A cardioactive peptide from the southern armyworm, Spodoptera eridania

Developmental regulation and antifungal activity of a growth-blocking peptide from the beet armyworm Spodoptera exigua

Insect cytokine growth-blocking peptides (GBPs) are involved in growth regulation and the innate immune response. However, the microbial binding and antimicrobial activities of GBPs remain unclear. Here, we investigate the developmental role and antifungal activity of a GBP from the beet armyworm Spodoptera exigua (SeGBP). Sequence analysis predicted that mature SeGBP consists of 24 amino acid residues, including 2 cysteine residues. During S. exigua development, SeGBP is constitutively expressed in the fat body during the larval and adult stages but not in pupae. SeGBP expression is up-regulated by 20-hydroxyecdysone and down-regulated by juvenile hormone analog. Recombinant SeGBP purified from baculovirus-infected insect cells retards the growth of S. exigua larvae. Additionally, SeGBP expression is acutely induced in the fat body after injection with Escherichia coli, Bacillus thuringiensis, or Beauveria bassiana. Recombinant SeGBP can bind to B. bassiana but not to E. coli or B. thuringiensis. Consistent with these findings, SeGBP shows antifungal activity against B. bassiana. Therefore, these results provide insight into the role of SeGBP during the innate immune response following microbial infection, and furthermore, they suggest a novel function for SeGBP as a direct antifungal agent against entomopathogenic fungi, such as B. bassiana.

Characteristics common to a cytokine family spanning five orders of insects

Growth-blocking peptide (GBP) is a member of an insect cytokine family with diverse functions including growth and immunity controls. Members of this cytokine family have been reported in 15 species of Lepidoptera, and we have recently identified GBP-like peptides in Diptera such as Lucilia cuprina and Drosophila melanogaster, indicating that this peptide family is not specific to Lepidoptera. In order to extend our knowledge of this peptide family, we purified the same family peptide from one of the tenebrionids, Zophobas atratus,(1) isolated its cDNA, and sequenced it. The Z. atratus GBP sequence together with reported sequence data of peptides from the same family enabled us to perform BLAST searches against EST and genome databases of several insect species including Coleoptera, Diptera, Hymenoptera, and Hemiptera and identify homologous peptide genes. Here we report conserved structural features in these sequence data. They consist of 19-30 amino acid residues encoded at the C terminus of a 73-152 amino acid precursor and contain the motif C-x(2)-G-x(4,6)-G-x(1,2)-C-[KR], which shares a certain similarity with the motif in the mammalian EGF peptide family. These data indicate that these small cytokines belonging to one family are present in at least five insect orders.

Drosophila growth-blocking peptide-like factor mediates acute immune reactions during infectious and non-infectious stress

Antimicrobial peptides (AMPs), major innate immune effectors, are induced to protect hosts against invading microorganisms. AMPs are also induced under non-infectious stress; however, the signaling pathways of non-infectious stress-induced AMP expression are yet unclear. We demonstrated that growth-blocking peptide (GBP) is a potent cytokine that regulates stressor-induced AMP expression in insects. GBP overexpression in Drosophila elevated expression of AMPs. GBP-induced AMP expression did not require Toll and immune deficiency (Imd) pathway-related genes, but imd and basket were essential, indicating that GBP signaling in Drosophila did not use the orthodox Toll or Imd pathway but used the JNK pathway after association with the adaptor protein Imd. The enhancement of AMP expression by non-infectious physical or environmental stressors was apparent in controls but not in GBP-knockdown larvae. These results indicate that the Drosophila GBP signaling pathway mediates acute innate immune reactions under various stresses, regardless of whether they are infectious or non-infectious.

