The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform
Angela B. Lange - One of the best experts on this subject based on the ideXlab platform.
-
the Proctolin gene and biological effects of Proctolin in the blood feeding bug rhodnius prolixus
Frontiers in Endocrinology, 2011Co-Authors: Ian Orchard, Do Hee Lee, Rosa Da Silva, Angela B. LangeAbstract:We have reinvestigated the possible presence or absence of the pentapeptide Proctolin in Rhodnius prolixus and report here the cloning of the Proctolin cDNA. The transcript is highly expressed in the central nervous system (CNS) with some low expression associated with peripheral tissues. The Proctolin prepropeptide encodes a single copy of Proctolin along with a Proctolin-precursor-associated peptide. We have biochemically identified Proctolin in CNS extracts and shown its distribution using Proctolin-like immunoreactivity. Immunostained processes are found on the salivary glands, female and male reproductive organs, and heart and associated alary muscles. Proctolin-like immunoreactive bipolar neurons are found on the lateral margins of the common oviduct and bursa. Proctolin is biologically active on R. prolixus tissues, stimulating increases in contraction of anterior midgut and hindgut muscles, and increasing heartbeat frequency. Contrary to the previous suggestion that Proctolin is absent from R. prolixus, Proctolin is indeed present and biologically active in this medically-important bug.
-
Proctolin a possible releasing factor in the corpus cardiacum corpus allatum of the locust
Peptides, 2006Co-Authors: Lisa Clark, J R Zhang, Stephen S. Tobe, Angela B. LangeAbstract:Abstract The corpus cardiacum (CC) and corpus allatum (CA) of the locust, Locusta migratoria , contain intense Proctolin-like immunoreactivity (PLI) within processes and varicosities. In contrast, in the cockroach, Diploptera punctata , although a similar staining pattern occurs within the CC, PLI appears absent within the CA. The possible role of Proctolin as a releasing factor for adipokinetic hormone (AKH) and juvenile hormone (JH) was investigated in the locust. Proctolin caused a dose-dependent increase in AKH I release (determined by RP-HPLC) from the locust CC over a range of doses with threshold above 10 −8 M and maximal release at about 10 −7 M Proctolin. Isolated glandular lobes of the CC released greater amounts of AKH I following treatment with Proctolin and in these studies AKH II was also released. Confirmation of AKH I release was obtained by injecting perfusate from incubated CCs into locusts and measuring hemolymph lipid concentration. Perfusate from CC incubated in Proctolin contained material with similar biological activity to AKH. Proctolin was also found to significantly increase the synthesis and release of JH from locust CA, with the increase being greatest from CAs that had a relatively low basal rate of JH biosynthesis ( −1 per CA). In contrast, Proctolin did not alter the synthesis and release of JH from the cockroach CA. These results suggest that Proctolin may act as a releasing factor for AKHs and JH in the locust but does not act as a releasing factor for JH in the cockroach.
-
a review of the involvement of Proctolin as a cotransmitter and local neurohormone in the oviduct of the locust locusta migratoria
Peptides, 2002Co-Authors: Angela B. LangeAbstract:Abstract The pentapeptide Proctolin, originally identified in the cockroach, has been shown to be widely distributed in many insects and to have a broad range of physiological functions. In the oviduct of the locust, Locusta migratoria , Proctolin’s role as a neurotransmitter/neuromodulator has been well documented; however, a neurohormonal role in the locust is less certain. This review will examine the various roles of Proctolin in locust oviduct contraction and will present evidence that a substance chromatographically, immunologically and physiologically indistinguishable from Proctolin is present in the hemolymph of the locust, L. migratoria . This material is concentrated in the plasma, rather than the hemocytes, and is present at concentrations ranging from 0.1 to 0.2 nM. This review extends the role of Proctolin in insects, and suggests that Proctolin may play a neurohormonal role in the locust.
-
Interaction between octopamine and Proctolin on the oviducts of Locusta migratoria.
