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PubMed2001

Physiological effects of FMRFamide-related peptides and classical transmitters on dispersed muscle fibres of the turbellarian, Procerodes littoralis.

The physiological effects of selected classical transmitters and FMRFamide-related peptides (FaRPs) on dispersed muscle fibres from the marine turbellarian, Procerodes littoralis have been examined. Confocal scanning laser microscopy coupled with fluorescein isothiocyanate (FITC) or tetramethylrhodamine (TRITC)-labelled phalloidin revealed a highly developed body wall muscle system with circular, longitudinal and diagonal layers of muscle fibres. Dispersed muscle fibres contracted when depolarized by exposure to extracellular media with elevated K+ (15-100 mM) in a concentration-dependent manner, with a maximal response of 87% achieved at > or = 75 mM. 5-Hydroxytryptamine (5-HT) induced concentration-dependent muscle contraction between 0.01 and 1000 microM, with 10 microM producing a near maximal contraction response of 75%. Acetylcholine (ACh) had less pronounced excitatory effects (0.01-1000 microM), inducing contraction of only 32% of the fibres at 100 microM. The flatworm FMRFamide-related peptides (FaRPs), GYIRFamide, YIRFamide and GNFFRFamide each had concentration-dependent myocontractile effects, indicating the occurrence of at least 1 FaRP receptor on P. littoralis muscle fibres. At 10 microM peptide, GNFFRFamide induced contractions in < 40% of the muscle fibres examined, whereas YIRFamide and GYIRFamide induced contraction in 70 and 75% of muscle fibres, respectively. The order of potency of the peptides was: GYIRFamide > YIRFamide > GNFFRFamide. Pre-incubation of the muscle fibres in 5 microM 5-HT significantly reduced the responses to GYIRFamide, YIRFamide and 5-HT, while the responses to high K+ remained unaltered. Muscle fibres pre-incubated in GYIRFamide (0.1 microM) were also less responsive to 5-HT but not to ACh and high-K+. The GYIRFamide analogue, GYIRDFamide, did not induce muscle contraction (0.01-100 microM) per se, but when co-applied with the myoactive peptides GYIRFamide, YIRFamide or GNFFRFamide, it significantly blocked their ability to elicit contractions. This suggests that the peptides tested may act via a common muscle-based neuropeptide receptor. GYIRDFamide did not alter the contractile effects of high K+, 5-HT or ACh. Collectively, these results indicate that FaRPs, 5-HT and ACh all have the potential to cause muscle contraction in flatworms and that 5-HT and FaRPs alter muscle sensitivity to each other, but do not influence the ability of flatworm muscle fibres to contract.

Acetylcholine↗
PubMed1994

FMRFamide-related peptides in the sex segmental ganglia of the Pharyngobdellid leech Erpobdella octoculata. Identification and involvement in the control of hydric balance.

Using enzyme-linked immunosorbent assays, a dot-immunobinding assay and a three-step reverse-phase HPLC separation, four Arg-Phe-amide (RFamide) peptides were purified from sex segmental ganglia extracts of the leech Erpobdella octoculata; FMRFamide, FM(O)RFamide, FLRFamide and GDPFLRFamide. Their amino acid sequences were elucidated by means of a combined approach using antiserum specificity, synthetic-peptide coelution, automated Edman degradation and electrospray mass spectrometry. One of these peptides, GDPFLRFamide, is a novel leech RFamide neuropeptide. Two of the above RFamide peptides are involved in the control of leech hydric balance; one (GDPFLRFamide) is diuretic, the other (FMRFamide) is anti-diuretic. Titration of each purified RFamide peptide indicated a similar amount of each tetrapeptide and of tetrapeptides and heptapeptides. A comparison between RFamide peptides of E. octoculata and molluscs reveals structural similarities supporting the hypothesis for the existence of an ancestral RFamide peptide gene common to leeches and molluscs.

