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PubMed2005

Is C-26 hydroxylation an evolutionarily conserved steroid inactivation mechanism?

Sterols are essential components of virtually all higher eukaryotic organisms, though the exact identity of the dominating sterol varies between species, from the C-27 of cholesterol in vertebrates to the C-28 and C-29 sterols of plants and invertebrates. In addition to their role as structural components of cell membranes these sterols are also converted into a variety of biologically active hormones. This conversion generally involves modifications of the basic structure of the sterol by dealkylation, hydroxylation and/or isomerization. Recent studies have demonstrated that irreversible inactivation of both plant and insect hormones is achieved by a specific C-26 hydroxylation. The concept of sterol deactivation by 26-hydroxylation appears to be an example of an evolutionarily conserved mechanism that has persisted despite the widely varying requirements for sterols in the species where it has been detected.

Animals↗
PubMed1990

Insulin and Neuroparsin Promote Neurite Outgrowth in Cultured Locust CNS.

Organotypic cultures of locust embryo central nervous system (CNS) were used to study the influence of hormonal factors on neurite outgrowth. Explants from the third thoracic ganglion (embryonic day 9) were grown in a serum-free medium and exposed to insulin, neuroparsin, a recently characterized insect neurohormone, somatostatin and two insect hormones: 20-hydroxyecdysone and juvenile hormone. These hormonal factors were tested either alone or in several combinations. In our culture system both insulin and neuroparsin promoted extensive neurite outgrowth. Their effects were quantitatively similar. Somatostatin had no effect on neurite formation, but was a growth factor for glial cells. 20-hydroxyecdysone was a required factor for glial cell and neurite survival. Juvenile hormone did not have any observable effects in this culture system. When insulin was added in combination with 20-hydroxyecdysone the stimulation of neurite outgrowth exceeded that seen when insulin was added alone. A similar enhancement was observed with the combination of neuroparsin and 20-hydroxyecdysone. We conclude that in locusts: (i) insulin can be implicated as a neurotrophic factor as in vertebrates; and (ii) neuroparsin, a locust neurohormone, can also be characterized as a neurotrophic factor for the locust. Moreover, both neurohormones interact synergistically with the steroid hormone 20-hydroxyecdysone to enhance neurite growth.

Journal Article↗
PubMed1997

Allatostatin in hemocytes of the cockroach Diploptera punctata.

Allatostatins are neuropeptides that inhibit the production, by the corpora allata, of a major insect hormone, juvenile hormone. These peptides are produced by cells of the brain and ganglia as well as by midgut endocrine cells. Transport from these sites may contribute to the allatostatin content in the hemolymph (insect blood). Using a monoclonal antibody against Diploptera punctata allatostatin I (A-P-S-G-A-Q-R-L-Y-G-F-G-L-NH2) and in situ hybridization with a digoxigenin-labeled cRNA probe generated from a portion of the allatostatin gene, it is demonstrated that allatostatin is present in and synthesized by granular hemocytes of D. punctata. About 5% of the hemocytes react with anti-allatostatin antibody and a similar number hybridize with a cRNA probe that detects allatostatin-specific mRNA. Electron micrographs showed that allatostatin-immunoreactive material occurs in membrane-bound, uniformly dense granules that frequently fill fusiform-shaped cells. Allatostatin in cell and plasma fractions of hemolymph quantified by enzyme-linked immunosorbent assay and by bioassay for inhibition of juvenile hormone synthesis in vitro indicated that about equal quantities (0.1-0.2 fmol/microl) are present in cell and plasma fractions. The production of allatostatin by hemocytes suggests that allatostatins may function as regulatory peptides in hemolymph activities in addition to their other known functions.

Animals↗
PubMed1994

Isolation and partial characterization of a gene from trachea of Manduca sexta that requires and is negatively regulated by ecdysteroids.

