Chemotactic adaptation is altered by changes in the carboxy-terminal sequence conserved among the major methyl-accepting chemoreceptors

In Escherichia coli and Salmonella typhimurium, methylation and demethylation of receptors are responsible for chemotactic adaptation and are catalyzed by the methyltransferase CheR and the methylesterase CheB, respectively. Among the chemoreceptors of these species, Tsr, Tar, and Tcp have a well-conserved carboxy-terminal motif (NWET/SF) that is absent in Trg and Tap. When they are expressed as sole chemoreceptors, Tsr, Tar, and Tcp support good adaptation, but Trg and Tap are poorly methylated and supported only weak adaptation. It was recently discovered that CheR binds to the NWETF sequence of Tsr in vitro. To examine the physiological significance of this binding, we characterized mutant receptors in which this pentapeptide sequence was altered. C-terminally-mutated Tar and Tcp expressed in a receptorless E. coli strain mediated responses to aspartate and citrate, respectively, but their adaptation abilities were severely impaired. Their expression levels and attractant-sensing abilities were similar to those of the wild-type receptors, but the methylation levels of the mutant receptors increased only slightly upon addition of attractants. When CheR was overproduced, both the adaptation and methylation profiles of the mutant Tar receptor became comparable to those of wild-type Tar. Furthermore, overproduction of CheR also enhanced adaptive methylation of wild-type Trg, which lacks the NWETF sequence, in the absence of any other chemoreceptor. These results suggest that the pentapeptide sequence facilitates effective adaptation and methylation by recruiting CheR.

Increased induction of apoptosis by a Sendai virus mutant is associated with attenuation of mouse pathogenicity

An avirulent mutant of Sendai virus, Ohita-MVC11 (MVC11), was generated from a highly virulent field strain, Ohita-M1 (M1), through successive passages in LLC-MK2 cell cultures (M. Itoh, Y. Isegawa, H. Hotta, and M. Homma, J. Gen. Virol. 78:3207-3215, 1997). In LLC-MK2 cells, MVC11 induced a high degree of apoptotic cell death that was demonstrated by chromatin condensation of the nucleus and DNA fragmentation, and production of MVC11 declined markedly after prolonged culture. On the other hand, M1 did not induce prominent apoptosis and maintained high virus titers. In primary mouse pulmonary epithelial cell cultures, M1 replicated rather slowly to reach maximum level of virus production at 3 days postinfection, and high levels of virus production were maintained thereafter without causing apoptosis. In contrast, MVC11, which produced 20 times more progeny virus than M1 at 1 day postinfection, induced a high degree of apoptotic cell death before the virus replication cycle was completed. Accordingly, the production of progeny virus was strongly inhibited thereafter. In the lungs of mice infected with MVC11, virus antigens and signals of DNA fragmentation detected by the in situ terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling technique colocalized in bronchial epithelial cells, clearly demonstrating that infection by MVC11 triggered apoptosis in vivo as well as in vitro. These results suggest the possibility that induction of apoptosis by MVC11 plays an important role in attenuation of mouse pathogenicity by restricting progeny virus production in the lung. The C protein was shown to have the capacity to induce apoptosis, and the increased level of the C protein in MVC11-infected cells was considered to account partly, if not entirely, for the induction of apoptosis.

Detection of measles virus mRNA from autopsied human tissues

By reverse transcription-PCR, measles virus (MV) mRNA was detected in the brain, kidney, spleen, liver, and lung tissues obtained from 23 (45.1%) of 51 autopsy subjects, with the detection rates of each tissue ranging from 8 to 20%. Sequence analysis revealed frequent mutations in the corresponding viral protein. These results suggest that MV mutants commonly persist in apparently healthy individuals.

Isolation of an avirulent mutant of Sendai virus with two amino acid mutations from a highly virulent field strain through adaptation to LLC-MK2 cells

A field strain of Sendai virus (SeV) Ohita-M1 (M1) was isolated from an epidemic in an animal laboratory by passaging in mice. A mutant strain, Ohita-MVC11 (MVC11), was then obtained by passaging M1 in rhesus monkey (LLC-MK2) cells. MVC11 was adapted to LLC-MK2 cells and produced 20 times higher levels of infectious virus than M1. This increased production of infectious virus in LLC-MK2 cells was associated with enhanced viral gene expression. However, MVC11 could not replicate efficiently in mouse lung and was not lethal to mice even when inoculated at a titre of 8 x 10(5) cell-infecting units (CIU) per mouse. On the other hand, with an inoculum of only 4 x 10(1) CIU per mouse, corresponding to 1 LD50, M1 replicated well in mouse lung and was highly virulent to mice. Nucleotide and deduced amino acid sequence analyses of the entire genomes of M1 and MVC11 revealed that adaptation to LLC-MK2 cells and the attenuation of mouse pathogenicity of MVC11 were associated with only two amino acid substitutions; one on the C protein (Phe substituted by Ser at position 170) and the other on the RNA polymerase, the L protein (Glu substituted by Ala at position 2050).

