A comparison of the neuropeptides from the retrocerebral complex of adult male and female Manduca sexta using MALDI-TOF mass spectrometry

Structure-activity relationship of adipokinetic hormone analogs in the striped hawk moth, Hippotion eson

We showed previously that the sphingid moth Hippotion eson synthesizes the highest number of adipokinetic hormones (AKHs) ever recorded, viz. five, in its corpus cardiacum: two octa-, two nona- and one decapeptide. Further, the endogenous decapeptide (Manse-AKH-II) and the other four AKHs are all active in lipid mobilization, whereas a non-lepidopteran decapeptide (Lacsp-AKH, five amino acid substitutions compared with Manse-AKH-II), was inactive in H. eson. We tested the decapeptide, Lacol-AKH, from a noctuid moth for the first time in a bioassay and it shows a maximal AKH effect in H. eson. Lacol-AKH differs from Manse-AKH-II in three places and from Lacsp-AKH in four places. We, thus, used Lacol-AKH as a lead peptide on which a series of AKH analogs are based to represent: (a) single amino acid replacements (according to the substitutions in Lacsp-AKH), (b) shorter chain lengths, (c) modified termini, and (d) a replacement of Trp in position 8. These analogs, as well as a few naturally occurring AKHs from other lepidopterans were tested in in vivo adipokinetic assays to gain insight into the ligand-receptor interaction in H. eson. Our results show that the second and third amino acids are important for biological activity in the sphingid moth. Analogs with an N-[acetylated]Glu(1) (instead of a pyroGlu), or a free C-terminus, or Ala(8) were not active in the bioassays, while shortened Lacol-AKH analogs and the undecapeptide, non-amidated Vanca-AKH showed very reduced activity (below 25%). This information is important for the consideration of peptide mimetics to combat specific lepidopteran pest insects.

Genomic and peptidomic analyses of the neuropeptides from the emerging pest, Drosophila suzukii

Drosophila suzukii is a highly polyphagous invasive pest which has been recently introduced into Europe and North America, where it is causing severe economic losses through larval infestations of stone and berry fruits. The peptidome of the selected nervous tissues of adult D. suzukii was investigated as a first step in identifying potential targets for the development of novel insecticides. Through in silico analyses of the D. suzukii genome databases 28 neuropeptide families, comprising more than 70 predicted peptides were identified. Using a combination of liquid chromatography and mass spectrometry of tissue extracts, 33 predicted peptides, representing 15 different peptide families were identified by their molecular masses and a total of 17 peptide sequences were confirmed by ion fragmentation. A comparison between the peptides and precursors of D. suzukii and D. melanogaster shows they are highly conserved, with differences only identified in the amino acid sequences of the peptides encoded in the FMRFamide, hugin and ecydysis triggering hormone precursors. All other peptides predicted and identified from D. suzukii appear to be identical to those previously characterized from D. melanogaster. Adipokinetic hormone was only identified in the corpus cardiacum, other peptides present included short neuropeptide F, a pyrokinin and myosuppressin, the latter of which was the only peptide identified from the crop nerve bundle. Peptides present in extracts of the brain and/or thoracico-abdominal ganglion included allatostatins, cardioacceleratory peptide 2b, corazonin, extended FMRFamides, pyrokinins, myoinihibitory peptides, neuropeptide-like precursor 1, SIFamide, short neuropeptide F, kinin, sulfakinins and tachykinin related peptides.

Adipokinetic hormones (AKHs) of sphingid Lepidoptera, including the identification of a second M. sexta AKH

The adipokinetic hormones (AKHs) from the corpora cardiaca (CC) of representative species from all three subfamilies of the Sphingidae (hawkmoths) were investigated using matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) and liquid chromatography electrospray ion trap mass spectrometry (LC-ESI MS), including a re-examination of the AKH complement of the tobacco hawkmoth, Manduca sexta. In addition to larvae and adults of M. sexta (subfamily: Sphinginae), adults from the following subfamilies were examined: Macroglossinae (large elephant hawkmoth, Deilephila elpenor), Smerinthinae (poplar hawkmoth, Laothoe populi and eyed hawkmoth, Smerinthus ocellata), and Sphinginae (death's head hawkmoth, Acherontia atropos). All moths are shown to have the nonapeptide Manse-AKH (pELTFTSSWGamide) [corrected] in their CC, together with a second AKH, which, on the basis of mass ions ([M+Na](+), [M+K](+)) and partial sequence analysis is identical in all species examined. The structure of this AKH was extracted from the CC [corrected] of adult M. sexta and shown, by ESI-collision-induced dissociation (CID) tandem mass spectrometry (MS/MS), to be a novel decapeptide AKH with a sequence of pELTFSSWGQamide. [corrected]. The new peptide has been code named Manse-AKH-II. Sequence confirmation was obtained from identical MS studies with synthetic Manse-AKH-II and with the native peptide. Manse-AKH-II has significant lipid-mobilizing activity when injected at low dose (5pmol) into newly emerged adult M. sexta. The potential implications of a second AKH, in M. sexta in particular, are discussed in relation to putative receptor(s).

