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PubMed1989

Dimer structure of a neuropeptide precursor established: consequences for processing.

A prohormone (P1) of locust adipokinetic hormone I (AKH I) is shown here to be a homodimer of a 41 residue subunit called the A-chain. The A-chain, from the N terminal, consists of AKH I (10 amino acids starting with pyroglutamate) followed by a Gly-Lys-Arg processing site and then a 28 residues called the alpha chain containing a single cysteine and a potential Arg-Lys processing site. When processed each molecule of the homodimer precursor yields two copies of AKH I and one alpha chain homodimer. We call the alpha-alpha homodimer product of P1 processing AKH precursor related peptide 1 or APRP 1. The Arg-Lys dibasic pair found within the alpha chain is not cleaved in vivo. Our results show that neuropeptide precursors can be dimers and that dimer products can be synthesized by processing of a preformed dimer precursor rather than by dimerization of independent subunits.

Amino Acid Sequence↗
PubMed1995

In vitro hormonal regulation of glycogen phosphorylase activity in fat body of the tropical cockroach, Blaberus discoidalis.

Blaberus hypertrehalosemic hormone (Bld-HTH)-dependent glycogen phosphorylase activation was investigated using in vitro fat bodies from the cockroach, Blaberus discoidalis. Resting levels of active phosphorylase were decreased by the presence of trehalose and glucose. Phosphorylase activation was dose-responsive to Bld-HTH and increased ca. 3-fold over a range of 0.02 to 2 nM Bld-HTH. Maximum phosphorylase activation required only 5-min exposure to Bld-HTH; reversion to the inactive state began within 15 min after Bld-HTH removal and was completed by 60 min. Octopamine also activated phosphorylase but required 10(3)-fold higher concentrations than did Bld-HTH. Concentrations of Bld-HTH and octopamine that increased active phosphorylase did not elevate fat body cAMP levels, although a high concentration of octopamine increased tissue cAMP levels. cAMP did not increase phosphorylase activity, but Ca2+ was important for both Bld-HTH- and octopamine-dependent phosphorylase activation.

Animals↗
PubMed2006

Stage-dependent effects of starvation on the growth, metamorphosis, and ecdysteroidogenesis by the prothoracic glands during the last larval instar of the silkworm, Bombyx mori.

The stage-dependent effects of starvation on the growth, metamorphosis, and ecdysteroidogenesis of the prothoracic glands during the last larval instar of the silkworm, Bombyx mori, were studied in the present study. When last instar larvae were starved beginning on day 1 of that instar, all larvae died between days 5 and 7 of the instar. Although the prothoracicotropic hormone (PTTH) release from the brain-corpus cardiacum-corpus allatum (BR-CC-CA) did not significantly change during starvation, a deficiency in PTTH signal transduction was maintained, which led to very low levels of hemolymph ecdysteroids after the beginning of starvation. However, when starvation began on day 3 of the last larval instar, the major hemolymph ecdysteroid peak, preceding larval-pupal transformation, occurred 1 day earlier than that in control larvae. Protein content of the prothoracic glands in day 3-starved larvae was maintained at a low level as compared to that of control larvae. The secretory activity of the prothoracic glands in day 3-starved larvae was maintained at a level similar to that of control larvae. However, the rate of ecdysteroidogenesis, expressed per microgram of glandular protein, was greatly enhanced in these starved larvae, indicating that upon starvation, larvae increased the ecdysteroid production rate to enhance the rate of survival.

Animals↗
PubMed1985

Cross-phyletic bioactivity of arthropod neurohormones and molluscan ganglion extracts: evidence of an extended peptide family.

Two structurally related arthropod neuropeptides, red pigment concentrating hormone (RPCH) and adipokinetic hormone (AKH), are potent excitors of the heart of the clam Mercenaria mercenaria. The response is bimodal: whereas the threshold for affected hearts is 1-3 X 10(-9) M, about 40% of the preparations are virtually unresponsive. Aqueous extracts of Mercenaria ganglia contain a substance which concentrates the red pigment in the erythrophores of intact destalked Uca pugilator and even of its isolated legs. This substance is retained on Sephadex G-15 and co-elutes with synthetic shrimp RPCH. The active fractions also concentrate the erythrophores and the leucophores of destalked shrimp (Penaeus). Neither dopamine nor the molluscan neuropeptide FMRFamide had any chromatophorotropic effect in these assays. The activity of the ganglion extracts was abolished by digestion with chymotrypsin. In conclusion, molluscan ganglion extracts contain a peptide factor, possibly an analog of RPCH, that concentrates the pigments of crustacean chromatophores by a direct action on the cells.

