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PubMed2005

Analysis of molecular stereoelectronic similarity between N,N-diethyl-m-toluamide (DEET) analogs and insect juvenile hormone to develop a model pharmacophore for insect repellent activity.

Similarity analysis on molecular stereoelectronic properties of N,N-diethyl-m-toluamide (DEET), natural insect juvenile hormone (JH), a synthetic insect juvenile hormone mimic (JH-mimic, undecen-2-yl carbamate), and DEET compounds reveals remarkable similarities that lead to a reliable pharmacophore for the design of efficacious insect repellents and provide insights for understanding the mechanism of repellent action. The study involves an AM1 quantum chemical computational procedure enabling a conformational search for the lowest and most abundant energy conformers of JH, JH-mimic, and 15 DEET compounds and complete geometry optimization of the conformers. Similarity analyses of stereoelectronic properties such as structural parameters, atomic charges, dipole moments, molecular electrostatic potentials, and highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies were performed on JH, JH-mimic, and the DEET compounds. Similarity of stereoelectronic attributes of the amide/ester moiety, negative electrostatic potential regions beyond the molecular surface, and a large distribution of hydrophobic regions in the compounds appears to be the 3 important factors leading to a similar interaction with the JH receptor. The similarity of electrostatic profiles beyond the molecular surface is likely to play a crucial role toward molecular recognition interaction with the JH receptor from a distance which suggests a possible electrostatic bioisosterism of the amide group of the DEET compounds and JH-mimic and, thus, a model for molecular recognition at the JH receptor.

Aedes↗
PubMed1971

Aspects of research on insect growth hormones.

Current research on insect growth hormones includes studies on the binding of hormones to receptor molecules, probably proteins. Evidence has been obtained that this process does in fact occur and may be the means whereby the hormones "recognize" target tissues. Other studies on the possibility of a feedback effect when growth hormones are used for insect control suggest that there is a positive feedback relationship between the hormone titre and the activity of prothoracic glands and corpora allata, but the details are not yet clear. Cyclic adenosine 3',5'-monophosphate has an important role as "second messenger" in vertebrate endocrinology and may also be important in insects. Studies have shown that adenyl cyclase is present in pupal epidermis and the preliminary results have shown that it can be stimulated by a steroid hormone.

Adenylyl Cyclases↗
PubMed2001

Absence of coupling between release and biosynthesis of peptide hormones in insect neuroendocrine cells.

Adipokinetic hormone (AKH)-producing cells in the corpus cardiacum of the insect Locusta migratoria represent a neuroendocrine system containing large quantities of stored secretory peptides. In the present study we address the question whether the release of AKHs from these cells induces a concomitant enhancement of their biosynthesis. The effects of hormone release in vivo (by flight activity) and in vitro (using crustacean cardioactive peptide, locustamyoinhibiting peptide, and activation of protein kinase A and C) on the biosynthetic activity for AKHs were measured. The intracellular levels of prepro-AKH mRNAs, the intracellular levels of pro-AKHs, and the rate of synthesis of (pro-)AKHs were used as parameters for biosynthetic activity. The effectiveness of in vitro treatment was assessed from the amounts of AKHs released. Neither flight activity as the natural stimulus for AKH release, nor in vitro treatment with the regulatory peptides or signal transduction activators appeared to affect the biosynthetic activity for AKHs. This points to an absence of coupling between release and biosynthesis of AKHs. The strategy of the AKH-producing cells to cope with variations in secretory stimulation seems to rely on a pool of secretory material that is readily releasable and continuously replenished by a process of steady biosynthesis.

Animals↗
PubMed1995

Biosynthesis and distribution of insect-molting hormones in plants--a review.

