Expression of a recombinant molt-inhibiting hormone of the kuruma prawn Penaeus japonicus in Escherichia coli

Moult-inhibiting fusion protein augments while polyclonal antisera attenuate moult stages and duration in Penaeus monodon

Moulting in crustaceans is regulated by moult-inhibiting hormone (MIH) of the CHH family neuropeptides. The inhibitory functions of MIH have pivotal roles in growth and reproduction of Penaeus monodon. In this study, we report the expression of a thioredoxin-fused mature MIH I protein (mf-PmMIH I) of P. monodon in a bacterial system and its use as antigen to raise polyclonal antiserum (anti-mf-PmMIH I). The mature MIH I gene of 231bp, that codes for 77 amino acids, was cloned into the Escherichia coli thioredoxin gene fusion expression system. The translation expression vector construct (mf-PmMIH I+pET32a+) upon induction produced 29.85kDa mature MIH I fusion protein (mf-PmMIH I). The purified fusion protein was used as exogenous MIH I and as antigen to raise polyclonal antisera. When fusion protein (mf-PmMIH I) was injected into D2 and D3 stages of juvenile shrimp, the moult cycle duration was extended significantly to 16.67±1.03 and 14.67±1.03days respectively compared to that of 11.67±1.03days in controls. Moult duration was further reduced to 8.33±0.82days when polyclonal antiserum (anti-mf-PmMIH I - 1:500 dilutions) was injected. Anti-mf-PmMIH I immunolocalized MIH I producing neurosecretory cells in the eyestalk of P. monodon. In short, the present manuscript reports an innovative means of moult regulation in P. monodon with thioredoxin fused MIH I and antisera developed.

Structure-activity relationship of crustacean peptide hormones

In crustaceans, various physiological events, such as molting, vitellogenesis, and sex differentiation, are regulated by peptide hormones. To understanding the functional sites of these hormones, many structure-activity relationship (SAR) studies have been published. In this review, the author focuses the SAR of crustacean hyperglycemic hormone-family peptides and androgenic gland hormone and describes the detailed results of our and other research groups. The future perspectives will be also discussed.

New functions of arthropod bursicon: inducing deposition and thickening of new cuticle and hemocyte granulation in the blue crab, Callinectes sapidus

Arthropod growth requires molt-associated changes in softness and stiffness of the cuticle that protects from desiccation, infection and injury. Cuticle hardening in insects depends on the blood-borne hormone, bursicon (Burs), although it has never been determined in hemolymph. Whilst also having Burs, decapod crustaceans reiterate molting many more times during their longer life span and are encased in a calcified exoskeleton, which after molting undergoes similar initial cuticle hardening processes as in insects. We investigated the role of homologous crustacean Burs in cuticular changes and growth in the blue crab, Callinectes sapidus. We found dramatic increases in size and number of Burs cells during development in paired thoracic ganglion complex (TGC) neurons with pericardial organs (POs) as neurohemal release sites. A skewed expression of Burs β/Burs α mRNA in TGC corresponds to protein contents of identified Burs β homodimer and Burs heterodimer in POs. In hemolymph, Burs is consistently present at ∼21 pM throughout the molt cycle, showing a peak of ∼89 pM at ecdysis. Since initial cuticle hardness determines the degree of molt-associated somatic increment (MSI), we applied recombinant Burs in vitro to cuticle explants of late premolt or early ecdysis. Burs stimulates cuticle thickening and granulation of hemocytes. These findings demonstrate novel cuticle-associated functions of Burs during molting, while the unambiguous and constant presence of Burs in cells and hemolymph throughout the molt cycle and life stages may implicate further functions of its homo- and heterodimer hormone isoforms in immunoprotective defense systems of arthropods.

