Analyzing the radiation of the proenkephalin gene in tetrapods: cloning of a Bombina orientalis proenkephalin cDNA

Analyzing the Radiation of the Proenkephalin Gene in Tetrapods: Cloning of a Bombina orientalis Proenkephalin cDNA: A proenkephalin cDNA was cloned from the brain of the anuran amphibian, Bombina orientalis (Family: Discoglossidae). This cDNA is 1358 nucleotides in length, and contains an open reading frame that codes for 251 amino acids. Within the open reading frame there are seven opioid (YGGF) sequences. There were five Met-enkephalin (YGGFM) sequences that are flanked by sets of paired basic amino acid proteolytic cleavage sites and two C-terminally extended Met-enkephalin sequences: YGGFMRGY and YGGFMRF. No Leu-enkephalin sequences were found in B. orientalis proenkephalin. It was possible to align the amino acid sequences of proenkephalin from several vertebrate taxa (human, Australian lungfish, B. orientalis, Xenopus laevis, Spea multiplicatus) by inserting a minimum of nine gaps. This alignment was then used to analyze the corresponding nucleotides for each proenkephalin sequence using maximum likelihood. This analysis yielded a single tree. In this tree, the Australian lungfish sequence was the outgroup or the tetrapod ingroup. The amphibian sequences form a clade separate from the human sequence. The bootstrap value for the amphibian clade was 100%. Within the amphibian clade the Bombina sequence was the sister group to a clade composed of the X. laevis and S. multiplicatus sequences. The bootstrap value for the X. laevis/S. multiplicatus clade was 94%. Collectively, these data indicate that the sequence of Bombina proenkephalin may be more similar to the proposed ancestral anuran proenkephalin sequence, than either X. laevis or S. multiplicatus proenkephalin.

Sturgeon orphanin, a molecular "fossil" that bridges the gap between the opioids and orphanin FQ/nociceptin

The elucidation of the cDNA sequence for sturgeon proorphanin provides a unique window for interpreting the evolutionary history of the opioid/orphanin gene family. The molecular "fossil" status of this precursor can be seen in several ancestral sequence characteristics that point to its origin as a duplication of either a prodynorphin- or proenkephalin-like gene. The sturgeon proorphanin cDNA encodes a precursor protein of 194 residues, and the orphanin heptadecapeptide itself binds not only the opioid receptor-like 1 (ORL1) receptor but also the classical (mu, kappa, and delta) opioid receptors with near equal affinity. Allowing for this broad receptor specificity are several amino acid substitutions at key positions in the heptadecapeptide sequence, relative to its mammalian orthologs, that have been linked by amino acid scans and site-directed mutagenic studies to the exclusion of mammalian orphanin FQ/nociceptin from classic opioid ligands (i.e. F1Y and L14W). The unique receptor binding profile of sturgeon orphanin not only provides insight into the evolutionary history of the opioid and opioid-related peptides but also provides an ideal context in which to investigate the underlying mechanisms by which novel and often divergent physiological functions arise in receptor-ligand systems.

In the african lungfish Met-enkephalin and leu-enkephalin are derived from separate genes: cloning of a proenkephalin cDNA

A full-length proenkephalin cDNA (accession number: AF232670) was cloned from an African lungfish (Protopterus annectens) brain cDNA library. The 1,351-bp African lungfish proenkephalin contains an open reading frame that codes 266 amino acids and a stop codon. Within the sequence of lungfish proenkephalin there are 5 pentapeptide opioid sequences (all YGGFM), 1 octapeptide opioid sequence (YGGFMRSL) and 1 heptapeptide opioid sequence (YGGFMGY). A Leu-enkephalin sequence was conspicuously absent in lungfish proenkephalin. These results, coupled with observations on the organization of amphibian proenkephalin and mammalian proenkephalin, indicate that among the Sarcopterygii (lobed finned fish and tetrapods), the appearance of a Leu-enkephalin sequence in proenkephalin may have evolved in either the ancestral amniotes or the ancestral mammals, but not earlier in sarcopterygian evolution. Furthermore, the detection of neurons in the lungfish CNS that are only immunopositive for Met-enkephalin, coupled with earlier anatomical studies on the presence of neurons in the lungfish CNS that are only immunopositive for Leu-enkephalin, indicates that a Leu-enkephalin-coding opioid gene must be present in the CNS of the lungfish. This gene may be the lungfish form of prodynorphin. Given the phylogenetic position of the lungfish in vertebrate evolution, the putative Leu-enkephalin-coding gene must have evolved in the ancestral sarcopterygian vertebrates, or in the ancestral gnathostomes. The apparent slow rate of lungfish evolution makes these organisms interesting models for investigating the evolution of the opioid/orphanin gene family.

