The Pharmacology of Nematode FMRFamide-related Peptides (original) (raw)
Related papers
Peptides, 1995
Isolation and preliminary biological characterization of KPNFlRFamide. a novel FMRFamide-related peptide from the free-living nematode, Panagrellus redivivus. PEPTIDES 16(l) 87-93, 1995-A novel FMRFamide-related heptapeptide, Lys-Pro-Asn-Phe-Be-Arg-Phe-NH2 (KPNFIRFamide), was isolated and characterized from acid ethanol extracts of the free-living nematode, Panagrellus redivivus. Whole-worm extracts contained zz 9 pmol KPNFIRFamide/g wet weight. A synthetic replicate of this peptide induced a rapid relaxation of tone and inhibited spontaneous contractility in isolated innervated and denervated body-wall muscle strips of the parasitic nematode, Ascaris suum. WNFIRFamide (0.1 n&f) induced measurable relaxations in 50% of the muscle preparations examined. Concentrations x= 0.3 nkf induced relaxation in 100% of muscle preparations examined. The relaxation was short-lived at concentrations of peptide 2 1 @4 and displayed a profile typical of receptor desensitization. These data suggest the occurrence of a closely related peptide in A. suum and add further evidence to the concept of primary structural conservation of FaRPs within the nematodes. Nematode peptides Ascaris suum Neuropeptides FMRFamide-related peptides KPNFIRFamide Panagrellus redivivus
FMRFamide-like peptides in root knot nematodes and their potential role in nematode physiology
Journal of Helminthology, 2009
FMRFamide-like peptides (FLPs) are a diverse group of neuropeptides that are expressed abundantly in nematodes. They exert potent physiological effects on locomotory, feeding and reproductive musculature and also act as neuromodulators. However, little is known about the specific expression patterns and functions of individual peptides. The current study employed rapid amplification of cDNA ends-polymerase chain reaction (RACE-PCR) to characterizeflpgenes from infective juveniles of the root knot nematodes,Meloidogyne incognitaandMeloidogyne minor. The peptides identified from these transcripts are sequelogs of FLPs from the free-living nematode,Caenorhabditis elegans; the genes have therefore been designated asMi-flp-1,Mi-flp-7,Mi-flp-12,Mm-flp-12andMi-flp-14.Mi-flp-1encodes five FLPs with the common C-terminal moiety, NFLRFamide.Mi-flp-7encodes two copies of APLDRSALVRFamide and APLDRAAMVRFamide and one copy of APFDRSSMVRFamide.Mi-flp-12andMm-flp-12encode the novel peptide KNNKFEF...
Pharmacology of FMRFamide-related Peptides in Helminths
Annals of the New York Academy of Sciences, 1999
Nervous systems of helminths are highly peptidergic. Species in the phylum Nematoda (roundworms) possess at least 50 FMRFamide-related peptides (FaRPs), with more yet to be identified. To date, few non-FaRP neuropeptides have been identified in these organisms, though evidence suggests that other families are present. FaRPergic systems have important functions in nematode neuromuscular control. In contrast, species in the phylum Platyhelminthes (flatworms) apparently utilize fewer FaRPs than do nematodes; those species examined possess one or two FaRPs. Other neuropeptides, such as neuropeptide F (NPF), play key roles in flatworm physiology. Although progress has been made in the characterization of FaRP pharmacology in helminths, much remains to be learned. Most studies on nematodes have been done with Ascaris suum because of its large size. However, thanks to the Caenorhabditis elegans genome project, we know most about the FaRP complement of this free-living animal. That essentially all C. elegans FaRPs are active on at least one A. suum neuromuscular system argues for conservation of ligand-receptor recognition features among the Nematoda. Structure-activity studies on nematode FaRPs have revealed that structure-activity relationship (SAR) "rules" differ considerably among the FaRPs. Second messenger studies, along with experiments on ionic dependence and anatomical requirements for activity, reveal that FaRPs act through many different mechanisms. Platyhelminth FaRPs are myoexcitatory, and no evidence exists of multiple FaRP receptors in flatworms. Interestingly, there are examples of cross-phylum activity, with some nematode FaRPs being active on flatworm muscle. The extent to which other invertebrate FaRPs show cross-phylum activity remains to be determined. How FaRPergic nerves contribute to the control of behavior in helminths, and are integrated with non-neuropeptidergic systems, also remains to be elucidated.