Natural and synthetic chiral isoforms of crustacean hyperglycemic hormone from the crayfish Astacus leptodactylus: hyperglycemic activity and hemolymphatic clearance

In the crayfish Astacus leptodactylus, as in several crustacean species, the crustacean hyperglycemic hormone is present as two isoforms differing by the chirality of the third residue, a phenylalanine. In the present work, isoforms synthesized full length by solid-phase peptide synthesis have been purified, refolded, the location of the disulfide bridges has been checked, their immunoreactivity against different antibodies have been analyzed and their hyperglycemic activity tested, to ensure the identity of the synthetic peptides with their natural homologs. Different parameters of the hyperglycemic activity of both isoforms were studied. In addition to a difference in the kinetics of hyperglycemia, already known from other studies, it was observed that the dose-response was different depending on the season where experiments were performed, the response being stronger in spring than in autumn, especially for the d-Phe containing isoform. A dosage method based on sandwich enzyme linked immunosorbent assay (ELISA) has been developed to measure hemolymphatic levels of the isoforms after spiking of the animals with one isoform or the other. It was found that hemolymphatic clearance was identical for both isoforms, indicating that their differential effect is not linked to their different lifetime in the hemolymph but may rather rely on other mechanisms such as their binding to different target tissues.

Novel protocol for the chemical synthesis of crustacean hyperglycemic hormone analogues--an efficient experimental tool for studying their functions

The crustacean Hyperglycemic Hormone (cHH) is present in many decapods in different isoforms, whose specific biological functions are still poorly understood. Here we report on the first chemical synthesis of three distinct isoforms of the cHH of Astacus leptodactylus carried out by solid phase peptide synthesis coupled to native chemical ligation. The synthetic 72 amino acid long peptide amides, containing L- or D-Phe³ and (Glp¹, D-Phe³) were tested for their biological activity by means of homologous in vivo bioassays. The hyperglycemic activity of the D-isoforms was significantly higher than that of the L-isoform, while the presence of the N-terminal Glp residue had no influence on the peptide activity. The results show that the presence of D-Phe³ modifies the cHH functionality, contributing to the diversification of the hormone pool.

Molt-inhibiting hormone from Chinese mitten crab (Eriocheir sinensis): Cloning, tissue expression and effects of recombinant peptide on ecdysteroid secretion of YOs

Molt-inhibiting hormone (MIH), a member of the crustacean hyperglycemic hormone (CHH) family, inhibits the synthesis of ecdysteroid in Y-organ (YO) and plays a significant role in the regulation of molting and growth of crustaceans. A complete cDNA sequence encoding MIH (Ers-MIH, GenBank Accession No.: DQ341280) was cloned from eyestalk of Chinese mitten crab (Eriocheir sinensis) by 5' and 3' RACEs and PCR cloning. The full-length cDNA consists of 1457 bp with a 330 bp open reading frame, encoding 110 amino acids, containing a 75 amino acid mature peptide. The deduced amino acid sequence contains a typical CHH domain. Transcripts of Ers-MIH mRNA were detected in eyestalk by Northern blotting. The production of purified recombinant Ers-MIH (rErs-MIH) expressed in Escherichia coli was 0.3g/L. The LC-ESI-MS analysis showed that two peptide fragments of the recombinant protein were identical to the deduced amino acid sequence of Ers-MIH. By in vitro assay on E. sinensis YOs, a cGMP mediated suppression of rErs-MIH on ecdysteroidogenesis could be observed. Accumulation of cGMP in YOs showed a concentration-dependent manner within 0.01-1 nmol/mL of rErs-MIH; ecdysteroid secretion was inhibited significantly at the range of 0.01-100 nmol/mL rErs-MIH; furthermore, a significant inhibition effect on ecdysteroid releasing was shown when cGMP analog (8-Br-cGMP) concentration rose up to 100 nmol/mL. This study would facilitate to investigate the roles of MIH in molt cycle regulation.

