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PubMed1990

Molecular cloning, regulation, and complete sequence of a hemocyanin-related, juvenile hormone-suppressible protein from insect hemolymph.

A cDNA library was prepared from mRNA isolated from the lepidopteran Trichoplusia ni during larval-pupal metamorphosis. Differential probing was used to identify clones for mRNAs which are suppressible by exogenous juvenile hormone treatment. In vitro transcribed cRNAs from these clones were translated in vitro and challenged with antiserum specific for a known acidic, juvenile hormone-suppressible hemolymph protein (AJSP-1) that is associated with larval metamorphosis. Three clones were found which encoded immunoreactive translation products; their identity was confirmed by comparison of the N-terminal sequence of the mature AJSP-1 protein with the cDNA sequence. As inferred from the cDNA sequence, the protein encompasses 704 amino acid residues, including a N-terminal signal peptide; widely distributed as well as more localized stronger sequence similarities indicate that the protein is distantly related to hemocyanins and hemocyanin-like insect proteins. However, on the basis of amino acid sequence and composition, immunological reactivity, and hormonal sensitivity, the protein is distinct from previously described insect proteins. Its juvenile hormone suppressibility can be ascribed to suppression of the mRNA. RNA blot analysis using the cloned cDNA as a probe demonstrated that the transcript (approximately 2.8 kilobases) is of very low abundance during the penultimate stadium but becomes very abundant during the last larval stadium, when juvenile hormone rapidly declines. Furthermore, treatment of larvae with a juvenile hormone analog strongly suppresses the abundance of the message.

Amino Acid Sequence↗
PubMed2007

A simple purification protocol for the detection of peptide hormones in the hemolymph of individual insects by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

The endocrine system of insects is largely based on peptide hormones. Nevertheless, an unequivocal chemical demonstration of the occurence in the hemolymph (the 'insect blood') is still lacking for most if not all insect peptide hormones, although this is the only way to prove their hormonal status. Focusing on peptides released during ecdysis behavior of the tobacco hornworm Manduca sexta, we developed a purification protocol based on ultrafiltration and a single reversed-phase high-performance liquid chromatography (RP-HPLC) step that for the first time allowed the mass spectrometric and chemical identification of a peptide hormone in the hemolymph of single specimens. Since this method is simple, relatively cheap and fast, it should be useful for routine endocrinological analyses and for monitoring peptide release during different physiological conditions and behaviors in insects.

Animals↗
PubMed2005

Manduca sexta prophenoloxidase activating proteinase-1 (PAP-1) gene: organization, expression, and regulation by immune and hormonal signals.

Insect phenoloxidase (PO) participates in melanotic encapsulation, wound healing, and cuticle sclerotization. It is converted from prophenoloxidase (proPO) by a proPO-activating proteinase (PAP). Manduca sexta PAP-1, the final component of a serine proteinase cascade, cleaves proPO to generate active PO. In an effort to understand the transcriptional regulation, we isolated a genomic clone of the PAP-1 gene, determined its nucleotide sequence, and elucidated its exon-intron organization. Computer analysis revealed several immune and hormone responsive elements in the upstream region. Southern blot analysis suggested that the M. sexta genome contains a single copy of PAP-1 gene. Reverse transcription-polymerase chain reaction showed that PAP-1 was constitutively expressed in fat body, trachea, and nerve tissue of the fifth instar larvae. The mRNA levels in hemocytes and fat body markedly increased in response to a bacterial challenge. We also observed tissue-specific and developmental regulation of the gene's transcription. Treating M. sexta fat body culture with 20-hydroxyecdysone reduced the PAP-1 mRNA level. These data indicated that the expression of PAP-1 gene is under the dual control of immune and hormonal signals.

Amino Acid Sequence↗
PubMed1991

Human thyroid hormone beta 1 receptor produced by recombinant baculovirus-infected insect cells.

Thyroid hormone receptors are nuclear proteins which regulate transcription in a hormone dependent manner. The baculovirus expression system was used for the overexpression of the beta 1 isoform of the human thyroid hormone receptor. The baculovirus produced receptor binds tri-iodothyronine with high affinity, is specifically immunoprecipitated with a beta 1 specific antibody, and binds to DNA that contains a known thyroid hormone receptor recognition site. Large scale production and purification of baculovirus produced receptor will be useful for structure-function analyses and studies of transcriptional regulation.

