Christian Wegener

A comparative review of short and long neuropeptide F signaling in invertebrates: Any similarities to vertebrate neuropeptide Y signaling?

Neuropeptides referred to as neuropeptide F (NPF) and short neuropeptide F (sNPF) have been identified in numerous invertebrate species. Sequence information has expanded tremendously due to recent genome sequencing and EST projects. Analysis of sequences of the peptides and prepropeptides strongly suggest that NPFs and sNPFs are not closely related. However, the NPFs are likely to be ancestrally related to the vertebrate family of neuropeptide Y (NPY) peptides. Peptide diversification may have been accomplished by different mechanisms in NPFs and sNPFs; in the former by gene duplications followed by diversification and in the sNPFs by internal duplications resulting in paracopies of peptides. We discuss the distribution and functions of NPFs and their receptors in several model invertebrates. Signaling with sNPF, however, has been investigated mainly in insects, especially in Drosophila. Both in invertebrates and in mammals NPF/NPY play roles in feeding, metabolism, reproduction and stress responses. Several other NPF functions have been studied in Drosophila that may be shared with mammals. In Drosophila sNPFs are widely distributed in numerous neurons of the CNS and some gut endocrines and their functions may be truly pleiotropic. Peptide distribution and experiments suggest roles of sNPF in feeding and growth, stress responses, modulation of locomotion and olfactory inputs, hormone release, as well as learning and memory. Available data indicate that NPF and sNPF signaling systems are distinct and not likely to play redundant roles.

Peptidomics of CNS-associated neurohemal systems of adult Drosophila melanogaster: A mass spectrometric survey of peptides from individual flies

Neuropeptides are important messenger molecules that influence nearly all physiological processes. In insects, they can be released as neuromodulators within the central nervous system (CNS) or as neurohormones into the hemolymph. We analyzed the peptidome of neurohormonal release sites and associated secretory peptidergic neurons of adult Drosophila melanogaster. MALDI‐TOF mass spectrometric analyzes were performed on single organs or cell cluster from individual flies. This first peptidomic characterization in adult fruit flies revealed 32 different neuropeptides. Peptides not directly predictable from previously cloned or annotated precursor genes were sequenced by tandem mass spectrometry. These peptides turned out to be either intermediate products of neuropeptide processing or shorter versions of known peptides. We found that the peptidome of the CNS‐associated neurohemal organs is tagma‐specific in Drosophila. Abdominal neurohemal organs and their supplying peptidergic neurons contain the capa gene products periviscerokinins and pyrokinin‐1, thoracic neurohemal organs contain FMRFamides, and the neurohemal release sites of the brain contain pyrokinin‐12‐15, pyrokinin‐2, corazonin, myosuppressin, and sNPF as their major putative release products. Our results show that peptidomic approaches are well suited to study differential neuropeptide expression or posttranslational modifications in morphologically defined parts of the nervous system and in a developmental and physiological context in animals as small as Drosophila melanogaster. J. Comp. Neurol. 474:379–392, 2004.

Biology of the CAPA peptides in insects

Abstract.CAPA peptides have been isolated from a broad range of insect species as well as an arachnid, and can be grouped into the periviscerokinin and pyrokinin peptide families. In insects, CAPA peptides are the characteristic and most abundant neuropeptides in the abdominal neurohemal system. In many species, CAPA peptides exert potent myotropic effects on different muscles such as the heart. In others, including blood-sucking insects able to transmit serious diseases, CAPA peptides have strong diuretic or anti-diuretic effects and thus are potentially of medical importance. CAPA peptides undergo cell-type-specific sorting and packaging, and are the first insect neuropeptides shown to be differentially processed. In this review, we discuss the current knowledge on the structure, distribution, receptors and physiological actions of the CAPA peptides.