Animals↗
PubMed1990

Changes in the sensitivity of adult cockroach corpora allata to a brain allatostatin.

There are major changes in the sensitivity of corpora allata from the cockroach Diploptera punctata toward the allatostatic tridecapeptide APSGAQRLYGFGL-amide (ASAL) during the female reproductive cycle, as revealed by measurement of juvenile hormone (JH) biosynthesis in vitro. Glands from recently molted adult females show only 30-40% inhibition at 10 nM ASAL, falling to a minimum of less than 10% on day 5 at the peak of spontaneous JH synthesis in vitro. The decline in JH synthesis observed in post-vitellogenic females is accompanied by a dramatic increase to ca. 90% ASAL sensitivity at 10 nM by day 6. Then sensitivity slowly wanes during subsequent ovulation and pregnancy to the levels typical of previtellogenic and virgin females. Full dose/response studies reveal a second level of response at ca. 1 microM, which resembles the pattern obtained from whole brain extracts. We conclude that physiological sensitivity to ASAL (IC50 ca. 0.1 nM) is correlated with the preparation for choriogenesis, and we suggest that 1000 times higher doses give a cross-reaction with related allatostatic receptor(s) that confer important sensitivity at other development stages.

Amino Acid Sequence↗
PubMed1996

Calcium-dependent action of hypertrehalosemic hormone on activation of glycogen phosphorylase in cockroach fat body.

Signaling mechanisms for Blaberus discoidalis hypertrehalosemic hormone (Bld-HrTH)-dependent glycogen phosphorylase activation were investigated in vitro using fat body of the tropical cockroach, B. discoidalis. Brief treatment of fat bodies with Bld-HrTH in the absence of extracellular Ca2+ showed a significant activation of phosphorylase. Although extracellular Ca2+ was required for a full activation of phosphorylase by Bld-HrTH, stimulation in the absence of extracellular Ca2+ suggested that intracellular Ca2+ was also involved in Bld-HrTH signal transduction. Thapsigargin and thimerosal mobilize Ca2+ from intracellular stores by different mechanisms, and both chemicals stimulated phosphorylase activities as effectively as a maximum dose of Bld-HrTH. Bld-HrTH likely induces intracellular Ca2+ release followed by extracellular Ca2+ entry across the plasma membrane. Inositol-1,4,5-trisphosphate (InsP3) levels were greatly increased by Bld HrTH in a time- and dose-dependent manner, suggesting that InsP3 might be a Ca(2+)-mobilizing intracellular second messenger for Bld-HrTH.

Animals↗
PubMed1996

The Drosophila Eip78C gene is not vital but has a role in regulating chromosome puffs.

We have generated a number of chromosomal aberrations that disrupt the early-late ecdysone-induced 78C puff gene (Eip78C, ecdysone-induced protein, FlyBase name for the E78 gene of Stone and Thummel 1993), which encodes the two members of the nuclear hormone receptor superfamily Eip78C-A and Eip78C-B. The aberrations include deletions of the ligand-binding/dimerization domain of both, inversions that split Eip78C-A but retain residual Eip78C-B expression, and a small deletion specific for Eip78C-B. We find that wild-type Eip78C functions are completely dispensable for normal development under laboratory conditions. However, we show that Eip78C-B is required for the maximal puffing activity of a subset of late puffs (63E and 82F) since these puffs are reduced in size in Eip78C-B mutant backgrounds. Paradoxically the same late puffs are reduced, as well as at least one other, when the Eip78C-B cDNA is overexpressed from a heat shock promoter. These data indicate either that Eip78C function is redundant or that it plays a subtle modulating role in the regulation of chromosome puffing.

Amino Acid Sequence↗
PubMed1989

Synthesis of a homodimer neurohormone precursor of locust adipokinetic hormone studied by in vitro translation and cDNA cloning.

The homodimer neurohormone precursor P1, consisting of 41 residue subunits or A-chains, is synthesized by the glandular neurosecretory cells of the corpora cardiaca (CC) of the locust Schistocerca gregaria. Processing of P1 generates two copies of a 10 amino acid peptide neurohormone (AKH I) and one copy of a homodimer peptide (APRP 1). Here we show that the P1 dimer is formed from two independent A-chain translation products. Translation of CC mRNA in vitro produces a prominent 6.4 kd protein, the synthesis of which can be blocked by oligonucleotides hybridizing to mRNA encoding the A-chain. Northern blot experiments suggest that the 6.4 kd protein is produced by an integral of 500 base mRNA. cDNA cloning reveals a pre-A-chain structure in which a single copy of the A-chain is preceded by a 22 amino acid signal peptide. This evidence indicates that the P1 dimer is synthesized by coupling of very small translational products rather than by folding and processing of a larger protein containing more than one copy of the A-chain.