Journal of insect physiology, 2000Co-Authors: David A. Nykamp, Angela B. LangeAbstract:The biogenic amine octopamine and the pentapeptide Proctolin are two important neuroactive chemicals that control contraction of the oviducts of the African locust Locusta migratoria. The physiological responses and signal transduction pathways used by octopamine and Proctolin have been well characterized in the locust oviducts and this therefore provides the opportunity to examine the interaction between these two pathways. Octopamine, via the intracellular messenger adenosine 3′,5′-cyclic monophosphate (cyclic AMP), inhibits contraction of the oviducts, while Proctolin, via the phosphoinositol pathway, stimulates contraction. We have examined the physiological response of the oviducts to combinations of octopamine and Proctolin and also looked at how combinations of these affect one of the main intracellular mediators of the octopamine response, namely cyclic AMP. It was found that application of octopamine to the oviducts led to a dose-dependent reduction in tonus of the muscle and also a decrease in the amplitude and frequency of spontaneous phasic contractions. Octopamine-induced relaxation was enhanced in the presence of the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX). Octopamine was also able to inhibit Proctolin-induced contractions of the oviducts in a dose-dependent manner. A 10−9 M Proctolin-induced contraction was inhibited by 83% in the presence of 10−5 M octopamine, and was completely inhibited in the presence of 10−5 M octopamine plus 5×10−4 M IBMX. Octopamine led to a dose-dependent increase in cyclic AMP content as measured by radioimmunoassay. In the presence of 10−9 M Proctolin, this octopamine-induced increase in cyclic AMP was reduced by as much as 60%. Proctolin also caused a dose-dependent decrease in the cyclic AMP elevation produced by 5×10−6 M octopamine. These results indicate that octopamine and Proctolin can antagonize each other's physiological response when added in combination, and that Proctolin is able to modulate the response of the oviducts to octopamine by influencing cyclic AMP levels.
-
comparison of the myotropic activity of position 2 modified analogues of Proctolin on the hindgut of periplaneta americana and the oviduct of locusta migratoria
Journal of Insect Physiology, 1997Co-Authors: Alvin N Starratt, Angela B. Lange, Ian Orchard, Robert W SteeleAbstract:Abstract The largest series of position-2 modified Proctolin analogues to have been examined to date were tested for their ability to mimic the basal contraction induced by Proctolin on hindgut of the cockroach, Periplaneta americana, and oviduct of the locust, Locusta migratoria . Twelve analogues of Proctolin (Arg-Tyr-Leu-Pro-Thr), differing in the substituent (H, OMe, OEt, OPr, F, Cl, Br, I, NO 2 , NH 2 , N 3 , Me) located at the para -position of the aromatic amino acid, caused dose-dependent contractions of both tissues at concentrations quite similar to Proctolin. Seven showed greater or equal potency on the hindgut but, with one exception, they were less active on the oviduct than Proctolin. The rank order of potency of the analogues depends on the tissue, lending more support to the notion that insects have more than one type of Proctolin receptor. No relationship was observed between myoactivity and lipophilic, steric, electron donating or electron withdrawing properties of the substituents at the para -position of the aromatic amino acid. This may be the result of more than one sub-type of Proctolin receptor on the specific tissue with differing structural requirements for optimum activity.
Ian Orchard - One of the best experts on this subject based on the ideXlab platform.
-
the Proctolin gene and biological effects of Proctolin in the blood feeding bug rhodnius prolixus
Frontiers in Endocrinology, 2011Co-Authors: Ian Orchard, Do Hee Lee, Rosa Da Silva, Angela B. LangeAbstract:We have reinvestigated the possible presence or absence of the pentapeptide Proctolin in Rhodnius prolixus and report here the cloning of the Proctolin cDNA. The transcript is highly expressed in the central nervous system (CNS) with some low expression associated with peripheral tissues. The Proctolin prepropeptide encodes a single copy of Proctolin along with a Proctolin-precursor-associated peptide. We have biochemically identified Proctolin in CNS extracts and shown its distribution using Proctolin-like immunoreactivity. Immunostained processes are found on the salivary glands, female and male reproductive organs, and heart and associated alary muscles. Proctolin-like immunoreactive bipolar neurons are found on the lateral margins of the common oviduct and bursa. Proctolin is biologically active on R. prolixus tissues, stimulating increases in contraction of anterior midgut and hindgut muscles, and increasing heartbeat frequency. Contrary to the previous suggestion that Proctolin is absent from R. prolixus, Proctolin is indeed present and biologically active in this medically-important bug.