The molting cycle in insects is regulated by the fluctuating levels of ecdysteroids. Twenty-four hours prior to the pupal molt in Manduca sexta steroid titers are relatively high and they fall to very low levels at 4 hr before the molt. Several physiological events accompanying molts have been shown to require the rise and then the subsequent decline of ecdysteroid levels. These events also require the expression of a new set of genes. We used subtractive hybridization to isolate genes that are expressed 4 hr, but not 24 hr, prior to the pupal molt in the nervous system of Manduca. These genes are expected to play a role either in ecdysis behavior or in the development of pupal/adult structures. The first such gene we have identified, esr20 (EcdySteroid Regulated) encodes a 20-kDa protein. The deduced amino acid sequence of the protein shows similarity to acidic domains in three urelated proteins, chick nucleolin, rat heavy-molecular-weight neurofilament, and the Drosophila steroid orphan receptor, knirps-related. The similarity among the four proteins appears to be in regions implicated in protein-protein interactions. The accumulation of esr20 mRNA starts 16 hr prior to the pupal molt and abruptly stops at ecdysis. Expression of esr20 was localized to tracheal epithelial cells within all tissue types, and the transcript was present prior to the larval, pupal, and adult molts only after the molting peak of ecdysteroids had declined. Its expression was inhibited in the presence of ecdysteroids in vitro and required protein synthesis.

Amino Acid Sequence↗
PubMed1992

Over-expression and characterization of recombinant beta subunit of the human chorionic gonadotropin hormone synthesized in insect cells infected with a genetically engineered baculovirus.

A recombinant baculovirus, vAc beta hCG, having a replacement of the viral polyhedrin gene with the cDNA encoding the beta subunit of hCG was used to express beta hCG, an extensively glycosylated hormone, in insect cells. Virus-infected cells, 72 hr pi, secreted approximately 8.02 micrograms beta hCG/2 x 10(6) cells/ml. The recombinant beta hCG purified from insect cells exhibited increased mobility on SDS-PAGE as compared to authentic urinary beta hCG, a reflection on differences in glycosylation between insect and mammalian systems. The insect derived beta hCG, however, was identical to the native hormonal peptide in terms of immunoreactivity and bioactivity on association with alpha-subunit, as evident by its binding to rat testicular receptors and induction of steroidogenesis in a mouse Leydig cell bioassay system. The implications of using the baculovirus system to study the importance of carbohydrates for biological activity are also discussed.

Animals↗
PubMed2006

Cloning and characterization of a third isoform of corazonin in the honey bee Apis mellifera.

The precursor of the insect hormone corazonin has been cloned from the honey bee Apis mellifera. The precursor predicts a novel isoform of corazonin, pQTFTYSHGWTNamide, which was confirmed by tandem mass spectrometry. Although Apis corazonin differs only by a glutamine/threonine substitution from [His7]-corazonin, it is considerably less active in the dark color inducing assay on albino locusts. Whole mount fluorescence immunohistochemistry of the central nervous system of the honey bee showed a pattern similar to the ones described for other insects. Four neurons of the lateral protocerebrum project axons towards the retrocerebral complex. It is unlikely that Apis corazonin is present in all hymenopteran species since the presence of this peptide could not be demonstrated by means of mass spectrometry in the retrocerebral complex of the red wood ant Formica rufa and the wasp Vespula saxonica. Instead, we found masses corresponding with [Arg7]- and [His7]-corazonin respectively, suggesting that some of the corazonin isoforms originated late during evolution in different insect orders.

Amino Acid Sequence↗
PubMed2005

Regulation of JH epoxide hydrolase versus JH esterase activity in the cabbage looper, Trichoplusia ni, by juvenile hormone and xenobiotics.