Thermosensing properties of mutant aspartate chemoreceptors with methyl-accepting sites replaced singly or multiply by alanine

The aspartate chemoreceptor Tar has a thermosensing function that is modulated by covalent modification of its four methylation sites (Gln295, Glu302, Gln309, and Glu491). Without posttranslational deamidation, Tar has no thermosensing ability. When Gln295 and Gln309 are deamidated to Glu, the unmethylated and heavily methylated forms function as warm and cold sensors, respectively. In this study, we carried out alanine-scanning mutagenesis of the methylation sites. Although alanine substitutions influenced the signaling bias and the methylation level, all of the mutants retained aspartate-sensing function. Those with single substitutions had almost normal thermosensing properties, indicating that substitutions at any particular methylation site do not seriously impair thermosensing function. In the posttranslational modification-defective background, some of the alanine substitutions restored thermosensing ability. Warm sensors were found among mutants retaining two glutamate residues, and cold sensors were found among those with one or no glutamate residue. This result suggests that the negative charge at the methylation sites is one factor that determines thermosensor phenotypes, although the size and shape of the side chain may also be important. The warm, cold, and null thermosensor phenotypes were clearly differentiated, and no intermediate phenotypes were found. Thus, the different thermosensing phenotypes that result from covalent modification of the methylation sites may reflect distinct structural states. Broader implications for the thermosensing mechanism are also discussed.

Cloning of a Vibrio alginolyticus rpoN gene that is required for polar flagellar formation

A fragment of DNA was cloned which complemented a polar flagellum-defective (pof) mutation of Vibrio alginolyticus. The fragment contained two complete and two partial open reading frames (ORFs) (ORF2 and -3 and ORF1 and -4, respectively). The presumed product of ORF2 has an amino acid sequence with a high degree of similarity to that of RpoN, which is an alternative sigma factor (sigma54) for other microorganisms. The other ORFs are also homologous to the genes adjacent to other rpoN genes. Deletion analysis suggests that ORF2 complements the pof mutation. These results demonstrate that RpoN is involved in the expression of polar flagellar genes.

Molecular epidemiology and changing distribution of genotypes of measles virus field strains in Japan

Based on phylogenetic and restriction fragment length polymorphism analyses of the hemagglutinin and nucleoprotein gene sequences, measles virus strains obtained in western Japan were divided into two types. Type 1 isolates have largely replaced type 2 isolates during the last 10 years in the area surveyed.

[Cerebral infarction due to stenosis of the bilateral internal carotid artery in Turner's syndrome]

A 43-year-old woman was admitted into our hospital because of aphasia and right hemiparesis. Computed tomographic scan demonstrated border zone infarction in the anterior and middle cerebral artery. Magnetic resonance imaging scans showed the borderline area between the terminal branches of the lenticulostriate arteries and the perforating branches of the middle cerebral artery. Digital subtraction ICA angiogram showed severe narrowing of the distal portion of the right and left ICA. A pattern analysis of ambulatory blood pressure monitoring (ABPM) was carried out in this patient, and it was showed "dipper type". Laboratory data was elevated excretion of pituitary gonadotropines and low estrogen excretion. Chromosome analysis revealed the 45, X/46, XX. She was diagnosed with mosaic type of Turner's syndrome. The cerebrovascular abnormality might be due to congenital hypoplasia of arteries, and declining of blood pressure during sleep was possible significant factors in the pathogenesis of cerebral infarction in this patient.

