PubMed Health⌕ Search

Biomedical subjects

M Nagahama

Publications and source records attributed to M Nagahama.

At least 19 recordsLinked to original sources
PubMed1992

Purification and characterization of furin, a Kex2-like processing endoprotease, produced in Chinese hamster ovary cells.

Furin, a mammalian homolog of the yeast Kex2 protease, is associated with Golgi membranes and is involved in cleavage of precursor proteins at sites marked by the Arg-X-Lys/Arg-Arg (RXK/RR) motif. We have recently shown that a furin mutant lacking the transmembrane domain can be secreted from cDNA-transfected cells with proteolytic activity for the fluorogenic peptide t-butoxycarbonyl-Arg-Val-Arg-Arg-4-methylcoumarin-7- amide. In this study, we purified and characterized the recombinant furin from the conditioned medium of these cells. Furin was purified as a mixture of 83- and 81-kDa forms and a 96-kDa form. The differences in molecular mass were not due to differences in molecular mass were not due to differences in glycosylation. Moreover, all forms had the same NH2-terminal sequence beginning at the residue after the Arg-Ala-Lys-Arg sequence. These data suggest that the three different forms may be produced by differential COOH-terminal processing of a furin molecule and that mature furin may be autocatalytically produced. Both enzyme preparations showed a pH optimum at 7.0, required Ca2+ for the activity, and showed essentially the same inhibitor profile. These properties resembled those of the Kex2 protease. Both preparations efficiently cleaved fluorogenic peptides with an RXK/RR sequence and moderately cleaved a peptide with an RXXR sequence, but did not cleave dibasic peptides. The sequence requirements determined in vitro were compatible with those determined by expression studies in cultured cells. These data unequivocally demonstrate that furin is an endogenous cellular protease responsible for cleavage of precursor proteins mainly at RXK/RR sites.

Amino Acid Sequence↗
PubMed1992

Consensus sequence for precursor processing at mono-arginyl sites. Evidence for the involvement of a Kex2-like endoprotease in precursor cleavages at both dibasic and mono-arginyl sites.

Many peptide hormones and neuropeptides are produced from larger, inactive precursors through endoproteolysis at sites usually marked by paired basic residues (primarily Lys-Arg and Arg-Arg), or occasionally by a monobasic residue (primarily Arg). Based upon data concerning processing of prorenin and its mutants around the native Lys-Arg cleavage site expressed in mouse pituitary AtT-20 cells, we present the following sequence rules that govern mono-arginyl cleavages: (a) a basic residue at the fourth (position -4) or the sixth (position -6) residue upstream of the cleavage site is required, (b) at position -4, Arg is more favorable than Lys, and (c) at position 1, a hydrophobic aliphatic residue is not suitable. These rules are compatible with those proposed by comparison of precursor sequences around mono-arginyl cleavage sites. We also provide evidence that precursor cleavages at mono-arginyl and dibasic sites can be catalyzed by the same Kex2-like processing endoprotease, PC1/PC3.

Amino Acid Sequence↗
PubMed1992

Sequence requirements for precursor cleavage within the constitutive secretory pathway.

We have recently demonstrated that the Arg-X-Lys/Arg-Arg sequence is a signal for precursor cleavage catalyzed by furin, a mammalian homologue of the yeast precursor-processing endoprotease Kex2, within the constitutive secretory pathway. In this study, we further examined sequence requirements for the constitutive precursor cleavage by expression of various prorenin mutants with amino acid substitutions around the native Lys-Arg cleavage site in Chinese hamster ovary cells. The results delineate the following sequence rules that govern the constitutive precursor cleavage. (a) A basic residue (Lys or Arg) at the 4th (position -4) or 6th (position -6) residue upstream of the cleavage site besides basic residues at positions -1 and -2 is necessary. (b) At position -2, a Lys residue is more preferable than Arg. (c) At position -4, an Arg residue is more preferable than Lys. (d) At position 1, a hydrophobic aliphatic amino acid is not suitable.

Amino Acid Sequence↗
PubMed1992

Effect of p-chloromercuribenzoate on Clostridium perfringens beta toxin.

p-Chloromercuribenzoate (PCMB) was shown to bind to Clostridium perfringens beta toxin. Treatment of the toxin with N-ethylmaleimide (NEM), 5,5'-dithio-bis(2-nitro-benzoic acid) (DTNB), o-iodosobenzoate (OIBA) and metal ions such as Cu2+ and Ag+ decreased the lethal activity, but PCMB did not affect the lethal activity. On the other hand, the binding of PCMB to the toxin was inhibited by DTNB and NEM in a dose-dependent manner. Furthermore, the lethal activity of beta toxin pretreated with PCMB was not blocked by treatment with NEM, DTNB, OIBA, Cu2+ and Ag+. However, the PCMB-treated toxin treated with reduced glutathione, dithiothreitol, 2-mercaptoethanol, liver homogenate or serum from mice was inactivated by NEM.

