Two genetic variants of the crustacean hyperglycemic hormone (CHH) from the Australian crayfish, Cherax destructor: detection of chiral isoforms due to posttranslational modification

Neuroendocrine pathways at risk? Simvastatin induces inter and transgenerational disruption in the keystone amphipod Gammarus locusta

The primary focus of environmental toxicological studies is to address the direct effects of chemicals on exposed organisms (parental generation - F0), mostly overlooking effects on subsequent non-exposed generations (F1 and F2 - intergenerational and F3 transgenerational, respectively). Here, we addressed the effects of simvastatin (SIM), one of the most widely prescribed human pharmaceuticals for the primary treatment of hypercholesterolemia, using the keystone crustacean Gammarus locusta. We demonstrate that SIM, at environmentally relevant concentrations, has significant inter and transgenerational (F1 and F3) effects in key signaling pathways involved in crustaceans' neuroendocrine regulation (Ecdysteroids, Catecholamines, NO/cGMP/PKG, GABAergic and Cholinergic signaling pathways), concomitantly with changes in apical endpoints, such as depressed reproduction and growth. These findings are an essential step to improve hazard and risk assessment of biological active compounds, such as SIM, and highlight the importance of studying the transgenerational effects of environmental chemicals in animals' neuroendocrine regulation.

Advancing d-amino acid-containing peptide discovery in the metazoan

The discovery of enzyme-derived d-amino acid-containing peptides (DAACPs) that have physiological importance in the metazoan challenges previous assumptions about the homochirality of animal proteins while simultaneously revealing new analytical challenges in the structural and functional characterization of peptides. Most known DAACPs have been identified though laborious activity-guided purification studies or by homology to previously identified DAACPs. Peptide characterization experiments are increasingly dominated by high throughput mass spectrometry-based peptidomics, with stereochemistry rarely considered due to the technical challenges of identifying l/d isomerization. This review discusses the prevalence of enzyme-derived DAACPs among animals and the physiological consequences of peptide isomerization. Also highlighted are the analytical methods that have been applied for structural characterization/discovery of DAACPs, including results of several recent studies using non-targeted discovery methods for revealing novel DAACPs, strongly suggesting that more DAACPs remain to be uncovered.

Independent and simultaneous effect of crustacean hyperglycemic hormone and dopamine on the hemocyte intracellular signaling pathways and immune responses in white shrimp Litopenaeus vannamei

Immune responses and intracellular signaling pathways were examined after hemolymph of Litopenaeus vannamei being incubated in Crustacean hyperglycemic hormone (CHH), dopamine (DA) and DA antagonist (Y). The results showed that the effect CHH and CHH + DA + Y on viability of hemocytes were no significant changes compared to the control group. However, in DA, DA + Y and CHH + DA groups, the viability of hemocytes decreased significantly. The phagocytic activity and the antibacterial activity of CHH group were increased significantly within 12h. Whereas the CHH + DA, DA were significantly lower than the control. PO in haemolymph was up-regulated after CHH and DA incubation. The proPO has the opposite change in all groups. In addition, DA + Y, CHH + DA + Y has a similar trend with the DA and CHH respectively. Furthermore, a significant increase of cAMP, CaM and cGMP were found in treatment groups except for the CaM concentration of the CHH group and the cGMP concentration of DA group. There is no significant change observed in the CHH group about CaM concentration. Whereas the cGMP of DA group decreased within 12h. The results suggest that DA could depress the immune responses by cAMP-, CaM-pathways. However, the CHH is on the contrary, which transduced the signals from cAMP, cGMP to PKA, PKC and PKG to enhance the immune response parameters.

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.

