The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Michael E Adams - One of the best experts on this subject based on the ideXlab platform.
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RESEARCH ARTICLE Rescheduling Behavioral Subunits of a Fixed Action Pattern by Genetic Manipulation of Peptidergic Signaling
2016Co-Authors: Miran Han, Youngjoon Kim, Gyunghee Lee, Sang Soo Lee, Michael E AdamsAbstract:The Ecdysis behavioral sequence in insects is a classic fixed action pattern (FAP) initiated by hormonal signaling. Ecdysis triggering hormones (ETHs) release the FAP through direct actions on the CNS. Here we present evidence implicating two groups of central ETH recep-tor (ETHR) neurons in scheduling the first two steps of the FAP: kinin (aka drosokinin, leuco-kinin) neurons regulate pre-Ecdysis behavior and CAMB neurons (CCAP, AstCC,MIP, and Bursicon) initiate the switch to Ecdysis behavior. Ablation of kinin neurons or altering levels of ETH receptor (ETHR) expression in these neurons modifies timing and intensity of pre-Ecdysis behavior. Cell ablation or ETHR knockdown in CAMB neurons delays the switch to Ecdysis, whereas overexpression of ETHR or expression of pertussis toxin in these neurons accelerates timing of the switch. Calcium dynamics in kinin neurons are temporally aligned with pre-Ecdysis behavior, whereas activity of CAMB neurons coincides with the switch from pre-Ecdysis to Ecdysis behavior. Activation of CCAP or CAMB neurons through tem-perature-sensitive TRPM8 gating is sufficient to trigger Ecdysis behavior. Our findings dem-onstrate that kinin and CAMB neurons are direct targets of ETH and play critical roles in scheduling successive behavioral steps in the Ecdysis FAP. Moreover, temporal organiza-tion of the FAP is likely a function of ETH receptor density in target neurons
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rescheduling behavioral subunits of a fixed action pattern by genetic manipulation of peptidergic signaling
PLOS Genetics, 2015Co-Authors: Dohyoung Kim, Youngjoon Kim, Miran Han, Gyunghee Lee, Sang Soo Lee, Michael E AdamsAbstract:The Ecdysis behavioral sequence in insects is a classic fixed action pattern (FAP) initiated by hormonal signaling. Ecdysis triggering hormones (ETHs) release the FAP through direct actions on the CNS. Here we present evidence implicating two groups of central ETH receptor (ETHR) neurons in scheduling the first two steps of the FAP: kinin (aka drosokinin, leucokinin) neurons regulate pre-Ecdysis behavior and CAMB neurons (CCAP, AstCC, MIP, and Bursicon) initiate the switch to Ecdysis behavior. Ablation of kinin neurons or altering levels of ETH receptor (ETHR) expression in these neurons modifies timing and intensity of pre-Ecdysis behavior. Cell ablation or ETHR knockdown in CAMB neurons delays the switch to Ecdysis, whereas overexpression of ETHR or expression of pertussis toxin in these neurons accelerates timing of the switch. Calcium dynamics in kinin neurons are temporally aligned with pre-Ecdysis behavior, whereas activity of CAMB neurons coincides with the switch from pre-Ecdysis to Ecdysis behavior. Activation of CCAP or CAMB neurons through temperature-sensitive TRPM8 gating is sufficient to trigger Ecdysis behavior. Our findings demonstrate that kinin and CAMB neurons are direct targets of ETH and play critical roles in scheduling successive behavioral steps in the Ecdysis FAP. Moreover, temporal organization of the FAP is likely a function of ETH receptor density in target neurons.
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A model depicting functional roles of kinin and CAMB neurons in scheduling of the Ecdysis FAP.
2015Co-Authors: Dohyoung Kim, Youngjoon Kim, Miran Han, Gyunghee Lee, Sang Soo Lee, Michael E AdamsAbstract:ETH release from Inka cells activates ETHR neurons (ETHR-A and ETHR-B). ETHR-B neurons are more sensitive to ETH and become active immediately following ETH release. These neurons release signal(s) that engage Gαo signaling in CAMB neurons. ETH activates kinin neurons directly governing pre-Ecdysis and CAMB neurons via ETHR-A and Gαq signaling. Initially, pre-Ecdysis is induced, whereas CAMB neurons remain silent due to relatively low sensitivity to ETH and Gαo-mediated inhibitory input. Upon reaching adequate ETH levels in the hemolymph, ETH-mediated Gαq signaling overrides Gαo signaling in CAMB neurons, leading to co-release of CCAP, AstCC, MIP, and bursicon. This results in pre-Ecdysis inhibition and the switch to Ecdysis behavior and post-Ecdysis behavior. Additional excitatory inputs from non-CAMB CCAP neurons contribute to vigorous Ecdysis swings, resulting in head eversion. The dashed arrow represents hypothetical input to CAMB neurons from as yet unidentified ETHR-B neurons.
