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PubMed1986

The Aplysia FMRFamide gene encodes sequences related to mammalian brain peptides.

We have characterized a precursor protein which gives rise to the neuropeptide Phe-Met-Arg-Phe-amide (FMRFamide) by determining the nucleotide sequence of a genomic and five cDNA clones. The 597-amino-acid protein contains 28 copies of the tetrapeptide FMRFamide, a single Phe-Leu-Arg-Phe-amide (FLRFamide), and other sequences flanked by paired basic residues, some of which have homologies to mammalian brain peptides. The data presented suggest the genes encoding pro-opiomelanocortin, pre-pro-enkephalin, and the hypothalamic releasing factor, cortico-releasing factor (CRF), arose from a common ancestral gene.

Animals↗
PubMed1992

SKPYMRFamide, a novel FMRFamide-related peptide in the snail Lymnaea stagnalis.

In Lymnaea stagnalis, three members of the FMRFamide peptide family have been chemically identified in the central nervous system, and other members of the family are predicted by cDNA studies. The present study demonstrates the occurrence of even more FMRFamide-related peptides in this species by identifying a novel member of this family. The peptide was purified from brain extracts by three different HPLC steps. Its amino acid sequence has been determined as Ser-Lys-Pro-Tyr-Met-Arg-Phe-amide (SKPYMRFamide).

Amino Acid Sequence↗
PubMed1996

Post-translational processing of the alternative neuropeptide precursor encoded by the FMRFamide gene in the pulmonate snail Lymnaea stagnalis.

The neuropeptide gene encoding FMRFamide-like peptides in the pulmonate mollusc Lymnaea is subject to alternative splicing that generates cell-specific expression of distinct sets of peptides in the CNS. In this paper, we analyse the post-translational processing of the alternative protein precursor encoded by the exon I, III-V transcript (type 2 transcript). We raised anti-peptide antisera specific to distinct segments of the precursor in order to address the pattern of endoproteolytic cleavages, specifically around the tetrabasic site RRKR. We first showed that not all peptides predicted by the precursor structure are generated as final steady-state products. We then identified a novel peptide by biochemical purification, amino acid sequencing and mass spectrometry- the 35 amino acid SDPFFRFGKQQVATDDSGELDDEILSRVSDDDKNI, which we termed the acidic peptide, previously not predicted on the basis of the precursor structure. This novel peptide, abundant in the snail brain (0.7 pmol per central nervous system), includes the N-terminal sequence SDPFFRF, which was previously considered to be a variant of the known heptapeptide SDPFLRFamide, also encoded within the same protein precursor. We showed by in situ hybridization and immunocytochemistry that the acidic peptide is produced in all cells that transcribe type 2 FMRFamide mRNA. We mapped the expression of this novel peptide in the CNS and localized it mainly in three identifiable neuronal clusters - the E, F and B groups of cells - and some additional neurons, all situated in three of the eleven central ganglia. Immunoreactive neurons included the single identifiable visceral white interneuron (VWI or VD4), a key cell of the cardiorespiratory network.

Amino Acid Sequence↗
PubMed1992

FMRFamide-related peptides potentiate transmission at the squid giant synapse.

The stellate ganglion of the squid Loligo pealli contains the neuropeptides Phe-Met-Arg-Phe-NH2 (FMRFamide), Phe-Leu-Arg-Phe-NH2 (FLRFamide) and at least one N-terminally extended FMRFamide-related peptide that is yet to be fully characterized. Both local application and arterial perfusion of FLRFamide potentiate transmission at the giant synapse. The N-terminally related peptide Ser-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (SDPFLRFamide) produced a similar effect. The threshold for both the tetra- and the hepta-peptides was less than 10 microM. Potentiation could be detected as an increase in rate of rise of the EPSPs, as an increase in amplitude of the EPSP in the absence of spikes, or under voltage clamp as an increase in the EPSC. The effect was most pronounced when the synapse was fatigued by high frequency stimulation. Another molluscan peptide, eledoisin and also leucine enkephalin were without effect. In the absence of any detectable effects of FLRFamide on the resting membrane potential of either pre- or postsynaptic terminals or on the presynaptic spike, it is suggested that the peptide influences transmitter mobilization. However, the peptide could also exert small changes in preterminal calcium currents, which so far we have been unable to detect.

