imidazole C2H signal assigned to His31 shows a downfield shift upon conversion of UCK to UAU, and the signals assigned to Tyr49 and Tyr56 in the UMP/CMP-binding domain disappear in UAU. In contrast, AUA has a Tm value about 11 degreesC lower than AK, whereas UAU and UCK have similar Tm values. These results together show that the substrate specificity of nucleoside monophosphate (NMP) kinases can be engineered by the domain exchange, even though the base moiety of NMP appears to be recognized cooperatively by both the NMP-binding domain and the MgATP-binding core domain.

Transcriptional activity of RBCK1 protein (RBCC protein interacting with PKC 1): requirement of RING-finger and B-Box motifs and regulation by protein kinases

The RBCK1 protein was recently identified as a protein kinase C-interacting protein with a new type of RBCC (RING-B-Box-Coiled-coil) region, possessing both DNA-binding and transcriptional activities unlike other proteins in the RBCC protein family (Tokunaga et al. Biochem. Biophys. Res. Commun. 244, 353-359, 1998). To identify protein motifs in the RBCC region of RBCK1 essential for the transcriptional activity, RBCK1 mutant proteins have been constructed and analyzed by using the GAL4 chimeric transcription regulator system. We have found that both of the RING-finger and the B-Box motifs are indispensable for the transcriptional activity of RBCK1. This is the first observation that these protein motifs of the RBCC protein family play a crucial role in transcriptional activation. In addition, we have examined the effect of co-expression of several protein kinases on the transcriptional activity of RBCK1. Protein kinase A (PKA) was found to enhance the activity by about eightfold, whereas both ERK (extracellular signal-regulated kinase) activator kinase 1 (MEK1) and MEK kinase 1 (MEKK1) significantly repressed the activity. Because RBCC proteins are presumed to act as a proto-oncoprotein, these results suggest that the RBCK1 protein is involved in the intracellular signaling cascades along with PKA, MEK1, and MEKK1 and mediates cell growth and differentiation.

Enzymatic peptide synthesis with p-guanidinophenyl and p-(guanidinomethyl)phenyl esters as acyl donors

Two series of "inverse substrates", N-Boc-amino acid p-guanidinophenyl and p-(guanidinomethyl)phenyl esters, were prepared as acyl donor components for enzymatic peptide synthesis. The kinetic behavior of these esters toward bovine and Streptomyces griseus (SG) trypsin was analyzed. The spatial requirement of the active site of these enzymes for catalytic efficiency is discussed based on the steric characteristics of the substrates. These substrates were found to couple readily with amino acid p-nitroanilides to produce peptides. SG trypsin was the most efficient catalyst among the enzymes tested (bovine, porcine, and SG trypsin).

Crystal structures of the copper-containing amine oxidase from Arthrobacter globiformis in the holo and apo forms: implications for the biogenesis of topaquinone

The crystal structures of the copper enzyme phenylethylamine oxidase from the Gram-positive bacterium Arthrobacter globiformis (AGAO) have been determined and refined for three forms of the enzyme: the holoenzyme in its active form (at 2.2 A resolution), the holoenzyme in an inactive form (at 2.8 A resolution), and the apoenzyme (at 2.2 A resolution). The holoenzyme has a topaquinone (TPQ) cofactor formed from the apoenzyme by the post-translational modification of a tyrosine residue in the presence of Cu2+. Significant differences between the three forms of AGAO are limited to the active site. The polypeptide fold is closely similar to those of the amine oxidases from Escherichia coli [Parsons, M. R., et al. (1995) Structure 3, 1171-1184] and pea seedlings [Kumar, V., et al. (1996) Structure 4, 943-955]. In the active form of holo-AGAO, the active-site Cu atom is coordinated by three His residues and two water molecules in an approximately square-pyramidal arrangement. In the inactive form, the Cu atom is coordinated by the same three His residues and by the phenolic oxygen of the TPQ, the geometry being quasi-trigonal-pyramidal. There is evidence of disorder in the crystals of both forms of holo-AGAO. As a result, only the position of the aromatic group of the TPQ cofactor, but not its orientation about the Cbeta-Cgamma bond, is determined unequivocally. In apo-AGAO, electron density consistent with an unmodified Tyr occurs at a position close to that of the TPQ in the inactive holo-AGAO. This observation has implications for the biogenesis of TPQ. Two features which have not been described previously in amine oxidase structures are a channel from the molecular surface to the active site and a solvent-filled cavity at the major interface between the two subunits of the dimer.

