NPY-like peptides occur in the nervous system and midgut of the migratory locust, Locusta migratoria and in the brain of the grey fleshfly, Sarcophaga bullata

A combined strategy of neuropeptide prediction and tandem mass spectrometry identifies evolutionarily conserved ancient neuropeptides in the sea anemone Nematostella vectensis

Neuropeptides are a class of bioactive peptides shown to be involved in various physiological processes, including metabolism, development, and reproduction. Although neuropeptide candidates have been predicted from genomic and transcriptomic data, comprehensive characterization of neuropeptide repertoires remains a challenge owing to their small size and variable sequences. De novo prediction of neuropeptides from genome or transcriptome data is difficult and usually only efficient for those peptides that have identified orthologs in other animal species. Recent peptidomics technology has enabled systematic structural identification of neuropeptides by using the combination of liquid chromatography and tandem mass spectrometry. However, reliable identification of naturally occurring peptides using a conventional tandem mass spectrometry approach, scanning spectra against a protein database, remains difficult because a large search space must be scanned due to the absence of a cleavage enzyme specification. We developed a pipeline consisting of in silico prediction of candidate neuropeptides followed by peptide-spectrum matching. This approach enables highly sensitive and reliable neuropeptide identification, as the search space for peptide-spectrum matching is highly reduced. Nematostella vectensis is a basal eumetazoan with one of the most ancient nervous systems. We scanned the Nematostella protein database for sequences displaying structural hallmarks typical of eumetazoan neuropeptide precursors, including amino- and carboxyterminal motifs and associated modifications. Peptide-spectrum matching was performed against a dataset of peptides that are cleaved in silico from these putative peptide precursors. The dozens of newly identified neuropeptides display structural similarities to bilaterian neuropeptides including tachykinin, myoinhibitory peptide, and neuromedin-U/pyrokinin, suggesting these neuropeptides occurred in the eumetazoan ancestor of all animal species.

Neuropeptide F regulates male reproductive processes in the desert locust, Schistocerca gregaria

Although Neuropeptide F (NPF) has been identified in different insect species, its function has mainly been studied in the fruit fly, Drosophila melanogaster, where it regulates diverse physiological processes, such as learning, stress responses and male courtship behavior. In locusts, only a truncated form of the "full-length" NPF (the biologically active "trNPF") has been isolated. This 9 AA peptide stimulates oocyte maturation, food intake and weight increase in adult desert locusts (Schistocerca gregaria [Forskål]). In this study, we investigated whether this peptide is also involved in the regulation of male reproductive physiology in this orthopteran species. Daily injections of trNPF in adult males resulted in proportionally heavier testes and seminal vesicles, while RNAi-mediated knockdown of the Schgr-NPF precursor transcript gave rise to proportionally lighter testes and seminal vesicles. Furthermore, adult males precociously displayed courtship behavior when injected daily with trNPF, while this behavior was inhibited or delayed by RNAi knockdown of the Schgr-NPF precursor transcript. In order to further analyze these effects of trNPF on male reproductive physiology, fertility of males was tested by analyzing progeny numbers following copulation with untreated females. In this way, we showed that daily trNPF injection in adult males resulted in a larger egg pod size and a higher percentage of hatched eggs per egg pod after copulation, while RNAi knockdown caused the opposite effects. Taken together, we provide clear evidence for a role of trNPF in the regulation of reproductive physiology in adult males of the desert locust, S. gregaria. Possible modes of action of trNPF in influencing these reproductive processes in male locusts are discussed.

Regulation of feeding by Neuropeptide F in the desert locust, Schistocerca gregaria