JH III esterase and JH III epoxide hydrolase (EH) in vitro activity was compared in whole body Trichoplusia ni homogenates at each stage of development (egg, larva, pupa and adult). While activity of both enzymes was detected at all ages tested, JH esterase was significantly higher than EH activity except for day three of the fifth (last) stadium (L5D3). For both enzymes, activity was highest in eggs. Adult virgin females had 4.6- and 4.0-fold higher JH esterase and EH activities, respectively, than adult virgin males. JH III metabolic activity also was measured in whole body homogenates of fifth stadium T. ni that were fed a nutritive diet (control) or starved on a non-nutritive diet of alphacel, agar and water. With larvae that were starved for 6, 28 and 52 h, EH activity per insect equivalent was 48%, 5% and 1%, respectively, of the control insects. At the same time points, JH esterase activity levels in starved T. ni were 29%, 4% and 3% of that of insects fed the nutritive diet. Selected insect hormones and xenobiotics were administered topically or orally to fifth stadium larvae for up to 52 h, and the effects on whole body EH and JH esterase activity analyzed. JH III increased the JH III esterase activity as high as 2.2-fold, but not the JH III EH activity. The JH analog, methoprene, increased both JH esterase and EH activity as high as 2.5-fold. The JH esterase inhibitor, 3-octylthio-1,1,1-trifluoropropan-2-one (OTFP), had no impact on EH activity. The epoxides trans- and cis-stilbene oxide (TSO and CSO) in separate experiments increased the EH activity approximately 2.0-fold. TSO did not alter JH esterase levels when topically applied, but oral administration reduced activity to 70% of the control at 28 h, and then increased the activity 1.8-fold at 52 h after the beginning of treatment. CSO had no effect on JH esterase activity. Phenobarbital increased EH activity by 1.9-fold, but did not change JH esterase levels. Clofibrate and cholesterol 5alpha,6alpha-epoxide had no effect on EH. JH esterase activity also was not affected by clofibrate, but cholesterol 5alpha,6alpha-epoxide reduced the JH esterase activity to 60-80% of the control. The biological significance of these results is discussed.

Animals↗
PubMed1990

Cloning and sequencing of a cDNA for the hemolymph juvenile hormone binding protein of larval Manduca sexta.

A cDNA for the hemolymph juvenile hormone binding protein (JHBP) of larval Manduca sexta has been cloned and sequenced. The JHBP was purified to homogeneity from fifth instar larval hemolymph using gel filtration chromatography, ion exchange chromatography, and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Polyclonal rabbit antibodies, generated in response to this protein, were used to identify and isolate JHBP cDNAs from a fat body expression library in bacteriophage lambda ZAPII. Eleven putative JHBP cDNA clones were isolated and subcloned into Bluescript plasmid; cDNA inserts were approximately 750 base pairs in length. A 36-kDa immunoreactive protein was expressed from these plasmids; this beta-galactosidase fusion protein, like the authentic 32-kDa JHBP, was specifically photoaffinity labeled with [3H] epoxyhomofarnesyl diazoacetate (EHDA). Single-stranded DNA from one clone was sequenced by the Sanger dideoxynucleotide method, using deletion and custom primer techniques. A mature translation product was identified which had 226 amino acid residues, a molecular mass of 25,111 daltons, and a predicted isoelectric point (pI) of 5.40. The cDNA correctly predicts the N-terminal amino acid sequence and the amino acid composition of an authentic M. sexta hemolymph JHBP. A computer search of protein and nucleic acid data bases failed to reveal any related sequences. Thus, M. sexta hemolymph JHBP appears to be the first member of a new superfamily of insect hormone binding proteins.

Affinity Labels↗
PubMed2005

A role for betaFTZ-F1 in regulating ecdysteroid titers during post-embryonic development in Drosophila melanogaster.

Variations in ecdysteroid titers play crucial roles in arthropods by initiating and regulating molting and metamorphosis. The recent identification of genes coding for cytochrome P450 enzymes involved in Drosophila ecdysteroidogenesis provides new molecular tools to investigate the regulation of insect hormone production. In the present study, we used an enzyme immunoassay to show that the molting hormone titer is strictly correlated with the steroidogenic capacity of the ring gland. A temporal correlation between dynamics of ecdysone production and expression of genes encoding steroidogenic enzymes was observed during the third instar, suggesting that the timing of hormone production depends on transcriptional regulation of the biosynthetic enzymes. Using clonal analysis, levels of two steroidogenic enzymes, Phantom (PHM) and Disembodied (DIB), were shown to be very reduced in ftz transcription factor 1 (ftz-f1) mutant ring gland cells whereas there was no effect of the without children (woc) mutation, suggesting that FTZ-F1 regulates phm and dib expression. Since betaFTZ-F1 is the homolog of the vertebrate steroidogenic factor 1 (SF1), which plays a key role in the differentiation of vertebrate steroidogenic organs through transcriptional regulation of steroidogenic enzymes, this study emphasizes the strong parallels between insects and vertebrates with respect to the regulatory mechanisms of steroidogenesis.

Animals↗
PubMed1982

Hormonal and genetic regulation of vitellogenesis in Drosophila.