Topaquinone-dependent amine oxidases: identification of reaction intermediates by Raman spectroscopy

Resonance Raman (RR) spectroscopy has proven to be an excellent technique for providing structural information about the 2,4, 5-trihydroxyphenylalaninequinone (TPQ) cofactor and for identifying the source of oxygen atoms during the posttranslational synthesis of the cofactor. Through specific labeling of the C2, C4, and C5 oxygens of TPQ in phenylethylamine oxidase (PEAO) from Arthrobacter globiformis, we have identified the C=O stretch of the C5 carbonyl at 1683 cm-1 (-27 in 18O) and the C=O stretch of the C2 carbonyl at 1575 cm-1 (-21 in 18O). These vibrational frequencies show that the C-O moiety at C5 has far greater double-bond character than at C2 or C4, thereby explaining the exclusive nucleophilic attack at the C5 position by substrates and substrate analogs. Bovine serum amine oxidase (BSAO) exhibits a similar nu(C=O) mode at 1678 cm-1 (-22 cm-1 in 18O). Aniline reacts with the TPQ cofactor of PEAO to form a new derivative (lambdamax at 450 nm) with properties similar to the proposed substrate-imine intermediate in the catalytic cycle. It retains the C2=O spectral features of the native enzyme and exhibits a new C5=N stretch at 1603 cm-1 (-29 in 15N). In contrast, methylamine reacts with both PEAO and BSAO under anaerobic conditions to form a different stable adduct (lambdamax at 385 nm) with properties closer to the proposed product-imine intermediate in the catalytic cycle. This species has a distinctive RR spectrum with a C=N stretch at 1617 cm-1 that corresponds to the atoms of the added methylamine (-58 cm-1 with CD3NH2, -19 cm-1 with CH315NH2). The lack of D2O dependence of nu(C=N) shows that this is a deprotonated imine, which would be more stable toward hydrolysis than the postulated protonated imine in the enzymatic reaction. However, the BSAO product imine (from methylamine) does undergo hydrolysis and conversion to semiquinone upon addition of cyanide. It is possible that the inactive form of the product imine is stabilized by deprotonation and flipping of the TPQ ring [Cai, D., Dove, J., Nakamura, N., Sanders-Loehr, J., and Klinman, J. P. (1997) Biochemistry 36, 11472-11478].

Mechanistic studies of topa quinone biogenesis in phenylethylamine oxidase

An alternative purification for apophenylethylamine oxidase from Arthrobacter globiformis has been developed, which avoids the use of possible contaminants that may interfere with the topa quinone (TPQ) self-processing reaction. The binding of Cu(II) and the kinetics of TPQ formation in these enzyme preparations have been reinvestigated. Our results show that Cu(II) is not significantly reduced when added to the apoprotein under anaerobic conditions. The Cu(II) EPR and circular dichroism spectra of the initially formed complex are different from the spectra of the mature Cu(II)/TPQ-containing protein, indicating that the active site structure must be altered during TPQ formation. The kinetics we observe are cleanly first-order in protein [measured subsequent to Cu(II) binding] when dioxygen is present in pseudo-first-order excess (k(obs) = 1.5 min(-1)). We found no rate dependence on copper, so long as one copper per subunit was present. This indicates that tyrosine oxidation to give TPQ depends only on the copper that is bound in the active site. These results differ from those originally reported; an alternative mechanism, which involves attack of an activated copper-oxygen species on a tyrosine radical intermediate, is proposed for TPQ formation.

Role of conserved Asn-Tyr-Asp-Tyr sequence in bacterial copper/2,4, 5-trihydroxyphenylalanyl quinone-containing histamine oxidase

Copper amine oxidase contains a covalently bound quinonoid cofactor, 2,4,5-trihydroxyphenylalanyl quinone (TPQ), which is synthesized by post-translational modification of a specific tyrosyl residue occurring in the highly conserved sequence, Asn-Tyr-(Asp/Glu)-Tyr. To elucidate the role(s) of the conserved sequence in the biogenesis of TPQ, each of the corresponding residues at positions 401-404 in the recombinant histamine oxidase from Arthrobacter globiformis has been replaced with other amino acids by site-directed mutagenesis. When Asn-401 was changed to Asp or Gln, the rate of TPQ formation by copper-dependent self-processing was 10(3)- to 10(4)-fold slower than in the wild-type enzyme. When Tyr-402 was replaced by Phe, TPQ was not formed at all, showing that Tyr-402 is essential as the precursor to TPQ. In contrast, Asp-403 could be replaced by Glu without changes in the rate of TPQ formation, whereas its replacement by Asn led to a marked decrease. Furthermore, when Tyr-404 was changed to Phe, TPQ was formed swiftly on incubation with copper ions, but the TPQ enzyme exhibited very low activity with altered substrate specificity. These results collectively indicate that a very rigorous structural motif is required for efficient formation of TPQ and for the catalytic activity in the active site of copper amine oxidases.

