Total Solution Synthesis of Human Epidermal Growth Factor (h-EGF) by the Assembly of Nine Building Blocks

Human epidermal growth factor (h-EGF) composed of 53 amino acids bearing three intramolecular disulfide bridges was synthesized by the maximum protecting solution method. The synthetic h-EGF coincided with recombinant h-EGF by reverse-phase HPLC, and the sites of three intramolecular disulfide bridges were ascertained by a thermolytic digestion. The synthetic h-EGF possessed m/z 6215.7 in its FAB-MS as expected, and exhibited compatible mitogenic activity.

Elucidation of structural requirements of mastoparan for mast cell activation-toward the comprehensive prediction of cryptides acting on mast cells

Mastoparan, a toxic peptide from wasp venom, induces various biological functions including histamine release from rat peritoneal mast cells. Here we report that, for the activation of mast cells by mastoparan, at least two positively charged side chains are required on the hydrophilic side of the amphiphilic structure of the peptide. The present results are expected to be utilized for the bioinformatic and comprehensive identification of endogenous mast cell-stimulating cryptides.

Antibacterial Activity and Clinical Efficacy of Sparfloxacin in Mycobacterium avium-intracellulare Complex Infection

In Japan the incidence of atypical mycobacteriosis has steadily increased, with Mycobacterium avium-intracellulare complex (MAC) the most common infecting organism. A standard chemotherapy regimen for MAC infection has not been established because of significant resistance to anti-mycobacterial drugs. Sparfloxacin has good antimicrobial activity against several acid-fast bacteria and is expected to be an effective drug for treating mycobacteriosis. We examined the effects of adding sparfloxacin to anti-tuberculotic combination therapy in six patients with MAC pulmonary disease. Drug susceptibility was also assessed using the agar dilution method. The minimum inhibitory concentrations (MICs) for sparfloxacin, levofloxacin, isoniazid, rifampicin, streptomycin, ethambutol and clarithromycin was measured in clinical isolates from all patients; sparfloxacin showed the lowest MIC. Bacteriological and clinical improvements were observed in the four patients who completed the study. Dosing was discontinued in two patients because of pruritic skin eruptions. Sparfloxacin shows promise as an anti-mycobacterial agent for treating MAC pulmonary disease.

Transcriptional regulation of interferon gamma gene by p300 co-activator

Interferon gamma (IFN gamma) is an important immunoreguratory protein and is secreted from CD4+, CD8+ T cells and NK cells. Expression of IFN gamma gene is regulated by either DNA-methylation or cis-elements of transcriptional factors such as AP-1, NFAT, AP-4, YY-1, ATF and GATA. At a putative ATF binding site in a promoter region of IFN gamma gene, the position from -59 to -43, is important for the IFN gamma promoter activity. Our gel-shift competition studies demonstrated that addition of antibodies against ATF-2 caused super-shifts of DNA-protein complexes. In addition, it was clarified that p300 was involved in DNA-protein complexes by in vitro "pull-down" experiments. Moreover, a co-expression of p300 and ATF-2 enhanced the promoter activity of IFN gamma gene. Thus, these results indicate that p300 and ATF-2 play critical rules in a basal transcription of IFN gamma gene in Jurkat T cells.

Recognition of engineered tRNAs with an extended 3' end by Exportin-t (Xpo-t) and transport of tRNA-attached ribozymes to the cytoplasm in somatic cells

Our recent analysis indicates that the cytoplasmic localization of tRNA-attached ribozymes (tRNA-Rz) is critical for its high-level intracellular activity, suggesting that mature mRNAs in the cytoplasm are more accessible to ribozymes than pre-mRNAs in the nucleus (Kato et al. J. Biol. Chem. 2001, 276, 15378-15385; Kuwabara et al. Nucleic Acids Res. 2001, 29, 2780-2788). Although studies in Xenopus oocytes led to the proposal that only correctly processed mature tRNAs are exported from nuclei in a RanGTP-dependent manner (Lund and Dahlberg Science 1998, 282, 2082-2085), our tRNA-Rz with an extended 3' end can also be exported to the cytoplasm in somatic cells. Xpo-t/RanGTP bound to tRNA-attached ribozymes in vitro and in somatic cells, with recognition basically resembling the recognition of mature tRNAs. In contrast, no binding to tRNA-attached ribozymes occurred in Xenopus oocytes. The injection of a nuclear extract of Xenopus oocytes together with tRNA-attached ribozymes inhibited the export of tRNA-attached ribozymes but not mature tRNAs in somatic cells, suggesting the existence of an inhibitor(s) of the Xpo-t-dependent export pathway. Moreover, the inhibitor(s) appears responsible for a proofreading mechanism that operates in oocytes.

[Clinical utility and safety of diagnostic thoracoscopy]

The increasing use of thoracoscopy performed under local anesthesia has made contributions to the diagnosis of pleural disease with effusion. During the past 7 years, we have performed 100 such thoracoscopy procedures using a flexible fiberoptic bronchoscope. On the basis of our clinical findings, we are able to discuss the utility and safety of this procedure. The causes of pleural effusion were carcinomatous pleurisy in 72 cases, tuberculosis pleurisy in 15 cases, infection without tuberculosis in 4 cases, malignant pleural mesothelioma in 8 cases and one case of asbestosis. The success rate of thoracoscopic pleural biopsies were 97% for carcinomatous pleurisy, 100% for malignant pleural mesothelioma and 86% for tuberculosis pleurisy. This procedure was performed with no serious effect on blood pressure, oxygen saturation, monitored ECG or BGA data, and with no serious complications. Therefore, we concluded that this method is very useful for the diagnosis of pleural effusions and has few complications.

Chemo-enzymatic synthesis of a bioactive peptide containing a glutamine-linked oligosaccharide and its characterization

A bioactive peptide containing a glutamine-linked oligosaccharide was chemo-enzymatically synthesized by use of the solid-phase method of peptide synthesis and the transglycosylation activity of endo-beta-N-acetylglucosaminidase. Substance P, a neuropeptide, is an undecapeptide containing two L-glutamine residues. A substance P derivative with an N-acetyl-D-glucosamine residue attached to the fifth or sixth L-glutamine residue from the N-terminal region was chemically synthesized. A sialo complex-type oligosaccharide derived from a glycopeptide of hen egg yolk was added to the N-acetyl-D-glucosamine moiety of the substance P derivative using the transglycosylation activity of endo-beta-N-acetylglucosaminidase from Mucor hiemalis, and a substance P derivative with a sialo complex-type oligosaccharide attached to the L-glutamine residue was synthesized. This glycosylated substance P was biologically active, although the activity was rather low, and stable against peptidase digestion. The oligosaccharide moiety attached to the L-glutamine residue of the peptide was not liberated by peptide-N(4)-(N-acetyl-beta-D-glucosaminyl) asparagine amidase F.

Cell-cycle dependent tyrosine phosphorylation on mortalin regulates its interaction with fibroblast growth factor-1

We previously reported that endogenously expressed, intracellularly localized fibroblast growth factor (FGF)-1 interacts with mortalin. Here we report that FGF-1 added to the culture medium of quiescent BALB/c3T3 cells is taken up by the cells and interacts with mortalin in the cells in a regulated manner. Although both the internalized FGF-1 and mortalin were present at high levels throughout the FGF-1-initiated cell cycle, their interaction became apparent only in late G1 phase. Interestingly, mortalin was preferentially tyrosine phosphorylated at the same time, and when its normally weak phosphorylation in early G1 phase was augmented by treating the cells with vanadate, a strong interaction between mortalin and FGF-1 was established. Conversely, when phosphorylated mortalin was treated with tyrosine phosphatase, its interaction with FGF-1 was abrogated. These results indicate that FGF-1 taken up by cells preferentially interacts with mortalin in late G1 phase of the cell cycle, and that tyrosine phosphorylation of mortalin regulates this interaction.