Animals↗
PubMed1987

Multiple receptor sites for a molluscan peptide (FMRFamide) and related peptides of Helix.

1. The membrane actions of some tetrapeptide amides and heptapeptide amides chemically related to the molluscan neuropeptides Phe-Met-Arg-Phe-NH2 (FMRFamide) and p-Glu-Asp-Pro-Phe-Leu-Arg-Phe-NH2 (pQDPFLRFamide) were tested and compared on identified neurones of Helix aspersa. 2. The C-terminal sequence -Phe-NH2 was an important requirement for each of the four different actions studied: slow increase in K conductance (gK), fast increase in gK, increase in Na conductance (gNa) and decrease in gK. 3. The response of some neurones involved a combination of such actions. 4. The tetrapeptide amides FMRFamide, Phe-Leu-Arg-Phe-NH2 (FLRFamide) and Phe-Ile-Arg-Phe-NH2 (FIRFamide) were more potent than the heptapeptide amides at producing the slow increase in gK and also produced the increase in gNa, not seen at all with the heptapeptide amides. 5. The heptapeptide amides induced the fast increase in gK which was not observed with the tetrapeptide amides. 6. Evidence is presented that each of the tetrapeptide amides tested acts on the same receptor type which mediates the increase in gNa and on which the heptapeptides were inactive. 7. The results are interpreted in terms of multiple receptors each of which however appears to require the C-terminal sequence Phe-Met(or Leu)-Arg-Phe-NH2, as has been shown for some molluscan muscle preparations which react to these peptide amides (Price & Greenberg, 1980).

Action Potentials↗
PubMed2002

Signaling pathways and physiological functions of Drosophila melanogaster FMRFamide-related peptides.

FMRFamide-related peptides (FaRPs) contain a C-terminal RFamide but unique N-terminal extensions. They are expressed throughout the animal kingdom and affect numerous biological activities. Like other animal species, Drosophila melanogaster contains multiple genes that encode different FaRPs. The ease of genetic manipulations, the availability of genomic sequence data, the existence of established bioassays, and its short lifespan make D. melanogaster a versatile experimental organism in which to investigate peptide processing, functions, and signal transduction pathways. Here, the structures, precursor organizations, distributions, and activities of FaRPs encoded by D. melanogaster FMRFamide (dFMRFamide), myosuppressin (Dms), and sulfakinin (Dsk) genes are reviewed, and predictions are made on their signaling pathways and biological functions.

Amino Acid Sequence↗
PubMed1995

Nitric oxide mediates the inhibitory effects of SDPNFLRFamide, a nematode FMRFamide-related neuropeptide, in Ascaris suum.

1. The physiological effects of two Phe-Met-Arg-Phe-NH2 (FMRFamide)-related neuropeptides isolated from the free-living nematode Panagrellus redivivus, SDPNFLRFamide (PF1) and SADPNFLRFamide (PF2), were examined using neuromuscular preparations from the parasitic nematode Ascaris suum. 2. PF1 and PF2 hyperpolarized muscle membrane and induced sustained flaccid paralysis, independent of external Cl-, in both innervated and denervated preparations. 3. PF1 reversed spastic contractions induced by the cholinomimetic levamisole, elevated K+, or the excitatory nematode FMRFamide-related neuropeptides KNEFIRFamide or KHEYLRFamide. 4. PF1 reversal of levamisole contraction was blocked by pretreatment with agents that interfere with nitric oxide (NO) synthesis (e.g., N-nitro-L-arginine), whereas sodium nitroprusside, which releases NO in solution, mimicked PF1 and PF2. 5. NO synthase activity, monitored by the conversion of [3H]arginine to [3H]citrulline, was twice as abundant in A. suum hypodermis as in muscle, but was not present in reproductive tissue. The relative abundance of NO synthase activity in these tissues was similar to the observed specific binding of [3H]PF1. 6. These results suggest that the inhibitory effects of PF1 and PF2 on nematode somatic muscle are mediated by NO, and that the hypodermis may serve a role in this process analogous to that of the endothelium in vertebrate vasculature.

