Sequencing and characterization of trypsin modulating oostatic factor (TMOF) from the ovaries of the grey fleshfly, Neobellieria (Sarcophaga) bullata

Molecular sequencing and modeling of Neobellieria bullata trypsin. Evidence for translational control by Neobellieria trypsin-modulating oostatic factor

Trypsin mRNA from the grey fleshfly (Neobellieria bullata) was reversed transcribed and amplified by means of PCR. Two cDNA species of 600 bp and 800 bp were cloned and sequenced. The 3' end of the gene (300 bp) was amplified by means of the rapid-amplification-of-cDNA-ends method, cloned and sequenced. The deduced protein sequence of 254 amino acids exhibited 46% identity to Drosophila trypsin and 32% identity to Anophiline trypsin and Aedes trypsin. Three-dimensional models of Neobellieria trypsin and Drosophilia trypsin were built and compared. Both models contain two domains of beta-barrel sheets as was shown by means of X-ray crystallography of mammalian trypsin. The catalytic active site is composed of the canonical triad of His42, Asp87 and Ser182 whereas Asp176 sits as the bottom of the specificity pocket. Southern blot analysis suggested that Neobellieria trypsin is encoded by one gene. Northern blot analysis showed that an early trypsin transcript is found in the midgut of sugar-fed females. This message disappeared after a liver meal, and was replaced by a late transcript. Injection of trypsin-modulating oostatic factor (TMOF) at 10(-9) M prevented the disappearance and the translation of the early transcript. TMOF did not prevent the appearance of the late transcript. However, in the presence of the hormone the late transcript was not translated. Thus, TMOF is the biological signal that terminates the translation of trypsin mRNA in the fleshfly gut and probably in the mosquito gut.

Hormones and the cytoskeleton of animals and plants

It is often overlooked that a cell can exert its specific functions only after it has acquired a specific morphology: function follows form. The cytoskeleton plays an important role in establishing this form, and a variety of hormones can influence it. The cytoskeletal framework has also been shown to function in a variety of cellular processes, such as cell motility (important for behavior), migration (important for the interrelationship between the endocrine and immune systems, e.g., chemotaxis), intracellular transport of particles, mitosis and meiosis, maintenance of cellular morphology, spatial distribution of cell organelles (e.g., nucleus and Golgi system), cellular responses to membrane events (e.g., endocytosis and exocytosis), intracellular communication including conductance of electrical signals, localization of mRNA, protein synthesis, and--more specifically in plants--ordered cell wall deposition, cytoplasmic streaming, and spindle function followed by phragmoplast function. All classes of hormones seem to make use of the cytoskeleton, either during their synthesis, transport, secretion, degradation, or when influencing their target cells. In this review special attention is paid to cytoskeleton-mediated effects of selected hormones related to growth, transepithelial transport, steroidogenesis, thyroid and parathyroid functioning, motility, oocyte maturation, and cell elongation in plants.

An ecdysiostatin from flies

A bioassay for compounds with ecdysiostatic activity ('ecdysiostatins') was developed in order to prove the existence of an ecdysiostatin in blowfly larvae. The factor eluted by HPLC like Neb-TMOF (trypsin modulating oostatic factor), a hexapeptide that inhibits ecdysone biosynthesis. The ecdysiostatic activity of Neb-TMOF is specific, related peptides were less active or inactive. TMOF inhibits ecdysone biosynthesis rather than its secretion. It increases the cAMP level of ring glands. Effectors that elevate the intracellular cAMP can mimic the inhibitory effect of the ecdysiostatin. This suggests that cAMP may control steroidogenesis in fly larvae by shutting ecdysone biosynthesis. Thus, the hexapeptide acts as a prothoracicostatic hormone (PTSH) that controls ecdysone biosynthesis.