Our knowledge on the physiological function of the insect Neuropeptide F (NPF) mostly comes from studies in the fruit fly, Drosophila melanogaster, where NPF was shown to regulate diverse processes, such as feeding, learning and responding to stress. In the desert locust, Schistocerca gregaria, only a truncated form of the "full-length" NPF (the biologically active "trNPF") has been isolated. In this study, we investigated whether this peptide is involved in the regulation of feeding in this orthopteran species. In the S. gregaria EST-database, an NPF-precursor encoding transcript was found. Alignment with other insect NPF-precursors showed relatively highest sequence conservation within the trNPF region (and the flanking dibasic cleavage site), as compared to other regions of the NPF-precursor. Quantitative real-time RT-PCR revealed that the Schgr-NPF-precursor encoding transcript occurs throughout the central nervous system with relatively high transcript levels in the brain, optic lobes and suboesophageal ganglion. It was also detected at relatively high levels in the midgut, which suggests that the encoded peptide also functions in the digestive system. Moreover, Schgr-NPF-transcript levels were notably higher in starved animals than in animals fed ad libitum, while transcript levels were also shown to be regulated after the consumption of a meal. Injection of locust trNPF in adults stimulated food intake, while RNAi knockdown reduced food intake. Furthermore, injection of trNPF in adults stimulated weight increase, while RNAi knockdown reduced weight gain. This effect of trNPF on body weight gain may result from its stimulatory effect on food intake. Taken together, we provide clear evidence for an important role of trNPF in the regulation of feeding in the desert locust, S. gregaria.

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.

Obese carboxypeptidase E knockout mice exhibit multiple defects in peptide hormone processing contributing to low bone mineral density

Carboxypeptidase E (CPE) is a prohormone/proneuropeptide processing enzyme, and mice bearing CPE mutations exhibit an obese and diabetic phenotype. Studies on CPE knockout (KO) mice revealed poor prohormone processing, resulting in deficiencies in peptide hormones/neuropeptides such as insulin, gonadotropin-releasing hormone, and cocaine- and amphetamine-regulated transcript (CART). Here, we show that CPE KO mice, an obese animal model, have low bone mineral density (BMD) accompanied by elevated plasma CTX-1 (carboxy-terminal collagen crosslinks), and osteocalcin, indicators of increased bone turnover. Receptor activator for NF-kappaB ligand (RANKL) expression was elevated approximately 2-fold relative to osteoprotegerin in the femur of KO animals, suggesting increased osteoclastic activity in the KO mice. In the hypothalamus, mature CART, a peptide involved in eating behavior and implicated in bone metabolism, was undetectable. The melanocortin and neuropeptide Y (NPY) systems in the hypothalamus have also been implicated in bone remodeling, since MC4R KO and NPY KO mice have increased BMD. However, reduction of alpha-MSH, the primary ligand of MC4R by up to 94% and the lack of detectable NPY in the hypothalamus of CPE KO do not recapitulate the single-gene KO phenotypes. This study highlights the complex physiological interplay between peptides involved in energy metabolism and bone formation and furthermore suggests the possibility that patients, bearing CPE and CART mutations leading to inactive forms of these molecules, may be at a higher risk of developing osteoporosis.

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.

Identification of new members of the (short) neuropeptide F family in locusts and Caenorhabditis elegans

Both the long and short neuropeptides F (NPF) represent important families of invertebrate neuropeptides that have been implicated in the regulation of reproduction and feeding behavior. In the present study, two short NPFs (SNRSPS(L/I)R(L/I)RFamide and SPS(L/I)R(L/I)RFamide) were de novo sequenced by mass spectrometry in two major pest insects, the desert locust Schistocerca gregaria and the African migratory locust Locusta migratoria. They are two of the most widespread peptides in the locust neuroendocrine system. A peptide that was previously reported to accelerate egg development in S. gregaria is shown to represent a truncated form of long NPF. This peptide is most likely derived by a novel processing mechanism involving cleavage at RY. In addition, an NPF peptide from the nematode Caenorhabditis elegans was isolated and sequenced by tandem mass spectrometry.

Mass spectrometric identification of pEGFYSQRYamide: a crustacean peptide hormone possessing a vertebrate neuropeptide Y (NPY)-like carboxy-terminus