Antagonistic effect of juvenile hormone on hemocyte-spreading behavior of Spodoptera exigua in response to an insect cytokine and its putative membrane action

Juvenile hormone (JH) acts on membrane of follicle cells to induce ovarian patency for vitellogenesis, though it regulates various other physiological processes via putative intracellular receptors. This study suggests another JH membrane action by analyzing in vitro hemocyte behavior. In response to nonself, both granular cells and plasmatocytes of Spodoptera exigua can exhibit cell shape changes through spreading behaviors. Plasmatocytes were separated from total S. exigua hemocytes by Percoll gradient and exposed in vitro to an insect cytokine, plasmatocyte-spreading peptide (PSP), identified from Pseudoplusia includens. In response, the purified plasmatocytes spread in a dose-dependent manner from picomolar to micromolar concentrations. Interestingly, the PSP responses of plasmatocytes in S. exigua varied among different larval ages during fifth instar ( approximately 5 days at 25 degrees C) in a sensitivity order of late (5 days old)<early (1 day old)<mid (3 days old). Considering the overall endocrine changes that occur during the final instar of holometabolous insects, we suspected that JH and ecdysteroid hormones were responsive for this developmental modulation of plasmatocyte sensitivity to PSP. We tested this hypothesis by exposing plasmatocytes to hormone agonists in vitro. Pyriproxyfen, a JH agonist, significantly inhibited plasmatocyte sensitivity to PSP. JH I and II had significant effects on antagonizing plasmatocyte sensitivity to PSP, but either JH III or farnesoic acid did not. In contrast, 20-hydroxyecdysone (20E) enhanced the plasmatocyte sensitivity to PSP. Ethoxyzolamide, a putative JH competitor to membrane receptor, inhibited JH action on the plasmatocyte sensitivity to PSP. Though staurosporine (a protein kinase inhibitor) alone did not influence plasmatocyte sensitivity to PSP, it antagonized the JH inhibitory effect on the plasmatocytes. Ouabain, a specific Na+ -K+ ATPase inhibitor, also masked the JH action on the plasmatocytes. These results suggest that the JH acts on the membrane of the plasmatocytes and prevents plasmatocyte spreading by reducing cell volume through activating Na+ -K+ pump via protein kinase C signal pathway.

Discovering new invertebrate neuropeptides using mass spectrometry

Neuropeptides are a complex set of messenger molecules controlling a wide array of regulatory functions and behaviors within an organism. These neuromodulators are cleaved from longer protein molecules and often experience numerous post-translational modifications to achieve their bioactive form. As a result of this complexity, sensitive and versatile analysis schemes are needed to characterize neuropeptides. Mass spectrometry (MS) through a variety of approaches has fueled the discovery of hundreds of neuropeptides in invertebrate species in the last decade. Particularly successful are direct tissue and single neuron analyses by matrix-assisted laser desorption/ionization (MALDI) MS, which has been used to elucidate approximately 440 neuropeptides, and examination of neuronal homogenates by electrospray ionization techniques (ESI), also leading to the characterization of over 450 peptides. Additional MS methods with great promise for the discovery of neuropeptides are MS imaging and large-scale peptidomics studies in combination with a sequenced genome.

A cytokine secreted from the suboesophageal body is essential for morphogenesis of the insect head

The suboesophageal body of insects was identified over a century ago in the silkworm embryo, but its biological function is still unknown. We discovered that this tissue is differentiated in the earliest embryonic stages of the cabbage armyworm and secretes the insect cytokine, growth-blocking peptide (GBP), transiently from 24 to 60 h after oviposition when gastrulation is in progress. Over-expression of GBP, achieved by microinjection of the GBP gene driven by a cytomegalovirus (CMV) constitutive promoter, resulted in complex deformities of the procephalon (embryonic head). Severe abnormal phenotypes of the head structure were produced by silencing the GBP expression in the embryo by treating with GBP double-stranded RNA: the procephalon-containing optic lobes diminished and completely separated into bilateral halves. This indicates that GBP secreted from the suboesophageal body plays an essential role in the formation of the procephalic domain during early embryogenesis. The cytokine-induced fusion of bilateral procephalic lobes is thought to be evolutionarily conserved at least in insects, because of the widespread occurrence of the suboesophageal body in insect embryos.