Inhibitory effect of molt-inhibiting hormone on phantom expression in the Y-organ of the kuruma prawn, Marsupenaeus japonicus

Molting in crustaceans is induced by ecdysteroids as in insects. The ecdysteroid titre in hemolymph is negatively regulated by molt-inhibiting hormone (MIH) that inhibits the secretion of ecdysteroids from the Y-organ, an ecdysteroid-producing gland of crustaceans, whereas little is known about the molecular mechanism of inhibition by MIH. Recently, the Halloween genes encoding cytochrome P450 monooxygenases were characterized as the steroidogenic enzymes in insects. To elucidate whether the ecdysteroidogenesis in the Y-organ is regulated by molt-inhibiting hormone (MIH), we analyzed the expression level of an orthologue of a member of the Halloween genes, phantom (Cyp306a1, phm), in the Y-organ of a decapod crustacean, Marsupenaeus japonicus. A cDNA encoding phm (Mj-phm) was cloned by degenerate PCR and 5'- and 3'-RACEs. The deduced amino acid sequence of Mj-phm showed about 40% identity to those of insect phm. The six motif sequences and the four substrate recognition sites were well conserved between Mj-PHM and other PHM. RT-PCR showed the specific expression of Mj-phm mRNA in the Y-organ. In addition, quantitative real-time PCR verified that the expression level of Mj-phm was significantly increased at the pre-molt stage and decreased after ecdysis. Furthermore, exposure of the Y-organ to MIH significantly decreased the Mj-phm expression level in vitro. These results indicate that the transcription of Mj-phm in the Y-organ may be regulated by the inhibitory mechanism of MIH of M. japonicus, which involves the consequent negative regulation of ecdysteroidogenesis at the transcriptional level.

The specific binding sites of eyestalk- and pericardial organ-crustacean hyperglycaemic hormones (CHHs) in multiple tissues of the blue crab, Callinectes sapidus

Crustacean hyperglycaemic hormone from the pericardial organ (PO-CHH) is a CHH-related neuropeptide but its function and target tissues are not known in crustaceans. To investigate this issue, we employed radiolabelled ligand binding and cGMP assays, using eyestalk-CHH (ES-CHH) as a reference neuropeptide. The membranes were prepared from various tissues of Callinectes sapidus: hepatopancreas, hindgut, midgut, gills, heart, abdominal muscles and scaphognathites. Like ES-CHH, recombinant PO-CHH (rPO-CHH) specifically bound to the membranes of scaphognathites=abdominal muscles>midgut>gills> heart>hindgut and hepatopancreas (list order corresponds to the number of binding sites). The specific binding sites of (125)I-ES-CHH in hepatopancreas and gills were saturable and displaceable. The abdominal muscle membrane binding sites were specific and saturable to both CHHs. These binding sites were displaced by homologous neuropeptides, but poorly displaced by the heterologous counterpart. As for the second messenger, the expected increment (3- to >20-fold) in the amount of cGMP produced by ES-CHH was noted in most tissues tested except midgut. Recombinant PO-CHH increased cGMP production 1.5- to 4-fold in scaphognathites, heart, midgut, hindgut and abdominal muscles. The results obtained from the binding study suggest that PO-CHH also has multiple target tissues of which abdominal muscles and scaphognathites are the primary ones. The differences in the primary amino acid sequences of PO-CHH and ES-CHH, particularly in the C-terminal region and in the amidation at C-terminus, may contribute to the truncated responses of hyperglycaemia, cGMP stimulation and binding affinity.

A convenient method for preparation of biologically active recombinant CHH of the kuruma prawn, Marsupenaeus japonicus, using the bacterial expression system

Crustacean hyperglycemic hormone (CHH) not only plays an important role in the modulation of hemolymph glucose level but also functions in other biological events including molting, reproduction and stress response. Of the six CHHs characterized in Marsupenaeus japonicus, an expression system for recombinant Pej-SGP-VII (rPej-SGP-VII-amide) has not yet been established. Here, we established a procedure using a Nus-tag for solubilization, thereby soluble and biologically active rPej-SGP-VII-amide could successfully be obtained by a simpler procedure than previous ones used for producing other recombinant Pej-SGPs (Pej-SGP-I, III and IV). It was found that rPej-SGP-VII-amide thus obtained had the correct arrangement of intramolecular disulfide bonds and helix-rich secondary structure. The established expression system for rPej-SGP-VII-amide may be applicable for the preparation of other recombinant CHHs.