-
the muscular contractions of the midgut of the cockroach diploptera punctata effects of the insect neuropeptides Proctolin and leucomyosuppressin
Regulatory Peptides, 1998Co-Authors: M Fuse, Ian OrchardAbstract:We have previously shown differential expression of leucomyosuppressin (LMS) mRNA in apparent endocrine cells in the anterior region of midguts of the cockroach Diploptera punctata, using in situ hybridization. In contrast, other FMRFamide-related peptides, as revealed by immunohistochemistry, have been found most abundantly in the posterior region in both apparent endocrine cells and nerve tracts (1). Here, we partially purified extracts of anterior and posterior cockroach midguts, using HPLC coupled with radioimmunoassay, and found, among multiple FMRFamide-like immunoreactive fractions, one fraction co-eluting with LMS in both regions. The presence of a co-eluting fraction in the posterior region, in the absence of LMS mRNA positive endocrine cells suggests that LMS might therefore be present in nerve tracts running along the length of the midgut. Using a circular muscle contraction assay from different portions of midgut, we determined the effects of LMS, Proctolin and a variety of other midgut peptides on contractions of the midgut of Diploptera. Proctolin caused a sustained tonic contraction in the anterior midgut, the amplitude of which was dose-dependent. In contrast, LMS, and its relative SchistoFLRFamide, reduced the amplitude of these contractions. LMS and SchistoFLRFamide also inhibited spontaneous phasic contractions, which were elicited by Proctolin application in only a few preparations. Other postulated midgut peptides did not induce or inhibit contractions, nor augment the Proctolin-induced contractions. The C-terminal truncated sequences of LMS, HVFLRFamide and VFLRFamide, were sufficient to reduce the amplitude of the Proctolin-induced contractions. This work illustrates a possible physiological role for LMS in Diploptera midguts, in the passage of food along the alimentary canal. © 1998 Elsevier Science B.V. All rights reserved.
-
comparison of the myotropic activity of position 2 modified analogues of Proctolin on the hindgut of periplaneta americana and the oviduct of locusta migratoria
Journal of Insect Physiology, 1997Co-Authors: Alvin N Starratt, Angela B. Lange, Ian Orchard, Robert W SteeleAbstract:Abstract The largest series of position-2 modified Proctolin analogues to have been examined to date were tested for their ability to mimic the basal contraction induced by Proctolin on hindgut of the cockroach, Periplaneta americana, and oviduct of the locust, Locusta migratoria . Twelve analogues of Proctolin (Arg-Tyr-Leu-Pro-Thr), differing in the substituent (H, OMe, OEt, OPr, F, Cl, Br, I, NO 2 , NH 2 , N 3 , Me) located at the para -position of the aromatic amino acid, caused dose-dependent contractions of both tissues at concentrations quite similar to Proctolin. Seven showed greater or equal potency on the hindgut but, with one exception, they were less active on the oviduct than Proctolin. The rank order of potency of the analogues depends on the tissue, lending more support to the notion that insects have more than one type of Proctolin receptor. No relationship was observed between myoactivity and lipophilic, steric, electron donating or electron withdrawing properties of the substituents at the para -position of the aromatic amino acid. This may be the result of more than one sub-type of Proctolin receptor on the specific tissue with differing structural requirements for optimum activity.