Effects of peptides, with emphasis on feeding, pain, and behavior A 5-year (1999-2003) review of publications in Peptides

Novel effects of naturally occurring peptides are continuing to be discovered, and their mechanisms of actions as well as interactions with other substances, organs, and systems have been elucidated. Synthetic analogs may have actions similar or antagonistic to the endogenous peptides, and both the native peptides and analogs have potential as drugs or drug targets. The journal Peptides publishes many leading articles on the structure-activity relationship of peptides as well as outstanding reviews on some families of peptides. Complementary to the reviews, here we extract information from the original papers published during the past five years in Peptides (1999-2003) to summarize the effects of different classes of peptides, their modulation by other chemicals and various pathophysiological states, and the mechanisms by which the effects are exerted. Special attention is given to peptides related to feeding, pain, and other behaviors. By presenting in condensed form the effects of peptides which are essential for systems biology, we hope that this summary of existing knowledge will encourage additional novel research to be presented in Peptides.

The Gly-Gly Linker Region of the Insect Cytokine Growth-blocking Peptide Is Essential for Activity

Growth-blocking peptide (GBP) is a 25-amino acid cytokine isolated from the lepidopteran insect Pseudaletia separata. GBP exhibits various biological activities such as regulation of larval growth of insects, proliferation of a few kinds of cultured cells, and stimulation of a class of insect immune cells called plasmatocytes. The tertiary structure of GBP consists of a well structured core domain and disordered N and C termini. Our previous studies revealed that, in addition to the structured core, specific residues in the unstructured N-terminal region (Glu1 and Phe3) are also essential for the plasmatocyte-stimulating activity. In this study, a number of deletion, insertion, and site-directed mutants targeting the unstructured N-terminal residues of GBP were constructed to gain more detailed insight into the mode of interaction between the N-terminal region and GBP receptor. Alteration of the backbone length of the linker region between the core structure and N-terminal domain reduced plasmatocyte-stimulating activity. The substitutions of Gly5 or Gly6 in this linker region with more bulky residues, such as Phe and Pro, also remarkably reduced this activity. We conclude that the interaction of GBP with its receptor depends on the relative position of the N-terminal domain to the core structure, and therefore the backbone flexibility of Gly residues in the linker region is necessary for adoption of a proper conformation suited to receptor binding. Additionally, antagonistic experiments using deletion mutants confirmed that not only the core domain but also the N-terminal region of GBP are required for "receptor-binding," and furthermore Phe3 is a binding determinant of the N-terminal domain.

Effects of silkworm paralytic peptide on in vitro hematopoiesis and plasmatocyte spreading

Bombyx mori paralytic peptide (BmPP), a multifunctional cytokine-like molecule, is expressed in the hematopoietic organ-wing imaginal disc complex, suggesting that BmPP is involved in both immune response and the hematopoietic process. We studied the effects of BmPP on plasmatocytes and hematopoietic organs of the silkworm. BmPP (1 microM) stimulated spreading of circulating plasmatocytes, but the percentage of spread plasmatocytes was only 20%. Over 10 nM of BmPP, however, elicited prominent spreading in 70% of young plasmatocytes discharged from cultured hematopoietic organs. Cells in hematopoietic organs that were enzymatically dispersed did not spread even after adding 100 nM of BmPP, indicating that plasmatocytes acquired BmPP-sensitivity immediately after discharge. When cultured in a medium containing larval plasma, hematopoietic organs grew markedly and discharged a large number of hemocytes, over 95% of which were morphologically plasmatocytes. The hemocyte discharge was blocked in the medium containing BmPP dose-dependently, although hematopoietic organ growth was not suppressed. These results suggest that BmPP plays important roles both in hematopoietic regulation and in the hemocyte immune reaction of the silkworm.