Animals↗
PubMed1992

Relationship between HOX2 homeobox gene expression and the human cytomegalovirus immediate early genes.

The human embryonal carcinoma cell line NT2/D1 is known to be non-permissive for human cytomegalovirus (HCMV) but becomes permissive after being induced to differentiate by retinoic acid (RA). Because homeobox genes have been reported to be specifically activated in the RA-differentiated NT2/D1 cells, we investigated the possible correlation between expression of homeobox (HOX) 2 genes and expression of the immediate early (IE) genes of HCMV both in NT2/D1 cells and in HCMV permissive human embryonic lung (HEL) cells. HCMV infection did not induce activation of the HOX2A, HOX2E and HOX2I genes in undifferentiated NT2/D1 cells nor affect their activation in the RA-differentiated NT2/D1 cells. By in situ hybridization using a HOX2A RNA probe, HOX2A transcript-positive cells appeared as clusters in RA-differentiated NT2/D1 cells. Viral antigen-positive cells detected by immunofluorescence using an antibody specific for the IE-1 antigen of HCMV appeared as clusters among the population of cells in which the HOX2A transcript was detected. The HOX2A gene only was expressed in HEL cells, however none of the HOX2 genes was expressed in non-permissive HeLa, Raji or mouse embryonic cells. These results suggest that activation of the HOX2A may be necessary for the expression of IE genes. HCMV infection markedly increased the expression of the HOX2E gene in HEL cells in the presence, but not in the absence, of cycloheximide. Ultraviolet-inactivated HCMV also displayed this effect. On the other hand, HCMV infection suppressed expression of the HOX2A gene to some degree at the early and late phases of infection in HEL cells. Activation of the HOX2E gene by HCMV might possibly have a role in virus-induced abnormal embryogenesis.

Animals↗
PubMed1992

Immunohistochemical localization of calmodulin in the human testis [corrected].

The localization of calmodulin in the normal human testis was studied by the indirect immunoperoxidase method. Three different types of fixative were used: phosphate-buffered formalin, Bouin's solution or Carnoy's solution. Immunoreactivity specific for calmodulin was not detectable in the testis fixed in Carnoy's solution. The specimens fixed in phosphate-buffered formalin and in Bouin's solution were stained. The immunostaining for calmodulin was observed in pachytene spermatocytes, secondary spermatocytes and round spermatids but not in spermatogonia, or in pre-leptotene, leptotene and zygotene spermatocytes, elongated spermatids, spermatozoa or Leydig cells. Sertoli cells were not stained or were stained slightly. Among pachytene spermatocytes, the cells at the early stage were barely stained but those at the middle and late stages were slightly and intensely stained, respectively. The present report provides the first confirmation of the localization of calmodulin in the human testis.

Adult↗
PubMed1992

High-affinity binding of Clostridium perfringens epsilon-toxin to rat brain.

125I-epsilon-toxin showed high affinity to rat brain homogenates and synaptosomal membrane fractions, having single binding phases with dissociation constants (Kds) of 2.5 and 3.3 nM, respectively. Treatment of synaptosomal membrane fractions with pronase and neuraminidase lowered the binding of the labeled toxin, whereas treatment with trypsin and phospholipase C did not. Heating of the fractions resulted in a decrease in the binding of the toxin. These data suggest that interaction of epsilon-toxin with cell membranes in the brain is facilitated by a sialoglycoprotein. On the other hand, treatment of the membrane fractions with lipase resulted in complete loss of binding, suggesting that the interaction may require an appropriate lipid environment. These data suggest the presence of specific binding sites in brain tissue for epsilon-toxin.

Animals↗
PubMed1991

Enzyme-linked immunosorbent assay for rapid detection of toxins from Clostridium perfringens.

An enzyme-linked immunosorbent assay (ELISA) with antibodies specific to beta, epsilon and iota ib toxins of Clostridium perfringens was developed to detect beta, epsilon and iota ib toxins, respectively. The ELISA was sensitive enough to detect as little as 1.0 ng/ml of purified beta and iota ib toxins and 0.1 ng/ml of purified epsilon toxin. By means of the ELISA method, 192 isolates of C. perfringens from food samples in Japan and Thailand, and 58 isolates from patients suffering from gas gangrene or gastroenteritis were examined. One isolate from food samples in Japan, three from food samples in Thailand and five from stools of patients with gastroenteritis were C. perfringens type D. One type B and one type C were detected from the stools of patients with gastroenteritis.