Elevation of plasma cortisol during the spawning migration of landlocked kokanee salmon (Oncorhynchus nerka kennerlyi)

Kokanee salmon (Oncorhynchus nerka kennerlyi ), a landlocked subspecies of sockeye salmon, exhibited hypothalamic-pituitary interrenal (HPI, adrenal homologue) axis activation and an increase in plasma cortisol concentration up to 639 +/- 55.9 ng/ml in association with upstream migration in the upper Colorado River even though they were not exposed to a change in salinity and lengthy migration. Kokanee salmon were collected at various stages of migration and concomitant sexual maturation. The pattern of cortisol elevation in kokanee is similar to that in ocean-run sockeye salmon (O. nerka nerka). The presence of plasma cortisol elevation in an upstream migrating, landlocked Pacific salmon suggests that stressors previously considered to cause the cortisol increase, such as long-distance migration and changes in salinity, may not be primary causes of the HPI axis activation.

Deciphering the origin of Met-enkephalin and Leu-enkephalin in Lobe-finned fish: cloning of australian lungfish proenkephalin

The previous detection of Met-enkephalin and Leu-enkephalin in the CNS of the Australian lungfish, Neoceratodus forsteri, in a molar ratio comparable to mammals suggested that the lungfish proenkephalin precursor should contain the sequences of both Met-enkephalin and Leu-enkephalin as seen for mammalian proenkephalin. However, the cloning of a full-length proenkephalin cDNA from the CNS of the Australian lungfish indicates that the organization of this precursor is more similar to amphibian proenkephalin than mammalian proenkephalin. The Australian lungfish cDNA is 1284 nucleotides in length and the open reading frame (267 amino acids) contains seven opioid sequences (GenBank #AF232671). There are five copies of the Met-enkephalin sequence flanked by sets of paired basic amino acid proteolytic cleavage sites and two C-terminally extended forms of Met-enkephalin: YGGFMRSL and YGGFMGY. As seen for amphibians, no Leu-enkephalin sequence was detected in the Australian lungfish proenkephalin cDNA. The fact that Leu-enkephalin has been identified by radioimmunoassay and HPLC analysis in the CNS of the Australian lungfish indicates that a Leu-enkephalin-coding gene, distinct from proenkephalin, must be expressed in lungfish. Potential candidates may include a prodynorphin- or other opioid-like gene. Furthermore, the absence of a Leu-enkephalin sequence in lungfish and amphibian proenkephalin would suggest that the mutations that yielded this opioid sequence in tetrapod proenkephalin occurred at some point in the radiation of the amniote vertebrates.

Organization of proenkephalin in amphibians: cloning of a proenkephalin cDNA from the brain of the anuran amphibian, Spea multiplicatus

Cloning of a proenkephalin cDNA from the pelobatid anuran amphibian, Spea multiplicatus, provides additional evidence that Leu-enkephalin, although present in the brain of anuran amphibians, is not encoded by the proenkephalin gene. The S. multiplicatus proenkephalin cDNA is 1375 nucleotides in length, and the open reading frame contains the sequences of seven opioid sequences. There are five copies of the Met-enkephalin sequence, as well as an octapeptide opioid sequence (YGGFMRNY) and a heptapeptide opioid sequence (YGGFMRF). In the proenkephalin sequence of S. multiplicatus the penultimate opioid is a Met-enkephalin sequence rather than the Leu-enkephalin present in mammalian sequences. The same order of opioid sequences also is observed for the proenkephalin sequence of the pipid anuran amphibian, Xenopus laevis. Hence, from a phylogenetic standpoint the organization of tetrapod proenkephalin has been remarkably conserved. What remains to be resolved is whether the Leu-enkephalin sequence found in mammalian proenkephalin is an ancestral trait or a derived trait for the tetrapods. Unlike the proenkephalin precursor of X. laevis, all of the opioid sequences in the S. multiplicatus proenkephalin cDNA are flanked by paired-basic amino acid proteolytic cleavage sites. In this regard the proenkephalin sequence for S. multiplicatus is more similar to mammalian proenkephalins than the proenkephalin sequence of X. laevis. However, a comparison of the proenkephalin sequences in human, X. laevis, and S. multiplicatus revealed several conserved features in the evolution of the tetrapod proenkephalin gene. By contrast, a comparison of tetrapod proenkephalin sequences with the partial sequence of a sturgeon proenkephalin cDNA indicates that the position occupied by the penultimate opioid sequence in vertebrate proenkephalins may be a highly variable locus in this gene.