Roles of aromatic residues in the structure and biological activity of the small cytokine, growth-blocking peptide (GBP)

Growth-blocking peptide (GBP) is a small (25 amino acids) insect cytokine with a variety of functions: controlling the larval development of lepidopteran insects, acting as a mitogen for various types of cultured cells, and stimulating insect blood cells. The aromatic residues of GBP (Phe-3, Tyr-11, and Phe-23) are highly conserved in the ENF peptide family found in lepidopteran insects. We investigated the relationship between the biological activities and structural properties of a series of GBP mutants, in which each of the three aromatic residues is replaced by a different residue. The results of the hemocytes-stimulating assays of GBP mutants indicated that Phe-3 is the key residue in this activity: Ala or Tyr replacement resulted in significant loss of the activity, but Leu replacement did not. The replacements of other aromatic residues hardly affected the activity. On the other hand, NMR analysis of the mutants suggested that Tyr-11 is a key residue for maintaining the core structure of GBP. Surprisingly, the Y11A mutant maintained its biological activity, although its native-like secondary structure was disordered. Detailed analyses of the (15)N-labeled Y11A mutant by heteronuclear NMR spectroscopy showed that the native-like beta-sheet structure of Y11A was induced by the addition of 2,2,2-trifluoroethanol. The results suggest that Y11A has a tendency to form a native-like structure, and this property may give the Y11A mutant native-like activity.

Expression and purification of a small cytokine growth-blocking peptide from armyworm Pseudaletia separata by an optimized fermentation method using the methylotrophic yeast Pichia pastoris

A small multifunctional cytokine, growth-blocking peptide (GBP), from the armyworm Pseudaletia separata larvae was expressed as a soluble and active recombinant peptide in the methylotrophic yeast Pichia pastoris. An expression vector for GBP secretion was constructed using vector pPIC9, and GBP was expressed under the control of the alcohol oxidase (AOX1) promoter. Although we first tried to cultivate GBP in shake flask cultures, the yield was low, probably due to proteolysis of the recombinant protein. To overcome this problem, we utilized a high-density fermentation method. The pH of the medium in the fermenter was kept at 3.0, and the medium was collected within 48h post methanol shift to minimize exposure of the target peptide to proteases. Recombinant GBP was purified through three reverse-phase HPLC columns. We characterized the 25 amino acid GBP by molecular mass spectrometry and amino acid sequencing. Plasmatocyte spreading, one of the activities of GBP, was similar between chemically synthesized GBP and purified recombinant GBP. Up to 50mg GBP was recovered per 1L of yeast culture supernatant.

Primary structures of four trypsin inhibitor E homologs from venom of Dendroaspis angusticeps: structure-function comparisons with other dendrotoxin homologs

Four trypsin inhibitor homologs, the first known from Dendroaspis angusticeps venom, were characterized using a combination of gel filtration, cation exchange, reverse-phase liquid chromatography, Edman degradation and mass spectrometry. The four toxins comprise two 57 residue and two 59 residue isoforms. The long toxins possess a Lys-Gln N-terminal extension lacked by the short toxins. The only other structural difference is an Arg/His replacement at position 55. The long Arg55 variant is identical to trypsin inhibitor E from the venom of Dendroaspis polylepis. The name epsilon-dendrotoxin is suggested so as to follow the nomenclature of Benishin, C.G., Sorensen, R.G., Brown, W.E., Krueger, B.K., Blaustein, M.P., 1988. Four polypeptide components of green mamba venom selectively block certain potassium channels in rat brain synaptosomes. Mol. Pharmacol. 34, 152-159. Among snake venom protease inhibitors, the epsilon-dendrotoxins are structurally most like the delta-dendrotoxins, with which they share only 64% of their residues. In addition, the epsilon-dendrotoxins display hydropathy profiles more like those of the alpha- and delta-dendrotoxins, than those of the trypsin inhibitors from snake venoms. Given the strong protease inhibitory activity of trypsin inhibitor E and the recently demonstrated weak K(+) channel inhibitory activity of two of these variants (Tytgat, J., Vandenberghe, I., Ulens, C., Van Beeumen, J., 2001. New polypeptide components purified from mamba venom. FEBS Lett. 491, 217-221), the epsilon-dendrotoxins represent structural and functional intermediates between the facilitatory toxins and the protease inhibitors.