Synthesis and tryptic hydrolysis of p-guanidinophenyl esters derived from amino acids and peptides

A facile synthetic method for p-guanidinophenyl esters derived from a variety of amino acids and peptides, including D-amino acids, is presented. The kinetic behavior of trypsin towards these synthetic esters, inverse substrates, was analyzed. The spatial requirement of the enzyme active site for catalytic efficiency is discussed based on the steric characteristics of the substrates.

Trypsin-catalyzed peptide synthesis and various p-guanidinophenyl esters as acyl donors

Trypsin-catalyzed peptide synthesis has been studied by using p-guanidinophenyl esters of N alpha-(tert-butyloxycarbonyl)amino acid and peptide as acyl donor components. The reaction conditions were optimized for organic solvents, pH, and concentration of acceptor. The method was especially useful for the preparation of various peptides containing D-amino acids. The enzymatic hydrolysis of the resulting products was negligible.

Biosynthesis of topa quinone cofactor in bacterial amine oxidases. Solvent origin of C-2 oxygen determined by Raman spectroscopy

Resonance Raman spectroscopy is an excellent technique for providing structural information on the 2,4, 5-trihydroxyphenylalanine quinone (TPQ) cofactor in copper-containing amine oxidases. This technique has been used to investigate the copper- and O2-dependent biosynthesis of the TPQ cofactor in phenylethylamine oxidase (PEAO) and histamine oxidase from Arthrobacter globiformis. Incubation of the holoenzyme in H218O causes frequency shifts at 1684(-26) cm-1 in PEAO and at 1679(-28) cm-1 in histamine oxidase, allowing this feature to be assigned to the C=O stretch of a single carbonyl group at the C-5 position. When apoprotein is reacted with Cu(II) and O2 in the presence of H218O, the resultant holoproteins show increased shifts of -3 to -6 cm-1 in a number of other vibrational modes, particularly at 411 and 1397 cm-1. Because these small shifts persist when the H218O-regenerated protein is back-exchanged into H216O, they can be assigned to oxygen isotope substitution at the C-2 postion. No isotope shifts are observed when apoprotein is regenerated with Cu(II) in the presence of 18O2. Thus, it is concluded that the C-2 oxygen atom of TPQ originates from H2O rather than O2. The isotope dependence of the 1397-cm-1 mode allows it to be assigned to the C O moiety at the C-2 position, with its low frequency being indicative of only partial double bond character. Similar frequency shifts due to 18O at C-2 are observed in the resonance Raman spectra of H218O-regenerated PEAO after derivatization of the C-5 carbonyl with either p-nitrophenylhydrazine (-5 cm-1 at 480 cm-1) or methylamine (-5 cm-1 at 1301 cm-1). Taken together, these results indicate that the TPQ cofactor in the native enzyme has substantial electron delocalization between the C-2 and C-4 oxygens and that only the C-5 oxygen has predominantly C=O character.

Biogenesis of novel quinone coenzymes

Recently, two novel quinonoid coenzymes, 2,4,5-trihydroxyphenylalanine quinone (topa quinone; TPQ) and tryptophan tryptophylquinone (TTQ), were identified in copper-containing amine oxidase and methylamine dehydrogenase, respectively. Unlike the formerly known quinonoid coenzyme, pyrroloquinoline quinone (PQQ), which is non-covalently bound to several prokaryotic dehydrogenases and produced through its own biosynthetic pathway, each of TPQ and TTQ is bound covalently to the polypeptide chain as an integral amino acid residue and encoded by a codon for a normal (unmodified) amino acid in the gene. Thus, these coenzymes must be generated through post-translational modification of the precursor amino acid; for TPQ, oxidation of a specific tyrosine occurring in the consensus Asn-Tyr-Asp/Glu sequence, and for TTQ, oxidation of a specific tryptophan and cross-linking with another tryptophan separated by 50 residues in the same polypeptide chain. We recently demonstrated that, using the inactive precursor forms of bacterial copper amine oxidases, TPQ is generated through self-processing of the protein with the participation of the bound copper ions. On the other hand, the absence of a prosthetic metal ion in methylamine dehydrogenase as well as its existence in the periplasm renders TTQ biogenesis more complicated, likely requiring an external enzymatic system(s).