Arthropod FMRFamide-related peptides modulate muscle activity in helminths
International Journal for Parasitology, 2004
FMRFamide-related peptides are common to a wide variety of invertebrate species, including helminths and arthropods. In arthropods, five distinct FMRFamide-related peptide subfamilies are recognised: the myosuppressins, extended-FLRFamides, -FMRFamides, -RFamides, and sulfakinins, members of which induce potent and diverse myotropic effects. Whilst >80 FMRFamide-related peptides have been identified in nematodes, only four FMRFamide-related peptides have been characterised from flatworms. The Ascaris suum ovijector/body wall bioassay and the Procerodes littoralis muscle fibre bioassay have proved both reliable and sensitive systems for assessing the functional activities of FMRFamide-related peptides in vitro, and data describing the effects of native FMRFamide-related peptides in these systems are rapidly accumulating. This is the first study to determine the cross-phyla activities of non-native FMRFamide-related peptides in both nematode and flatworm species. In the present study, the effects of 10 arthropod FMRFamide-related peptides (leucomyosuppressin [pQDVDHVFLRFamide], schistoFLRFamide [PDVDHVFLRFamide] and truncated analogues [HVFLRFamide and VFLRFamide], lobster peptide I [TNRNFLRFamide], lobster peptide II [SDRNFLRFamide], manducaFLRFamide II [GNSFLRFamide], manducaFLRFamide III [DPSFLRFamide], calliFMRFamide 4 [KPNQDFMRFamide] and perisulfakinin [EQFDDY(SO(3)H)GHMRFamide]), representing the five subfamilies, were examined on the body wall and ovijector of the parasitic porcine nematode, A. suum and dispersed muscle fibres from the free-living turbellarian, P. littoralis. The muscle activity of the ovijector was found to be modulated significantly by each of the arthropod FMRFamide-related peptides tested; the effects were concentration-dependent, reversible and repeatable. All but one (perisulfakinin) of the 10 arthropod FMRFamide-related peptides examined modulated significantly the activity of A. suum body wall muscle. In addition, all of the arthropod FMRFamide-related peptides examined induced potent concentration-dependent contractions of P. littoralis muscle fibres. These results reveal similarities in the ligand requirement(s) between FMRFamide-related peptide receptors within the Phyla Arthropoda, Nematoda and Platyhelminthes, and indicate significant receptor promiscuity, which highlights the potential of FMRFamide-related peptide receptors as legitimate targets for novel endectocidal agents.
International Journal for Parasitology, 1995
The chemotherapeutic control of helminth parasites is compromised by the limited number of classes of anthelmintic drugs. Discovery of novel anthelmintics is impeded by the lack of novel screening technologies that overcome the difficulties inherent in screens based on whole organism toxicity. The development and implementation of mechanism-based screens for new anthelmintics offers great promise for the revitalization of antiparasitic
Inhibitory effects of nematode FMRFamide-related peptides (FaRPs) on muscle strips fromAscaris suum
Invertebrate Neuroscience, 1995
A large number of FMRFamide-related peptides (FaRPs) are found in nematodes, and some of these are known to influence tension and contractility of neuromuscular strips isolated from Ascaris suum body wall. Relaxation of these strips has been noted with five nematode FaRPs. The inhibitory actions of SDPNFLRFamide (PF1) and SADPNFLRFamide (PF2) appear to be mediated by nitric oxide, as previously demonstrated with inhibitors of nitric oxide synthase (NOS). This present study showed that the effects of PF1 were also dependent on external Ca ++ and were reduced by the Ca++-channel blocker verapamil, observations consistent with the finding that nematode NOS is Ca++-dependent. KSAYMRFamide (PF3), KPNFIRFamide (PF4) and KNAFIRFamide (an alanine substituted analog of KNEFIRFamide, AF1, termed A3AF1) also relaxed A. suum muscle strips, but these responses were not affected by NOS inhibitors. PF3 inhibited the activity of strips prepared from the dorsal side of the worm, but contracted ventral strips. Both effects were dependent on the presence of ventral/dorsal nerve cords (unlike PF1/PF2) and were attenuated in medium which contained high K + or low Ca ++. PF4-induced muscle relaxation and hyperpolarization were independent of nerve cords, but were reversed in Cl'-free medium, unlike PF1 or PF3. The PF4 effect physiologically desensitized muscle strips to subsequent treatment with PF4 and/or GABA. However, PF4 and GABA were not synergistic in this preparation. The effects of GABA, but not PF4, were reduced in muscle strips treated with the GABA antagonist, NCS 281-93. Following PF4 (or GABA) relaxation, subsequent treatment with higher doses of PF4 caused muscle strip contraction. A3AF1 was found to relax muscle strips and hyperpolarize muscle cells independently of the ventral and dorsal nerve cords, K +, Ca ++, and CI-, and mimicked the inhibitory phase associated with the exposure of these strips to AF1. On the basis of anatomical and ionic dependence, these data have delineated at least four distinct inhibitory activities attributable to nematode FaRPs. Clearly, a remarkably complex set of inhibitory mechanisms operate in the nematode neuromuscular system.