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Ecdysis triggering hormone signaling in arthropods
Peptides, 2010Co-Authors: Ladislav Roller, Yoonseong Park, Li Dai, Ladislav Simo, Honoo Satake, Yoshiaki Tanaka, Michael E AdamsAbstract:Ecdysis triggering hormones (ETHs) from endocrine Inka cells initiate the Ecdysis sequence through action on central neurons expressing ETH receptors (ETHR) in model moth and dipteran species. We used various biochemical, molecular and BLAST search techniques to detect these signaling molecules in representatives of diverse arthropods. Using peptide isolation from tracheal extracts, cDNA cloning or homology searches, we identified ETHs in a variety of hemimetabolous and holometabolous insects. Most insects produce two related ETHs, but only a single active peptide was isolated from the cricket and one peptide is encoded by the eth gene of the honeybee, parasitic wasp and aphid. Immunohistochemical staining with antiserum to Manduca PETH revealed Inka cells on tracheal surface of diverse insects. In spite of conserved ETH sequences, comparison of natural and the ETH-induced Ecdysis sequence in the honeybee and beetle revealed considerable species-specific differences in pre-Ecdysis and Ecdysis behaviors. DNA sequences coding for putative ETHR were deduced from available genomes of several hemimetabolous and holometabolous insects. In all insects examined, the ethr gene encodes two subtypes of the receptor (ETHR-A and ETHR-B). Phylogenetic analysis showed that these receptors fall into a family of closely related GPCRs. We report for the first time the presence of putative ETHs and ETHRs in genomes of other arthropods, including the tick (Arachnida) and water flea (Crustacea). The possible source of ETH in ticks was detected in paired cells located in all pedal segments. Our results provide further evidence of structural and functional conservation of ETH-ETHR signaling.
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Ecdysis triggering hormone signaling in the yellow fever mosquito aedes aegypti
General and Comparative Endocrinology, 2009Co-Authors: Li Dai, Michael E AdamsAbstract:At the end of each developmental stage, the yellow fever mosquito Aedes aegypti performs the Ecdysis behavioral sequence, a precisely timed series of behaviors that culminates in shedding of the old exoskeleton. Here we describe Ecdysis triggering hormone-immunoreactive Inka cells located at branch points of major tracheal trunks and loss of staining coincident with Ecdysis. Peptides (AeaETH1, AeaETH2) purified from extracts of pharate 4th instar larvae have—PRXamide C-terminal amino acid sequence motifs similar to ETHs previously identified in moths and flies. Injection of synthetic AeaETHs induced premature Ecdysis behavior in pharate larvae, pupae and adults. Two functionally distinct subtypes of ETH receptors (AeaETHR-A, AeaETHR-B) of A. aegypti are identified and show high sensitivity and selectivity to ETHs. Increased ETHR transcript levels and behavioral sensitivity to AeaETHs arising in the hours preceding the 4th instar larva-to-pupa Ecdysis are correlated with rising ecdysteroid levels, suggesting steroid regulation of receptor gene expression. Our description of natural and ETH-induced Ecdysis in A. aegypti should facilitate future approaches directed toward hormone-based interference strategies for control of mosquitoes as human disease vectors.
James W. Truman - One of the best experts on this subject based on the ideXlab platform.
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hormonal control of insect Ecdysis endocrine cascades for coordinating behavior with physiology
Vitamins and Hormones Series, 2005Co-Authors: James W. TrumanAbstract:Publisher Summary This chapter presents an overview of the Ecdysis control system, emphasizing the lessons from Ecdysis control that may help in understanding behavioral organization in animals in general. The first indication of a hormonal control over the Ecdysis sequence came from studies on the giant silk moths, Hyalophora cecropia and Antheraea pernyi . Brain extirpation and implantation experiments within and between species showed that the brain controlled the timing of the behavior and could exert this control even if transplanted to the abdomen. Among insects, the wealth of variation in the factors that control Ecdysis is evident at both the species and the stage level. Manduca and Drosophila have received the most attention in this regard, and there is only scattered information available for other species. In Manduca , ETH and PETH appear in the blood coincident with the onset of pre‐Ecdysis movements. Experiments with isolated CNS preparations in Manduca show the onset of pre‐Ecdysis motor bursts a few minutes after addition of the peptides and the pre‐Ecdysis behaviors fail to appear in mutant Drosophila that lack a functional ETH gene. Temporal ordering is also evident in the interaction of the cells that produce and release the various modulators. A crucial feature of the behavioral program is that it occurs at the appropriate time relative to the developmental processes of the molt.
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modulation of Ecdysis in the moth manduca sexta the roles of the suboesophageal and thoracic ganglia
The Journal of Experimental Biology, 2002Co-Authors: Megumi Fuse, James W. TrumanAbstract:The sequential behaviours shown by insects at Ecdysis are due to the sequential release of various hormones, but the transition from one phase to the next can be fine-tuned by inhibitory influences. The Ecdysis sequence in the moth Manduca sexta was initiated by injecting sensitive animals with the neuropeptide Ecdysis-triggering hormone (ETH). Exposure to ETH stimulates the release of eclosion hormone (EH) which, in turn, activates a set of neurons containing crustacean cardioactive peptide (CCAP) by elevating their levels of intracellular cyclic GMP. We characterized a set of non-CCAP containing neurons that also appear to be EH targets because of their response to cyclic GMP at Ecdysis. The neurons did not display leucokinin-, diuretic-hormone- or FMRFamide-like immunoreactivity. They are probably the bursicon-containing cells described previously. After release of EH, there is a transient inhibition of the abdominal centers responsible for Ecdysis. Transection experiments suggested that this suppression is via descending inhibitory units from the suboesophageal and thoracic ganglia. The duration of this inhibition appears to depend on the levels of cyclic GMP and can be extended by pharmacologically suppressing cyclic GMP breakdown. We further found that brief exposure to CO2 caused premature Ecdysis. Since the CO2 treatment was effective only after EH release, it probably acts by suppressing descending inhibition. Studies on adult eclosion suggest that CO2, given at the appropriate time, can uncouple the basic larval motor program from modulatory influences provided by the adult pterothoracic ganglion. CO2 therefore appears to be a novel and non-invasive tool for studies of Ecdysis behavior in insects.