Functional Assessment of Residues in the Amino- and Carboxyl-Termini of Crustacean Hyperglycemic Hormone (CHH) in the Mud Crab Scylla olivacea Using Point-Mutated Peptides

To assess functional importance of the residues in the amino- and carboxyl-termini of crustacean hyperglycemic hormone in the mud crab Scylla olivacea (Sco-CHH), both wild-type and point-mutated CHH peptides were produced with an amidated C-terminal end. Spectral analyses of circular dichroism, chromatographic retention time, and mass spectrometric analysis of the recombinant peptides indicate that they were close in conformation to native CHH and were produced with the intended substitutions. The recombinant peptides were subsequently used for an in vivo hyperglycemic assay. Two mutants (R13A and I69A rSco-CHH) completely lacked hyperglycemic activity, with temporal profiles similar to that of vehicle control. Temporal profiles of hyperglycemic responses elicited by 4 mutants (I2A, F3A, D12A, and D60A Sco-CHH) were different from that elicited by wild-type Sco-CHH; I2A was unique in that it exhibited significantly higher hyperglycemic activity, whereas the remaining 3 mutants showed lower activity. Four mutants (D4A, Q51A, E54A, and V72A rSco-CHH) elicited hyperglycemic responses with temporal profiles similar to those evoked by wild-type Sco-CHH. In contrast, the glycine-extended version of V72A rSco-CHH (V72A rSco-CHH-Gly) completely lost hyperglycemic activity. By comparing our study with previous ones of ion-transport peptide (ITP) and molt-inhibiting hormone (MIH) using deleted or point-mutated mutants, detail discussion is made regarding functionally important residues that are shared by both CHH and ITP (members of Group I of the CHH family), and those that discriminate CHH from ITP, and Group-I from Group-II peptides. Conclusions summarized in the present study provide insights into understanding of how functional diversification occurred within a peptide family of multifunctional members.

Different transcription regulation routes are exerted by L- and D-amino acid enantiomers of peptide hormones

Conversion of one or more amino acids in eukaryotic peptides to the D-configuration is catalyzed by specific L/D peptide isomerases and it is a poorly investigated post-translational modification. No common modified amino acid and no specific modified position have been recognized and mechanisms underlying changes in the peptide function provided by this conversion were not sufficiently studied. The 72 amino acid crustacean hyperglycemic hormone (CHH) of Astacidea crustaceans exhibits a co-existence of two peptide enantiomers alternately having D- or L-phenylalanine in their third position. It is a pleiotropic hormone regulating several physiological processes in different target tissues and along different time scales. CHH enantiomers differently affect time courses and intensities of examined processes. The short-term effects of the two isomers on gene expression are presented here, examined in the hepatopancreas, gills, hemocytes and muscles of the astacid Pontastacus leptodactylus. Muscles and hemocytes were poorly affected by both isomers. Two CHH modes of action were elucidated in the hepatopancreas and the gills: specific gene induction by D-CHH only, elucidated in both organs and mutual targeted attenuation affected by both enantiomers elucidated in the gills. Consequently a two-receptor system is hypothesized for conveying the effect of the two CHH isomers.

Crustacean hyperglycemic hormone precursor transcripts in the hemocytes of the crayfish Procambarus clarkii: novel sequence characteristics relating to gene splicing pattern and transcript stability

It was demonstrated in a previous study (Wu et al., 2012b) that crustacean hyperglycemic hormone (CHH) gene is expressed in the hemocyte of Procambarus clarkii. In the present study, 2 additional cDNAs (CHH2-L and tCHH2) from the hemocyte and a CHH gene (CHH2) from the abdominal muscle of the same species were cloned. Analyses of the cDNA and genomic sequences suggested that, similar to other previously reported CHH genes, 2 precursor transcripts (CHH2 and CHH2-L) would be derived from CHH2 gene through a process of RNA alternative splicing, and CHH2 and CHH2-L each encode a precursor containing a signal peptide, a CHH precursor-related peptide, and a mature peptide. Further, tCHH2 sequence consists of exon I, exon II, and a truncated segment of intron II of CHH2 gene, followed by a previously unknown 3'sequence. It is suggested that, because the truncation disrupts the highly conserved RNA splice acceptor site, the truncated segment is retained within tCHH2, resulting in encoding a precursor containing the typical precursor components except the mature peptide is truncated with only 40 residues. In addition, unlike 2 other previously identified transcripts (referred to as CHH1 and CHH1-L), CHH2-L, CHH2, tCHH2 contain in the 3'-UTRs 3-5 AU-rich elements (AREs). The data showed that multiple CHH genes are expressed in crayfish hemocytes. Novel sequence characteristics of the transcripts result in an RNA splicing pattern that yields a transcript (tCHH2) encoding a precursor with an atypical truncated mature peptide and possibly leads to a different expression dynamics of the precursors encoded by the ARE-containing transcripts.