Neuropeptides associated with the central nervous system of the cabbage root fly, Delia radicum (L)

The peptidome of the central nervous system of adult cabbage root fly, Delia radicum (L) was investigated using matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). Over twenty neuropeptides were identified from three different tissue sources, the combined brain/suboesophageal ganglion (SOG), the retrocerebral complex, and the thoracic-abdominal ganglion (TAG). A number of peptides were identified in all three tissues, including allatostatins, short neuropeptide F-like peptides, corazonin, a pyrokinin, and a myosuppressin. Adipokinetic hormone was restricted to the retrocerebral complex. Other peptides, including FMRFamides and sulfakinins were detected only in the brain/SOG and TAG. Some peptides, notably myoinhibitory peptides and tachykinins, which have been identified in other fly species, were not detected in any tissue sample. This study has structurally characterized for the first time, the neuropeptides from adult D. radicum.

In search for a common denominator for the diverse functions of arthropod corazonin: a role in the physiology of stress?

Corazonin (Crz) is an 11 amino acid C-terminally amidated neuropeptide that has been identified in most arthropods examined with the notable exception of beetles and an aphid. The Crz-receptor shares sequence similarity to the GnRH-AKH receptor family thus suggesting an ancestral function related to the control of reproduction and metabolism. In 1989, Crz was purified and identified as a potent cardioaccelerating agent in cockroaches (hence the Crz name based on "corazon", the Spanish word for "heart"). Since the initial assignment as a cardioacceleratory peptide, additional functions have been discovered, ranging from pigment migration in the integument of crustaceans and in the eye of locusts, melanization of the locust cuticle, ecdysis initiation and in various aspects of gregarization in locusts. The high degree of structural conservation of Crz, its well-conserved (immuno)-localization, mainly in specific neurosecretory cells in the pars lateralis, and its many functions, suggest that Crz is vital. Yet, Crz-deficient insects develop normally. Upon reexamining all known effects of Crz, a hypothesis was developed that the evolutionary ancient function of Crz may have been "to prepare animals for coping with the environmental stressors of the day". This function would then complement the role of pigment-dispersing factor (PDF), the prime hormonal effector of the clock, which is thought "to set a coping mechanism for the night".

MALDI-TOF mass spectrometry approaches to the characterisation of insect neuropeptides

The diversity of insect neuropeptides coupled with the limitations from the small size of the insects themselves combine to make positive identification through peptide sequencing a highly challenging task. The advent of the "soft-ionisation" techniques of MALDI-TOF and electrospray (ESI)-Q-TOF mass spectrometry, coupled with the additional information from insect genome projects have revolutionised the characterisation of insect neuropeptides, such that sequences can now be obtained from just a few cells, where before thousands of insects had to be laboriously dissected, extracted and purified. Some of the procedures that are now used to identify these peptides are described here. Once the neuropeptides have been identified, it then becomes possible to use this knowledge to define physiological functionality.

Flight-related metabolism and its regulatory peptides in the spittle bug Locris arithmetica (Cicadomorpha: Cercopidae) and the stink bugs Nezara viridula (Heteroptera: Pentatomidae) and Encosternum delegorguei (Heteroptera: Tessaratomidae)

Three species of bugs (Order: Hemiptera) belonging to different suborders and different families were investigated with respect to flight-related metabolism, and the neuropeptide hormones that regulate metabolism in Encosternum delegorguei, Locris arithmetica and Nezara viridula were characterised. The concentration of two potential metabolic fuels in the haemolymph of these bugs (at rest) revealed that lipids were more abundant than carbohydrates and that lipids increased significantly when the bugs performed extensive exercise (flight) and in the resting period following the aerobic activity. Carbohydrate levels declined during flight but recovered to the pre-flight level during a 1h resting period post-flight. Further experiments with N. viridula revealed greater lipid accumulation in the haemolymph after a 10min flight than after a 2min flight and significant activation of glycogen phosphorylase was recorded in the fat body immediately after flight activity. Crude extracts of corpora cardiaca (CC) from L. arithmetica and E. delegorguei were both active in mobilising carbohydrates in the cockroach Periplaneta americana. In conspecific assays, only L. arithmetica CC extract had a significant hypertrehalosaemic effect, while CC extracts from both E. delegorguei and L. arithmetica were hyperlipaemic. By a combination of liquid chromatography and mass spectrometry two octapeptides known as Peram-CAH-I and Pyrap-AKH were identified from the spittle bug, L. arithmetica, and two octapeptides known as Panbo-RPCH and Schgr-AKH-II were identified from the edible inflated stink bug, E. delegorguei. Injection of Panbo-RPCH into E. delegorguei and into the green stink bug, N. viridula had no effect on circulating carbohydrates, although glycogen phosphorylase was activated in the fat body. The circulating lipid concentration in N. viridula did not change significantly under artificially induced hypertrehalosaemia, suggesting that lipids were not being used or mobilised.

