Vanessa cardui adipokinetic hormone (Vanca-AKH) in butterflies and a moth

Unique Members of the Adipokinetic Hormone Family in Butterflies and Moths (Insecta, Lepidoptera)

Lepidoptera is amongst one of the four most speciose insect orders and ecologically very successful because of their ability to fly. Insect flight is always aerobic and exacts a high metabolic demand on the animal. A family of structurally related neuropeptides, generically referred to as adipokinetic hormones (AKHs), play a key role in triggering the release of readily utilizable fuel metabolites into the hemolymph from the storage forms in the fat body. We used mass spectrometry to elucidate AKH sequences from 34 species of Lepidoptera and searched the literature and publicly available databases to compile (in a phylogenetic context) a comprehensive list of all Lepidoptera sequences published/predicted from a total of 76 species. We then used the resulting set of 15 biochemically characterized AKHs in a physiological assay that measures lipid or carbohydrate mobilization in three different lepidopteran species to learn about the functional cross-activity (receptor-ligand interactions) amongst the different butterfly/moth families. Our results include novel peptide structures, demonstrate structural diversity, phylogenetic trends in peptide distribution and order-specificity of Lepidoptera AKHs. There is almost an equal occurrence of octa-, nona-, and decapeptides, with an unparalleled emphasis on nonapeptides than in any insect order. Primitive species make Peram-CAH-II, an octapeptide found also in other orders; the lepidopteran signature peptide is Manse-AKH. Not all of the 15 tested AKHs are active in Pieris brassicae; this provides insight into structure-activity specificity and could be useful for further investigations into possible biorational insecticide development.

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).

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.

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 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.

The detection of red pigment-concentrating hormone (RPCH) in crustacean eyestalk tissues using matrix-assisted laser desorption/ionization-Fourier transform mass spectrometry: [M + Na]+ ion formation in dried droplet tissue preparations

Red pigment-concentrating hormone (RPCH), an octapeptide found in crustaceans and insects with the sequence pGlu-Leu-Asn-Phe-Ser-Pro-Gly-Trp-NH2, is an N- and C-terminally blocked uncharged peptide. These structural features are shared with many members of the larger adipokinetic hormone (AKH)/RPCH peptide family in insects. We have applied vacuum UV matrix-assisted laser desorption/ionization (MALDI)-Fourier transform ion cyclotron mass spectrometry (FTMS) to the direct analysis of crustacean sinus gland tissues, using 2,5-dihydroxybenzoic acid (DHB) as the MALDI matrix, and have found that RPCH is detected in the cationized, [M + Na]+, form under conditions where other peptides in the direct tissue spectra are protonated without accompanying [M + Na]+ or [M + K]+ satellite peaks. The [M + H]+ ion for RPCH is not detected in tissue samples or for an RPCH standard, even when care is taken to eliminate metal ions. This behavior is not unprecedented; however, both direct tissue spectra and SORI-CID spectra provide no clues to suggest that the ionizing agent is a metal cation. In this communication, we characterize the MALDI-FTMS ionization and SORI-CID mass spectra of the [M + Na]+ and [M + K]+ ions from RPCH, and report on the detection of this neuropeptide in sinus gland tissues from the lobster Homarus americanus and the kelp crab Pugettia producta. We describe two strategies, an on-probe extraction procedure and a salt-doping approach, that can be applied to previously analyzed MALDI tissue samples to enhance and unmask sodiated peptides that may otherwise be mistaken for novel neuropeptides.

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.