A First-Class Degrader Candidate Targeting Both KRAS G12D and G12V Mediated by CANDDY Technology Independent of Ubiquitination

"Undruggable" targets such as KRAS are particularly challenging in the development of drugs. We devised a novel chemical knockdown strategy, CANDDY (Chemical knockdown with Affinity aNd Degradation DYnamics) technology, which promotes protein degradation using small molecules (CANDDY molecules) that are conjugated to a degradation tag (CANDDY tag) modified from proteasome inhibitors. We demonstrated that CANDDY tags allowed for direct proteasomal target degradation independent of ubiquitination. We synthesized a KRAS-degrading CANDDY molecule, TUS-007, which induced degradation in KRAS mutants (G12D and G12V) and wild-type KRAS. We confirmed the tumor suppression effect of TUS-007 in subcutaneous xenograft models of human colon cells (KRAS G12V) with intraperitoneal administrations and in orthotopic xenograft models of human pancreatic cells (KRAS G12D) with oral administrations. Thus, CANDDY technology has the potential to therapeutically target previously undruggable proteins, providing a simpler and more practical drug targeting approach and avoiding the difficulties in matchmaking between the E3 enzyme and the target.

Effect of the extracellular component of bone marrow mesenchymal stromal cells from healthy donors on hematologic neoplasms and their angiogenesis

Bone marrow mesenchymal stromal cells (BM-MSCs) from healthy donors are a promising source of cell therapy. However, their effectiveness in cancer remains less known. This study is the first to evaluate the quality of BM-MSCs obtained from young and elderly healthy volunteers (KNT cells). The KNT cells had normal karyotypes and were positive for MSC markers (CD90, CD73, CD105). When cultured under appropriate conditions, they showed adipogenic or osteogenic potential. Hence, the anti-neoplastic effects of secretory factors [supernatant or extracellular vesicles (EV)] from KNT cells were verified using several neoplastic cells (three multiple myeloma, three myeloid leukemia, and three lymphoma cell lines). The conditioned medium (CM), but not EV, of KNT cells derived from young healthy donors significantly inhibited myeloma and lymphoma cell proliferation, but enhanced myeloid leukemia proliferation. Anti-angiogenesis effect of CM and EV derived from young KNT against hematologic neoplasia-induced angiogenesis was evident and more prominent in CM than in EV but not evident in elderly KNT-derived EV. These findings indicate that the anti-tumor effect of KNT cells depends on the types of hematologic neoplasia, with elements existing in the supernatant and not in EVs. Therefore, BM-MSC may produce soluble factors that affect cell proliferation of neoplasia, causing cell-to-cell communication. The anti-angiogenesis effect of KNT cells depends on the age of BM-MSC donors.

Downregulation of extracellular vesicle microRNA-101 derived from bone marrow mesenchymal stromal cells in myelodysplastic syndrome with disease progression

To evaluate the mechanism underlying the communication between myeloid malignant and bone marrow (BM) microenvironment cells in disease progression, the current study established BM mesenchymal stromal cells (MSCs) and assessed extracellular vesicle (EV) microRNA (miR) expression in 22 patients with myelodysplastic syndrome (MDS) and 7 patients with acute myeloid leukemia and myelodysplasia-related changes (AML/MRC). Patients with MDS were separated into two categories based on the revised International Prognostic Scoring System (IPSS-R), and EV-miR expression in BM-MSCs was evaluated using a TaqMan low-density array. The selected miRs were evaluated using reverse transcription-quantitative PCR. The current study demonstrated that the expression of BM-MSC-derived EV-miR was heterogenous and based on MDS severity, the expression of EV-miR-101 was lower in high-risk group and patients with AML/MRC compared with the control and low-risk groups. This reversibly correlated with BM blast percentage, with which the cellular miR-101 from BM-MSCs or serum EV-miR-101 expression exhibited no association. Database analyses indicated that miR-101 negatively regulated cell proliferation and epigenetic gene expression. The downregulation of BM-MSC-derived EV-miR-101 may be associated with cell-to-cell communication and may accelerate the malignant process in MDS cells.

A novel non-invasive monitoring assay of 5-azacitidine efficacy using global DNA methylation of peripheral blood in myelodysplastic syndrome

Purpose: Monitoring response and resistance to 5-azacitidine (AZA) is essential when treating patients with myelodysplastic syndrome (MDS). To quantify methylated DNA not only in the promoter region but also in the gene body, we established a single-molecule methylation assay (SMMA).

Patients and methods: We first investigated the methylation extent (expressed as methylation index [MI]) by SMMA among 28 MDS and 6 post-MDS acute myeloid leukemia patients. We then analyzed the MI in 13 AZA-treated patients.

Results: Whole-blood DNA from all 34 patients had low MI values compared with healthy volunteers (P<0.0001). DNA hypomethylation in MDS patients was more evident in neutrophils (P=0.0008) than in peripheral mononuclear cells (P=0.0713). No consistent pattern of genome-wide DNA hypomethylation was found among MDS subtypes or revised International Prognostic Scoring System (IPSS-R) categories; however, we found that the MI was significantly increased for patients at very high risk who were separated by the new cytogenetic scoring system for IPSS-R (P=0.0398). There was no significant difference in MI before AZA, regardless of the response to AZA (P=0.8689); however, sequential measurement of MI in peripheral blood demonstrated that AZA non-responders did not have normalized MI at the time of next course of AZA (P=0.0352).

Conclusion: Our results suggest that sequential SMMA of peripheral blood after AZA may represent a non-invasive monitoring marker for AZA efficacy in MDS patients.

Chromatin Regulation by HP1γ Contributes to Survival of 5-Azacytidine-Resistant Cells

Recent investigations of the treatment for hematologic neoplasms have focused on targeting epigenetic regulators. The DNA methyltransferase inhibitor 5-azacytidine (AZA) has produced good results in the treatment of patients with myelodysplastic syndromes. The mechanism underlying its pharmacological activity involves many cellular processes including histone modifications, but chromatin regulation in AZA-resistant cells is still largely unknown. Therefore, we compared human leukemia cells with AZA resistance and their AZA-sensitive counterparts with regard to the response of histone modifications and their readers to AZA treatment to identify novel molecular target(s) in hematologic neoplasms with AZA resistance. We observed an a decrease of HP1γ, a methylated lysine 9 of histone H3-specific reader protein, in AZA-sensitive cells after treatment, whereas AZA treatment did not affect HP1 family proteins in AZA-resistant cells. The expression of shRNA targeting HP1γ reduced viability and induced apoptosis specifically in AZA-resistant cells, which accompanied with down-regulation of ATM/BRCA1 signaling, indicating that chromatin regulation by HP1γ plays a key role in the survival of AZA-resistant cells. In addition, the amount of HP1γ protein in AZA-sensitive and AZA-resistant cells was decreased after treatment with the bromodomain inhibitor I-BET151 at a dose that inhibited the growth of AZA-resistant cells more strongly than that of AZA-sensitive cells. Our findings demonstrate that treatment with AZA, which affects an epigenetic reader protein and targets HP1γ, or a bromodomain inhibitor is a novel strategy that can be used to treat patients with hematopoietic neoplasms with AZA resistance.