Human CENP-H multimers colocalize with CENP-A and CENP-C at active centromere--kinetochore complexes

Centromere and kinetochore proteins have a pivotal role in centromere structure, kinetochore formation and sister chromatid separation. However, the molecular architecture and the precise dynamic function of the centromere-kinetochore complex during mitosis remain poorly understood. Here we report the isolation and characterization of human CENP-H. Confocal microscopic analyses of HeLa cells with anti-human CENP-H-specific antibody demonstrated that CENP-H colocalizes with inner kinetochore plate proteins CENP-A and CENP-C in both interphase and metaphase. CENP-H was present outside centromeric heterochromatin, where CENP-B is localized, and inside the kinetochore corona, where CENP-E is localized during prometaphase. Furthermore, CENP-H was detected at neocentromeres, but not at inactive centromeres in stable dicentric chromosomes. In vitro binding assays of human CENP-H with centromere-kinetochore proteins suggest that the CENP-H binds to itself and MCAK, but not to CENP-A, CENP-B or CENP-C. CENP-H multimers were observed in cells in which both FLAG-tagged CENP-H and hemagglutinin-tagged CENP-H were expressed. These results suggest that CENP-H multimers localize constitutively to the inner kinetochore plate and play an important fundamental role in organization and function of the active human centromere-kinetochore complex.

The expression of Cox17p in rodent tissues and cells

Previous works have reported the isolation of a novel polypeptide from porcine heart. Structural analysis has shown that it is a mammalian homologue of Cox17p, believed essential for the assembly of functional cytochrome c oxidase and delivery of copper ions to the mitochondrion for insertion into the enzyme in yeast. Although the human, mouse and porcine homologs of this small protein have already been cloned or purified, the function of Cox17p in the mammalian system has not yet been elucidated. To investigate the physiological function of Cox17p in mammals, we performed Northern blot analysis using probes containing the mouse and rat sequences obtained by RT-PCR. The hybridization signals were detected in all mouse tissues, but notably intense signals were observed in heart, brain and kidney RNA samples. Some of the neuroendocrine and endocrine cell lines showed higher expression levels than fibroblasts. The highest expression level of Cox17p mRNA in mouse brain was observed in the pituitary sample. While in rat heart, Cox17p mRNA expression was detected from early development, in rat brain, embryonic and postnatal changes in the expression were observed. Immunocytochemical analysis showed that Cox17p immunoreactivity was strong in the pituitary cell line, AtT-20. These findings suggested that Cox17p is not only part of the respiratory chain but also involved in brain and endocrine functions.

Role of side-chains in the cooperative beta-hairpin folding of the short C-terminal fragment derived from streptococcal protein G

A short C-terminal fragment of immunoglobulin-binding domain of streptococcal protein G is known to form nativelike beta-hairpin at physiological conditions. To understand the cooperative folding of the short peptide, eight Ala-substituted mutants of the fragment were investigated with respect to their structural stabilities by analyzing temperature dependence of NMR signals. On comparison of the obtained thermodynamic parameters, we found that the nonpolar residues Tyr45 and Phe52 and the polar residues Asp46 and Thr49 are crucial for the beta-hairpin folding. The results suggest a strong interaction between the nonpolar side chains that participates in a putative hydrophobic cluster and that the polar side chains form a fairly rigid conformation around the loop (46-51). We also investigated the complex formation of the mutants with N-terminal fragment at the variety of temperature to get their thermal unfolding profiles and found that the mutations on the residues Asp46 and Thr49 largely destabilized the complexes, while substitution of Asp47 slightly stabilized the complex. From these results, we deduced that both the hydrophobic cluster formation and the rigidity of the loop (46-51) cooperatively stabilize the beta-hairpin structure of the fragment. These interactions which form a stable beta-hairpin may be the initial structural scaffold which is important in the early folding events of the whole domain.

Thermodynamics of a beta-hairpin structure: evidence for cooperative formation of folding nucleus

To elucidate early nucleation stages in protein folding, multi-probed thermodynamic characterization was applied to the beta-hairpin structural formation of G-peptide, which is a C-terminal fragment of the B1 domain of streptococcal protein G. The segment corresponding to the sequence of G-peptide is believed to act as a nucleus during the folding process of the B1 domain. In spite of the broad thermal transition of G-peptide, nuclear magnetic resonance (NMR) melting measurements combined with our original analytical theory enabled us to obtain the thermodynamic properties of the beta-hairpin formation with considerable accuracy. Additionally, all the thermodynamic properties determined by every NMR probe on both the main-chain and the side-chains were quite similar, and also comparable to the values that were independently determined by calorimetric analysis of G-peptide. These results demonstrate that G-peptide folds cooperatively throughout the molecule. In other words, the formation of the beta-hairpin is interpreted as the fashion of a first-order phase transition between two states without any distinguishable intermediates. This cooperative formation of the short linear peptide consisting of only 16 residues provides insight into not only the first folding events of the B1 domain, but also the general principles of proteins in terms of structural hierarchy, stability and folding mechanism.

Isolation and characterization of Cox17p from porcine heart by determining its survival-promoting activity in NIH3T3 cells

We have found that the gel filtration fraction of porcine heart extract clearly promoted the survival of NIH3T3 fibroblast cells in the serum-free medium condition. A structural analysis showed that the active fraction contained a novel peptide, porcine Cox17p (p-Cox17p), which was recently reported by Chen et al. as dopuin (Z. W. Chen et al., Eur. J. Biochem. 249 (1997) 518-522). Porcine Cox17p/dopuin possesses high sequence homology to the product of human COX17 gene (h-Cox17p). Although Cox17p has been implied to be involved in copper recruitment to mitochondria and in the functional assembly of cytochrome oxidase in yeast, its role in mammalian cells is unknown. In this study, we chemically synthesized p-Cox17p to investigate its biological effects. Refolding experiments of synthesized linear p-Cox17p revealed the existence of mostly one pattern of three intrachain disulfide bridges similar to that of native p-Cox17p, because the main oxidized p-Cox17p was completely co-eluted with the natural product. The addition of heavy metal ions such as copper, zinc and cadmium significantly inhibited the formation of the oxidized form, suggesting that reduced p-Cox17p may interact directly with these metal ions. The reduced and oxidized forms of p-Cox17p were also confirmed to promote the survival of NIH3T3 cells in serum-free medium as observed with the natural product, indicating that Cox17p may be a bioactive peptide.

Characterization of a novel kinetochore protein, CENP-H

Macromolecular centromere-kinetochore complex plays a critical role in sister chromatid separation, but its complete protein composition as well as its precise dynamic function during mitosis has not yet been clearly determined. Here we report the isolation of a novel mouse kinetochore protein, CENP-H. The CENP-H, with an apparent molecular mass of 33 kDa, was found to contain a coiled-coil structure and a nuclear localization signal. The CENP-H transcripts were relatively scarce but were detectable in most tissues and embryos at various stages of development. Immunofluorescence stainings of mouse fibroblast cells with anti-CENP-H-specific antibody demonstrated that the CENP-H is specifically and constitutively localized in kinetochores throughout the cell cycle; this was also confirmed by stainings with anti-centromere-specific antibody. Thus the newly isolated CENP-H may play a role in kinetochore organization and function throughout the cell cycle.