-
evidence for Proctolin like and rfamide like neuropeptides associated with the hindgut of the crayfish procambarus clarkii
Canadian Journal of Zoology, 1997Co-Authors: Joffre A Mercier, Angela B. Lange, Victoria Tebrugge, Ian OrchardAbstract:Immunohistochemical staining revealed Proctolin-like immunoreactivity in nerve endings associated with the hindgut of the crayfish Procambarus clarkii. Proctolin-like bioactivity, detected using both locust oviducts and crayfish hindguts for bioassays, co-eluted with authentic Proctolin through five consecutive reversed-phase high-performance liquid chromatography (RP-HPLC) systems. This strongly suggests that Proctolin (or a peptide very similar to it) is contained in nerve endings on the crayfish hindgut. RFamide-like immunoreactivity (RFLI) was extracted from the hindguts and intestinal nerves of crayfish and separated using RP-HPLC. Initial separation on a C18 column gave a broad peak of RFLI, and these fractions were bioactive on the crayfish hindgut. Subsequently, RFLI was separated on two additional RP-HPLC systems. The predominant peak could be distinguished from FMRFamide and several known FMRFamide-like peptides on the basis of elution times. Partial sequence analysis indicated the presence of a decapeptide having some sequence homology with leucomyosuppressin and SchistoFLRFamide. These results support earlier evidence that extended RFamide peptides may function as neurotransmitters or neuromodulators on the crayfish hindgut,
-
the effects of selected Proctolin analogues on contractions of locust locusta migratoria oviducts
Journal of Insect Physiology, 1993Co-Authors: Angela B. Lange, Ian Orchard, Danuta KonopińskaAbstract:We have examined the ability of some selected Proctolin analogues to mimic the basal contraction induced by Proctolin (Arg-Tyr-Leu-Pro-Thr) on a locust oviduct. The criterion of agonist-induced basal contraction was used to construct dose-response relationships for these selected analogues. Three of the analogues were modified in the [Tyr2]-position, two were modified in the [Arg1]-position, and one was a tetrapeptide lacking the N-terminal arginine, Tyr(3′-NH2)-Leu-Pro-Thr. All were chosen because of their differing rank orders of activity on two other insect preparations. [l-Dopa2]Proctolin, [Phe(pNH2)2]Proctolin and [Phe(pNMe2)2]Proctolin were all capable of mimicking Proctolin, as too were [Lys1]Proctolin and [homo-Arg1]Proctolin, although with varying thresholds, half-maxima and maxima. The tetrapeptide was a very poor agonist, resulting in only a minor basal contraction at the high dose of 10−5 M. The rank orders, based upon doses required for half-maxima and maximal contraction were different from either a cockroach heart or a mealworm heart. The results support the suggestion for subtypes of Proctolin receptors within insects, and indicate that these analogues may be useful tools for comparing these sub-types.
B.g. Loughton - One of the best experts on this subject based on the ideXlab platform.
-
Pharmacological studies of Proctolin receptors on foregut and hindgut of Blaberus craniifer.
Peptides, 1998Co-Authors: C Mazzocco-manneval, Mariola Kuczer, Danuta Konopińska, B Fournier, B.g. Loughton, J PuirouxAbstract:Proctolin (Arg-Tyr-Leu-Pro-Thr) and Proctolin analogs modified at position 1, 2, or 5 caused dose dependent contractions of Blaberus fore- and hindgut. The varying contractile effects between both tissues revealed the possible presence of receptor subtypes as identified by [GABA1]-Proctolin. A single population of binding sites (Kd approximately 100 nM) was deduced from Scatchard analysis. In addition, nanomolar concentrations of Proctolin induced a dose-dependent hydrolysis of phosphoinositides (PIns) augmented by GTPgammaS (1 microM) on foregut membranes but no accumulation of cAMP. Proctolin induced contractions are likely mediated via a phospholipase C linked to a heptahelical receptor bound to heterotrimeric G-proteins.
-
the effect of substitutions at position three on the binding and bioactivity of Proctolin in locust hindgut and oviduct
Insect Biochemistry and Molecular Biology, 1995Co-Authors: L E King, V M Sevala, B.g. LoughtonAbstract:A number of Proctolin analogs modified at position three were analyzed for their relative binding affinities and biological activity on locust hindgut and oviduct. A decrease in chain length at this position (from Leu, Ile to Val) or an increase in hydrophobicity alone (Glu) or combined with a decrease in chain length (Val, Ser, Thr and Asp) decreased bioactivity but not necessarily binding. (Ser3)-Proctolin had a higher affinity than Proctolin for both hindgut and oviduct membranes but was less biologically active than Proctolin in both tissues. Several other analogs bound with a similar affinity to Proctolin but were significantly less biologically active, particularly on locust oviduct. These results suggest that the position three leucine of Proctolin is more important for bioactivity than for binding in both oviduct and hindgut. The data also suggest the presence of two Proctolin receptor subtypes on oviduct but not on hindgut membranes. Position three Proctolin analogs may be useful in more precisely distinguishing these subtypes.
