Gene organization and expression of a neuropeptide Y homolog from the land planarian Arthurdendyus triangulatus

The neuromuscular system of the sheep tapeworm Moniezia expansa

Cestodes are common gastrointestinal parasites of humans and livestock. They attach to the host gut and, without a mouth or intestinal system, absorb nutrients through their epidermis. Here we show that despite this simplified anatomy and sessile lifestyle, they maintain a complex neuromuscular system. We used fluorescently labelled phalloidin as a specific probe for filamentous actin to define the overall organisation of several distinct muscle systems in the cyclophyllidean Moniezia expansa. Like all flatworms, the body wall musculature below the neodermis of this intestinal parasite of sheep is characterised by outer circular and inner longitudinal muscle fibres. Diagonal fibres, typically found in free-living and trematode platyhelminths, on the other hand, are notably absent. Prominent longitudinal sheaths dominate the parenchyma and provide retractor muscles to the four acetabula in the scolex; they attach at the bottom of each cup-shaped holdfast. Within sexually mature proglottids, circular fibres dominate the duct walls of the male and female reproductive systems. Nerve cells and fibres that express serotonin or neuropeptide F supply well-developed innervation to several of the described muscle systems: emanating from the central nervous system, fibres in the periphery develop pervasive nerve nets that anastomose within body wall musculature as well as the parenchymal longitudinal and oblique muscle fibres, and innervate the sexual organs and gonopore in mature proglottids. Using homology searches, we provide evidence for 20 neuropeptide precursors together with four prepropeptide processing enzymes as well as several 5-HT signalling components to be represented in the Moniezia transcriptome.

Identification, tissue distribution and orexigenic activity of neuropeptide F (NPF) in penaeid shrimp

The neuropeptide Fs (NPFs) are an invertebrate subgroup of the FMRFamide-like peptides, and are proposed by some to be the homologs of vertebrate neuropeptide Y. Although there is some information about the identity, tissue distribution and function of NPFs in insects, essentially nothing is known about them in crustaceans. We have identified and characterized NPF-encoding transcripts from the penaeid shrimp Litopenaeus vannamei and Melicertus marginatus. Two transcripts were identified from each species. For each shrimp species, the two transcripts differed from one another by the presence or absence of an insert in the portion of the open reading frame that encodes the NPF peptide. The two NPF isoforms are identical in L. vannamei and M. marginatus, with their predicted structures being KPDPSQLANMAEALKYLQELDKYYSQVSRPRFamide and KPDPSQLANMAEALKYLQELDKYYSQVSRPSPRSAPGPASQIQALENTLKFLQLQELGKLYSLRARPRFamide. RT-PCR tissue profiling showed both transcripts are broadly distributed within the nervous system of each species. The transcript encoding the shorter NPF was detected in some, but not all, midgut samples. The transcript encoding the longer NPF was absent in the midgut of both species, and neither transcript was detected in their skeletal muscle. Juvenile L. vannamei fed on a diet supplemented with the shorter NPF exhibited a marked increase in food intake relative to control individuals that did not receive the supplement; the NPF-fed shrimp also showed a significant increase in growth relative to the control group. Our data suggest that NPF is present in both the nervous system and midgut of penaeid shrimp, functioning, at least in part, as a powerful orexigenic agent.

Schistosome I/Lamides--a new family of bioactive helminth neuropeptides

Here we report the identification of a new family of helminth neuropeptides with members in both nematodes and flatworms, and include preliminary cell biological and functional characterisation of one of the peptides from the trematode parasite of humans, Schistosoma mansoni. Bioinformatics and Rapid Amplification of cDNA Ends (RACE)-PCR were used to identify the complete S. mansoni neuropeptide precursor gene Sm-npp-1, which encodes three pentapeptides bearing the motif (A/G)FVR(I/L).NH(2). Similar peptides were identified in three other flatworm species and in 15 nematode species. Quantitative PCR (qPCR) and immunocytochemical (ICC) analyses showed that Sm-npp-1 is constitutively expressed in larval and adult worms. ICC and confocal microscopy were employed to localise one of the schistosome NPP-1 peptides (GFVRIamide) in adult worms and schistosomules; antibodies labelled a pair of neurones in the cerebral ganglia that extend posteriorly along the main nerve cords. GFVRIamide displayed no detectable co-localisation with FMRFamide-like peptides (FLPs), nor was it detectable in muscle innervation. Exogenously applied peptide had a significant inhibitory effect on the mobility of whole adult worm pairs at 10(-5)M (n = 9). Finally, we explored Sm-npp-1 function in schistosomules using RNA interference (RNAi); we successfully achieved specific knockdown of the Sm-npp-1 transcript (54.46 ± 10.41% knockdown, n = 3), but did not detect any clear, aberrant mobility or morphological phenotypes. NPP-1-like peptides are a new family of helminth peptides with a cell-specific expression pattern distinct from FLPs and a modulatory effect on schistosome muscular activity.