Animals↗
PubMed1996

Juvenile hormone regulation of an insect gene: a specific transcription factor and a DNA response element.

We have used locust fat body nuclear protein extracts and upstream DNA of the juvenile hormone (JH)-inducible locust gene, jhp21, to examine the regulation of specific transcription by JH. Promoter activity was assayed with G-free cassette reporter constructs. Nuclear extracts from adult female fat body, previously exposed to JH or an analog, actively transcribe from the jhp21 promoter and a control adenovirus major late (AdML) promoter, whereas extracts from JH-deprived female fat body, or other tissues, transcribe strongly from the AdML promoter but weakly or not at all from the jhp21 promoter. Transcription is enhanced by sequences between -140 and -211 nt from the jhp21 transcription start point (tsp), which include a CAAT box, and also by sequences between -1056 and -1200. A 15-nt partially palindromic sequence element found at -1152, resembling known hormone response elements, was shown to stimulate transcription when restored to truncated jhp21 DNA. Two very similar sequences occur further upstream. In electrophoretic mobility shift assays (EMSA), the same sequence element was shown to specifically bind a protein that was present in nuclear extracts from JH-exposed, but not from JH-deprived, fat body. Several lines of evidence suggest that the DNA element may be a JH response element (JHRE). The JH-induced protein that binds to it appears to be a transcription factor that activates the initiation of JH target gene (jhp21) transcription, and could be a JH receptor.

Animals↗
PubMed2005

Activation of triacylglycerol lipase in the fat body of a beetle by adipokinetic hormone.

The activation of triacylglycerol lipase and the stimulation of proline synthesis in the fat body of the fruit beetle Pachnoda sinuata by the endogenous octapeptide hormone Melme-CC (pQLNYSPDWa), which belongs to the family of insect adipokinetic hormones, were studied, and the correlation of both events investigated. At rest, the activity of triacylglycerol lipase in the fat body of the beetle was higher than in the fat body of the American cockroach, Periplaneta americana, but lower than in the migratory locust, Locusta migratoria. Triacylglycerol lipase of the beetle is activated by: (a) injection of synthetic Melme-CC and (b) the stimulus of flight. Activation of lipase by Melme-CC is time-dependent. Injection of cpt-cAMP activates triacylglycerol lipase in the fat body and causes an increase in the concentration of proline in the haemolymph at the expense of alanine. In contrast, injection of F-inositol-1,4,5-phosphate does not affect the activation state of lipase, nor the levels of amino acids in the haemolymph. High doses of octopamine do not activate lipase. Furthermore, activity of fat body lipase and proline concentration in the haemolymph both follow a circadian rhythm: both parameters are high in the morning, whereas they are low in the evening. When transfer of Melme-CC, released from the corpora cardiaca, to the thorax/abdomen is prevented by neck-ligation, the activity of lipase, as well as the circulating proline levels are low. Regression analysis revealed that activity of triacylglycerol lipase is positively correlated to proline concentration in the haemolymph, whereas there is a negative correlation of the enzyme activity and alanine level in the haemolymph. From these results we conclude that the activation of fat body triacylglycerol lipase by Melme-CC in P. sinuata stimulates proline synthesis. Proline is one of the major substrates to power flight activity in the beetle.

Animals↗
PubMed2006

Adipokinetic hormones in the African malaria mosquito, Anopheles gambiae: identification and expression of genes for two peptides and a putative receptor.

