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PubMed2002

New insights in Adipokinetic Hormone (AKH) precursor processing in Locusta migratoria obtained by capillary liquid chromatography-tandem mass spectrometry.

After translation, the AKH I and AKH II precursors form three dimeric constructs prior to further processing into the respective AKHs and three dimeric Adipokinetic Hormone Precursor Related Peptides or APRPs (two homodimers and one heterodimer). By capillary liquid chromatography-tandem mass spectrometry we demonstrate that the APRPs in Locusta migratoria are further processed to form two smaller neuropeptides: DAADFADPYSFL (residue 36 to 47 of the AKH I precursor) and YADPNADPMAFL (residue 34 to 45 of the AKH II precursor). The peptides are designated as Adipokinetic Hormone Joining Peptide 1 (AKH-JP I) and 2 (AKH-JP II) respectively. Within the AKH I and AKH II precursor molecules, the classic KK and RR processing sites separate the AKH-JPs from the AKH I and II respectively. At the carboxyterminus, both AKH-JP I and II are flanked by Tyr-Arg, a cleaving site not described before. Such an unusual cleavage site suggests the presence, in the corpora cardiaca, of specific convertases. The AKH-JP-II does not stimulate lipid release from the fat body nor does it stimulate glycogen phosphorylase activity, both key functions of AKH.

Animals↗
PubMed2004

Biochemical and cytoimmunological evidence for the control of Aedes aegypti larval trypsin with Aea-TMOF.

Trypsin and chymotrypsin-like enzymes were detected in the gut of Aedes aegypti in the four larval instar and pupal developmental stages. Although overall the amount of trypsin synthesized in the larval gut was 2-fold higher than chymotrypsin, both enzymes are important in food digestion. Feeding Aea-Trypsin Modulating Oostatic Factor (TMOF) to Ae. aegypti and Culex quinquefasciatus larvae inhibited trypsin biosynthesis in the larval gut, stunted larval growth and development, and caused mortality. Aea-TMOF induced mortality in Ae. aegypti, Cx. quinquefasciatus, Culex nigripalpus, Anopheles quadrimaculatus, and Aedes taeniorhynchus larvae, indicating that many mosquito species have a TMOF-like hormone. The differences in potency of TMOF on different mosquito species suggest that analogues in other species are similar but may differ in amino acid sequence or are transported differently through the gut. Feeding of 29 different Aea-TMOF analogues to mosquito larvae indicated that full biological activity of the hormone is achieved with the tetrapeptide YDPA. Using cytoimmunochemical analysis, intrinsic TMOF was localized to ganglia of the central nervous system in larvae and male and female Ae. aegypti adults. The subesophageal, thoracic, and abdominal ganglia of both larval and adult mosquitoes contained immunoreactive cells. Immunoreactive cells were absent in the corpus cardiacum of newly molted 4th instar larvae but were found in late 4th instar larvae. In both males and females, the intrinsic neurosecretory cells of the corpus cardiacum were filled with densely stained immunoreactive material. These results indicate that TMOF-immunoreactive material is synthesized in sugar-fed male and female adults and larvae by the central nervous system cells.

Aedes↗
PubMed1991

Structure-activity studies on adipokinetic hormones in Manduca sexta.

Structure-activity studies were performed for adipokinetic hormone (AKH) in Manduca sexta. Seven naturally occurring and four synthetic peptides of the red pigment concentrating hormone (RPCH)/AKH family were tested in larvae of M. sexta for activation of glycogen phosphorylase in fat body. pGlu at the N-terminal was found to be important for activity of peptides; however, Manduca AcGly1AKH is partially active. The amino acids at all positions appear to be of importance for activity, with the possible exception of the two serine residues in positions six and seven. Generally, the more amino acids are exchanged, the less the peptide will bind to the receptor. In M. sexta a beta-bend appears not to be important for the binding of peptides. Peptides ten amino acids long appear to be more active than shorter ones.

Amino Acid Sequence↗
PubMed1993

Structural requirements for processing of pro-adipokinetic hormone I.

We found that a seven-residue sequence in pro-adipokinetic hormone I (proAKH I) which precedes the endopeptidase cleavage site is predicted to form an omega loop. Molecular modelling experiments indicated that a stable omega loop may form at this site, and suggested that loop stability may depend on the C-terminal loop residue, Lys12. The importance of this residue in proAKH I processing was confirmed by the observation that replacement of Lys12 by thialysine, a Lys analog with an altered side chain, prevented processing in vivo. In addition we showed by molecular modelling that this side-chain alteration may prevent formation of an omega loop. Together, these approaches lead us to propose that an omega loop may serve as a recognition motif in proAKH I processing.