[Construction of a High-precision Chemical Prediction System Using Human ESCs]

　Toxicity prediction based on stem cells and tissue derived from stem cells plays a very important role in the fields of biomedicine and pharmacology. Here we report on qRT-PCR data obtained by exposing 20 compounds to human embryonic stem (ES) cells. The data are intended to improve toxicity prediction, per category, of various compounds through the use of support vector machines, and by applying gene networks. The accuracy of our system was 97.5-100% in three toxicity categories: neurotoxins (NTs), genotoxic carcinogens (GCs), and non-genotoxic carcinogens (NGCs). We predicted that two uncategorized compounds (bisphenol-A and permethrin) should be classified as follows: bisphenol-A as a non-genotoxic carcinogen, and permethrin as a neurotoxin. These predictions are supported by recent reports, and as such constitute a good outcome. Our results include two important features: 1) The accuracy of prediction was higher when machine learning was carried out using gene networks and activity, rather than the normal quantitative structure-activity relationship (QSAR); and 2) By using undifferentiated ES cells, the late effect of chemical substances was predicted. From these results, we succeeded in constructing a highly effective and highly accurate system to predict the toxicity of compounds using stem cells.

Genetic variations of bone marrow mesenchymal stromal cells derived from acute leukemia and myelodysplastic syndrome by targeted deep sequencing

Bone marrow mesenchymal stromal cells (MSCs), which support proliferation and differentiation of hematopoietic stem cells, may play a crucial role in the pathogenesis of myeloid neoplasms. To determine whether MSCs in myeloid neoplasms harbor distinct somatic mutations that may affect their function, we used a targeted gene sequencing panel containing 50 myeloid neoplasm-associated genes with coverage of ≥500. We compared the genetic alterations between MSCs and bone marrow hematopoietic (BM) cells from patients with acute leukemia (n=5) or myelodysplastic syndrome (MDS, n=5). Non-synonymous somatic mutations, such as DNMT3A-R882H and FLT3-D835Y, were only detected in BM cells with high allelic frequency. We found several non-synonymous genetic variants overlapping BM cells and MSCs, including TP53 and ASXL1, partially owing to the heterogenous cell fraction of MSC samples and lineage fidelity. We also found MSC-specific genetic variants with very low allelic frequency (7% to 8%), such as NF1-G2114D and NF1-G140. Further studies in large cohorts are needed to clarify the molecular properties of MSCs including age-related genetic alterations by targeted deep sequencing.

Teriflunomide restores 5-azacytidine sensitivity via activation of pyrimidine salvage in 5-azacytidine-resistant leukemia cells

Previous studies showed that downregulation of pyrimidine salvage underlies resistance against 5-azacytidine (AZA), indicating an important role for de novo pyrimidine synthesis in AZA resistance. Because de novo pyrimidine synthesis is inhibited by the immunomodulator teriflunomide and its pro-drug leflunomide, we examined the effect of combined treatment with AZA and teriflunomide on AZA resistance to develop a novel strategy to cancel and prevent AZA resistance. Teriflunomide markedly inhibited the growth of AZA-resistant human leukemia cell lines (R-U937 and R-HL-60) in comparison with their AZA-sensitive counterparts (U937 and HL-60). In the presence of a non-toxic concentration of teriflunomide (1 μM), AZA induced apoptosis in AZA-resistant cells and leukemia cells from AZA-resistant patients. AZA acted as a DNA methyltransferase 3A inhibitor in AZA-resistant cells in the presence of 1 μM teriflunomide. Although AZA-sensitive cells acquired AZA resistance after continuous treatment with AZA for 42 days, the growth of AZA-sensitive cells continuously treated with the combination of AZA and teriflunomide was significantly inhibited in the presence of AZA, demonstrating that the combined treatment prevented AZA resistance. These results suggest that combined treatment with AZA and teriflunomide can be a novel strategy to overcome AZA resistance.

Prediction of developmental chemical toxicity based on gene networks of human embryonic stem cells

Predictive toxicology using stem cells or their derived tissues has gained increasing importance in biomedical and pharmaceutical research. Here, we show that toxicity category prediction by support vector machines (SVMs), which uses qRT-PCR data from 20 categorized chemicals based on a human embryonic stem cell (hESC) system, is improved by the adoption of gene networks, in which network edge weights are added as feature vectors when noisy qRT-PCR data fail to make accurate predictions. The accuracies of our system were 97.5–100% for three toxicity categories: neurotoxins (NTs), genotoxic carcinogens (GCs) and non-genotoxic carcinogens (NGCs). For two uncategorized chemicals, bisphenol-A and permethrin, our system yielded reasonable results: bisphenol-A was categorized as an NGC, and permethrin was categorized as an NT; both predictions were supported by recently published papers. Our study has two important features: (i) as the first study to employ gene networks without using conventional quantitative structure-activity relationships (QSARs) as input data for SVMs to analyze toxicogenomics data in an hESC validation system, it uses additional information of gene-to-gene interactions to significantly increase prediction accuracies for noisy gene expression data; and (ii) using only undifferentiated hESCs, our study has considerable potential to predict late-onset chemical toxicities, including abnormalities that occur during embryonic development.

Prenatal exposure to permethrin influences vascular development of fetal brain and adult behavior in mice offspring

Pyrethroids are one of the most widely used classes of insecticides and show neurotoxic effects that induce oxidative stress in the neonatal rat brain. However, little is still known about effects of prenatal exposure to permethrin on vascular development in fetal brain, central nervous system development, and adult offspring behaviors. In this study, the effects of prenatal exposure to permethrin on the development of cerebral arteries in fetal brains, neurotransmitter in neonatal brains, and locomotor activities in offspring mice were investigated. Permethrin (0, 2, 10, 50, and 75 mg/kg) was orally administered to pregnant females once on gestation day 10.5. The brains of permethrin-treated fetuses showed altered vascular formation involving shortened lengths of vessels, an increased number of small branches, and, in some cases, insufficient fusion of the anterior communicating arteries in the area of circle of Willis. The prenatal exposure to permethrin altered neocortical and hippocampus thickness in the mid brain and significantly increased norepinephrine and dopamine levels at postnatal day 7 mice. For spontaneous behavior, the standing ability test using a viewing jar and open-field tests showed significant decrease of the standing ability and locomotor activity in male mice at 8 or 12 weeks of age, respectively. The results suggest that prenatal exposure to permethrin may affect insufficient development of the brain through alterations of vascular development.

Abstract 5627: Involvement of pyrimidine metabolism pathway in 5-azacytidine resistance

Background and aim

5-azacytidine (AZA) is a DNA demethylating agent that is clinically used for patients with myelodysplastic syndrome and acute myeloid leukemia. However, the mechanism of AZA-resistance remains unclear although many patients become resistant to AZA after short-term use. To investigate the mechanism of AZA resistance, we established an AZA-resistant cell line and analyzed its cellular and molecular biological characteristics.

Experimental procedures

To establish the AZA-resistant cell line, U937 cells were incubated in a gradually increasing dose of AZA from 0.1 μM to 3 μM. Surviving cells were named R-U937. The profiles of mRNA expression and DNA methylation in U937 and R-U937 cells were obtained and pathway analysis was performed to determine differences between U937 and R-U937. Experiments using specific inhibitors were also performed.

Results

Proliferation and drug resistance of R-U937

R-U937 cells showed a lower proliferation rate than their parent cells, but their viability was not affected by AZA or 2’-deoxy-AZA (DAC).

