Biological activity of structural analogs and effect of oil as a carrier of trypsin modulating oostatic factor of the gray fleshfly Neobellieria bullata

Oostatic peptides

Oostatic peptides are organic molecules, which influence an insect reproduction due to a regulation of the eggs development. It was proved that decapeptide-H-Tyr-Asp-Pro-Ala-Pro-Pro-Pro-Pro-Pro-Pro-OH (YDPAPPPPPP)-isolated from mosquito Aedes aegypti, inhibits trypsin activity in the midgut of the mosquito. Therefore, it was named trypsin-modulating oostatic factor (Aea-TMOF). Feeding the recombinant cells with cloned and expressed TMOF on the coat protein of tobacco mosaic virus (TMV) to mosquito larvae, caused larval mortality. The TMOF was therefore designed for usage as a new biorational insecticide against mosquito. Similarly, a hexapeptide-H-Asn-Pro-Thr-Asn-Leu-His-OH (NPTNLH)-was isolated from the grey flesh fly Neobellieria bullata. This peptide and some of its analogs inhibited trypsin-like synthesis by the midgut in female flies and was therefore entitled Neb-TMOF. Interestingly, the synthetic Aea-TMOF and mainly its C-terminus shorten analogs, including those containing D-amino acids or methylene-oxy isosteric bond, quickly and strongly inhibited the hatchability and egg development in the flesh fly N. bullata.

Dispersion of peptides in vegetable oil as a simple slow release formula for both injection and oral uptake in insects: a case study with [His7]-corazonin in an albino Locusta migratoria deficient in corazonin

Upon realizing that for drug delivery in the body, lipidization is a technique used in the pharmaceutical industry, we took in consideration that corazonin melanizes the cuticle of albino Locusta migratoria only when injected in an emulsion in oil, not when applied in a watery solution. In this study, we investigate the possibility for oral uptake of corazonin dispersed in oil, and validated the activity by a melanization assay. Not only was it active, it also induced red cuticular coloration in some animals, and it was also unexpectedly lethal for nymphs, but not for adults. These results necessitate the revision of the potential of (some) peptides for insect control. Also, they suggest practical recommendations for the application of other peptides in physiological assays where oil could be used as a simple slow release formula.

Insect gonadotropic peptide hormones: some recent developments

Gonadotropic peptides are a new generation of peptide hormone regulators of insect reproduction. They have been isolated from ovaries, oviducts, or brains of insects. The subject of this paper is insect peptides that exert stimulatory or inhibitory effects on ovarian development and oocyte maturation. On the basis of the literature data and the results of our investigations, the structure and biological properties of different groups of peptides are presented.

Activity and mechanism of action of insect oostatic peptides in flesh fly

The relationship between structure and activity of insect oostatic decapeptide (Aed-TMOF) analogues in flesh fly was analyzed. The highest oostatic activity was exhibited by the pentapetide and tetrapeptide analogues, H-Tyr-Asp-Pro-Ala-Pro-OH and H-Tyr-Asp-Pro-Ala-OH, respectively. The tetrapeptide, either native or tritiated, was used to study its metabolism in the ovaries and hemolymph and to detect putative binding sites in the flesh fly ovaries and head. A high metabolism of the tetrapeptide with a half-life in the hemolymph and ovaries less than 1h was determined. The initial limiting step in the degradation is tyrosine(1) cleavage. Other degradation products were detected only transiently in low quantities. Using tritiated tetrapeptide, we found that only very low specific binding was detected in the homogenates of ovaries and in the rough membrane preparation in the presence and absence of protease inhibitors.

Nuclear magnetic resonance (NMR) studies of the dark-color-inducing neurohormone of locusts and corazonin

The dark-color-inducing neurohormone (DCIN) of locusts and corazonin of a cockroach, both 11 residue-long peptides, induce dark coloration in albino nymphs of Locusta migratoria when injected after a nymphal molt. These peptides differ at position 7 (His in DCIN and Arg in corazonin) and elicit an almost identical darkening response. The three-dimensional structures of these peptides, dissolved in dimethylsulfoxide (DMSO), were determined by NMR. Structural elements determined at atomic resolution may provide insight into the biological activity of these two neurohormones. The calculated structures of DCIN and corazonin indicate clear, prevalent conformations with similar secondary features. The generated low-energy solution structures of each show structural elements within residues Phe3 to Trp9 with a turn situated at the core of the peptide from which the sidechains of residue 7 of each peptide protrude. A calculated negative electrostatic potential surface almost completely covers both neurohormones and only the 7th residue sidechains of each peptide emerge in their entirety. Within these residues there is a partial sequence seen in several neurohormones that control various physiological functions in Arthropods: -Ser-X-Gly-Trp- (X=His in DCIN and Arg in corazonin). This partial sequence may play a role in the physiological activity of some Arthropod neurohormones.

Insect oostatic peptide: absence of effect on mice ovaries

An analogue of insect oostatic peptide, the pentapeptide H-Tyr-Asp-Pro-Ala-Pro-OH (H-YDPAP-OH), was administered to female mice and its effects on reproduction and development of the ovaries were studied. Up to 0.5 mg of the peptide per mice (25 g b.w.) injected intraperitoneally did not change the rate of pregnancy, number of offsprings and histological findings in ovaries and uterus in comparison to saline treated controls.

In vitro degradation of the Neb-Trypsin modulating oostatic factor (Neb-TMOF) in gut luminal content and hemolymph of the grey fleshfly, Neobellieria bullata

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.

Hormonal control of body-color polymorphism in Locusta migratoria: interaction between

The effects of injection of [His(7)]-corazonin and juvenile hormone (JH) III on the body color in L. migratoria were investigated using albino and normal (pigmented) nymphs. Most albino nymphs turned green in the fourth instar if injected with JH III during the last 2 days of the previous instar. When albino third instar nymphs injected with 10 pmol of [His(7)]-corazonin on different days were treated with 100 µg of JH III on day 3.5, they developed various body colors in the following nymphal instar: those injected with [His(7)]-corazonin during the first 2 days developed very dark green or black color, whereas some of those injected after this period turned green and their legs and ventral side of the body were variously pigmented, the coloration being similar to green solitary individuals often found in the field. Field-collected brown solitary nymphs injected with 1 nmol of [His(7)]-corazonin and kept individually, turned reddish without any black spots in the following nymphal instar when the ecdysis occurred within 1 day after injection. Injection of [His(7)]-corazonin 2 days before the following ecdysis induced black patterns on an orange background color, the coloration characteristic of gregarious forms. Similar injections into field-collected green solitary nymphs also induced black patterns but the rest of their body remained green. These results may indicate that the temporal changes in the hemolymph titers of [His(7)]-corazonin and JH play an important role in the control of body-color polymorphism in this locust.