Feeding the mosquito Aedes aegypti with TMOF and its analogs; effect on trypsin biosynthesis and egg development

Female Aedes aegypti that were given a blood meal by enema deposited yolk in their oocytes and synthesized trypsinlike enzymes in their midgut. When females were given an enema of Aea-TMOF (Trypsin Modulating Oostatic Factor) (NH2-YDPAPPPPPP-COOH) and blood both egg development and trypsin biosynthesis were inhibited. Similar results were observed if TMOF was mixed with the blood meal and fed to female mosquitoes through a membrane. Renin inhibitor (NH2-PHPFHFFVYK-COOH) or poly proline given by enema with the blood meal did not affect egg development or trypsin biosynthesis. Feeding of TMOF analogs P1 (NH2-YDPAP-COOH) or P4 (NH2-YDPAPPPP-COOH) inhibited trypsin biosynthesis in the midgut. Injecting or giving an enema of an amidated peptide (NH2-WRPGPPPPPP-CONH2) of HIV-2 X-ORF protein also inhibited egg development and trypsin biosynthesis in the mosquito gut. When [3H]TMOF was purified by high performance liquid chromatography (HPLC) and fed with the blood meal through a membrane to female mosquitoes, [3H]TMOF outside the gut increased linearly for the first 24 h and 28% of the hormone was found outside the gut at 72 h. These results suggest that TMOF and its active analogs traverse the gut epithelial cells into the hemolymph, bind TMOF gut receptor(s) and modulate trypsin biosynthesis.

Folliculostatins, gonadotropins and a model for control of growth in the grey fleshfly, Neobellieria (sarcophaga) bullata

The sequences of two folliculostatic peptides of the fleshfly Neobellieria bullata have been determined recently. The first peptide (Neb-TMOF: H-NPTNLH-OH), originates from a 75 kDa precursor protein found in vitellogenic oocytes. The hexapeptide directly inhibits the synthesis of trypsin-like enzymes in the gut, and thus lowers the concentration of yolk polypeptides in the hemolymph. It also inhibits the biosynthesis of ecdysone in the larval ring gland. Therefore, it could also be named prothoracicostatic hormone (Neb-PTSH). The second peptide (Neb-colloostatin: H-SIV-PLGLPVPIGPIVVGPR-OH) acts on previtellogenic follicles and is a cleaved product of a collagen-like precursor molecule. Our results indicate that peptides that are cleaved from matrix proteins could act as growth-inhibiting factors. Gonadotropin releasing hormone (GnRH)-immunolike peptides were not identified, but progress is being made in the isolation and characterization of factors which stimulate cAMP production by the ovary. Using these results, a novel model of growth control in which matrix proteins play an important role as a potential source of growth regulators has been developed.

Neb-colloostatin, a second folliculostatin of the grey fleshfly, Neobellieria bullata

During the purification of trypsin-modulating oostatic factor (TMOF) of the grey fleshfly Neobellieria bullata, a new factor with oostatic activity was discovered. We report herein its purification, primary structure and effects on oocyte development. Its amino acid sequence was determined as H-SIVPLGLPVPIGPIVVGPR-OH. Due to structural sequence similarities with parts of several known collagens and its oostatic activity, we named it Neb-colloostatin. The synthetic peptide inhibits yolk uptake by previtellogenic oocytes and might have a role in the absence of yolk deposition in penultimate oocytes. Neb-colloostatin does not inhibit trypsin biosynthesis in the gut or ecdysone biosynthesis by larval ring glands. It decreases vitellogenin concentrations in the hemolymph by an unknown mode of action. The role of extracellular matrix proteins in the feedback control of growth is discussed.

Inhibition of ecdysone biosynthesis in flies by a hexapeptide isolated from vitellogenic ovaries

The only identified insect peptides known to be involved in controlling the biosynthesis of ecdysone, the steroid moulting hormone of arthropods, are the prothoracicotropic hormones (PTTH). These neuropeptides stimulate ecdysone biosynthesis. Recently, a hexapeptide (NPTNLH) with folliculostatic and trypsin modulating activity was isolated from vitellogenic ovaries of the fleshfly Neobellieria bullata. Here we report that the hexapeptide, when tested in vitro on the isolated ring gland of flies, inhibited ecdysone biosynthesis immediately and completely (EC50 = 5 nM). The hexapeptide is the first known factor with 'prothoracicostatic activity' and may form part of the endocrine system that controls ecdysone biosynthesis in vivo.