-
the effect of Proctolin analogues and other peptides on locust oviduct muscle contractions
Peptides, 1993Co-Authors: Jacques Puiroux, Anne Pedelaborde, B.g. LoughtonAbstract:Abstract The locust oviduct bioassay system was used to assess the ability of a variety of peptides to induce oviducal contractions. Proctolin analogues were three orders of magnitude less potent than Proctolin. Proctolin supra-analogue and Arg-Tyr-Leu-Ala-Thr demonstrated high activity. Perhaps the most significant finding was the discrepancy between the high binding capacity of the Proctolin analogue Arg-Tyr-Ser-Pro-Thr and its relatively low myotropic activity. This observation argues for a crucial role for the leucine residue in activating the Proctolin receptor. Several other myotropic peptides were tested for their effect on oviduct contractions. FMRFamide caused contractions at doses several orders of magnitude higher than Proctolin. The FLRFamide leucomyosuppressin inhibited Proctolin-induced contractions. In addition, myomodulin and catch relaxing peptide caused oviducal contractions at low concentrations. The enkephalins had no effect when applied alone but potentiated Proctolin-induced oviduct contractions. The mechanism of the potentiation is not known. The data argue for the presence of several binding sites on the oviduct membrane.
-
characterization of Proctolin binding sites on locust oviduct membranes
Insect Biochemistry and Molecular Biology, 1992Co-Authors: Jacques Puiroux, Anne Pedelaborde, B.g. LoughtonAbstract:Abstract The binding of [ 3 H]Proctolin to oviduct membranes has been analyzed to investigate the nature of Proctolin binding sites in the oviduct. Proctolin binding was found to be time dependent, proportional to concentration of membrane protein, saturable, specific and reversible. Two apparent Proctolin binding sites were recognized. The first had a K d of 400 ± 82 nM and a B max of 23.7 ± 6.7 pmol/mg protein. The second had a K d of 2.4 ± 0.2 μ M and a B max of 96.3 ± 16.7 pmo/mg protein. Binding was specific in thatcompetition experiments with a wide range of peptides showed that only Arg-Tyr-Leu-Pro-Ala was an effective competitor at μM concentrations. All other peptides examined weekly reduced Proctolin binding at concentrations above 50 μM. Certain peptides were found to potentiate [ 3 ]pProctolin binding at low μM concentrations (1–10 μM) and to inhibit Proctolin binding at higher concentrations. The significance of these findings is discussed.
-
characterization of a Proctolin binding site on locust hindgut membranes
Insect Biochemistry and Molecular Biology, 1992Co-Authors: Jacques Puiroux, Anne Pedelaborde, B.g. LoughtonAbstract:Abstract The binding of [ 3 H]Proctolin to hindgut membranes of the locust was investigated. Specific Proctolin binding was found to be time dependent, proportional to membrane protein concentration, saturable and reversible. Scatchard analysis of the binding data allowed the calculation of a dissociation constant ( K d of 96 ± 8 nM and a maximum binding capacity ( B max of 3.37 ± 0.44 pmol/mg membrane protein. Competition studies with a number of small neuropeptides revealed that FMRF-amide, Met-enkephalin-RF and Leu-enkephalin could compete with Proctolin at concentrations two orders of magnitude greater than Proctolin itself. By contrast, Met-enkephalin did not compete effectively with Proctolin. Two antagonists of Proctolin action, leucomyosuppressin (LMS) and SchistoFLRF -amide had no effect on Proctolin binding at high concentrations which suggests that SchistoFLRF-amide acts at a different receptor site to Proctolin. This is the first study of Proctolin binding to visceral membrane preparations.
Jacques Puiroux - One of the best experts on this subject based on the ideXlab platform.
