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Ecdysone Receptor (ecdysone + receptor)

Distribution by Scientific Domains

Chemistry	63%
Life Sciences	31%

Selected Abstracts

Synergistic interaction of endocrine-disrupting chemicals: Model development using an ecdysone receptor antagonist and a hormone synthesis inhibitor

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2004
Xueyan Mu
Abstract Endocrine toxicants can interfere with hormone signaling through various mechanisms. Some of these mechanisms are interrelated in a manner that might result in synergistic interactions. Here we tested the hypothesis that combined exposure to chemicals that inhibit hormone synthesis and that function as hormone receptor antagonists would result in greater-than-additive toxicity. This hypothesis was tested by assessing the effects of the ecdysteroid-synthesis inhibitor fenarimol and the ecdysteroid receptor antagonist testosterone on ecdysteroid-regulated development in the crustacean Daphnia magna. Both compounds were individually characterized for effects on the development of isolated embryos. Fenarimol caused late developmental abnormalities, consistent with its effect on offspring-derived ecdysone in the maturing embryo. Testosterone interfered with both early and late development of embryos, consistent with its ability to inhibit ecdysone provided by maternal transfer (responsible for early developmental events) or de novo ecdysone synthesis (responsible for late developmental events). We predicted that, by decreasing endogenous levels of hormone, fenarimol would enhance the likelihood of testosterone binding to and inhibiting the ecdysone receptor. Indeed, fenarimol enhanced the toxicity of testosterone, while testosterone had no effect on the toxicity of fenarimol. Algorithms were developed to predict the toxicity of combinations of these two compounds based on independent joint action (IJA) alone as well as IJA with fenarimol-on-testosterone synergy (IJA+SYN). The IJA+SYN model was highly predictive of the experimentally determined combined effects of the two compounds. These results demonstrate that some endocrine toxicants can synergize, and this synergy can be accurately predicted. [source]

Differential effects of US2, US6 and US11 human cytomegalovirus proteins on HLA class,Ia and HLA-E expression: impact on target susceptibility to NK cell subsets

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 10 2003
Manuel Llano
Abstract We compared in an inducible expression system the individual effect of US2, US6 and US11 human cytomegalovirus (HCMV) proteins on HLA-E and HLA class,Ia surface expression, assessing in parallel their influence on target susceptibility to NK cell clones. To this end, the RPMI,8866 B,lymphoma cell line (HLA-A2, HLA-A3, HLA-B7, HLA-Cw7, HLA-ER, HLA-EG) was stably cotransfected with the ecdysone receptor, together with the US sequences under the control of an ecdysone-inducible promoter. Biosynthesis of viral proteins was turned on by incubating transfectants with Ponasterone,A. US6 down-regulated expression of all class,I molecules, hampering target resistance to NK cell clones controlled by the CD94/NKG2A, KIR2DL2 and/or CD85j (ILT2 or LIR-1) inhibitory receptors. By contrast, US11 reduced the surface levels of class,Ia molecules but preserved HLA-E; this rendered US11+ cells sensitive to NK clones under the control of KIR2DL2 and/or CD85j, while their resistance to CD94/NKG2A+KIR2DL2, effector cells was maintained. US2 preserved as well HLA-E expression but selectively targeted class,Ia molecules; in fact, HLA-A and HLA-C allotypes were down-modulated whereas HLA-B7 remained unaltered. US2+ targets became sensitive to KIR2DL2+ cells but remained resistant to CD94/NKG2A+CD85j+ NK clones. The differential effects of US proteins on HLA class,Ia and HLA-E likely reflect the evolutionary adaptation of HCMV to counteract NK-mediated surveillance. [source]

Properties of ecdysteroid receptors from diverse insect species in a heterologous cell culture system , a basis for screening novel insecticidal candidates