Amino Acid Sequence↗
PubMed1995

[Genetic analysis of differences in metabolism of juvenile hormone in lines of Drosophila virilis resistant and sensitive to heat stress].

The metabolism of juvenile hormone (JH) in imagos of two Drosophila species (D. virilis and D. melanogaster) was studied in the normal state and after short-term heat stress. Females of both species respond to stress by a decrease in the activity of JH esterase. This decrease is realized through a decrease in the amount of protein. JH metabolism in males does not change after heat stress. Genetic analysis of differences in the activity of DPF-resistant JH esterase in stress-sensitive and stress-resistant strains of D. virilis was performed. The differences are controlled by one autosomal gene.

Animals↗
PubMed1993

Developmental expression of the prothoracicotropic hormone in the CNS of the tobacco hornworm Manduca sexta.

The prothoracicotropic hormone is an insect neuropeptide released into the hemolymph to signal molting and metamorphosis through its stimulation of steroidogenesis. The only known source of the prothoracicotropic hormone in the tobacco hornworm, Manduca sexta, has been a group of lateral cerebral neurosecretory cells, the L-NSC III. In this study, the developmental and spatial distribution of the prothoracicotropic hormone was examined throughout the life cycle of Manduca. In common with many vertebrates and invertebrates in which neuropeptides are located in several regions within the central nervous system (CNS), the prothoracicotropic hormone phenotype in Manduca is expressed by CNS neurons in addition to the L-NSC III. These neurons are located in the brain, frontal ganglion, and subesophageal ganglion. One cerebral neurosecretory cell group, the ventromedial neurons, expresses the prothoracicotropic hormone phenotype and the behavioral neurohormone, eclosion hormone. Whereas the L-NSC III and the ventromedial neurons express the peptide phenotype throughout the life cycle, the other neurons express the peptide only during the embryonic and larval stages. This precise spatial and temporal expression of the prothoracicotropic hormone by different groups of neurosecretory cells raises the possibility that in Manduca the peptide may, in addition to its known neuroendocrine function, play other physiological roles in different ways at different stages of the life cycle.

Animals↗
PubMed2005

The structure of the USP/RXR of Xenos pecki indicates that Strepsiptera are not closely related to Diptera.

The receptor for the insect molting hormone, ecdysone, is a heterodimer consisting of the Ecdysone Receptor and Ultraspiracle (USP) proteins. The ligand binding domain sequences of arthropod USPs divide into two distinct groups. One group consists of sequences from members of the holometabolous Lepidoptera and Diptera, while the other arthropod sequences group with vertebrate retinoid-X-receptors (RXRs). We therefore wondered whether USP/RXR structure could be used to clarify the contentious phylogenetic position of the order Strepsiptera, which has proposed affinities with either Diptera or Coleoptera. We have cloned and sequenced the USP/RXR from the strepsipteran Xenos pecki. Phylogenetic analyses are not consistent with a close affinity between Strepsiptera and Diptera.

Amino Acid Sequence↗
PubMed2004

Induced hyperlipaemia and immune challenge in locusts.

Injections of immunogens, such as beta-1,3-glucan or lipopolysaccharide (LPS), bring about a marked hyperlipaemia with associated changes in lipophorins and apolipophorin-III in the haemolymph of Locusta migratoria. These changes are similar to those observed after injection of adipokinetic hormone (AKH). The possibility that endogenous AKH is released as part of the response to these immunogens is investigated using passive immunisation against AKH-I, and measurement of AKH-I titre in the haemolymph after injection of immunogens. The data presented show that, despite the similarity of the changes brought about by the presence of immunogens in the haemolymph to those brought about by AKH, there is no release of endogenous AKH after injection of laminarin or LPS. A direct effect of the immunogens on release of neutral lipids by the fat body cannot be demonstrated in vitro, and the mechanism by which hyperlipaemia is induced during immune challenge remains uncertain.

Animals↗
PubMed1997

Prothoracicotropic hormone-producing neurosecretory cells in the silkworm, Bombyx mori, express a muscarinic acetylcholine receptor.

