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At least 433 records · Page 24Linked to original sources
PubMed1996

Structure-activity relationships of KNEFIRFamide (AF1), a nematode FMRFamide-related peptide, on Ascaris suum muscle.

Analogues of KNEFIRFamide (Lys-Asn-Glu-Phe-Ile-Arg-Phe-NH2; AF1), an FMRFamide-related peptide (FaRP) originally isolated from Ascaris suum, were characterized in an A. suum muscle tension assay. AF1 had biphasic effects on this preparation, inducing a brief relaxation followed by excitation and spastic paralysis. Activity of AF1 in this assay was eliminated by N-terminal deletions and by deamidation of the carboxy-terminus. The potency of AF1 was greatly reduced by alanine substitution for any residue. Peptides that retained activity did not show the biphasic response observed with AF1, suggesting that the inhibitory and excitatory phases seen with AF1 may be due to activation of distinct receptors. The basis for the marked differences in potency observed between AF1 and the structurally related nematode FaRP, AF2 (KHEYLRFamide) was also tested. AF2 is approximately 1000-fold more potent than AF1 in this assay, but has physiological effects that are otherwise indistinguishable. KNEYIRFamide and KNEFLRFamide induced characteristic AF1/AF2 responses, but were much less potent than the native peptides. In contrast, KHEYIRFamide resembled AF1 in potency and pattern of responses. These data suggest that AF1 and AF2 act at distinct receptors, and hypothesis supported by the observation that KNEFIAFamide antagonized the effects of AF1 but not of AF2.

Alanine↗
PubMed1984

Immunocytochemical demonstration of a homology in peptidergic neurosecretory cells in the suboesophageal ganglion of a beetle and a locust with antisera to bovine pancreatic polypeptide, FMRFamide, vasopressin and alpha-MSH.

In the suboesophageal ganglion of the Colorado potato beetle and the migratory locust three types of peptidergic neurosecretory cells were identified immunocytochemically with antisera to bovine pancreatic polypeptide, FMRFamide, vasopressin and alpha-MSH. Their locations and immunocytochemical reactions are similar, which suggests that these peptidergic cells in both insect species are homologous and perhaps have similar functions.

Animals↗
PubMed1995

The FMRFamide-related peptides F1 and F2 alter hemolymph distribution and cardiac output in the crab Cancer magister.

The FMRFamide-related peptides F1 and F2, originally isolated from lobster pericardial organs, have been shown to exert cardioexcitatory effects on isolated or semi-isolated crustacean hearts. The present study sought to determine the in vivo effects of F1 and F2 on cardiac and circulatory performance of Cancer magister using a pulsed-Doppler technique. In general the effects of F1 and F2 were similar; however, F1 was more potent and its effects were of longer duration than those exerted by F2. Infusion of either F1 or F2 caused a decrease in heart rate and subsequent periods of acardia. These decreases in rate occurred concurrently with a short-term increase in stroke volume of the heart, followed by a longer-term decrease in stroke volume. Hemolymph flow rates through the anterior aorta, anterolateral arteries, sternal artery, and posterior aorta also showed the same trend, with an initial short-term increase in flow rate followed by a longer-term decrease with periods of ischemia. Hemolymph flow through the paired hepatic arteries simply decreased, but recovery to pretreatment levels was faster than in the other arterial systems. Threshold for these responses occurred at circulating concentrations between 10(-9) mol.l-1 and 10(-8) mol.l-1 for F1 and somewhat higher, between 10(-8) mol.l-1 and 10(-7) mol.l-1, for F2.

Amino Acid Sequence↗
PubMed2001

FMRFamide-related neuropeptides are agonists of the orphan G-protein-coupled receptor GPR54.

We have isolated and determined the coding sequences of human and mouse orthologs of the rat orphan G-protein-coupled receptor GPR54. Mouse and rat GPR54 are nearly 95% identical to each other, and both are approximately 85% identical to human GPR54 at the amino acid level. Screening of agonists for GPR54 identified several invertebrate neuropeptides of the RFamide and RWamide family that were able to activate GPR54 at microM range through the G(alpha)q pathway. Substitution analysis showed that the C-terminal optimal sequence of GPR54-activating peptides is Gly-Leu-Arg-Trp-NH2. Northern analysis of human GPR54 detected expression in several peripheral tissues and many regions of the central nervous system.

Amino Acid Sequence↗
PubMed1994

N-terminally extended FMRFamide-related peptides of Helix aspersa: processing of the precursor protein and distribution of the released peptides.