In invertebrates, peptides possessing the carboxy (C)-terminal motif -RXRFamide have been proposed as the homologs of vertebrate neuropeptide Y (NPY). Using matrix assisted laser desorption/ionization mass spectrometry, in combination with sustained off-resonance irradiation collision-induced dissociation and chemical and enzymatic reactions, we have identified the peptide pEGFYSQRYamide from the neuroendocrine pericardial organ (PO) of the crab Pugettia producta. This peptide is likely the same as that previously reported, but misidentified, as PAFYSQRYamide in several earlier reports (e.g. [Li, L., Kelley, W.P., Billimoria, C.P., Christie, A.E., Pulver, S.R., Sweedler, J.V., Marder, E. 2003. Mass spectrometric investigation of the neuropeptide complement and release in the pericardial organs of the crab, Cancer borealis. J. Neurochem. 87, 642-656; Fu, Q., Kutz, K.K., Schmidt, J.J., Hsu, Y.W., Messinger, D.I., Cain, S.D., de la Iglesia, H.O., Christie, A.E., Li, L. 2005. Hormone complement of the Cancer productus sinus gland and pericardial organ: an anatomical and mass spectrometric investigation. J. Comp. Neurol. 493, 607-626.]). The -QRYamide motif contained in pEGFYSQRYamide is identical to that present in many vertebrate members of the NPY superfamily. Mass spectrometric analysis conducted on the POs of several other decapods showed that pEGFYSQRYamide is present in three other brachyurans (Cancer borealis, Cancer irroratus and Cancer productus) as well as in one species from another decapod infraorder (Lithodes maja, an anomuran). Thus, our findings show that at least some invertebrates possess NPY-like peptides in addition to those exhibiting an -RXRFamide C-terminus, and raise the question as to whether the invertebrate -QRYamides are functionally and/or evolutionarily related to the NPY superfamily.

Characterization of neuropeptide F and its receptor from the African malaria mosquito, Anopheles gambiae

The genome of Anopheles gambiae contains sequences encoding a neuropeptide F (Ang-NPF) and NPF receptor (Ang-NPFR) related to the neuropeptide Y signaling family. cDNAs for each were cloned and sequenced. Ang-NPFR was stably expressed for radioligand binding analysis. Ang-NPF exhibited high affinity (IC50 approximately 3 nM) membrane binding; NPFs from Aedes aegypti (Aea-NPF) and Drosophila melanogaster (Drm-NPF) were less potent, with the rank order: Ang-NPF>Aea-NPF>Drm-NPF>Drm-NPF8-36. RT-PCR analysis revealed Ang-NPF and Ang-NPFR transcripts in all life stages. Ang-NPF and Ang-NPFR may be strategically positioned for signaling in relation to nutritional status in the African malaria mosquito.

The activation of G-protein gated inwardly rectifying K+ channels by a cloned Drosophila melanogaster neuropeptide F-like receptor

A Drosophila melanogaster G-protein-coupled receptor (NPFR76F) that is activated by neuropeptide F-like peptides has been expressed in Xenopus oocytes to determine its ability to regulate heterologously expressed G-protein-coupled inwardly rectifying potassium channels. The activated receptor produced inwardly rectifying potassium currents by a pertussis toxin-sensitive G-protein-mediated pathway and the effects were reduced in the presence of proteins, such as the betaARK 1 carboxy-tail fragment and alpha-transducin, which bind G-protein betagamma-subunits. Short Drosophila NPF-like peptides were more potent than long NPF-like peptides at coupling the receptor to the activation of inwardly rectifying potassium channels. The putative endogenous short Drosophila NPF-like peptides showed agonist-specific coupling depending on whether their actions were assessed as the activation of the inwardly rectifying potassium channels or as the activation of endogenous inward chloride channels through a co-expressed promiscuous G-protein, Galpha16. As inwardly rectifying potassium channels are known to be encoded in the Drosophila genome and the NPFR76F receptor is widely expressed in the Drosophila nervous system, the receptor could function to control neuronal excitability or slow wave potential generation in the Drosophila nervous system.

Functional characterization of a neuropeptide F-like receptor from Drosophila melanogaster

A cDNA clone encoding a seven-transmembrane domain, G-protein-coupled receptor (NPFR76F, also called GPCR60), has been isolated from Drosophila melanogaster. Deletion mapping showed that the gene encoding this receptor is located on the left arm of the third chromosome at position 76F. Northern blotting and whole mount in situ hybridization have shown that this receptor is expressed in a limited number of neurons in the central and peripheral nervous systems of embryos and adults. Analysis of the deduced amino acid sequence suggests that this receptor is related to vertebrate neuropeptide Y receptors. This Drosophila receptor shows 62-66% similarity and 32-34% identity to type 2 neuropeptide Y receptors cloned from a variety of vertebrate sources. Coexpression in Xenopus oocytes of NPFR76F with the promiscuous G-protein Galpha16 showed that this receptor is activated by the vertebrate neuropeptide Y family to produce inward currents due to the activation of an endogenous oocyte calcium-dependent chloride current. Maximum receptor activation was achieved with short, putative Drosophila neuropeptide F peptides (Drm-sNPF-1, 2 and 2s). Neuropeptide F-like peptides in Drosophila have been implicated in a signalling system that modulates food response and social behaviour. The identification of this neuropeptide F-like receptor and its endogenous ligand by reverse pharmacology will facilitate genetic and behavioural studies of neuropeptide functions in Drosophila.