Amino Acid Sequence↗
PubMed1997

Involvement of juvenile hormone in regulation of prothoracicotropic hormone transduction during the early last larval instar of Bombyx mori.

We previously reported that a deficiency in prothoracicotropic hormone (PTTH) transduction during the early last larval instar of Bombyx mori plays a role in leading to very low ecdysteroid levels in the hemolymph, inactivation of corpora allata, as well as larval-pupal transformation. In the present study, the role of juvenile hormone (JH) in the regulation of PTTH transduction was clarified. When JH analog (hydroprene) was applied to early last instar larvae, the development of larvae was greatly inhibited. It was found that it was not PTTH release, but prothoracic gland competency in both cAMP generation and ecdysteroidogenesis to the stimulation of PTTH which was developmentally inhibited by hydroprene application. Glands in hydroprene-treated larvae showed no response in ecdysteroidogenesis to either PTTH or 1-methyl-3-isobutylxanthine (MIX) until day 7, 4 days later than those of control larvae. JH-I application showed the same effects as those of hydroprene. By contrast, allatectomy on day 0 of the last instar accelerated development, and glands showed the activation response to either PTTH or MIX in both cAMP generation and ecdysteroidogenesis 1 day after allatectomy. From these results, we conclude that the absence of JH is a prerequisite for successful PTTH transduction and for acquisition of the cAMP generating system of gland cells.

Animals↗
PubMed2003

Developmental and diel changes of adipokinetic hormone in CNS and haemolymph of the flightless wing-polymorphic bug, Pyrrhocoris apterus (L.).

We have used an enzyme-linked immunoassay (ELISA) for determination of the AKH content in CNS (brain + corpora cardiaca + corpora allata) and haemolymph of adult macropterous and brachypterous females of the bug Pyrrhocoris apterus. The tests revealed that the AKH content fluctuates between 1 and almost 4 pmol/CNS during the first 14 days of adult life and significantly increased in order diapausing brachypters<reproductive brachypters<macropters. The titre of AKH in haemolymph is detectable mostly only in macropterous females during that period; in reproductive or diapausing brachypterous females keeps mostly below the detectable limit--1 fmol/microl. There are significant changes of AKH content in CNS and haemolymph of 10-day-old macropterous females during a 24 h period, with the highest values at about 10 h after the onset of light and at second half of the light period, respectively. The diel changes of AKH content in CNS are positively correlated with diel changes of adipokinetic response to AKH. Immunohistochemistry revealed that almost all reactive material is localized in the posterior part of the corpora cardiaca, and just a small amount in a few cell groups and axons distributed over the whole brain.

Aging↗
PubMed2003

Regulation of juvenile hormone biosynthesis in Heliothis virescens by Manduca sexta allatotropin.

In Heliothis virescens, reproduction is strictly dependent on juvenile hormone (JH). In females, mating induces a sharp increase in JH titers, which stimulates increased vitellogenin biosynthesis and higher rates of egg production. JH biosynthesis is presumably stimulated by production and/or release of stimulatory neuropeptides such as allatotropins. There is evidence that allatotropin of H. virescens may be structurally related to Manduca sexta allatotropin (Manse-AT). In a radiochemical in vitro assay, synthetic Manse-AT stimulated JH biosynthesis by corpora allata (CA) of virgin H. virescens females in a dose-dependent manner, but had no effect on CA activity in H. virescens males. In females, the CA showed a transient increase in sensitivity to Manse-AT shortly after mating. Several structurally related peptides stimulated CA activity to a similar extent as Manse-AT. Corpora allata activity was stimulated by a Ca2+ ionophore, A23187. A membrane-permeable Ca2+ chelator, BAPTA/AM, antagonized the stimulatory effects of Manse-AT, suggesting that Manse-AT may enhance CA activity by increasing intracellular Ca2+ concentration.

Amino Acid Sequence↗
PubMed1997

Hyperprolinaemia caused by novel members of the adipokinetic hormone/red pigment-concentrating hormone family of peptides isolated from corpora cardiaca of onitine beetles.