Role of pyrimidine metabolism pathway in AZA resistance

The pathway analysis of mRNA expression profiles revealed differences between U937 and R-U937 in terms of the mRNA expression level of 4 genes involved in the ‘Pyrimidine Metabolism Pathway’. The observation was confirmed by quantitative RT-PCR. R-U937 cells re-acquired sensitivity to AZA when they were incubated with an inhibitor of CTP synthase. These results indicated that adaptation in pyrimidine metabolism, particularly the accelerated synthesis of CTP from UTP, played important roles in the development of an AZA-resistant phenotype.

Role of DNA hypomethylation in AZA resistance

The DNA demethylation process induced by AZA involves inhibition of DNA methyltransferases (DNMTs) and DNA damage. It is not clear which process is the major mechanism of the anti-leukemia activity. To clarify this, we compared the effects of AZA, DAC and RG108, a DNMT inhibitor with no DNA damaging activity, on viability and DNA damage. AZA and DAC significantly decreased U937 cell viability, but not RG108. U937 incubated with AZA or DAC showed an increased ratio of p-H2AX-positive cells, indicating that these agents caused DNA damage. However, the ratio of p-H2AX-positive cells in U937 incubated with RG108 was equal to that of cells incubated without the agents. In R-U937, all agents did not increase the ratio of p-H2AX-positive cells. The DNA methylation profiles revealed global hypomethylation in R-U937. These results indicated that DNA damage but not DNMT inhibition played a major role in the anti-leukemia activity of AZA and DAC.

Conclusion

The present results showed that the development of an AZA-resistant phenotype of R-U937 depended on the adaptation in pyrimidine metabolism and global DNA hypomethylation. To overcome AZA resistance, pyrimidine metabolism, particularly CTP synthase, can be a good target.

Citation Format: Satoshi Imanishi, Tomohiro Umezu, Chiaki Kobayashi, Kazuma Ohyashiki, Junko Ohyashiki. Involvement of pyrimidine metabolism pathway in 5-azacytidine resistance. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5627. doi:10.1158/1538-7445.AM2013-5627

Effect of low-dose thalidomide on dopaminergic neuronal differentiation of human neural progenitor cells: a combined study of metabolomics and morphological analysis

Thalidomide is increasingly used in anticancer and anti-inflammation therapies. However, it is known for its teratogenicity and ability to induce peripheral neuropathy, although the mechanisms underlying its neurological effect in humans are unclear. In this study, we investigated the effect of thalidomide on the metabolism and neuronal differentiation of human neural progenitor cells. We found that levels of tyrosine, phenylalanine, methionine and glutathione, which are involved in dopamine and methionine metabolism, were decreased following thalidomide treatment. Morphological analysis revealed that treatment with 100 nM thalidomide, which is much lower than clinical doses, significantly decreased the number of dopaminergic (tyrosine hydroxylase-positive) neurons, compared with control cells. Our results suggest that these adverse neurological effects of thalidomide should be taken into consideration prior to its use for the treatment of neurodegenerative and other diseases.

Identification of Stage-Specific Gene Expression Signatures in Response to Retinoic Acid during the Neural Differentiation of Mouse Embryonic Stem Cells

We have previously established a protocol for the neural differentiation of mouse embryonic stem cells (mESCs) as an efficient tool to evaluate the neurodevelopmental toxicity of environmental chemicals. Here, we described a multivariate bioinformatic approach to identify the stage-specific gene sets associated with neural differentiation of mESCs. We exposed mESCs (B6G-2 cells) to 10⁻⁸ or 10⁻⁷ M of retinoic acid (RA) for 4 days during embryoid body formation and then performed morphological analysis on day of differentiation (DoD) 8 and 36, or genomic microarray analysis on DoD 0, 2, 8, and 36. Three gene sets, namely a literature-based gene set (set 1), an analysis-based gene set (set 2) using self-organizing map and principal component analysis, and an enrichment gene set (set 3), were selected by the combined use of knowledge from literatures and gene information selected from the microarray data. A gene network analysis for each gene set was then performed using Bayesian statistics to identify stage-specific gene expression signatures in response to RA during mESC neural differentiation. Our results showed that RA significantly increased the size of neurosphere, neuronal cells, and glial cells on DoD 36. In addition, the gene network analysis showed that glial fibrillary acidic protein, a neural marker, remarkably up-regulates the other genes in gene set 1 and 3, and Gbx2, a neural development marker, significantly up-regulates the other genes in gene set 2 on DoD 36 in the presence of RA. These findings suggest that our protocol for identification of developmental stage-specific gene expression and interaction is a useful method for the screening of environmental chemical toxicity during neurodevelopmental periods.

Effects of methylmercury exposure on neuronal differentiation of mouse and human embryonic stem cells

The establishment of more efficient in vitro approaches has been widely acknowledged as a critical need for toxicity testing. In this study, we examined the effects of methylmercury (MeHg), which is a well-known developmental neurotoxicant, in two neuronal differentiation systems of mouse and human embryonic stem cells (mESCs and hESCs, respectively). Embryoid bodies were generated from gathering of mESCs and hESCs using a micro-device and seeded onto ornithine-laminin-coated plates to promote proliferation and neuronal differentiation. The cells were exposed to MeHg from the start of neuronal induction until the termination of cultures, and significant reductions of mESCs and hESCs were observed in the cell viability assays at 1,10,100 and 1000nM, respectively. Although the mESC derivatives were more sensitive than the hESC derivatives to MeHg exposure in terms of cell viability, the morphological evaluation demonstrated that the neurite length and branch points of hESC derivatives were more susceptible to a low concentration of MeHg. Then, the mRNA levels of differentiation markers were examined using quantitative RT-PCR analysis and the interactions between MeHg exposure and gene expression levels were visualized using a network model based on a Bayesian algorithm. The Bayesian network analysis showed that a MeHg-node was located on the highest hierarchy in the hESC derivatives, but not in the mESC derivatives, suggesting that MeHg directly affect differentiation marker genes in hESCs. Taken together, effects of MeHg were observed in our neuronal differentiation systems of mESCs and hESCs using a combination of morphological and molecular markers. Our study provided possible, but limited, evidences that human ESC models might be more sensitive in particular endpoints in response to MeHg exposure than that in mouse ESC models. Further investigations that expand on the findings of the present paper may solve problems that occur when the outcomes from laboratory animals are extrapolated for human risk evaluation.

Multi-parametric profiling network based on gene expression and phenotype data: a novel approach to developmental neurotoxicity testing

The establishment of more efficient approaches for developmental neurotoxicity testing (DNT) has been an emerging issue for children’s environmental health. Here we describe a systematic approach for DNT using the neuronal differentiation of mouse embryonic stem cells (mESCs) as a model of fetal programming. During embryoid body (EB) formation, mESCs were exposed to 12 chemicals for 24 h and then global gene expression profiling was performed using whole genome microarray analysis. Gene expression signatures for seven kinds of gene sets related to neuronal development and neuronal diseases were selected for further analysis. At the later stages of neuronal cell differentiation from EBs, neuronal phenotypic parameters were determined using a high-content image analyzer. Bayesian network analysis was then performed based on global gene expression and neuronal phenotypic data to generate comprehensive networks with a linkage between early events and later effects. Furthermore, the probability distribution values for the strength of the linkage between parameters in each network was calculated and then used in principal component analysis. The characterization of chemicals according to their neurotoxic potential reveals that the multi-parametric analysis based on phenotype and gene expression profiling during neuronal differentiation of mESCs can provide a useful tool to monitor fetal programming and to predict developmentally neurotoxic compounds.