Characterization of receptors of insect cytokine, growth-blocking peptide, in human keratinocyte and insect Sf9 cells

Insect cytokine, growth-blocking peptide (GBP), enhances cell proliferation of human keratinocyte cells with a potency almost equivalent to that of human epidermal growth factor (EGF). GBP consists of 25 amino acid residues containing a core region that shows a striking similarity to the C-terminal beta-loop domain of EGF and disordered N and C termini. The present study demonstrates that, although GBP lacks the N-terminal half-portion of EGF molecule, at least five amino acids of the disordered N-terminal six-amino acid region are indispensable for affecting the cell growth activity of GBP. Upon stimulating mitogenesis in keratinocyte cells, GBP directly binds and activates their EGF receptors. GBP also effects proliferative activity on insect Sf9 cells through the binding and activation of the specific receptor, which consists of a heterodimeric complex: a binding subunit (60 kDa) and a tyrosine phosphorylation subunit (58 kDa). These results indicate that GBP enhances cell proliferation of human keratinocyte and insect Sf9 cells through the activation of EGF and GBP receptors, respectively.

Structure and activity of the insect cytokine growth-blocking peptide. Essential regions for mitogenic and hemocyte-stimulating activities are separate

Growth-blocking peptide (GBP) is a 25-amino acid insect cytokine found in Lepidopteran insects that possesses diverse biological activities such as larval growth regulation, cell proliferation, and stimulation of immune cells (plasmatocytes). The tertiary structure of GBP consists of a structured core that contains a disulfide bridge and a short antiparallel beta-sheet (Tyr(11)-Arg(13) and Cys(19)-Pro(21)) and flexible N and C termini (Glu(1)-Gly(6) and Phe(23)-Gln(25)). In this study, deletion and point mutation analogs of GBP were synthesized to investigate the relationship between the structure of GBP and its mitogenic and plasmatocyte spreading activity. The results indicated that deletion of the N-terminal residue, Glu(1), eliminated all plasmatocyte spreading activity but did not reduce mitogenic activity. In contrast, deletion of Phe(23) along with the remainder of the C terminus destroyed all mitogenic activity but only slightly reduced plasmatocyte spreading activity. Therefore, the minimal structure of GBP containing mitogenic activity is 2-23 GBP, whereas that with plasmatocyte spreading activity is 1-22 GBP. NMR analysis indicated that these N- and C-terminal deletion mutants retained a similar core structure to wild-type GBP. Replacement of Asp(16) with either a Glu, Leu, or Asn residue similarly did not alter the core structure of GBP. However, these mutants had no mitogenic activity, although they retained about 50% of their plasmatocyte spreading activity. We conclude that specific residues in the unstructured and structured domains of GBP differentially affect the biological activities of GBP, which suggests the possibility that multifunctional properties of this peptide may be mediated by different forms of a GBP receptor.

Molecular cloning of silkworm paralytic peptide and its developmental regulation

The silkworm paralytic peptide (PP) is a member of the ENF peptide family that exerts multiple biological activities involved in defense reaction and growth regulation. We isolated its cDNA and examined mRNA expression profiles. cDNA encoded 131 amino acids from which the 23-residue PP sequence was found at the C-terminal portion. Immunoblot analysis and paralytic activity assay indicated that inactive pro-protein in larval hemolymph was processed into active peptide immediately after bleeding. In the last larval instar, 0.6-kb PP mRNA was expressed in various tissues, of which the fat body was predominant. Its expression in the fat body decreased during the feeding period and then increased during metamorphic process. Juvenile hormone and 20-hydroxyecdysone upregulated its expression. At the embryonic stage, 1.5-kb mRNA, in addition to 0.6-kb mRNA, was expressed from 1 day after oviposition to hatching. PP was thus expressed stage-specifically under hormonal control.