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.

Crustacean neuroendocrine systems and their signaling agents

Decapod crustaceans have long served as important models for the study of neuroendocrine signaling. For example, the process of neurosecretion was first formally demonstrated by using a member of this order. In this review, the major decapod neuroendocrine organs are described, as are their phylogenetic conservation and neurochemistry. In addition, recent advances in crustacean neurohormone discovery and tissue mapping are discussed, as are several recent advances in our understanding of hormonal control in this group of animals.

Neuropeptide physiology in helminths

Parasitic worms come from two distinct, distant phyla, Nematoda (roundworms) and Platyhelminthes (flatworms). The nervous systems of worms from both phyla are replete with neuropeptides and there is ample physiological evidence that these neuropeptides control vital aspects of worm biology. In each phyla, the physiological evidence for critical roles for helminth neuropeptides is derived from both parasitic and free-living members. In the nematodes, the intestinal parasite Ascaris suum and the free-living Caenorhabditis elegans have yielded most of the data; in the platyhelminths, the most physiological data has come from the blood fluke Schistosoma mansoni. FMRFamide-like peptides (FLPs) have many varied effects (excitation, relaxation, or a combination) on somatic musculature, reproductive musculature, the pharynx and motor neurons in nematodes. Insulin-like peptides (INSs) play an essential role in nematode dauer formation and other developmental processes. There is also some evidence for a role in somatic muscle control for the somewhat heterogeneous grouping ofpeptides known as neuropeptide-like proteins (NLPs). In platyhelminths, as in nematodes, FLPs have a central role in somatic muscle function. Reports of FLP physiological action in platyhelminths are limited to a potent excitation of the somatic musculature. Platyhelminths are also abundantly endowed with neuropeptide Fs (NPFs), which appear absent from nematodes. There is not yet any data linking platyhelminth NPF to any particular physiological outcome, but this neuropeptide does potently and specifically inhibit cAMP accumulation in schistosomes. In nematodes and platyhelminths, there is an abundance of physiological evidence demonstrating that neuropeptides play critical roles in the biology of both free-living and parasitic helminths. While it is certainly true that there remains a great deal to learn about the biology of neuropeptides in both phyla, physiological evidence presently available points to neuropeptidergic signaling as a very promising field from which to harvest future drug targets.

Molecular characterization of neuropeptide F from the eastern subterranean termite Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae)

Neuropeptide F (NPF)-like immunoreactivity was previously found to be abundant in the eastern subterranean termite, Reticulitermes flavipes. Purification of the NPF from a whole body extract of worker termites was accomplished in the current study by HPLC and heterologous radioimmunoassay for an NPF-related peptide, Helicoverpa zea Midgut Peptide-I. A partial amino acid sequence allowed determination of the corresponding cDNA that encoded an open reading frame deduced for authentic R. flavipes NPF (Ref NPF): KPSDPEQLADTLKYLEELDRFYSQVARPRFa. Effects of synthetic NPFs on muscle contractions were investigated for isolated foreguts and hindguts of workers, with Drm NPF inhibiting spontaneous contractions of hindguts. Phylogenetic analysis of invertebrate NPF sequences reveals two separate groupings, with Ref NPF occurring within a clade composed exclusively of arthropods.

A review of FMRFamide- and RFamide-like peptides in metazoa

Neuropeptides are a diverse class of signalling molecules that are widely employed as neurotransmitters and neuromodulators in animals, both invertebrate and vertebrate. However, despite their fundamental importance to animal physiology and behaviour, they are much less well understood than the small molecule neurotransmitters. The neuropeptides are classified into families according to similarities in their peptide sequence; and on this basis, the FMRFamide and RFamide-like peptides, first discovered in molluscs, are an example of a family that is conserved throughout the animal phyla. In this review, the literature on these neuropeptides has been consolidated with a particular emphasis on allowing a comparison between data sets in phyla as diverse as coelenterates and mammals. The intention is that this focus on the structure and functional aspects of FMRFamide and RFamide-like neuropeptides will inform understanding of conserved principles and distinct properties of signalling across the animal phyla.