Amino Acid Sequence↗
PubMed2004

A possible stimulatory effect of FMRFamide on neural nitric oxide production in the central nervous system of Helix lucorum L.

The anatomical and functional relationship between neurons expressing nitric oxide (NO) synthase and molluscan cardioexcitatory (FMRFamide)-like neuropeptides was studied in the central ganglia of Helix lucorum (Pulmonata, Gastropoda), applying NADPHdiaphorase (NADPHd) histochemistry to visualize NO synthase and immunocytochemistry to demonstrate FMRFamide (FMRFa) at the light microscopic level. The NO production of the ganglia was detected by the colorimetric Griess determination of nitrite, a breakdown product of NO. Effects of the NO synthase substrate amino acid L-arginine, the NO synthase inhibitor Nomega-nitro-L-arginine (NOARG), synthetic FMRFa and the FMRFa sensitive ion channel blocker amiloride hydrochloride on nitrite production were also tested. NADPHd reaction labeled nerve cells and fibers in the procerebra, mesocerebra and metacerebra within the cerebral ganglia, and cell clusters in the postcerebral ganglia. FMRFa immunolabeling could be observed within subpopulations of NADPHd positive cells and in pericellular varicose fibers surrounding NADPHd stained neurons. Nitrite production of the ganglia was stimulated by L-arginine (10- 20 mM) but was decreased by NOARG (1-2 mM). Synthetic FMRFa (0.830-3.340 mM) increased the nitrite production in a dose dependent manner, but was ineffective in the presence of NOARG. Amiloride hydrochloride (7.890 mM) reduced the FMRFa evoked nitrite production in all ganglia. This is the first description of an anatomical relationship between putative NO producing and FMRFa containing cells, suggesting a possible regulatory role of FMRFa in the NO mediated signaling in an invertebrate nervous system.

Animals↗
PubMed1990

Seven FMRFamide-related and two SCP-related cardioactive peptides from Helix.

Pulmonate snails have a more complex array of cardioexcitatory peptides than other molluscs, and Helix has a more complex array than most other pulmonates. Since a full characterisation of the cardioexcitatory peptides is necessary for an understanding of physiology, we sought to identify the members of two families of such peptides - the small cardioactive peptides (SCPs) and the FMRFamide-related peptides (FaRPs) - from Helix aspersa. We characterised the peaks of immunoreactivity from HPLC both by their elution times and by their molecular weights as determined by fast atom bombardment mass spectrometry (FABms). These two criteria, used in parallel, facilitated our identification of several known peptides: MNYLAFPRMamide, identical to SCPB of Aplysia; two tetrapeptide FaRPs, FRMRamide and FLRFamide; and three hepatapeptide FaRPs, NDPFLRFamide, SDPFLRFamide and pQDPFLRFamide. Of these peptides, only FMRFamide and pQDPFLRFamide have previously been reported from Helix. We also discovered an additional SCP and two novel FaRPs and sequenced them. The SCP is Ser-Gly-Tyr-Leu-Ala-Phe-Pro-Arg-Met-amide (SGYLAFPRMamide), and the heptapeptide FaRPs are Asn-Asp-Pro-Tyr-Leu-Arg-Phe-amide (NDPYLRFamide) and Ser-Glu-Pro-Tyr-Leu-Arg-Phe-amide (SEPYLRFamide). When these nine peptides were tested on isolated Helix ventricles, the SCPs were the most potent cardioexcitors, the heptapeptide FaRPs were next, and the tetrapeptides had the least activity.

