[Show abstract][Hide abstract] ABSTRACT: The neuropeptide Pigment-Dispersing Factor (PDF) is a principle transmitter regulating circadian locomotor rhythms in Drosophila. We have identified a Class II (secretin-related) G protein-coupled receptor (GPCR) that is specifically responsive to PDF and also to calcitonin-like peptides and to PACAP. In response to PDF, the PDF receptor (PDFR) elevates cAMP levels when expressed in HEK293 cells. As predicted by in vivo studies, cotransfection of Neurofibromatosis Factor 1 significantly improves coupling of PDFR to adenylate cyclase. pdfr mutant flies display increased circadian arrhythmicity, and also display altered geotaxis that is epistatic to that of pdf mutants. PDFR immunosignals are expressed by diverse neurons, but only by a small subset of circadian pacemakers. These data establish the first synapse within the Drosophila circadian neural circuit and underscore the importance of Class II peptide GPCR signaling in circadian neural systems.
[Show abstract][Hide abstract] ABSTRACT: We cloned and characterized an orphan FMRFamide-related peptide (FaRP) GPCR in Caenorhabditis elegans. We synthesized numerous structurally different FaRPs that were found in the C. elegans genome by bioinformatic analysis and used them to screen cells expressing the C26F1.6 receptor. Two peptides ending in M(orL)VRFamide elicited a calcium response in receptor-expressing mammalian Chinese hamster ovary cells. The response was dose-dependent and appeared to be very specific; that is, none of the other FaRPs were active, not even closely related peptides also ending in M(orL)VRFamide, which are encoded by the same peptide precursor. Pharmacological profiling with a truncated series of the most active peptide revealed that the full peptide sequence is necessary for receptor activation.
Annals of the New York Academy of Sciences 05/2005; 1040:410-2. DOI:10.1196/annals.1327.076 · 4.31 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: G-protein-coupled receptors (GPCRs) constitute one of the largest families of membrane-spanning proteins. Their importance in drug development has been proven over and over again. Therefore, they remain one of the most significant groups of molecules to be characterized. In the postgenomic era, the methods used for the characterization of GPCRs have dramatically changed: the predicted orphan receptors are now often used to ascertain the ligands (reverse pharmacology), whereas, in the past, the bioactive ligand was used to identify the receptor (classic approach). In this review, we will give an overview of the recent postgenomic functional assays that are frequently used to link the orphan GPCR of both vertebrate and invertebrate organisms with their ligands.
[Show abstract][Hide abstract] ABSTRACT: In this study, we describe the cloning and the characterization of the third FMRFamide-related peptide (FaRP) receptor in Caenorhabditis elegans, the VRFa receptor 1. Numerous structurally different FaRPs were synthesized and used to screen the orphan C26F1.6 receptor for activation. Two peptides ending in M(orL)VRFamide elicited a calcium response in receptor expressing mammalian cells. The response is dose-dependent and appeared to be very specific, since very closely related FaRPs were less active, even the other peptides ending in M(orL)VRFamide. Pharmacological profiling of the most active peptide suggests that SMVRFa is the most active binding core. N-terminal extension decreases peptide activity.
[Show abstract][Hide abstract] ABSTRACT: Differential display reverse transcriptase polymerase chain reaction (DDRT-PCR) in combination with semi-quantitative RT-PCR was used to compare differences in gene expression between the solitary and gregarious phase of Schistocerca gregaria. Twenty-six primer combinations were used, which produced 8 differential bands. Two out of the 8 differentials, one typical for the solitary and one for the gregarious phase, were further analyzed by semi-quantitative RT-PCR. The expression level of the solitary phase specific gene (SSG) was 2 times higher in solitary animals as compared to gregarious ones, while the gregarious specific gene (GSG) gave a 4-fold higher expression level in gregarious animals than in solitaries. Sequence analysis demonstrated that SSG does not belong to a known gene family, while the GSG belongs to the SPARC protein family.
