Extending the honey bee venome with the antimicrobial peptide apidaecin and a protein resembling wasp antigen 5

Honey bee venom is a complex mixture of toxic proteins and peptides. In the present study we tried to extend our knowledge of the venom composition using two different approaches. First, worker venom was analysed by liquid chromatography-mass spectrometry and this revealed the antimicrobial peptide apidaecin for the first time in such samples. Its expression in the venom gland was confirmed by reverse transcription PCR and by a peptidomic analysis of the venom apparatus tissue. Second, genome mining revealed a list of proteins with resemblance to known insect allergens or venom toxins, one of which showed homology to proteins of the antigen 5 (Ag5)/Sol i 3 cluster. It was demonstrated that the honey bee Ag5-like gene is expressed by venom gland tissue of winter bees but not of summer bees. Besides this seasonal variation, it shows an interesting spatial expression pattern with additional production in the hypopharyngeal glands, the brains and the midgut. Finally, our immunoblot study revealed that both synthetic apidaecin and the Ag5-like recombinant from bacteria evoke no humoral activity in beekeepers. Also, no IgG4-based cross-reactivity was detected between the honey bee Ag5-like protein and its yellow jacket paralogue Ves v 5.

A proteomic approach to neuropeptide function elucidation

Many of the diverse functions of neuropeptides are still elusive. As they are ideally suited to modulate traditional signaling, their added actions are not always detectable under standard laboratory conditions. The search for function assignment to peptide encoding genes can therefore greatly benefit from molecular information. Specific molecular changes resulting from neuropeptide signaling may direct researchers to yet unknown processes or conditions, for which studying these signaling systems may eventually lead to phenotypic confirmation. Here, we applied gel-based proteomics after pdf-1 neuropeptide gene knockout in the model organism Caenorhabditis elegans. It has previously been described that pdf-1 null mutants display a locomotion defect, being slower and making more turns and reversals than wild type worms. The vertebrate functional homolog of PDF-1, vasocative intestinal peptide (VIP), is known to influence a plethora of processes, which have so far not been investigated for pdf-1. Because proteins represent the actual effectors inside an organism, proteomic analysis can guide our view to novel pdf-1 actions in the nematode worm. Our data show that knocking out pdf-1 results in alteration of levels of proteins involved in fat metabolism, stress resistance and development. This indicates a possible conservation of VIP-like actions for pdf-1 in C. elegans.

A structural and functional comparison of nematode and crustacean PDH-like sequences

The elucidation of the whole genome of the nematode Caenorhabditis elegans allowed for the identification of ortholog genes belonging to the pigment dispersing hormone/factor (PDH/PDF) peptide family. Members of this peptide family are known from crustaceans, insects and nematodes and seem to exist exclusively in ecdysozoans where they play a role in different processes, ranging from the dispersion of integumental and eye (retinal) pigments in decapod crustaceans to circadian rhythms in insects and locomotion in C. elegans. Two pdf genes (pdf-1 and pdf-2) encoding three different peptides: PDF-1a, PDF-1b and PDF-2 have been identified in C. elegans. These three C. elegans PDH-like peptides are similar but not identical in primary structure to PDHs from decapod crustaceans. We investigate whether this divergence has an influence on the pigment dispersing function of the peptides in a decapod crustacean, namely the shrimp Palaemon pacificus. We show that C. elegans PDF-1a and b peptides display cross-functional activity by dispersing pigments in the epithelium of P. pacificus at physiological doses. Moreover, by means of a comparative amino acid sequence analysis of nematode and crustacean PDH-like peptides, we can pinpoint several potentially important residues for eliciting pigment dispersing activity in decapod crustaceans. Although there is no sequence information on a receptor for PDH in decapod crustaceans, we postulate that there is general conservation of the PDH/PDF signaling system based on structural similarities of precursor proteins and receptors (including those from a branchiopod crustacean and from C. elegans).

Signalling through pigment dispersing hormone-like peptides in invertebrates

During recent decades, several research teams engaged in unraveling the molecular structure and the physiological significance of pigment dispersing hormone-like peptides, particularly with respect to colour change and biological rhythms. In this review, we first summarise the entire history of pigment dispersing hormone-like peptide research, thus providing a stepping stone for those who are curious about this growing area of interest. Next, we try to bring order in the plethora of experimental data on the molecular structure of the various peptides and receptors and also discuss immunolocalization, time-related expression and suggested functions in crustaceans, insects and nematodes. In addition, a brief comparison with the vertebrate system is made.

Characterization of an RFamide-related peptide orphan GPCR in C. elegans

We cloned and characterized an orphan FMRFamide-related peptide (FaRP) GPCR in Caenorhabditis elegans. We synthesized numerous structurally different FaRPs that were found in the C. elegans genome by bioinformatic analysis and used them to screen cells expressing the C26F1.6 receptor. Two peptides ending in M(orL)VRFamide elicited a calcium response in receptor-expressing mammalian Chinese hamster ovary cells. The response was dose-dependent and appeared to be very specific; that is, none of the other FaRPs were active, not even closely related peptides also ending in M(orL)VRFamide, which are encoded by the same peptide precursor. Pharmacological profiling with a truncated series of the most active peptide revealed that the full peptide sequence is necessary for receptor activation.