ADP Ribose Transferases↗
PubMed1991

Arg-X-Lys/Arg-Arg motif as a signal for precursor cleavage catalyzed by furin within the constitutive secretory pathway.

Many peptide hormones are produced from larger precursors by endoproteolysis at pairs of basic amino acids (e.g. Lys-Arg and Arg-Arg) within the regulated secretory pathway in endocrine cells. However, many other secretory and membrane proteins appear to be produced from precursors through cleavage at multiple, rather than paired, basic residues within the constitutive secretory pathway in non-endocrine cells. By surveying various precursors processed constitutively, we noticed that most of them have the consensus sequence, Arg-X-Lys/Arg-Arg (RXK/RR), at the cleavage site. When expressed in endocrine and non-endocrine cells, a precursor with the RXKR sequence was cleaved in both types of cells, whereas that with the Lys-Arg pair was cleaved only in the endocrine cells. When the RXKR precursor was coexpressed with furin and PC3, both of which are mammalian homologues of the yeast precursor-processing endoprotease Kex2, in non-endocrine cells, enhancement of the precursor cleavage by furin but not by PC3 was observed. By contrast, when the Lys-Arg precursor was coexpressed with the two mammalian proteases in endocrine cells with no endogenous processing activity at dibasic sites, it was cleaved only by PC3. These results indicate that the basic pair and the RXK/RR sequence are the signals for precursor cleavages catalyzed by PC3 within the regulated secretory pathway and by furin within the constitutive pathway, respectively.

Amino Acid Sequence↗
PubMed1991

Sequence requirements for prohormone processing in mouse pituitary AtT-20 cells. Analysis using prorenins as model substrates.

Although cleavage of peptides at sites marked by paired basic amino acids is a common feature of prohormone processing, little is known about the properties of endoprotease(s) responsible for cleavage of the precursor. To examine the cleavage specificity of a processing endoprotease, we have altered the Lys-Arg cleavage site of human prorenin to Arg-Arg, Lys-Lys and Arg-Lys by site-directed mutagenesis, and expressed the native and mutated precursors in mouse pituitary AtT-20 cells which are known to process foreign prohormones, including prorenin, at paired basic sites during the regulated secretory process. All native and mutated human prorenins were sorted into the regulated secretory pathway. The mutated precursor with Arg-Arg instead of the Lys-Arg native pair was processed at about half the efficiency of the native one, while the Lys-Lys and Arg-Lys mutants were not processed. Rat prorenin, which naturally has a Lys-Lys pair, was not processed in the cells. In addition, mouse Ren2 prorenin, which has a Ser residue next to the Lys-Arg pair, but not mouse Ren1 prorenin, which has a Pro residue next to the pair, was processed. These results suggest that the Arg residue at the COOH side of the basic pair is essential for cleavage of prorenins by a processing enzyme during the regulated secretory process in AtT-20 cells, although the NH2-side Lys residue also plays a role. The results also demonstrate that the processing enzyme cannot cleave the Arg-Pro peptide bond.

Amino Acid Sequence↗
PubMed1991

Postnatal porencephaly induced in mouse by murine cytomegalovirus.

Mouse embryos were infected with murine cytomegalovirus (MCMV) by injecting the virus into the cerebral ventricles at the late gestation. After deliveries, offspring were fed by the mothers until 4 weeks. Cystic brain lesions, regarded as porencephaly or paraventricular cysts, were observed in about 20% of the MCMV-injected offspring 3 to 4 weeks after birth. The porencephaly involved the cerebral cortex and the white matter, and sometimes opened to the ventricles, while the paraventricular cysts involved the white matter. The inner surfaces of the cysts were covered with thin monolayer cells. Around the cystic lesions, perivascular cuffings were sometimes observed in the meninges and the basal regions. Viral antigen-positive cells were observed in the cortex and the hippocampus but were hardly observed along the cystic walls. Immunohistochemical double staining using antibodies specific for the viral antigen and specific for factor VIII-related antigen showed that the brain capillary endothelial cells had susceptibility to MCMV infection, and in addition that some neurons in the cortex and the hippocampus had the same susceptibility. These findings suggest that there are at least two ways by which MCMV induce abnormalities in the developing mouse brains; migration of MCMV-infected neurons and affinity to the endothelial cells of the brain vessels to this virus.