D-configuration of serine is crucial in maintaining the phalloidin-like conformation of viroisin

NMR studies have revealed that the conformation of the monocyclic viroisin is dissimilar to that of the corresponding monocyclic derivative of phalloidin, dethiophalloidin, but has much similarity with the conformation of the bicyclic phalloidin. Obviously, one of three structural features found exclusively in the virotoxins is able to compensate for the conformational strain that in the bicyclic phallotoxins maintains the toxic conformation. Synthetic work on virotoxin analogues has shown that both the additional hydroxy group in allo-hydroxyproline and the methylsulfonyl moiety in the 2'-position of tryptophan are unlikely to represent the structural element in question, leaving the D-serine moiety as the supposed key element. In this study we asked whether it is the hydroxy group of this amino acid or its D-configuration that is responsible for the effect. We synthesized four viroisin analogues and submitted them to conformational analysis by NMR as well as to an actin binding assay. While the rotating-frame nuclear Overhauser effect (ROESY) spectra of the analogues with L-configured amino acids showed several sets of signals, indicating the existence of conformers interconverting more slowly than the NMR time scale, the spectra of the analogues with D-configured amino acids showed only one set of signals. Remarkably, the two viroisin analogues with D-serine and D-alanine also had distinctly higher affinities for filamentous actin than their L-configured counterparts, suggesting that the high biological activity may be correlated with the absence of multiple and slowly interconverting conformers. Anyhow, D-configuration of serine is the structural element that maintains the phalloidin-like structure, while the hydroxy group does not contribute to conformational stability but is likely to be in contact with the actin surface.

Fragment reconstitution of a small protein: disulfide mutant of a short C-terminal fragment derived from streptococcal protein G

Hierarchical studies on the folding of protein G B1 domain have shown that the C-terminal fragment (C16) has a considerable amount of beta-hairpin structure that exchanges between the folded and unfolded states at room temperature, and that the C16 fragment binds noncovalently to an N-terminal fragment (N40) under physiological conditions. Those studies have led us to the hypothesis that the amphipathic beta-hairpin structure of C16 initiates folding of the domain. To obtain a more detailed understanding of the folding mechanism of the domain, we designed a mutant of C16 (SS16ox) with a disulfide bond between residues 41 and 56, and then examined the interaction of the mutant with N40 by surface plasmon resonance (SPR) and by thermal denaturation studies using circular dichroism. SS16ox strongly interacted with N40, with an equilibrium constant, KD, that was 7-fold higher than wild-type. The association rate constant, kon, of SS16ox was 8.7-fold higher than that of wild-type. This strong interaction can be explained by the entropic effect of the disulfide bond. The introduction of the disulfide bond into C16 stabilizes the beta-hairpin structure of C16, accelerates the association rate with N40, and then stabilizes the whole complex. These results support a hypothetical folding mechanism of protein G where the amphipathic beta-hairpin structure of C16 acts as a nucleus and accelerates folding of the whole molecule.

Biological actions of the epidermal growth factors-like domain peptides of mouse schwannoma-derived growth factor and human amphiregulin

Several members of the epidermal growth factor (EGF) family of growth factors that contain EGF-like units at their carboxy portion have been isolated and characterized. Schwannoma-derived growth factor (SDGF) and amphiregulin (AR) are members of this family. SDGF has high sequence homology to AR, and is known to be not only a potent mitogen for astrocytes and fibroblasts but also a neurotrophic factor. We previously confirmed that the synthetic EGF-like peptides SDGF(38-80) and AR(44-84), corresponding to the EGF-like domain of mouse SDGF and human AR, respectively, formed similar disulfide bond patterns to that of EGF. In the present study, we further investigated the biological actions of these two EGF-like peptides on several cultured cell lines. We found that SDGF(38-80) and AR(44-84) have weak mitogenic activity in NIH/3T3 cells and weak binding affinity to the EGF receptor on the surface of A431 cells compared with EGF. However, SDGF(38-80) and EGF induced short neurite outgrowth in PC12 h cells, a subclone of PC12 cells, at 100 nM. In addition, a significant increase in acetylcholinesterase (AChE) activity induced by SDGF(38-80) was observed at a concentration similar range to that of EGF, which is known as a differentiation marker of these cells. The effect of AR(44-84) in PC12 h cells was weaker than those of SDGF(38-80) and EGF, but the AChE activity was significantly increased by the addition of 100 nM AR(44-84), which did not stimulate NIH/3T3 cell growth. These results also suggest that SDGF(38-80) and AR(44-84) may be effective for neuronal differentiation rather than proliferation.

Intermolecular and interdomain interactions of a dynamin-related GTP-binding protein, Dnm1p/Vps1p-like protein

Dnm1p/Vps1p-like protein (DVLP) is a mammalian member of the dynamin GTPase family, which is classified into subfamilies on the basis of the structural similarity. Mammalian dynamins constitute the dynamin subfamily. DVLP belongs to the Vps1 subfamily, which also includes yeast Vps1p and Dnm1p. Typical structural features that discriminate between members of the Vps1 and dynamin subfamilies are that the former lacks the pleckstrin homology and Pro-rich domains. Dynamin exists as tetramers under physiological salt conditions, whereas under low salt conditions, it can polymerize into spirals that resemble the collar structures seen at the necks of constricted coated pits. In this study, we found that DVLP is also oligomeric, probably tetrameric, under physiological salt conditions and forms sedimentable large aggregates under low salt conditions. The data indicate that neither the pleckstrin homology nor Pro-rich domain is required for the self-assembly. Analyses using the two-hybrid system and co-immunoprecipitation show that the N-terminal region containing the GTPase domain and a domain (DVH1) conserved across members of the dynamin and Vps1 subfamilies, can interact with the C-terminal region containing another conserved domain (DVH2). The data on the interdomain interaction of DVLP is compatible with the previous reports on the interdomain interaction of dynamin. Thus, the self-assembly mechanism of DVLP appears to resemble that of dynamin, suggesting that DVLP may also be involved in the formation of transport vesicles.

Fragment reconstitution of a small protein: folding energetics of the reconstituted immunoglobulin binding domain B1 of streptococcal protein G

To elucidate early stages in protein folding, we have adopted a fragment reconstitution method for small proteins. This approach is expected to provide nuclei for protein folding and to allow us to investigate folding mechanisms. In previous work [Kobayashi, N., et al. (1995) FEBS Lett. 366, 99-103.] we demonstrated the association of two complementary fragments, derived from the immunoglobulin G-binding domain B1 of streptococcal Protein G, and showed the structural similarity between the reconstituted domain and the uncleaved wild-type domain. In this work we have further characterized the reconstituted domain as well as the uncleaved domain thermodynamically by means of differential scanning calorimetry (DSC) and circular dichroism (CD) measurements. Although composed of short peptide fragments not linked by covalent bonds, the reconstituted domain showed a typical folding/unfolding curve in both DSC and CD melting measurements and behaved like a globular protein. The domain was not very stable, and the small value of the Gibbs free energy corresponded to the class of the weakest protein-protein binding systems. The denaturation temperature of 0. 78 mM solution was 313 K at pH 5.9 as measured by DSC, which was more than 40 degrees lower than the uncleaved domain. This apparent instability was primarily caused by entropic disadvantage attributed to a bimolecular reaction. The temperature dependence of the enthalpy change from the folded to the unfolded state was almost identical for the reconstituted domain and the uncleaved one. This indicates that most of the noncovalent intramolecular interactions stabilizing the native structure, such as hydrogen bonding and hydrophobic interactions, are regenerated in the reconstituted domain. By comparing the equilibrium constants of the reconstituted and uncleaved domains, we determined the effective concentration to be approximately 6 M at 298 K. Structure-based estimation of the thermodynamic properties from the values of accessible surface areas showed that approximately 35% of the total heat capacity change and approximately 25% of the total enthalpy change can be attributed to the interchain interaction at 298 K. Furthermore, the folding/unfolding equilibrium of beta-hairpin structure of the fragment 41-56 alone was also characterized. These analyses allow us to envision the microdomain folding mechanism of the Protein G B1 domain, in which segment 41-56 first forms a stable beta-hairpin structure and then collides with segment 1-40, followed by spontaneous folding of the whole molecule.