Two type I crustacean hyperglycemic hormone (CHH) genes in Morotoge shrimp (Pandalopsis japonica): cloning and expression of eyestalk and pericardial organ isoforms produced by alternative splicing and a novel type I CHH with predicted structure shared with type II CHH peptides

Crustacean hyperglycemic hormone (CHH) peptide family members play critical roles in growth and reproduction in decapods. Three cDNAs encoding CHH family members (Pj-CHH1ES, Pj-CHH1PO, and Pj-CHH2) were isolated by a combination of bioinformatic analysis and conventional cloning strategies. Pj-CHH1ES and Pj-CHH1PO were products of the same gene that were generated by alternative mRNA splicing, whereas Pj-CHH2 was the product of a second gene. The Pj-CHH1 and Pj-CHH2 genes had four exons and three introns, suggesting the two genes arose from gene duplication. The three cDNAs were classified in the type I CHH subfamily, as the deduced amino acid sequences had a CHH precursor-related peptide sequence positioned between the N-terminal signal sequence and C-terminal mature peptide sequence. The Pj-CHH1ES isoform was expressed at a higher level in the eyestalk X-organ/sinus gland (XO/SG) complex and at a lower level in the gill. The Pj-CHH1PO isoform was expressed at higher levels in the XO/SG complex, brain, abdominal ganglion, and thoracic ganglion and at a lower level in the epidermis. Pj-CHH2 was expressed at a higher level in the thoracic ganglion and at a lower level in the gill. Real-time polymerase chain reaction was used to quantify the effects of eyestalk ablation on the mRNA levels of the three Pj-CHHs in the brain, thoracic ganglion, and gill. Eyestalk ablation reduced expression of Pj-CHH1ES in the brain and Pj-CHH1PO and Pj-CHH2 in the thoracic ganglion. Sequence alignment of the Pj-CHHs with CHHs from other species indicated that Pj-CHH2 had an additional alanine at position #9 of the mature peptide. Molecular modeling showed that the Pj-CHH2 mature peptide had a short alpha helix (α1) in the N-terminal region, which is characteristic of type II CHHs. This suggests that Pj-CHH2 differs in function from other type I CHHs.

The CHH-superfamily of multifunctional peptide hormones controlling crustacean metabolism, osmoregulation, moulting, and reproduction

Apart from providing an up-to-date review of the literature, considerable emphasis was placed in this article on the historical development of the field of "crustacean eyestalk hormones". A role of the neurosecretory eyestalk structures of crustaceans in endocrine regulation was recognized about 80 years ago, but it took another half a century until the first peptide hormones were identified. Following the identification of crustacean hyperglycaemic hormone (CHH) and moult-inhibiting hormone (MIH), a large number of homologous peptides have been identified to this date. They comprise a family of multifunctional peptides which can be divided, according to sequences and precursor structure, into two subfamilies, type-I and -II. Recent results on peptide sequences, structure of genes and precursors are described here. The best studied biological activities include metabolic control, moulting, gonad maturation, ionic and osmotic regulation and methyl farnesoate synthesis in mandibular glands. Accordingly, the names CHH, MIH, and GIH/VIH (gonad/vitellogenesis-inhibiting hormone), MOIH (mandibular organ-inhibiting hormone) were coined. The identification of ITP (ion transport peptide) in insects showed, for the first time, that CHH-family peptides are not restricted to crustaceans, and data mining has recently inferred their occurrence in other ecdysozoan clades as well. The long-held tenet of exclusive association with the eyestalk X-organ-sinus gland tract has been challenged by the finding of several extra nervous system sites of expression of CHH-family peptides. Concerning mode of action and the question of target tissues, second messenger mechanisms are discussed, as well as binding sites and receptors. Future challenges are highlighted.