FEBS JOURNAL, Issue 11 2009
Joshua M. Beatty
Insect development is driven by the action of ecdysteroids on morphogenetic processes. The classic ecdysteroid receptor is a protein heterodimer composed of two nuclear receptors, the ecdysone receptor (EcR) and Ultraspiracle (USP), the insect ortholog of retinoid X receptor. The functional properties of EcR and USP vary among insect species, and provide a basis for identifying novel and species-specific insecticidal candidates that disrupt this receptor's normal activity. A heterologous mammalian cell culture assay was used to assess the transcriptional activity of the heterodimeric ecdysteroid receptor from species representing two major insect orders: the fruit fly, Drosophila melanogaster (Diptera), and the Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera). Several nonsteroidal agonists evoked a strong response with the L. decemlineata heterodimer that was consistent with biochemical and in vivo evidence, whereas the D. melanogaster receptor's response was comparatively modest. Conversely, the phytoecdysteroid muristerone A was more potent with the D. melanogaster heterodimer. The additional presence of juvenile hormone III potentiated the inductive activity of muristerone A in the receptors from both species, but juvenile hormone III was unable to potentiate the inductive activity of the diacylhydrazine methoxyfenozide (RH2485) in the receptor of either species. The effects of USP on ecdysteroid-regulated transcriptional activity also varied between the two species. When it was tested with D. melanogaster EcR isoforms, basal activity was lower and ligand-dependent activity was higher with L. decemlineata USP than with D. melanogaster USP. Generally, the species-based differences validate the use of the cell culture assay screen for novel agonists and potentiators as species-targeted insecticidal candidates. [source]

Molecular cloning of the ecdysone receptor and the retinoid X receptor from the scorpion Liocheles australasiae

FEBS JOURNAL, Issue 23 2007
Yoshiaki Nakagawa
cDNAs of the ecdysone receptor and the retinoid X receptor were cloned from the Japanese scorpion Liocheles australasiae, and the amino acid sequences were deduced. The full-length cDNA sequences of the L. australasiae ecdysone receptor and the L. australasiae retinoid X receptor were 2881 and 1977 bp in length, respectively, and the open reading frames encoded proteins of 560 and 414 amino acids. The amino acid sequence of the L. australasiae ecdysone receptor was similar to that of the ecdysone receptor-A of the soft tick, Ornithodoros moubata (68%) and to that of the ecdysone receptor-A1 of the lone star tick, Amblyomma americanum (66%), but showed lower similarity to the ecdysone receptors of Orthoptera and Coleoptera (53,57%). The primary sequence of the ligand-binding region of the L. australasiae ecdysone receptor was highly homologous to that of ticks (85,86%). The amino acid sequence of the L. australasiae retinoid X receptor was also homologous to the amino acid sequence of ultraspiracles of ticks (63%) and insects belonging to the orders Orthoptera and Coleoptera (60,64%). The identity of both the L. australasiae ecdysone receptor and the L. australasiae retinoid X receptor to their lepidopteran and dipteran orthologs was less than 50%. The cDNAs of both the L. australasiae ecdysone receptor (L. australasiae ecdysone receptor-A) and the L. australasiae retinoid X receptor were successfully translated in vitro using a rabbit reticulocyte lysate system. An ecdysone analog, ponasterone A, bound to L. australasiae ecdysone receptor-A (KD = 4.2 nm), but not to L. australasiae retinoid X receptor. The L. australasiae retinoid X receptor did not enhance the binding of ponasterone A to L. australasiae ecdysone receptor-A, although L. australasiae retinoid X receptor was necessary for the binding of L. australasiae ecdysone receptor-A to ecdysone response elements. [source]

Presence of membrane ecdysone receptor in the anterior silk gland of the silkworm Bombyx mori

FEBS JOURNAL, Issue 15 2004
Mohamed Elmogy
Nongenomic action of an insect steroid hormone, 20-hydroxyecdysone (20E), has been implicated in several 20E-dependent events including the programmed cell death of Bombyx anterior silk glands (ASGs), but no information is available for the mode of the action. We provide evidence for a putative membrane receptor located in the plasma membrane of the ASGs. Membrane fractions prepared from the ASGs exhibit high binding activity to [3H]ponasterone A (PonA). The membrane fractions did not contain conventional ecdysone receptor as revealed by Western blot analysis using antibody raised against Bombyx ecdysone receptor A (EcR-A). The binding activity was not solubilized with 1,m NaCl or 0.05% (w/v) MEGA-8, indicating that the binding sites were localized in the membrane. Differential solubilization and temperature-induced phase separation in Triton X-114 showed that the binding sites might be integrated membrane proteins. These results indicated that the binding sites are located in plasma membrane proteins, which we putatively referred to as membrane ecdysone receptor (mEcR). The mEcR exhibited saturable binding for [3H]PonA (Kd = 17.3 nm, Bmax = 0.82 pmol·mg,1 protein). Association and dissociation kinetics revealed that [3H]PonA associated with and dissociated from mEcR within minutes. The combined results support the existence of a plasmalemmal ecdysteroid receptor, which may act in concert with the conventional EcR in various 20E-dependent developmental events. [source]