Serotonin increases cytoplasmic Ca2+ concentration in PC12h cells: effect of tachykinin peptides

We report here that serotonin (5-hydroxytriptamine, 5-HT) induces an increase in intracellular Ca2+ concentration ([Ca2+]i) in rat pheochromocytoma PC12h cells, a subclone of PC12 cells, which was detected by using Ca2+ sensitive indicator dye fura-2. The [Ca2+]i increase completely disappeared when extracellular Ca2+ was chelated with excess EGTA and potently suppressed in Na+-free buffer. Nifedipine, a voltage-dependent L-type calcium channel blocker, significantly blocked the 5-HT response. Addition of another 4 mM Ca2+ to the cell suspension attenuated the [Ca2+]i increase induced by 5-HT, whereas the nicotinic action was remarkably potentiated. Furthermore, metoclopramide, a 5-HT3 receptor antagonist, inhibited the 5-HT response in a dose dependent manner. These findings suggest that the 5-HT-induced [Ca2+]i increase involves the mediation of a voltage-dependent Ca2+ channel, evoked by membrane depolarization via the activation of cation channel-type receptors, 5-HT3 receptors. We also noted the inhibitory action of tachykinin peptides on the 5-HT response, suggesting that the cell line is useful to investigate these neuromodulatory actions in the nervous system.

Amyloid beta-peptide-induced inhibition of MTT reduction in PC12h and C1300 neuroblastoma cells: effect of nitroprusside

We have investigated the effect of amyloid beta-peptide (Abeta) in rat pheochromocytoma PC 12h and murine C 1300 neuroblastoma cells by using MTT ¿3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) reduction assay. Exposure of the cells to Abeta peptides, Abeta1-40 and its fragment Abeta25-35, induced a concentration-dependent inhibition of MTT reduction in both cell lines, and MTT-dependent LDH release due to cell lysis in PC12h cells. We also found that sodium nitroprusside (SNP), a spontaneous nitric oxide (NO) generator, significantly prevented the inhibition of MTT reduction and MTT-dependent LDH release caused by Abeta peptides at 10-100 microM, although a high concentration of SNP (> or = 333 microM) was remarkably toxic by itself. Since the inhibition of MTT reduction caused by Abeta is known as one of the first indicators of its toxicity, these findings suggest that Abeta peptides have a toxic effect in these cell lines, and SNP may attenuate the Abeta peptide-induced toxicity. In regard the mechanisms of the actions of SNP, hydroxylamine which also generates NO and 8-Br-cGMP, a membrane-permeable analogue of cyclic GMP (cGMP), failed to prevent the inhibition of MTT reduction caused by Abeta25-35 in PC12h cells, implying that the effect of SNP may be mediated by the NO-independent pathway. Since potassium ferrocyanide showed a significant prevention at 333 microM although it had toxic effect at this concentration, it is considered that the ferrocyanide portion of the SNP metabolite may be partially involved. The cell death induced by other oxidative insults, such as glutamate and hydrogen peroxide (H2O2), could not be attenuated by SNP in both cell lines. Thus, the observed effect of SNP might not be due to its direct antioxidative action.

Signaling pathways via NK1 receptors and their desensitization in an AR42J cell line

Substance P (SP) has been shown to induce phosphatidylinositol (PI) hydrolysis and Ca2+ mobilization in AR42J cells. In this study, we confirmed the expression of NK1 but not NK2 or NK3 receptors in this cell line, and further investigated signaling pathways via NK1 receptors and their desensitization. The activation of NK1 receptors by SP affected neither basal cyclic AMP level nor cyclic AMP accumulation induced by secretin and forskolin, although it stimulated PI hydrolysis. Furthermore, SP induced Ca2+ mobilization even in the absence of extracellular Ca2+, though maximal response was reduced. U73122, a phospholipase C (PLC) inhibitor, nearly abolished Ca2+ response to SP. In addition, SP-induced Ca2+ signaling and PI hydrolysis rapidly desensitized following short exposure to SP, which did not affect the Ca2+ amount in intracellular Ca2+ stores or Ca2+ responses to carbachol and gastrin releasing peptide-10. These findings suggested that NK1 receptors do not couple to adenylate cyclase, although they induce PI response, and that NK1 receptors induce both intracellular Ca2+ release and Ca2+ influx through PLC activation. Ca2+ signaling and PI hydrolysis through NK1 receptors desensitized rapidly after the stimulation, maybe dependent on the modification of NK1 receptors.

Activin A and all-trans-retinoic acid cooperatively enhanced the functional activity of L-type Ca2+ channels in the neuroblastoma C1300 cell line

Activin, a member of the transforming growth factor-beta superfamily, regulates various physiological functions. In the present study, we investigated the effect of activin on neuronal differentiation, particularly the functional activity of voltage-dependent Ca2+ channels, in murine neuroblastoma C1300 cells. A slight K(+)-induced increase in the intracellular free Ca2+ ([Ca2+]i) was observed in C1300 cells untreated and treated with either activin A or all-trans-retinoic acid, while treatment with both agents significantly enhanced the increase. The [Ca2+]i increases potentiated by activin A and all-trans-retinoic acid were nearly abolished in the presence of 1.0 mM nickel or in the absence of extracellular Ca2+. Nifedipine (0.1 microM) and omega-conotoxin (1.0 microM), inhibitors of L- and N-type Ca2+ channels, respectively, partially inhibited these responses, however the inhibitory effects of these compounds were not additive. In addition, Bay K 8644, an activator of L-type Ca2+ channels, enhanced the K(+)-induced [Ca2+]i increase. These findings indicated that depolarization evoked the Ca2+ influx, at least in part, through L-type Ca2+ channels in C1300 cells treated with both activin A and all-trans-retinoic acid.

Further identification of neurokinin receptor types and mechanisms of calcium signaling evoked by neurokinins in the murine neuroblastoma C1300 cell line

It has been suggested that murine neuroblastoma C1300 cells express endogenous neurokinin NK2 receptors with features that differ from those of NK2 receptors characterized in other systems. In this study, we have further characterized the neurokinin receptor types present in this cell line. RNA blots showed that mRNAs of NK2 and NK3 receptors, but not of NK1 receptors, were expressed in C1300 cells. The increase in the cytosolic calcium concentration ([Ca2+]i) induced by 0.33 microM neurokinin A was completely inhibited by SR 48968, an NK2 receptor antagonist, whereas the partial response to 0.33 microM neurokinin B was unaffected, and the response was completely inhibited by SR 142801, and NK3 receptor antagonist. In addition, the [Ca2+]i increase by 0.33 microM senktide, an NK3 receptor agonist, was inhibited by SR 142801 but not by SR 48968. These findings indicated that C1300 cells endogenously express functional NK2 and NK3 receptors. It was also demonstrated that NK2 and NK3 receptors can be activated independently by 3.3 microM neurokinin A in the presence of 1.0 microM SR 142801 or 1.0 microM senktide, respectively. Therefore, the mechanisms of Ca2+ signaling mediated by endogenous NK2 and NK3 receptors were investigated. The independent activation of NK2 or NK3 receptors induced not only the [Ca2+]i increase, but also stimulated the formation of inositol trisphosphates; both these responses were inhibited by U73122, a phospholipase C (PLC) inhibitor. In addition, NK2 and NK3 receptor-mediated [Ca2+]i increase was partially attenuated in the absence of extracellular Ca2+ or in the presence of nickel, an inorganic Ca2+ influx blocker, but was unaffected by nifedipine and omega-conotoxin, L- and N-type voltage-dependent Ca2+ channel blockers, respectively. Furthermore, the depolarization by 60 mM K+ did not affect the [Ca2+]i. These findings suggested that the NK2 and NK3 receptor-mediated [Ca2+]i increase was due to the activation of PLC and was dependent on the mobilization of internal Ca2+ and the entry of extracellular Ca2+ through voltage-independent channels. This study showed that the C1300 cell line is a useful system with which to investigate pharmacological functions and signaling pathways of endogenous NK2 and NK3 receptors.