-
purification of Proctolin binding proteins from the foregut of the insect blaberus craniifer
FEBS Journal, 2000Co-Authors: Claire Mazzocco, Jacques PuirouxAbstract:A membrane protein that specifically binds the insect neuropeptide Proctolin was purified using standard chromatography from cockroach foregut membranes. Proctolin-binding sites were efficiently solubilized with either the nonionic detergent digitonin or the zwitterionic detergent Chaps, as indicated by the specific binding of 3H-Proctolin to solubilized samples. A solubilized sample obtained from 1600 foregut membranes was subjected to a five-step chromatographic purification including chromatofocusing, anion-exchange and size-exclusion chromatographies. The final size-exclusion separation resulted in the isolation of approximately 100 pmol of purified Proctolin-binding proteins, eluting as a single peak at approximately 74 kDa. Analysis of the purified sample using SDS/PAGE and silver staining showed two bands at 80 kDa and 76 kDa. Densitometric analysis of the gel indicated that each band contained approximately 7-8 microg of protein, suggesting that one band corresponds to the Proctolin-binding activity. Proctolin-binding proteins were thus purified 1800-fold using standard chromatography.
-
the effect of Proctolin analogues and other peptides on locust oviduct muscle contractions
Peptides, 1993Co-Authors: Jacques Puiroux, Anne Pedelaborde, B.g. LoughtonAbstract:Abstract The locust oviduct bioassay system was used to assess the ability of a variety of peptides to induce oviducal contractions. Proctolin analogues were three orders of magnitude less potent than Proctolin. Proctolin supra-analogue and Arg-Tyr-Leu-Ala-Thr demonstrated high activity. Perhaps the most significant finding was the discrepancy between the high binding capacity of the Proctolin analogue Arg-Tyr-Ser-Pro-Thr and its relatively low myotropic activity. This observation argues for a crucial role for the leucine residue in activating the Proctolin receptor. Several other myotropic peptides were tested for their effect on oviduct contractions. FMRFamide caused contractions at doses several orders of magnitude higher than Proctolin. The FLRFamide leucomyosuppressin inhibited Proctolin-induced contractions. In addition, myomodulin and catch relaxing peptide caused oviducal contractions at low concentrations. The enkephalins had no effect when applied alone but potentiated Proctolin-induced oviduct contractions. The mechanism of the potentiation is not known. The data argue for the presence of several binding sites on the oviduct membrane.
-
characterization of Proctolin binding sites on locust oviduct membranes
Insect Biochemistry and Molecular Biology, 1992Co-Authors: Jacques Puiroux, Anne Pedelaborde, B.g. LoughtonAbstract:Abstract The binding of [ 3 H]Proctolin to oviduct membranes has been analyzed to investigate the nature of Proctolin binding sites in the oviduct. Proctolin binding was found to be time dependent, proportional to concentration of membrane protein, saturable, specific and reversible. Two apparent Proctolin binding sites were recognized. The first had a K d of 400 ± 82 nM and a B max of 23.7 ± 6.7 pmol/mg protein. The second had a K d of 2.4 ± 0.2 μ M and a B max of 96.3 ± 16.7 pmo/mg protein. Binding was specific in thatcompetition experiments with a wide range of peptides showed that only Arg-Tyr-Leu-Pro-Ala was an effective competitor at μM concentrations. All other peptides examined weekly reduced Proctolin binding at concentrations above 50 μM. Certain peptides were found to potentiate [ 3 ]pProctolin binding at low μM concentrations (1–10 μM) and to inhibit Proctolin binding at higher concentrations. The significance of these findings is discussed.
-
characterization of a Proctolin binding site on locust hindgut membranes
Insect Biochemistry and Molecular Biology, 1992Co-Authors: Jacques Puiroux, Anne Pedelaborde, B.g. LoughtonAbstract:Abstract The binding of [ 3 H]Proctolin to hindgut membranes of the locust was investigated. Specific Proctolin binding was found to be time dependent, proportional to membrane protein concentration, saturable and reversible. Scatchard analysis of the binding data allowed the calculation of a dissociation constant ( K d of 96 ± 8 nM and a maximum binding capacity ( B max of 3.37 ± 0.44 pmol/mg membrane protein. Competition studies with a number of small neuropeptides revealed that FMRF-amide, Met-enkephalin-RF and Leu-enkephalin could compete with Proctolin at concentrations two orders of magnitude greater than Proctolin itself. By contrast, Met-enkephalin did not compete effectively with Proctolin. Two antagonists of Proctolin action, leucomyosuppressin (LMS) and SchistoFLRF -amide had no effect on Proctolin binding at high concentrations which suggests that SchistoFLRF-amide acts at a different receptor site to Proctolin. This is the first study of Proctolin binding to visceral membrane preparations.