Amino Acid Sequence↗
PubMed1996

Characterization of two myotrophic neuropeptides in the FMRFamide family from the segmental ganglia of the moth Manduca sexta: candidate neurohormones and neuromodulators

We have characterized two new members of the FMRFamide family of neuropeptides from the segmental ganglia of the tobacco hornworm Manduca sexta. Levels of peptides in ganglia used for purification were enhanced by manipulating their exposure to the steroid molting hormones. Explants of ganglia were cultured in the low-level ecdysteroid environment of diapausing pupae shown previously to evoke accumulation of FMRFamide-like immunoreactivity (FLI). Sufficient material for sequencing was obtained from 180 explanted ganglia. Extracts of ganglia were fractionated using two reverse-phase liquid chromatography procedures, and the immunoreactive fractions were subjected to sequence analysis using electrospray mass spectrometry. The sequences of the two peptides were determined to be GNSFLRFamide and DPSFLRFamide. These peptides have been named MasFLRFamide II and MasFLRFamide III, respectively; the previously characterized M. sexta FLRFamide (pEDVVHSFLRFamide) has been renamed MasFLRFamide I. The three peptides show distinctive tissue and developmental distributions as determined from fractionated extracts of larval and adult central nervous system structures and neurohemal organs. In the retrocerebral corpora cardiaca/corpora allata, MasFLRFamide I was the predominant form, while in the segmental ganglia MasFLRFamides II and III predominated. Higher levels of MasFLRFamide I and II were found in the adult, whereas there was little apparent change in the level of MasFLRFamide III upon metamorphosis. Determinations of peptide levels in fractionated hemolymph of newly emerged moths revealed that levels of MasFLRFamide I and III could exceed 10 nmol l-1. The actions of the three peptides were tested on the moth ileum. MasFLRFamides II and III were found to be stimulatory. At 1 nmol l-1, these peptides induced robust increases in the rate of rhythmic longitudinal and peristaltic waves of contractions. In contrast, MasFLRFamide I was ineffective even at 20 nmol l-1. Thus, while all three peptides have the characteristics of neurohormones in M. sexta, the physiological findings show that the heptapeptide FLRFamides have properties distinct from those of the decapeptide.

Journal Article↗
PubMed1999

FMRFamide neuropeptides and neuropeptide-associated enzymes in Drosophila.

To review the histochemistry of neuropeptide transmitters system in insects, this chapter focuses on the biology of FMRFamide-related neuropeptides in Drosophila. dFMRFamide expression is limited to a small number of neurons that present a complex spatial pattern and whose functions appear heterogeneous. The neuropeptide is first expressed by a few neurons in late stage embryos, then dynamically in as many as 44 neurons in the larval CNS. This review describes histochemical procedures to evaluate this neuronal phenotype and its regulation, including descriptions of promoter activity, and RNA and peptide distributions. To evaluate the use of peptidergic transmitters on a broad scale, I also review experiments in Drosophila studying enzymes necessary for neuropeptide biosynthesis, and in particular, histochemical studies of an enzyme responsible for peptide alpha-amidation.

Amino Acid Sequence↗
PubMed2000

Gene expression and function of FMRFamide-related neuropeptides in the snail Lymnaea.

FMRFamide and a large family of related peptides (FaRPs) have been identified in every major metazoan phylum examined, including chordates. In the pulmonate snail Lymnaea this family of neuropeptides is encoded by a five-exon locus that is subject to alternative splicing. The two alternative mRNA transcripts are expressed in the CNS in a mutually exclusive manner at the single cell level, resulting in the differential distribution of the distinct sets of FaRPs that they encode in defined neuronal networks. Biochemical peptide purification, single-cell analysis by mass spectroscopy, and immunocytochemistry have led to an understanding of the post-translational processing patterns of the two alternative precursor proteins and identified at least 12 known and novel peptides contained in neuronal networks involved in cardiorespiration, penial control and withdrawal response. The pharmacological actions of single or co-expressed peptides are beginning to emerge for the cardiorespiratory network and its central and peripheral targets. Peptides derived from protein precursor 1 and contained in the heart excitatory central motoneurons E(he) have distinct functions and also act in concert in cardiac regulation, based on their unique effects on heartbeat and their differential stimulatory effects on second messenger pathways. Precursor-2 derived peptides, contained in the Visceral White Interneuron, a key neuron of the cardiorespiratory network, have mostly inhibitory effects on the VWI's central postsynaptic target neurons but with some of the peptides also exhibiting excitatory effects on the same cells.