Sequencing of cDNA clones reveals a precursor protein that can be processed into 10 different hepta-FaRPs. Two of the peptides are previously undescribed and are N-terminally extended forms of-YMRFamide, making them the only methionine-containing peptides in the precursor. They are separated from the main cluster of hepta-FaRPs by a recognition site (RQKR) for the Golgi-resident proteolytic enzyme furin. Antisera raised against the synthetic peptide KQDPFLRFGK specifically stain the clusters of neurons in the parietal ganglia that have been shown to contain hepta-FaRP mRNA. These antisera recognize two major protein bands of 35 and 23 kDa on immunoblots. Evidence is presented to identify the larger band as the precursor protein and the smaller band as the fragment containing the main cluster of hepta-FaRPs produced after furin cleavage. A series of immunostaining bands of 22-13 kDa suggests sequential and non-preferential N- or C-terminal cleavage at the mainly monobasic (K and R) sites that link all of the peptide sequences throughout the 23-kDa fragment, to yield the preamidated hepta-FaRPs. Immunostaining of sections shows punctate staining in the perikarya of the parietal cluster neurons commensurate with label within the endoplasmic reticulum and Golgi apparatus. Staining is followed through the axons to many fibers in the nerve trunks and is picked up as fine processes within the skin. These observations indicate that the antiserum used here recognizes one or more of the processed hepta-FaRPs, a view confirmed by radioimmunoassay. The abundance of immunoreactive fibers within the skin suggests a major role for the peptides in this tissue.

Amino Acid Sequence↗
PubMedDate not supplied

Enhanced antiopiate activity in peptidomimetics of FMRFamide containing Z-2,3-methanomethionine.

FMRFa is a molluscan peptide that has shown antiopiate activity in a number of mammalian test systems. The current study determined the antiopiate potency of FMRFa and two conformationally constrained peptidomimetics of FMRFa containing stereoisomers of Z-2,3-methanomethionine. Morphine abstinence signs were observed after varying doses (0.25-25.0 micrograms) of these substances were injected into the third ventricle of morphine-dependent rats. Although both peptidomimetics were far more potent than FMRFa itself, they bound with lower affinity than FMRFa to rat spinal cord receptors for the mammalian FMRFa-like peptide, NPFF.

Amino Acid Sequence↗
PubMedDate not supplied

Isolation of two FMRFamide-related peptides from crayfish pericardial organs.

Pericardial organs of the crayfish, Procambarus clarkii, were removed, and material from them was extracted and fractionated using two sequential reverse-phase HPLC columns. Fractions were analysed using a radioimmunoassay (RIA) specific for the C-terminal peptide sequence -Arg-Phe-NH2. The peak immunoreactive fraction from the second column appeared to contain two peptides with the sequences DRNFLRFamide and NRNFLRFamide, based on microsequencing analysis and on the absolute requirement for the amide in the RIA. These two peptides, respectively, have been given the names NF1 and DF2 due to similarity with previously identified lobster peptides F1 and F2. NF1 and DF2 are cardioexcitatory and augment synaptic transmission at a neuromuscular synapse, and evidence is presented for the calcium-dependent release of these peptides from the pericardial organs.

Amino Acid Sequence↗
PubMed1990

Dopamine and FMRFamide act directly on isolated gill muscle fibers in culture.

The peripheral nervous system (PNS) in the gill of Aplysia plays an important role in the mediation of adaptive gill withdrawal reflex (GWR) behaviors. It has proven difficult to determine whether or not neuronally active agents work directly on PNS neurons, the muscle or both. We have now been able to isolate individual gill muscle fibers in culture and thus begin an analysis of how endogenous neurotransmitters and/or neuromodulators act. We report here that both dopamine and FMRF-amide act directly on gill muscle fibers to cause contractions.

Animals↗
PubMed1994

Temperature dependence of synaptic modulation by a FMRFamide-related neuropeptide in crayfish.

The present study examined the temperature dependence of synaptic transmission and peptidergic modulation of chemical synapses on the phasic abdominal extensor muscles of crayfish. Decreasing the temperature from 25 degrees C to 5 degrees C in saline, decreased the EPSP amplitude by 88% and increased the EPSP half-decay time four-fold. The putative neurohormone DRNFLRFamide (DF2) increased EPSP amplitudes, but was more effective at 7-9 degrees C than at 15-17 degrees C. DF2 might play a hormonal role in counteracting low transmitter release at low temperature.

Amino Acid Sequence↗
PubMed1992

Effects of FMRFamide-related peptides and morphine on the isolated foregut of the locust Schistocerca gregaria.