Morphological, genetic, and hormonal studies of the process of vitellogenesis, whereby yolk is accumulated in the developing oocytes, have been going on for many years in Drosophila. Recently there has been a resurgence of interest in vitellogenesis, for it provides a model system for investigating how eukaryotic genes are regulated. The proteins found in the yolk are regulated in a tissue-specific, stage-specific and sex-limited fashion. Molecular studies have identified the major proteins concerned and their genes have been cloned. This has facilitated a new approach to how this fascinating process is controlled. In this review current understanding of the factors required for normal vitellogenesis in Drosophila is analyzed. The nature of the proteins themselves, their sites of synthesis, and the organization and characterization of the genes and transcripts that code for them are emphasized. The manner in which the expression of these genes is regulated by the insect hormones, ecdysone and juvenile hormone, is described and, finally, an analysis is made of how various mutants that disrupt vitellogenesis can contribute further to our understanding of vitellogenesis regulation in Drosophila.

Adipose Tissue↗
PubMed1991

The alpha subunit of human chorionic gonadotropin hormone synthesized in insect cells using a baculovirus vector is biologically active.

A recombinant baculovirus, vAc alpha hCG, having a replacement of the viral polyhedrin gene with the cDNA encoding the alpha subunit of hCG was used to express alpha hCG, an extensively glycosylated hormone, in insect cells. Virus-infected cells, 72 h pi, secreted approximately 11.3 micrograms alpha hCG/2 x 10(6) cells/ml which was identical to the native hormonal peptide in terms of electrophoretic mobility, immunoreactivity and bioactivity on association with beta subunit, as evident by its binding to rat testicular cells and induction of steroidogenesis in a mouse Leydig cell bioassay system. The alpha hCG secreted into the medium represented approximately 20-30% of the total hCG synthesized by vAc alpha CG infected insect cells. The implications of using a very late promoter, in a baculovirus expression system, for directing the transcription of a gene whose gene product requires extensive post-translational modifications are discussed.

Animals↗
PubMed1992

A putative new juvenile peptide hormone in lepidopteran insects.

A growth-blocking peptide (GBP) with repressive activity against juvenile hormone (JH) esterase has been isolated from the last (6th) instar larval plasma of the armyworm Pseudaletia separata (Lepidoptera: Noctuidae) parasitized by the parasitoid wasp Apanteles kariyai (Hymenoptera: Braconidae) (1,2). This study demonstrates that GBP not only exists in the plasma of parasitized last instar larvae, but also in the plasma of unparasitized penultimate (5th) instar larvae, while the plasma of last instar larvae does not contain any detectable amount of GBP. The detection of GBP in unparasitized penultimate instar larvae, before the final larval molt, demonstrates that this factor is naturally occurring in the insect larva before the last larval instar and is seemingly coordinating, along with JH, the regulation of juvenile characteristics. This finding suggests the existence of a new type of juvenile peptide hormone in lepidopteran insects.

Amino Acid Sequence↗
PubMed1997

Maxadilan, the vasodilator from sand flies, is a specific pituitary adenylate cyclase activating peptide type I receptor agonist.

Maxadilan is a potent vasodilator peptide isolated from salivary gland lysates of the sand fly Lutzomyia longipalpis, a vector of leishmaniasis. The peptide aids the fly in obtaining blood from the skin of its vertebrate hosts but the mammalian receptor through which this insect ligand acts was unknown. We demonstrate that maxadilan is an agonist of the type I receptor for pituitary adenylate cyclase activating peptide, a neuropeptide with vascular activity. This surprising observation is a unique example of convergent evolution from a functional standpoint as these two peptides do not share significant sequence homology.

Adenylyl Cyclases↗
PubMed2002

Ecdysteroid-dependent expression of a novel cuticle protein gene BMCPG1 in the silkworm, Bombyx mori.