Insect-molting hormones, phytoecdysteroids, have been reported to occur in over 100 plant families. Plants, unlike insects, are capable of the biosynthesis of ecdysteroids from mevalonic acid, and in several cases the biosynthesis of phytoecdysteroids was also demonstrated to proceed via sterols. Spinacia oleracea (spinach) biosynthesizes polypodine B and 20-hydroxyecdysone, which is the predominant insect-molting hormone found in plant species. The onset of ecdysteroid production in spinach requires the appropriate ontogenetic development within the plant, which is related to leaf development. In spinach, lathosterol is the biosynthetic precursor to ecdysone and 20-hydroxyecdysone. Phosphorylated ecdysteroid intermediates, particularly ecdysone-3-phosphate, are required during biosynthesis. Polyphosphorylated forms of ecdysteroids are putative regulatory components of the pathway. During spinach development, the 20-hydroxyecdysone is transported from the sites of biosynthesis to the apical regions. An analysis of the physiological data available suggests that different species may synthesize ecdysteroids in various organs and distribute these ecdysteroids to other sites. Annual plants appear to concentrate ecdysteroids in the apical regions, including flowers and seeds. Perennial plants may recycle their ecdysteroids between their deciduous and their perennial organs over the growing season. Further investigations of ecdysteroid biosynthesis and physiology within plants will be required before an acceptable system can be designed to test phytoecdysteroid effectiveness in vivo against insect herbivory.

Ecdysteroids↗
PubMed2001

Adipokinetic hormones of insect: release, signal transduction, and responses.

Flight activity of insects provides an attractive yet relatively simple model system for regulation of processes involved in energy metabolism. This is particularly highlighted during long-distance flight, for which the locust constitutes a well-accepted model insect. Peptide adipokinetic hormones (AKHs) are synthesized and stored by neurosecretory cells of the corpus cardiacum, a neuroendocrine gland connected with the insect brain. The actions of these hormones on their fat body target cells trigger a number of coordinated signal transduction processes which culminate in the mobilization of both carbohydrate (trehalose) and lipid (diacylglycerol). These substrates fulfill differential roles in energy metabolism of the contracting flight muscles. The molecular mechanism of diacylglycerol transport in insect blood involving a reversible conversion of lipoproteins (lipophorins) has revealed a novel concept for lipid transport in the circulatory system. In an integrative approach, recent advances are reviewed on the consecutive topics of biosynthesis, storage, and release of insect AKHs, AKH signal transduction mechanisms and metabolic responses in fat body cells, and the dynamics of reversible lipophorin conversions in the insect blood.

Animals↗
PubMed2006

Comparative genomics of insect juvenile hormone biosynthesis.

The biosynthesis of insect juvenile hormone (JH) and its neuroendocrine control are attractive targets for chemical control of insect pests and vectors of disease. To facilitate the molecular study of JH biosynthesis, we analyzed ESTs from the glands producing JH, the corpora allata (CA) in the cockroach Diploptera punctata, an insect long used as a physiological model species and compared them with ESTs from the CA of the mosquitoes Aedes aegypti and Anopheles albimanus. The predicted genes were analyzed according to their probable functions with the Gene Ontology classification, and compared to Drosophila and Anopheles gambiae genes. A large number of reciprocal matches in the cDNA libraries of cockroach and mosquito CA were found. These matches defined known and suspected enzymes of the JH biosynthetic pathway, but also several proteins associated with signal transduction that might play a role in the modulation of JH synthesis by neuropeptides. The identification in both cockroach and mosquito CA of homologs of the small ligand binding proteins from insects, Takeout/JH binding protein and retinol-binding protein highlights a hitherto unsuspected complexity of metabolite trafficking, perhaps JH precursor trafficking, in these endocrine glands. Furthermore, many reciprocal matches for genes of unknown function may provide a fertile ground for an in-depth study of allatal-specific cell physiology. ESTs are deposited in GenBank under the accession numbers DV 017592-DV 018447 (Diploptera punctata); DR 746432-DV 747949 (Aedes aegypti); and DR 747950-DR 748310 (Anopheles albimanus).

Aedes↗
PubMedDate not supplied

Molecular similarity analysis between insect juvenile hormone and N, N-diethyl-m-toluamide (DEET) analogs may aid design of novel insect repellents.