Animals↗
PubMed1994

Alternative mRNA splicing of the FMRFamide gene and its role in neuropeptidergic signalling in a defined neural network.

Neuronal signalling involves multiple neuropeptides that are diverse in structure and function. Complex patterns of tissue-specific expression arise from alternate RNA splicing of neuropeptide-encoding gene transcripts. The pattern of expression and its role in cell signalling is difficult to study at the level of single neurons in the complex vertebrate brain. However, in the model molluscan system, Lymnaea, it is possible to show that alternate mRNA expression of the FMRFamide gene is specific to single identified neurons. Two different transcripts are expressed in a mutually exclusive manner in different neurons. Post-translational processing of the two precursor proteins leads to completely distinct sets of neuropeptide transmitters. The function of these transmitter cocktails, resulting from alternate mRNA splicing, was studied physiologically in identified neurons forming part of a behaviourally important network regulating heartbeat.

Alternative Splicing↗
PubMed2001

Distribution and development of FMRFamide-like immunoreactive neuronal systems in the brain of the brown trout, Salmo trutta fario.

The distribution of Phe-Met-Arg-Phe-amide (FMRFamide) peptide-immunoreactive (FMRF-ir) cells and fibers in the terminal nerve and central nervous system was investigated in developing stages and adults of the brown trout, Salmo trutta fario. The first FMRF-ir neurons appeared in the terminal nerve system of 8-mm embryos in and below the olfactory placode. In the brain, FMRF-ir neurons were first observed in the rostral hypothalamus, primordial hypothalamic lobe, mesencephalic laminar nucleus, and locus coeruleus of 12- to 13 -m embryos. After hatching, FMRF-ir cells appeared in the lateral part of the ventral telencephalic area and the anterior tuberal nucleus. In adult trout, FMRF-ir cells were observed in all these areas. The number of FMRF-ir neurons increased markedly in some of these populations during development. Dense innervation by FMRF-ir fibers was observed in the dorsal and lateral parts of the dorsal telencephalic area, and in the ventral telencephalic area, the lateral preoptic area, the medial hypothalamic and posterior tubercle regions, midbrain tegmentum and rhombencephalic reticular areas, the central gray, the superior raphe nucleus, the secondary visceral nucleus, the vagal nuclei, and the area postrema. Fairly rich FMRF-ir innervation was also observed in the optic tectum and some parts of the torus semicircularis. The saccus vasculosus and hypophysis received a moderate amount of FMRF-ir fibers. Innervation of most of these regions appeared either in late alevins or fry, although FMRF-ir fibers in the preoptic area, hypothalamus, and reticular areas appeared in embryos. Comparative analysis of the complex innervation pattern observed in the brain of trout suggests that FMRF is involved in a variety of functions, like the FMRF family of peptides in mammals.

Aging↗
PubMed2004

Expression and regulation of an FMRFamide-related neuropeptide gene family in Caenorhabditis elegans.

FMRFamide (Phe-Met-Arg-Phe-NH2) and related peptides (FaRPs) have been found throughout the animal kingdom, where they are involved in many behaviors. We previously identified 22 genes comprising the flp gene family that encodes FaRPs in Caenorhabditis elegans; in this paper we report the identification of another flp gene, flp-23. As a first step toward determining their functional roles in C. elegans, we examined the cell-specific expression pattern of the flp gene family. Of the 19 flp genes examined, each gene is expressed in a distinct set of cells; these cells include interneurons, motor neurons, and sensory neurons that are involved in multiple behaviors, as well as supporting cells, muscle cells, and epidermal cells. Several flp genes show sex-specific expression patterns. Furthermore, we find that expression of two flp genes changes in response to the developmental state of the animal. Many neurons express multiple flp genes. To investigate how flp genes are regulated in different neuronal subtypes, we examined flp expression in a small, well-defined subset of neurons, the mechanosensory neurons. Mutations in the unc-86 and mec-3 genes, which are necessary for the production and differentiation of the mechanosensory neurons, result in the complete loss of flp-4, flp-8, and flp-20 expression in mechanosensory neurons. Collectively, these data indicate that members of the flp gene family are likely to influence multiple behaviors and that their regulation can be dependent on the developmental state of the organism.