Amino Acid Sequence↗
PubMed1998

Effects of food nutrient content, insect age and stage in the feeding cycle on the FMRFamide immunoreactivity of diffuse endocrine cells in the locust gut.

We have studied the influence of variations in dietary protein and digestible carbohydrate content, of insect age and of time during the feeding cycle on the endocrine cells of the ampullar region of the midgut in the African migratory locust Locusta migratoria L. Morphometric analysis of FMRFamide-like immunoreactivity was used as an indirect measure of the amount of FMRFamide-related peptides (FaRPs) stored in the gut endocrine cells. There was a highly significant correlation between FaRP content and the nutritional quality of the food, measured relative to the concentrations and ratio of protein to digestible carbohydrate in a nutritionally optimal diet. The direction of the relationship between FaRP content and diet quality varied with age during the fifth stadium. On day 1, FaRP levels increased with the nutritional quality of the food, while on day 4 the opposite relationship was observed. Release of peptide was triggered by the onset of a meal during ad libitum feeding, with cell FaRP levels returning to premeal values within 15 min of the meal ending. The results also suggested that cell contents were released during food deprivation beyond the normal intermeal interval. Locusts switched for a single meal during ad libitum feeding on day 4 from a low- to a high-carbohydrate food did not respond by reducing endocrine cell FaRP content. Our results show a relationship between the diffuse gut endocrine system and feeding and nutrition in locusts. The ampullar endocrine cells are in three-way contact with the midgut luminal contents, with the primary urine from the Malpighian tubules and with the haemolymph. They are thus ideally positioned to play an integrative receptor-secretory function in the regulation of a variety of post-ingestive processes, such as enzyme secretion, absorption, gut motility or nutrient metabolism.

Age Factors↗
PubMed2000

FMRFamides exert a unique modulation of rodent pancreatic polypeptide sensitive neuropeptide Y (NPY) receptors.

FMRFamide and related peptides (RFamides) were found to inhibit the association binding of iodinated human pancreatic polypeptide ([125I]hPP) to Y5-like neuropeptide Y (NPY) receptor in rodent tissues. An allosteric regulation of the activity of the rodent kidney PP-sensitive neuropeptide Y (NPY) receptor by RFamides was indicated by potency decrease with particle concentration in the inhibition of the association binding of 125I-labeled human pancreatic polypeptide (hPP) by RFamides at rabbit kidney membranes. The competition by C-terminal hexapeptide of hPP (LTRPRY.NH2) did not show such affinity change. The steady-state binding of hPP showed little sensitivity to any of the RFamides tested. The Y1-selective binding of [125I][Leu31,Pro34]hPYY (at 2 nM hPP) was much less sensitive to RFamides than the binding of [125I]hPP, albeit with some differences across tissue or cell types. The binding of Y2-selective agonist 125I-labeled human peptide YY (3-36) was quite insensitive to RFamides. The presence of a unique component in the inhibition of hPP binding by RFamides was further indicated by a degree of antagonism with phospholipase C inhibitor U-73122, and by an only limited cooperation with a N5-amiloride compound, and with alkylator chloroethylclonidine. Change of the chirality of individual residues in the FMRFamide molecule produced a significant reduction of inhibitory potency only with D-Phe in the C-terminal position. Substitution of the (C-3) L-Met by L-Leu greatly increased the inhibitory potency of RFamides relative to otherwise identical congeners. RFamides could act both as ligands of membrane neighbors of the PP receptor, and as competitors of Y5-like NPY receptor epitopes that accommodate the C-terminal aspects of agonist peptides.

Amino Acid Sequence↗
PubMed1992

Activation of a divalent cation-conducting channel in heart ventricle muscle cells of the snail Lymnaea stagnalis by the molluscan cardioactive peptide FMRFamide.