Adipokinetic hormones (AKHs) are neuropeptides that mobilize stored fuels for flight in insects, and thus, may regulate flight by mosquitoes that transmit pathogens of human diseases. Our study of AKHs in the African malaria mosquito, Anopheles gambiae, identified and characterized the expression of genes encoding two AKHs, Anoga-AKH-I (pQLFTPAWa) and Anoga-AKH-II (pQVTFSRDWNAa), and a putative homolog for an AKH G-protein coupled receptor. Gene transcripts for both Anoga-AKHs and the AKH receptor were present in eggs, larvae, pupae, and adults of An. gambiae. In females, these transcripts were apparent in heads and thoraces for up to 72 h after blood or sugar feeding, as revealed by RT-PCR. With immunocytochemistry, a cluster of neurosecretory cells posterior to the corpus cardiacum and specific cells in the brain and thoracic ganglia of females were immunostained with an AKH antibody, which recognizes both Anoga-AKHs. Accordingly, Anoga-AKH-I was detected in extracts of female heads and thoraces by HPLC and an AKH radioimmunoassay, whereas Anoga-AKH-II was detected only in heads.

Adipogenesis↗
PubMed1999

Ligand regulation of juvenile hormone binding protein mRNA in mutant Manduca sexta.

Insect hemolymph juvenile hormone binding protein (hJHBP) regulates peripheral titers of its ligands, the juvenile hormones. In larvae of the black (bl) strain of the tobacco hornworm, Manduca sexta, treatment with small doses of juvenile hormone I (JH I) can also regulate titers of hJHBP. To further investigate this regulation, responsiveness of hJHBP mRNA expression to JH I was characterized in vivo. RNA analyzes revealed that transcript levels in fat body, the site of hJHBP synthesis, increased fivefold within several hours of treatment with physiological doses of hormone and remained elevated for approximately 16 h. Sensitivity to JH treatment was found to vary temporally. To ensure transcript identity, a wild-type cDNA clone and a bl RT-PCR fragment were sequenced and found to be 99% homologous. Together, these results suggest that JH participates in regulating expression of its transport protein in bl larvae by modifying the in vivo abundance of hJHBP's mRNA transcript.

Amino Acid Sequence↗
PubMed1977

Prothoracicotropic hormone in Manduca sexta: localization by a larval assay.

1. A new method for the assay of insect prothoracicotropic hormone (PTTH) is described, using fourth instar larvae of Manduca sexta. Larvae neck-ligated at a critical time to prevent release of PTTH from the head fail to undergo the next larval moult. Such ligated larvae moult to fifth instar larvae or larval-pupal intermediates after injection of brain homogenates from Manduca larvae, pupae or pharate adults. The degree of response is proportional to the concentration of brain homogenate injected. 2. The source of PTTH in the pupal brain is the dorsal region of the protocerebrum containing the lateral neurosecretory cells. Microhomogennates of single pieces of brain showed activity with this method. 3. PTTH activity in partially purified extracts is water soluable, stable to boiling for 10 min, and is destroyed by Pronase or trypsin.

Animals↗
PubMed2002

Interactions between Spinacia oleracea and Bradysia impatiens: a role for phytoecdysteroids.

Plant produced insect molting hormones, termed phytoecdysteroids (PEs), are thought to function as plant defenses against insects by acting as either feeding deterrents or through developmental disruption. In spinach (Spinacia oleracea), 20-hydroxyecdysone (20E) concentrations in the roots rapidly increase following root damage, root herbivory, or methyl jasmonate (MJ) applications. In this inducible system, we investigated the plant defense hypothesis by examining interactions of roots, 20E concentrations, and larvae of the dark-winged fungus gnat (Bradysia impatiens). Root herbivory by B. impatiens larvae resulted in a 4.0- to 6.6-fold increase in root 20E concentrations. In paired-choice tests, increases in dietary 20E stimulated B. impatiens feeding deterrency. B. impatiens larvae preferred control diets, low in 20E, to those constructed from induced roots and those amended with 20E (25 to 50 micro g/g wet mass). When confined to 20E-treated diets, concentrations as low as 5 micro g/g (wet mass) resulted in significantly reduced B. impatiens survivorship compared to controls. The induction of root 20E levels with MJ resulted in a 2.1-fold increase in 20E levels and a 50% reduction in B. impatiens larval establishment. In a paired-choice arena, untreated control roots were damaged significantly more by B. impatiens larvae than MJ-induced roots that contained 3-fold greater 20E levels. Based on dietary preference tests, the 20E concentrations present in the MJ-induced roots (28 micro g/g wet mass) were sufficient to explain this reduction in herbivory. Interactions between spinach roots and B. impatiens larvae demonstrate that PEs can act as inducible defenses and provide protection against insect herbivory.