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.

Experimental strategies for the analysis of D-amino acid containing peptides in crustaceans: a review

Detection of D-amino acids in natural peptides has been, and remains a challenging task, as peptidyl isomerization is a peculiar and subtle posttranslational modification that does not induce any change in primary sequence or in physicochemical properties of the molecule such as molecular mass or pI. Therefore, the presence of a D-amino acid residue in a peptide chain is generally transparent to classical methods of peptide analysis (electrophoresis, chromatography, mass spectrometry, molecular biology). In this article, we will review the various experimental strategies and analytical techniques, which have been used to characterize and to study D-amino acid containing peptides in crustaceans.

Cloning and expression profiles of two isoforms of a CHH-like gene specifically expressed in male Chinese shrimp, Fenneropenaeus chinensis

Two full-length cDNA sequences (Fc-CHH1, Fc-CHH2) encoding a crustacean hyperglycemic hormone (CHH) precursor homolog and their DNA sequences were cloned from Chinese shrimp Fenneropenaeus chinensis. The deduced amino acid sequences of them are predicted to contain a signal peptide and a mature peptide. The mature peptides of Fc-CHH1 and Fc-CHH2 shared 78% identity, but they showed low identities (less than 40%) to CHH peptides from other species. Both Fc-CHH1 and Fc-CHH2 proteins contain six highly conserved cysteine residues which are characteristic of the CHH family peptides. The transcripts of Fc-CHH1 and Fc-CHH2 were shown to be specifically present in the spermatophore sac of mature male Chinese shrimp through reverse transcription-polymerase chain reaction (RT-PCR) detection. The transcripts of Fc-CHH1 and Fc-CHH2 begin to appear at the immature stage (115 days after the first post-larvae stage) when the spermatophore sac was first observed to be appeared. In situ hybridization analyses showed that Fc-CHH1 and Fc-CHH2 transcripts located at the epithelial cells in the internal wall of the spermatophore sac. In the cloned DNA sequences of Fc-CHH1 and Fc-CHH2, the predicted transcription factor binding sites in the 5' flanking sequences are different from those previously reported for CHH family genes of crustacean. To our knowledge, these are novel CHH-like genes expressed specifically in male shrimp. Their function needs to be further investigated.

Molecular cloning and differential expression pattern of two structural variants of the crustacean hyperglycemic hormone family from the mud crab Scylla olivacea

Two full-length cDNA sequences encoding a crustacean hyperglycemic hormone (CHH) precursor were cloned from tissues of the mud crab Scylla olivacea. Sco-CHH (S. olivacea CHH) was cloned from eyestalk ganglia, whereas Sco-CHH-L (S. olivacea CHH-like peptide) was cloned from extra-eyestalk tissues (pericardial organ and thoracic ganglia). Each conceptually translated precursor is expected to be processed into a signal peptide, a CHH precursor-related peptide (CPRP), and a mature CHH or CHH-like peptide. The two precursors are identical in amino acid sequence through the 40th residue of the mature peptide, but different from each other substantially in the C-terminus. Both CHH variants contain the six highly conserved cysteine residues characteristic of the CHH family peptides, and share higher sequence identities with other brachyuran CHH sequences than with those of other taxonomic groups. As determined by reverse transcription-polymerase chain reaction (RT-PCR), the transcripts of Sco-CHH and Sco-CHH-L were present in eyestalk ganglia and several extra-eyestalk tissues (the thoracic ganglia, pericardial organ, brain, circumesophageal connectives, and gut). Sco-CHH was the predominant form in eyestalk ganglia, while Sco-CHH-L was the predominant form in several extra-eyestalk tissues. Neither transcript was expressed in the muscle, hepatopancreas, ovary, testis, heart, or gill. Antisera were raised against synthetic peptides corresponding to a stretch of sequence-specific to the C-terminus of Sco-CHH or Sco-CHH-L. Western blot analyses of tissues expressing Sco-CHH and Sco-CHH-L detected a Sco-CHH immunoreactive protein in the sinus gland, and a Sco-CHH-L immunoreactive protein in the pericardial organ. Immunohistochemical analyses of the eyestalk ganglia localized both Sco-CHH and Sco-CHH-L immunoreactivity to the sinus gland, and only Sco-CHH immunoreactivity to the X-organ somata; analyses of the pericardial organs also localized both Sco-CHH and Sco-CHH-L immunoreactivity to the anterior and posterior bars, as well as to longitudinal trunks joining the two bars. The combined data provided supporting evidence that Sco-CHH and Sco-CHH-L are co-localized in the same tissue.