Ion channels with characteristics of Ca2+ channels have been found in isolated heart ventricle cells of the snail Lymnaea stagnalis. Although spontaneous Ca2+ or Ba2+ currents were seen only occasionally, spontaneous inward Na+ currents were readily observed in the absence of patch pipette Ca2+ between membrane potentials of -100 mV and +20 mV. These currents were blocked by 2 mM Ni2+, 2 mM Co2+ and 10 microM Ca2+. The channels usually ceased conducting within a few minutes after seal formation with the patch pipette and could not be re-activated with depolarizing voltage steps. However, at the cell's resting potential, 10(-8) to 10(-6) M of the molluscan cardioactive peptide FMRFamide or its analogue FLRFamide2+ applied to the cell membrane away from the patch pipette, induced unitary Ba2+ currents or, in the absence of Ca2+ in the patch pipette, Na+ currents. This suggests that a secondary messenger is involved in the FMRFamide-induced activation of these channels rather than a direct activation of a channel-receptor complex by the peptide.

Amino Acid Sequence↗
PubMed1989

FMRFamide immunoreactivity in the brain and pituitary of Carassius auratus (Cyprinidae, Teleostei).

Neurons immunoreactive for the molluscan cardioactive peptide FMRFamide (FMRFi) in the brain of Carassius were demonstrated immunohistochemically with the peroxidase-antiperoxidase technique (PAP) and three antisera against this tetrapeptide. FMRFi perikarya were consistently found in the ganglion of the nervus terminalis, in some scattered neurons of the nucleus entopeduncularis, in the nucleus praeopticus pars magno- and parvocellularis, the nucleus ventromedialis, the nucleus posterior periventricularis, nucleus recessus lateralis and posterior. Some weak FMRFi neurons occurred in the rostral mesencephalic tegmentum and in the region of the nucleus gustatorius secundus. Both the medullary Mauthner neurons and the cerebellar Purkinje cells were only weakly immunoreactive for FMRFamide, while a group of intensely FMRFi rhombencephalic perikarya, presumably the nucleus motorius nervi vagi, occurred subependymally next to the fourth ventricle. FMRFi fibres and nerve endings occurred in the bulbus olfactorius, in the tractus opticus, and in the central parts of the dorsal, medial and ventral telencephalon. Some FMRFi fibres traversed through the commissura anterior while others occurred close to the hypothalamic nuclei, in the medial layers of the tectum opticum, in the brain stem, in the vagal lobe and in the ventral medulla oblongata. The present results are compared to the FMRFi structures in other fish brains.

Animals↗
PubMed1988

[Effects of FMRFamide on the activity of command neurons in defensive behavior of fed and fasting snails, Helix pomatia].

FMRFamide (Phe-Met-Arg-Phe-NH2) micropneumophoresis changed bimodally the activity of LPa2, LPa3, PPa2 and PPa3 neurones in fasting and fed Helix pomatia. In fasting creatures peptide application elicited hyperpolarization and decreased the neuronal membrane excitability and responses to tactile stimulation. In fed snails peptide application caused depolarization, decreased membrane resistance and increased the neuronal membrane excitability and responses to tactile stimulation. Neurophysiological mechanisms underlying FMRFamide effects on feeding and defense behaviour are discussed.

Animals↗
PubMed1994

Identification and characterization of pleural neurons that inhibit tail sensory neurons and motor neurons in Aplysia: correlation with FMRFamide immunoreactivity.