Discovery of multiple neuropeptide families in the phylum Platyhelminthes

Available evidence shows that short amidated neuropeptides are widespread and have important functions within the nervous systems of all flatworms (phylum Platyhelminthes) examined, and could therefore represent a starting point for new lead drug compounds with which to combat parasitic helminth infections. However, only a handful of these peptides have been characterised, the rigorous exploration of the flatworm peptide signalling repertoire having been hindered by the dearth of flatworm genomic data. Through searches of both expressed sequence tags and genomic resources using the basic local alignment search tool (BLAST), we describe 96 neuropeptides on 60 precursors from 10 flatworm species. Most of these (51 predicted peptides on 14 precursors) are novel and are apparently restricted to flatworms; the remainder comprise nine recognised peptide families including FMRFamide-like (FLPs), neuropeptide F (NPF)-like, myomodulin-like, buccalin-like and neuropeptide FF (NPFF)-like peptides; notably, the latter have only previously been reported in vertebrates. Selected peptides were localised immunocytochemically to the Schistosoma mansoni nervous system. We also describe several novel flatworm NPFs with structural features characteristic of the vertebrate neuropeptide Y (NPY) superfamily, previously unreported characteristics which support the common ancestry of flatworm NPFs with the NPY-superfamily. Our dataset provides a springboard for investigation of the functional biology and therapeutic potential of neuropeptides in flatworms, simultaneously launching flatworm neurobiology into the post-genomic era.

Effects of neuropeptide F on regeneration in Girardia tigrina (Platyhelminthes)

The effects of neuropeptide F (NPF; from Moniezia expansa) on the regeneration of Girardia tigrina were studied. The animals were decapitated and incubated in water (control) or NPF. The dynamics of the proliferation of the neoblasts in the developing tissue were studied during the course of regeneration by monitoring the mitotic index (MI). The effects of incubation in FMRFamide and GYIRFamide on the MI were also tested. The course of cephalic regeneration was followed with in vivo computer-assisted morphometry for up to 7 days. The development of the regenerating nervous system and the musculature was visualised by immunostaining with a primary antiserum to the C-terminal decapeptide of NPF (YFAIIGRPRFa) and tetramethylrhodamine-isothiocyanate-conjugated phalloidin, which stains F-actin in muscle filaments. The study showed that NPF had a stimulatory effect on the mitotic activity of the neoblasts. FMRFamide and GYIRFamide did not have this effect. NPF also stimulated the growth of the regenerating head and the growing nervous system and musculature. NPF is postulated to have a morphogenetic action in the regenerating animals.

Neuropeptide Y Y2 receptor in health and disease

We briefly survey the current knowledge and concepts regarding structure and function of the neuropeptide Y Y2 receptor and its agonists, especially as related to pharmacology of the receptor and its roles in pathological processes. Specific structural features are considered that could be responsible for the known compartmentalization and participation of the receptor in cell and tissue organization. This is further discussed in relation to changes of levels of the Y2 receptor in pathological conditions (especially in epilepsy and drug abuse), to endocytosis and recycling, and to participation in wound healing, retinopathy and angiogenesis. Properties of the receptor and of Y2 agonists are considered and reviewed in connection to the negative regulation of transmitter release, feeding, mood and social behavior. The possible involvement of the Y2 receptor in diabetes, carcinogenesis and bone formation is also reviewed.

Neuropeptide signalling systems in flatworms

Two distinct families of neuropeptides are known to endow platyhelminth nervous systems - the FMRFamide-like peptides (FLPs) and the neuropeptide Fs (NPFs). Flatworm FLPs are structurally simple, each 4-6 amino acids in length with a carboxy terminal aromatic-hydrophobic-Arg-Phe-amide motif. Thus far, four distinct flatworm FLPs have been characterized, with only one of these from a parasite. They have a widespread distribution within the central and peripheral nervous system of every flatworm examined, including neurones serving the attachment organs, the somatic musculature and the reproductive system. The only physiological role that has been identified for flatworm FLPs is myoexcitation. Flatworm NPFs are believed to be invertebrate homologues of the vertebrate neuropeptide Y (NPY) family of peptides. Flatworm NPFs are 36-39 amino acids in length and are characterized by a caboxy terminal GRPRFamide signature and conserved tyrosine residues at positions 10 and 17 from the carboxy terminal. Like FLPs, NPF occurs throughout flatworm nervous systems, although less is known about its biological role. While there is some evidence for a myoexcitatory action in cestodes and flukes, more compelling physiological data indicate that flatworm NPF inhibits cAMP levels in a manner that is characteristic of NPY action in vertebrates. The widespread expression of these neuropeptides in flatworm parasites highlights the potential of these signalling systems to yield new targets for novel anthelmintics. Although platyhelminth FLP and NPF receptors await identification, other molecules that play pivotal roles in neuropeptide signalling have been uncovered. These enzymes, involved in the biosynthesis and processing of flatworm neuropeptides, have recently been described and offer other distinct and attractive targets for therapeutic interference.