Animals↗
PubMed2006

Characteristic expression patterns of allatostatin-like peptide, FMRFamide-related peptide, orcokinin, tachykinin-related peptide, and SIFamide in the olfactory system of crayfish Procambarus clarkii.

The olfactory system plays important roles in various crustacean behaviors. Despite numerous studies on different aspects of the olfactory neural pathway, only the decapod-tachykinin-related peptide (decapod-TRP) has been identified as a neuromodulator in this processing to date. To establish the functions of other related neuropeptides, we initially performed cDNA cloning of FMRFamide-related peptide (FaRP) and allatostatin (AST)-like peptide from the crayfish Procambarus clarkii, followed by in situ hybridization (ISH) analysis of these peptides, along with decapod-TRP, orcokinin, and crustacean-SIFamide. Cloned FaRP cDNA encodes seven copies of C-terminal RN(F/Y)LRFamide-containing peptide, whereas AST-like peptide cDNA comprises 29 copies of AST-like peptide (-YXFGLamide) and three additional putative peptides. ISH analysis of the brain revealed specific expression of crustacean-SIFamide mRNA in most projection neurons (cell cluster 10), and predominant localization of other mRNAs to interneurons. The data suggest that the crustacean-SIFamide neuropeptide is involved in output of the deutocerebrum to the protocerebrum. Double-fluorescence ISH data further disclose that, in cluster 9, orcokinin is coexpressed in decapod-TRP-specific interneurons, whereas AST-like peptide-containing cells do not overlap with orcokinin-expressing cells. On the other hand, FaRP-expressing cells overlap with both orcokinin- and AST-like peptide-specific cells. In cluster 11, where signals for AST-like peptide are absent, a number of interneurons express both decapod-TRP and orcokinin, emphasizing a close relationship between these two factors with regard to olfactory processing, and possibly tactile and/or visual sensory systems. These characteristic expression patterns of neuropeptides support their distinct involvement in the modulation of olfactory processing.

Animals↗
PubMed1991

Neurosecretory cells in the honeybee brain and suboesophageal ganglion show FMRFamide-like immunoreactivity.

Immunocytochemical analysis of the brain and suboesophageal ganglion of the honeybee Apis mellifera L. was combined with Lucifer Yellow backfilling from the corpora cardiaca and intracellular staining of single neurons. It is shown that more than one third of the cells that display FMRFamide-like immunoreactivity (F-LI) project to the corpora cardiaca, suggesting they are neurosecretory. Among the ca. 120 median neurosecretory cells (MNCs) in the pars intercerebralis about 32 show F-LI. The number of immunoreactive MNCs is highly variable and may depend on age and/or diet. Seven of at least 40 lateral neurosecretory cells display F-LI. They project through the brain via the medial branch of the bipartite nervus corporis cardiaci II. In the suboesophageal ganglion three types of immunoreactive neurosecretory cells were identified. Together with the median and the lateral neurosecretory cells in the brain these cells project through a single pair of nerves into the corpora cardiaca suggesting that the nervus corporis cardiaci (NCC) of the honeybee is a fusion of NCC I, II, and III described in other insects.

Animals↗
PubMed2003

Physiological functions of FMRFamide-like peptides (FLPs) in crustaceans.

Neuropeptides play important roles in chemical signalling in the central and peripheral nervous systems. One of the largest families of neuropeptides is that of the FMRFamide-like peptides (FLPs). This paper reviews what is known about the physiological functions of FLPs in crustaceans, focussing on the cardiovascular, digestive and neuromuscular systems.

Animals↗
PubMed2001

Regulation of the pharynx of Caenorhabditis elegans by 5-HT, octopamine, and FMRFamide-like neuropeptides.