Peptides of the adipokinetic hormone/red pigment-concentrating hormone family with special emphasis on Caelifera: primary sequences and functional considerations contrasting grasshoppers and locusts

The presented work is a hybrid of an overview and an original research paper. First, we review briefly the structure, biosynthesis, release, mode of action and function of those peptides that constitute the adipokinetic/red pigment-concentrating family. Second, we collate the data on primary sequences available for caeliferan orthoptera, i.e. grasshoppers and locusts, and add a number of new data from previously unpublished work. The data are interpreted in conjunction with morphological and molecular biology data with respect to phylogenetic relationships of these various taxa. Finally, we discuss the differences between the adipokinetic response of grasshoppers and locusts to corpus cardiacum extract or synthetic adipokinetic hormone with regard to flight ability, phase polymorphism, age, presence of adipokinetic hormones, lipophorin system and other parameters. It appears that the higher hyperlipaemic response is always correlated with pronounced flight ability.

A proteomic approach for studying insect phylogeny: CAPA peptides of ancient insect taxa (Dictyoptera, Blattoptera) as a test case

Background

Neuropeptide ligands have to fit exactly into their respective receptors and thus the evolution of the coding regions of their genes is constrained and may be strongly conserved. As such, they may be suitable for the reconstruction of phylogenetic relationships within higher taxa. CAPA peptides of major lineages of cockroaches (Blaberidae, Blattellidae, Blattidae, Polyphagidae, Cryptocercidae) and of the termite Mastotermes darwiniensis were chosen to test the above hypothesis. The phylogenetic relationships within various groups of the taxon Dictyoptera (praying mantids, termites and cockroaches) are still highly disputed.

Results

Tandem mass spectrometry of neuropeptides from perisympathetic organs was used to obtain sequence data of CAPA peptides from single specimens; the data were analysed by Maximum Parsimony and Bayesian Interference. The resulting cladograms, taking 61 species into account, show a topology which is in general agreement with recent molecular and morphological phylogenetic analyses, including the recent phylogenetic arrangement placing termites within the cockroaches. When sequence data sets from other neuropeptides, viz. adipokinetic hormones and sulfakinins, were included, the general topology of the cladogram did not change but bootstrap values increased considerably.

Conclusion

This study represents the first comprehensive survey of neuropeptides of insects for solely phylogenetic purposes and concludes that sequences of short neuropeptides are suitable to complement molecular biological and morphological data for the reconstruction of phylogenetic relationships.

Biological activity and identification of neuropeptides in the neurosecretory complexes of the cabbage pest insect, Mamestra brassicae (Noctuidae; Lepidoptera)

The need for more environmentally sound strategies of plant protection has become a driving force in physiological entomology to combat insect pests more efficiently. Since neuropeptides regulate key biological processes, these "special agents" or their synthetic analogues, mimetics, agonists or antagonists may be useful tools. We examined brain-suboesophageal ganglia and corpora cardiaca-corpora allata complexes of the cabbage moth, Mamestra brassicae, in order to obtain clues about possible peptide candidates which may be appropriate for the biological control of this pest. With the aid of bioassays, reversed phase high performance liquid chromatography, and mass spectrometry, five neuropeptides were unequivocally identified and the presence of a further three were inferred solely by comparing mass spectra with known peptides. Only one neuropeptide with adipokinetic capability was identified in M. brassicae. Data from the established homologous bioassay indicated that the cabbage moths rely on a lipid-based metabolism which is aided by an adipokinetic hormone (viz. Manse-AKH) that had previously been isolated in many different lepidopterans. Other groups of neuropeptides identified in this study are: FLRFamides, corazonin, allatostatin and pheromonotropic peptide.

Predicted versus expressed adipokinetic hormones, and other small peptides from the corpus cardiacum-corpus allatum: a case study with beetles and moths

This mass spectrometric study confines itself to peptide masses in the range of 500-1500Da. Adipokinetic hormones (AKHs) that are predicted from the genome of the red flour beetle, Tribolium castaneum, and the silk moth, Bombyx mori, are shown to exist as expressed peptides in the corpora cardiaca (CC) of the respective species as evidenced by various mass spectrometric methods. Additionally, some related species were included in this study, such as the tenebrionid beetles Tribolium brevicornis and Tenebrio molitor, as well as the moths Spodoptera frugiperda, Spodoptera littoralis, Mamestra brassicae and Lacanobia oleracea, to investigate whether AKH peptides are structurally conserved in the same genus or family. Interestingly, the AKH peptide of T. brevicornis is identical to that of T. molitor but not to the ones of its close relative T. castaneum. Moreover, other peptides in T. brevicornis, such as various FXPRL amides (=pyrokinins), also match the complement in T. molitor but differ from those in T. castaneum. All the CC of beetles lacked the signal for the mass of the peptide corazonin. All moths have the nonapeptide Manse-AKH expressed in their CC. In addition, whereas the silk moth has the decapeptide Bommo-AKH as a second peptide, all other moths (all noctuids) express the decapeptide Helze-HrTH. In M. brassicae and L. oleracea a novel amidated Gly-extended Manse-AKH is found as a possible third AKH. The noctuid moth species also all express the same FLRF amide-I, corazonin, and a group-specific isoform of a gamma-PGN-(=gamma-SGNP) peptide. In L. oleracea, however, the latter peptide has a novel sequence which is reported for the first time, and the peptide is code-named Lacol-PK.