Neurons on the rostral edge of the ventral surface of the right pleural ganglion were identified as elements of the circuit mediating the defensive tail withdrawal reflex of Aplysia. These neurons produced IPSPs in tail sensory neurons and were classified into two groups, RPI4 and RPI5, according to their affinity for an antibody directed against FMRFamide. RPI4 was not FMRFamide immunoreactive, and RPI5 was. RPI4 and RPI5 were found to have different electrophysiological profiles. The summated IPSPs in sensory neurons produced by RPI4 developed more rapidly and had a shorter duration than those produced by RPI5. In addition, RPI4 produced IPSPs in the tail motor neurons, whereas RPI5 did not. Both RPI4 and RPI5 received excitatory synaptic inputs from stimulation of the pleural-abdominal connective as well as peripheral nerves P8 and P9, which innervate the tail and posterior part of the animal's body. These inputs were sufficient to elicit spikes. In RPI4, the excitatory synaptic inputs were followed by short and transient hyperpolarization, whereas in RPI5, the excitatory synaptic inputs were followed by slow and long-lasting hyperpolarization. Excitatory inputs elicited in RPI4 by stimulation of peripheral nerves appeared to be mediated, at least in part, by activation of tail sensory neurons. Intracellular stimulation of sensory neurons produced EPSPs in RPI4 that appeared to be monosynaptic. These results suggest that inhibitory interneurons underlying the circuit of the tail withdrawal reflex may play roles in mediating or modulating neuronal responses to tail stimulation. By inhibiting tail sensory and motor neurons, these interneurons may reduce the effectiveness of an animal's response to stimulation of the tail.

Animals↗
PubMed1990

Distribution of Met-enkephalin, Leu-enkephalin, substance P, neuropeptide Y, FMRFamide, and serotonin immunoreactivities in the optic tectum of the Atlantic salmon (Salmo salar L.).

The distribution of the neuropeptides methionine- and leucine-enkephalins, substance P, FMRFamide, neuropeptide Y, and vasoactive intestinal peptide, as well as the biogenic amine serotonin was studied in the optic tectum of the Atlantic salmon by means of immunocytochemistry. Peroxidase-antiperoxidase and indirect immunofluorescence methods were used to compare the differential laminar distribution of each of these substances. Nine parts of the optic tectum were selected for analysis on frontal sections: median, dorsolateral, and ventrolateral areas at rostral, medial, and caudal levels. Methionine- and leucine-enkephalin immunoreactive fibers were found in discrete sublayers in the following strata: stratum opticum, stratum fibrosum et griseum superficiale, stratum griseum centrale, stratum, and album centrale. Most of the substance P-, serotonin-, and vasoactive intestinal peptide-immunoreactive fibers were found in the stratum album centrale, whereas the FMRFamide- and neuropeptide Y-immunoreactive fibers were more or less randomly distributed within most of the strata of the optic tectum. Neuropeptide Y-immunoreactive cell bodies were located in the stratum periventriculare. We suggest an extrinsic origin for most of the immunoreactive fibers observed in the optic tectum, except for the neuropeptide Y-immunoreactive fibers that probably originate in the periventricular neurons. Although retinal peptidergic input to the optic tectum has been proposed in other vertebrates, there is no evidence that any of the neuropeptidelike or serotonin immunoreactive fibers in the optic tectum of the salmon should be of retinal origin. Differences and similarities with the distribution of neuropeptides in the optic tectum in representatives of other vertebrate classes are discussed.

Animals↗
PubMedDate not supplied

A new peptide in the FMRFamide family isolated from the CNS of the hawkmoth, Manduca sexta.

We have purified a FMRFamide-like peptide from extracts of brain-subesophageal ganglion of the moth, Manduca sexta. The purification was monitored with a new, competitive ELISA, and accomplished with ion exchange and reverse-phase HPLC. The peptide structure was determined by a combination of tandem mass spectrometry and automated Edman degradation. The amino acid sequence of the peptide is less than Glu-Asp-Val-Val-His-Ser-Phe-Leu-Arg-Phe-amide (pEDVVHSFLRF-NH2). In a separate purification, an identical peptide was isolated from extracts of brain-associated neurohemal structures. We have named this peptide ManducaFLRFamide, to indicate its homology with other members of the "FMRFamide" family. In bioassays, chemically synthesized peptide increased the force of neurally evoked contractions in the major power-producing flight muscles, the dorsal longitudinal muscles. This observation suggests that hormonally released ManducaFLRFamide may play a role in sustaining or promoting the flight behavior necessary for mate-seeking (in males) or oviposition (in females) in sphingid moths.

Amino Acid Sequence↗