Molecular similarity analysis of stereoelectronic properties between natural insect juvenile hormone (JH), -a synthetic insect juvenile hormone mimic (JH-mimic, undecen-2-yl carbamate), and N, N-diethyl-m-toluamide (DEET) and its analogs reveals similarities that may aid the design of more efficacious insect repellents and give a better insight into the mechanism of repellent action. The study involves quantum chemical calculations using the AM1 semi-empirical computational method enabling a conformational search for the lowest and most abundant energy conformers of JH, JH-mimic, and 15 DEET compounds, followed by complete geometry optimization of the conformers. Similarity analyses of stereoelectronic properties such as structural parameters, atomic charges, dipole moments, molecular electrostatic potentials, and highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies were performed on JH, JH-mimic and the DEET compounds. The similarity of stereoelectronic attributes of the amide/ester moiety, the negative electrostatic potential regions beyond the van der Waals surface, and the large distribution of hydrophobic regions in the compounds appear to be the three important factors leading to a similar interaction with the JH receptor. The similarity of electrostatic profiles beyond the van der Waals surface is likely to play a crucial role in molecular recognition interaction with the JH receptor from a distance. This also suggests electrostatic bioisosterism of the amide group of the DEET compounds and JH-mimic and, thus, a model for molecular recognition at the JH receptor. The insect repellent property of the DEET analogs may thus be attributed to a conflict of complementarity for the JH receptor binding sites.

Algorithms↗
PubMed1993

Development of an enzyme immunoassay for arginine-vasopressin (AVP)-like insect diuretic hormone.

1. The AVP-like insect diuretic hormone is a biologically active antiparallel dimer present, along with its non-active monomeric form (Cys-Leu-Ile-Thr-Asn-Cys-Pro-Arg-GlyNH2), in the African locust. 2. It exhibits diuretic activity by increasing fluid excretion at the level of the Malpighian tubules. 3. To date, both monomer and dimer have been assayed using a radioimmunoassay originally prepared for mammalian AVP. 4. We have developed here an original enzyme immunoassay based on the use of antibodies to insect AVP-like raised in rabbits against synthetic monomers and dimers, using acetylcholinesterase conjugate as an enzymatic tracer. 5. This enzyme immunoassay enables measurement of the dimer to be made with adequate sensitivity (0.3 nmol/l, i.e. 21 pg/well) and reproducibility while sensitivity of the monomer is somewhat lower (14 nmol/l, i.e. 480 pg/well). 6. The assay was validated by assaying native dimer and monomer throughout the different steps of purification (from a crude extract to reversed-phase liquid chromatographic fractions). 7. A good correlation was observed between radioimmunoassays and enzyme immunoassays. 8. The enzyme immunoassay was also used to measure the level of AVP-like peptides in several insect tissues not explored to date.

Amino Acid Sequence↗
PubMed1996

A new nonsteroidal chemical class of ligand for the ecdysteroid receptor 3, 5-di-tert-butyl-4-hydroxy-N-isobutyl-benzamide shows apparent insect molting hormone activities at molecular and cellular levels.

Insect molting hormones, ecdysteroids, found in natural products so far have steroidal structures. However, nonsteroidal ecdysteroid agonists show promise as a new type of insecticide and may be useful as probes for the biochemical study of ecdysteroids. 3, 5-Di-tert-butyl-4-hydroxy-N-isobutyl-benzamide (DTBHIB), discovered by the combination of the automated ecdysteroid receptor binding assay and the ecdysteroid responsive gene expression assay, showed both ecdysteroid receptor binding activity and induction activities of ecdysteroid responsive genes. Furthermore, the inhibition of the Kc cell proliferation and the induction of the cell process protrusion were observed in the presence of DTBHIB in a dose response manner. A similar compound of DTBHIB, however, could neither bind the receptor nor induce the responsive gene. These results provide strong evidence for the ecdysteroid agonist activity of DTBHIB, which has a novel nonsteroidal chemical structure, and might be a valuable lead chemical for higher potential ecdysteroid agonists.