A large population of diverse neurons in the Drosophila central nervous system expresses short neuropeptide F, suggesting multiple distributed peptide functions

BackgroundInsect neuropeptides are distributed in stereotypic sets of neurons that commonly constitute a small fraction of the total number of neurons. However, some neuropeptide genes are expressed in larger numbers of neurons of diverse types suggesting that they are involved in a greater diversity of functions. One of these widely expressed genes, snpf, encodes the precursor of short neuropeptide F (sNPF). To unravel possible functional diversity we have mapped the distribution of transcript of the snpf gene and its peptide products in the central nervous system (CNS) of Drosophila in relation to other neuronal markers.ResultsThere are several hundreds of neurons in the larval CNS and several thousands in the adult Drosophila brain expressing snpf transcript and sNPF peptide. Most of these neurons are intrinsic interneurons of the mushroom bodies. Additionally, sNPF is expressed in numerous small interneurons of the CNS, olfactory receptor neurons (ORNs) of the antennae, and in a small set of possibly neurosecretory cells innervating the corpora cardiaca and aorta. A sNPF-Gal4 line confirms most of the expression pattern. None of the sNPF immunoreactive neurons co-express a marker for the transcription factor DIMMED, suggesting that the majority are not neurosecretory cells or large interneurons involved in episodic bulk transmission. Instead a portion of the sNPF producing neurons co-express markers for classical neurotransmitters such as acetylcholine, GABA and glutamate, suggesting that sNPF is a co-transmitter or local neuromodulator in ORNs and many interneurons. Interestingly, sNPF is coexpressed both with presumed excitatory and inhibitory neurotransmitters. A few sNPF expressing neurons in the brain colocalize the peptide corazonin and a pair of dorsal neurons in the first abdominal neuromere coexpresses sNPF and insulin-like peptide 7 (ILP7).ConclusionIt is likely that sNPF has multiple functions as neurohormone as well as local neuromodulator/co-transmitter in various CNS circuits, including olfactory circuits both at the level of the first synapse and at the mushroom body output level. Some of the sNPF immunoreactive axons terminate in close proximity to neurosecretory cells producing ILPs and adipokinetic hormone, indicating that sNPF also might regulate hormone production or release.

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.

Neuroarchitecture of Aminergic Systems in the Larval Ventral Ganglion of Drosophila melanogaster

Biogenic amines are important signaling molecules in the central nervous system of both vertebrates and invertebrates. In the fruit fly Drosophila melanogaster, biogenic amines take part in the regulation of various vital physiological processes such as feeding, learning/memory, locomotion, sexual behavior, and sleep/arousal. Consequently, several morphological studies have analyzed the distribution of aminergic neurons in the CNS. Previous descriptions, however, did not determine the exact spatial location of aminergic neurite arborizations within the neuropil. The release sites and pre-/postsynaptic compartments of aminergic neurons also remained largely unidentified. We here used gal4-driven marker gene expression and immunocytochemistry to map presumed serotonergic (5-HT), dopaminergic, and tyraminergic/octopaminergic neurons in the thoracic and abdominal neuromeres of the Drosophila larval ventral ganglion relying on Fasciclin2-immunoreactive tracts as three-dimensional landmarks. With tyrosine hydroxylase- (TH) or tyrosine decarboxylase 2 (TDC2)-specific gal4-drivers, we also analyzed the distribution of ectopically expressed neuronal compartment markers in presumptive dopaminergic TH and tyraminergic/octopaminergic TDC2 neurons, respectively. Our results suggest that thoracic and abdominal 5-HT and TH neurons are exclusively interneurons whereas most TDC2 neurons are efferent. 5-HT and TH neurons are ideally positioned to integrate sensory information and to modulate neuronal transmission within the ventral ganglion, while most TDC2 neurons appear to act peripherally. In contrast to 5-HT neurons, TH and TDC2 neurons each comprise morphologically different neuron subsets with separated in- and output compartments in specific neuropil regions. The three-dimensional mapping of aminergic neurons now facilitates the identification of neuronal network contacts and co-localized signaling molecules, as exemplified for DOPA decarboxylase-synthesizing neurons that co-express crustacean cardioactive peptide and myoinhibiting peptides.