Bioinformatic analysis of peptide precursor proteins

Neuropeptides are among the most important signal molecules in animals. Traditional identification of peptide hormones through peptide purification is a tedious and time-consuming process. With the advent of the genome sequencing projects, putative peptide precursor can be mined from the genome. However, because bioactive peptides are usually quite short in length and because the active core of a peptide is often limited to only a few amino acids, using the BLAST search engine to identify neuropeptide precursors in the genome is difficult and sometimes impossible. To overcome these shortcomings, we subject the entire set of all known Drosophila melanogaster peptide precursor sequences to motif-finding algorithms in search of a motif that is common for all prepropeptides and that could be used in the search for new peptide precursors.

Melatonin-induced neuropeptide release from isolated locust corpora cardiaca

A method, based on a combination of mass spectrometry and liquid chromatography, was developed to investigate the release of neuropeptides from isolated locust corpora cardiaca. Melatonin, octopamine, trehalose and forskolin were administered to the perifused glands. The neuropeptides present in the releasates (spontaneous versus induced) were visualized by either conventional or capillary HPLC. Identification was achieved by means of MALDI-TOF MS and/or nanoflow-LC-Q-TOF MS. The observed effects of these chemicals regarding AKH release were in line with previous studies and validate the method. The most important finding of this study was that administration of melatonin stimulated the release of adipokinetic hormone precursor related peptides (APRP 1 and APRP 2), neuroparsins (NP A1, NP A2 and NP B) and diuretic peptide.

Peptidomics of the locust corpora allata: identification of novel pyrokinins (-FXPRLamides)

The peptidomes of the corpora allata of Locusta migratoria and Schistocerca gregaria were investigated by both matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and nanoscale liquid chromatography quadrupole time-of-flight tandem mass spectrometry (nanoLC-Q-TOF MSMS). The pyrokinin (-FXPRLamide) family seems to be predominant. In addition to the known pyrokinins, we de novo sequenced four pyrokinins in L. migratoria and five in S. gregaria. In addition, one pyrokinin-like peptide (-PRLamide) was identified in S. gregaria. Besides the -(FX)PRLamides, FLRFamide-1, the allatostatins (A family) and numerous as yet unidentified peptides are also present in the corpora allata.

Peptide profiling of a single Locusta migratoria corpus cardiacum by nano-LC tandem mass spectrometry

The pars intercerebralis-corpora cardiaca complex in insects is the functional equivalent of the vertebrate brain-pituitary axis. During the past few decades more than 40 neuropeptides have been isolated from the locust brain-corpus cardiacum complex. Tedious and time-consuming successive purification rounds of large tissue extracts were necessary to achieve the purification and sequencing of most of these signal molecules. Nowadays, the combination of nanoscale liquid chromatography and the very sensitive tandem mass spectrometry allows us to identify and sequence peptides in very low concentration directly from tissue extracts. In this manuscript, we review previous data on the peptidome analysis of the locust corpora cardiaca, with emphasis on AKH processing. In addition, we report the peptide profiling of a single corpus cardiacum from Locusta migratoria. 23 peptides were isolated and sequenced in a single nano-LC-MS/MS experiment, demonstrating the sensitivity and effectiveness of mass spectrometry in peptide research.

Antimicrobial compounds of low molecular mass are constitutively present in insects: characterisation of beta-alanyl-tyrosine

The number of bacterial and fungal strains that have developed resistance against the classical antibiotics continues to grow. The intensified search for new antibiotic lead compounds has resulted in the discovery of numerous endogenous peptides with antimicrobial properties in plants, bacteria and animals. Their possible applications as anti-infective agents are often limited by their size, in reference to production costs and susceptibility to proteases. In this article, we report recent isolations of antimicrobial compounds from insects, with molecular masses less than 1 kDa. Experimental approaches are discussed and the first data on the antimicrobial properties of beta-alanyl-tyrosine (252 Da), one of such low molecular mass compounds isolated from the fleshfly Neobellieria bullata, are presented. We also offer evidence for the constitutive presence of antimicrobial compounds in insects of different orders, in addition to the previously identified inducible antimicrobial peptides.

Isolation, identification, and synthesis of a disulfated sulfakinin from the central nervous system of an arthropods the white shrimp Litopenaeus vannamei

Two myotropic peptides displaying tyrosyl sulfation have been isolated from an extract of central nervous systems (brain, suboesophageal ganglion, thoracic ganglia, and ventral nerve cord) of the white shrimp Litopenaeus vannamei. Both peptides were identified by mass spectrometry and belong to the sulfakinin family of neuropeptides, which are characterized by the C-terminal hexapeptide Y(SO(3)H)GHMRF-NH(2) preceded by two acidic amino acid residues. Pev-SK 1 (AGGSGGVGGEY(SO(3)H)DDY(SO(3)H)GH(L/I) RF-NH(2)) has two sulfated tyrosyl residues and a unique (L/I) for M substitution in the C-terminal sequence. Pev-SK 2 (pQFDEY(SO(3)H)GHMRF-NH(2)) fully complies with the typical sulfakinin core sequence and is blocked by a pyroglutamyl residue. Synthetic analogs (sulfated and unsulfated) were synthesized and the tyrosyl sulfations were confirmed by myotropic activity studies and co-elution with the native fractions. Pev-SK 1 is the first disulfated neuropeptide elucidated in the phylum of the arthropoda, with the only other reported disulfated neuropeptide, called cionin, found in a protochordate. The similarities in amino acid sequence and posttranslational modifications of the crustacean sulfakinins and protochordate cionin provide further evidence for the hypothesis stating that gastrin/CCK, cionin, and sulfakinins originate from a common ancestral gastrin/CCK-like peptide.