The roles of Dippu-allatostatin in the modulation of hormone release in Locusta migratoria

Dippu-allatostatins (ASTs) have pleiotropic effects in Locusta migratoria. Dippu-ASTs act as releasing factors for adipokinetic hormone I (AKH I) from the corpus cardiacum (CC) and also alter juvenile hormone (JH) biosynthesis and release from the corpus allatum (CA). Dippu-AST-like immunoreactivity is found within lateral neurosecretory cells (LNCs) of the brain and axons within the paired nervi corporis cardiaci II (NCC II) to the CC and the CA, where there are extensive processes and nerve endings over both of these neuroendocrine organs. There was co-localization of Dippu-AST-like and proctolin-like immunoreactivity within these regions. Dippu-ASTs increase the release of AKH I in a dose-dependent manner, with thresholds below 10(-11)M (Dippu-AST 7) and between 10(-13) and 10(-12)M (Dippu-AST 2). Both proctolin and Dippu-AST 2 caused an increase in the cAMP content of the glandular lobe of the CC. Dippu-AST 2 also altered the release of JH from the locust CA, but this effect depended on the concentration of peptide and the basal release rates of the CA. These physiological effects for Dippu-ASTs in Locusta have not been shown previously.

Allatoregulatory peptides in Lepidoptera, structures, distribution and functions

Allatoregulatory peptides either inhibit (allatostatins) or stimulate (allatotropins) juvenile hormone (JH) synthesis by the corpora allata (CA) of insects. However, these peptides are pleitropic, the regulation of JH biosynthesis is not their only function. There are currently three allatostatin families (A-, B-, and C-type allatostatins) that inhibit JH biosynthesis, and two structurally unrelated allatotropins. The C-type allatostatin, characterised by its blocked N-terminus and a disulphide bridge between its two cysteine residues, was originally isolated from Manduca sexta. This peptide exists only in a single from in Lepidoptera and is the only peptide that has been shown to inhibit JH synthesis by the CA in vitro in this group of insects. The C-type allatostatin also inhibits spontaneous contractions of the foregut. The A-type allatostatins, which exist in multiple forms in a single insect, have also been characterised from Lepidoptera. This family of peptides does not appear to have any regulatory effect on JH biosynthesis, but does inhibit foregut muscle contractions. Two structurally unrelated allatotropins stimulate JH biosynthesis in Lepidoptera. The first was identified in M. sexta (Manse-AT) and occurs in other moths. The second (Spofr AT2) has only been identified in Spodoptera frugiperda. Manduca sexta allatotropin also stimulates heart muscle contractions and gut peristalsis, and inhibits ion transport across the midgut of larval M. sexta. The C-terminal (amide) pentapeptide of Manse-AT is important for JH biosynthesis activity. The most active conformation of Manse-AS requires the disulphide bridge, although the aromatic residues also have a significant effect on biological activity. Both A- and C-type allatostatins and Manse-AT are localised in neurosecretory cells of the brain and are present in the corpora cardiaca, CA and ventral nerve cord, although variations in localisation exist in different moths and at different stages of development. The presence of Manse-AS and Manse-AT in the CA correlates with the biological activity of these peptides on JH biosynthesis. There is currently no explanation for the presence of A-type allatostatins in the CA. The three peptide types are also co-localised in neurosecretory cells of the frontal ganglion, and are present in the recurrent nerve that supplies the muscles of the gut, particularly the crop and stomodeal valve, in agreement with their role in the regulation of gut peristalsis. There is also evidence that they are expressed in the midgut and reproductive tissues.

Transepithelial flux of an allatostatin and analogs across the anterior midgut of Manduca sexta larvae in vitro