Differentially expressed genes in silkworm cell cultures in response to infection by Wolbachia and Cardinium endosymbionts

Wolbachia and Cardinium are bacterial endosymbionts that are widely distributed amongst arthropods. Both cause reproductive alterations, such as cytoplasmic incompatibility, parthenogenesis and feminization. Here we studied differentially expressed genes in Wolbachia- and Cardinium-infected Bm-aff3 silkworm cells using a silkworm microarray. Wolbachia infection did not alter gene expression or induce or suppress immune responses. In contrast, Cardinium infection induced many immune-related genes, including antimicrobial peptides, pattern recognition receptors and a serine protease. Host immune responses differed, possibly because of the different cell wall structures of Wolbachia and Cardinium because the former lacks genes encoding lipopolysaccharide components and two racemases for peptidoglycan formation. A few possibly non-immune-related genes were differentially expressed, but their involvement in host reproductive alteration was unclear.

Lipopolysaccharide elicits expression of immune-related genes in the silkworm, Bombyx mori

Lipopolysaccharide (LPS), a major cell wall component of gram-negative bacteria, was found to be unable to activate immune-related genes in Drosophila melanogaster. In contrast, highly purified LPS elicited immune-related gene expression in the fat body of Bombyx mori. However, the level of activation by highly purified LPS was lower than crude LPS and peptidoglycan. Furthermore, synthetic lipid A also activated these genes, suggesting that B. mori possesses unknown signal pathways to activate immune-related genes by LPS. Up-regulation of antimicrobial peptide genes by highly purified LPS was not confirmed in the immune-responsive cell line, NIAS-Bm-aff3, suggesting that some factors necessary for signal transduction activated by LPS are deficient in this cell line.

Development and characterization of a continuous cell line, AFKM-On-H, from hemocytes of the European corn borer Ostrinia nubilalis (Hübner) (Lepidoptera, Pyralidae)

The corn borer, Ostrinia nubilalis, is a very important pest in different countries, and the in vitro system of the insect could be a useful tool for isolation and characterization of the pathogens and physiological responses of the insect. In this context, a cell line was derived from the hemocytes of the European corn borer and was named AFKM-On-H for, respectively, O. nubilalis, Armand Frappier, King Mongkut Institutes, and Hemocytes. This cell line was initiated and maintained in Ex-Cell 400 medium supplemented with 10% heat-inactivated fetal bovine serum. The cells, mostly spherical in shape, not firmly attached to the plastic culture flasks, were passaged up to 200 times by repeated gentle pipetting of the cells. The doubling times at the 80th and 125th passages at 28 degrees C and at the 122th and 169th passages at 25 degrees C were 40, 29, 35, and 34 h, respectively. The AFKM-On-H cell line was further characterized by the morphology, karyotype, random amplified polymorphic DNA analysis, and isozyme profiles. Susceptibility of the cell line to cytoplasmic polyhedrosis viruses (CPV) Euxoa scandens (EsCPV), Dendrolimus punctatus (DpCPV), and Choristoneura fumiferana (CfCPV); nuclear polyhedrosis viruses [Autographa californica (AcMNPV) wild type and recombinant, Antherea yammamai (AnyaNPV)]; and Chilo iridescent virus was demonstrated. Relative sensitivities of the cell line to Bacillus thuringiensis and Metarhizium anisopliae toxins and effects of the molting hormone 20-hydroxyecdysone on this new hemocyte cell line were characterized.

Changes in Expression and Localization of GPRC5B and RAR.ALPHA. in the Placenta and Yolk Sac During Middle to Late Gestation in Mice

The mRNA expression of GPRC5B, an orphan G protein-coupled receptor, is induced by retinoic acid (RA). Because RA plays critical roles in embryonic development, reproductive functions, metabolism and homeostasis, GPRC5B is also considered crucial in these physiological events. We investigated the changes in expression of GPRC5B and RA receptor (RAR) alpha mRNAs and immunohistochemical localization of their proteins in the murine placenta and yolk sac at 13.5, 15.5 and 17.5 days post coitus. Stable levels of GPRC5B and RARalpha mRNAs were detected in the placenta and yolk sac. In the placenta, GPRC5B was present in maternal and fetal vascular endothelial cells, stromal cells, fibroblast-like cells and glycogen cells. A strong reaction to RARalpha was detected in maternal and fetal vascular endothelial cells and stromal cells. The levels of GPRC5B and RARalpha proteins in maternal and fetal vascular endothelial cells decreased with gestation. In the yolk sac, GPRC5B and RARalpha proteins were detected in vascular endothelial cells, but their levels did not change during the gestation period. These findings indicate that GPRC5B is involved in RA-dependent morphogenesis/angiogenesis and regulation of extracellular matrix synthesis in the murine placenta and yolk sac.

Effects of Exposure In Utero to Bisphenol A on the Expression of Aryl Hydrocarbon Receptor, Related Factors, and Xenobiotic Metabolizing Enzymes in Murine Embryos

To evaluate the effects of bisphenol A (BPA), a candidate endocrine disruptor (ED), on embryonic development, we examined the mRNA expression levels of the aryl hydrocarbon receptor (AhR; which binds with many EDs and plays crucial roles in their metabolism) and related factors [aryl hydrocarbon receptor repressor (AhRR) and AhR nuclear translocator (Arnt)], xenobiotic metabolizing enzymes [XMEs; cytochrome P450 1A1 (CYP1A1) and UDP-glucuronosyltransferase, and the glutathione S-transferase Ya subunit (GST)], in murine embryos exposed in utero to BPA (0.02, 2, 200, and 20,000 microg/kg/day) and 17beta-estradiol (E2; 5 microg/kg/day, used as a positive control) at 6.5-13.5 or 6.5-17.5 days post coitum (dpc) using the quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) method. Protein levels of CYP1A1 and GST in embryonic livers were estimated by Western immunoblotting. Exposure in utero to BPA [0.02 (1/100 dose of environmental exposure), 2, 200, and 20,000 microg/kg/day] increased AhR mRNA expression in the cerebra, cerebella, and gonads (testes and ovaries) of male and female mid-and late-developmental stage (14.5- and 18.5-dpc, respectively) embryos. BPA dose-independently up-regulated the expression of AhRR and Arnt in mid- and late-stage embryos. BPA had no remarkable effect on the mRNA levels of XMEs in mid-stage embryos, but dose-dependently up-regulated the expression in late-stage embryos. Moreover, the protein levels of these enzymes in the livers of late-stage embryos were increased. The present findings revealed that exposure to BPA in utero disrupts the expression of AhR and related factors and of xenobiotic metabolizing enzymes, and that mid-stage embryos, in the organogenic stage, are sensitive to BPA.