Search for peptidic molecular markers in hemolymph of crowd-(gregarious) and isolated-reared (solitary) desert locusts, Schistocerca gregaria

An HPLC analysis of hemolymph extracts was undertaken to uncover differences between desert locusts, Schistocerca gregaria, reared under either crowded or isolated conditions. Some differences in the chromatographic pattern could be detected. One of the major peaks in the hemolymph of crowd-reared adults was found to be a minor one in isolated-reared individuals, whereas other peaks increased after solitarization. The differences became even more pronounced after several generations of isolated rearing. The dominant chromatographic peak in hemolymph extracts of the crowd-reared animals was identified as a novel peptide with a molecular mass of 6080Da. Edman degradation in combination with enzymatic fragmentation and quadrupole-time of flight (Q-Tof) mass spectrometry revealed the full sequence: DNADEDTICVAADNKFYLYANSLKLYTCYNQLPKVYVVKPKSQCRSSLSDCPTS. This 54 aa-peptide is very abundant in hemolymph of crowd-reared adults. Its concentration in hemolymph amounts to 0.1mM. To uncover the function, its effects were investigated in several bioassays, so far without positive results. One of the other peaks differentially expressed in the individuals of the two phases was identified as SGPI-2 (MW=3794Da), which is a serine protease inhibitor in locusts.

Immunocytochemical localization of a diuretic hormone of the beetle Tenebrio molitor, Tenmo-DH(37), in nervous system and midgut

Although the mealworm Tenebrio molitor inhabits very dry environments, it has at least two diuretic peptides, which increase fluid secretion by the free portions of the Malpighian tubules. Unlike other insect corticotropin-releasing factor (CRF)-related peptides isolated to date, these are non-amidated peptides. The immunocytochemical localization of Tenmo-DH(37) was investigated using antisera raised against this hormone. Immunoreactive neurosecretory cells were found in the brain and abdominal ganglia with immunoreactive processes projecting to the peripheral nervous system. Intense staining of the neurohaemal release site, the corpora cardiaca, was observed. In addition, neurosecretory cells immunoreactive to Tenmo-DH(37) were found in the posterior midgut and a network of immunoreactive nerve processes extended over the surface of the midgut. Tenmo-DH(37) is widely distributed and its staining pattern resembles that found for other, amidated CRF-related diuretic peptides.

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.

Effect of Bacillus thuringiensis Cry1 toxins in insect hemolymph and their neurotoxicity in brain cells of Lymantria dispar

Little information is available on the systemic effects of Bacillus thuringiensis toxins in the hemocoel of insects. In order to test whether B. thuringiensis-activated toxins elicit a toxic response in the hemocoel, we measured the effect of intrahemocoelic injections of several Cry1 toxins on the food intake, growth, and survival of Lymantria dispar (Lepidoptera) and Neobellieria bullata (Diptera) larvae. Injection of Cry1C was highly toxic to the Lymantria larvae and resulted in the complete inhibition of food intake, growth arrest, and death in a dose-dependent manner. Cry1Aa and Cry1Ab (5 microg/0.2 g [fresh weight] [g fresh wt]) also affected growth and food intake but were less toxic than Cry1C (0.5 microg/0.2 g fresh wt). Cry1E and Cry1Ac (5 microg/0.2 g fresh wt) had no toxic effect upon injection. Cry1C was also highly toxic to N. bullata larvae upon injection. Injection of 5 microg/0.2 g fresh wt resulted in rapid paralysis, followed by hemocytic melanization and death. Lower concentrations delayed pupariation or gave rise to malformation of the puparium. Finally, Cry1C was toxic to brain cells of Lymantria in vitro. The addition of Cry1C (20 microg/ml) to primary cultures of Lymantria brain cells resulted in rapid lysis of the cultured neurons.

The angiotensin system elements in invertebrates

In this review, the different components of the renin-angiotensin system (RAS) in invertebrates are discussed. This system is implicated in osmoregulation, reproduction, memory processes and immune system regulation. As the elements of this hormone-enzymatic system also exist in invertebrates, it appears that the RAS originated very early in evolution.