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the hormonal coordination of behavior and physiology at adult Ecdysis in drosophila melanogaster
The Journal of Experimental Biology, 1999Co-Authors: James D Baker, Susan L Mcnabb, James W. TrumanAbstract:In insects, Ecdysis is thought to be controlled by the interaction between peptide hormones; in particular between Ecdysis-triggering hormone (ETH) from the periphery and eclosion hormone (EH) and crustacean cardioactive peptide (CCAP) from the central nervous system. We examined the behavioral and physiological functions of the first two of these peptides in Drosophila melanogaster using wild-type flies and knockout flies that lacked EH neurons. We used ETH from Manduca sexta (MasETH) to induce premature Ecdysis and compared the responses of the two types of flies. The final release of EH normally occurs approximately 40 min before Ecdysis. It is correlated with cyclic guanosine monophosphate (cGMP) production in selected neurons and tracheae, by an elevation in the heart rate and by the filling of the new tracheae with air. Injection of developing flies with MasETH causes all these events to occur prematurely. In EH cell knockouts, none of these changes occurs in response to MasETH, and these flies show a permanent failure in tracheal filling. This failure can be overcome in the knockouts by injecting them with membrane-permeant analogs of cGMP, the second messenger for EH. The basis for the 40 min delay between EH release and the onset of Ecdysis was examined by decapitating flies at various times relative to EH release. In flies that had already released EH, decapitation was always followed within 1 min by the start of Ecdysis. Immediate Ecdysis was never observed when the EH cell knockout flies were decapitated. We propose that EH activates both ventral central nervous system elements necessary for Ecdysis (possibly the CCAP cells) and descending inhibitory neurons from the head. This descending inhibition establishes a delay in the onset of Ecdysis that allows the completion of EH-activated physiological processes such as tracheal filling. A waning in the inhibition eventually allows Ecdysis to begin 30–40 min later.
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Programmed cell death of identified peptidergic neurons involved in Ecdysis behavior in the Moth, Manduca sexta.
Journal of neurobiology, 1998Co-Authors: John Ewer, James W. Truman, Kathleen A. Klukas, Karen A. Mesce, Chiou Miin Wang, Susan E. FahrbachAbstract:The eclosion of the adult Manduca sexta moth is followed by a wave of cell death that eliminates up to 50% of the neurons of the central nervous system within the first few days of imaginal life. While the identity of some of the dying motoneurons has been established, that of most doomed neurons is unknown. Here, we show that the dying cells include peptidergic neurons involved in the control of Ecdysis behavior. These cells belong to a small population of 50 neurons that express crustacean cardioactive peptide (CCAP), a potent regulator of the Ecdysis motor program, and show increases in cyclic 3',5'-guanosine monophosphate at each Ecdysis. First, we describe new markers for these neurons and show that they are expressed in these CCAP-immunoreactive neurons in a complex temporal pattern during development. We then show that these neurons die within 36 h after adult eclosion, the last performance of Ecdysis behavior in the life of the animal, via the active, genetically determined process of programmed cell death. The death of these neurons supports the hypothesis that outmoded or unused neurons are actively eliminated.
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invariant association of Ecdysis with increases in cyclic 3 5 guanosine monophosphate immunoreactivity in a small network of peptidergic neurons in the hornworm manduca sexta
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 1997Co-Authors: John Ewer, James W. TrumanAbstract:At the end of each molt insects shed their old cuticle by performing the stereotyped behavior of Ecdysis. In the moth, Manduca sexta, this behavior is triggered by the neuropeptide eclosion hormone (EH). Insights into the mechanism of action of EH have come from the identification of a small network of peptidergic neurons that shows increased cyclic 3',5'-guanosine monophosphate (cGMP) immunoreactivity at Ecdysis in insects from many different orders. Here we present further evidence that strengthens the association between Ecdysis and the occurrence of this cGMP response in Manduca. We found that the cGMP increases occurred at every Ecdysis, although some of the neurons that showed a response at larval Ecdysis did not participate at pupal and adult Ecdysis. Both Ecdysis and the cGMP increases only required an intact connection with the brain for the first 30 min after EH injection. Interestingly, Ecdysis in debrained animals only occurred if the cGMP response had been initiated, suggesting that the onset of this response marks the time at which the central nervous system is first able to drive Ecdysis. Finally, we found that the appearance of sensitivity to EH for triggering the cGMP response coincided with the time at which EH first triggers Ecdysis.
Dusan Zitnan - One of the best experts on this subject based on the ideXlab platform.
