Cloning and sequence analysis of cDNA for precursor of a crustacean hyperglycemic hormone

Cloning and expression of mRNA encoding prepro-gonad-inhibiting hormone (GIH) in the lobster Homarus americanus

The gonad-inhibiting hormone (GIH) is produced in the eyestalk X-organ sinus gland complex of male and female lobsters, and plays a prominent role in the regulation of reproduction, e.g. inhibition of vitellogenesis in female animals. To study this neurohormone at the mRNA level, we cloned and sequenced a cDNA which encodes GIH in the lobster Homarus americanus. The structure of preproGIH consists of a signal peptide and the GIH peptide itself. A comparative analysis revealed that lobster GIH, together with crab molt-inhibiting hormone, belongs to a separate group of the crustacean hyperglycemic hormone (CHH) peptide family which seems to be unique for crustaceans. Expression studies showed that GIH mRNA is expressed in the eyestalk, indicating that the neuroendocrine center in this optic structure is the only source of GIH. As this center modulates the other (neuro)endocrine organs in crustaceans, it is postulated that GIH regulates production and release of hormones involved in reproduction/molting processes.

Cloning and expression of two crustacean hyperglycemic-hormone mRNAs in the eyestalk of the crayfish Orconectes limosus

Crustacean hyperglycemic hormone (CHH) is a multifunctional neurohormone produced in the eyestalk of crustaceans and is primarily involved in the regulation of carbohydrate metabolism. In several crustacean species, CHH isoforms with identical amino acid sequences and molecular masses, but with different chromatographic elution patterns, are synthesized. To obtain sequence information on the CHH preprohormone in the crayfish Orconectes limosus we isolated two full-length cDNAs encoding two structurally different preproCHH species. The sequences of these precursors differ slightly in the signal peptide, the CHH-precursor-related peptide(CPRP)-coding sequences and in the non-coding regions, but are identical in the CHH peptide-coding sequence. Determination of the levels of preproCHH mRNAs and the amount of CHH peptide in the eyestalks of individual animals revealed that the ratio between the two preproCHH mRNAs varies for different individuals while the ratio between the two CHH peptide isoforms does not differ among animals. Our results suggest that the existence of two CHH isoforms in the crayfish O. limosus is due to a post-translational modification event. Northern-blot analysis showed only one band in eyestalk tissue with a size of approximately 2.4 kb, similar to the sizes of the cDNA sequences. Southern-blot analysis revealed the presence of at least two preproCHH genes in the crayfish suggesting a gene duplication event. Slight modifications in the duplicated genes could be responsible for the existence of the two preproCHH-encoding mRNAs.

Molecular cloning of crustacean putative molt-inhibiting hormone (MIH) precursor

A cDNA encoding the complete precursor of the putative molt-inhibiting hormone (MIH) of the shore crab, Carcinus maenas, was isolated and sequenced. The precursor consists of a putative 35 amino acid signal peptide and the 78 amino acid mature MIH. The deduced MIH amino acid sequence is in complete agreement with the sequence previously determined by Edman degradation. In situ hybridization revealed MIH-expression in a subpopulation of large neurosecretory perikarya of the medulla terminalis X-organ in the eyestalk.

Isolation and molecular characterization of a hyperglycemic neuropeptide from the sinus gland of the terrestrial isopod Armadillidium vulgare (Crustacea)

The major peptide from the sinus gland of the terrestrial isopod Armadillidium vulgare (Crustacea) has been extracted and purified by reverse-phase HPLC. This neuropeptide exhibited a high hyperglycemic activity and was therefore named A. vulgare crustacean hyperglycemic hormone (Arv-CHH). Its average molecular mass measured by mass spectrometry was 8729.3 Da. Its complete amino acid sequence was determined by a combination of Edman degradation and mass spectrometry. The N-terminal amino acid was found to be unblocked, the C-terminal residue was found amidated and none of the other 72 residues was affected by any post-translational modification. Disulfide bond assignment was made unambiguously by mass spectrometry and Edman degradation was performed on peptides produced by enzymatic cleavage. Relationships with other, similar neuropeptides from decapod sinus glands are discussed.