Testis ecdysiotropin, an insect gonadotropin that induces synthesis of ecdysteroid

Testes of lepidoptera synthesized ecdysteroid in a somewhat different temporal pattern than the prothoracic glands that release ecdysteroid to the hemolymph. Brain extracts from Heliothis virescens and Lymantria dispar induced testes to synthesize ecdysteroid, but did not affect prothoracic glands. The testis ecdysiotropin (LTE) was isolated from L. dispar pupal brains by a series of high-pressure chromatography steps. Its sequence was Ile-Ser-Asp-Phe-Asp-Glu-Tyr-Glu-Pro-Leu-Asn-Asp-Ala-Asp-Asn-Asn-Glu-Val-Leu-Asp-Phe-OH, of molecular mass 2,473 Daltons. The predominant signaling pathway for LTE was via G(i) protein, IP3, diacylglycerol and PKC; a modulating pathway, apparently mediated by an angiotensin II-like peptide, was controlled via G(s) protein, cAMP, and PKA. Testis ecdysteroid caused isolated testis sheaths to also synthesize a growth factor that induced development of the male genital tract. The growth factor appeared to be a glycoprotein similar to vertebrate alpha-1-glycoprotein. A polyclonal antibody to LTE indicated LTE-like peptide in L. dispar brain medial neurosecretory cells, the suboesophageal, and other ganglia, and also in its target organ, the testis sheath. LTE immunoreactivity was also seen in testis sheaths of Rhodnius prolixus. LTE-like immunoactivity was also detected in developing optic lobes, antennae, frontal ganglia, and elongating spermatids of developing L. dispar pupae. This may indicate that LTE has a role in development as well as stimulation of testis ecdysteroid synthesis. Published 2001 Wiley-Liss, Inc.

Mass spectrometric evidence for the deficiency in the dark-color-inducing hormone,

A factor present in the brain and corpus cardiacum responsible for the induction of dark colour in Locusta migratoria was recently isolated and identified from the corpora cardiaca of normally pigmented locusts. The purification of this factor, designated as [His7]-corazonin was monitored using an albino mutant from a laboratory colony of an Okinawa (Japan) strain. In this study, we provide unequivocal mass spectrometric evidence that the brain and the corpora cardiaca of this albino Locusta mutant are deficient in [His7]-corazonin. Previously, [His7]-corazonin was shown to be responsible for the induction of dark body colour patterns as observed in crowded locusts. Using nanoflow-liquid chromatography-mass spectrometry, we demonstrated that this dark colour-inducing hormone is, however, present in the corpora cardiaca of solitary locusts (Schistocerca gregaria). Arch.

Gonadotropins in insects: an overview

Control of gonad development in insects requires juvenile hormone, ecdysteroids, and a peptidic brain gonadotropin(s). Compared to vertebrates, the situation in insects with respect to the molecular structure of gonadotropins is far less uniform. Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) of vertebrates are glycoproteins that are synthezised in the hypothalamus and released from the anterior pituitary. They stimulate gonad development, the production of progesterone or of sex steroids (estrogens, androgens). None of the known insect gonadotropins is a glycoprotein, neither can they be grouped into a single peptide family. In Drosophila, two G-protein coupled receptors, structurally related to the mammalian glycoprotein hormone receptors, have been identified. Nothing is known about their natural ligands. The sex-steroids of insects are likely to be ecdysteroids (20E in females, E in males of some species). Some of the identified gonadotropins speed up vitellogenesis (locust OMP and some -PF/-RFamide peptides) or stimulate ecdysteroid production by the ovaries (locust-OMP and Aedes- OEH) or testis (testis ecdysiotropin of Lymantria). In flies, the only as yet identified gonadotropin is the cAMP-generating peptide of Neobellieria. The seeming absence of uniformity in gonadotropins in insects might be due to a multitude of factors that can stimulate ecdysteroid production and/or to the use of different bioassays. Arch.

Electrophysiological characterization of BmK M1, an alpha-like toxin from Buthus martensi Karsch venom

The present study investigates the electrophysiological actions of BmK M1, an alpha-like toxin purified from the venom of the scorpion Buthus martensi Karsch, on voltage-gated Na+ channels. Using the voltage clamp technique, we assessed the BmK M1 activity on the cardiac Na+ channel (hH1) functionally expressed in Xenopus oocytes. The main actions of the toxin are a concentration-dependent slowing of the inactivation process and a hyperpolarizing shift of the steady-state inactivation. This work is the first electrophysiological characterization of BmK M1 on a cloned Na+ channel, demonstrating that this toxin belongs to the class of scorpion alpha-toxins. Our results also show that BmK M1 can be considered as a cardiotoxin.

Peptidomics of the pars intercerebralis-corpus cardiacum complex of the migratory locust, Locusta migratoria

The pars intercerebralis-corpora cardiaca system (PI-CC) of insects is the endocrinological equivalent of the hypothalamus-pituitary system of vertebrates. Peptide profiles of the pars intercerebralis and the corpora cardiaca were characterized using simple sampling protocols in combination with MALDI-TOF and electrospray ionization double quadrupole time of flight (ESI-Qq-TOF) mass spectrometric technologies. The results were compared with earlier results of conventional sequencing methods and immunocytochemical methods. In addition to many known peptides, several m/z signals corresponding to putative novel peptides were observed in the corpora cardiaca and/or pars intercerebralis. Furthermore, for a number of peptides evidence was provided about their localization and MALDI-TOF analysis of the released material from the corpora cardiaca yielded information on the hormonal status of particular brain peptides.