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complex steroid peptide receptor cascade controls insect Ecdysis
General and Comparative Endocrinology, 2007Co-Authors: Dusan Zitnan, Inka Zitnanova, Youngjoon Kim, Ladislav Roller, Michael E AdamsAbstract:Insect Ecdysis sequence is composed of pre-Ecdysis, Ecdysis and post-Ecdysis behaviors controlled by a complex cascade of peptide hormones from endocrine Inka cells and neuropeptides in the central nervous system (CNS). Inka cells produce pre-Ecdysis and Ecdysis triggering hormones (ETH) which activate the Ecdysis sequence through receptor-mediated actions on specific neurons in the CNS. Multiple experimental approaches have been used to determine mechanisms of ETH expression and release from Inka cells and its action on the CNS of moths and flies. During the preparatory phase 1-2 days prior to Ecdysis, high ecdysteroid levels induce expression of ETH receptors in the CNS and increased ETH production in Inka cells, which coincides with expression of nuclear ecdysone receptor (EcR) and transcription factor cryptocephal (CRC). However, high ecdysteroid levels prevent ETH release from Inka cells. Acquisition of Inka cell competence to release ETH requires decline of ecdysteroid levels and beta-FTZ-F1 expression few hours prior to Ecdysis. The behavioral phase is initiated by ETH secretion into the hemolymph, which is controlled by two brain neuropeptides-corazonin and eclosion hormone (EH). Corazonin acts on its receptor in Inka cells to elicit low level ETH secretion and initiation of pre-Ecdysis, while EH induces cGMP-mediated ETH depletion and consequent activation of Ecdysis. The activation of both behaviors is accomplished by ETH action on central neurons expressing ETH receptors A and B (ETHR-A and B). These neurons produce numerous excitatory or inhibitory neuropeptides which initiate or terminate different phases of the Ecdysis sequence. Our data indicate that insect Ecdysis is a very complex process characterized by two principal steps: (1) ecdysteroid-induced expression of receptors and transcription factors in the CNS and Inka cells. (2) Release and interaction of Inka cell peptide hormones and multiple central neuropeptides to control consecutive phases of the Ecdysis sequence.
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developmental peptides eth corazonin and ptth
Handbook of Biologically Active Peptides, 2006Co-Authors: Michael E Adams, Yoonseong Park, Dusan ZitnanAbstract:ABSTRACT Ecdysis triggering hormones (ETHs) are small, linear, C-terminally amidated peptides produced and released by endocrine Inka cells under the control of ecdysteroids and other peptides. Released into the blood at the end of each molt, they act directly on the central nervous system to trigger a sequence of physiological and behavioral events culminating in Ecdysis, or shedding of the old cuticle. Corazonin is an N- and C-terminally blocked neuropeptide produced by neurosecretory cells in the brain and ventral nerve cord. It has a number of physiological actions, including cardioacceleration, melanization, and Ecdysis initiation. Prothoracicotropic hormones (PTTHs) is a large (22 kDa) homodimeric peptide hormone produced by two pairs of lateral neurosecretory cells in the brain. It acts on the prothoracic glands to promote synthesis and release of ecdysteroids. Precursors of all these peptide hormones contain associated peptides of unknown function.
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corazonin receptor signaling in Ecdysis initiation
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Ivana Spalovskavalachova, Inka Zitnanova, Michael E Adams, Yoonseong Park, Dusan ZitnanAbstract:Corazonin is a highly conserved neuropeptide hormone of wide-spread occurrence in insects yet is associated with no universally recognized function. After discovery of the corazonin receptor in Drosophila, we identified its ortholog in the moth, Manduca sexta, as a prelude to physiological studies. The corazonin receptor cDNA in M. sexta encodes a protein of 436 amino acids with seven putative transmembrane domains and shares common ancestry with its Drosophila counterpart. The receptor exhibits high sensitivity and selectivity for corazonin when expressed in Xenopus oocytes (EC50 ≈ 200 pM) or Chinese hamster ovary cells (EC50 ≈ 75 pM). Northern blot analysis locates the receptor in peripheral endocrine Inka cells, the source of preEcdysis- and Ecdysis-triggering hormones. Injection of corazonin into pharate larvae elicits release of these peptides from Inka cells, which induce precocious preEcdysis and Ecdysis behaviors. In vitro exposure of isolated Inka cells to corazonin (25-100 pM) induces preEcdysis- and Ecdysis-triggering hormone secretion. Using corazonin receptor as a biosensor, we show that corazonin concentrations in the hemolymph 20 min before natural preEcdysis onset range from 20 to 80 pM and then decline over the next 30-40 min. These findings support the role of corazonin signaling in initiation of the Ecdysis behavioral sequence. We propose a model for peptide-mediated interactions between Inka cells and the CNS underlying this process in insect development.