1. Morphine and YAGFMamide were the most effective potentiators of 5-hydroxytryptamine (5-HT)-induced relaxation of the isolated foregut. 2. Morphine had no effect on proctolin-induced tissue contraction which was inhibited by YGGFMamide and YFMRFamide. 3. The differing potency of FaRPs and morphine to potentiate 5-HT effects and reduce proctolin responses suggests that there are two separate FaRP receptor sub types. 4. This proposal is supported by the observation that, while naloxone (10(-5) M) is a relatively potent antagonist of FaRP induced inhibition of proctolin contraction, it has less effect on FaRP-induced potentiation of 5-HT-induced relaxation.

Amino Acid Sequence↗
PubMed2005

Analysis of FMRFamide-like peptide (FLP) diversity in phylum Nematoda.

This study reports a series of systematic BLAST searches of nematode ESTs on the Genbank database, using search strings derived from known nematode FLPs (those encoded by Caenorhabditis elegans flp genes as well as those isolated from other nematodes including Ascaris suum), as well as query sequences representative of theoretical FLPs. Over 1000 putative FLP-encoding ESTs were identified from multiple nematode species. A total of 969 ESTs representing sequelogs of the 23 known C. elegans flp genes were identified in 32 species, from clades I, III, IV and V. Numerical analysis of EST numbers suggests that flp-1, flp-11 and flp-14 are amongst the most highly expressed flp genes. Speculative BLAST searches were performed using theoretical FLP C-termini as queries, in an attempt to identify putative novel FLP sequences in the EST database. These searches yielded eight multi-species sequelogs encoding FLPs with novel signatures that are believed to identify distinct flp genes. These novel genes encode 25 distinct previously unidentified FLPs, and raise the current total of known nematode flp genes to 31. Additionally, software-based analyses of the presence of signal peptides were performed, with signal peptides being identified on at least one member of each group of flp ESTs, further confirming their status as secreted peptides. The data reveal that nematode FLPs encompass the most complex neuropeptide family known within the metazoa. Moreover, individual FLPs and FLP motifs are highly conserved across the nematodes with little evidence for inter-clade or inter-lifestyle variation, supporting their fundamental role in free-living and parasitic species.

Amino Acid Sequence↗
PubMed2000

The range and biological activity of FMRFamide-related peptides and classical neurotransmitters in nematodes.

Nematodes include both major parasites of humans, livestock and plants in addition to free-living species such as Caenorhabditis elegans. The nematode nervous system (especially in C. elegans) is exceptionally well defined in terms of the number, location and projections of the small number of neurons in the nervous system and their integration into circuits involved in regulatory behaviours vital to their survival. This review will summarize what is known about the biological activity of neurotransmitters in nematodes: the biosynthetic pathways and genes involved, their receptors, inactivation mechanisms and secondary messenger signalling systems. It will cover the 'classical' transmitters, such as acetylcholine (ACh), GABA, glutamate, serotonin, dopamine, octopamine, noradrenaline and nitric oxide. The localization of peptides throughout the nematode nervous system is summarized, in addition to the isolation of nematode neuropeptides by both traditional biochemical techniques and more modern genetic means. The major contribution of the completion of the C. elegans genome-sequencing program is highlighted throughout. Efforts to unravel neurotransmitter action in various physiological actions such as locomotion, feeding and reproduction are detailed as well as the various inactivation mechanisms for the current complement of nematode transmitters.

Animals↗
PubMed1992

Relationships among the FMRFamide-like peptides.

The nuclear family of FaRPs (comprising those peptides that are, on compelling evidence, homologous) appears to be restricted to the protostome invertebrate phyla: i.e. Mollusca, Arthropoda, Annelida and Nematoda. Neither the origin nor the range of the family has been definitively established. That is, no genuine homologs have been demonstrated yet in the flatworms (though not for lack of trying), and neither the pseudocoelomate phyla related to the nematodes, nor the coelomate relatives of the annelids have been examined. The extended family of FaRPs (including peptides with little consistent sequence similarity beyond a penultimate Arg and an amidated hydrophobic residue at the C-terminal) exists in all phyla. Such a superfamily was probably first proposed by Morris et al. (1982), whose sequencing of SCPB suggested to them a class of peptides, "... the key unit for biological activity being Phe-A-Arg-B-amide (where A and B are also hydrophobic amino acids)." The ubiquity of the convergent FaRPs could reflect a conserved family of complementary heptahelical receptors requiring the arginyl residue for binding (Price and Greenberg, 1989). But another selective advantage would be the protection provided by a penultimate Arg against certain deamidating peptidases, found so far in yeast and mammals (Jackman et al., 1990).

Amino Acid Sequence↗