More than fifty FMRFamide-like neuropeptides have been identified in nematodes. We addressed the role of a subset of these in the control of nematode feeding by electrophysiological recording of the activity of C. elegans pharynx. AF1 (KNEFIRFamide), AF2 (KHEYLRFamide), AF8 (KSAYMRFamide), and GAKFIRFamide (encoded by the C. elegans genes flp-8, flp-14, flp-6, and flp-5, respectively) increased pharyngeal action potential frequency, in a manner similar to 5-HT. In contrast, SDPNFLRFamide, SADPNFLRFamide, SAEPFGTMRFamide, KPSVRFamide, APEASPFIRFamide, and AQTVRFamide (encoded by the C. elegans genes flp-1; flp-1; flp-3; flp-9; flp-13, and flp-16, respectively) inhibited the pharynx in a manner similar to octopamine. Only three of the neuropeptides had potent effects at low nanomolar concentrations, consistent with a physiological role in pharyngeal regulation. Therefore, we assessed whether these three peptides mediated their actions either directly on the pharynx or indirectly via the neural circuit controlling its activity by comparing actions between wild-type and mutants with deficits in synaptic signaling. Our data support the conclusion that AF1 and SAEPFGTMRFamide regulate the activity of the pharynx indirectly, whereas APEASPFIRFamide exerts its action directly. These results are in agreement with the expression pattern for the genes encoding the neuropeptides (Kim and Li, 1999) as both flp-8 and flp-3 are expressed in extrapharyngeal neurons, whereas flp-13 is expressed in I5, a neuron with synaptic output to the pharyngeal muscle. These results provide the first, direct, functional information on the action of neuropeptides in C. elegans. Furthermore, we provide evidence for a putative inhibitory peptidergic synapse, which is likely to have a role in the control of feeding.

Animals↗
PubMed2005

Role of a FMRFamide-like family of neuropeptides in the pharyngeal nervous system of Caenorhabditis elegans.

The nervous system of C. elegans has a remarkable abundance of flp genes encoding FMRFamide-like (FLP) neuropeptides. To provide insight into the physiological relevance of this neuropeptide diversity, we have tested more than 30 FLPs (encoded by 23 flps) for bioactivity on C. elegans pharynx. Eleven flp genes encode peptides that inhibit pharyngeal activity, while eight flp genes encode peptides that are excitatory. Three potent peptides (inhibitory, FLP-13A, APEASPFIRFamide; excitatory, FLP-17A, KSAFVRFamide; excitatory, FLP-17B, KSQYIRFamide) are encoded by flp genes, which, according to reporter gene constructs, are expressed in pharyngeal motoneurons. Thus, they may act through receptors localized on the pharyngeal muscle. The two other potent peptides, FLP-8 (excitatory AF1, KNEFIRFamide,) and FLP-11A (inhibitory, AMRNALVRFamide), appear to be expressed in extrapharyngeal neurons and are therefore likely to act either indirectly or as neurohormones. Intriguingly, a single neuron can express peptides that have potent but opposing biological activity in the pharynx. Only five flp genes encode neuropeptides that have no observable effect on the pharynx, but none of these have shown reporter gene expression in the pharyngeal nervous system. To examine the roles of multiple peptides produced from single precursors, a comparison was made between the bioactivity of different neuropeptides for five flp genes (flp-3, flp-13, flp-14, flp-17, and flp-18). For all but one gene (flp-14), the effects of peptides encoded by the same gene were similar. Overall, this study demonstrates the impressive neurochemical complexity of the simple circuit that regulates feeding in the nematode, C. elegans.

Action Potentials↗
PubMed1995

Coupling of a single receptor to two different G proteins in the signal transduction of FMRFamide-related peptides.

A series of studies, which have investigated the membrane receptor-mediated signal transduction of PDVDHVFLRFamide in the locust oviduct, suggest the presence of a novel ligand-receptor reaction system. In this system, inhibitory peptides and stimulatory peptides share a single receptor by having the same binding sequence, VFLRFamide, but are able to produce opposite muscle responses due to the differences in activation sites. In this research, the results from both "guanine nucleotide effect assay" and GTPase assay indicated that the receptors for the inhibitory and stimulatory FMRFamide-related peptides (FaRPs) are coupled with G proteins and both inhibitory and excitatory effects of FaRPs on locust oviduct are through the activation of G proteins. Thus it is very likely that the receptor is coupled with two different G proteins. The activation of one is responsible for the inhibitory effect and the activation of the other is responsible for the stimulatory effect.

Adenosine Diphosphate Ribose↗
PubMed1995

Isolation of AF2 (KHEYLRFamide) from Caenorhabditis elegans: evidence for the presence of more than one FMRFamide-related peptide-encoding gene.