Sex- and clock-controlled expression of the neuropeptide F gene in Drosophila

Drosophila neuropeptide F (NPF), a homolog of vertebrate neuropeptide Y, functions in feeding and coordination of behavioral changes in larvae and in modulation of alcohol sensitivity in adults, suggesting diverse roles for this peptide. To gain more insight into adult-specific NPF neuronal functions, we studied how npf expression is regulated in the adult brain. Here, we report that npf expression is regulated in both sex-nonspecific and male-specific manners. Our data show that male-specific npf (ms-npf) expression is controlled by the transformer (tra)-dependent sex-determination pathway. Furthermore, fruitless, one of the major genes functioning downstream of tra, is apparently an upstream regulator of ms-npf transcription. Males lacking ms-npf expression (through tra(F)-mediated feminization) or npf-ablated male flies display significantly reduced male courtship activity, suggesting that one function of ms-npf neurons is to modulate fruitless-regulated sexual behavior. Interestingly, one of the ms-npf neuronal groups belongs to the previously defined clock-controlling dorsolateral neurons. Such ms-npf expression in the dorsolateral neurons is absent in arrhythmic Clock(Jrk) and cycle(02) mutants, suggesting that npf is under dual regulation by circadian and sex-determining factors. Based on these data, we propose that NPF also plays a role in clock-controlled sexual dimorphism in adult Drosophila.

Structure and bioactivity of neuropeptide F from the human parasites Schistosoma mansoni and Schistosoma japonicum

The blood flukes Schistosoma mansoni and Schistosoma japonicum inflict immense suffering as agents of human schistosomiasis. Previous investigations have found the nervous systems of these worms contain abundant immunoreactivity to antisera targeting invertebrate neuropeptide Fs (NPFs) as well as structurally similar neuropeptides of the mammalian neuropeptide Y (NPY) family. Here, cDNAs encoding NPF in these worms were identified, and the mature neuropeptides from the two species differed by only a single amino acid. Both neuropeptides feature the characteristics common among NPFs; they are 36 amino acids long with a carboxyl-terminal Gly-Arg-X-Arg-Phe-amide and Tyr residues at positions 10 and 17 from the carboxyl terminus. Synthetic S. mansoni NPF potently inhibits the forskolin-stimulated accumulation of cAMP in worm homogenates, with significant effects at 10(-11) m. This is the first demonstration of an endogenous inhibition of cAMP by an NPF, and because this is the predominant pathway associated with vertebrate NPY family peptides, it demonstrates a conservation of downstream signaling pathways used by NPFs and NPY peptides.

A functionally atypical amidating enzyme from the human parasite Schistosoma mansoni

Many neuropeptide transmitters require the presence of a carboxy-terminal alpha-amide group for biological activity. Amidation requires conversion of a glycine-extended peptide intermediate into a C-terminally amidated product. This post-translational modification depends on the sequential action of two enzymes (peptidylglycine alpha-hydroxylating monooxygenase or PHM, and peptidyl-alpha-hydroxyglycine alpha-amidating lyase or PAL) that in most eukaryotes are expressed as separate domains of a single protein (peptidylglycine alpha-amidating monooxygenase or PAM). We identified a cDNA encoding PHM in the human parasite Schistosoma mansoni. Transient expression of schistosome PHM (smPHM) revealed functional properties that are different from other PHM proteins; smPHM displays a lower pH-optimum and, when expressed in mammalian cells, is heavily N-glycosylated. In adult worms, PHM is found in the trans-Golgi network and secretory vesicles of both central and peripheral nerves. The widespread occurrence of PHM in the nervous system confirms the important role of amidated neuropeptides in these parasitic flatworms. The differences between schistosome and mammalian PHM suggest that it could be a target for new chemotherapeutics.

Flatworm asexual multiplication implicates stem cells and regeneration

The phenomenon of asexual multiplication is rare in the animal kingdom, but it occurs in all main flatworm taxa. In the present paper, we review data regarding the presence of different forms of asexual multiplication in flatworms and argue that the presence of a population of totipotent or pluripotent stem cells, "neoblasts", is a primitive feature of decisive importance for the developing potential of flatworms. Next we present information on the role of stem cells in fission, head regeneration, and pharynx regeneration of planarians. Furthermore, the tracing of neoblasts in lower flatworms and cestodes is presented, and the results indicating heterogeneity of the neoblast pool are discussed. Finally, the mode by which the neoblasts are stimulated to divide, migrate, and differentiate and the nature of the interactions are discussed. We focus on (i) biogenic amines and neuropeptides, (ii) the role of neuropeptides in the early stage of regeneration, (iii) the evidence for the influences of growth factors and nitric oxide, and (iv) the influence of weak electromagnetic fields. We discuss the pattern in which a gradient system of morphogens and (or) a hierarchical system of inductions is expressed in development.