Multiple intracellular signal transduction pathways mediating inward current produced by the neuropeptide, achatin-I

The effects of intracellular signal transduction system inhibitors on the inward current (Iin) caused by achatin-I (Gly-D-Phe-Ala-Asp), an Achatina endogenous tetrapeptide having a D-phenylalanine residue, applied locally onto the neurone tested, were examined under voltage clamp using two identifiable Achatina giant neurone types, v-RCDN (ventral-right cerebral distinct neurone) and PON (periodically oscillating neurone). H-89 (N-[2-(p-bromocinnamylamino)-ethyl]-5-isoquinolinesulfonamide) (adenosine-3',5'-cyclic monophosphate (cyclic AMP)-dependent protein kinase inhibitor) markedly suppressed the achatin-I-induced Iin on PON, whereas this drug was ineffective on the Iin of v-RCDN. Dose (pressure duration)-response study of achatin-I on PON in a physiological solution and in the presence of H-89, and Lineweaver-Burk plot of these data, indicated that H-89 inhibited the Iin in a noncompetitive manner. KT5823 (N-methyl-(8R*,9S*,11S*)-(-)-9-methoxy-9-methoxycarbonyl-8-methyl-2,3,9, 10-tetrahydro-8,11-epoxy-1H,8H,11H-2, 7b,11a-triazadibenzo[a,g]cycloocta[c,d,e]-trinden-1-on e) (guanosine-3',5'-cyclic monophosphate (cyclic GMP)-dependent protein kinase inhibitor) suppressed the achatin-I-induced Iin of v-RCDN in mainly noncompetitive and partly uncompetitive manners, but this drug had no effect on the Iin of PON. W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide) (calmodulin inhibitor) suppressed noncompetitively the Iin of PON, but this drug had no effect on the Iin of v-RCDN. IBMX (3-isobutyl-1-methylxanthine) (cyclic nucleotide phosphodiesterase inhibitor) enhanced the achatin-I-induced Iin of v-RCDN, but this drug was ineffective on the Iin of PON. However, IBMX might have effects on the achatin-I receptor sites on v-RCDN. These findings suggest multiple intracellular signal transduction pathways mediating the achatin-I-induced Iin: the Iin of PON is via cyclic AMP-dependent and probably Ca2+/calmodulin-dependent protein kinases, and that of v-RCDN via cyclic GMP-dependent protein kinase. Other signal transduction system inhibitors including calphostin C (2-[12-[2-(benzyloxy)-propyl]-3, 10-dihydro-4,9-dihydroxy-2,6,7,11-tetramethoxy-3,10-dioxo-1-per yleny]-1 -methylethyl carbonic acid 4-hydroxyphenyl ester) (protein kinase C inhibitor) did not significantly affect the Iin of both v-RCDN and PON.

Further mapping of the Achatina giant neurone types sensitive to the neuroactive peptides isolated from invertebrates

1. The effects of the 10 synthetic neuroactive peptides originally isolated from invertebrates, applied locally to the neurone tested by the brief pneumatic pressure ejection on the identifiable neurone types of Achatina fulica Ferussac were examined. 2. Achatin-1 (Gly-D-Phe-Ala-Asp), an Achatina endogenous tetrapeptide having a D-phenylalanine residue, ejected locally, showed the depolarizing effects on nearly half of the number of neurone types tested. 3. ACEP-1 (Ser-Gly-Gln-Ser-Trp-Arg-Pro-Gln-Gly-Arg-Phe-NH2), isolated originally from Achatina atria, and pedal peptide (Pro-Leu-Asp-Ser-Val-Tyr-Gly-Thr-His-Gly-Met-Ser-Gly-Phe-Ala) and buccalin (Gly-Met-Asp-Ser-Leu-Ala-Phe-Ser-Gly-Gly-Leu-NH2), found in Aplysia neurones, showed excitatory effects on some Achatina neurone types. 4. Myomodulin (Pro-Met-Ser-Met-Leu-Arg-Leu-NH2), found in Aplysia neurones, produced a hyperpolarization on nearly half of the number of Achatina neurone types tested. The two FMRFamide-like peptides, <EDPFLRFamide (<Glu-Asp-Pro-Phe-Leu-Arg-Phe-NH2), isolated from Helix heart, and AF1 (Lys-Asn-Glu-Phe-Ile-Arg-Phe-NH2), from Ascaris head, also showed hyperpolarizing effects on more than half of the number of Achatina neurone types. 5. SALMFamide 1 (Gly-Phe-Asn-Ser-Ala-Leu-Met-Phe-NH2), isolated from Asterias nervous system, CCAP (Pro-Phe-Cys-Asn-Ala-Phe-Thr-Gly-Cys-NH2), from Carcinus pericardial organ, and corazonin (<Glu-Thr-Phe-Gln-Tyr-Ser-Arg-Gly-Trp-Thr-Asn-NH2), from Periplaneta cardiac corpus, had no effect on Achatina neurones.

Chemical synthesis and biological activities of the EGF-like domain of mouse schwannoma-derived growth factor (SDGF)

Schwannoma-derived growth factor (SDGF), an epidermal growth factor (EGF) family peptide recently discovered, has an EGF-like domain in the carboxyl terminal portion. In this study, we synthesized mSDGF(38-80) corresponding to the EGF-like domain of mouse SDGF by means of stepwise solid-phase method using Fmoc chemistry in order to evaluate the biological function of the EGF-like domain in SDGF. The linear peptide of mSDGF(38-80) was folded by direct oxidation with reduced and oxidized glutathione to form intramolecular disulfide bridges in synthetic peptide. On the biological activity, we examined mitogenic activity induced by mSDGF(38-80) in NIH/3T3 fibroblast cells and interaction with EGF receptor in A431 cells. In the results, mSDGF(38-80) was confirmed to form three disulfide linkages that were similar in pattern to EGF by amino acid and sequence analysis of fragments obtained after thermolytic digestion. However, mSDGF(38-80) possessed weak mitogenic activity in NIH/3T3 cells and weak binding affinity for the EGF receptor in A431 cells compared with those of human EGF. These results suggest that the EGF-like domain of SDGF may have little effect upon mitogenic activity and the EGF receptor binding of SDGF.

Comparative study on the conformation of phalloidin, viroisin, and related derivatives in aqueous solution

We investigated the conformations of toxic phalloidin and viroisin in aqueous solution using 500-MHz 1H-NMR spectroscopy in conjunction with molecular modeling. The conformations of two non-toxic phalloidin derivatives, secophalloidin and dethiophalloidin, were also correspondingly studied for comparison purposes. Results indicate that the non-toxic peptides have a multiple conformation, whereas the toxic peptides are comprised of a rigid molecule. It was found that the conformation of phalloidin partially resembles that of viroisin in the region of Cys3-Pro4-Ala5-Trp6, being different from that of the non-toxic peptides; thereby suggesting this region plays an important role leading to their toxicity.

Complement assembly of two fragments of the streptococcal protein G B1 domain in aqueous solution

We examined the complementation of various pairs of fragments derived from the streptococcal protein G B1 domain by NMR and CD. Most were not associated; however, one pair of fragments (1-40) and (41-56) interacted sufficiently enough to regenerated a stable 1:1 complex, Kd = 9 x 10(-6) M. A 2D-NMR analysis showed that the structure of the complex resembled that of native domain. Here we discuss the complementation from the viewpoint of the folding pathway of the protein.