Molecular cloning of crustacean pigment dispersing hormone precursor

The cDNA encoding the precursor of the pigment dispersing hormone (PDH) of the shore crab, Carcinus maenas, was isolated and sequenced. The precursor consists of a putative 22 amino acid signal peptide, a putative 33 residue peptide of unknown function, and the 18 amino acid mature PDH, followed by a Gly residue which serves as a possible amide donor. The deduced mature PDH amino acid sequence is identical to those of Uca pugilator and Cancer magister, previously determined by Edman degradation.

Localization of messenger RNAs encoding crustacean hyperglycemic hormone and gonad inhibiting hormone in the X-organ sinus gland complex of the lobster Homarus americanus

The localization of messenger RNAs encoding the crustacean hyperglycemic hormone, involved in regulation of carbohydrate metabolism and the gonad inhibiting hormone, which inhibits vitellogenesis, was studied in the eyestalk of the lobster Homarus americanus using complementary RNA probes for in situ hybridization. For the detection of gonad inhibiting hormone messenger RNA, we cloned and sequenced a partial complementary DNA encoding lobster gonad inhibiting hormone and for crustacean hyperglycemic hormone messenger RNA detection an available complementary DNA was used. This approach reveals that there is a frequent but inconsistent cellular co-localization of the two neurohormones. Furthermore, our data show that male lobsters contain an equal number of neuroendocrine gonad inhibiting hormone cells as female lobsters. An additional study, involving the use of in situ hybridization in combination with immunocytochemistry, shows that the synthetic activity of the crustacean hyperglycemic hormone- and gonad inhibiting hormone-producing cells can be followed at the messenger RNA as well as the protein level. This reveals that when strong immunostaining is present, the messenger RNA staining is usually weak or absent and vice versa. In conclusion, the presence of cells, containing only gonad inhibiting hormone messenger RNA or only crustacean hyperglycemic hormone messenger RNA, indicates that lobster crustacean hyperglycemic hormone and gonad inhibiting hormone originate from two different precursors. Co-localization of the two neurohormone messenger RNAs confirms the co-localization at the peptidergic level found by immunocytochemistry and thus these findings were not due to cross-reactions between the two antisera.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of the mRNA encoding vitellogenesis inhibiting hormone in neurosecretory cells of the X-organ in Homarus americanus by in situ hybridization

Vitellogenesis inhibiting hormone (VIH)-mRNA in secretory cells of the eyestalk of Homarus americanus was detected by nonradioactive in situ hybridization (ISH) using two digoxigenin-tailed oligonucleotide probes deduced from the peptide sequence. Two distinct clusters of positive cells were observed in the medulla terminalis ganglionic X-organ (MGTX). Only one of them gave a strong immunoreaction after incubation with a specific polyclonal anti-VIH serum and corresponded to the conventionally described VIH producing cells. The significance of the cells reacting positively in ISH but not in immunocytochemistry (ICC) is discussed. Northern blot analysis using 32P-labeling confirms the specificity of the probes and indicates an approximate size of 2.5 kb for VIH mRNA.

Fine structure of the neurohemal sinus gland of the shore crab, Carcinus maenas, and immuno-electron-microscopic identification of neurosecretory endings according to their neuropeptide contents

The sinus gland of the shore crab, Carcinus maenas, is a compact assembly of interdigitating neurosecretory axon endings abutting upon the thin basal lamina of a central hemolymph lacuna. Four types of axon endings are distinguishable by the size distribution, shape, electron density and core structure of their neurosecretory granules. One additional type of axon ending is characterized by electron-lucent vacuoles and vesicles. The axon profiles are surrounded by astrocyte-like glial cells. Various fixations followed by epoxy- or Lowicryl-embedding were compared in order to optimize the preservation of the fine structure of the granule types and the antigenicity of their peptide hormone contents. By use of specific rabbit antisera, the crustacean hyperglycemic, molt-inhibiting, pigment-dispersing, and red-pigment-concentrating hormones were assigned to the four distinct granule types which showed no overlap of immunostaining. Epi-polarization microscopy and ultrathin section analysis of immunogold-stained Lowicryl-embedded specimens revealed that immunoreactivity to Leu-enkephalin and proctolin is co-localized with molt-inhibiting hormone immunoreactivity in the same type of granule. The size and core structure of the immunocytochemically identified granule types vary little with the different pretreatments but, in some cases, to a statistically significant extent. The present results are compared with those from earlier studies of sinus glands in different crustaceans. The methods of granule identification used in this study supplement the classical approach in granule typing; they are easier to perform and more reliable for the analysis of release phenomena in identified secretory neurons supplying the neurohemal sinus gland.