Newly discovered functions for some myotropic neuropeptides in locusts

The field of neuropeptide research in insects during the past twenty years can be characterized by the enormous number of peptides that have been identified. In the locusts, Locusta migratoria and Schistocerca gregaria only, structural information is now available for more than 60 peptides. Quite a number of these peptides were isolated on the basis of their effect on visceral muscle contraction in vitro. A very limited number of reports describe the 'in vivo' function of a myotropic neuropeptide. Moreover, for most of the brain neuropeptides, we ignore whether they have a hormonal function. In this paper, we describe the recently discovered in vivo effects of some of the myotropic peptides, identified in locusts in the past decade. Schistocerca-neuropeptide F accelerates egg development; locustasulfakinin inhibits food intake and [His(7)]-corazonin induces body color pigmentation.

Pyrokinin neuropeptides in a crustacean. Isolation and identification in the white shrimp Penaeus vannamei

Identification of substances able to elicit physiological or behavioural processes that are related to reproduction would greatly contribute to the domestication of commercially important crustaceans that do not reproduce easily in captivity. Crustaceans are thought to release urine signals used for chemical communication involved in courtship behaviour. In contrast to insects, very little is known about the endocrinological processes underlying this phenomenon. Therefore, an extract of 3500 central nervous systems of female white shrimp Penaeus vannamei was screened for myotropic activity in order to purify pyrokinin-like peptides that belong to the pyrokinin/PBAN neuropeptide family. Members of this family regulate reproductive processes in insects, including pheromone biosynthesis. Purification of these pyrokinins was achieved by a combination of reversed-phase and normal-phase chromatography. Subsequent characterization by mass spectrometry, Edman degradation and peptide synthesis resulted in the elucidation of two novel peptides. Pev-PK 1 has the primary sequence DFAFSPRL-NH(2) and a second peptide (Pev-PK 2) is characterized as the nonapeptide ADFAFNPRL-NH(2). Pev-PK 1 contains the typical FXPRL-NH(2) (X = G, S, T or V) C-terminal sequence that characterizes members of the versatile pyrokinin/PBAN family. Pev-PK 2 displays an Asn residue at the variable X position of the core pyrokinin sequence. These crustacean pyrokinins are the first to be found in a noninsect. The synthetic peptides display myotropic activity on the Leucophaea maderae as well as on the Astacus leptodactylus hindgut.

The pigmentotropic hormone [His(7)]-corazonin, absent in a Locusta migratoria albino strain, occurs in an albino strain of Schistocerca gregaria

[His(7)]-corazonin has recently been identified in the corpora cardiaca (CC) of two locust species, the migratory locust, Locusta migratoria and the desert locust, Schistocerca gregaria, as the dark colour inducing neurohormone. Here, we investigate whether [His(7)]-corazonin occurs in the brain-CC axis of a Schistocerca albino strain. From data obtained by immunocytochemistry, injection experiments, chromatographic and mass spectrometric analysis of brain and CC tissues, it could be concluded that an albino strain of S. gregaria from Denmark contains authentic [His(7)]-corazonin. This was unequivocally demonstrated by sequencing the [His(7)]-corazonin-immunoreactive factor in albino Schistocerca brain-CC extracts with ESI-Qq-oa-TOF mass spectrometry. Albinism in this strain is hence not caused by the deficiency of authentic [His(7)]-corazonin in the brain-CC axis, nor by defects in release. Conversely to L. migratoria albinos, injection of [His(7)]-corazonin failed to induce dark pigmentation in Schistocerca albinos. Therefore, albinism in the investigated Schistocerca strain is likely to be situated at the level of the receptor, signal transduction mechanisms or of pigment biosynthesis.

Sulfakinins reduce food intake in the desert locust, Schistocerca gregaria

In vertebrates, the peptides cholecystokinin (CCK), neuropeptide Y, galanin, and bombesin are known to be involved in the control of food intake. We report here that insect sulfakinins, peptides which display substantial sequence similarities with the vertebrate gastrin/CCK peptide family, significantly inhibit food uptake in fifth instar nymphs of the locust, Schistocerca gregaria. Upon injection of Lom-sulfakinin, a neuropeptide present in the corpus cardiacum of locusts, food intake was significantly reduced in a dose-dependent manner within a fixed 20 min time period. The induced effect ranged from 13% inhibition (10 pmol of injected peptide) to over 50% inhibition at 1 nmol. Other naturally occurring sulfakinins from different insect species also elicited this satiety effect. Analogous to the satiety effect of CCK in vertebrates, the sulfate group is required for activity. No effect on the palptip resistance was found after injection with sulfakinin. Therefore it seems unlikly that sulfakinins reduce food intake by decreasing the sensitivity of the taste receptors.