Characterization of core promoter elements for ecdysone receptor isoforms of the silkworm, Bombyx mori

INSECT MOLECULAR BIOLOGY, Issue 2 2007
H. Shirai
Abstract Two ecdysone receptor (EcR) isoforms, EcR-A and EcR-B1, are expressed in a tissue- and stage-specific manner, although the details of their transcription mechanisms are unknown. We determined the transcription start sites of EcR-A and EcR-B1 isoforms of Bombyx mori and found that both core promoter regions consist of initiator (Inr) and downstream promoter elements (DPE) but not TATA boxes. Promoter truncation analysis performed using the luciferase reporter assays and BmN cells showed that, in both isoforms, the regions ,296 to ,74 for BmEcR-B1, ,104 to ,61 for BmEcR-A and downstream regions of +1 are essential for basal transcriptional activity. Mutation experiments revealed that both DPE and its 5,-flanking CGCGCG sequence are crucial but DPE of BmEcR-B1 is not important for BmEcR-A transcription. These results indicate that the basal promoter activities differ between the two BmEcR isoforms. [source]

The rapid divergence of the ecdysone receptor is a synapomorphy for Mecopterida that clarifies the Strepsiptera problem

INSECT MOLECULAR BIOLOGY, Issue 3 2006
F. Bonneton
Abstract In arthropods, the regulation by ecdysteroids is mediated by the heterodimer between the ecdysone receptor (ECR; NR1H1) and ultraspiracle (USP/RXR; NR2B4) nuclear receptors. Both ECR and USP/RXR ligand-binding domains experienced a strong acceleration of evolutionary rate in Diptera and Lepidoptera, which belong to the superorder Mecopterida. We performed a phylogenetic analysis of 28 ECR and 30 USP/RXR protein sequences from 36 arthropod species, including representatives from Trichoptera, Mecoptera and Siphonaptera. Our data show that the acceleration of ECR and USP/RXR was a unique event in the ancestor of Mecopterida. Our analysis shows further that Strepsiptera ECR and USP/RXR sequences are unambiguously placed outside of the Mecopterida clade. Protein alignments reveal that eight of 11 synapomorphies support an affinity between Strepsiptera and Coleoptera sequences. The affiliation of Strepsiptera to Diptera should therefore be rejected. [source]

Apis mellifera ultraspiracle: cDNA sequence and rapid up-regulation by juvenile hormone

INSECT MOLECULAR BIOLOGY, Issue 5 2004
A. R. Barchuk
Abstract Two hormones, 20-hydroxyecdysone (20E) and juvenile hormone (JH) are key regulators of insect development including the differentiation of the alternative caste phenotypes of social insects. In addition, JH plays a different role in adult honey bees, acting as a ,behavioural pacemaker'. The functional receptor for 20E is a heterodimer consisting of the ecdysone receptor and ultraspiracle (USP) whereas the identity of the JH receptor remains unknown. We have cloned and sequenced a cDNA encoding Apis mellifera ultraspiracle (AMUSP) and examined its responses to JH. A rapid, but transient up-regulation of the AMUSP messenger is observed in the fat bodies of both queens and workers. AMusp appears to be a single copy gene that produces two transcripts (,4 and ,5 kb) that are differentially expressed in the animal's body. The predicted AMUSP protein shows greater sequence similarity to its orthologues from the vertebrate,crab,tick,locust group than to the dipteran,lepidopteran group. These characteristics and the rapid up-regulation by JH suggest that some of the USP functions in the honey bee may depend on ligand binding. [source]

Mode of action of methoprene in affecting female reproduction in the African malaria mosquito, Anopheles gambiae

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 9 2010
Hua Bai
Abstract BACKGROUND: One of the most studied actions of juvenile hormone (JH) is its ability to modulate ecdysteroid signaling during insect development and metamorphosis. Previous studies in mosquitoes showed that 20-hydroxyecdysone (20E) regulates vitellogenin synthesis. However, the action of JH and its mimics, e.g. methoprene, on female reproduction of mosquitoes remains unknown. RESULTS: Here, a major malaria vector, Anopheles gambiae Giles, was used as a model insect to study the action of methoprene on female reproduction. Ecdysteroid titers and expression profiles of ecdysone-regulated genes were determined before and after a blood meal. An ecdysteroid peak was detected at 12 h post blood meal (PBM). The maximum expression of ecdysone-regulated genes, such as ecdysone receptor (EcR), hormone receptor 3 (HR3) and vitellogenin (Vg) gene, coincided with the ecdysteroid peak. Interestingly, topical application of methoprene at 6 h PBM delayed ovarian development and egg maturation by suppressing the expression of ecdysone-regulated genes in female mosquitoes. CONCLUSION: The data suggest that ecdysteroid titers are correlated with Vg synthesis, and methoprene affects vitellogenesis by modulating ecdysteroid action in A. gambiae. Copyright © 2010 Society of Chemical Industry [source]