Effects of elevated ecdysteroid on tissue expression of three guanylyl cyclases in the tropical land crab Gecarcinus lateralis: possible roles of neuropeptide signaling in the molting gland

Two eyestalk (ES) neuropeptides, molt-inhibiting hormone (MIH) and crustacean hyperglycemic hormone (CHH), increase intracellular cGMP levels in target tissues. Both MIH and CHH inhibit ecdysteroid secretion by the molting gland or Y-organ (YO), but apparently through different guanylyl cyclase(GC)-dependent pathways. MIH signaling may be mediated by nitric oxide synthase (NOS) and NO-sensitive GC. CHH binds to a membrane receptor GC. As molting affects neuropeptide signaling, the effects of ecdysteroid on the expression of the land crab Gecarcinus lateralis β subunit of a NO-sensitive GC (Gl-GC-Iβ), a membrane receptor GC (Gl-GC-II) and a NO-insensitive soluble GC (Gl-GC-III) were determined. Gl-GC-Iβ isoforms differing in the absence or presence of an N-terminal 32-amino acid sequence and Gl-GC-III were expressed at higher mRNA levels in ES ganglia, gill,hepatopancreas, ovary and testis, and at lower levels in YO, heart and skeletal muscle. Three Gl-GC-II isoforms, which vary in the length of insertions (+18, +9 and +0 amino acids) within the N-terminal ligand-binding domain, differed in tissue distribution. Gl-GC-II(+18) was expressed highly in striated muscle (skeletal and cardiac muscles); Gl-GC-II(+9) was expressed in all tissues examined (ES ganglia, YO, gill, hepatopancreas, striated muscles and gonads); and Gl-GC-II(+0) was expressed in most tissues and was the dominant isoform in ES and thoracic ganglia. ES ablation, which increased hemolymph ecdysteroid, increased Gl-GC-II(+18) mRNA level in claw muscle. Using real-time RT-PCR, ES ablation increased Gl-GC-Iβ, Gl-GC-III and ecdysone receptor mRNA levels in the YOs ∼ten-, ∼four- and∼twofold, respectively, whereas Gl-GC-II mRNA level was unchanged. A single injection of 20-hydroxyecdysone into intact animals transiently lowered Gl-GC-Iβ in hepatopancreas, testis and skeletal muscle, and certain Gl-GC-II isoforms in some of the tissues. These data suggest that YO and other tissues can modulate responses to neuropeptides by altering GC expression.

Molecular cloning of a cDNA encoding a crustacean hyperglycemic hormone from eyestalk ganglia of the blue crab, Callinectes sapidus

Crustacean hyperglycemic hormone (CHH), a polypeptide with multiple physiological effects, was first identified in the X-organ/sinus gland neurosecretory system of the eyestalks. In studies reported here, we used a PCR-based cloning strategy (RT-PCR followed by 5'- and 3'-RACE) to clone from blue crab (Callinectes sapidus) eyestalk ganglia a cDNA (CsCHH-1) encoding a putative CHH preprohormone. Sequence analysis revealed the preprohormone included all structural features previously reported for CHH preprohormones: a signal peptide, a CHH precursor-related peptide (CPRP), the CHH polypeptide, and a C-terminal basic processing site. Further, the deduced amino acid sequence of the mature polypeptide included all signature domains previously reported for CHH. The primary structure of blue crab CHH is most closely related to CHH from other brachyurans. RT-PCR revealed the CsCHH-1 transcript was present in eyestalk ganglia, but was undetectable in other tissues tested. A transcript encoding a similar CHH-like preprohormone was detected in thoracic ganglion, ventral nerve cord, and brain, but was not detected in eyestalk ganglia.