Regeneration of cultured midgut cells after exposure to sublethal doses of toxin from two strains of Bacillus thuringiensis

Toxin from two strains of Bacillus thuringiensis (Bt), AA 1-9 and HD-73, caused dose-dependent destruction of cultured midgut cells from Heliothis virescens larvae. HD-73 toxin was more effective although, at the doses used, not all cells were killed. After 2 days of exposure to 0.8 pg/µl AA 1-9 or 0.06 pg/µl HD-73, columnar and goblet cell numbers declined to ca 20% of controls. In contrast, stem and differentiating cells increased to 140-200% of controls. The dynamic of depletion and replacement depended on toxin type and concentration. Two days after toxin was washed out, ratios of cell types returned to approximate control levels, suggesting rapid population corrections in vitro. Regulation of the ratio of cell types in each population, and the rate of proliferation and differentiation of stem cells was induced by the cultured midgut cells themselves. Controls and cells treated with toxin from Bt strain AA 1-9 were stained using a polyclonal antibody to Lepidopteran midgut differentiation factor 1 (MDF1). With Bt toxin, 1.5 times more cells stained for MDF1, suggesting increased synthesis of this differentiation factor during increased stem cell differentiation. The response of cultured midgut cells to Bt toxin injury is similar to injured vertebrate tissues dependent on stem cells for replacement and healing.

Alanine-scanning mutagenesis of plasmatocyte spreading peptide identifies critical residues for biological activity

Plasmatocyte spreading peptide (PSP) is a 23-amino acid cytokine that induces a class of insect immune cells called plasmatocytes to spread on foreign surfaces. The structure of PSP consists of a disordered N terminus (residues 1-6) and a well-defined core (residues 7-23) stabilized by a disulfide bridge between Cys(7) and Cys(19), hydrophobic interactions, and a short beta-hairpin. Structural comparisons also indicate that the core region of PSP adopts an epidermal growth factor (EGF)-like fold very similar to the C-terminal subdomain of EGF-like module 5 of thrombomodulin. To identify residues important for plasmatocyte spreading activity, we bioassayed PSP mutants in which amino acids were either replaced with alanine or deleted. Within the well-defined core of PSP, alanine replacement of Cys(7) and Cys(19) (C7.19A) eliminated all activity. Alanine replacement of Arg(13) reduced activity approximately 1000-fold in comparison to wild-type PSP, whereas replacement of the other charged residues (Asp(16), Arg(18), Lys(20)) surrounding Cys(19) diminished activity to a lesser degree. The point mutants Y11A, T14A, T22A, and F23A had activity identical or only slightly reduced to that of wild-type PSP. The mutant PSP-(7-23) lacked the entire unstructured domain of PSP and was found to have no plasmatocyte spreading activity. Surprisingly, E1A and N2A had higher activity than wild-type PSP, but F3A had almost no activity. We thus concluded that the lack of activity for PSP-(7-23) was largely due to the critical importance of Phe(3). To determine whether reductions in activity correlated with alterations in tertiary structure, we compared the C7.19A, R13A, R18A, and F3A mutants to wild-type PSP by NMR spectroscopy. As expected, the simultaneous replacement of Cys(7) and Cys(19) profoundly affected tertiary structure, but the R13A, R18A, and F3A mutants did not differ from wild-type PSP. Collectively, these results indicate that residues in both the unstructured and structured domains of PSP are required for plasmatocyte-spreading activity.

Cardioacceleratory action of tachykinin-related neuropeptides and proctolin in two coleopteran insect species