Molecular cloning and expression analysis of ecdysone receptor and retinoid X receptor from the kuruma prawn, Marsupenaeus japonicus

Two cDNAs encoding EcR (MjEcR) and RXR (MjRXR) were cloned and sequenced from the kuruma prawn Marsupenaeus japonicus using PCR techniques. The amino acid sequence of MjEcR was similar to that of known EcR especially in the ligand binding domain (LBD) of insect EcR. The DNA binding domain of MjRXR showed higher homology with that of insect USP (>90% identity) than vertebrate RXR ( approximately 85% identity), while LBD of MjRXR is more homologous with that of vertebrate RXR ( approximately 65% identity) than that of insect USP (30-60% identity). The transcripts of MjEcR and MjRXR were expressed in all tissues examined and in particular, highly in Y-organ and heart and in ovary and heart, respectively. Quantitative real-time PCR analyses revealed that the expression level of MjEcR in hepatopancreas and thoracic muscle increased from intermolt to premolt stages. The analyses also showed that the expressions of MjEcR and MjRXR were regulated in a tissue-specific manner. No significant changes were observed in reproductive organs throughout the molting stages, and MjRXR was expressed much more than MjEcR at all stages. These data suggest that MjRXR mediates a certain hormonal signal related to reproduction.

Molecular characterization and gene expression pattern of two putative molt-inhibiting hormones from Litopenaeus vannamei

Two cDNA sequences (Liv-MIH1 and Liv-MIH2) were cloned from the eyestalk ganglia of the white shrimp Litopenaeus vannamei. The conceptually translated peptide precursors consist of a mature peptide (77 residues for Liv-MIH1, 75 residues for Liv-MIH2), preceded by a 28-residue signal peptide. Both mature peptides share highest sequence identity with other known MIHs, and contain several conserved residues that have been proposed to be functionally critical for MIH activity. Analysis of genomic sequences reveals that both genes are organized in a 3 exon/2 intron manner, with the same sites of intron insertion. The transcripts of Liv-MIH1 and Liv-MIH2 were detected exclusively in the eyestalk, but not in other neural and non-neural tissues examined. Phylogenetic analysis indicates that Liv-MIH1 and Liv-MIH2 cluster with the type II peptides that are considered as penaeid MIH. In addition, a quantitative real-time polymerase chain reaction (PCR) assay was developed and validated for the quantification of gene expression of Liv-MIH1 and Liv-MIH2. Transcript levels for both genes remained constant through stages A - D(1') (ranges of relative expression levels are 97.9+/-2.9 to 104.5+/-8.9% for Liv-MIH1, and 85.6+/-6.7 to 104.7+/-10.8% for Liv-MIH2), and declined afterwards, reaching a lowest level during stage D(2)D(3) (40.6+/-0.4% for Liv-MIH1, and 48.5+/-3.2% for Liv-MIH2). These significant decreases in the transcript levels correspond to a significant increase in hemolymph ecdysteroid titers at stage D(2)D(3). These results clearly indicate that Liv-MIH1 and Liv-MIH2 are type II peptides of the crustacean hyperglycemic hormone family and most likely function as MIHs in the white shrimp. They are discussed with regard to the presence of multiple MIHs and possible functional divergence of type II peptides in Penaeidae, as well as endocrine regulation of crustacean molting.