Using an anti-muscarinic acetylcholine receptor (mAChR) antibody and an anti-prothoracicotropic hormone (PTTH) antibody, double immunofluorescence staining was performed on brain sections of the silkworm, Bombyx mori. Four pairs of dorsolateral neurosecretory cells, along with some intercerebral neurosecretory cells, were immunoreactive to anti-mAChR antibody. Among these immunoreactive cells, two pairs of dorsolateral neurosecretory cells were identified to be PTTH-producing neurosecretory cells. Nerve fibers in the median and paramedian protocerebral areas, and nerve terminals in the corpus allatum also showed immunoreactivity to the anti-mAChR antibody. Some of these nerve terminals expressing mAChRs were overlapped by immunostaining with the anti-PTTH antibody. These results indicated that PTTH-producing neurosecretory cells of Bombyx mori expressed an mAChR, and that muscarinic, cholinergic transmission might directly regulate PTTH release from neurosecretory cells.

Animals↗
PubMed2004

Ultrastructural characteristics of circadian pacemaker neurones, immunoreactive to an antibody against a pigment-dispersing hormone in the fly's brain.

Neurones immunoreactive to an antibody against a pigment-dispersing hormone (PDH-ir) are considered to be pacemaker cells in the neuronal circadian system of flies. We investigated the ultrastructure of PDH-ir varicosities, possible releasing sites of the PDH-like peptide, in the distal medulla of the optic lobe and in the dorsal protocerebrum of the two fly species Drosophila melanogaster and Musca domestica. In both species PDH-ir varicosities show accumulation of dense core vesicles (DCVs). PDH-like peptide is localized in the DCVs as shown by post-embedding immuno-electron microscopy. Localization of PDH-like peptide in DCVs and normally lacking synaptic specializations at PDH-ir varicosities in the medulla are interpreted as a non-synaptic paracrine release of peptide.

Animals↗
PubMed2002

Ance, a Drosophila angiotensin-converting enzyme homologue, is expressed in imaginal cells during metamorphosis and is regulated by the steroid, 20-hydroxyecdysone.

Ance is a single domain homologue of mammalian angiotensin-converting enzyme (ACE) and is important for normal development and reproduction in Drosophila melanogaster. Mammalian ACE is responsible for the synthesis of angiotensin II and the inactivation of bradykinin and N -acetyl-Ser-Asp-Lys-Pro, but the absence of similar peptide hormones in insects suggests novel functions for Ance. We now provide evidence in support of a role for Ance during Drosophila metamorphosis. The transition of larva to pupa was accompanied by a 3-fold increase in ACE-like activity, which subsequently dropped to larval levels on adult eclosion. This increase was attributed to the induction of Ance expression during the wandering phase of the last larval instar in the imaginal cells (imaginal discs, abdominal histoblasts, gut imaginal cells and imaginal salivary gland). Ance expression was particularly strong in the presumptive adult midgut formed as a result of massive proliferation of the imaginal midgut cells soon after pupariation. No Ance transcripts were detected in the midgut of the fully differentiated adult intestine. Ance protein and mRNA were not detected in imaginal discs from wandering larvae of flies homozygous for the ecd ( 1 ) allele, a temperature-sensitive ecdysone-less mutant, suggesting that Ance expression is ecdysteroid-dependent. Physiological levels of 20-hydroxyecdysone induced the synthesis of ACE-like activity and Ance protein by a wing disc cell line (Cl.8+), confirming that Ance is an ecdysteroid-responsive gene. We propose that the expression of Ance in imaginal cells is co-ordinated by exposure to ecdysteroid (moulting hormone) during the last larval instar moult to increase levels of ACE-like activity during metamorphosis. The enzyme activity may be required for the processing of a developmental peptide hormone or may function in concert with other peptidases to provide amino acids for the synthesis of adult proteins.

Alleles↗
PubMed2003

Insights into the molecular basis of the hormonal control of molting and metamorphosis from Manduca sexta and Drosophila melanogaster.

This short review summarizes our current knowledge about the role of transcription factors regulated by ecdysteroids and juvenile hormone (JH) in larval molting and metamorphosis in the tobacco hornworm, Manduca sexta, and Drosophila melanogaster. We show new evidence that EcR-A/USP-2 and E75A contribute to the down-regulation of MHR3 after the peak of ecdysteroid. Also, there is suggestive evidence that both MHR4 and betaFTZ-F1 may regulate the expression of dopa decarboxylase as the ecdysteroid titer declines. We summarize the regulation by JH of the Broad transcription factor that normally appears in the epidermis in the final larval instar and specifies pupal cuticle formation at the metamorphic molt. Premature expression of different Broad isoforms also is shown to cause precocious degeneration of the prothoracic glands as well as to prevent ecdysteroid release during its presence.