Characterization of the short neuropeptide F receptor from Drosophila melanogaster

A seven transmembrane G-protein coupled receptor has been cloned from Drosophila melanogaster. This receptor shows structural similarities to vertebrate Neuropeptide Y(2) receptors and is activated by endogenous Drosophila peptides, recently designated as short neuropeptide Fs (sNPFs). sNPFs have so far been found in neuroendocrine tissues of four other insect species and of the horseshoe crab. In locusts, they accelerate ovarian maturation, and in mosquitoes, they inhibit host-seeking behavior. Expression analysis by RT-PCR shows that the sNPF receptor (Drm-sNPF-R) is present in several tissues (brain, gut, Malpighian tubules and fat body) from Drosophila larvae as well as in ovaries of adult females. All 4 Drosophila sNPFs clearly elicited a calcium response in receptor expressing mammalian Chinese hamster ovary cells. The response is dose-dependent and appeared to be very specific. The short NPF receptor was not activated by any of the other tested arthropod peptides, not even by FMRFamide-related peptides (also ending in RFamide), indicating that the Arg residue at position 4 from the amidated C-terminus appears to be crucial for the response elicited by the sNPFs.

Neuropeptides in the nervous system of Drosophila and other insects: multiple roles as neuromodulators and neurohormones

Neuropeptides in insects act as neuromodulators in the central and peripheral nervous system and as regulatory hormones released into the circulation. The functional roles of insect neuropeptides encompass regulation of homeostasis, organization of behaviors, initiation and coordination of developmental processes and modulation of neuronal and muscular activity. With the completion of the sequencing of the Drosophila genome we have obtained a fairly good estimate of the total number of genes encoding neuropeptide precursors and thus the total number of neuropeptides in an insect. At present there are 23 identified genes that encode predicted neuropeptides and an additional seven encoding insulin-like peptides in Drosophila. Since the number of G-protein-coupled neuropeptide receptors in Drosophila is estimated to be around 40, the total number of neuropeptide genes in this insect will probably not exceed three dozen. The neuropeptides can be grouped into families, and it is suggested here that related peptides encoded on a Drosophila gene constitute a family and that peptides from related genes (orthologs) in other species belong to the same family. Some peptides are encoded as multiple related isoforms on a precursor and it is possible that many of these isoforms are functionally redundant. The distribution and possible functions of members of the 23 neuropeptide families and the insulin-like peptides are discussed. It is clear that each of the distinct neuropeptides are present in specific small sets of neurons and/or neurosecretory cells and in some cases in cells of the intestine or certain peripheral sites. The distribution patterns vary extensively between types of neuropeptides. Another feature emerging for many insect neuropeptides is that they appear to be multifunctional. One and the same peptide may act both in the CNS and as a circulating hormone and play different functional roles at different central and peripheral targets. A neuropeptide can, for instance, act as a coreleased signal that modulates the action of a classical transmitter and the peptide action depends on the cotransmitter and the specific circuit where it is released. Some peptides, however, may work as molecular switches and trigger specific global responses at a given time. Drosophila, in spite of its small size, is now emerging as a very favorable organism for the studies of neuropeptide function due to the arsenal of molecular genetics methods available.

Newly discovered functions for some myotropic neuropeptides in locusts

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

Identification of a Drosophila brain-gut peptide related to the neuropeptide Y family

A neuropeptide F (NPF) was isolated from the fruit fly, Drosophila mellanogaster, based on a radioimmunoassay for a gut peptide from the corn earworm, Helicoverpa zea. A partial sequence was obtained from the fly peptide, and a genomic sequence coding for NPF was cloned after inverse polymerase chain reaction and shown to exist as a single genomic copy. The encoded, putative prepropeptide can be processed into an amidated NPF with 36 residues that is related to invertebrate NPF's and the neuropeptide Y family of vertebrates. In situ hybridization and immunocytochemistry showed that Drosophila NPF was expressed in the brain and midgut of fly larvae and adults.