The transepithelial flux of cydiastatin 4 and analogs across flat sheet preparations of the anterior midgut of larvae of the tobacco hawkmoth moth, Manduca sexta, was investigated using a combination of reversed-phase high-performance liquid chromatography (RP-HPLC), enzyme-linked immunosorbent assay (ELISA) and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The lumen to hemolymph (L-H) flux of cydiastatin 4 was dose and time-dependent, with a maximum rate of flux of c. 178 pmol/cm2/h) measured after a 60-min incubation with 100 micromol/l of peptide in the lumen bathing fluid. The rates of flux, L-H and H-L, across the isolated gut preparations were not significantly different. These data suggest that uptake across the anterior midgut of larval M. sexta is via a paracellular route. Cydiastatin 4 was modified to incorporate a hexanoic acid (Hex) moiety at the N-terminus, the N-terminus extended with 5 P residues and/or the substitution of G7 with Fmoc-1-amino-cyclopropylcarboxylic acid (Acpc). The incorporation of hexanoic acid enhanced the uptake of these amphiphilic analogs compared to the native peptide. Analogs were also more resistant to enzymes in hemolymph and gut preparations from larval M. sexta. A modified N-terminus gave protection against aminopeptidase-like activity and incorporation of Acpc inhibited endopeptidase-like activity. Although analogs were stable in the hemolymph, they were susceptible to amidase-like activity in the gut, which appears to convert the C-terminal amide group to a free carboxylic acid, identified by an increase in 1 mass unit of the peptide analog.

Neuropeptides of the beetle, Tenebrio molitor identified using MALDI-TOF mass spectrometry and deduced sequences from the Tribolium castaneum genome

Four neuropeptides were identified from the brain and corpora cardiaca-corpora allata (CC-CA) of the mealworm beetle Tenebrio molitor using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) and information derived from the genome of the red flour beetle, Tribolium castaneum. Leucomyosuppressin (a FLRFamide), previously associated with cockroaches, but also subsequently identified from honey bee seen as a prominent peptide in both brain and CC-CA of T.molitor. A coding sequence for this peptide is found in the genome of T. castaneum. In addition, three FXPRLamides (pyrokinins), provisionally Tenmo-PK-1, Tenmo-PK-2 and Tenmo-PK-3 (HVVNFTPRLamide, SPPFAPRLamide, HL(I)SPFSPRLamide) were identified in both CC-CA and brain of T. molitor, again on the basis of predicted occurrence or similarity in T. castaneum. The sequence of Tenmo-PK-2 is the same as the PK-2 of the cockroach, Periplaneta americana. Other peptides readily predicted from the genome of T. castaneum include two AKH/HrTH peptides (Trica-AKH-1; pELNFSTDWamide and Trica-AKH-2; pELNFTPNWamide), the second of which is identical to Pyrap-AKH, an AKH-related peptide (Trica AKH-L; pEVTFSRDWPamide), two CRF-related diuretic factors (Trica-DH 37 and Trica-DH 47), the latter identical to Tenmo-DH 47, a putative antidiuretic factor (Trica-ADFb; LYDDGSYKPHVYGF-OH), two sulfakinin-like peptides (Trica-SK-1; pETSDDY(SO(3))GHLRFamide, and Trica SK-2; GEEPFDDYGHMRFamide), a potential allatostatin-C (Trica-AS; pESRYRQCYFNPISCF-OH), six allatostatin-B/myoinhibitory peptides (Trica-AST-B-1,2,3,4,5 & 6; DWNKDLHIWamide, GWNNLHEGWamide, AWQSLQSGWamide, NWGQFHGGWamide, SKWDNFRGSWamide, EPAWSNLGIWamide), an allatotropin-like peptide (Trica-ATL; GIEALKYHNMDLGTARGYamide), four 'CAPA'-related peptides (Trica-CAPA-1,2,3,4; NKLASVYALTPSLRVamide, RIGKMVSFPRIamide, PGANSGGMWFGPRLamide, SENFTPWAYIILNGEAPIIREVHYSPRLamide), proctolin (RYLPT), a potential SIFamide (Trica-SIFa; TYRKPPFNGSIFamide), an arginine-vasopressin-related peptide (Trica-AVP; CLITNCPRGamide) and an ITP-related peptide (Trica-ITP). No evidence was found for the presence of 'A' allatostatins (Y/FxFGLamides) or corazonin, either in T. molitor, or in the genome of T. castaneum.

The adipokinetic hormones in the fall armyworm, Spodoptera frugiperda: cDNA cloning, quantitative real time RT-PCR analysis, and gene specific localization

Small neuropeptides of the adipokinetic/red pigment-concentrating hormone (AKH/RPCH) family regulate energy metabolism in insects. Within lepidopterans, the nonapeptide Manduca sexta AKH (Manse-AKH) represents a widely occurring AKH, whereas the decapeptide Helze-HrTH (at first isolated from Helicoverpa zea) seems to be restricted to moths. Here we report the identification of the Manse-AKH-like Spofr-AKH 1 and the Helze-HrTH-like Spofr-AKH 2 prohormone precursors from the fall armyworm, Spodoptera frugiperda. Moreover, by PCR screening of a random primer cDNA library and by RACE, three 668, 835 and 1008 bp cDNA sequences were obtained, which encode putative translation products of 67-74 amino acids, each containing one copy of a peptide sequence that in its processed form has the sequence of QLTFSSGW-amide (Spofr-AKH 3). Another cDNA sequence of 634 bp encodes a putative translation product of 40 amino acids, potentially leading to one copy of an elongated, non-amidated Helze-HrTH (pQLTFSSGWGNCTS-OH; Spofr-AKH 4). Q-RT-PCR analysis showed that the Spofr-AKH mRNAs are expressed in 2d-old female brain/corpora cardiaca complexes, but also in ovaries, midgut, fat body, accessory glands and muscle tissues. Expression was also found in the ovaries of 4d-old females. Whole-mount in situ RT-PCR analysis with ovaries from 2d-old females showed that the Spofr-AKH 2 and Spofr-AKH 4 were mainly localized in the germarium (phase 3), whereas the Spofr-AKH 1, and the three mRNA isoforms of Spofr-AKH 3 were localized at the end of the vitellarium and in the fully developed oocytes (phase 1 and 2). The results suggest that Spofr-AKH genes play a role in the regulation of oocyte maturation in S. frugiperda.