Influence of cell cycle on ecdysteroid receptor in CHO-K1 cells

ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 3 2009
Katarzyna Betanska
Abstract CHO-K1 cells are routinely used for characterization of ecdysone receptor (EcR) function, because these vertebrate cells are devoid of endogenous ecdysone receptor protein. Moreover, the endogenous expression of RXR, the vertebrate orthologue of Ultraspiracle (Usp), the most important heterodimerization partner, is neglectable. In contrast to insect cells, there is also no influence of moulting hormone on CHO-K1 cells on cell proliferation either in the absence or presence of transiently expressed EcR. In contrast to Usp, which is exclusively found in nuclei, EcR is heterogeneously distributed between cytoplasm and nuclei in non-synchronized cells. Synchronization of CHO-K1 cells by nocodazole revealed that the cell cycle influences receptor concentration with lowest amounts in late S-phase and G2/M phase and intracellular distribution of the receptor protein showing a minimum of receptors present in nuclei during S-phase. EcR, but not Usp reduces cyclin D1 expression and cyclin D1 concentration is impaired by cyclin D1. Coimmunoprecipitation studies reveal physical interaction of EcR and cyclin D1. © 2009 Wiley Periodicals, Inc. [source]

Transcriptional activity of ecdysone receptor isoforms is regulated by modulation of receptor stability and interaction with Ab- and C-domains of the heterodimerization partner ultraspiracle

ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 3 2009
Heike Ruff
Abstract The stability of ecdysone receptor (EcR) expressed in a heterologous system is regulated in an isoform-specific manner and modified by ligand and heterodimerization partner. Transcriptional activities of various receptor complexes with Usp and ligand as determined by reporter assays are the result of two effects: change in receptor concentration and altered transcriptional capability. Transcriptional activity of EcR-A is low when compared to EcR-B1 independent of the absence or presence of Ultraspiracle (Usp). Ligand increased the concentration of EcR-A, but had no effect on the transcriptional capability, in contrast to EcR-B1, which is not stabilized by hormone or Usp, but the transcriptional capability is enhanced by heterodimerization and ligand. Exchange of the AB-domain of Usp by the activation domain (AD) of Vp16 revealed that the N-terminus of Usp inhibited transcriptional activity only with EcR-B isoforms, whereas the hexapeptide in the AB-domain of wild type Usp adjacent to the C-domain of Usp harbours an activating function. Deletion of the C-domain of Usp did not affect the stability of the receptor complex, but reduced the transcriptional capability of heterodimers with all EcR-isoforms, indicating that the stability of the receptor, which is important for termination of the hormone signal transduction, is regulated in a cooperative manner by the AB-domains of EcR and Usp, and ligand. We show the active role of Usp in modulation of the transcriptional activity of the heterodimer in an isoform-specific manner by the inhibitory N-terminus, the activating hexapeptide in the AB-domain, and the C-domain of Usp. © 2009 Wiley Periodicals, Inc. [source]

DNA-binding properties of Drosophila ecdysone receptor isoforms and their modification by the heterodimerization partner ultraspiracle

ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 3 2009
Simone Braun
Abstract Transcriptional activity of ecdysone receptor (EcR) isoforms varies considerably and is modified further by the heterodimerization partner and hormone treatment. To investigate whether differences in DNA binding of receptor complexes are responsible for these variations in transcriptional activity, interaction of Drosophila EcR isoforms, and variants of Ultraspiracle (Usp), the orthologue of RXR, with the ecdysone response elements (EcRE) hsp 27, PAL-1, and DR-1, were determined by electrophoretic mobility shift assays. Receptor proteins were expressed in vertebrate cells (CHO-K1) in order to rule out an influence of endogenous receptor proteins. In the absence of a heterodimerization partner, weak DNA binding of EcR was detected even without hormone with EcR-A and -B1, but not EcR-B2. In the presence of hormone, all three isoforms show increased binding to the hsp 27 EcRE. The heterodimerization partner Usp increased DNA binding considerably. The hormone effect of heterodimers is more pronounced with both EcR-B isoforms compared to EcR-A. Two specific bands were obtained for EcR-A and B1 but only one band is visible with EcR-B2. Deletion of the C-domain of Usp still allows basal DNA binding of the heterodimer, but in contrast to full-length Usp, addition of hormone decreases the intensity of the retarded receptor band of all EcR isoforms and the EcREs hsp27 and DR-1 considerably, whereas interaction with the EcRE PAL-1 is only slightly affected. Synergistic effects on transcriptional activity are associated with the formation of different receptor DNA-complexes observed with 1×hsp27 and 3×hsp27. Comparison of DNA-binding properties of EcR isoforms and EcR/Usp heterodimers revealed that binding of receptor complexes to hsp 27 EcRE is dependent on the AB domain of EcR and the AB-, C-, and D-domains of the heterodimerization partner. Interaction with the hsp 27 EcRE correlates neither with ligand binding nor with transcriptional activity of the various receptor complexes. We, therefore, conclude that the different receptor functions are regulated separately, for example, by interaction with co-modulators or post-transcriptional modifications. © 2009 Wiley Periodicals, Inc. [source]

Interaction of proteins involved in ecdysone and juvenile hormone signal transduction,

ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2009
Kavita Bitra
Abstract Ecdysteroids and juvenile hormones (JH) regulate a variety of developmental, physiological, behavioral, and metabolic processes. Ecdysteroids function through a heterodimeric complex of two nuclear receptors, ecdysone receptor (EcR) and ultraspiracle (USP). An 85 kDa protein identified in Drosophila melanogaster methoprene-tolerant (Met) mutant binds to JH III with high affinity, and the mutant flies are resistant to juvenile hormone analog (JHA), methoprene. Reporter assays using the yeast two-hybrid system were performed in order to study the molecular interactions between EcR, USP and Met. As expected, EcR fused to the B42 activation domain and USP fused to the LexA DNA binding domain interacted with each other and supported induction of the reporter gene in the presence of stable ecdysteroid analog, RG-102240 or steroids, muristerone A and ponasterone A. The USP:USP homodimers supported expression of the reporter gene in the absence of ligand, and there was no significant increase in the reporter activity after addition of a JHA, methoprene. Similarly, Met:Met homodimers as well as Met:EcR and Met:USP heterodimers induced reporter activity in the absence of ligand and addition of ecdysteroid or JH analogs did not increase the reporter activity regulated by either homodimers or heterodimers of Met protein. Two-hybrid assays in insect cells and in vitro pull-down assays confirmed the interaction of Met with EcR and USP. These data suggest that the proteins that are involved in signal transduction of ecdysteroids (EcR and USP) and juvenile hormones (Met) interact to mediate cross-talk between these two important hormones. Arch. Insect Biochem. Physiol. 2008. © 2008 Wiley-Liss, Inc. [source]

Proliferation and differentiation of intestinal stem cells during metamorphosis of the red flour beetle, Tribolium castaneum

DEVELOPMENTAL DYNAMICS, Issue 4 2008
R. Parthasarathy
Abstract The insect midgut epithelium is remodeled during larval-pupal metamorphosis when larval polyploid cells (LPCs) are replaced by the daughters of intestinal stem cells (ISCs). We characterized the proliferation of ISCs during midgut remodeling in the red flour beetle, Tribolium castaneum. Midgut remodeling is initiated at 96 hr after ecdysis into the final instar larval stage. Immunocytochemistry with bromodeoxyuridine and phospho-histone H3 antibodies showed that the ISCs are the progenitors of the pupal/adult midgut epithelium and they undergo proliferation and differentiation to form new midgut epithelium. In vitro midgut culture experiments revealed that 20-hydroxyecdysone (20E) in the absence of juvenile hormone induces proliferation of ISCs. RNA interference (RNAi) mediated silencing of ecdysone receptors (EcRA and EcRB) and ultraspiracle (USP) identified EcRA and USP but not EcRB as the proteins involved in 20E regulation of ISCs proliferation. These data show that the proliferation of ISCs is under both developmental and endocrine regulation. Developmental Dynamics 237:893,908, 2008. © 2008 Wiley-Liss, Inc. [source]