When insects molt, the exoskeleton is renewed under the controls of insect hormones via the biosynthesis and degradation of cuticle proteins. To understand the hormonal control of cuticle formation, we used the differential display method to look for stage-specific cuticle genes, and identified a novel cDNA named Bombyx mori Cuticle Protein GlyGlyTyr-repeat 1 (BMCPG1). Expression of BMCPG1 mRNA peaked sharply immediately after a pulse of ecdysteroid during the fourth molt and pre-pupal stages, concurrent with the expression of genes for FTZF1 and dopa decarboxylase. BMCPG1 was expressed only in the epidermis, but not in any other tissue. We cultured the larval epidermis and found that BMCPG1 expression is not induced by the continuous presence of ecdysteroid. Removal of ecdysteroid from the medium, which constitutes a pulse treatment, is required for the induction of BMCPG1 transcription. These results explain well the stage-specific expression of BMCPG1 by ecdysteroid in vivo. Based on its expression patterns and unique structure, we propose that BMCPG1 may be a novel component of epicuticle of B. mori, and is probably involved in cross-linking of proteins via its GGY repeats.

Amino Acid Sequence↗
PubMed2002

Analyzing the repressive function of ultraspiracle, the Drosophila RXR, in Drosophila eye development.

Response to the insect hormone ecdysone is mediated by a nuclear receptor complex containing Ultraspiracle (USP) and the Ecdysone Receptor (EcR). Among other phenotypes, loss of functional USP in Drosophila eye development results in an accelerated morphogenetic furrow, although loss of ecdysone arrests the furrow. We have shown that USP both represses and activates a gene affecting furrow movement, the ecdysone-responsive Z1 isoform of Broad-Complex, and we report additional usp mutant phenotypes. Using targeted replacement of USP to rescue usp mutant clones in the eye, we have mapped various USP functions and tested whether the USP nuclear receptor has an activating as well as a repressive effect on furrow movement. Furrow movement and related phenotypes are rescued by the presence of USP in a limited domain near the furrow while other phenotypes are rescued by USP expression posterior to the furrow. Our data indicate roles for USP activity at multiple developmental stages and help explain why loss of functional USP leads to furrow advancement while loss of ecdysone stops furrow movement.

Animals↗
PubMed1996

Structural characterization and location of disulphide linkages of a potent vasodilatory peptide, recombinant maxadilan, by a multiple mass spectrometric approach.

A multiple mass spectrometric strategy using fast-atom bombardment (FAB) and matrix-assisted laser desorption/ionization (MALDI) has been used to confirm the sequence and to locate the disulfide linkages of recombinant maxadilan (r-maxadilan) (average molecular mass 7422.5 Da), a potent vasodilatory peptide from Lutzomyia longipalpis. MALDI measurements of intact r-maxadilan, its reduced form and its pyridylethylated form (p-maxadilan) indicated the presence of four Cys residues without major post-translational modifications. FAB and FAB-tandem mass spectrometry measurements of chymotryptic digests of p-maxadilan were sufficient to map the primary structure of p-maxadilan, though the complementary use of MALDI was necessary for complete mapping using Asp-N digestion due to a strong suppression observed in FAB. Assignment of the Cys-5-Cys-9 linkage was achieved by comparison of FAB mass spectra before and after reduction of tryptic digests of r-maxadilan. Since the molecular weight of the peptide fragment containing the Cys-18-Cys 55 linkage is more than 4000, MALDI measurement was indispensable for assignment of this linkage. The results fully support the value of the multiple mass spectrometric strategy in the structural characterization of peptides and proteins.

Amino Acid Sequence↗
PubMed1996

CD and NMR structural characterization of ceratotoxins, natural peptides with antimicrobial activity.

Antibacterial properties of the secretion from the female reproductive accessory glands of medfly Ceratitis capitata are mostly ascribed to the presence of two peptides, ceratotoxin A and B, which exhibit a strong activity against gram-positive and gram-negative bacterial strains, and show sequence and function homology with cecropins, melittin, and magainins. CD experiments performed in different solvents indicate the presence of a significant content of helical structures in organic solvent. Two-dimensional nmr results for ceratotoxin A in methanol show a helical behavior for the 8-25 region of the peptide. A ramachandran classification of each residue for the structures obtained from distance geometry calculations lead to the definition of four structural families in which the central segment 10-19 is always helical and differences refer to residues 8-9 and 19-23. A sequence analysis of the two ceratotoxins and a systematic search on the protein data bank revealed the occurrence of a KX-hydrophobic-hydrophobic-P motif that seems to be important for helix stabilization.

Amino Acid Sequence↗