Direct peptide profiling of lateral cell groups of the antennal lobes ofManduca sextareveals specific composition and changes in neuropeptide expression during development

The paired antennal lobes are the first integration centers for odor information in the insect brain. In the sphinx moth Manduca sexta, like in other holometabolous insects, they are formed during metamorphosis. To further understand mechanisms involved in the formation of this particularly well investigated brain area, we performed a direct peptide profiling of a well defined cell group (the lateral cell group) of the antennal lobe throughout development by MALDI-TOF mass spectrometry. Although the majority of the about 100 obtained ion signals represent still unknown substances, this first peptidomic characterization of this cell group indicated the occurrence of 12 structurally known neuropeptides. Among these peptides are helicostatin 1, cydiastatins 2, 3, and 4, M. sexta-allatotropin (Mas-AT), M. sexta-FLRFamide (Mas-FLRFamide) I, II, and III, nonblocked Mas-FLRFamide I, and M. sexta-myoinhibitory peptides (Mas-MIPs) III, V, and VI. The identity of two of the allatostatins (cydiastatins 3 and 4) and Mas-AT were confirmed by tandem mass spectrometry (MALDI-TOF/TOF). During development of the antennal lobe, number and frequency of ion signals including those representing known peptides generally increased at the onset of glomeruli formation at pupal Stage P7/8, with cydiastatin 2, helicostatin 1, and Mas-MIP V being the exceptions. Cydiastatin 2 showed transient occurrence mainly during the period of glomerulus formation, helicostatin 1 was restricted to late pupae and adults, while Mas-MIP V occurred exclusively in adult antennal lobes. The power of the applied direct mass spectrometric profiling lies in the possibility of chemically identifying neuropeptides of a given cell population in a fast and reliable manner, at any developmental stage in single specimens. The identification of neuropeptides in the antennal lobes now allows to specifically address the function of these signaling molecules during the formation of the antennal lobe network.

In vitro transport of an allatostatin across the foregut of Manduca sexta larvae and metabolism by the gut and hemolymph

The degradation of synthetic cydiastatin 4 by enzymes of the foregut and hemolymph, and transport across the foregut of larvae of the tobacco hawkmoth moth, Manduca sexta, were investigated using reversed-phase high performance liquid chromatography (RP-HPLC) together with matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). In the hemolymph in vitro, cydiastatin 4 had a half-life of ca. 30 min. Two degradation products were identified; cydiastatin 4(1-6), due to cleavage of the C-terminal di-peptide GL-amide, and cydiastatin 4(2-8), due to cleavage of the N-terminal A residue. This hydrolysis could be inhibited by up to 93% by 1,10-phenanthroline. Other protease inhibitors had lesser effects (<21% inhibition of degradation) including the aminopeptidase inhibitors amastatin and bestatin, and the chelator EDTA. When incubated with foregut extract in vitro, cydiastatin 4 had a half-life of 23 min, and the hydrolysis products detected were also cydiastatin 4(1-6) and cydiastatin 4(2-8). Similarly, 1-10 phenanthroline inhibited foregut enzyme degradation of cydiastatin 4 by ca. 80%, whereas amastatin, bestatin, and EDTA had very little effect (<10% inhibition). Cydiastatin 4 was transported, intact, from the lumen to the hemolymph side of foregut tissues that were mounted as flat sheets in modified Ussing chambers. This trans-epithelial flux of peptide was dose and time-dependent, but was <3% of the amount of cydiastatin 4 present in the lumen bathing saline. In contrast, no trans-epithelial transport of peptide was apparent across everted foregut sac preparations.