Two novel members of the adipokinetic hormone/red pigment-concentrating hormone family of peptides were identified in dung beetles of the genus Onitis using heterologous (measuring lipid and carbohydrate mobilization in locusts and cockroaches) and a homologous (measuring proline increase in the haemolymph) bioassay(s). Isolation of the peptides was achieved by single-step reverse-phase HPLC of corpora cardiaca extracts. The primary structure was elucidated by automated Edman degradation and by electrospray MS. Both peptides are blocked octapeptides containing three aromatic amino acids. Peptide 1, designated Ona-CC-I, is pGlu-Tyr-Asn-Phe-Ser-Thr-Gly-Trp-NH2, and peptide 2, designated Ona-CC-II, is pGlu-Phe-Asn-Tyr-Ser-Pro-Asp-Trp-NH2. The synthetic peptides were chromatographically indistinguishable from the natural compounds. They both had a hyperprolinaemic effect in the dung beetle. Moreover, flight experiments established that proline is an important fuel to power flight metabolism in Onitis species. Therefore, it is concluded that these novel and unique peptides are involved in regulating proline-based flight metabolism.

Amino Acid Sequence↗
PubMed1998

Ecdysteroidostatin from the house fly, Musca domestica.

Ovaries from house flies maintained on sucrose secrete large amounts of ecdysteroid when they are cultured with ovarian ecdysteroidogenic hormone, OEH. However, ovarian ecdysteroid secretion is reduced by incubation with both OEH and the ovarian ecdysteroidostatin (OES). A partially purified OES fraction from a semi-preparative reverse phase HPLC C18 column caused a 98% inhibition of ovarian ecdysteroid secretion in vitro at a concentration of 0.8 equivalents per microliter. Ovaries can be activated to produce ecdysteroid in vivo by feeding diet containing protein to flies maintained on sucrose. Ecdysteroid secretion was inhibited when the in vivo stimulated ovaries were cultured with OES. This suggests that OES does not interfere with the OEH activation mechanism, but blocks ovarian ecdysteroid synthesis or release. Furthermore, OES inhibition is reversible and ecdysteroid secretion resumes when OES is removed. Musca OES could explain the decrease in ecdysteroid levels found in flies after mid-vitellogenesis. Both adult male and female abdomens contain OES, but OES was not transferred to females during mating. Evidence is presented that OES is not a trypsin modulating oostatic factor.

Animals↗
PubMed1982

Pharmacology of insecticide-induced release of hyperlipaemic hormone in the locust, Locusta migratoria.

1. The mechanism of insecticide-induced release of hyperlipaemic hormone from the glandular lobe of the isolated corpora cardiaca (CC) of locusts has been studied using pharmacological agents. 2. Treatment of isolated CC with various insecticides induces the release of hyperlipaemic hormone as judged by bioassay. 3. Reserpinisation of CC (25 micrograms/locust) or treatment of isolated CC with the alpha-adrenergic-receptor blocker phentolamine had no effect on the action of DDT or bioresmethrin, but partially blocked the action of dieldrin and chlorfenvinphos. 4. Treatment of isolated CC with the postsynaptic cholinergic blocker hexamethonium bromide abolished the effect of dieldrin and chlorfenvinphos, but did not block the action of DDT or bioresmethrin. 5. The effects of all the insecticides tested in this study were completely blocked by treatment of the CC with 10(-6) M tetrodotoxin. 6. The results indicate that DDT and bioresmethrin may act directly on the glandular cells via a sodium-dependent mechanism. The results with dieldrin and chlorfenvinphos suggest the presence of two distinct cholinergic pathways, one of which acts via the pre-synaptic aminergic terminals which control the glandular cells, whereas the other acts elsewhere in the CC. Sodium channels are also involved in the ultimate expression of these two insecticides.

Animals↗
PubMed2000

Identification of the cellular target for eclosion hormone in the abdominal transverse nerves of the tobacco hornworm, Manduca sexta.