Animals↗
PubMed2006

Regulation of insect steroid hormone biosynthesis by innervating peptidergic neurons.

In insects, steroid hormones named ecdysteroids elicit molting and metamorphosis. The prothoracic gland (PG) is a predominant source of ecdysteroids, where their biosynthesis (ecdysteroidogenesis) is regulated by several neuropeptides. Here, we report that FMRFamide-related peptides (FaRPs) regulate ecdysteroidogenesis through direct innervation of the PG in the silkworm Bombyx mori. We purified a previously uncharacterized Bombyx FaRP, DPSFIRFamide, and identified the corresponding Bombyx FMRFamide gene (Bommo-FMRFamide, BRFa), which encodes three additional FaRPs. All BRFa peptides suppressed ecdysteroidogenesis in the PG by reducing cAMP production by means of the receptor for Bommo-myosuppressin, another FaRP we have previously shown to act as a prothoracicostatic factor. BRFa is predominantly expressed in neurosecretory cells of thoracic ganglia, and the neurons in the prothoracic ganglion innervate the PG to supply all four peptides to the gland surface. Electrophysiological recordings during development confirmed the increased firing activity of BRFa neurons in stages with low PG activity and decreased ecdysteroid levels in the hemolymph. To our knowledge, this study provides the first report of peptides controlling ecdysteroidogenesis by direct innervation.

Amino Acid Sequence↗
PubMed1994

Expression cloning of an insect diuretic hormone receptor. A member of the calcitonin/secretin receptor family.

Insect diuretic hormones and their receptors regulate fluid and ion secretion and thus are attractive targets for the design of novel insect control agents. A complementary DNA clone encoding a corticotropin-releasing factor-related diuretic hormone receptor from the tobacco hornworm Manduca sexta was isolated by expression cloning in COS-7 cells. The receptor consists of 395 amino acids and contains seven putative transmembrane domains. The expressed receptor binds M. sexta diuretic hormone, as well as several related insect diuretic peptides with high affinity. Furthermore, each of these peptides stimulate adenylate cyclase in COS-7 cells transfected with the receptor. The M. sexta diuretic hormone receptor is homologous to the receptors for calcitonin, secretin, vasoactive intestinal peptide, parathyroid hormone, glucagon-like peptide 1, growth hormone-releasing hormone, pituitary adenylate cyclase-activating polypeptide, and glucagon. The M. sexta diuretic hormone receptor is the first nonmammalian member of this family to be identified.

Amino Acid Sequence↗
PubMed2000

Organizational and activational effects of hormones on insect behavior.

The concepts of hormone organization and activation provide a framework for thinking about the influence of hormones on development, brain, and behavior in vertebrates. There is good evidence for activational effects of hormones on the nervous system and behavior in insects, but organizational effects are almost never discussed in the insect literature. This paper explores the utility of the concepts of hormonal organization and activation of behavior in insects. We describe the two concepts as developed from studies of vertebrates, review some insect examples that appear to fit this classification scheme, and consider how explicit use of the concept of organization might benefit studies of the insect brain and behavior.

Journal Article↗
PubMed2001

Conformational study of insect adipokinetic hormones using NMR constrained molecular dynamics.

Mem-CC (pGlu-Leu-Asn-Tyr-Ser-Pro-Asp-Trp-NH2), Tem-HrTH (pGlu-Leu-Asn-Phe-Ser-Pro-Asn-Trp-NH2) and Del-CC (pGlu-Leu-Asn-Phe-Ser-Pro-Asn-Trp-Gly-Asn-NH2) are adipokinetic hormones, isolated from the corpora cardiaca of different insect species. These hormones regulate energy metabolism during flight and so are intimately involved in an insect's mobility. Secondary structural elements of these peptides and the N7 analogue, [N7]-Mem-CC (pGlu-Leu-Asn-Tyr-Ser-Pro-Asn-Trp-NH2), have been determined in dimethylsulfoxide solution using NMR restrained molecular mechanic simulations. The neuropeptides were all found to have an extended structure for the first 4 residues and a beta-turn between residues 4-8. For Tem-HrTH and Del-CC, asparagine (N7) which is postulated to be involved in receptor binding and/or activation, projects outward form the beta-turn. Mem-CC does not have an asparagine at position 7 while, for [N7]-Mem-CC, the N7 sidechain folds inside the beta-turn preventing its interaction with the receptor.