Identification of

The neuropeptides inducing dark color in albino nymphs of the migratory locust Locusta migratoria were isolated from the larval brain of the silkworm, Bombyx mori and from the adult corpora cardiaca (CC) of the cricket Gryllus bimaculatus, respectively, and their amino acid sequences identified. The two peptides isolated from the two different species are identical to [Arg(7)] corazonin, a neuropeptide known to be present in a cockroach and others. This peptide induces a dark color in albino nymphs of L. migratoria at fmol levels, and a high dose of >/=100 pmol caused albino locusts to turn completely black, but it influenced neither body color nor metamorphosis in B. mori and G. bimaculatus. Therefore, the physiological functions of [Arg(7)] corazonin in the silkworm and the cricket remain unknown. The present study demonstrated the usefulness of the albino strain of L. mirgatoria as a specific bioassay system for this peptide.

Identification of novel periviscerokinins from single neurohaemal release sites in insects MS/MS fragmentation complemented by Edman degradation

Three novel members of the periviscerokinin family could be identified directly from extracts of single abdominal perisympathetic organs of blaberoid cockroaches by means of electrospray ionization-quadrupole time of flight (ESI-QTOF) MS. Sequences of these periviscerokinins were confirmed by Edman degradation. Their primary structures are GSSGLIPFGRT-NH2 (Lem-PVK-1), GSSGLISMPRV-NH2 (Lem-PVK-2), and GSSGMIPFPRV-NH2 (Lem-PVK-3). Hitherto only known from the American cockroach, this neuropeptide family contains a highly conserved N-terminus whereas, at the C-terminus, only the penultimate amino-acid residue (Arg) has been found in all members of this peptide family. The identified periviscerokinins are the only abundant myoactive peptides in abdominal perisympathetic organs of blaberoid cockroches and they appear to be absent in the retrocerebral complex. Screening of extracts of single abdominal perisympathetic organs (70-90 microm in diameter), from five different species of the suborder Blaberoidea, revealed that they all contain the three neuropeptides which are described here for the first time.

The kinin peptide family in invertebrates

Kinins comprise a family of peptides that were first found in the central nervous system of insects and recently also in mollusks and crustaceans. After the isolation of the first members of the kinin family, the leukokinins from Leucophaea maderae, leukokinin-related peptides were found in the cricket Acheta domesticus and the locust Locusta migratoria, all through their ability to induce Leucophaea maderae hindgut contraction. Subsequently, kinins were found in the mosquitoes Culex salinarius and Aedes aegypti and in the earworm Helicoverpa zea. The first noninsect member of this family was isolated from a mollusk, the pond snail Lymnaea stagnalis. Most recently our group has isolated the first kinins from crustaceans. Six kinins were isolated from the white shrimp Penaeus vannamei. To date, 35 members of this family have been isolated. The first relatively small family of insect kinins has grown into an expanding and rather large family with members in insects, crustaceans, and mollusks. In this paper we discuss the kinin family in terms of method of isolation, structure, in vitro and in vivo activity, distribution, receptors, and signal transduction. We will compare the crustacean and insect members of the kinin family, using the data available on crustacea.

Identification of a new tachykinin from the midgut of the desert locust, Schistocerca gregaria, by ESI-Qq-oa-TOF mass spectrometry

This paper reports the purification of a tachykinin isoform from the midgut of the desert locust, Schistocerca gregaria. One hundred locust midguts were extracted in an acidified methanolic solvent, after which three HPLC column systems were used to obtain a pure peptide. A tachykinin immunoassay was used to monitor all collected fractions. After each purification step the purity of the sample was monitored by MALDI-TOF mass spectrometry. The pure peptide was sequenced by ESI-Qq-oa-TOF mass spectrometry. Edman degradation-based automated microsequencing and chemical synthesis confirmed the sequences. The midgut peptide, GNTKKAVPGFYGTRamide (Scg-midgut-TK), belongs to the tachykinin family with identified members in all vertebrate phyla and some invertebrate phyla: arthropods, annelids and molluscs. Scg-midgut-TK is the first tachykinin purified from midguts of the desert locust Schistocerca gregaria. In comparison to locust brain tachykinins, the midgut tachykinin is N-terminally extended. Similar to neuropeptide gamma, an N-terminally extended mammalian tachykinin, first isolated from rabbit intestine, the present identified locust intestinal tachykinin contains a putative dibasic cleavage site.

Partial identification of a peptide that stimulates the primary urine production of single isolated Malpighian tubules of the forest ant, Formica polyctena

A peptide was purified from a 10% trifluoroacetic acid (TFA) head/thorax extract of 300,000 ants with high performance liquid chromatography (HPLC). Fluid secretion assay of single isolated Malpighian tubules was used as a bioassay. The purity of F. polyctena diuretic peptide (FopDP) after a two step HPLC protocol was confirmed by means of mass spectrometry and revealed a molecular mass of 7514 daltons. Due to lack of material, no enzymatic digestion could be performed and the sequence of only the first 25 amino acids could be determined: VPKYENCVSEVLPAGDRQRCVKVTC. A computer search of sequence data banks did not reveal any significant similarity between FopDP and other known insect diuretic peptides.FopDP had no effect on the basolateral membrane potential and depolarised the apical membrane potential of the Malpighian tubule cells. This effect as well as the stimulatory effect on the primary urine formation in the Malpighian tubule of the ant, could be mimicked with A23187, a calcium ionophore, and by thapsigargin, an inhibitor of the endoplasmic reticulum calcium ATPase. FopDP did not stimulate the cAMP content. The results suggest that FopDP uses an increase of intracellular calcium as cellular transduction mechanism.