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conservation of Ecdysis triggering hormone signalling in insects
The Journal of Experimental Biology, 2003Co-Authors: Dusan Zitnan, Inka Zitnanova, Yoonseong Park, Ivana Spalovska, Peter Takac, Michael E AdamsAbstract:Pre-Ecdysis- and Ecdysis-triggering hormones (PETH and ETH) from endocrine Inka cells initiate Ecdysis in moths and Drosophila through direct actions on the central nervous system (CNS). Using immunohistochemistry, we found Inka cells in representatives of all major insect orders. In most insects, Inka cells are numerous, small and scattered throughout the tracheal system. Only some higher holometabolous insects exhibit 8-9 pairs of large Inka cells attached to tracheae in each prothoracic and abdominal segment. The number and morphology of Inka cells can be very variable even in the same individuals or related insects, but all produce peptide hormones that are completely released at each Ecdysis. Injection of tracheal extracts prepared from representatives of several insect orders induces pre-Ecdysis and Ecdysis behaviours in pharate larvae of Bombyx, indicating functional similarity of these peptides. We isolated several PETH-immunoreactive peptides from tracheal extracts of the cockroach Nauphoeta cinerea and the bug Pyrrhocoris apterus and identified the gene encoding two putative ETHs in the mosquito Anopheles gambiae. Inka cells also are stained with antisera to myomodulin, FMRFamide and other peptides sharing RXamide carboxyl termini. However, our enzyme immunoassays show that these antisera cross-react with PETH and ETH. Our results suggest that Inka cells of different insects produce only peptide hormones closely related to PETH and ETH, which are essential endocrine factors required for activation of the Ecdysis behavioural sequence.
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molecular cloning and function of Ecdysis triggering hormones in the silkworm bombyx mori
The Journal of Experimental Biology, 2002Co-Authors: Dusan Zitnan, Inka Zitnanova, Laura Hollar, Ivana Spalovska, Peter Takac, Sarjeet S Gill, Michael E AdamsAbstract:Inka cells of the epitracheal endocrine system produce peptide hormones involved in the regulation of insect Ecdysis. In the silkworm Bombyx mori, injection of Inka cell extract into pharate larvae, pupae or adults activates the Ecdysis behavioural sequence. In the present study, we report the identification of three peptides in these extracts, pre-Ecdysis-triggering hormone (PETH), Ecdysis-triggering hormone (ETH) and ETH-associated peptide (ETH-AP), which are encoded by the same cDNA precursor. Strong immunoreactivity associated with each peptide in Inka cells prior to Ecdysis disappears during each Ecdysis, indicating complete release of these peptides. Injection of either PETH or ETH alone is sufficient to elicit the entire Ecdysis behavioural sequence through the direct action on abdominal ganglia; cephalic and thoracic ganglia are not required for the transition from pre-Ecdysis to Ecdysis behaviour. Our in vitro data provide evidence that these peptides control the entire Ecdysis behavioural sequence through activation of specific circuits in the nervous system. Ecdysis of intact larvae is associated with the central release of eclosion hormone (EH) and elevation of cyclic 3',5'-guanosine monophosphate (cGMP) in the ventral nerve cord. However, injection of ETH into isolated abdomens induces cGMP elevation and Ecdysis behaviour without a detectable release of EH, suggesting that an additional central factor(s) may be involved in the activation of this process. Our findings provide the first detailed account of the natural and hormonally induced behavioural sequence preceding larval, pupal and adult ecdyses of B. mori and highlight significant differences in the neuro-endocrine activation of pre-Ecdysis and Ecdysis behaviours compared with the related moth, Manduca sexta.
John Ewer - One of the best experts on this subject based on the ideXlab platform.
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Cellular/Molecular Genetic Analysis of Ecdysis Behavior in Drosophila Reveals Partially Overlapping Functions of Two Unrelated
2016Co-Authors: Eleanor C. Lahr, Derek Dean, John EwerAbstract:Ecdysis behavior allows insects to shed their old exoskeleton at the end of every molt. It is controlled by a suite of interacting hormones and neuropeptides, and has served as a useful behavior for understanding how bioactive peptides regulate CNS function. Previous findings suggest that crustacean cardioactive peptide (CCAP) activates the Ecdysis motor program; the hormone bursicon is believed to then act downstreamofCCAP to inflate, pigment, andharden the exoskeletonof thenext stage.However, the exact roles of these signaling molecules in regulating Ecdysis remain unclear. Here we use a genetic approach to investigate the functions of CCAP and bursicon in Drosophila Ecdysis.We show that nullmutants inCCAPexpress no apparent defects in Ecdysis andpostEcdysis, producingnormal adults. By contrast, a substantial fraction of flies genetically null for one of the two subunits of bursicon [encoded by the partner of bursicon gene (pburs)] show severe defects in Ecdysis, with escaper adults exhibiting the expected failures in wing expansion and exoskeleton pigmen-tation andhardening. Furthermore, flies lacking bothCCAPandbursicon showmuchmore severe defects at Ecdysis than do animals null for either neuropeptide alone.Our results show that the functions thought tobe subservedbyCCAParepartially effectedbybursicon, and that bursicon plays an important and heretofore undescribed role in Ecdysis behavior itself. These findings have important implications for understanding the regulation of this vital insect behavior and the mechanisms by which hormones and neuropeptides control the physiology and behavior of animals
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the splice isoforms of the drosophila Ecdysis triggering hormone receptor have developmentally distinct roles
Genetics, 2016Co-Authors: Feici Diao, Paul H. Taghert, John Ewer, Wilson Mena, Jonathan Shi, Dongkook Park, Fengqiu Diao, Benjamin H WhiteAbstract:To grow, insects must periodically shed their exoskeletons. This process, called Ecdysis, is initiated by the endocrine release of Ecdysis Trigger Hormone (ETH) and has been extensively studied as a model for understanding the hormonal control of behavior. Understanding how ETH regulates Ecdysis behavior, however, has been impeded by limited knowledge of the hormone's neuronal targets. An alternatively spliced gene encoding a G-protein-coupled receptor (ETHR) that is activated by ETH has been identified, and several lines of evidence support a role in Ecdysis for its A-isoform. The function of a second ETHR isoform (ETHRB) remains unknown. Here we use the recently introduced "Trojan exon" technique to simultaneously mutate the ETHR gene and gain genetic access to the neurons that express its two isoforms. We show that ETHRA and ETHRB are expressed in largely distinct subsets of neurons and that ETHRA- but not ETHRB-expressing neurons are required for Ecdysis at all developmental stages. However, both genetic and neuronal manipulations indicate an essential role for ETHRB at pupal and adult, but not larval, Ecdysis. We also identify several functionally important subsets of ETHR-expressing neurons including one that coexpresses the peptide Leucokinin and regulates fluid balance to facilitate Ecdysis at the pupal stage. The general strategy presented here of using a receptor gene as an entry point for genetic and neuronal manipulations should be useful in establishing patterns of functional connectivity in other hormonally regulated networks.