Crustacean hyperglycemic and vitellogenesis-inhibiting hormones in the lobster Homarus gammarus

Crustacean hyperglycemic hormone (CHH) and vitellogenesis-inhibiting hormone (VIH), produced by the X organ-sinus gland neurosecretory complex, belong to a peptide group referred to as the CHH family, which is widely distributed in arthropods. In this study, genetic variants and post-translationally modified isoforms of CHH and VIH were characterized in the European lobster Homarus gammarus. With the use of RP-HPLC and ELISA with specific antibodies that discriminate between stereoisomers of CHH and VIH, two groups of CHH-immunoreactive peaks were characterized from HPLC fractions of sinus gland extract (CHH A and CHH B); each group contained two variants (CHH and D-Phe3CHH). In the same way, two VIH-immunoreactive peaks (VIH and D-Trp4VIH) were demonstrated in HPLC fractions from sinus gland extract. The masses of these different neuropeptides were determined by FT-ICR MS: CHH A and CHH B spectra exhibited monoisotopic ions at 8557.05 Da and 8527.04 Da, respectively, and both VIH isomers displayed an m/z value of 9129.19 Da. Two full-length cDNAs encoding preprohomones of CHH A and CHH B and only one cDNA for VIH precursor were cloned and sequenced from X organ RNA. Comparison of CHH sequences between European lobster and other Astacoidea suggests that the most hydrophobic form appeared first during crustacean evolution.

The crustacean hyperglycemic hormones from an euryhaline crab Pachygrapsus marmoratus and a fresh water crab Potamon ibericum: eyestalk and pericardial isoforms

The structures of crustacean hyperglycemic hormones (CHH) were investigated in two crabs, the coastal euryhaline crab Pachygrapsus marmoratus and the fresh water crab Potamon ibericum. The neuropeptide mRNAs were extracted from pericardial and X-organs (PO and XO), and the sequences of the cDNA encoding the hormones' precursors were determined. The X-organ preprohormones are composed of 29 and 28 amino acid signal peptides in P. marmoratus and P. ibericum respectively, followed by 43 and 41 amino acid crustacean hyperglycemic hormone precursor related peptide (CPRP) flanking the 72 amino acid crustacean hyperglycemic hormones. A similar organization is reported for pericardial preprohormones with identical sequences for the signal peptide, the CPRP and the N-terminal sequences of CHH (1-40), but remaining sequences (41-72 and 41-71) differing considerably. In P. marmoratus two CHH cDNAs were characterized from XO and evidences were obtained for the existence of at least two forms in the PO. From our results and by comparison with other known sequences, a consensus pattern for crab pericardial CHH could be pointed out. Analysis of the data presented in this article using phylogenetic methods reveals that the two crab species studied are much closer than previously predicted.

Biochemical and functional aspects of crustacean hyperglycemic hormone in decapod crustaceans: review and update

In crustaceans, neuroendocrine centers are located in different structures of the nervous system. One of these structures, the X-organ-sinus gland complex of the eyestalk, produces several neuropeptides that belong to the two main functionally different families: firstly, the chromatophorotropins, and secondly, a large family comprising various closely related peptides, commonly named CHH/MIH/GIH family. This review updates some aspects of the structural, biochemical and functional properties of the main hyperglycemic neuropeptide of this family, the crustacean hyperglycemic hormone (CHH). The first part of this work is a survey of the neuroendocrine system that produces the neurohormones of the CHH/MIH/GIH family, focusing on recent reports that propose new possible neuroendocrine loci of CHH production, secondly we revise general aspects of the CHH biochemical, and structural characteristics and thirdly, we present a review of the role of CHH in the regulation of several physiological processes of crustaceans as well as new reports on the ontogenetic aspects of CHH. The review is centered only on one group of malacostracan crustaceans, the Decapoda.