Comparative Biochemistry and Physiology - Part A Molecular & Integrative Physiology 07/2003; 135(2):221-8. DOI:10.1016/S1095-6433(03)00050-3 · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Vitellogenic ovaries of the gray fleshfly Neobellieria bullata contain a variety of unidentified substances that interact, either as a substrate or as an inhibitor, with angiotensin converting enzyme (ACE). We here report the isolation and characterization of the first ACE interactive compound hereof. This 1312.7 Da peptide with the sequence NKLKPSQWISL, is substrate to both insect and human ACE. It is a novel peptide that shows high sequence similarity to a sequence at the N-terminal part of dipteran yolk polypeptides (YPs). We propose to call it N. bullata ovary-derived ACE interactive factor or Neb-ODAIF. Both insect and human ACE hydrolyze Neb-ODAIF by sequentially cleaving off two C-terminal dipeptides. K(m) values of Neb-ODAIF and Neb-ODAIF(1-9) (NKLKPSQWI) for human somatic ACE (sACE) are 17 and 81 microM, respectively. Additionally, Neb-ODAIF(1-7) (NKLKPSQ) also interacts with sACE (K(m/i)=90 microM). These affinity-constants are in range with those of the physiological ACE substrates and suggest the importance of Neb-ODAIF and its cleavage products in the elucidation of the physiological role of insect ACE. Alternatively, they can serve as lead compounds in the development of new drugs against ACE-related diseases in humans.
[Show abstract][Hide abstract] ABSTRACT: Angiotensin converting enzyme (ACE) was already discovered in insects in 1994, but its physiological role is still enigmatic. We have addressed this problem by purifying four new ACE substrates from the ovaries of the grey fleshfly, Neobellieria bullata. Their primary structures were identified as NKLKPSQWISLSD (Neb-ODAIF-1(1-13)), NKLKPSQWI (Neb-ODAIF-1(1-9)), SLKPSNWLTPSE (Neb-ODAIF-2) and LEQIYHL. Database analysis showed significant homology with amino acid sequence stretches as present in the N-terminal part of several fly yolk proteins. An antiserum raised against Neb-ODAIF-1(1-9) immunostained one out of three yolk protein bands of SDS/PAGE-separated fly haemolymph and egg homogenate, thus confirming that these peptides originate from a yolk protein gene product. Kinetic analysis of these peptides and of the peptides Neb-ODAIF and Neb-ODAIF-1(1-7) with insect ACE and human ACE show both similar and unique properties for insect ACE as compared with human C-domain ACE.
European Journal of Biochemistry 08/2002; 269(14):3522-30. DOI:10.1046/j.1432-1033.2002.03043.x · 3.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Angiotensin converting enzyme (ACE) activity, defined as a captopril-inhibitable dipeptidyl carboxypeptidase activity towards 3H-hippurylglycylglycine, was demonstrated in haemolymph, testes and ovaries of the grey fleshfly Neobellieria bullata, hereby suggesting a physiological role for ACE in these particular tissues. While the ACE activity in haemolymph and testes reached relatively high levels, only minute ACE activity could be detected in ovaries throughout the entire vitellogenic cycle. Ovarian extracts of Neobellieria bullata do contain, however, in addition to Neb-TMOF, the Neobellieria bullata trypsin modulating oostatic factor which is an in vitro and a putative in vivo substrate of ACE in circulation, several other heat-stable molecules which individually function either as an ACE substrate or ACE inhibitor. Presumably these ACE interactive factors mask ACE activity in the fly ovaries, as measured by a classic substrate-binding assay. Purification and characterisation of these ACE substrates/inhibitors is in progress and is likely to facilitate the elucidation of the enigmatic physiological relevance of ACE in insects.