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genetic analysis of eclosion hormone action during drosophila larval Ecdysis
Development, 2015Co-Authors: Eileen Kruger, Eleanor C. Lahr, Wilson Mena, Erik C Johnson, John EwerAbstract:Insect growth is punctuated by molts, during which the animal produces a new exoskeleton. The molt culminates in Ecdysis, an ordered sequence of behaviors that causes the old cuticle to be shed. This sequence is activated by Ecdysis triggering hormone (ETH), which acts on the CNS to activate neurons that produce neuropeptides implicated in Ecdysis, including Eclosion hormone (EH), Crustacean cardioactive peptide (CCAP) and Bursicon. Despite more than 40 years of research on Ecdysis, our understanding of the precise roles of these neurohormones remains rudimentary. Of particular interest is EH; although it is known to upregulate ETH release, other roles for EH have remained elusive. We isolated an Eh null mutant in Drosophila and used it to investigate the role of EH in larval Ecdysis. We found that null mutant animals invariably died at around the time of Ecdysis, revealing an essential role in its control. Further analyses showed that these animals failed to express the preparatory behavior of pre-Ecdysis while directly expressing the motor program of Ecdysis. Although ETH release could not be detected, the lack of pre-Ecdysis could not be rescued by injections of ETH, suggesting that EH is required within the CNS for ETH to trigger the normal ecdysial sequence. Using a genetically encoded calcium probe, we showed that EH configured the response of the CNS to ETH. These findings show that EH plays an essential role in the Drosophila CNS in the control of Ecdysis, in addition to its known role in the periphery of triggering ETH release.
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Genetic Analysis of Ecdysis Behavior in Drosophila Reveals Partially Overlapping Functions of Two Unrelated Neuropeptides
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2012Co-Authors: Eleanor C. Lahr, Derek M. Dean, John EwerAbstract:Ecdysis behavior allows insects to shed their old exoskeleton at the end of every molt. It is controlled by a suite of interacting hormones and neuropeptides, and has served as a useful behavior for understanding how bioactive peptides regulate CNS function. Previous findings suggest that crustacean cardioactive peptide (CCAP) activates the Ecdysis motor program; the hormone bursicon is believed to then act downstream of CCAP to inflate, pigment, and harden the exoskeleton of the next stage. However, the exact roles of these signaling molecules in regulating Ecdysis remain unclear. Here we use a genetic approach to investigate the functions of CCAP and bursicon in Drosophila Ecdysis. We show that null mutants in CCAP express no apparent defects in Ecdysis and postEcdysis, producing normal adults. By contrast, a substantial fraction of flies genetically null for one of the two subunits of bursicon [encoded by the partner of bursicon gene (pburs)] show severe defects in Ecdysis, with escaper adults exhibiting the expected failures in wing expansion and exoskeleton pigmentation and hardening. Furthermore, flies lacking both CCAP and bursicon show much more severe defects at Ecdysis than do animals null for either neuropeptide alone. Our results show that the functions thought to be subserved by CCAP are partially effected by bursicon, and that bursicon plays an important and heretofore undescribed role in Ecdysis behavior itself. These findings have important implications for understanding the regulation of this vital insect behavior and the mechanisms by which hormones and neuropeptides control the physiology and behavior of animals.