Effects of In Utero Exposure to Bisphenol A on mRNA Expression of Arylhydrocarbon and Retinoid Receptors in Murine Embryos

To evaluate the effects of bisphenol A (BPA), a candidate endocrine disruptor (ED), on embryonic development, we examined the mRNA expression levels of the arylhydrocarbon receptor (AhR), which binds with many EDs and plays crucial roles in xenobiotic metabolism, and of the retinoic acid receptor (RAR) alpha and retinoid X receptor (RXR) alpha, key factors in nuclear receptor-dependent retinoid signal transduction, in murine embryos exposed in utero to BPA (0.02, 2, 200, and 20,000 microg/kg/day) at 6.5-13.5 or 6.5-17.5 days post coitum (dpc), using the real-time reverse transcription-polymerase chain reaction (RT-PCR) method. Extremely low-dose BPA (0.02 microg/kg/day; 1/100 the dose of environmental exposure) remarkably increased AhR mRNA expression in the cerebra, cerebella, and gonads (testes and ovaries) of male and female 14.5- and 18.5-dpc-embryos. In utero exposure to BPA at 2, 200, and 20,000 microg/kg/day also increased levels of AhR mRNA. In gonads of 14.5-dpc-embryos, AhR mRNA levels were elevated and showed diphasic (U) dose-response curves following exposure to BPA, but inverted U dose-response curves were obtained for 18.5-dpc-embryos. Exposure to BPA increased expression levels of RARalpha and RXRalpha mRNAs in the cerebra, cerebella, and gonads of male and female 14.5- and 18.5-dpc-embryos. Extremely low-dose BPA (0.02 microg/kg/day) increased RARalpha mRNA expression in the cerebella of male and female 14.5- and 18.5-dpc-embryos and in the gonads of female 14.5-dpc-embryos, and significantly increased RXRalpha mRNA expression in the cerebra and cerebella of male and female 14.5-dpc-embryos. The present findings confirm that in utero exposure to an extremely low dose of BPA up-regulates the mRNA expression of AhR, RARalpha, and RXRalpha in murine embryos and disrupts the receptor-dependent signal transducing systems, and will contribute to the assessment of the toxic effects of BPA on xenobiotic metabolism and retinoid signals in embryogenesis.

Effects of in utero exposure to bisphenol A on expression of RARalpha and RXRalpha mRNAs in murine embryos

Retinoic acid receptor (RAR) alpha and retinoid X receptor (RXR) alpha are key factors in a nuclear receptor-dependent signal. To evaluate the effects of bisphenol A (BPA), a candidate endocrine disruptor (ED), on embryonic development, we examined the mRNA levels of RARalpha and RXRalpha in murine embryos, exposed in utero to BPA (2 microg/kg/day) at 6.5-17.5 days post-coitum (dpc), by the real-time reverse transcription-polymerase chain reaction (RT-PCR) method. Higher levels of RARalpha mRNA in cerebra of male and female embryos of control groups were detected at 14.5 dpc. In utero BPA reduced the RARalpha mRNA expression. Higher levels of RXRalpha mRNA in cerebra of male and female embryos were seen at 12.5 dpc. The exposure decreased RXRalpha mRNA expression in male but not female embryos. No remarkable change in the RARalpha mRNA expression level was noted in cerebella of male or female embryos of the control group during embryonic development. Exposure to BPA increased expression levels of RARalpha mRNA in cerebella of male and female embryos at 12.5 dpc. Higher levels of RXRalpha mRNA in cerebella of male and female embryos were seen, but no remarkable changes were noted during embryonic development. BPA significantly decreased the expression levels of RXRalpha mRNA in cerebella of female embryos at 12.5, 14.5 and 18.5 dpc. RARalpha and RXRalpha mRNAs were expressed in gonads (testes and ovaries) of murine embryos from 12.5 to 18.5 dpc. In utero exposure to BPA decreased levels of RARalpha mRNA in testes of 14.5- and 18.5-dpc-embryos, levels of RXRalpha mRNA in testes of 14.5-dpc-embryos, and levels of RXRalpha mRNA in ovaries of 14.5-dpc-embryos. The present findings indicate that RARalpha and RXRalpha play crucial roles in organogenesis, and the growth and development of murine embryos, and will contribute to the assessment of the toxic effects of BPA on retinoid signals in embryogenesis.

Effects of oral exposure of bisphenol A on mRNA expression of nuclear receptors in murine placentae assessed by DNA microarray

Bisphenol A (BPA), a candidate endocrine disruptor (ED), is considered to bind to estrogen receptors and to regulate expressions of estrogen responsive genes. It has also shown evidence of affecting the reproductive, immunological and nervous systems of mammalian embryos. However, the effects of BPA on placentae, a central organ of feto-maternal interlocution, are still unclear. To reveal the mechanisms of BPA effects on placentae in mammals, we compared the mRNA expression of 20 nuclear receptors between placentae of vehicle controls and those of orally BPA exposed pregnant mice by a DNA microarray technique. In murine placentae, mRNAs of 11 nuclear receptors were not detected. However, greater than 1.5 fold changes in mRNA expression of nine nuclear receptors between vehicle control and BPA treated mice were noted. Moreover, remarkable changes in mRNA expression of six non-nuclear receptor proteins were induced by BPA exposure. There were various differences in the effects of BPA on the expression of these mRNAs between the placentae with male embryos and those with female embryos. Such embryo-sex dependent differences are interesting and important pointers to understanding of the endocrine disrupting effect of BPA. The present data indicate that BPA affects the expression of nuclear receptor mRNAs in placentae and may disrupt the physiological functions of placentae.

Availability of NMR microscopic observation of mouse embryo disorder: examination in malformations induced by maternal administration of retinoic acid

Nuclear magnetic resonance (NMR) microscopy is a magnetic resonance imaging method with enhanced spatial resolution due to the use of a high static magnetic field and high magnetic field gradients. It is considered to be a useful tool for non-invasive and continuous investigation of tissue and organs at the histological level. In this study, we applied NMR microscopy to assessment of morphology in mouse embryos using a developmental disorder model induced by retinoic acid administration. Pregnant mice were given 50 mg/kg all-trans retinoic acid at 8.5 dpc. Embryos were collected at several time points after treatment and examined by NMR microscopy after fixation. Two-dimensional and three-dimensional spin echo sequences were used. Tissue contrast on two-dimensional images changed according to length of repetition time and echo time, and also to developmental stage of embryos. Two-dimensional and three-dimensional images nondestructively demonstrated defects in development of the skeleton and soft tissue, e.g. hypoplasia of vertebrae in the lumbar and tail regions and dysplasia of the spinal cord, in embryos exposed to retinoic acid. These morphological abnormalities were confirmed by conventional assessment after imaging. Although further improvements are required, NMR microscopy will provide a new approach for multi-parameter assessment of embryonic development under physiological and pathological conditions.

Activation of background membrane conductance by the tyrosine kinase inhibitor tyrphostin A23 and its inactive analog tyrphostin A1 in guinea pig ventricular myocytes

ABSTRACT-The effects of the tyrosine kinase (TK) inhibitor tyrphostin A23 and its inactive analog tyrphostin Al on background membrane conductance were investigated in guinea pig ventricular myocytes. TK-inhibiting A23 reversibly increased membrane conductance under conditions designed to minimize Na+, Ca2+, K+, and Na+-K+ pump currents. Similar stimulatory action was obtained with TK-inactive Al. The tyrphostin-induced current was inhibited by omitting external Na+ or Ca+, suppressed by chelating internal Ca2+, blocked by external Cd2+ and Ni2+, and insensitive to changes in internal Cl- concentration. We conclude that tyrphostins have a direct, TK-independent action that increases membrane conductance probably by stimulating Na+-Ca2+ exchange.