Identification of the gregarization-associated dark-pigmentotropin in locusts through an albino mutant

In response to crowding, locusts develop characteristic black patterns that are well discernible in the gregarious phase at outbreaks. We report here a dark-color-inducing neuropeptide (dark-pigmentotropin) from the corpora cardiaca of two plague locusts, Schistocerca gregaria and Locusta migratoria. The chromatographic isolation of this neuropeptide was monitored by using a bioassay with an albino mutant of L. migratoria. The neurohormone, consisting of 11 amino acids, is identical to [His7] corazonin, previously isolated from corpora cardiaca of another acridid without known function. The present results show that even in isolated (solitary) nymphs, [His7] corazonin induces gregarious black patterns. Its primary structure shows some similarity with the vertebrate melanophore stimulating hormone.

Immunolocalization of a tachykinin-receptor-like protein in the central nervous system of Locusta migratoria migratorioides and neobellieria bullata

Antisera raised against two distinct peptide regions of the Drosophila neurokinin-like receptor NKD were used to immunolocalize tachykinin-receptor-like proteins in the central nervous system of two insect species: the African migratory locust, Locusta migratoria, and the gray fleshfly, Neobellieria bullata. The resulting immunopositive staining patterns were identical for both antisera. Moreover, a very similar distribution of the immunoreactive material was observed in fleshflies and locusts. Immunoreactivity was found in nerve terminals of the retrocerebral complex, suggesting a presynaptic localization of the receptor in this part of the brain. Cell bodies were stained in the subesophageal ganglion: an anterior group of four larger cells and a posterior group of about 20 cells. These cells have axons projecting into the contralateral nervus corporis allati (NCA) II, bypassing the corpus allatum and projecting through the NCA I into the storage part of the corpus cardiacum. In the glandular part of the corpus cardiacum, the glandular adipokinetic hormone-producing cells did not show any immunopositive staining. In the locust, additional immunopositive staining was observed in internolaterally located neurons of the tritocerebrum and in important integrative parts of the neuropil such as the central body and the mushroom bodies.

Several isoforms of locustatachykinins may be involved in cyclic AMP-mediated release of adipokinetic hormones from the locust Corpora cardiaca

Four locustatachykinins (LomTK I-IV) were identified in about equal amounts in extracts of corpora cardiaca of locusts, using reverse-phase high-performance liquid chromatography and radioimmunoassay with synthetic LomTK I-IV as standards. Brain extracts also contained the four isoforms in roughly equimolar concentrations. Retrograde tracing of the nervi corporis cardiaci II (NCC II) in vitro with Lucifer yellow in combination with LomTK immunocytochemistry revealed that about half of the secretomotor neurons in the lateral part of the protocerebrum projecting into the glandular lobe of the corpora cardiaca (CCG) contain LomTK-immunoreactive material. Since the four LomTKs are present in the CCG, these four or five neurons in each hemisphere are likely to contain colocalized LomTK I-IV. The role of two of the LomTKs in the regulation of the release of adipokinetic hormones (AKHs) from the adipokinetic cells in the CCG in the locust was investigated. Experiments performed in vitro showed that LomTK I and II induced release of AKH in a dose-dependent manner. These peptides also rapidly and transiently elevated the cyclic AMP-content of the CCG. The peak level of cyclic AMP occurred about 45 seconds after stimulation with LomTK. These results support the proposal that LomTKs are involved in controlling the release of the adipokinetic hormones and suggest that all LomTK isoforms may participate in this cyclic AMP-mediated event.

Led-NPF-1 stimulates ovarian development in locusts

For more than a decade, immunohistochemical results on FMRFamide related peptides (FaRP's) have been reported extensively, suggesting many possible roles for these peptides associated with behavioural and physiological events as well as reproduction. This study provides a clear effect in vivo of members of this family of insect neuropeptides. The effect of two neuropeptide F-related peptides from the Colorado potato beetle, Leptinotarsa decemlineata, Led-NPF-1 and Led-NPF-2 as well as the locusts myotropins, Lom-PK-1, Lom-PK-2 and Lom-SK, was screened in an ovarian development assay in the African migratory locust and the grey fleshfly, Neobellieria bullata. Led-NPF-1 (Ala-Arg-Gly-Pro-Gln-Leu-Arg-Leu-Arg-Phe-NH2) was shown to be a potent gonadostimulin in Locusta migratoria, but not in Neobellieria bullata. A minimal dose of 0.05 microg of Led-NPF-1 per animal, every 12 h, during 5 consecutive injections into 6 day old virgin females, could accelerate egg development. Higher doses of prolonged injections were demonstrated to be even more potent in the ovarian development assay. Led-NPF-2 (Ala-Pro-Ser-Leu-Arg-Leu-Arg-Phe-NH2) was far less active. The other tested peptides scored no reproducible effect what so ever on ovarian growth, in locusts, nor in flies. The gonadotropic action of a NPF-like peptide on oocyte growth implies a complex regulation of oogenesis in the locust and adds to our knowledge of insect neuroendocrinology in general. The results also suggest that a peptide of similar sequence also resides in the locust.