Animals↗
PubMed2001

LcUSP, an ultraspiracle gene from the sheep blowfly, Lucilia cuprina: cDNA cloning, developmental expression of RNA and confirmation of function.

A DNA sequence corresponding to most of the DNA-binding domain of a Lucilia cuprina ultraspiracle protein (LcUSP) was amplified by PCR from genomic DNA and cloned. This cloned fragment was used to screen a L. cuprina cDNA library and to isolate a full-length LcUSP encoding sequence within a 3800-bp cDNA clone. The conceptually translated amino acid sequence of this open reading frame (467 amino acids) was used in alignment comparisons and phylogenetic analyses to reveal that LcUSP most closely resembles DmUSP relative to other known insect nuclear hormone receptors. An antisense RNA probe specific for the 5' end of Lcusp was used in ribonuclease protection assays to detect significant levels of Lcusp RNA throughout L. cuprina development. Highest levels were detected in embryos, late third instar larvae, pupae and adult females. This pattern parallels the pattern of expression observed for Dmusp RNAs during Drosophila melanogaster development. Finally, the LcUSP sequence was engineered for expression in mammalian cells and we now report that the cloned LcUSP is functional in vivo and can act as a partner for a chimeric L. cuprina ecdysone receptor to form an ecdysteroid-dependent transcription factor in mammalian cells.

Amino Acid Sequence↗
PubMed1989

Developmental and diurnal changes in ecdysteroid biosynthesis by prothoracic glands of Rhodnius prolixus (Hemiptera) in vitro during the last larval instar.

The synthesis of ecdysteroids by prothoracic glands (PGs) of male last instar larvae of Rhodnius prolixus was measured in vitro by radioimmunoassay throughout the course of larval-adult development. Large and systematic changes in relative rates of synthesis occur during development. Two bursts of elevated synthetic activity were found. The first commences as soon as development is initiated by a blood meal and lasts approximately 1 day. The second commences 4 days later and increases progressively to a peak at Days 11-13 after feeding (up to 25 ng of 20-hydroxyecdysone eq. gland-1/4 hr-1). The onset of each of these bursts of activity coincides with apparent times of PG stimulation in vivo by release of the prothoracicotropic hormone from the brain. Both bursts result in increases in hemolymph ecdysteroid titer measured in the donor animals. PGs exhibit an abrupt attenuation of synthesis on Day 14, which is followed by a rapid decline in the hemolymph ecdysteroid titer. Clearly, ecdysteroid synthesis by PGs is a major factor regulating the hemolymph titer. Ecdysteroid synthesis by PGs exhibits diurnal changes in vitro. The amount of ecdysteroid synthesized by PGs from animals during the scotophase is two to five times higher than that from animals during the photophase. A corresponding rhythm is seen in the hemolymph ecdysteroid titer. The rhythm in the titer is known to be under circadian control. It is therefore suggested that ecdysteroid synthesis in PGs of Rhodnius is regulated by a circadian system, possibly located in the PGs themselves.

Animals↗
PubMed2006

Flight fuel and neuropeptidergic control of fuel mobilisation in the twig wilter, Holopterna alata (Hemiptera, Coreidae).

The corpus cardiacum of the twig wilter Holopterna alata contains a factor that elicits increases in the concentration of lipids in the haemolymph of twig wilters and migratory locusts and causes hypertrehalosaemia in American cockroaches. A hyperlipaemic neuropeptide was isolated from corpora cardiaca of H. alata in a single high-performance liquid chromatography step. The primary sequence of this peptide was assigned by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, biological assay and co-elution with the synthetic peptide. The adipokinetic peptide of H. alata is an octapeptide with the sequence pGlu-Leu-Asn-Phe-Ser-Thr-Gly-Trp amide denoted Schgr-AKH-II which was sequenced previously from the corpora cardiaca of a number of Caelifera, Ensifera and some Hymenoptera. A dose of 1pmol of synthetic Schgr-AKH-II causes a pronounced hyperlipaemic effect in the twig wilter. Physiological experiments with the twig wilter reveal that during flight periods of 3 min, the normally low carbohydrate concentration in the haemolymph is significantly diminished, whereas the lipid concentration stays constant in most cases. During a subsequent rest period of 60 min after a 3 min flight episode, however, the concentration of lipids in the haemolymph increases substantially and significantly, indicating that lipids, too, are a major fuel during flight of twig wilters. This is corroborated by the activation of the enzyme triacylglycerol (TAG) lipase in the fat body, but not in the flight muscles, by injection of 5 pmol of synthetic Schgr-AKH-II, the endogenous adipokinetic hormone that is thought to be released during flight. Moreover, in the thorax there is a significant decrease in the concentration of glycogen and lipids measured after flight plus 60 min of rest compared to non-flown twig wilters, whereas no significant changes were monitored for these substrates stored in the abdomen. When the change in lipid class composition was analysed during flight plus 60 min of rest, TAG which comprised the major class in all compartments analysed (thorax, abdomen, haemolymph) was significantly reduced in abdomen and thorax, and diacylglycerol was significantly increased in all three compartments. From all the data collected, it is concluded that lipids are the major fuel class for flight in H. alata and that the contribution of carbohydrates is minimal.