Acetates↗
PubMed1987

Time course of hormonal independence for developmental events in neurons and other cell types during insect metamorphosis.

The ecdysteroid dependence of developmental events during the larval-pupal transformation of the tobacco hornworm, Manduca sexta, was studied using the technique of abdomen ligation to eliminate the ecdysteroid-secreting prothoracic glands (PTG) in the thorax. The time at which a particular developmental event no longer required the presence of the PTG for its successful completion, i.e., when the event became ecdysteroid independent, was determined for the dendritic regression and death of proleg motor neuron PPR, the degeneration of its target muscle PPRM, and the secretion of pupal cuticle by the abdominal epidermis. Groups of abdomens were ligated from synchronously developing larvae at 12-hr intervals over the 4-day period preceding entry into the pupal stage. PPR's dendritic regression became ecdysteroid independent over the first 24 hr of this period. When abdomens were ligated midway through this period PPR became arrested in a partially regressed state. Twelve hours after PPR's regression became independent, the degeneration of PPRM and the secretion of pupal cuticle by the epidermis acquired independence. Another 12 hr elapsed before PPR's programmed death became independent. Thus, different developmental events acquired ecdysteroid independence in a stereotyped temporal sequence, and even different events within a single cell, i.e., PPR's regression and death, became independent at different times.

Abdomen↗
PubMed2000

[Hormonal regulation of gametogenesis in insect].

The review discusses the role of juvenile hormone (JH), ecdysone and brain in the regulation of oogenesis and spermatogenesis in insects. The early period of gametogenesis (gonial mitoses, the meiotic prophase) in both sexes is controlled mainly by ecdysone and neurosecretory cells of the brain. In periods of cytoplasmic growth of oocytes and vitellogenesis the main role in the regulation belongs to JH. The modern views on hormonal regulation of vitellogenin synthesis and follicular epithelium differentiation are under consideration with a special reference of the role of ecdysteroids in Diptera and Lepidoptera oogenesis.

Animals↗
PubMed1997

Rat gonadotropin-releasing hormone receptor expressed in insect cells induces activation of adenylyl cyclase.

Increasing evidence exist that multiple G proteins mediate the effects of gonadotropin-releasing hormone (GnRH) on the synthesis and release of pituitary gonadotropins. In the present study, we have expressed the rat GnRH receptor (GnRH-R) in insect cells, by infection with a recombinant baculovirus. Under the conditions used, insect cells expressed, 48 h post-infection, a maximum of 7800 +/- 650 receptors/cell which bound GnRH agonist [D-Trp6]GnRH with a Kd = 0.52 +/- 0.06 nM indicating characteristics similar to those of the natural receptor. No binding was observed in non-infected cells or cells infected with wild-type baculovirus. In presence of GnRH, GnRH-R expressing cells elicited a time- and dose-dependent production of inositol trisphosphate, with a maximum level reached within 30 min and an EC50 = 5 nM. These recombinant insect cells also produced cAMP in response to GnRH. However, in contrast to other heterologous systems, or rat pituitary gonadotropes wherein GnRH induced a weak and delayed elevation of cAMP, in insect cells the rise of cAMP was comparatively rapid, attaining a maximum level after 2 h, and the EC50 was 5 nM. Finally, a clear activation of adenylyl cyclase (AC) in response to GnRH was shown for the first time by measuring the conversion of [alpha-32P]ATP into labeled cAMP, using membrane preparations from GnRH-R expressing insect cells. These data demonstrate that rat GnRH-R has the potential for dual coupling to both phosphoinositidase C and AC and suggest a major influence of the host cell for this coupling and/or its expression, probably in relation with the G protein repertoire and preference. This notion could be extended to several target cells other than pituitary gonadotropes that normally express the GnRH-R in mammals, including hippocampal, Leydig, granulosa, placental and GnRH-secreting hypothalamic cells.