Distribution of neuropeptides in the primary olfactory center of the heliothine moth Heliothis virescens

Neuropeptides are a diverse widespread class of signaling substances in the nervous system. As a basis for the analysis of peptidergic neurotransmission in the insect olfactory system, we have studied the distribution of neuropeptides in the antennal lobe of the moth Heliothis virescens. Immunocytochemical experiments with antisera recognizing A-type allatostatins (AST-As), Manduca sexta allatotropin (Mas-AT), FMRFamide-related peptides (FaRPs), and tachykinin-related peptides (TKRPs) have shown that members of all four peptide families are present in local interneurons of the antennal lobe. Whereas antisera against AST-As, Mas-AT, and FaRPs give similar staining patterns characterized by dense meshworks of processes confined to the core of all antennal-lobe glomeruli, TKRPs are present only in neurons with blebby processes distributed throughout each glomerulus. In addition to local neurons, a pair of centrifugal neurons with cell bodies in the lateral subesophageal ganglion, arborizations in the antennal lobe, and projections in the inner antenno-cerebral tracts exhibits tachykinin immunostaining. Double-label immunofluorescence has detected the co-localization of AST-As, Mas-AT, and FaRPs in certain local interneurons, whereas TKRPs occurs in a distinct population. MALDI-TOF mass spectrometry has revealed nearly 50 mass peaks in the antennal lobe. Seven of these masses (four AST-As, two N-terminally extended FLRFamides, and Mas-AT) match known moth neuropeptides. The data thus show that local interneurons of the moth antennal lobe are highly differentiated with respect to their neuropeptide content. The antennal lobe therefore represents an ideal preparation for the future analysis of peptide signaling in insect brain.

Analysis of peptides in the brain and corpora cardiaca-corpora allata of the honey bee, Apis mellifera using MALDI-TOF mass spectrometry

The neuropeptide profiles and diversity of the brain and retrocerebral organs (corpora cardiaca-corpora allata; CC-CA) of adult workers of the honey bee Apis mellifera carnica (dark European strain) were investigated using a combination of HPLC and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) with post-source decay (PSD) and collision-induced dissociation (CID) fragmentation. Using evidence from genomic sources, including BLAST searches of the honey bee genome, comparisons with other species and de novo sequencing by PSD and CID fragmentation, a total of 13 mass ions could be assigned to peptides predicted from the A. mellifera genomic database. Peptides positively identified were A. mellifera tachykinin-related peptides 3 and 4 (APMGFQGMRa; APMGFYGTRa) and leucomyosuppressin (pEDVDHVFLRFa). Peptides tentatively identified were A. mellifera tachykinin-related peptides 2 and 5 (ALMGFQGVRa; ARMGFHGMRa), A. mellifera allatostatins 2, 3 and 4 (GRDYSFGLa; RQYSFGLa; GRQPYSFGLa), A1-SIFamide (AYRKPPFNGSIFa), Q1-leucomyosuppressin (QDVDHVFLRFa) and A. mellifera pyrokinins PK 1, PK 2 and Q1-PK 2 (TSQDITSGMWFGPRLa; pEITQFTPRLa; QITQFTPRLa). Allatostatins, tachykinin-related peptides and A1-SIFamide were not detected in CC-CA extract, which appears to contain predominantly leucomyosuppressin, Q1-leucomyosuppressin, PK 1, PK 2, Q1-PK 2 and some unidentified masses. No ion signal was detected that would correspond to the hypertrehalosaemic peptide (=Manse-AKH), which has been isolated from the Italian race of the honey bee (A. mellifera ligustica), but not from A. mellifera carnica.

Direct mass spectrometric peptide profiling and fragmentation of larval peptide hormone release sites in Drosophila melanogaster reveals tagma-specific peptide expression and differential processing

Regulatory peptides represent a diverse group of messenger molecules. In insects, they are produced by endocrine cells as well as secretory neurones within the CNS. Many regulatory peptides are released as hormones into the haemolymph to regulate, for example, diuresis, heartbeat or ecdysis behaviour. Hormonal release of neuropeptides takes place at specialized organs, so-called neurohaemal organs. We have performed a mass spectrometric characterization of the peptide complement of the main neurohaemal organs and endocrine cells of the Drosophila melanogaster larva to gain insight into the hormonal communication possibilities of the fruit fly. Using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) and MALDI-TOF-TOF tandem mass spectrometry, we detected 23 different peptides of which five were unpredicted by previous genome screenings. We also found a hitherto unknown peptide product of the capa gene in the ring gland and transverse nerves, suggesting that it might be released as hormone. Our results show that the peptidome of the neurohaemal organs is tagma-specific and does not change during metamorphosis. We also provide evidence for the first case of differential prohormone processing in Drosophila.

Functional Screening of Serine Protease Inhibitors in the Medical Leech Hirudo medicinalis Monitored by Intensity Fading MALDI-TOF MS

The blood-feeding invertebrates are a rich biological source of drugs and lead compounds to treat cardiovascular diseases because they have evolved highly efficient mechanisms to feed on their hosts by blocking blood coagulation. In this work, we focused our attention on the leech Hirudo medicinalis. We performed, by "intensity fading" MALDI-TOF mass spectrometry, a comprehensive detection and functional analysis of pre-existent peptides and small proteins with the capability of binding to trypsin-like proteases related to blood coagulation. Combining "intensity fading MS" and off-line LC prefractionation allowed us to detect more than 75 molecules present in the leech extract that interact specifically with a trypsin-like protease over a sample profile of nearly 2,000 different peptides/proteins in the 2-20-kDa range. Moreover we resolved 232 individual components from the complex mixture, 13 of which have high sequence homology with previously described serine protease inhibitors. Our findings indicate that such extracts are much more complex than expected. Additionally, intensity fading MS, when complemented with LC separation strategies, seems to be a useful tool to investigate complex biological samples, establishing a new bridge between profiling, functional peptidomics, and subsequent drug discovery.