Defective de novo thymocyte maturation in cyclosporin A (CsA)-induced autoimmunity: expression of costimulatory and activation molecules

Lethally x-irradiated Lewis rats, reconstituted with syngeneic bone marrow and transiently treated with CsA for 4 weeks, will develop an autoimmune disease about 2-3 weeks after cessation of CsA therapy. CsA-induced autoimmunity is a thymus-dependent and T cell-mediated autoimmune disease. CsA is thought to generate autoreactive T cells by interference with negative selection in the thymus; x-irradiation is required to eliminate the peripheral autoregulatory T cell circuit. In this study we re-evaluate the effect of CsA on thymic atrophy and thymocyte maturation. Subsequently we examine the expression of costimulatory and activation molecules (CD2, CD5, CD11a, CD11b, CD25, CD28, CD43, CD54, OX-40, RT-1A, RT-1B and RT-1D) during distinct maturational stages in order to detect possible clues to the observed effects of CsA on thymocyte maturation and selection. The results revealed that CsA blocks maturation of double-positive TCR(int) to double-positive TCR(high) thymocytes and preferentially inhibits the development of mature CD4 single-positive thymocytes. Furthermore, CsA administration resulted in a reduced expression of the costimulatory CD2 molecule. Although it is a matter of debate whether this defective CD2 expression is involved in the aberrant maturation and selection of thymocytes, it is speculated that reduced costimulation via CD2 may influence differentiation into distinct T cell subsets.

[Phospholipase C inhibitor]

N-Myristoylated PCI peptide, myr-PCI, originally developed based on the PCI sequence of PLC- gamma 2, inhibited activity of purified PLC isoforms in vitro, and external stimuli-dependent IP3 formation in Swiss 3T3 cells. When myr-PCI was added to KMS-8 cells, derived from familial adenomatous polyposis patients, it also suppressed the serum-dependent IP3 formation, DNA synthesis, and cell growth. In order to develop PCI peptides with strong anti-PLC activity, we synthesized the peptides whose N- and/or C-termini were acylated by a variety of compounds, and examined their anti-PLC and anti-proliferative activities. Results would be quite helpful to determine the minimal structure required for PLC inhibition in vivo.

Extrashot-ODS, a syringe-type minicolumn sample injector for a reversed-phase high-performance liquid chromatographic column. Application to antiepileptics in human sera

Extrashot-ODS (EXS-ODS) is a syringe-type minicolumn developed for sample injection into reversed-phase high-performance liquid chromatographic columns. EXS-ODS consists of (a) a stainless-steel needle fitted to an ordinary syringe-loading sample injector for HPLC, (b) a 45-microl minicolumn tube made of polytetrafluoroethylene (PTFE) and packed with ODS-silica and (c) a minicolumn holder made of polystyrene, which is connected to the needle on one side and the other side is shaped so as to be fitted with a solvent syringe. Using the device, we simultaneously analyzed three antiepileptics in 20 microl of human sera. First, we introduced a 20-microl serum specimen diluted with 100 microl of buffer solution into the device and, second, 100 microl of distilled water. Then the device was attached to the HPLC injector and 130 microl of methanol were introduced into the HPLC column through the device. Then, reversed-phase HPLC was conducted in the usual manner, with the chromatogram reading at a wavelength of 210 nm for the assays of 5,5-diphenylhydantoin, phenobarbital and carbamazepine. The results obtained by direct peak-height calibration were comparable to those given by the immunological method.

Pharmacokinetics and safety of the novel amino-3-hydroxy-5-methylisoxazole-4-propionate receptor antagonist YM90K in healthy men

YM90K is a novel, selective and competitive alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate receptor antagonist with neuroprotective properties, and it is currently under development for the intravenous treatment of stroke and other conditions of acute neuronal degeneration. The safety and pharmacokinetics of YM90K in healthy men was investigated after single doses up to 36 mg and repeated doses of 24 mg given by intravenous infusion over 3 hours. YM90K was well tolerated in healthy men and induced only mild changes in kidney function markers. Unchanged plasma drug concentration reached a near steady state during 3-hour infusion and rapidly decreased in a biphasic manner after the completion of infusion. YM90K showed linear pharmacokinetics. In the repeated-dose study, no significant differences were observed in pharmacokinetics of YM90K between the first and fifth dose. Unchanged urinary drug excretion was as high as 63.2% to 78.3% of the dose, most of which was excreted within 1 hour after the completion of infusion. YM90K is thought to be excreted mainly by renal tubular secretion. YM90K showed neither significant adverse reactions nor severe abnormalities in physical and laboratory examinations of the study participants and demonstrated safety and pharmacokinetic profiles compatible with clinical use.