The isolated abdominal central nervous system of Manduca sexta undergoes an increase in cyclic GMP (cGMP) when exposed to the insect peptide eclosion hormone (EH) before pupal ecdysis. Previously, cGMP immunocytochemistry revealed that the EH-stimulated increase in cGMP was contained in numerous filamentous processes within the transverse nerve associated with each abdominal ganglion. These processes seemed to be the axons of neurosecretory cells projecting to this neurohemal organ. In the present paper, we now show that the EH-stimulated cGMP is not present in neurosecretory terminals. There is no colocalization of the EH-stimulated cGMP with immunoreactivity of two peptides, known to be present in axons in the transverse nerves. Furthermore, there is no colocalization of EH-stimulated cGMP with the synaptic vesicle protein, synaptotagmin. The neurosecretory axons are localized to a narrow band at the anterior margin of the transverse nerve, whereas the cellular elements showing an EH-stimulated cGMP increase are primarily present in the posterior region. There are two cell types in this region: a granular and a nongranular type. The cGMP immunoreactivity seems to be contained within the nongranular type. During adult development, the cells of the posterior compartment spread in a thin layer between the transverse and dorsal nerves, become positive for myosin immunoreactivity between pupal stages 5 and 8, and seem to form the adult ventral diaphragm muscles. We conclude that the EH-sensitive filaments in the transverse nerves of Manduca are most likely to be intrinsic cells that subsequently develop into the ventral diaphragm muscles of the adult.

Abdomen↗
PubMed1997

Isolation and characterization of Melanoplus sanguinipes adipokinetic hormone: a new member of the AKH/RPCH family.

A neuropeptide hormone isolated from corpora cardiaca of Melanoplus sanguinipes was purified by HPLC. The HPLC fractions were examined for adipokinetic activity with an in vivo bioassay. A single large UV absorbent peak was active in the mobilization of lipid while the other HPLC fractions showed no detectable activity. This large peak had a retention time and amino acid composition identical to synthetic Lom-AKH-I which was analyzed in a parallel manner. The primary sequence structure, pGlu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-Gly-Thr-NH2, was determined by automated gas-phase Edman degradation. The peptide was deblocked prior to sequencing using pyroglutamate aminopeptidase and the sequence was confirmed with mass spectrometry. The C-terminus of the peptide was determined to be blocked, as indicated by the lack of digestion with carboxypeptidase A. The knowledge of the primary sequence of Mes-AKH allows the use of a commercially available synthetic peptide and its antibodies for use in future research with Melanoplus sanguinipes.

Animals↗
PubMed1997

Differential induction of inositol phosphate metabolism by three adipokinetic hormones.

Many (in)vertebrates simultaneously release several structurally and functionally related hormones; however, the relevance of this phenomenon is poorly understood. In the locust e.g. each of three adipokinetic hormones (AKHs) is capable of controlling mobilization of carbohydrate and lipid from fat body stores, but it is unclear why three AKHs coexist. We now demonstrate disparities in the signal transduction of these hormones. Massive doses of the AKHs stimulated total inositol phosphate (InsPn) production in the fat body biphasicly, but time courses were different. Inhibition of phospholipase C (PLC) resulted in attenuation of both InsPn synthesis and glycogen phosphorylase activation. The AKHs evoked differential formation of individual [3H]InsPn isomers (InsP(1-6)), the effect being most pronounced for InsP3. 40 nM of AKH-I and -III induced a substantial rise in total InsPn and [3H]InsP3 at short incubations, whereas the AKH-II effect was negligible. At a more physiological dose of 4 nM, the AKHs equally enhanced Ins(1,4,5)P3 levels. The InsP3 effect was most prolonged for AKH-III. These subtle differences in InsPn metabolism, together with earlier findings on differences between the AKHs, support the hypothesis that each AKH exerts specific biological functions in the overall syndrome of energy mobilization during flight.

Animals↗
PubMed1994

Superior expression of juvenile hormone esterase and beta-galactosidase from the basic protein promoter of Autographa californica nuclear polyhedrosis virus compared to the p10 protein and polyhedrin promoters.

The expression characteristics of the p10, polyhedrin and basic protein promoters of Autographa californica nuclear polyhedrosis virus were compared using two reporter enzymes, juvenile hormone esterase (JHE) and beta-galactosidase. In these systems, JHE is exported from the cell and beta-galactosidase is localized to the cytosol. Expression of JHE from the basic, p10 and polyhedrin promoters was first detected in the medium at 13, 19 and 27 h post-infection respectively. The basic protein promoter yielded the highest expression of the three promoters tested for both enzymes, as determined by protein and enzyme activity assays. In addition, yields of beta-galactosidase and JHE under control of the p10 promoter are higher relative to expression under control of the polyhedrin promoter. These data highlight the importance of investigation of viral promoters other than the polyhedrin promoter for high yield protein expression in vitro, and for insecticidal use of recombinant baculoviruses requiring high levels of expression. The results support revision of the current concept that very late viral promoters are always optimal for high yield recombinant protein expression.

Carboxylic Ester Hydrolases↗