Animals↗
PubMed1991

Distribution of labeled Clostridium perfringens epsilon toxin in mice.

The in vivo distribution of labeled Clostridium perfringens epsilon toxin after i.v. administration to mice was investigated. High amounts of radioactivity were found in the kidneys and the brain, and small amounts were in the heart, lungs, liver and stomach. On the other hand, the prior administration of epsilon prototoxin resulted in significant inhibition of the uptake of the radioactivity in the brain, but no effect in the other organs tested. The labeled prototoxin or toxin was dose-dependently accumulated in the brain after i.v. injection. However, the prototoxin inhibited the uptake of the toxin injected within 10 min after the administration of the prototoxin. The prototoxin also inhibited the uptake of labeled bovine serum albumin caused by the toxin in the brain. In the present paper, these data show that the toxin is specifically bound to the brain of mice.

Animals↗
PubMed1991

Evidence that differentiates between precursor cleavages at dibasic and Arg-X-Lys/Arg-Arg sites.

It is well known that precursor cleavage at paired basic amino acids (e.g., Lys-Arg, Arg-Arg) within the regulated secretory pathway is one of the key steps to produce bioactive peptides. On the other hand, we have recently shown that precursors with an Arg residue at the fourth residue upstream of the cleavage site besides the basic pair, i.e. with the Arg-X-Lys/Arg-Arg (RXK/RR) motif, are cleaved within the constitutive secretory pathway. To discriminate between the precursor cleavage at RXK/RR sites within the constitutive pathway and that at dibasic sites within the regulated pathway, we examined the effects of drugs affecting the secretory process, intracellular Ca2+ depletion, and a protease inhibitor on these cleavages. Chloroquine (a weak base), depletion of intracellular Ca2+ by A23187 (a Ca2+ ionophore), and the Pittsburgh-type mutant of alpha 1-protease inhibitor differentially affected these two cleavages. Brefeldin A, which impedes protein transport from the endoplasmic reticulum to the Golgi complex, inhibited both cleavages. Colchicine (an anti-microtubular drug) had no discernible effect on either cleavage. These observations support the notion that the precursor cleavages at dibasic and RXK/RR sites occur in different subcellular compartments, and are catalyzed by different processing endoproteases.

Amino Acid Sequence↗
PubMed1991

Viral DNA detected by in situ hybridization in the developing mouse brain infected with murine cytomegalovirus.

To investigate the pathogenesis of brain abnormalities caused by congenital cytomegalovirus (CMV) infection, we previously reported experimental murine models of brain damage induced by intraventricular injection of murine CMV (MCMV) at the late stage of gestation. In the present study, viral DNA-positive cells in the damaged brain at different postnatal stages detected by in situ hybridization were compared with viral antigen-positive cells detected by an immunoperoxidase method using a monoclonal antibody against the immediate early antigen. At birth, the number of viral DNA-positive cells almost equalled that of viral antigen-positive cells. Seven to ten days after birth, the number of viral DNA-positive cells in the brain of MCMV-injected mice was one-fifth that of viral antigen-positive cells. Viral DNA-positive cells were more numerous in the hippocampus than in the cortex, and their density was dependent on the presence of viral antigen-positive cells. Dotted reaction products were observed in the nuclei of viral DNA-positive cells. These cells were rarely detected in lesions of later stages such as atrophy of the cortex and hippocampus, or the wall of the cystic lesions. These results suggest that viral DNA-positive cells detected by in situ hybridization are infected cells in which viral DNA replication is occurring actively.

Animals↗
PubMed1991

Effect of glucose and an aldose reductase inhibitor on myo-inositol uptake by cultured human endothelial cells.

The effects of an aldose reductase (AR) inhibitor, elevated glucose and other compounds were evaluated on in vitro 2-[3H] myo-inositol (MI) uptake in cultured human endothelial cells (ECs). Significant AR activity was present in ECs (1,373 +/- 170 mumol/mg.min: incubated with 28 mM glucose for 48 hr). Since Na(+)-deprivation and the addition of Ouabain (5 mM) significantly reduced MI uptake, MI incorporation into ECs might be dependent on an active transport system via Na(+)-K+ ATPase activity. MI uptake was reduced significantly (21 +/- 6, 39 +/- 7% reduction) in the presence of excess glucose (27.5, 55 mM). However, addition of the AR inhibitor (ONO-2235 100 microM) prevented the glucose mediated inhibition of MI uptake (15 +/- 5, 21 +/- 6% reduction). These results suggest that inhibition of AR might prevent glucose-mediated toxicity via an increment of MI uptake.

Aldehyde Reductase↗