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neuromodulation of the locust frontal ganglion during the moult a novel role for insect Ecdysis peptides
The Journal of Experimental Biology, 2006Co-Authors: Yael Zilberstein, John Ewer, Amir AyaliAbstract:In insects, continuous growth requires the periodic replacement of the exoskeleton during the moult. A moulting insect displays a stereotypical set of behaviours that culminate in the shedding of the old cuticle at Ecdysis. Moulting is an intricate process requiring tightly regulated physiological changes and behaviours to allow integration of environmental cues and to ensure the proper timing and sequence of its components. This is under complex hormonal regulation, and is an important point of interaction between endocrine and neural control. Here, we focus on the locust frontal ganglion (FG), an important player in moulting behaviour, as a previously unexplored target for Ecdysis peptides. We show that application of 10-7 mol l-1 Ecdysis-triggering hormone (ETH) or 10-7 mol l-1 and 10-6 mol l-1 Pre-Ecdysis-triggering hormone (PETH) to an isolated FG preparation caused an increase in bursting frequency in the FG, whereas application of 10-6 mol l-1 eclosion hormone (EH) caused an instantaneous, though temporary, total inhibition of all FG rhythmic activity. Crustacean cardioactive peptide (CCAP), an important peptide believed to turn on Ecdysis behaviour, caused a dose-dependent increase of FG burst frequency. Our results imply a novel role for this peptide in generating air-swallowing behaviour during the early stages of Ecdysis. Furthermore, we show that the modulatory effects of CCAP on the FG motor circuits are dependent on behavioural state and physiological context. Thus, we report that pre-treatment with ETH caused CCAP-induced effects similar to those induced by CCAP alone during pre-Ecdysis. Thus, the action of CCAP seems to depend on pre-exposure to ETH, which is thought to be released before CCAP in vivo .
Inka Zitnanova - One of the best experts on this subject based on the ideXlab platform.
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complex steroid peptide receptor cascade controls insect Ecdysis
General and Comparative Endocrinology, 2007Co-Authors: Dusan Zitnan, Inka Zitnanova, Youngjoon Kim, Ladislav Roller, Michael E AdamsAbstract:Insect Ecdysis sequence is composed of pre-Ecdysis, Ecdysis and post-Ecdysis behaviors controlled by a complex cascade of peptide hormones from endocrine Inka cells and neuropeptides in the central nervous system (CNS). Inka cells produce pre-Ecdysis and Ecdysis triggering hormones (ETH) which activate the Ecdysis sequence through receptor-mediated actions on specific neurons in the CNS. Multiple experimental approaches have been used to determine mechanisms of ETH expression and release from Inka cells and its action on the CNS of moths and flies. During the preparatory phase 1-2 days prior to Ecdysis, high ecdysteroid levels induce expression of ETH receptors in the CNS and increased ETH production in Inka cells, which coincides with expression of nuclear ecdysone receptor (EcR) and transcription factor cryptocephal (CRC). However, high ecdysteroid levels prevent ETH release from Inka cells. Acquisition of Inka cell competence to release ETH requires decline of ecdysteroid levels and beta-FTZ-F1 expression few hours prior to Ecdysis. The behavioral phase is initiated by ETH secretion into the hemolymph, which is controlled by two brain neuropeptides-corazonin and eclosion hormone (EH). Corazonin acts on its receptor in Inka cells to elicit low level ETH secretion and initiation of pre-Ecdysis, while EH induces cGMP-mediated ETH depletion and consequent activation of Ecdysis. The activation of both behaviors is accomplished by ETH action on central neurons expressing ETH receptors A and B (ETHR-A and B). These neurons produce numerous excitatory or inhibitory neuropeptides which initiate or terminate different phases of the Ecdysis sequence. Our data indicate that insect Ecdysis is a very complex process characterized by two principal steps: (1) ecdysteroid-induced expression of receptors and transcription factors in the CNS and Inka cells. (2) Release and interaction of Inka cell peptide hormones and multiple central neuropeptides to control consecutive phases of the Ecdysis sequence.
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corazonin receptor signaling in Ecdysis initiation
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Ivana Spalovskavalachova, Inka Zitnanova, Michael E Adams, Yoonseong Park, Dusan ZitnanAbstract:Corazonin is a highly conserved neuropeptide hormone of wide-spread occurrence in insects yet is associated with no universally recognized function. After discovery of the corazonin receptor in Drosophila, we identified its ortholog in the moth, Manduca sexta, as a prelude to physiological studies. The corazonin receptor cDNA in M. sexta encodes a protein of 436 amino acids with seven putative transmembrane domains and shares common ancestry with its Drosophila counterpart. The receptor exhibits high sensitivity and selectivity for corazonin when expressed in Xenopus oocytes (EC50 ≈ 200 pM) or Chinese hamster ovary cells (EC50 ≈ 75 pM). Northern blot analysis locates the receptor in peripheral endocrine Inka cells, the source of preEcdysis- and Ecdysis-triggering hormones. Injection of corazonin into pharate larvae elicits release of these peptides from Inka cells, which induce precocious preEcdysis and Ecdysis behaviors. In vitro exposure of isolated Inka cells to corazonin (25-100 pM) induces preEcdysis- and Ecdysis-triggering hormone secretion. Using corazonin receptor as a biosensor, we show that corazonin concentrations in the hemolymph 20 min before natural preEcdysis onset range from 20 to 80 pM and then decline over the next 30-40 min. These findings support the role of corazonin signaling in initiation of the Ecdysis behavioral sequence. We propose a model for peptide-mediated interactions between Inka cells and the CNS underlying this process in insect development.