Development of A-type allatostatin immunoreactivity in antennal lobe neurons of the sphinx moth Manduca sexta

The antennal lobe (AL) of the sphinx moth Manduca sexta is a well-established model system for studying mechanisms of neuronal development. To understand whether neuropeptides are suited to playing a role during AL development, we have studied the cellular localization and temporal expression pattern of neuropeptides of the A-type allatostatin family. Based on morphology and developmental appearance, we distinguished four types of AST-A-immunoreactive cell types. The majority of the cells were local interneurons of the AL (type Ia) which acquired AST-A immunostaining in a complex pattern consisting of three rising (RI-RIII) and two declining phases (DI, DII). Type Ib neurons consisted of two local neurons with large cell bodies not appearing before 7/8 days after pupal ecdysis (P7/P8). Types II and III neurons accounted for single centrifugal neurons, with type II neurons present in the larva and disappearing in the early pupa. The type III neuron did not appear before P7/P8. RI and RII coincided with the rises of the ecdysteroid hemolymph titer. Artificially shifting the pupal 20-hydroxyecdysone (20E) peak to an earlier developmental time point resulted in the precocious appearance of AST-A immunostaining in types Ia, Ib, and III neurons. This result supports the hypothesis that the pupal rise in 20E plays a role in AST-A expression during AL development. Because of their early appearance in newly forming glomeruli, AST-A-immunoreactive fibers could be involved in glomerulus formation. Diffuse AST-A labeling during early AL development is discussed as a possible signal providing information for ingrowing olfactory receptor neurons.

Mass spectral signature for insect adipokinetic hormones

Insect adipokinetic hormones (AKHs) are structurally similar. They consist of 8 to 10 amino acid residues, and are post-translationally modified at the N-terminus (pyroglutamic acid) and at the C-terminus (carboxyamide). They contain aromatic amino acids at position 4 (mostly Phe, in a few cases Tyr) and at position 8 (Trp). Position 9 is always Gly which is used in the octapeptides for the amidation, and the majority of the peptides have no charge. AKHs exhibit a characteristic ion signature both in matrix-assisted laser desorption/ionization (ion pair [M+Na](+)/[M+K]+) and in electrospray mass spectrometry ([M+H+K]2+, [M-17+H]+, [M+H]+, [M+Na]+, [M+K]+). Their high affinity for Na+ and K+ alkali cations is observed even after reversed-phase purification. AKHs rarely form doubly charged ions with protons or sodium while the [M+H+K]2+ ion is often abundant suggesting a special conformation of the larger metal ion complex possibly related to its size. Here, we present analyses of several AKHs of different insect species and discuss their ionization behavior with respect to their sequence. The mass spectral signature observed is useful for AKH detection from mixtures and so an unassigned 990.7 Da molecule was found in dragonfly which is currently under investigation.

Neuropeptides associated with the frontal ganglion of larval Lepidoptera

The occurrence of neuropeptides in the frontal ganglia of larvae of the tobacco hawkmoth, Manduca sexta, the tomato moth, Lacanobia oleracea and the cotton leafworm, Spodoptera littoralis was investigated using reversed-phase high performance liquid chromatography (RP-HPLC), matrix-assisted laser desorption time of flight mass spectrometry (MALDI-TOF MS) and enzyme-linked immunosorbent assay (ELISA). Only three types of peptides could be identified or assigned from frontal ganglion extracts; M. sexta allatostatin (Manse-AS), M. sexta allatotropin (Manse-AT), and F/YXFGL-NH2 allatostatins. The peptide profiles of frontal ganglion of L. oleracea and S. littoralis were similar, with ten identical [M+H]+ ions, seven of which could be assigned to known lepidopteran peptides (Manse-AT, cydiastatin 2, 3, 4 and helicostatin 1, 5, 9). In addition, mass ions corresponding to helicostatin 7 (which was confirmed by MALDI-post source decay analysis) and Manse-AS were present in frontal ganglia of L. oleracea and helicostatin 6 in frontal ganglia of S. littoralis. Only four mass ions from M. sexta frontal ganglia corresponded to known peptides, cydiastatin 3 and 4, helicostatin 1, and Manse-AT. The only difference between the profiles of frontal ganglia from different stages of L. oleracea were mass ions which could not be assigned, and no differences were observed in the allatoregulatory peptides present. In HPLC fractions of M. sexta frontal ganglia, F/YXFGL-NH2 allatostatin-like immunoreactivity was widespread suggesting that more allatostatins were present than were identified.