Establishment and characterization of cell-free translation/glycosylation in insect cell (Spodoptera frugiperda 21) extract prepared with high pressure treatment

A coupled cell-free translation/glycosylation system, prepared from Spodoptera frugiperda insect cells, was established and optimized for protein production and glycosylation efficiency. Both translation and glycosylation were stimulated by addition of Mg2+, K+, ATP, GTP, creatine kinase and creatine phosphate, suggesting that glycoprotein productivity is largely determined by translation efficiency. However, high concentrations of creatine phosphate significantly inhibited translation. Spermidine stimulated both translation and glycosylation, but glycosylation required higher concentrations of spermidine than translation. Furthermore, extracts prepared at a nitrogen pressure of 10 kg/cm2 with the Mini-Bomb cell disruption chamber had the highest glycoprotein productivity; and extracts prepared at the higher nitrogen pressure of 15 kg/cm2 retained glycosylation ability. While extracts prepared with the Potter-Elvehjem homogenizer could mediate translation, no glycosylation was achieved. This indicated that the posttranslational machinery might survive disruption by high pressure, but not by physical shearing force. This insect cell-free system was able to synthesize approximately 25 microg of glycosylated gp120/ml of reaction mixture.

Sequence analysis of Pns11, a nonstructural protein of rice gall dwarf virus, and its expression and detection in infected rice plants and vector insects

The nucleotide sequence of genome segment S11 of rice gall dwarf virus (RGDV), a member of Phytoreovirus, was determined. The segment encodes a putative protein of 40 kDa that exhibits approximately 37% homology at the amino acid level to the nonstructural proteins Pns10 of rice dwarf and wound tumor viruses, which are other members of Phytoreovirus. A band of a protein with an apparent molecular mass of 40 kDa was specifically detected in an analysis of cells transfected with S11 cDNA. An antiserum raised against this protein reacted with a protein of approximately 40kDa after fractionation by SDS-PAGE of materials prepared from infected plants and from viruliferous vector insects. However, the antiserum did not react with purified viral proteins. These results suggest that S11 encodes a nonstructural protein of RGDV. This protein was named Pns11.

Differential level in co-down-modulation of CD4 and CXCR4 primed by HIV-1 gp120 in response to phorbol ester, PMA, among HIV-1 isolates

HIV-1 enters cells through interacting with cell surface molecules such as CD4 and chemokine receptors. We generated recombinant soluble gp120s derived from T-cell line-tropic (T-tropic) and macrophage-tropic (M-tropic) HIV-1 strains using a baculovirus expression system and investigated the association of CD4-gp120 complex with the chemokine receptor and/or other surface molecule(s). For monitoring the co-down-modulations of the CD4-gp120 complex, a cytoplasmic domain deletion mutant (tailless CD4), which is not capable of undergoing down-modulation by itself in response to phorbol ester PMA, was used. Our studies revealed both cell-type and HIV-1 strain-specific differences. We found that T-tropic gp120s were capable of priming co-down-modulation with tailless CD4 by interacting with CXCR4, whereas M-tropic SF162 gp120 could not after PMA treatment even in the presence of CCR5. Among the T-tropic HIV-1 envelopes, IIIB gp120 was the most potent. Furthermore, the ability of gp120 to prime the PMA induced co-down-modulation of tailless CD4 appeared to be dependent on the concentration of the principal coreceptor CXCR4. Nevertheless, the observation that IIIB gp120 strongly primed tailless CD4 co-down-modulation on human osteosarcoma HOS cells that express undetectable levels of surface CXCR4 raised the possibility that membrane component(s) other than those recently identified can be involved in down-modulation of the CD4/gp120 complexes.

Peroral infectivity of non-occluded viruses of Bombyx mori nucleopolyhedrovirus and polyhedrin-negative recombinant baculoviruses to silkworm larvae is drastically enhanced when administered with Anomala cuprea entomopoxvirus spindles

Non-occluded viruses (NOVs) of Bombyx mori nucleopolyhedrovirus (BmNPV) are poorly infectious to silkworm larvae when administered by peroral inoculation, although they are highly infectious when injected into the insect haemocoel. In the present study, it is demonstrated that NOVs of BmNPV became highly infectious even through peroral inoculation when administered with spindles (proteinaceous structures) of Anomala cuprea entomopoxvirus (AcEPV). Marked enhancement of peroral infectivity of NOVs by AcEPV spindles (nearly 1000-fold higher in the strongest case) was observed in all growth stages of silkworm larvae tested (2nd to 5th instar). Similarly, peroral infectivity of polyhedrin-negative recombinants of BmNPV, which do not produce polyhedra, was also enhanced remarkably by AcEPV spindles. In contrast, spheroids (proteinaceous structures containing AcEPV virions) did not enhance the peroral infectivity of either NOVs or the recombinant BmNPV in silkworm larvae.

A novel cell-free translation/glycosylation system prepared from insect cells

A cell-free translation/glycosylation system derived from lepidopteran (Sf21) cells, which are widely used to express high yields of foreign active proteins that have post-translational modifications, was constructed. The insect cell extract was prepared using a Mini-Bomb cell disruption chamber by nitrogen pressure treatment, which stably retains translational and post-translational components. The gp120 mRNA was transcribed from the human immunodeficiency virus type-1 envelope glycoprotein gp120 gene with T7 RNA polymerase. When the gp120 mRNA was translated in the insect cell-free system, gp120 having a molecular mass of 100 kDa was detected by Western blot analysis. Synthesized gp120 and gp120 expressed in the intracellular fraction of recombinant-baculovirus-infected Sf21 cells had the same molecular mass, and they both had reduced mobility compared with gp120 secreted by recombinant baculovirus-infected Sf21 cells. In contrast, the 56-kDa gp120 protein, which corresponds to the polypeptide backbone of gp120, was synthesized in wheat germ and rabbit reticulocyte systems. The molecular mass of synthesized gp120 decreased from 100 kDa to 61 kDa after endoglycosidase H treatment, indicating that synthesized gp120 had been glycosylated with N-linked oligosaccharides. Furthermore, glycosylated gp120 was bound to human CD4 molecules expressed on the surface of quail cells. These results revealed that the insect cell-free system can synthesize gp120 that is folded in the proper conformation to provide a CD4-binding domain.

Aspirin and salicylic acid do not inhibit methyl jasmonate-inducible expression of a gene for ornithine decarboxylase in tobacco BY-2 cells

Similar to the prostanoid-mediated inflammatory response in mammals, jasmonate-mediated wound response in plant leaves is inhibited by salicylic acid (SA) or acetylsalicylate (aspirin). In tobacco BY-2 cells, expression of the gene for ornithine decarboxylase (ODC) involved in putrescine synthesis is rapidly inducible by methyl jasmonate (MeJA). A nuclear gene for ODC isolated from tobacco, gNtODC-1, was an intron-less gene and MeJA induced the expression of a GUS fusion gene with the gNtODC-1 promoter in transformed tobacco cells. Although SA alone did not induce the expression, 0.2 to 20 microM SA increased the MeJA-induced expression of the fusion gene to about two-fold. A similar increase was observed with aspirin but not with 3- or 4-hydroxybenzoic acids. SA at concentrations up to 200 microM did not inhibit the MeJA-induction of mRNAs for the GUS fusion gene and the endogenous gene for ODC.