Crustacean neuropeptides: structures, functions and comparative aspects

In this article, an attempt is made to review the presently known, completely identified crustacean neuropeptides with regard to structure, function and distribution. Probably the most important progress has been made in the elucidation of a novel family of large peptides from the X-organ-sinus gland system which includes crustacean hyperglycemic hormone (CHH), putative molt-inhibiting hormone (MIH) and vitellogenesis (= gonad)-inhibiting hormone (VIH). These peptides have so far only been found in crustaceans. Renewed interest in the neurohemal pericardial organs has led to the identification of a number of cardioactive/myotropic neuropeptides, some of them unique to crustaceans. Important contributions have been made by immunocytochemical mapping of peptidergic neurons in the nervous system, which has provided evidence for a multiple role of several neuropeptides as neurohormones on the one hand and as local transmitters or modulators on the other. This has been corroborated by physiological studies. The long-known chromatophore-regulating hormones, red pigment concentrating hormone (RPCH) and pigment-dispending hormone (PDH), have been placed in a broader perspective by the demonstration of an additional role as local neuromodulators. The scope of crustacean neuropeptide research has thus been broadened considerably during the last years.

Changes in carbohydrate metabolism of Pila globosa in response to crustacean hyperglycemic hormone

Hyperglycemia was caused in the snail Pila globosa by the injection of the hyperglycemic hormones obtained from fresh water crabs (Oziotelphusa senex senex) and marine tiger prawns (Penaeus monodon). Tissue glycogen and total carbohydrates presented a significant decrease which indicated that the source of hyperglycemia was the tissue carbohydrates. The hyperglycemic principles also increased the tissue phosphorylase activity and provided evidence for a possible action of the crustacean hyperglycemic hormones in non-arthropod species.

Cloning and sequence analysis of cDNA encoding two crustacean hyperglycemic hormones from the lobster Homarus americanus

Using the polymerase chain reaction with degenerated oligonucleotides, we have isolated cDNA clones that encode two structurally different (92% identity) crustacean hyperglycemic hormones (CHH) from the lobster Homarus americanus. The deduced amino acid sequences fully agree with previously published data on partial amino acid sequences, amino acid compositions and molecular masses of hyperglycemic peptides in the lobster. A comparative analysis between the deduced primary structure of two lobster CHH and the crab CHH sequence reveals a phylogenetic relationship and allows the prediction of biologically important regions within the structures of these novel neuropeptides.

Isolation and amino acid sequence of crustacean hyperglycemic hormone precursor-related peptides

The crustacean hyperglycemic hormone (CHH) is synthesized as part of a larger preprohormone in which the sequence of CHH is N-terminally flanked by a peptide for which the name CPRP (CHH precursor-related peptide) is proposed. Both CHH and CPRP are present in the sinus gland, the neurohemal organ of neurosecretory cells located in the eyestalk of decapod crustaceans. This paper describes the isolation and sequence analysis of CPRPs isolated from sinus glands of the crab Carcinus maenas, the crayfish Orconectes limosus and the lobster Homarus americanus. The published sequence of "peptide H" isolated from the land crab, Cardisoma carnifex, has now been recognized as a CPRP in this species. Sequence comparison reveals a high level of identity for the N-terminal region (residues 1-13) between all four peptides, while identity in the C-terminal domain is high between lobster and crayfish CPRP on the one hand, and between both crab species on the other. Conserved N-terminal residues include a putative monobasic processing site at position 11, which suggests that CPRP may be a biosynthetic intermediate from which a potentially bioactive decapeptide can be derived.