Angiotensin II and angiotensin-converting enzyme as candidate compounds modulating the effects of testis ecdysiotropin in testes of the gypsy moth, Lymantria dispar1

Lymantria dispar testes synthesize immunodetectable ecdysteroid in vitro in response to the brain peptide, testis ecdysiotropin (TE), acting primarily via a cascade involving Gi protein, diacyl glycerol, and phosphokinase C. However, a component of TE activation also involves the opposite cascade, Gs protein, cAMP, and phosphokinase A. Excess cAMP inhibits the action of TE, acting as a feedback modulator. Here, we show that bovine angiotensin II (AII) and bovine angiotensin converting enzyme (ACE) act like cAMP, inducing synthesis of immunodetectable ecdysteroid by pupal testes in vitro, but are antagonistic to coincubated TE. In addition, an insect ACE antibody clearly stains the spermatogenic cells through all stages of development, as well as testis sheath tissue where ecdysteroid is synthesized. AII induces synthesis of cAMP by pupal testes in vitro. Therefore, insect homologs of mammalian AII and ACE are good candidates for the peptides responsible for the cAMP cascade and as modulators of TE action in lepidopteran testes. Saralasin, an analog of AII that blocks angiotensin receptors in mammals, behaved like AII in inducing ecdysteroid secretion with ecdysteroidogenic effects additive to either angiotensin or ACE. Therefore, the receptors for the insect form of angiotensin on lepidopteran testis cells are probably different from those in mammals. Saralasin also inhibited ecdysteroid synthesis when combined with TE, as did AII.

Identification of one tachykinin- and two kinin-related peptides in the brain of the white shrimp, Penaeus vannamei

This paper reports the purification of three myotropic neuropeptides from the white shrimp Penaeus vannamei. The central nervous systems of 3500 shrimps were extracted in an acidified solvent, after which four to five HPLC column systems were used to obtain pure peptides. A cockroach hindgut muscle contraction bioassay was used to monitor all collected fractions. The pure peptides were submitted to Edman degradation based automated microsequencing. Mass spectrometry and chemical synthesis confirmed the sequences. Ala-Pro-Ser-Gly-Phe-Leu-Gly-Met-Arg-NH2 (Pev-tachykinin, 934.1 Da) belongs to the tachykinin family with identified members in all vertebrate classes and some invertebrate classes: arthropods, annelids and molluscs. A very specific Pev-tachykinin antiserum was developed, which labels 4 neurosecretory cells in the brain. Ala-Ser-Phe-Ser-Pro-Trp-Gly-NH2 (Pev-kinin 1, 749.8 Da) and Asp-Phe-Ser-Ala-Trp-Ala-NH2 (Pev-kinin 2, 694.7 Da) are the first crustacean kinins. Pev-kinin 2 is the first kinin with a Trp-Ala-NH2 instead of a kinin-typical Trp-Gly-NH2 carboxyterminus.

Purification of toxic compounds from larvae of the gray fleshfly: the identification of paralysins

Larval haemolymph of Neobellieria bullata (Insecta, Diptera) is highly toxic to adults of the same species: injection causes instant paralysis to death. Referring to their dramatic effect in adult insects the responsible compounds were designated paralysins. Two paralysins, soluble in organic solvents and heat stable, were chromatographically purified to homogeneity. They were identified by use of mass spectrometry and nuclear magnetic resonance respectively as beta-alanine-tyrosine (beta-Ala-Tyr) and as 3-hydroxy-kynurenine (3-HK). The quantities of beta-Ala-Tyr and 3-HK in the insect appear to increase steadily during larval development, with peak values prior to the pupal stage. These findings may contribute to a better understanding of some aspects of the process of insect metamorphosis. Orienting experiments in mammals suggest that both compounds, when injected intraspinally, are also neurotoxic to rats. In addition, cytotoxicity tests revealed that 3-HK, but not beta-Ala-Tyr is toxic to human neuroblastoma cells, rat primary cortex neurons as well as to rat glial cells.

Cloning of two cDNAs encoding three small serine protease inhibiting peptides from the desert locust Schistocerca gregaria and analysis of tissue-dependent and stage-dependent expression

This study describes the cloning of two cDNAs encoding three serine-protease-inhibiting peptides, SGPI I, II and III, which were recently identified from ovarian extracts of the desert locust, Schistocerca gregaria. The first cDNA codes for the precursor polypeptides of SGPI I and SGPI II; the second encodes only a single inhibitor, SGPI III. Northern-blot analysis revealed an approximate length of 0.8 kb for SGPI-I/II mRNA and 0.6 kb for SGPI-III mRNA. The transcripts are present in several locust tissues, but they could not be detected in the midgut. The gene for SGPI-I/II is abundantly transcribed during all larval and adult stages, whereas SGPI-III mRNA is mainly present in adults. Northern-blot hybridization also revealed important changes in the SGPI-mRNA content during the molting cycle and during the adult reproductive cycle. Moreover, a differential hormonal control was observed in adult females which had been treated with precocene, juvenile hormone or ecdysone.