Mechanisms of cation permeation in cardiac sodium channel: description by dynamic pore model

The selective permeability to monovalent metal cations, as well as the relationship between cation permeation and gating kinetics, was investigated for native tetrodotoxin-insensitive Na-channels in guinea pig ventricular myocytes using the whole-cell patch clamp technique. By the measurement of inward unidirectional currents and biionic reversal potentials, we demonstrate that the cardiac Na-channel is substantially permeable to all of the group Ia and IIIa cations tested, with the selectivity sequence Na(+) >/= Li(+) > Tl(+) > K(+) > Rb(+) > Cs(+). Current kinetics was little affected by the permeant cation species and concentrations tested (</=160 mM), suggesting that the permeation process is independent of the gating process in the Na-channel. The permeability ratios determined from biionic reversal potentials were concentration and orientation dependent: the selectivity to Na(+) increased with increasing internal [K(+)] or external [Tl(+)]. The dynamic pore model describing the conformational transition of the Na-channel pore between different selectivity states could account for all the experimental data, whereas conventional static pore models failed to fit the concentration-dependent permeability ratio data. We conclude that the dynamic pore mechanism, independent of the gating machinery, may play an important physiological role in regulating the selective permeability of native Na-channels.

Expression patterns of two genes for the delta-subunit of mitochondrial F1-ATP synthase from sweet potato in transgenic tobacco plants and cells

Two nuclear genes, F1 delta-1 and F1 delta-2, coding for the delta-subunit of mitochondrial F1-ATP synthase, which corresponds to oligomycin-sensitivity conferring protein in animal and yeast mitochondria, were isolated from sweet potato. The gene for the delta-subunit was composed of 6 exons and these two genes shared high sequence similarities to each other not only in exons but also in introns and in the 5'-upstream regions. However, the 5'-upstream regions of F1 delta-1 and F1 delta-2 were distinguishable by the presence of novel sequences, designated Ins-1 and Ins-2, respectively. Ins-1 and Ins-2 contained a terminal direct repeat of 10 bp and 12 bp, respectively, and various forms of repeat sequences. The promoter fusion of both F1 delta-1 and F1 delta-2 with the GUS coding sequence gave expression of GUS activity in transformed tobacco BY-2 cells, although the levels of GUS activity and the patterns of expression during the growth of cells were different between the two. In transgenic tobacco plants, the two fusion genes showed similar levels of expression in leaves and stems, while F1 delta-2:GUS gave significantly higher levels of expression in roots than F1 delta-1:GUS. Deletion of Ins-1 from the 5'-upstream region of F1 delta-1:GUS did not affect the expression of the fusion gene in various organs of transgenic plants. However, it caused significant enhancement of expression in transformed tobacco BY-2 cells.

Differential induction by methyl jasmonate of genes encoding ornithine decarboxylase and other enzymes involved in nicotine biosynthesis in tobacco cell cultures

A cDNA of tobacco BY-2 cells corresponding to an mRNA species which was rapidly induced by methyl jasmonate (MeJA) in the presence of cycloheximide (CHX) was found to encode ornithine decarboxylase (ODC). Another cDNA from a MeJA-inducible mRNA encoded S-adenosylmethionine synthase (SAMS). Although these enzymes could be involved in the biosynthesis of polyamines, the level of putrescine, a reaction product of ODC, increased slowly and while the levels of spermidine and spermine did not change following treatment of cells with MeJA. However, N-methylputrescine, which is a precursor of pyrrolidine ring of nicotine, started to increase shortly after MeJA-treatment of cells and the production of nicotine occured thereafter. The levels of mRNA for arginine decarboxylase (ADC), an alternative enzyme for putrescine synthesis, and that for S-adenosylmethionine decarboxylase (SAMDC), required for polyamine synthesis, were not affected by MeJA. In addition to mRNAs for ODC and SAMS, mRNA for putrescine N-methyltransferase (PMT) was also induced by MeJA. Unlike the MeJA-induction of ODC mRNA, MeJA-induction of SAMS and PMT mRNAs were blocked by CHX. The level of ODC mRNA declined after 1 to 4 h following MeJA treatment, while the levels of mRNAs for SAMS and PMT continued to increase. Auxin significantly reduced the MeJA-inducible accumulation of mRNAs for ODC, SAMS and PMT. These results indicate that MeJA sequentially induces expression of a series of genes involved in nicotine biosynthesis by multiple regulatory mechanisms.

Effect of sulfhydryl oxidoreduction on permeability of cardiac tetrodotoxin-insensitive sodium channel

Effects of sulfhydryl oxidizing and reducing agents on permeability of the tetrodotoxin (TTX)-insensitive Na-channel were investigated in guinea-pig ventricular myocytes using the whole-cell patch-clamp technique. Mercury chloride (HgCl2) at 1-100 microM irreversibly blocked Na+ currents with no significant changes in the gating kinetics. In contrast, the hydrophilic sulfhydryl oxidizing agent, thimerosal at 50-100 microM little affected Na+ permeation through the Na-channel. The Hg2+-induced block of Na+ current could be readily reversed by 1,4-dithiothreitol (DTT), an agent that reduces disulfide bonds. These results indicate that the formation of sulfur-Hg-sulfur bridge is essential for Hg2+ block. Pretreatment with DTT prevented the Hg2+ block of Na+ current, whereas Zn2+ and Cd2+ retained their abilities to block Na+ current after DTT treatment. An application of Zn2+ or Cd2+ resulted in the restoration of Hg2+ sensitivity of the DTT-treated channel. A conformational model for the Na-channel with multiple free sulfhydryl groups and native disulfide bonds could account for our experimental data regarding the effects of sulfhydryl modifying agents on the channel permeability. We conclude that the cardiac TTX-insensitive Na-channel contains functionally important free sulfhydryl groups and disulfide bonds which are accessible from the extracellular side by an aqueous pathway. These sulfhydryls would be capable of modulating the Na-channel permeability by affecting the conformation of channel pore region.

Brain potentials associated with eye fixations during visual tasks under different lighting systems

The variations of eye fixation related potentials (EFRPs) were examined in two tasks under three lighting conditions for assessment of lighting environments. Sixteen subjects participated in two tasks; a difficult and an easy reading task under three lighting conditions: Spot light (S), General light (G) and Mixed light (M). EEG (Oz) and EOG were recorded. EEG epochs time-locked to onset of eye fixations were collected at random and averaged separately in two arrays to obtain a pair of EFRPs. Two wave forms under the S were similar, although those under the G showed the disparity, the largest disparity being in the easy task under the G. Under the S, wave forms of EFRPs were stable in the difficult task. The amplitude changed with the task load. The results suggested that EFRPs might be an index of the work load under lighting conditions.

An mRNA of tobacco cell, which is rapidly inducible by methyl jasmonate in the presence of cycloheximide, codes for a putative glycosyltransferase

Two-dimensional gel electrophoretic display of polypeptides labeled in vivo and those synthesized in vitro from poly(A)(+)-RNA indicated that treatment of cultured cells of tobacco (Nicotiana tabacum) BY-2 with methyl jasmonate (MeJA) induces accumulation of a limited number of specific mRNAs within a few hours. The MeJA-induction of most of these mRNAs was inhibited by cycloheximide (CHX). Six MeJA-inducible cDNAs identified by differential screening were classified into three groups based on the sensitivity of their induction to CHX. Induction of group I mRNAs by MeJA occurred earlier than the induction of other mRNAs and it was not inhibited by CHX. The induction of group II mRNAs by MeJA was blocked by CHX, while group III mRNAs were induced by CHX alone. One group I cDNA was found to encode a putative protein, JIGT, homologous to UDP-sugar glycosyltransferases previously characterized from several plant species. JIGT was structurally different from a putative glycosyltransferase that is rapidly inducible by salycylic acid (SA) in BY-2 cells. JIGT mRNA was not induced by SA. In addition to MeJA, as little as 10(-9) M coronatine induced JIGT mRNA. A sequence highly homologous to JIGT is present as a single copy in the genomes of Nicotiana sylvestris and N. tomentosiformis. The MeJA-inducible production of JIGT may be involved in sugar-conjugation of an unknown substrate in a defensive response and expression of the gene for JIGT in BY-2 cells might serve as a good model system for disecting molecular events occurring in JA-inducible gene expression.