Adenylyl Cyclases↗
PubMed2006

Can juvenogens, biochemically targeted hormonogen compounds, assist in environmentally safe insect pest management?

Two different types of juvenogens, biochemically targeted hormonogen compounds were tested for their potency to act as insect pest management agents. In the performed biological screening, wax-like esteric juvenogens (3-10) proved to be convenient agents for controlling blowfly and termites, and displayed species selectivity: cis-N-{2-[4-(2-butanoyloxycyclohexyl)methyl]phenoxy}ethyl carbamate (3) was highly active on blowfly (Neobellieria bullata), while trans-N-{2-[4-(2-hexadecanoyloxycyclohexyl)methyl]-phenoxy}ethyl carbamate (6) showed high activity on termite (Prorhinotermes simplex). Glycosidic juvenogens, isomeric N-{2-{4-{[2-(beta-D-galactopyranosyloxy)cyclohexyl]methyl}phenoxy}ethyl carbamates (13 and 14), were proved to act as systemic agents, suitable for protecting plants against phytophagous insects (e.g. aphids). Due to the prolonged action of juvenogens, which is connected with the sequential liberating of the biologically active molecule of the insect juvenile hormone bioanalog from the juvenogen molecule by means of enzymic systems of target insects and/or their host plants, more insect individuals can be treated by juvenogens, which are species-targeted structures due to their different physicochemical properties. The results achieved with both types of juvenogens were promising, concerning their final effect on the tested insect species, and the compounds 3-6, 9 (cis-(9Z)-N-{2-[4-(2-(octadec-9-enoyl)oxycyclohexyl)methyl]phenoxy}ethyl carbamate), 13 and 14 proved to represent convenient insect pest management agents for potential practical applications against different insect pests.

Animals↗
PubMed1995

Drosophila hormone receptor 38: a second partner for Drosophila USP suggests an unexpected role for nuclear receptors of the nerve growth factor-induced protein B type.

In Drosophila the response to the hormone ecdysone is mediated in part by Ultraspiracle (USP) and ecdysone receptor (EcR), which are members of the nuclear receptor superfamily. Heterodimers of these proteins bind to ecdysone response elements (EcREs) and ecdysone to modulate transcription. Herein we describe Drosophila hormone receptor 38 (DHR38) and Bombyx hormone receptor 38 (BHR38), two insect homologues of rat nerve growth factor-induced protein B (NGFI-B). Although members of the NGFI-B family are thought to function exclusively as monomers, we show that DHR38 and BHR38 in fact interact strongly with USP and that this interaction is evolutionarily conserved. DHR38 can compete in vitro against EcR for dimerization with USP and consequently disrupt EcR-USP binding to an EcRE. Moreover, transfection experiments in Schneider cells show that DHR38 can affect ecdysone-dependent transcription. This suggests that DHR38 plays a role in the ecdysone response and that more generally NGFI-B type receptors may be able to function as heterodimers with retinoid X receptor type receptors in regulating transcription.

Amino Acid Sequence↗
PubMed1994

The brain secretory peptides that control moulting and metamorphosis of the silkmoth, Bombyx mori.

Progress made toward the elucidation of molecular features of the prothoracicotropic hormone (PTTH) of the silkmoth Bombyx mori is reviewed. PTTH stimulates the prothoracic glands to synthesize and release ecdysone, and is therefore a key hormone for the regulation of insect moulting and metamorphosis. Bombyx PTTH is a 30 kDa homodimeric glycoprotein, whose carbohydrate moiety is not essential for the biological function. The Bombyx genome contains a single copy of the PTTH gene. PTTH is produced by four dorsolateral neurosecretory cells of brain. Another Bombyx brain peptide exerting prothoracicotropic activity to a heterologous moth Samia cynthia ricini but no activity to Bombyx has been identified and termed bombyxin. Bombyxin is a 5 kDa heterodimeric peptide that shows a high similarity to insulin in the amino acid sequence. The bombyxin gene structure also shows a high similarity with the insulin gene structure. The Bombyx genome contains more than 30 copies of the bombyxin gene. Bombyxin is synthesized by eight dorsomedial neurosecretory cells of brain.

Amino Acid Sequence↗