-
degradation of the neuropeptide Proctolin by membrane bound proteases of the hindgut and ovary of locusta migratoria and the effects of different inhibitors
Archives of Insect Biochemistry and Physiology, 1992Co-Authors: Jacques Puiroux, B.g. LoughtonAbstract:Proctolin was incubated in vitro with crude membrane preparations derived from hind gut and ovary of Locusta migratoria. The metabolites of Proctolin were separated and identified by reversed phase-high performance liquid chromatography which allowed the determination of the time course of degradation. At pHs 9.2 and 7.4, aminopeptidase activity predominated but some evidence of a carboxypeptidase could be inferred. At pH 6, aminopeptidase activity was slightly reduced compared to the level of aminopeptidase activity at the two former pHs; by contrast the carboxypeptidase was more important. At this pH, the presence of a membrane bound endopeptidase was detected. Phenanthroline, actinonin, amastatine, bestatin, and (2S,3R)-3-amino-2-hydroxy-4-(4-nitrophenyl)-butanoyl-L-leucine (HNBL) were tested at the concentration of 0.1 mM at pHs 8.2 and 6 and their ability to prevent the degradation of Proctolin was estimated. A both pHs, HNBL and amastatin were revealed to be the most efficient inhibitors (50 to 75% inhibition) and o-phenanthroline appeared particularly efficacious at pH 6 (70% inhibition), whereas it was relatively poor inhibitor at pH 8.2. Furthermore, the use of these inhibitors confirmed the importance of carboxypeptidase activity at pH 6. These data are the first to describe Proctolin degradation in ovary and hindgut muscle, important targets of Proctolin action.
Vanessa Rioli - One of the best experts on this subject based on the ideXlab platform.
-
des arg 1 Proctolin a novel nep like enzyme inhibitor identified in tityus serrulatus venom
Peptides, 2016Co-Authors: Bruno Duzzi, Daniela Cajadocarvalho, Alexandre Kazuo Kuniyoshi, Roberto Tadashi Kodama, Fabio C Gozzo, Mariana Fioramonte, Denise V Tambourgi, Fernanda C V Portaro, Vanessa RioliAbstract:The scorpion Tityus serrulatus venom comprises a complex mixture of molecules that paralyzes and kills preys, especially insects. However, venom components also interact with molecules in humans, causing clinic envenomation. This cross-interaction may result from homologous molecular targets in mammalians and insects, such as (NEP)-like enzymes. In face of these similarities, we searched for peptides in Tityus serrulatus venom using human NEP as a screening tool. We found a NEP-inhibiting peptide with the primary sequence YLPT, which is very similar to that of the insect neuropeptide Proctolin (RYLPT). Thus, we named the new peptide [des-Arg(1)]-Proctolin. Comparative NEP activity assays using natural substrates demonstrated that [des-Arg(1)]-Proctolin has high specificity for NEP and better inhibitory activity than Proctolin. To test the initial hypothesis that molecular homologies allow Tityus serrulatus venom to act on both mammal and insect targets, we investigated the presence of a NEP-like in cockroaches, the main scorpion prey, that could be likewise inhibited by [des-Arg(1)]-Proctolin. Indeed, we detected a possible NEP-like in a homogenate of cockroach heads whose activity was blocked by thiorphan and also by [des-Arg(1)]-Proctolin. Western blot analysis using a human NEP monoclonal antibody suggested a NEP-like enzyme in the homogenate of cockroach heads. Our study describes for the first time a Proctolin-like peptide, named [des-Arg(1)]-Proctolin, isolated from Tityus serrulatus venom. The tetrapeptide inhibits human NEP activity and a NEP-like activity in a cockroach head homogenate, thus it may play a role in human envenomation as well as in the paralysis and death of scorpion preys.