Several cardioactive peptides have been identified in insects and most of them are likely to act on the heart as neurohormones. Here we have investigated the cardioactive properties of members of a family of insect tachykinin-related peptides (TRPs) in heterologous bioassays with two coleopteran insects, Tenebrio molitor and Zophobas atratus. Their effects were compared with the action of the pentapeptide proctolin. We tested the cardiotropic activity of LemTRP-4 isolated from the midgut of the cockroach Leucophaea maderae, CavTK-I and CavTK-II isolated from the blowfly Calliphora vomitoria. The semi-isolated hearts of the two coleopteran species were strongly stimulated by proctolin. We observed a dose dependent increase in heartbeat frequency (a positive chronotropic effect) and a decrease in amplitude of contractions (a negative inotropic effect). In both beetles the TRPs are less potent cardiostimulators and exert lower maximal frequency responses than proctolin. LemTRP-4 applied at 10(-9)-10(-6) M was cardiostimulatory in both species inducing an increase of heart beat frequency. The amplitude of contractions was stimulated only in Z. atratus. CavTK-I and CavTK-II also exerted cardiostimulatory effects in Z. atratus at 10(-9)-10(-6) M. Both peptides stimulated the frequency, but only CavTK-II increased the amplitude of the heart beat. In T. molitor, however, the CavTKs induced no significant effect on the heart. Immunocytochemistry with antisera to the locust TRPs LomTK-I and LomTK-II was employed to identify the source of TRPs acting on the heart. No innervation of the heart by TRP immunoreactive axons could detected, instead it is possible that TRPs reach the heart by route of the circulation. The likely sources of circulating TRPs in these insects are TRP-immunoreactive neurosecretory cells of the median neurosecretory cell group in the brain with terminations in the corpora cardiaca and endocrine cells in the midgut. In conclusion, LemTRP-4, CavTK-I and CavTK-II are less potent cardiostimulators than proctolin and also exert stimulatory rather than inhibitory action on amplitude of contractions. The differences in the responses to proctolin and TRPs suggest that the peptides regulate heart activity by different mechanisms.

Plasmatocyte spreading peptide (PSP1) and growth blocking peptide (GBP) are multifunctional homologs

Recently, we identified Plasmatocyte spreading peptide (PSP1) from the moth Pseudoplusia includens and reported that it mediates adhesion of hemocytes to foreign surfaces. PSP1 is structurally very similar to three classes of peptides identified earlier from other species of Lepidoptera: growth blocking peptide (GBP) originally identified in Pseudaletia separata, and a series of related peptides from other species designated as paralytic (PP) or cardioactive (CAP) peptides. In this study, we conducted parallel experiments in P. includens and P. separata to determine whether PSP1 and GBP have distinct or multiple biological activities. Both peptides affected the adhesive state of hemocytes from each moth very similarly. PSP1 and GBP exhibited significant growth blocking and paralytic activity in P. separata. Both peptides also had growth blocking activity in P. includens although larvae had to be injected with higher doses of each peptide to reduce weight gain than was observed for P. separata. However, GBP and PSP1 had little paralytic activity in P. includens. Collectively, our results indicate that GBP and PSP1 are multifunctional, but that some interspecific variation also exists in their growth blocking and paralytic activities. We suggest that all PSP1, GBP, PP and CAP family members are homologs that likely have multiple biological activities. Based upon the unique consensus sequence of their N termini, we propose that these molecules be henceforth referred to as members of the "ENF" peptide family.

Isolation and characterization of CRF-related diuretic hormones from the whitelined sphinx moth Hyles lineata

We have isolated and characterized two diuretic hormones (DH), Hylli-DH41 and Hylli-DH30, from extracts of whole heads of the lepidopteran Hyles lineata. We monitored the isolation by measuring the ability of fractions to affect levels of cyclic AMP production by Malpighian tubules of Manduca sexta maintained in vitro. These DH are related to a family of vertebrate neuropeptides which includes sauvagine, corticotropin-releasing factor (CRF), and urotensin I. Both Hylli-DH41 (RMPSLSIDLPMSVLRQKLSLE KERKVQALRAAANRNFLNDI-NH2) and Hylli-DH30 (SFSVNPAVEILQHRYMEKVAQNNRNFLNRV-NH2) show extremely high similarity with two DH from the tobacco hornworm M. sexta. This is not surprising because both H. lineata and M. sexta are sphingid moths. The discovery of these DH provides a third example of two CRF-related DH occurring in one insect species.