The distribution and myotropic activity of locustatachykinin-like peptides in locust midgut

The midgut of the African migratory locust, Locusta migratoria, was found to contain endocrine-like cells that stained positively for locustatachykinin I (Lom TK I)-like immunoreactivity. These cells were distributed in an unequal manner throughout the midgut of the locust, with a greater density of Lom TK I-like immunoreactive endocrine-like cells occurring in the posterior region of the midgut. These singly occurring cells appear elongate with an apical extension projecting toward the midgut lumen and a smaller projection extending towards the midgut basal lamina. No immunoreactive neuronal processes were detected along the midgut wall. Radioimmunoassays revealed that the female midgut contained two to three times more Lom TK I-like material than the male midgut, and radioimmunoassay coupled to high-performance liquid chromatography analysis revealed that at least five locustatachykinin isoforms appear to be present in the midgut. This distribution of Lom TK I-like material suggests possible functional differences in the various regions of the midgut. The role that these cells may play in locust midgut secretory activity and motility remains unknown. However, the addition of synthetic Lom TK I through IV to a ring type midgut muscle preparation stimulated contraction of midgut circular muscles, suggesting a possible physiological role for these peptides. Dose-response curves constructed for Lom TK I-IV revealed that the peptide-induced contractions increased in a dose-dependent manner.

Led-NPF-1 stimulates ovarian development in locusts

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

Insect neuropeptide F (NPF)-related peptides: isolation from Colorado potato beetle (Leptinotarsa decemlineata) brain

Two novel neuropeptides with neuropeptide F (NPF)-like immunoreactivity have been isolated from brain extracts of the Colorado potato beetle. Purification was achieved primarily by use of reverse phase chromatography including initial C-18 Sep-Pak cartridges and 4 subsequent analytical HPLC columns. Combined data from automated Edman degradation, immunochemical analysis, u.v. absorbance and mass spectrometry led to the elucidation of their full primary structures. The deduced sequences are: Ala-Arg-Gly-Pro-Gln-Leu-Arg-Leu-Arg-Phe-NH2 (ARGPQLRLRFamide) and Ala-Pro-Ser-Leu-Arg-Leu-Arg-Phe-NH2 (APSLRLRFamide). On the basis of their primary structure both peptides can be appended to the invertebrate group of neuropeptide Y (NPY)-like peptides, generally referred to as NPFs. We suggest these peptides to be designated Led-NPF-1 and Led-NPF-2.

Isolation of NEB-LFamide, a novel myotropic neuropeptide from the grey fleshfly

A methanolic extract of 350,000 adult grey fleshflies Neobellieria bullata, was prepared and screened for myotropic activity. After fractionation on the first column, all fractions were screened in two heterologous (Locusta oviduct and Leucophaea hindgut) and one homologous (Neobellieria hindgut) myotropic bioassay. We here report the purification of one fraction, which stimulates the contractions of the Locusta oviduct. Electrospray Mass Spectrometry of the peptide revealed a molecular mass of 1395.82. The primary structure has been determined as AYRKPPFNGSLF-amide. This novel peptide was designated Neb-LF-amide. This sequence is different from the other known myotropic peptides in insects. The threshold concentration of the synthetic peptide is 1 x 10(-7) M on the Locusta oviduct. On the hindgut of Neobellieria or Leucophaea, the synthetic peptide is not active. By use of a polyclonal antiserum raised against the synthetic peptide, immunoreactivity was localized in median neurosecretory cells in the pars intercerebralis of the fly brain, indicating that Neb-LF-amide is a neuropeptide.

Isolation and identification of a cAMP generating peptide from the flesh fly, Neobellieria bullata (Diptera: Sarcophagidae)

The Manduca sexta Malpighian tubule assay system, developed to monitor adenylate cyclase activity, was used in combination with HPLC to isolate a novel cAMP generating peptide from 350,000 whole flesh flies, Neobellieria bullata. Mass spectrometry revealed a molecular mass of 5,047 daltons, and Edman degradation the following sequence: AGAEAEKLSGLSKYFNGTTMAGRANVAKATYAVIGLIIAYNVMKPKKK. This 48-mer peptide, called Neb-cGP, does not belong to the corticotropin releasing factor family of insect diuretic peptides. Electrophoresis and subsequent immunoblotting of peptides immunoprecipitated from a homogenate of entire flies showed that one fly contained approximately 0.003 to 0.03 micrograms Neb-cGP and that 10 micrograms represents the lowest immunostainable amount on a Western blot.