Peptides, 1996
Structure-activity relationships of KNEFIRFamide (AFl), a nematode FMRFamide-related peptide, on Ascaris suum muscle. PEF'I'IDES 17(3) 381-387, 1996.-Analogues of KNEFIRFamide (Lys-Asn-Glu-Phe-Ile-Arg-Phe-NH2; AFl), an FMRFamide-related peptide (FaRP) originally isolated from Ascaris suum, were characterized in an A. suum muscle tension assay. AFI had biphasic effects on this preparation, inducing a brief relaxation followed by excitation and spastic paralysis. Activity of AFl in this assay was eliminated by N-terminal deletions and by deamidation of the carboxy-terminus. The potency of AFl was greatly reduced by alanine substitution for any residue. Peptides that retained activity did not show the biphasic response observed with AFl, suggesting that the inhibitory and excitatory phases seen with AFl may be due to activation of distinct receptors. The basis for the marked differences in potency observed between AFl and the structurally related nematode FaRP, AF2 (KHEYLRFamide) was also tested. AF2 is approximately lOOO-fold more potent than AFl in this assay, but has physiological effects that are otherwise indistinguishable. KNEYIRFamide and KNEFL~amide induced characteristic AFI /AR responses, but were much less potent than the native peptides. In contrast, KHEYIRFamide resembled AFl in potency and pattern of responses. These data suggest that AFl and AF2 act at distinct receptors, an hypothesis supported by the observation that KNEwamide antagonized the effects of AFl but not of AF2.
Annals of the New York Academy of Sciences, 1999
The endogenous nematode peptides known as FMRFamide-related peptides (FaRPs) and various "classical" transmitters have a range of effects on nematodes that result in changes in behavior, particulary locomotion, including paralysis and inhibition of feeding. This study describes the application of an in vitro pharmacological approach to further delineate the action of a number of FaRP neurotransmitters on feeding behavior. Contraction of Ascaris suum pharyngeal muscle was monitored using a modified pressure transducer system that detects changes in intrapharyngeal pressure and therefore contraction of the radial muscle of the pharynx. The pharynx did not contract spontaneously. However, serotonin (5-HT, 100 mM) stimulated rhythmic contractions and relaxations (pumping) at a frequency of 0.5 Hz. The native nematode peptide, KNEFIRFamide (AF1), inhibited the pumping elicited by 5-HT. The duration of inhibition was concentration-dependent (1-1000 nM) with a threshold of 1 nM (n = 7). KSAYMRFamide (AF8/PF3) also inhibited pharyngeal pumping. There was no observable effect of any of the following nematode peptides on pharyngeal pumping behavior (1-1000 nM; n = 8): AF2, AF3, AF4, AF6, AF16, PF1/CF1, PF2/CF2, or PF4. Thus, interruption of pharyngeal processes, such as feeding, regulation of hydrostatic pressure, and secretion, may provide a new site of anthelmintic action.
European Journal of Neuroscience, 1996
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, Ill-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 spectromettythe 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. lmmunoreactive neurons included the single identifiable visceral white interneuron (VWI or VD4), a key cell of the cardiorespiratory network.