A major jasmonate-inducible protein of sweet potato, ipomoelin, is an ABA-independent wound-inducible protein

Treatment of sweet potato plants cultured in vitro with a vapor of methyl jasmonate (MeJA) induced an accumulation in leaves of a large amount of protein with an apparent molecular mass of 18 kDa. This protein, designated ipomoelin, was purified, and the amino acid sequences of proteolytic fragments were determined. Screening a cDNA library of MeJA-treated leaves by oligonucleotide probes designed from the peptide sequences identified a clone that could code for a polypeptide with 154 amino acids. The deduced amino acid sequence of ipomoelin showed an overall amino acid identity of 25% with the salt-inducible SalT protein of rice. In addition, the C-terminal 70 amino acid sequence of ipomoelin showed about 50% identity with the C-terminal amino acid sequences of seed lectins from Moraceae. The gene for ipomoelin was present in a few copies in the genome of sweet potato. The mRNA for ipomoelin was detected in leaves and petioles, but not in stems and tuberous roots, of sweet potato plants grown in the field. Mechanical wounding of leaves induced ipomoelin mRNA both locally and systemically, while treatment of leaves with ABA, salt, or a high level of sucrose did not induce ipomoelin mRNA. By contrast, ABA-inducible mRNA for sporamin was not induced by MeJA. These results suggest that ipomoelin is involved in defensive reactions of leaves in response to wounding and that JA-mediated wound-induction of ipomoelin occurs independently of ABA.

Diverse inotropic effects of 5-hydroxytryptamine in heart muscles of various mammalian species

The inotropic effects of 5-hydroxytryptamine (5-HT) on mammalian heart muscles were investigated. 5-HT (10(-8)-10(-3)M) produced increases in the contractile tension of atrial and ventricular muscles isolated from guinea pigs, Japanese monkeys, and humans, but not in rat heart preparations. The maximum percent increase of contraction was largest in guinea pig ventricular muscles (142.0 percent), followed by monkey atrium (86.3 percent), human atrium (71.7 percent), guinea pig atrium (48.7 percent), and monkey ventricle (30.1 percent). The sensitivity to 5-HT, measured as the negative logarithm of the half-maximal inotropic molar contractions of 5-HT, i.e., -logEC(50), was highest in the human atrium (6.65 +/- 0.20), followed by guinea pig atrium (5.53 +/- 0.36), monkey ventricle (4.83 +/- 0.28), guinea pig ventricle (4.56 +/- 0.11), and monkey atrium (4.46 +/- 0.16). The inotropic effects of 5-HT seen in the atrial and ventricular muscles of guinea pigs were abolished in the presence of the beta-receptor blocker, pindolol (8 mu M), while these effects in human atrial muscles and monkey atrial and ventricular muscles were abolished only in the presence of both pindolol (8 mu M) and of prazosin (1 mu M), an alpha(1)-receptor blocker. 5-HT increased the V(max) of the slow response recorded from guinea pig ventricular muscles exposed to high K+ (27 mM) media, whereas this agent did not alter the calcium current of isolated guinea pig ventricular myocytes devoid of sympathetic nerve terminals. In reserpinized guinea pig hearts, 5-HT exerted no inotropic effect on ventricular muscle, yet it had an inotropic effect in the atrial muscle, although the latter effect was considerably depressed, compared to that seen in non-reserpinized atrial muscles. We conclude that the positive inotropic effects of 5-HT observed in the ventricular muscle of the guinea pig and in the atrial and ventricular muscles of the Japanese monkey can be attributed to the release of noradrenaline from sympathetic nerve terminals (indirect effect). In contrast, in human atrial muscles, the positive inotropic effect of 5-HT was apparently the result of stimulation of a specific membrane receptor for 5-HT (direct effect). In guinea pig atrial muscles, both direct and indirect effects of 5-HT were involved in the positive inotropism. An explanation for the lack of sensitivity of rat atrial and ventricular muscles to 5-HT awaits further studies.

Hyperpolarization induced by sodium removal in rabbit sinoatrial node cells. Possible role of electrogenic sodium-calcium exchange

Spontaneously active rabbit sinoatrial node (SAN) cells were bathed in K-free solution or in K-free ouabain (20 microM)-containing solution to depress the electrogenic Na(+)-K+ pump activity. In SAN cells exposed to K-free solution, the automatic action potentials ceased with gradual depolarization, followed by an eventual steady-state membrane potential of -32 +/- 1 mV. Under conditions where the Na(+)-K+ pump was blocked, removal of external Na+ produced a large and rapid hyperpolarization in the membrane potential and the membrane was hyperpolarized by 23 +/- 0.5 mV. When the external Na+ was lowered, Na+ was replaced by Li+. The Na-free hyperpolarization was not affected by applications of verapamil (4 microM), lidocaine (1 mM), and quinidine (50 microM), but was inhibited by either quinacrine (50 microM) or Cd2+ (10 mM), which are blockers of Na(+)-Ca2+ exchange. In the absence of external K+, replacement of external NaCl by sucrose produced a hyperpolarization similar to that seen in the replacement of external Na+ by Li+. In the K-free ouabain (20 microM)-containing solution, removal of external Na+ also produced a hyperpolarization, and the membrane potential dropped from -29 +/- 1 to -48 +/- 1 mV. The intracellular acidification due to NH4Cl removal after exposure to NH4Cl (20 mM) produced a decrease in Na-free hyperpolarization, which in the presence of ouabain was inhibited by the application of Cd2+ (10 mM). Removal of external Ca2+ nearly completely blocked Na-free hyperpolarization. It can be concluded that Na-free hyperpolarizations are related to the functioning of an electrogenic Na(+)-Ca2+ exchange mechanism.

Isolation of p10 gene from Bombyx mori nuclear polyhedrosis virus and study of its promoter activity in recombinant baculovirus vector system

A homologue of Autographa californica NPV (AcNPV) p10 gene was identified and cloned from Bombyx mori NPV (BmNPV). BmNPV p10 gene encodes truncated protein of 70 amino acid residues that lacks carboxyl terminus comparing with the p10 protein encoded by AcNPV. The putative TATA box sequence and the ATAAG motif which is the consensus sequence of baculovirus very late promoter were conserved. A transfer vector, pBNT1, which includes the p10 promoter region of BmNPV for foreign gene expression was constructed. By using pBNT1, a recombinant BmNPV, Bmp10-Luc, in which the p10 gene was replaced by the firefly luciferase gene, was obtained. We also obtained another recombinant virus, BmPH-Luc, in which the polyhedrin gene was replaced by the luciferase gene. The luciferase activity detected in BoMo-15AIIc insect cells infected with Bmp10-Luc was approximately 50% of that infected with BmPH-Luc, suggesting that although both the p10 and polyhedrin promoters of BrnNPV are effective in high-level expression of foreign genes, the p10 promoter is not so strong as the polyhedrin promoter.