Expression of crustacean (Callinectes sapidus) molt-inhibiting hormone in Escherichia coli: characterization of the recombinant peptide and assessment of its effects on cellular signaling pathways in Y-organs

A neuropeptide, molt-inhibiting hormone (MIH), negatively regulates the synthesis of ecdysteroid molting hormones by crustacean Y-organs. We report here the expression of blue crab (Callinectes sapidus) MIH in Escherichia coli. Bacteria were transformed with an expression plasmid containing a cDNA insert encoding MIH. After induction of protein synthesis, recombinant MIH (recMIH) was detected in the insoluble fraction of cell lysates. The insoluble recMIH was refolded and purified by reversed-phase high performance liquid chromatography (RP-HPLC). The refolded peptide was MIH-immunoreactive and comigrated with native MIH on RP-HPLC. Mass and CD spectral analyses showed the mass number and secondary structure of the recombinant peptide were as predicted for MIH. Bioassays showed recMIH dose-dependently suppresses ecdysteroid synthesis by Y-organs. The combined results suggest that recMIH is properly folded. In subsequent experiments, recMIH was used to assess cellular signaling pathways linked to MIH-mediated suppression of ecdysteroidogenesis. Incubation of Y-organs with recMIH produced an increase in intracellular cGMP content, but had no effect on intracellular cAMP. Further, a cGMP analog significantly suppressed ecdysteroid production, but neither cAMP analogs nor an activator of adenylyl cyclase had a detectable effect on ecdysteroidogenesis. The results are consistent with the hypothesis that MIH-induced suppression of ecdysteroidogenesis in Y-organs of C. sapidus is mediated by a cGMP second messenger. We anticipate recMIH will be a useful tool for additional studies of the cellular actions and physiological functions of MIH.

Characterization of a Molt-Inhibiting Hormone (MIH) Receptor in the Y-Organ of the Kuruma Prawn,Marsupenaeus japonicus

To characterize a receptor for molt-inhibiting hormone (MIH) in the kuruma prawn, Marsupenaeus japonicus, we performed a binding assay and chemical cross-linking experiments using radiolabeled recombinant MIH ([(125)I]rMIH). The specific binding of [(125)I]rMIH was found in the membrane fraction of the Y-organ (K(d) = 4.76 x 10(-10) M and B(max) = 5.51 x 10(-12) M). Chemical cross-linking between [(125)I]rMIH and the membrane fraction of the Y-organ revealed that the MIH receptor protein has a molecular size of approximately 70 kDa.

The effects of crustacean hyperglycemic hormone-family peptides on vitellogenin gene expression in the kuruma prawn, Marsupenaeus japonicus

In crustaceans, eyestalk ablation induces gonadal maturation of which vitellogenin gene expression is an essential step. However, the molecular mechanisms by which the hormones produced by the X-organ/sinus gland complex in the eyestalk regulate vitellogenesis remain poorly understood. We therefore investigated the effects of sinus gland extracts and certain sinus gland peptides belonging to the crustacean hyperglycemic hormone peptide family on vitellogenin gene expression in ovarian fragments of immature kuruma prawn, Marsupenaeus japonicus. Vitellogenin mRNA levels in incubated ovarian fragments were significantly higher than those in unincubated ovarian fragments prepared from the same animal. Sinus gland extracts and sinus gland peptide-III (type I peptide) both reduced vitellogenin mRNA levels in a dose-dependent manner. In contrast, neither molt-inhibiting hormone (sinus gland peptide-IV) nor molt-inhibiting hormone B, both of which are type II peptides, exerted significant effects on vitellogenin mRNA levels. These results suggest that, in the immature ovary, sinus gland peptide-III is involved in the suppression of vitellogenin gene expression. The existence of such a peptide in the X-organ/sinus gland complex provides a rationale for the significant increase in vitellogenin mRNA levels in the ovaries of eyestalk-ablated prawns.

In vivoEffects of a Recombinant Molt-Inhibiting Hormone on Molt Interval and Hemolymph Ecdysteroid Level in the Kuruma Prawn, Marsupenaeus japonicus

In order to determine the function of molt-inhibiting hormone (MIH) in vivo, we examined the effects of injecting of a recombinant MIH on the molt interval and hemolymph ecdysteroid level in the kuruma prawn, Marsupenaeus japonicus. The injection of recombinant MIH significantly prolonged the molt interval (9.0 +/-0.4 days in the control group, 9.5+/-0.5 days in the 2500 ng/g-body weight/injection-group, mean+/-SD), and significantly decreased the hemolymph ecdysteroid level (ratio of levels between after and before injection: 1.94+/-1.09 in the control and 1.28+/-0.39 in the 3000 ng/g-body weight/injection-group, mean+/-SD). These results conclusively show the inhibitory effects of MIH on molting in vivo.