Numerous FMRFamide-related peptides (FaRPs) have been isolated and sequenced from extracts of free-living and parasitic nematodes. The most abundant FaRP identified in ethanolic/methanolic extracts of the parasitic forms, Ascaris suum and Haemonchus contortus and from the free-living nematode, Panagrellus redivivus, was KHEYLRFamide (AF2). Analysis of the nucleotide sequences of cloned FaRP-precursor genes from C. elegans and, more recently, Caenorhabditis vulgaris identified a series of related FaRPs which did not include AF2. An acid-ethanol extract of Caenorhabditis elegans was screened radioimmunometrically for the presence of FaRPs using a C-terminally directed FaRP antiserum. Approximately 300 pmols of the most abundant immunoreactive peptide was purified to homogeneity and 30 pmols was subjected to Edman degradation analysis and gas-phase sequencing. The unequivocal primary structure of the heptapeptide, Lys-His-Glu-Tyr-Leu-Arg-Phe-NH2 (AF2) was determined following a single gas-phase sequencing run. The molecular mass of the peptide was determined using a time-of-flight mass spectrometer and was found to be 920 (MH+)+, which was consistent with the theoretical mass of C-terminally amidated AF2. These results indicate that C. elegans possesses more than one FaRP gene.

Amino Acid Sequence↗
PubMed1997

APEASPFIRFamide, a novel FMRFamide-related decapeptide from Caenorhabditis elegans: structure and myoactivity.

To date, 9 FMRFamide-related peptides (FaRPs) have been identified in Caenorhabditis elegans. Eight of these peptides are encoded on the flp-1 gene. However, AF2 (KHEYLRFamide) which was not co-encoded was the most abundant FaRP identified in ethanolic extracts. Further radioimmunometrical screening of acidified ethanol extracts of C. elegans has revealed the presence of other novel FaRPs, which are not encoded on the flp-1 gene. One of these peptides has been isolated by sequential rpHPLC and subjected to Edman degradation analysis and gas-phase sequencing and the unequivocal primary structure of the decapeptide Ala-Pro-Glu-Ala-Ser-Pro-Phe-Ile-Arg-Phe-NH2 was determined following a single gas-phase sequencing run. The molecular mass of the peptide was found to be 1133.7 Da, determined using a time-of-flight mass spectrometer. Synthetic replicates of this peptide were found to induce a profound relaxation of both dorsal and ventral somatic muscle-strip preparations of Ascaris suum with a threshold for activity of 10 nM. The inhibitory response was not dependent on the presence of nerve cords, indicating a post-synaptic site-of-action. The relaxation was Ca(+2)- and Cl(-)-independent but was abolished in high-K+ medium and could be distinguished from those of other inhibitory nematode FaRPs, including PF1 (SDPNFLRFamide) and PF4 (KPNFIRFamide).

Amino Acid Sequence↗
PubMed1993

The wide range of actions of the FMRFamide-related peptides and the biological importance of peptidergic messengers.

The importance of peptides as intercellular messengers is discussed. The view is put forward that peptides evolved early in evolution as chemical messengers and that they have come to exert a wide range of actions. Using as an example the FMRFamide (Phe-Met-Arg-Phe-NH2) related peptide family of molluscs, the wide range of peptide actions on membrane currents is discussed and considered in relation to co-localization of peptides with low molecular weight (or "classical") intercellular messengers.

Amino Acid Sequence↗
PubMed1994

Immunogold labelling of serotonin-like and FMRFamide-like immunoreactive material in neurohaemal areas on abdominal nerves of Rhodnius prolixus.

The ultrastructure of neurohaemal areas on abdominal nerves of the blood-sucking bug Rhodnius prolixus was investigated. Four types of axon terminals were found, distinguished by the morphology of their neurosecretory granules. By use of post-embedding immunogold labelling, granules in Type I axon terminals were shown to contain serotonin-like immunoreactive material, and granules in Type II axon terminals were shown to contain FMRFamide-like immunoreactive material. There was no colocalization of these materials. It is suggested that Type III terminals contain peptidergic diuretic hormone, which has previously been reported to be present in electron-dense neurosecretory granules in this neurohaemal area. The identity of material in Type IV terminals is unknown.

Amino Acid Sequence↗