Putative channel components for the fast-rotating sodium-driven flagellar motor of a marine bacterium

The polar flagellum of Vibrio alginolyticus rotates remarkably fast (up to 1,700 revolutions per second) by using a motor driven by sodium ions. Two genes, motX and motY, for the sodium-driven flagellar motor have been identified in marine bacteria, Vibrio parahaemolyticus and V. alginolyticus. They have no similarity to the genes for proton-driven motors, motA and motB, whose products constitute a proton channel. MotX was proposed to be a component of a sodium channel. Here we identified additional sodium motor genes, pomA and pomB, in V. alginolyticus. Unexpectedly, PomA and PomB have similarities to MotA and MotB, respectively, especially in the predicted transmembrane regions. These results suggest that PomA and PomB may be sodium-conducting channel components of the sodium-driven motor and that the motor part consists of the products of at least four genes, pomA, pomB, motX, and motY. Furthermore, swimming speed was controlled by the expression level of the pomA gene, suggesting that newly synthesized PomA proteins, which are components of a force-generating unit, were successively integrated into the defective motor complexes. These findings imply that Na+-driven flagellar motors may have similar structure and function as proton-driven motors, but with some interesting differences as well, and it is possible to compare and study the coupling mechanisms of the sodium and proton ion flux for the force generation.

Uncoupling of ligand-binding affinity of the bacterial serine chemoreceptor from methylation- and temperature-modulated signaling states

The Escherichia coli chemoreceptor Tsr mediates tactic responses to serine, repellents, and changes in temperature. We have previously shown that the serine-sensing ability of Tsr-T156C, which has a unique cysteine in place of threonine at residue 156, is specifically inactivated by thiol-modifying reagents and that L-serine protects the receptor from modification. In this study, we demonstrated the correlation between protective effects of various attractants and their potencies to elicit attractant responses. This indirect binding assay was used to monitor the affinity of the receptor for L-serine under various conditions. It has been demonstrated by in vitro assays that the ligand-binding affinities of Tsr and the related chemoreceptor Tar are unaffected by changes in the methylation state of the receptor. Using the serine protection assay, we re-examined this issue both in vitro and in vivo. The methylation levels of Tsr-T156C did not affect its ligand-binding affinity. We also showed both in vitro and in vivo that the ligand-binding affinity was unaffected by temperature. These results suggest that the structure of the periplasmic domain of the receptor is uncoupled from the signaling states of the cytoplasmic domain. This ligand-binding assay system should be applicable to other receptors.

Chromatographic identification of phenolic compounds in human urine following oral administration of the herbal medicines Daisaiko-to and Shosaiko-to

Chemical identification of the compounds in human urine following administration of the traditional Chinese medicines, Daisaiko-to and Shosaiko-to (Dachaihu-tang and Xiaochaihu-tang in Chinese, respectively), was achieved by using a linear relationship between the logarithm of the capacity factor, log k', and that of the volume fraction of CH3CN, log X(s)(vol), in the aqueous mobile phase: -log k'=A+B log X(s)(vol). Comparison of the slope, B, and the intercept, A, between the urinary compound and its suspected authentic specimen gave satisfactory results in the chemical identification. We applied this method to the initial stage of pharmacokinetic studies on the herbal medicines and identified seven flavonoids and two anthraquinone derivatives in the urine specimens obtained after herbal administration.

Systematic analysis of post-administrative saiboku-to urine by liquid chromatography to determine pharmacokinetics of traditional Chinese medicine

To disclose the mystery of a traditional Chinese medicine and to identify biologically active components, we analysed post-administrative urine for Saiboku-To, an anti-asthmatic Chinese herbal remedy. Systematic analysis of the components appearing in the urine was carried out by high-performance liquid chromatography (HPLC) with normal- and reversed-phase modes in combination. beta-D-glucuronidase-treated urine was subjected to rapid-flow fractionation (RFF) to achieve fractional extraction of lipophilic components with exhaustive recovery rates. The extracts were analysed by HPLC equipped with a multi-channel UV-detector. In the first stage of HPLC, we conducted a normal-phase mode run to find magnolol derived from Magnolia officinalis, as the most hydrophobic component showing minimum retention time among the urinary products of Saiboku-To. In the next stage, mobile phase solvent composition for reversed-phase HPLC was optimized so as to retain magnolol up to 60 min. Under these conditions, other Saiboku-To urinary products, which were more polar than magnolol, appeared within 60 min. Our HPLC method used marker compounds like magnolol and could indicate the terminal peak position on the reversed-phase chromatography. We found a total of eight components in the post-administrative Saiboku-To urine. Structure identification of the isolated pure materials was achieved using nuclear magnetic resonance (NMR)-, mass (MS)- and UV-spectra, and HPLC retention profiles. They were magnolol and 8,9-dihydroxydihydromagnolol stemming from M. officinalis, medicarpin and liquiritigenin from Glycyrrhiza glabra, baicalein, wogonin, and oroxylin A from Scutellaria baicalensis, and davidigenin of an unknown origin. The pharmacological mystery of Saiboku-To should be disclosed by resolving the pharmacokinetics and pharmacodynamics of these urinary products independently and synergistically.