Trophic effects of substance P and beta-amyloid peptide on dibutyryl cyclic AMP-differentiated human leukemic (HL-60) cells

The neuropeptide substance P (SP) is a mediator of neurogenic inflammation. Also, beta-amyloid protein (beta AP) can directly activate the cell types involved in inflammatory processes. The relationship between SP and beta AP on their biological actions has attracted much interest. SP is trophic in neuronal cells and protected them against the death induced by beta AP. In this study, we examined the effects of SP and beta-amyloid peptide on cell viability in neutrophil-like HL-60 cells, by means of the WST-1 tetrazolium and lactate dehydrogenase (LDH) release assays. The results showed that SP promoted the cell survival on neutrophil-like HL-60 cells in serum-free conditions. Also, beta-amyloid peptide showed trophic effects rather than toxic in these cells in WST-1 assay, though it is reportedly toxic in neuronal cells.

Pharmacological evidence for neurokinin receptors in murine neuroblastoma C1300 cells

We found that neurokinin A (NKA) and neurokinin B (NKB) induce an increase in the concentration of intracellular free Ca2+ ([Ca2+]i) in murine neuroblastoma C1300 cells (EC50: NKA 87 +/- 13 nM, NKB 97 +/- 15 nM). Substance P (SP) also caused a transient Ca2+ increase, although the potency of SP was much less than that of NKA and NKB. The increase in [Ca2+]i induced by NKA and NKB was inhibited by SR 48,968, a selective antagonist for NK2, and [beta Ala8]NKA(4-10), a selective agonist for NK2, did not stimulate the increase in [Ca2+]i. NKA- and NKB-induced Ca2+ mobilization was not inhibited by CP-96,345 and [Trp7, beta Ala8]NKA(4-10), selective antagonists for NK1 and NK3, respectively. These results suggested that C1300 cells express endogenous NK2 neurokinin receptors that have different features from known NK2 receptors.

beta-Amyloid peptide, substance P, and SEC receptor ligand activate cytoplasmic Ca2+ in neutrophil-like HL-60 cells: effect of chemotactic peptide antagonist BocMLF

It has been reported that a discrete peptide fragment of beta-amyloid protein, beta A(25-35), and neuropeptide substance P (SP) possessed sequence homology and could bind to the serine protease inhibitor (serpin) enzyme complex (SEC) receptor. Thus, it has been thought that these peptides and SEC receptor ligand might have similar biological activities. In the present study, we found that C-terminal amidated beta A(25-35)-NH2, SP, and the SEC receptor ligand, Phe-Val-Phe-Leu-Met(FVFLM), could induce an increase in the intracellular free Ca2+ concentration ([Ca2+]i) in neutrophil-like human leukemic (HL-60) cells. Pretreatment with pertussis toxin (PTX) potently inhibited the increase in [Ca2+]i stimulated by these peptides, suggesting that these responses might be mediated by PTX-sensitive G-proteins. Furthermore, we examined the effect on these responses of t-butyloxycarbonyl-methionyl-leucyl-phenylalanine (BocMLF), which is a competitive antagonist of chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLF) at its receptor. BocMLF scarcely inhibited the [Ca2+]i increase stimulated by beta A(25-35)-NH2. However, the increase in FVFLM-induced [Ca2+]i was potently inhibited by BocMLF. The results suggest that the [Ca2+]i activation of beta A(25-35)-NH2 may have a different mechanism from that of FVFLM in neutrophil-like HL-60 cells, which is not mediated by the SEC-receptor.

Synthesis and biological activity of N-terminal-truncated derivatives of human epidermal growth factor (h-EGF)

To investigate the contribution of the N-terminal sequence of h-EGF to its biological activity and the formation of three intramolecular disulfide bonds by oxidative refolding via air oxidation, five derivatives of h-EGF with a single N-terminal amino acid deletion were synthesized by solid-phase synthesis. The homogeneity of the synthetic peptides was confirmed by analytical reversed-phase HPLC, amino acid analysis, and FAB-MS. The pairing of the three disulfide bridges in synthetic peptides was determined by thermolytic digestion. All N-truncated derivatives of h-FGF formed the correct intramolecular three disulfide linkages during oxidative refolding and had equipotent activity in both EGF receptor binding on A-431 epidermoid carcinoma cells and mitogenesis on NIH-3T3 fibroblast cells, compared with authentic h-EGF. The results suggested that the five residues from N-terminal sequence of h-EGF have no effect on the formation of the correct disulfide linkages in h-EGF and do not exert a significant influence on its biological activity.

Chemical synthesis and biological activity of the EGF-like domain of heparin-binding epidermal growth factor-like growth factor (HB-EGF)

Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a recently discovered member of the epidermal growth factor (EGF) family. This novel growth factor possesses the EGF-like domain in the carboxyl portion. In order to evaluate the biological function of the EGF-like domain in HB-EGF, human HB-EGF(44-86) corresponding to the EGF-like domain was synthesized by the solid-phase procedure using the Fmoc strategy. It was confirmed by amino acid microsequencing of cysteine-containing fragments derived from thermolytic digestion that the pattern of three disulfide bond pairings in synthetic HB-EGF(44-86) was consistent with that of EGF and transforming growth factor-alpha (TGF-alpha). The homogeneity of the synthetic peptide was confirmed by analytical RP-HPLC, amino acid analysis and fast atom bombardment mass spectrometer (FAB-MS). Compared with h-EGF, the EGF-like domain of human HB-EGF showed a comparable mitogenic activity in the proliferation of NIH/3T3 fibroblast cells. These results suggest that the EGF-like domain of human HB-EGF may play an important role in mitogenic activity.

Determination of electrostatic potential around specific locations on the surface of actin by diffusion-enhanced fluorescence resonance energy transfer

In this study we have established systematic procedures for the measurement of electrostatic potentials around specific and localized portions of protein surfaces. Diffusion-enhanced fluorescence energy transfer was used for these determinations. Energy transfer from donor molecules to freely diffusing acceptors is sensitive to the electrostatic potential around the donor when the acceptors possess electric charges. To quantify this sensitivity phenomenon in a controllable environment, we observed energy transfer from excited terbium chelate donors of known electric charge to a series of acceptors of different charges but bearing the same chromophore group. The rate of energy transfer was calculated theoretically (considering the structural arrangement of charged groups around the chromophore center), as well as determined experimentally (by time-resolved detection of terbium luminescence), with the two values obtained by the different means in close agreement. Having established the validity of this procedure using a relatively simple system, we studied the electrostatic conditions around two specific sites on the surface of actin molecules. A negative potential was found at both sites; the potential at one location (around the myosin binding site) was nearly neutralized by the addition of myosin subfragment-1, while the potential at the other site (around the phalloidin binding site) was not significantly affected.

Inhibitory effects of beta-amyloid peptides on nicotine-induced Ca2+ influx in PC12h cells in culture

Synthetic beta-amyloid peptides and the neuropeptide substance P (SP) were examined for their ability to modulate nicotinic response in PC12h cells, a subclone of PC12 cells, SP, beta A1-40 and its peptide fragment beta A25-35-NH2 significantly inhibited an increase in cytoplasmic calcium concentrations ([Ca2+]i) induced by nicotine in a dose-dependent manner. Furthermore, beta A1-40 was found to inhibit the [Ca2+]i increase induced by depolarization with a high concentration of potassium. These findings show that both beta A1-40 and beta A25-35-NH2 may mimic the function of SP on inhibition of nicotinic response through different mechanisms.