Cloning and characterization of a molt-inhibiting hormone-like peptide from the prawn Marsupenaeus japonicus

Recently, it was demonstrated by PCR amplification that an additional molt-inhibiting hormone (MIH)-like peptide was present in the kuruma prawn Marsupenaeus japonicus. In this study, a cDNA encoding this peptide designated Pej-MIH-B was cloned. The Pej-MIH-B gene was expressed strongly in the nerve cord, and weakly in the eyestalk. It was possible to isolate Pej-MIH-B from the sinus glands in the eyestalks. The recombinant Pej-MIH-B expressed in Escherichia coli showed low molt-inhibiting activity, but did not exhibit hyperglycemic activity. These results suggest that Pej-MIH-B does not function as MIH or CHH intrinsically, but may have some unknown functions.

The solution structure of molt-inhibiting hormone from the Kuruma prawn Marsupenaeus japonicus

Molting in crustaceans is controlled by molt-inhibiting hormone (MIH) and ecdysteroids. It is presumed that MIH inhibits the synthesis and the secretion of ecdysteroids by the Y-organ, resulting in molt suppression. The amino acid sequence of MIH is similar to that of crustacean hyperglycemic hormone (CHH), and therefore, they form a peptide family referred to as the CHH family. Most of the CHH family peptides show no cross-activity, whereas a few peptides show multiple hormonal activities. To reveal the structural basis of this functional specificity, we determined the solution structure of MIH from the Kuruma prawn Marsupenaeus japonicus and compared the solution structure of MIH with a homology-modeled structure of M. japonicus CHH. The solution structure of MIH consisted of five alpha-helices and no beta-structures, constituting a novel structural motif. The homology-modeled structure of M. japonicus CHH was very similar to the solution structure of MIH with the exception of the absence of the N-terminal alpha-helix and the C-terminal tail, which were sterically close to each other. The surface properties of MIH around this region were quite different from those of CHH. These results strongly suggest that this region is a functionally important site for conferring molt-inhibiting activity.

Significance of a carboxyl-terminal amide moiety in the folding and biological activity of crustacean hyperglycemic hormone

Recombinant peptides related to Pej-SGP-I, one of several crustacean hyperglycemic hormones (CHHs) existing in the kuruma prawn Penaeus japonicus, were expressed in bacterial cells, and then purified after being allowed to refold. Their circular dichroism spectra suggested that the recombinant Pej-SGP-I having a free carboxyl-terminus (rPej-SGP-I-OH) differed slightly in secondary structure from the recombinant Pej-SGP-I having an amidated C-terminus (rPej-SGP-I-amide). The hyperglycemic activity of rPej-SGP-I-amide was comparable to that of natural Pej-SGP-I, whereas rPej-SGP-I-OH showed weaker hyperglycemic activity by approximately one order of magnitude. These results indicate that the C-terminal amide of CHH affects secondary structure and is significant in conferring hyperglycemic activity.

Antipeptide antibodies for detecting crab (Callinectes sapidus) molt-inhibiting hormone

In crustaceans, the synthesis of ecdysteroid molting hormones is regulated by molt-inhibiting hormone (MIH), a neuropeptide produced by an eyestalk neuroendocrine system, the X-organ/sinus gland complex. Using sequence analysis software, two regions of the blue crab (Callinectes sapidus) MIH peptide were selected for antibody production. Two 14-mer peptides were commercially synthesized and used to generate polyclonal antisera. Western blot analysis revealed that each antiserum bound to proteins of the predicted size in extracts of C. sapidus sinus glands, and lysates of insect cells containing recombinant MIH. Thin section immunocytochemistry using either antiserum showed specific immunoreactivity in X-organ neurosecretory cell bodies, their associated axons and collaterals, and their axon terminals in the sinus gland.