Comparative Biochemistry and Physiology Part B Biochemistry and Molecular Biology 06/2002; 132(1):27-35. DOI:10.1016/S1096-4959(01)00529-2 · 1.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The degradation of the unblocked hexapeptide, trypsin modulating oostatic factor of the flesh fly Neobellieria (Sarcophaga) bullata (Neb-TMOF) was studied in vitro in the hemolymph of the lepidopteran Spodoptera frugiperda, the orthopteran Schistocerca gregaria and the dictyopteran Leucophaea maderae. The half-life in the different species varied from approximately 3min in L. maderae to approximately 25min in S. gregaria. Purification of the degradation products and ESI-Qq-oa-Tof mass spectrometry revealed the fragments Asn-Pro-Thr-Asn, Leu-His and Asn-Pro, which were the same in the hemolymph of all species. Except in Leucophaea, Neb-TMOF was cleaved in dipeptides starting from the C-terminus and the reaction could be, at least partially, inhibited by captopril. These observations suggest that a dipeptidase, which has very similar enzymatic properties as mammalian angiotensin converting enzyme (ACE) and which circulates in the hemolymph, apparently is involved in the breakdown of Neb-TMOF and might be a common but not a universal enzyme in insect hemolymph.The introduction of Neb-TMOF into the gut of S. gregaria with the help of a capillary tube (intubation) demonstrated that the intact peptide is able to cross the gut epithelium and to appear in the hemolymph compartment. Since [3H]-inulin, which is too large to cross cell membranes, was found to penetrate the gut walls at a measurable rate, the paracellular pathway might be also permeable to smaller peptides. There was indeed a clear correlation between the molecular weight of inulin, Neb-TMOF, and inositol and the rate of penetration of these compounds through the gut epithelium to the hemolymph. These are promising findings in view of a potential use of such peptides for insect control purposes.
[Show abstract][Hide abstract] ABSTRACT: A strong and constitutive angiotensin converting enzyme- or ACE-like activity was demonstrated in the hemolymph of the adult grey fleshfly Neobellieria bullata. In a competition assay, the N. bullata trypsin modulating oostatic factor (Neb-TMOF) was confirmed to be an in vitro substrate for this circulating Neb-ACE. Oral uptake of captopril, a selective and specific inhibitor of ACE, resulted in a complete phenotypic knockout of circulating ACE activity. When compared with control animals, captopril-fed female flies showed an increase in the liver meal-induced trypsin peak in the midgut and elevated levels of protein meal-induced yolk polypeptides in the hemolymph. The latter effect was not due to a slower vitellogenin uptake by the ovaries, because oocyte growth was not affected by the captopril treatment. The apparent synergism between the demonstrated ACE functionality and the previously reported effects of the oostatic peptide Neb-TMOF are discussed in the context of our recent finding that Neb-TMOF represents a prime candidate for being the first known in vivo substrate for circulating insect ACE. Arch.
Archives of Insect Biochemistry and Physiology 07/2001; 47(3):161-7. DOI:10.1002/arch.1047 · 1.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The unblocked hexapeptidic Trypsin Modulating Oostatic Factor of the fleshfly, an inhibitor of both trypsin and ecdysone biosynthesis, resists very well proteolytic breakdown by enzymes present in the lumen of the gut of previtellogenic fleshflies. However, when incubated in hemolymph of adult flies, females and males, its half-life time is a mere 0.5 min. In hemolymph of last instar larvae, this value increases to about 1.5 min. Whereas PMSF, a potent inhibitor of serine proteases has no effect, captopril and lisinopril, both known to be specific inhibitors of mammalian angiotensin I converting enzyme (ACE), effectively inhibit TMOF breakdown in fly hemolymph. Digestion of Neb-TMOF by recombinant Drosophila AnCE on itself results in identical degradation products as with total hemolymph. In both cases ESI-Qq-oa-Tof mass spectrometry demonstrated the appearance of peptide fragments with the sequences NPTN, LH and NP. These observations not only confirm the reported presence of circulating ACE-like activity in flies but also strongly suggest that in flies this hemolymph ACE-like activity might be involved in the regulation of the oostatic activity as exerted by Neb-TMOF.
[Show abstract][Hide abstract] ABSTRACT: The 24h molecular clock that ticks in organisms from bacteria to humans is useless without an output signal. The 18 amino acid neuropeptide, the pigment dispersing factor (PDF) encoded by the pdf gene, is the key outgoing signal in behavioral circadian rhythms in Drosophila melanogaster. PDF is likely to act on clock neurons in an autocrine or paracrine fashion. In this study, we identify the PDF receptor, which belongs to the G-protein coupled receptor family. We cloned the ORF of gene CG13758 and this resulted in a gene product of 669 amino acids, which did not correspond to the predicted protein length in the Drosophila database. Functional expression of this orphan receptor in HEK-293 cells and screening with a synthetic peptide library revealed that Drm-PDF specifically activates the receptor in a dose-dependent way. No other peptides were able to elicit a calcium response. These results indicate that we have cloned and identified the Drosophila PDF receptor.