Neuropeptide tyrosine in the brain of the African lungfish, Protopterus annectens: immunohistochemical localization and biochemical characterization

Lungfishes, which share similarities with both fishes and amphibians, represent an interesting group in which to investigate the evolutionary transition from fishes to tetrapods. In the present study, we have investigated the localization and biochemical characteristics of neuropeptide Y (NPY)-immunoreactive material in the central nervous system of the African lungfish, Protopterus annectens. NPY-immunoreactive cell bodies were found in various regions of the brain, most notably in the telencephalon (septal area, ventral striatum, and nucleus accumbens), in the diencephalon (preoptic nucleus, periventricular region of the hypothalamus, and ventral thalamus), and in the tegmentum of the mesencephalon. A strong immunoreaction was also detected in cell bodies of the nervus terminalis. Immunoreactive nerve fibers were particularly abundant in the ventral striatum, the nucleus accumbens, the diagonal band of Broca, the hypothalamus, and the mesencephalic tegmentum. Positive fibers were also seen in the median eminence and in the neural lobe of the pituitary. The NPY-immunoreactive material localized in the brain and pituitary was characterized by combining high-performance liquid chromatography (HPLC) analysis and radioimmunological quantitation. The displacement curves obtained with synthetic porcine and frog NPY and serial dilutions of brain and pituitary extracts were parallel. Reversed-phase HPLC analysis of telencephalon, diencephalon, and pituitary extracts resolved a major NPY-immunoreactive peak that coeluted with frog NPY. The similarity between the distribution of NPY-containing neurons and the biochemical characteristics of the immunoreactive peptide in the brain of lungfish and frog strongly favors a close phylogenetic relationship between dipnoans and amphibians.

Locustatachykinin immunoreactivity in the blowfly central nervous system and intestine

An antiserum raised against locustatachykinin I, one of four myotropic peptides that have been isolated from the locust brain and corpora cardiaca, was characterized by enzyme-linked immunosorbent assay (ELISA) and used for immunocytochemical detection of neurons and endocrine cells in the nervous system and intestine of the blowfly Calliphora vomitoria. The ELISA characterization indicated that the antiserum recognizes the common C-terminus sequence of the locustatachykinins I-III. Hence, the cross reaction with locustatachykinin IV is less, and in competitive ELISAs no cross reaction was detected with a series of vertebrate tachykinins tested. It was also shown that the antiserum recognized material in extracts of blowfly heads, as measured in ELISA. In high-performance liquid chromatography the extracted locustatachykinin-like immunoreactive (LomTK-LI) material eluted in two different ranges. A fairly large number of LomTK-LI neurons was detected in the blowfly brain and thoracicoabdominal ganglion. A total of about 160 LomTK-LI neurons was seen in the proto-, deuto-, and tritocerebrum and subesophageal ganglion. Immunoreactive processes from these neurons could be traced in many neuropil regions of the brain: superior and dorsomedian protocerebrum, optic tubercle, fan-shaped body and ventral bodies of the central complex, all the glomeruli of the antennal lobes, and tritocerebral and subesophageal neuropil. No immunoreactivity was seen in the mushroom bodies or the optic lobes. In the fused thoracicoabdominal ganglion, 46 LomTK-LI neurons could be resolved. The less evolved larval nervous system was also investigated to obtain additional information on the morphology and projections of immunoreactive neurons. In neither the larval nor the adult nervous systems could we identify any efferent or afferent immunoreactive axons or neurosecretory cells. The widespread distribution of LomTK-LI material in interneurons suggests an important role of the native peptide(s) as a neurotransmitter or neuromodulator within the central nervous system. Additionally a regulatory function in the intestine is indicated by the presence of immunoreactivity in endocrine cells of the midgut.

Neurotensin-like immunoreactivity in locust supraesophageal ganglion and optic lobes

A substance immunoreactive to antibodies directed against bovine neurotensin (NT) was localized in neurons in the supraesophageal ganglion (SEG) and optic lobes of larval and adult Locusta migratoria L. Two large somata were located in the caudal cortex, ventral to the calyces and symmetrical to the median of the SEG. Four smaller somata also in the caudal cortex were located as two symmetrical pairs at the level of the central body. These somata formed a diffuse network of varicose fibers from the superior lateral to the ventro-lateral protocerebrum between the pedunculi and frontal cortical region. Some fibers crossed the median to the contralateral sides of the SEG. Another pair of immunoreactive somata whose terminating processes remained unclear was found at the level of the antennal lobes. Intrinsic networks of fibers were labeled in the accessory medulla and in layer 4/5 of the medulla. These fibers originated from 8-10 small somata near the dorso-frontal rim of the medulla. All larval stages contained these NT-like immunoreactive structures. Results from isoelectric focusing and press-blot analysis of SEG homogenates, synthetic neurotensin and neurotensin fragments indicate that this substance is similar to bovine neurotensin(1-13).