Peptidomics and Peptide Hormone Processing in the Drosophila Midgut

Peptide hormones are key messengers in the signaling network between the nervous system, endocrine glands, energy stores and the gastrointestinal tract that regulates feeding and metabolism. Studies on the Drosophila nervous system have uncovered parallels and homologies in homeostatic peptidergic signaling between fruit flies and vertebrates. Yet, the role of enteroendocrine peptides in the regulation of feeding and metabolism has not been explored, with research hampered by the unknown identity of peptides produced by the flys intestinal tract. We performed a peptidomic LC/MS analysis of the fruit fly midgut containing the enteroendocrine cells. By MS/MS fragmentation, we found 24 peptides from 9 different preprohormones in midgut extracts, including MIP-4 and 2 forms of AST-C. DH(31), CCHamide1 and CCHamide2 are biochemically characterized for the first time. All enteroendocrine peptides represent brain-gut peptides, and apparently are processed by Drosophila prohormone convertase 2 (AMON) as suggested by impaired peptide detectability in amon mutants and localization of amon-driven GFP to enteroendocrine cells. Because of its genetic amenability and peptide diversity, Drosophila provides a good model system to study peptide signaling. The identification of enteroendocrine peptides in the fruit fly provides a platform to address functions of gut peptide hormones in the regulation of feeding and metabolism.

Molecular evolution of neuropeptides in the genus Drosophila

BackgroundNeuropeptides comprise the most diverse group of neuronal signaling molecules. They often occur as multiple sequence-related copies within single precursors (the prepropeptides). These multiple sequence-related copies have not arisen by gene duplication, and it is debated whether they are mutually redundant or serve specific functions. The fully sequenced genomes of 12 Drosophila species provide a unique opportunity to study the molecular evolution of neuropeptides.ResultsWe data-mined the 12 Drosophila genomes for homologs of neuropeptide genes identified in Drosophila melanogaster. We then predicted peptide precursors and the neuropeptidome, and biochemically identified about half of the predicted peptides by direct mass spectrometric profiling of neuroendocrine tissue in four species covering main phylogenetic lines of Drosophila. We found that all species have an identical neuropeptidome and peptide hormone complement. Calculation of amino acid distances showed that ortholog peptide copies are highly sequence-conserved between species, whereas the observed sequence variability between peptide copies within single precursors must have occurred prior to the divergence of the Drosophila species.ConclusionWe provide a first genomic and chemical characterization of fruit fly neuropeptides outside D. melanogaster. Our results suggest that neuropeptides including multiple peptide copies are under stabilizing selection, which suggests that multiple peptide copies are functionally important and not dispensable. The last common ancestor of Drosophila obviously had a set of neuropeptides and peptide hormones identical to that of modern fruit flies. This is remarkable, since drosophilid flies have adapted to very different environments.

The periviscerokinin (PVK) peptide family in insects: evidence for the inclusion of CAP2b as a PVK family member

Periviscerokinins (PVKs) are a distinct insect peptide family with unusual distribution in the central nervous system and neurohemal release sites. PVKs were first isolated from the abdominal perisympathetic organs of Periplaneta americana, but can be found in other insect species. Peptides with structural similarity to PVKs have been identified through searches of the Drosophila genome. The cardioacceleratory peptide CAP(2b) of the hawkmoth Manduca sexta shares close amino acid identity with the PVKs and may thus be included as a structural member of the PVK peptide family. In this review, we provide support for grouping CAP(2b) as a PVK family member based on published sequences, and new immunocytochemical findings and mass spectrometric data.

Unique features of a global human ectoparasite identified through sequencing of the bed bug genome

The bed bug, Cimex lectularius, has re-established itself as a ubiquitous human ectoparasite throughout much of the world during the past two decades. This global resurgence is likely linked to increased international travel and commerce in addition to widespread insecticide resistance. Analyses of the C. lectularius sequenced genome (650 Mb) and 14,220 predicted protein-coding genes provide a comprehensive representation of genes that are linked to traumatic insemination, a reduced chemosensory repertoire of genes related to obligate hematophagy, host–symbiont interactions, and several mechanisms of insecticide resistance. In addition, we document the presence of multiple putative lateral gene transfer events. Genome sequencing and annotation establish a solid foundation for future research on mechanisms of insecticide resistance, human–bed bug and symbiont–bed bug associations, and unique features of bed bug biology that contribute to the unprecedented success of C. lectularius as a human ectoparasite.