Identification of neuropeptides from the decapod crustacean sinus glands using nanoscale liquid chromatography tandem mass spectrometry

Neurosecretory systems are known to synthesize and secrete a diverse class of peptide hormones which regulate many physiological processes. The crustacean sinus gland (SG) is a well-defined neuroendocrine site that produces numerous hemolymph-borne agents including the most complex class of endocrine signaling molecules--neuropeptides. As an ongoing effort to define the peptidome of the crustacean SG, we determine the neuropeptide complements of the SG of the Jonah crab, Cancer borealis, and the Maine lobster, Homarus americanus, using nanoflow liquid chromatography electrospray ionization quadrupole time-of-flight (ESI-QTOF) MS/MS. Numerous neuropeptides were identified, including orcokinins, orcomyotropin, crustacean hyperglycemic hormone (CHH), CHH precursor-related peptides (CPRPs), red pigment concentrating hormone (RPCH), beta-pigment dispersing hormone (beta-PDH), proctolin and HL/IGSL/IYRamide. Among them, two novel orcokinins were de novo sequenced from the SG of H. americanus. Three CPRPs including a novel isoform were sequenced in H. americanus. Four new CPRPs were sequenced from the SG of C. borealis. Our results show that structural polymorphisms in CPRPs (and thus the CHH precursors) are common in Dendrobranchiata as well as in Pleocyemata. The evolutionary relationship between the CPRPs is also discussed.

Occurrence of L- and D-crustacean hyperglycemic hormone isoforms in the eyestalk X-organ/sinus gland complex during the ontogeny of the crayfish Astacus leptodactylus

We studied the ontogeny of the eyestalk structure and of the L-CHH and d-Phe3-CHH synthesis in the X-organ/sinus gland (XO/SG) complex by light microscopy and immunocytochemistry in the freshwater crustacean Astacus leptodactylus. The optic ganglia start to differentiate in embryos at EI 190 microm (EI: eye index; close to 410 microm at hatching). At EI 270 microm, the three medullae (externa, interna, and terminalis) and the lamina ganglionaris are present and are organized as in the adult eyestalk. The L-CHH was localized in perikarya of neuroendocrine cells, in their tracts, and in SG from the metanauplius stage to the adult. The d-Phe3-CHH was visualized in XO perikarya, in their tracts and in SG of embryos from EI 350 microm and in all later studied stages. Co-localization of both CHH stereoisomers always occurred in the d-Phe3-CHH-producing cells. These results show that the synthesis of CHH enantiomers starts during the embryonic life in A. leptodactylus, and that the d-isomer is synthesized later than its L-counterpart. We discuss the post-translational isomerization as a way to generate hormonal diversity and the putative relation between d-Phe3-CHH synthesis and the ability to osmoregulate, occurring late during the embryonic life of Astacus leptodactylus.

Identification of Neuropeptides from the Sinus Gland of the Crayfish Orconectes limosus Using Nanoscale On-line Liquid Chromatography Tandem Mass Spectrometry

In this article, a novel and sensitive analytical strategy for direct characterization of neuropeptides from the X-Organ-sinus gland neurosecretory system of the crayfish Orconectes limosus is presented. A desalted extract corresponding to 0.5 sinus gland equivalents was analyzed in a nanoflow liquid chromatography system coupled to quadrupole time-of-flight tandem mass spectrometry (nanoLC-QTOF MS/MS). The existence and structural identity of four crustacean hyperglycemic hormone precursor-related peptide variants and two new genetic variants of the pigment-dispersing hormone, not detected by conventional chromatographic systems, molecular cloning, or immunochemical methods before, was revealed. The here-presented approach of the combined LC-QTOF MS/MS technique is a powerful tool to discover new peptide hormones in biological systems, due to its sensitivity, accuracy, and speed.