Neuropeptide Y-like immunoreactivity in the dogfish gastroenteropancreatic tract: light and electron microscopical study

The 36 amino acid neuropeptide Y (NPY) has been examined in mammals and is mainly located in the nerves. Its distribution in nonmammalian vertebrate and in some invertebrate nervous systems has been confirmed. Using antisera raised to porcine NPY, NPY immunoreactivity has been localized in endocrine cells of the pancreas and gastrointestinal tract of two dogfish, Scyliorhinus stellaris and Scyliorhinus canicula. Immunostained serial sections and cross-absorption experiments with related peptides, including avian and bovine pancreatic polypeptide and peptide tyrosine tyrosine, excluded any cross-reactivity. The fine structure of the cells containing NPY-like substance is described.

Primary structure of frog PYY: implications for the molecular evolution of the pancreatic polypeptide family

A peptide belonging to the pancreatic polypeptide (PP) family was isolated in pure form from the intestine of the European green frog (Rana ridibunda). The primary structure of the peptide was established as: Tyr-Pro-Pro-Lys-Pro-Glu-Asn-Pro-Gly-Glu10-Asp-Ala- Ser-Pro-Glu-Glu-Met-Thr-Lys-Tyr20-Leu-Thr-Ala-Leu-Arg-His-Tyr-Ile- Asn-Leu30-Val - Thr-Arg-Gln-Arg-Tyr-NH2. This amino acid sequence shows moderate structural similarity to human PYY (75% identity) but stronger similarity to the PP family peptides isolated from the pancreas of the salmon (86%) and dogfish (83%). The data suggest that the two putative duplications of an ancestral PP family gene that have given rise to PP, PYY and NPY in mammals had already taken place by the time of the appearance of the amphibia. In fish, however, only a single duplication has occurred, giving rise to NPY in nervous tissue and a PYY-related peptide in both pancreas and gut.

Dual peptidergic innervation of the blowfly hindgut: a light- and electron microscopic study of FMRFamide and proctolin immunoreactive fibers

1. The innervation of the hindgut, rectal valve, rectum and rectal papillae of the adult blowfly, Calliphora erythrocephala, was studied by means of light and electron microscopic immunocytochemistry, using antibodies against the neuropeptides proctolin and FMRFamide. 2. Branches from the abdominal nerves reaching the posterior portion of the gut were found to contain mostly neurosecretory type axons and to innervate the muscle coat of all hindgut structures studied. 3. Some of the axons found in these nerve branches innervating the gut display proctolin- others FMRFamide-like immunoreactivity. Both types of peptidergic axons were found to have abundant terminals in the muscle coat of the hindgut, rectum and rectal valve and in the medulla of the rectal papillae. 4. It is clear that two separate peptidergic systems derived from the abdominal ganglion are supplying the hindgut structures, and, possibly, they use proctolin- and FMRFamide-like peptides respectively as their transmitters or modulators.

Isolation and partial sequencing of a pancreatic polypeptide-like neuropeptide from the liver fluke, Fasciola hepatica

1. A pancreatic polypeptide (PP)-immunoreactive neuropeptide has been isolated and partially sequenced from the liver fluke, Fasciola hepatica. 2. Gel permeation chromatography of an acid ethanol extract of cattle flukes showed that the peptide is similar in size to mammalian (bovine) PP. 3. The Fasciola peptide was purified to homogeneity by means of reverse-phase HPLC, employing different column chemistries. 4. The purified peptide was sequenced using automated gas-phase Edman degradation and the first 24 amino acid residues determined.