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conservation of Ecdysis triggering hormone signalling in insects
The Journal of Experimental Biology, 2003Co-Authors: Dusan Zitnan, Inka Zitnanova, Yoonseong Park, Ivana Spalovska, Peter Takac, Michael E AdamsAbstract:Pre-Ecdysis- and Ecdysis-triggering hormones (PETH and ETH) from endocrine Inka cells initiate Ecdysis in moths and Drosophila through direct actions on the central nervous system (CNS). Using immunohistochemistry, we found Inka cells in representatives of all major insect orders. In most insects, Inka cells are numerous, small and scattered throughout the tracheal system. Only some higher holometabolous insects exhibit 8-9 pairs of large Inka cells attached to tracheae in each prothoracic and abdominal segment. The number and morphology of Inka cells can be very variable even in the same individuals or related insects, but all produce peptide hormones that are completely released at each Ecdysis. Injection of tracheal extracts prepared from representatives of several insect orders induces pre-Ecdysis and Ecdysis behaviours in pharate larvae of Bombyx, indicating functional similarity of these peptides. We isolated several PETH-immunoreactive peptides from tracheal extracts of the cockroach Nauphoeta cinerea and the bug Pyrrhocoris apterus and identified the gene encoding two putative ETHs in the mosquito Anopheles gambiae. Inka cells also are stained with antisera to myomodulin, FMRFamide and other peptides sharing RXamide carboxyl termini. However, our enzyme immunoassays show that these antisera cross-react with PETH and ETH. Our results suggest that Inka cells of different insects produce only peptide hormones closely related to PETH and ETH, which are essential endocrine factors required for activation of the Ecdysis behavioural sequence.
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molecular cloning and function of Ecdysis triggering hormones in the silkworm bombyx mori
The Journal of Experimental Biology, 2002Co-Authors: Dusan Zitnan, Inka Zitnanova, Laura Hollar, Ivana Spalovska, Peter Takac, Sarjeet S Gill, Michael E AdamsAbstract:Inka cells of the epitracheal endocrine system produce peptide hormones involved in the regulation of insect Ecdysis. In the silkworm Bombyx mori, injection of Inka cell extract into pharate larvae, pupae or adults activates the Ecdysis behavioural sequence. In the present study, we report the identification of three peptides in these extracts, pre-Ecdysis-triggering hormone (PETH), Ecdysis-triggering hormone (ETH) and ETH-associated peptide (ETH-AP), which are encoded by the same cDNA precursor. Strong immunoreactivity associated with each peptide in Inka cells prior to Ecdysis disappears during each Ecdysis, indicating complete release of these peptides. Injection of either PETH or ETH alone is sufficient to elicit the entire Ecdysis behavioural sequence through the direct action on abdominal ganglia; cephalic and thoracic ganglia are not required for the transition from pre-Ecdysis to Ecdysis behaviour. Our in vitro data provide evidence that these peptides control the entire Ecdysis behavioural sequence through activation of specific circuits in the nervous system. Ecdysis of intact larvae is associated with the central release of eclosion hormone (EH) and elevation of cyclic 3',5'-guanosine monophosphate (cGMP) in the ventral nerve cord. However, injection of ETH into isolated abdomens induces cGMP elevation and Ecdysis behaviour without a detectable release of EH, suggesting that an additional central factor(s) may be involved in the activation of this process. Our findings provide the first detailed account of the natural and hormonally induced behavioural sequence preceding larval, pupal and adult ecdyses of B. mori and highlight significant differences in the neuro-endocrine activation of pre-Ecdysis and Ecdysis behaviours compared with the related moth, Manduca sexta.
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dual ecdysteroid action on the epitracheal glands and central nervous system preceding Ecdysis of manduca sexta
The Journal of Experimental Biology, 2001Co-Authors: Inka Zitnanova, Dusan Zitnan, Michael E AdamsAbstract:Initiation of the Ecdysis behavioural sequence in insects requires activation of the central nervous system (CNS) by pre-Ecdysis-triggering hormone (PETH) and Ecdysis-triggering hormone (ETH), which are released from the Inka cells of the epitracheal glands. Here, we show that the developmental events preceding larval and pupal Ecdysis of Manduca sexta involve a dual action of ecdysteroids on the epitracheal glands and CNS. The low steroid levels in freshly ecdysed and feeding larvae are associated with small-sized epitracheal glands, reduced peptide production in Inka cells and insensitivity of the CNS to ETH. The elevated ecdysteroid levels before each Ecdysis lead to a dramatic enlargement of Inka cells and increased production of peptide hormones and their precursors. As blood ecdysteroids reach peak levels, the CNS becomes responsive to Inka cell peptides. These effects of natural ecdysteroid pulses can be experimentally induced by injection of 20-hydroxyecdysone or the ecdysteroid agonist tebufenozide (RH-5992) into ecdysed larvae, thus stimulating peptide production in Inka cells and inducing CNS sensitivity to ETH. A direct steroid action on the CNS is demonstrated by subsequent treatment of isolated nerve cords from ecdysed larvae with 20-hydroxyecdysone and ETH, which results in pre-Ecdysis or Ecdysis bursts. Our data show that ecdysteroid-induced transcriptional activity in both the epitracheal glands and the CNS are necessary events for the initiation of the Ecdysis behavioural sequence.