Amino acid sequence of putative moult-inhibiting hormone from the crab Carcinus maenas

Putative moult-inhibiting hormone (MIH) was isolated from sinus glands of the shore crab Carcinus maenas, and its primary structure determined by automated Edman degradation of endoproteinase derived peptide fragments. MIH is a 78 residue neuropeptide (deduced molecular mass 9181 Da) with three disulphide bridges and unblocked N- and C-termini. MIH shows some homology to the crustacean hyperglycemic hormone (CHH) neuropeptide family. However, consideration of the roles of various members of this group, together with sequence information recently reported, strongly suggests that these neuropeptides may be multifunctional.

Autoradiographic evidence that transport of newly synthesized neuropeptides is directed to release sites in the X-organ--sinus gland of Cardisoma carnifex

Sections of isolated X-organ--sinus gland neurosecretory systems of the crab, Cardisoma carnifex, were studied by light- and electron microscopy with conventional and autoradiographic procedures. The somata only were exposed to a pulse of 3H-leucine (5 min-5 h) and the entire system perfused with chase medium for various times (1-72 h) before fixation. Within 1 h, radiolabel is concentrated in Golgi complexes and nascent granules of both large and small somata. Label is undetectable in the terminal region following a 10 h chase. It is found in the nerve tract near terminals at 14 h, while after a 19 h chase, label is concentrated in terminal profiles abutting blood sinuses of the neurohemal organ (sinus gland). Following a 72 h chase, label is distributed throughout the terminal region. Each of the six morphologically distinguishable terminal types shows labelling. These observations show that the vast majority of newly formed granules are initially transported to release sites of the perisinus terminals. They thus provide an explanation for previous analyses indicating that newly synthesized peptides are preferentially secreted.

Detection of mRNA encoding crustacean hyperglycemic hormone (CHH) in the eyestalk of the crayfish Orconectes limosus using non-radioactive in situ hybridization

A non-radioactive in situ hybridization procedure for the localization of the mRNA encoding the crustacean hyperglycemic hormone (CHH) in the eyestalk of the crayfish Orconectes limosus has been developed. Based on the partial amino acid sequence of CHH, polymerase chain reactions were performed to generate complementary DNA (cDNA) clones encoding CHH. Non-radioactively labelled probes derived from the cDNA sequence were used to establish suitable conditions in terms of tissue fixation and pretreatment for detection of the CHH-encoding mRNA in combination with an immunocytochemical staining using a polyclonal antibody for CHH. Localization of the mRNA in the CHH perikarya was obtained with a complementary RNA probe in combination with pepsin/HCl treated Bouin-fixed eyestalks. The immunocytochemical staining confirmed that this cRNA probe specifically hybridized with mRNA of cell somata belonging to the CHH-producing cell system in the eyestalk of Orconectes limosus.

Comparative characterization of hyperglycemic neuropeptides from the lobster Homarus americanus

With the use of a two-step HPLC purification procedure, two sets of two isoforms of the crustacean hyperglycemic hormone (CHH) were isolated from sinus glands of the lobster Homarus americanus. Structural differences between the two groups of isoforms were found in their amino acid sequences, amino acid compositions and precise molecular weights. Using peptide mapping, the difference between the isoforms in each group was located within the first eight amino acids at the N-termini. The nature of this difference remained unclear as all four peptides had the same N-terminal amino acid sequence unto residue 19.

Amino acid sequence of a peptide with both molt-inhibiting and hyperglycemic activities in the lobster, Homarus americanus

A hydrophobic peptide of 71 residues was isolated from lobster sinus gland extracts that prolonged intermolt periods and lowered ecdysteroid titers in juvenile lobsters. Removal of the N-terminal pyroglutamyl residue allowed sequencing of 30 of the first 36 residues. Additional data were obtained from HPLC-purified fragments from endoproteinase cleavages (Lys-C, Glu-C, Arg-C, Asp-N), and carboxypeptidase Y digestion. This is the first reported amino acid sequence of a crustacean molt-inhibiting hormone. This peptide also has significant hyperglycemic activity.