Structure-activity relationships of human epidermal growth factor(h-EGF)

The 53 amino acid regulatory peptide, human epidermal growth factor (h-EGF), is a potent mitogen that stimulates cellular proliferation and differentiation in a wide variety of cells. To identify the critical residues that elicit the biological activity of h-EGF, peptides were constructed by stepwise solid-phase synthesis using the Boc-HF strategy. These synthetic peptides were characterized by HPLC, FAB-MS, amino acid analysis and thermolytic digestion. The mitogenic activity of these h-EGF analogues was determined by the stimulation of [3H]-thymidine uptake into DNA in NIH-3T3 fibroblast cell lines. Substituting Tyr with Phe at position's 37 and 13 had little effect on the mitogenic activity of h-EGF. In contrast, Ala at these positions resulted in a severe loss of activity (20 and 10(3)-fold). These results indicate that the hydrophobicity of the side chain at positions 13 and 37 of h-EGF is essential for its biological activity. A semiconservative substitution of Leu with Ala at position 15 and a conservative change of Lys at position 41 also drastically reduced mitogenic activity (10(4) and 10(5)-fold). Thus, the bulky hydrophobic side chain at position 15 and the guanidino group at position 41 are indispensable in determining the biological activity of h-EGF.

A structurally flexible and antigenically variable N-terminal domain of the hepatitis C virus E2/NS1 protein: implication for an escape from antibody

Hepatitis C virus persists in most infected hosts, and causes chronic hepatitis, liver cirrhosis, and/or hepatocellular carcinoma in humans. During the infection the RNA genome of hepatitis C virus undergoes frequent missense mutations at one or two "hypervariable" regions within a presumptive envelope gene (Okamoto et al., 1992, Virology 190, 894-899; Ogata et al., 1991, Proc. Natl. Acad. Sci. USA 88, 3392-3396). In the present study, we analyzed three cases of hepatitis C virus infection, two in chimpanzees and one in humans, for the antigenicity of peptides predicted from the hypervariable region of viral RNA obtained during the follow-up. Our results showed a successive appearance of hepatitis C virus mutants with antigenically distinct amino acid sequence within the domain; and the amino acid replacement was associated with an alteration of predicted local secondary structure of the epitope region. Hence, the hypervariable domain of the hepatitis C virus envelope appeared to be structurally flexible and antigenically variable, providing the virus a way to escape from host immunity.

Electrostatic potential around actin

We presume that tension of contracting muscle originates from electrostatic force experienced by actin and myosin. We suppose that a high-energy state of myosin-ADP-Pi interacts with actin, transferring the stored energy to actin, and that the actin excited in this way develops around itself electric field which exerts sliding force against charged myosin heads. To explore the idea, first we conjectured how electric charges on actin produce electric field in the axial direction, and second we experimentally examined electrostatic circumstances around actin in solution and in muscle fibers by optimizing diffusion-enhanced fluorescence energy transfer. In the experiments, Tb ion, which has a long excited-state lifetime, was used as donor. To introduce Tb to actin, Tb-DTPA-phalloin and Tb-DTPA-maleimide were synthesized. As acceptors with electric charges (Za = -3 to +2), rhodamine B that was conjugated with various amino acids or their derivatives was used. The fluorescence energy transfer efficiency (ET) was estimated from the shortening in the lifetime of Tb. The electrostatic circumstances around actin were inferred from the ET-Za relation. When Tb was introduced at Cys-374 of actin, the Tb-site was found in negative electric potential. S-1 binding to the labeled actin neutralized the electric potential almost completely. Tb-DTPA-phalloin bound to actin seemed to reside in the vicinity of tryptophan residue(s). Electric potential around the phalloin site was negative. S-1 binding to the actin slightly reduced the negativity. In glycerinated fibers in the rigor state, the phalloin site was again found in negative potential. When fibers were transferred from an ADP-rigor solution to an active solution, the negative electric potential was neutralized to some extent. The direction of this change could not be explained by detachment of crossbridges from actin, since the detachment should have given an opposite direction of changes in the electric potential. Thus, this observation may indicate that electric potential characteristic of the active state occurs at actin surfaces.

Two distinct subtypes of hepatitis C virus defined by antibodies directed to the putative core protein

Four distinct genotypes of hepatitis C virus types I, II, III and IV have been identified by comparison of nucleotide sequences of isolates from different areas of the world. We examined the possibility that hepatitis C virus may have serologically definable subtypes. Enzyme-linked immunosorbent assay systems were prepared by use of two synthetic peptides deduced from the putative core protein of hepatitis C virus. The following are the two peptides that were used: (a) IPKARRPEGRTWAQPGY (subtype-1) conserved in hepatitis C virus isolates with type I and type II genotypes; and (b) IPKDRRSTGKSWGKPGY (subtype-2) conserved in type III and type IV genotypes. With the enzyme-linked immunosorbent assays, the subtype-1 antibodies were detected in 26 (68%) of 38 subjects whose hepatitis C virus RNA had been genotyped as type I or type II, whereas subtype-2 antibodies were not detected. Inversely, the subtype-2 antibodies were detected in 10 (56%) of 18 subjects with hepatitis C virus RNA genotypes III or IV, whereas subtype-1 antibodies were detected in none of them. These results suggest that hepatitis C virus has two serologically distinguishable core antigen subtypes, corresponding to either genotype I/II or genotype III/IV. Subtyping of HCV by serological methods would contribute to tracking transmission routes of the virus, especially in cases where serum samples were not stored under conditions to preserve RNA or in infected hosts who have cleared the virus and therefore have only antibodies remaining to identify the infection.

G protein antagonists. A novel hydrophobic peptide competes with receptor for G protein binding

A substance P (SP) analog, [D-Pro4,D-Trp7,9,10] SP4-11, is known to inhibit the actions of various structurally unrelated messenger molecules as well as SP. Our studies on the effects of this peptide on the regulation of purified G proteins by receptor showed that at least some of the biological effects of the peptide can be explained by the ability of the peptide to block the activation of G proteins by receptors. Here we report that a novel truncated SP-related peptide, pGlu-Gln-D-Trp-Phe-D-Trp-D-Trp-Met-NH2, inhibited the activation of G(i) or G(o) by M2 muscarinic cholinergic receptor (M2 mAChR) or of Gs by beta-adrenergic receptor in the reconstituted phospholipid vesicles, assayed by receptor-promoted GTP hydrolysis. The inhibition by the peptide was apparently reversible and competitive with respect to receptor binding to G proteins; the inhibition could be overcome by increasing the concentration of receptor in the vesicles and was not altered by changes in the concentration of G protein. The competing effects of the peptide were used to analyze the effect of agonist on receptor-G protein interaction. The concentration change of muscarinic agonist did not alter the inhibitory effects of the peptide on M2 mAChR-promoted GTPase by G(o), which is consistent with the idea that agonist increases the regulatory efficiency of the receptor but does not alter its affinity for G proteins. This new group of compounds (G protein antagonists) is a promising tool to study receptor-G protein interaction quantitatively.

1H NMR study on the conformation of bacitracin A in aqueous solution

The conformation of bacitracin A, a widely used cyclic dodecapeptide antibiotic in aqueous solution, has been investigated using 500 MHz 1H NMR and molecular modeling. Findings revealed that a region (residues 1-6) is folded over the cyclic ring, resulting in metal coordination sites, a thiazoline ring, and Glu4 and His10 being proximate to each other.

Demonstration of a hepatitis C virus-specific antigen predicted from the putative core gene in the circulation of infected hosts

An ELISA was used to detect a protein derived from the core gene of the hepatitis C virus (HCV) in human plasma. The solid phase antibody in the assay was a murine monoclonal antibody against a synthetic peptide deduced from the putative core gene of HCV (residues 39 to 74). An enzyme-labelled affinity-purified human antibody directed at another region within the HCV core (residues 5 to 23) was the second antibody tracer. The ELISA had a sensitivity capable of detecting a few ng/ml of the HCV core polypeptide expressed in Escherichia coli. Core antigen activity in plasma of infected hosts was detected after treatment of HCV RNA-rich fractions from buoyant density centrifugation with the detergent Tween 80. There was a direct correlation between core antigen ELISA values of a plasma fraction and intensities of polymerase chain reaction signals for HCV RNA. These observations are consistent with the proposal that the N-terminal sequence of the predicted polyprotein of HCV is a nucleocapsid protein, and that improved core antigen assays may correlate with viraemia.