Preparation of an active recombinant peptide of crustacean androgenic gland hormone

In crustaceans, male sexual characteristics are induced by a hormone referred to as androgenic gland hormone. We have recently cloned a candidate cDNA in the terrestrial isopod Armadillidium vulgare. In order to prove that this cDNA encodes the hormone, recombinant single-chain precursor molecules consisting of B chain, C peptide and A chain were produced using both baculovirus and bacterial expression systems. Neither recombinant precursors showed activity. Digestion of only the precursor carrying a glycan moiety with lysyl endopeptidase gave a heterodimeric peptide with hormonal activity by removing a part of C peptide. These results indicate that the cDNA encodes the hormone.

Expression of crustacean (Callinectes sapidus) molt-inhibiting hormone in insect cells using recombinant baculovirus

Molt-inhibiting hormone (MIH) negatively regulates the synthesis of ecdysteroid molting hormones by crustacean Y-organs. We report here the expression of blue crab (Callinectes sapidus) MIH in insect cells using recombinant baculovirus. Insect Sf9 cells were transfected with recombinant baculovirus containing a DNA insert encoding the C. sapidus MIH prohormone (signal sequence plus mature hormone). The construct was designed to yield a mature, fully processed recombinant MIH (recMIH). Several baculovirus recombinants showing no contamination with wild-type viral DNA were subsequently analyzed for their ability to direct expression of recMIH. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins from infected cells revealed time-dependent expression of two proteins of approximately the predicted size for the C. sapidus MIH prohormone and mature hormone. Western blot results (using antiserum against MIH of Carcinus maenas) indicated that the proteins were MIH-immunoreactive. N-Terminal amino acid sequence data and mass spectral analysis indicated the expressed proteins were of the correct sequence and molecular mass. Cell lysates containing the recombinant protein dose-dependently suppressed the synthesis of ecdysteroids by Y-organs in vitro. We anticipate the recombinant peptide will prove useful for studies of the structure and function of MIH.

Immunological identification of crustacean androgenic gland hormone, a glycopeptide

Androgenic gland hormone (AGH) is known to be responsible for sex differentiation in crustaceans. The amino acid sequence of AGH-active fraction purified from androgenic glands of the terrestrial isopod Armadillidium vulgare was determined by immunoprecipitation employing three types of antibodies raised against differing parts of the amino acid sequence deduced from the putative AGH cDNA sequence. As all antibodies adsorbed AGH activity, it was confirmed that the sequence examined was that of AGH. The affinity of AGH to certain lectins indicated that AGH possesses a carbohydrate moiety, which is in agreement with the observation that AGH possesses an N-glycosylation consensus sequence.

The molt-inhibiting hormone in the American crayfish Procambarus clarkii: its chemical synthesis and biological activity

The molt-inhibiting hormone of the American crayfish Procambarus clarkii (Prc-MIH), a 75-residue polypeptide containing three disulfide bridges, was synthesized by chemical ligation of two peptides, i.e., synthetic Prc-MIH(1-39) and Prc-MIH(40-75)-NH(2), and by subsequent folding to form the native disulfide-containing peptide molecule. The synthetic peptide was comparable to the natural Prc-MIH in inhibiting ecdysteroid secretion by in vitro bioassay and shared features with the natural Prc-MIH in some biochemical analyses. These results indicate that the chemical ligation method can be used for the synthesis of Prc-MIH. Furthermore, it was demonstrated that synthetic Prc-MIH has hyperglycemic activity, although the activity was weaker than that of the authentic crustacean hyperglycemic hormone in the American crayfish. To examine the structural requirement of the Prc-MIH for eliciting biological activity, an antibody raised against the C-terminal region (residues 55-75) and two synthetic peptides, i.e., a core region (residues 1-54) containing three disulfide bridges and the C-terminal region, were utilized. It is suggested that Prc-MIH exerts its activities through coordination between the core region and the C-terminal region.