Amino Acid Sequence↗
PubMed1989

13C-NMR assignments of some insect molting hormones.

13C-NMR assignments of some insect molting hormones including ecdysone, 20-hydroxyecdysterone, ponasterone A and inokosterone, were made by using ecdysone as the model compound, whose carbon chemical shifts were assigned via NMR techniques including nOe and COSY, hetero-COSY and hetero-long range-COSY.

Ecdysone↗
PubMed1988

A monoclonal antibody to the insect prothoracicotropic hormone.

The prothoracicotropic hormone (PTTH) is an insect cerebral peptide that stimulates the prothoracic glands to produce the steroid hormone ecdysone thus initiating molting and metamorphosis. "Big" PTTH, one of several molecular forms of the neurohormone, was isolated from brains of the tobacco hornworm Manduca sexta, and fractionated by high-pressure liquid chromatography (HPLC) for use in antibody production. A murine polyclonal antiserum and a monoclonal antibody (MAb) have been generated using this highly purified preparation of big PTTH. Antisera and hybridoma supernatants were screened with an indirect, brain whole-mount immunocytological assay, and antibody specificity was confirmed by immunocytological, ELISA, and functional criteria. In brain whole-mount preparations, the MAb (A2H5) and antiserum specifically immunostained the lateral protocerebral neurosecretory cells (L-NSC III), the prothoracicotropes, which produce PTTH. This immunostaining was blocked by preadsorbing the antibodies with big PTTH. Analysis of the elution of HPLC-fractionated big PTTH with an in vitro bioassay for the neurohormone and an ELISA employing the A2H5 MAb resulted in peaks of activity that were superimposable. Finally, the antiserum and A2H5 MAb inhibited big PTTH activation of the prothoracic glands to synthesize ecdysone in the in vitro bioassay for the neurohormone. With these specific antibodies, the organization of the PTTH neuroendocrine axis has been defined. It is now evident that both of the peptidergic neurons that comprise the L-NSC III are prothoracicotropes, and that the corpora allata are the neurohemal organs for the release of big PTTH into the hemolymph. This study indicates that these specific antibodies will be useful in investigations of numerous aspects of the biology of this cerebral neuroendocrine axis.

Animals↗
PubMed1992

Insect peptide hormones, an overview of the present literature.

A comprehensive overview of the recent state of the art of insect peptide hormones with chemical structures is presented. An increased interest in insect neuropeptides and dynamic development of that research area has been influenced by a rapid improvement of instrumentation necessary for isolation and structural characterization. Several research teams have studied the relationships between biological properties of insect and vertebrate peptide hormones. Thus hormones from the AKH family can be considered glucagon counterparts, whereas the myotropic hormones such as proctolin and Lem-PK (LPK) are a substance P equivalent. Insect melanization hormones Bom-MRCH in their structural characteristics and properties resemble those of mammal MSH, and leucosulfakinins Lem-SK-I and -II show some similarities with gastrin II and cholecystokinin. Bombyxin-II (Bom-PTTH-II) reveals a structural homology with human insulin and similar biological properties to adenocorticotropic mammal hormone. Allatostatin (Dip-JHS-I) may be compared to somatostatin as it can be inferred from the observations that this peptide modulates JH secretion in cockroach, Blattella germanica. Determination of the primary structure of eclosion hormones Mas-EH and Bom-EH-II as well as the amino acid sequence of allatotropin and allatostatin is a significant contribution to the understanding of the molecular mechanisms of metamorphosis and insect development.

Amino Acid Sequence↗