Coexistence of serum anti-DNA topoisomerase I and anti-Sm antibodies: report of 3 cases

We describe 3 Japanese patients having both serum anti-DNA topoisomerase I and anti-Sm antibodies. All 3 patients had typical features of systemic lupus erythematosus, such as glomerulonephritis, in addition to skin thickening and systemic sclerosis related organ involvement, including pulmonary interstitial fibrosis and renal crisis. This is the first report of the coexistence of these 2 disease specific autoantibodies.

Vibrio alginolyticus mutants resistant to phenamil, a specific inhibitor of the sodium-driven flagellar motor

The polar flagella of Vibrio alginolyticus are driven by sodium motive force and those motors are specifically and strongly inhibited by phenamil, an amiloride analog that is thought to interact with a sodium channel of the flagellar motor. To study the sodium ion coupling site, we isolated motility mutants resistant to phenamil and named the phenotype Mpa(r) for motility resistant to phenamil. The motility of the wild-type (Mpa(s)) was inhibited by 50 microM phenamil, whereas Mpa(r) strains were still motile in the presence of 200 microM phenamil. The Ki value for phenamil in the Mpa(r) strain was estimated to be five times larger than that in the Mpa(s) strain. However, the sensitivities to amiloride or benzamil, another amiloride analog, were not distinctly changed in the Mpa(r) strain. The rotation rate of the wild-type Na+-driven motor fluctuates greatly in the presence of phenamil, which can be explained in terms of a relatively slow dissociation rate of phenamil from the motor. We therefore studied the stability of the rotation of the Mpa(r) and Mpa(s) motors by phenamil. The speed fluctuations of the Mpa(r) motors were distinctly reduced relative to the Mpas motors. The steadier rotation of the Mpa(r) motors can be explained by an increase in the phenamil dissociation rate from a sodium channel of the motor, which suggests that a phenamil-specific binding site of the motor is mutated in the Mpa(r) strain.

[Effect of phospholipase C inhibitor peptides on cancer cell growth]

We analyzed the effect of PLC inhibitor (PCI) peptides in their growth and cell cycle. N-Myristoylated PCI peptide, myr-PCI, originally developed based on the PCI sequence of PLC-gamma 2, inhibited activity of purified PLC isoforms in vitro. When myr-PCI was added to KMS-4 and KMS-8 cells, both derived from familial adenomatous polyposis patients, it suppressed the production of inositol trisphosphate, DNA synthesis, and cell growth, all of which were induced by serum in both KMS 4 and KMS 8 cells. Flow cytometry analysis with propidium iodide labelling revealed marked decreases in the percentage of KMS 8 cells in S phase and increases in G0, G1 by the addition of myr PCI. These results indicate that the activation of PLC is essential for growth and transformed properties of these colorectal carcinoma cells, and also that PLC inhibitors could be an anti-tumor drug for some cases.

Signaling by the Escherichia coli aspartate chemoreceptor Tar with a single cytoplasmic domain per dimer

Many transmembrane receptors are oligomeric proteins. Binding of a ligand may alter the oligomeric state of the receptor, induce structural changes within the oligomer, or both. The bacterial aspartate chemoreceptor Tar forms a homodimer in the presence or absence of ligands. Tar mediates attractant and repellent responses by modulating the activity of the cytoplasmic kinase CheA. In vivo intersubunit suppression was used to show that certain combinations of full-length and truncated mutant Tar proteins complemented each other to restore attractant responses to aspartate. These results suggest that heterodimers with only one intact cytoplasmic domain are functional. The signaling mechanism may require interactions between dimers or conformational changes within a single cytoplasmic domain.