Alanine↗
PubMedDate not supplied

Juvenile hormone-mediated termination of larval diapause in the bamboo borer, Omphisa fuscidentalis.

Larvae of the bamboo borer, Omphisa fuscidentalis are in diapause for more than nine months (Singtripop, T., Wanichaneewa, S., Tsuzuki, S., Sakurai, S. 1999. Larval growth and diapause in a tropical moth, Omphisa fuscidentalis Hampson. Zool. Sci. 16, 725-733). To examine the endocrine mechanisms underlying this larval diapause, we assayed the responsiveness of the diapausing larvae to 20-hydroxyecdysone (20E) and a juvenile hormone analogue (JHA: S-methoprene). 20E injection caused the larvae to halt movement, followed by deposition of a pupal cuticle. Topical application of JHA induced pupation in a dose-dependent manner. JHA also induced pupation of the larvae whose brains were removed before JHA application. In those larvae, the prothoracic glands became active and competent to respond to brain extracts within seven days after JHA treatment, and the hemolymph ecdysteroid concentration began to increase 12 days after JHA application. These results indicate that JHA stimulates the prothoracic glands of diapausing Omphisa larvae, terminating larval diapause, in contrast with previous findings that JH inhibits the brain-prothoracic gland axis and thus maintains the larval diapause. Current results therefore suggest a novel regulatory mechanism for larval diapause in this species.

Animals↗
PubMed1996

Effects of fenoxycarb on the secretory activity of the prothoracic glands in the fifth instar of the silkworm, Bombyx mori.

Effects of fenoxycarb on the secretory activity of the prothoracic glands (PGs) of the silkworm, Bombyx mori, were investigated. Fenoxycarb inhibited the secretory activity of PGs in vitro throughout the fifth instar. Incubation of PGs in the presence of 1 microgram of fenoxycarb resulted in a approximately 50% inhibition of their secretory activity. This inhibition of fenoxycarb was dose dependent. Stimulation of the PGs by recombinant prothoracicotropic hormone (rPTTH) reached a high activation ratio of 15.9. Simultaneous presence of fenoxycarb and 1 ng rPTTH significantly decreased the stimulatory effect of rPTTH on the PGs, and the activation ratio never exceeded 3.65. Early in the fifth instar, fenoxycarb strongly inhibited the secretory activity of the PGs and induced a developmental arrest as well. After the onset of pupal commitment, its action toward the PG secretory activity was inhibitory. However, fenoxycarb treatment was not able to induce a developmental arrest in intact animals after the pupal commitment although it could do so in head-ligated animals. On the contrary, application of fenoxycarb after the wandering behavior resulted in a significantly increased secretory activity by the PGs of both intact and head-ligated larvae.

Animals↗
PubMed1992

Loss of gene function through rapid mitotic cycles in the Drosophila embryo.

The early developmental period in Drosophila is characterized by rapid mitotic divisions, when the body pattern becomes organized by a cascade of segmentation gene activity. During this process localized expression of the gap gene knirps (kni) is required to establish abdomen segmentation. The knirps-related gene (knrl) encodes a kni-homologous nuclear hormone receptor-like protein and shares the spatial patterns of kni expression. The two genes differ with respect to the size of their transcription units; kni contains 1 kilobase and knrl 19 kilobases of intron sequences. The consequence of this difference in intron size is that knrl cannot substitute for kni segmentation function, although it gains this ability when expressed from an intronless transgene. Here we show that the length of mitotic cycles provides a physiological barrier to transcript size, and is therefore a significant factor in controlling developmental gene activity during short 'phenocritical' periods. The required coordination of cycle length and gene size provides severe constraints towards the evolution of rapid development.

Amino Acid Sequence↗