Localization and characterization of neuropeptide Y in the brain of Microcebus murinus (Primate, Lemurian)

The distribution of neuropeptide Y (NPY) in the brain of the lemur Microcebus murinus was determined by immunocytochemistry with the aid of a highly specific antiserum against synthetic porcine NPY. When compared with previous immunohistochemical data obtained in primates and other mammalian species, the localization of NPY-immunoreactive (IR) structures in the Microcebus murinus brain revealed particular features. (1) Numerous NPY-IR perikarya and a dense network of IR nerve terminals were found in the supraoptic and suprachiasmatic nuclei, respectively. The occurrence of NPY-IR perikarya in the supraoptic nucleus, also reported in the squirrel monkey, seems to be specific to primates. In the squirrel monkey, the suprachiasmatic nucleus exhibits only a moderate innervation, whereas in humans it appears totally devoid of NPY-IR fibers. (2) IR perikarya and axon processes were observed in many upper brainstem areas, in particular in the interpeduncular, raphe pontine, dorsal tegmental, parabrachial, and dorsal raphe nuclei, in the locus coeruleus, the nucleus of the solitary tract, and the reticular formation; in this latter area, the occurrence of two categories of NPY-IR neurons was demonstrated on the basis of their morphology and localization, suggesting that they may play distinct roles. (3) NPY-IR nerve processes could be traced over a long distance. (4) For the first time, numerous NPY-IR terminals were observed close to the lumen of the various cerebral ventricles. The immunoreactive NPY-like peptide was characterized by combining high performance liquid chromatography (HPLC) analysis and radioimmunoassay quantification. The dilution curves obtained with synthetic porcine NPY and serial dilutions of occipital cortex, paraventricular and supraoptic hypothalamus, posterior hypothalamus, medulla oblongata, or preoptic area extracts were parallel. The highest amounts of NPY were measured in the hypothalamus and telencephalon. HPLC analysis resolved a single peak of NPY-like immunoreactivity that exhibited the same retention time as synthetic porcine NPY. The distribution of NPY in the lemurian brain is discussed with respect to phylogeny and putative functions.

Neuropeptide Y: localization in the central nervous system and neuroendocrine functions

Neuropeptide Y (NPY) is a 36-amino acid peptide first isolated and characterized from porcine brain extracts. A number of immunocytochemical investigations have been conducted to determine the localization of NPY-containing neurons in various animal species including both vertebrates and invertebrates. These studies have established the widespread distribution of NPY in the brain and in sympathetic neurons. In the rat brain, a high density of immunoreactive cell bodies and fibers is observed in the cortex, caudate putamen and hippocampus. In the diencephalon, NPY-containing perikarya are mainly located in the arcuate nucleus of the hypothalamus; numerous fibers innervate the paraventricular and suprachiasmatic nuclei of the hypothalamus, as well as the paraventricular nucleus of the thalamus and the periaqueductal gray. At the electron microscope level, using the pre- and post-embedding immunoperoxidase techniques, NPY-like immunoreactivity has been observed in neuronal cell body dendrites and axonal processes. In nerve terminals of the hypothalamus, the product of the immunoreaction is associated with large dense core vesicles. In lower vertebrates, including amphibians and fish, neurons originating from the diencephalic (or telencephalic) region innervate the intermediate lobe of the pituitary where a dense network of immunoreactive fibers has been detected. At the ultrastructural level, positive endings have been observed in direct contact with pituitary melanotrophs of frog and dogfish. These anatomical data suggest that NPY can act both as a neurotransmitter (or neuromodulator) and as a hypophysiotropic neurohormone. In the rat a few NPY-containing fibers are found in the internal zone of the median eminence and high concentrations of NPY-like immunoreactivity are detected in the hypothalamo-hypophyseal portal blood, suggesting that NPY may affect anterior pituitary hormone secretion. Intrajugular injection of NPY causes a marked inhibition of LH release but does not significantly affect other pituitary hormones. Passive immunoneutralization of endogenous NPY by specific NPY antibodies induces stimulation of LH release in female rats, suggesting that NPY could affect LH secretion at the pituitary level. However, NPY has no effect on LH release from cultured pituitary cells or hemipituitaries. In addition, autoradiographic studies show that sites for 125I-labeled Bolton-Hunter NPY or 125I-labeled PYY (2 specific ligands of NPY receptors) are not present in the adenohypophysis, while moderate concentrations of these binding sites are found in the neural lobe of the pituitary. It thus appears that the inhibitory effect of NPY on LH secretion must be mediated at the hypothalamic level.(ABSTRACT TRUNCATED AT 400 WORDS)