Antibodies against synthetic oligopeptides deduced from the putative core gene for the diagnosis of hepatitis virus infection

Immunoassays were developed to detect antibodies against oligopeptides deduced from the putative core gene of hepatitis C virus, and their performances were compared with that of the commercial immunoassay for antibodies against the product of nonstructural regions of hepatitis C virus (anti-C100-3). A 19-mer oligopeptide (CP10) and a 36-mer oligopeptide (CP9) were chemically synthesized, which represented hydrophilic regions of the product of the hepatitis C virus core gene. They were used to capture corresponding antibodies, anti-CP10 and anti-CP9, by enzyme-linked immunosorbent assay in sera from patients with acute or chronic non-A, non-B liver disease and in blood donations. At the onset of acute non-A, non-B hepatitis, anti-CP10 was detected in 15 of 20 patients (75%), and anti-CP9 was detected in 14 patients (70%). This was more frequent than anti-C100-3, which was found in only 9 patients (45%). In 186 patients with chronic non-A, non-B liver disease, anti-CP9, anti-CP10 or both were detected in 170 patients (91%). This was more frequent than anti-C100-3, which was found in 138 patients (74%). Blood with anti-CP10 as the single serological marker for hepatitis C virus infection transmitted non-A, non-B hepatitis by needlestick exposure. In sera from 558 apparently healthy blood donors, anti-CP10 was detected in 55 donors (9.9%), anti-CP9 was detected in 26 donors (4.7%) and anti-C100-3 was detected in 7 donors (1.3%).(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic control of immune responses in mice to synthetic peptides of a Streptococcus mutans surface protein antigen

The immune responses to a cell surface protein antigen (PAc) of Streptococcus mutans and a peptide corresponding to residues 301 to 319 of the protein antigen [PAc(301-319)] in various strains of mice were studied, with attention being given to the haplotype of major histocompatibility complex (MHC) class II genes. Subcutaneous immunization of mice carrying the MHC class II I-Ad gene [BALB/c, B10.D2, B10.GD, and (B10.D2 x B10.G)F1 mice] with the peptide induced strong serum immunoglobulin G (IgG) responses to recombinant PAc (rPAc) and the peptide. Subcutaneous immunization of mice carrying the haplotype k or b of the H-2 I-A gene (C3H/HeN, C57BL/6, B10.BR, B10.A, or B10 mice) with the peptide induced intermediate serum IgG responses to rPAc and the peptide, and subcutaneous immunization of mice carrying the haplotype s or q of the H-2 I-A gene (DBA/1, B10.S, or B10.G mice) induced weak serum IgG responses to rPAc and the peptide compared with the responses of mice carrying the I-Ad gene. PAc(301-319) strongly induced PAc(301-319)-specific T-cell proliferation in B10.D2 mice but not in B10.G mice. The T-cell proliferation in B10.D2 mice was inhibited by treatment of antigen-presenting cells with anti-I-Ad monoclonal antibody but not with anti-I-Ab monoclonal antibody. These results indicate that the immune responses to the peptide in mice are genetically restricted or dominated by the MHC class II gene (I-Ad). To map antigenic epitopes in PAc(301-319) and PAc in mice bearing different H-2 haplotypes, 10 overlapping decapeptides covering PAc(301-319) and 153 decapeptides covering the entire mature PAc were synthesized. Of 10 decapeptides covering PAc(301-319), 6, 7, 1, and 1 decapeptides showed strong reactions with anti-PAc(301-319) sera from B10.D2 (H-2d), B10.GD (H-2g2), B10.BR (H-2k), and B10.A (H-2a) mice, respectively. None of these overlapping decapeptides reacted with anti-PAc(301-319) sera from B10.S (H-2s) and B10.G (H-2q) mice. Epitope-scanning analyses of the mature PAc molecule showed that antigenic epitopes scattered throughout the molecule and that antigenic epitope patterns differed in mice with different H-2 haplotypes. In addition, there was little overlap of immunogenic peptides among the mice with different haplotypes.

Molecular heterogeneity of e antigen polypeptides in sera from carriers of hepatitis B virus

Hepatitis B e Ag (HBeAg) was isolated from pooled sera of carriers, without abnormalities in liver function, by affinity column chromatography with mAb against HBeAg. HBeAg polypeptide with an estimated molecular size of 20,000 Da (p20e) was detected, in addition to regular HBeAg polypeptides (p17e/p18e). p20e, as well as p17e/p18e, did not bind with mAb against the carboxyl-terminal domain of the C-gene product. p20e disclosed an N-terminal sequence of MQLFHLXLII- (X unknown), whereas p17e had that of SKLXLGXLXGMDIDPXKEFG- (X's unknown). By comparing them with the amino acid sequence encoded by the precore region and C gene of hepatitis B virus DNA, p20e was deduced to possess amino acids 1 to 19 of the precore-region product at the N-terminus, which contains signal sequence and usually removed before the secretion of HBeAg. p17e had amino acids 20 to 29 of the precore-region product that continued to the C-gene product. Inasmuch as p20e was invariably detected in HBeAg preparations from carriers without evidence for liver disease, it would not have been released into the circulation from destructed hepatocytes. HBeAg polypeptide bearing an uncleaved signal sequence would help in further understanding the mechanism of HBeAg secretion.

Molecular heterogeneity of e antigen polypeptides in sera from carriers of hepatitis B virus

Hepatitis B e Ag (HBeAg) was isolated from pooled sera of carriers, without abnormalities in liver function, by affinity column chromatography with mAb against HBeAg. HBeAg polypeptide with an estimated molecular size of 20,000 Da (p20e) was detected, in addition to regular HBeAg polypeptides (p17e/p18e). p20e, as well as p17e/p18e, did not bind with mAb against the carboxyl-terminal domain of the C-gene product. p20e disclosed an N-terminal sequence of MQLFHLXLII- (X unknown), whereas p17e had that of SKLXLGXLXGMDIDPXKEFG- (X's unknown). By comparing them with the amino acid sequence encoded by the precore region and C gene of hepatitis B virus DNA, p20e was deduced to possess amino acids 1 to 19 of the precore-region product at the N-terminus, which contains signal sequence and usually removed before the secretion of HBeAg. p17e had amino acids 20 to 29 of the precore-region product that continued to the C-gene product. Inasmuch as p20e was invariably detected in HBeAg preparations from carriers without evidence for liver disease, it would not have been released into the circulation from destructed hepatocytes. HBeAg polypeptide bearing an uncleaved signal sequence would help in further understanding the mechanism of HBeAg secretion.

Structure-activity relationships of mammalian bombesin-like neuropeptides in the contraction of rat uterus

Various peptide derivatives of the C-terminal decapeptide of gastrin releasing peptide (GRP-10) and neuromedin B (NMB), i.e., carboxyl terminal fragments, amino terminal fragments and substituted analogues, were chemically synthesized and the structure-activity relationships of the peptides were investigated by comparing their contractile activities on the rat uterus. Peptides with chain lengths of 8 and 9 amino acid residues from the C-terminus of GRP-10 and NMB, respectively, had considerable contractile activities. At position 6 of both decapeptides, Val seems to be more favourable than Thr for inducing contraction of the rat uterus. The substitution of His at position 3 and Leu at position 9 of GRP-10 by Leu and Phe, as in NMB leads to a decrease in activity. Moreover, Trp at position 4 and -Met-NH2 at the C-terminus are essential for activity. Furthermore, in order to characterize the bombesin-receptor profile of rat uterus, the inhibitory effect of two peptide antagonists, [D-Arg1, D-Pro2, D-Trp7,9, Leu11]-substance P and [Leu13-phi (CH2NH)-Leu14]-bombesin on the contraction of rat uterus were examined.