Cloning of a neoteleost (Oreochromis mossambicus) pro-opiomelanocortin (POMC) cDNA reveals a deletion of the gamma-melanotropin region and most of the joining peptide region: implications for POMC processing

A signature feature of tetrapod pro-opiomelanocortin (POMC) is the presence of three melantropin (MSH) coding regions (alpha-MSH, beta-MSH, gamma-MSH). The MSH duplication events occurred early during the radiation of the jawed vertebrates well over 400 million years ago. However, in at least one order of modern bony fish (subdivision Teleostei; order Salmoniformes; i.e. salmon and trout) the gamma-MSH sequence has been deleted from POMC. To determine whether the gamma-MSH deletion has occurred in other teleost orders, a POMC cDNA was cloned from the pituitary of the neoteleost Oreochromis mossambicus (order Perciformes). In O. mossambicus POMC, the deletion is more extensive and includes the gamma-MSH sequence and most of the joining peptide region. Because the salmoniform and perciform teleosts do not share a direct common ancestor, the gamma-MSH deletion event must have occurred early in the evolution of the neoteleost fishes. The post-translational processing of O. mossambicus POMC occurs despite the fact that the proteolytic recognition sequence, (R/K)-Xn-(R/K) where n can be 0, 2, 4, or 6, a common feature in mammalian neuropeptide and polypeptide hormone precursors, is not present at several cleavage sites in O. mossambicus POMC. These observations would indicate that either the prohormone convertases in teleost fish use distinct recognition sequences or vertebrate prohormone convertases are capable of recognizing a greater number of primary sequence motifs around proteolytic cleavage sites.

Cloning of a proopiomelanocortin cDNA from the pituitary of the Australian lungfish, Neoceratodus forsteri: analyzing trends in the organization of this prohormone precursor

The polypeptide hormone precursor, proopiomelanocortin (POMC), was cloned and sequenced from the pituitary of the Australian lungfish, Neoceratodus forsteri, the only surviving species of the oldest extant lineage of lungfish. The Australian lungfish POMC cDNA had an open reading frame that coded for a 255-amino acid precursor. A comparison of POMC sequences from the Australian lungfish and the African lungfish indicated that the deduced amino acid sequences for ACTH, beta-MSH, and beta-endorphin were over 90% identical. Furthermore, within the open reading frames of the two lungfish POMCs, there was 84% identity at the nucleotide level. Although a gamma-MSH-like region was detected in the Australian lungfish POMC cDNA, this sequence contained mutations that have been detected in the gamma-MSH sequences of some ray-finned fish and are not found in the gamma-MSH sequence of the African lungfish or those of tetrapods. In addition, the sequence of beta-endorphin in the two species of lungfish has amino acid motifs that are found in the beta-endorphin sequences of cartilaginous fish and ray-finned fish but not in tetrapods. However, maximum parsimony analysis of the entire POMC open reading indicated that the lungfish POMC sequences form a clade with two amphibian POMC sequences rather than with POMC sequences from ray-finned fish. This result is consistent with the accepted view that the sarcopterygians (lungfishes and tetrapods) are a monophyletic assemblage. Analysis of rates of divergence for various POMC sequences indicate that point mutations are accumulating in the lungfish POMC sequences at a slower rate than in either amphibian or mammalian POMC sequences. The phylogenetic implications of these observations are discussed.

Duplication of the POMC gene in the paddlefish (Polyodon spathula): analysis of gamma-MSH, ACTH, and beta-endorphin regions of ray-finned fish POMC

The proopiomelanocortin (POMC) gene, which encodes the common precursor for MSH-related and beta-endorphin-related end products, appeared early in chordate evolution and features a variety of lineage-specific modifications. Key among these has been the apparent degeneration and subsequent deletion of the gamma-MSH region during the evolution of POMC in the ray-finned fish. A second area of increasing focus has been the role of gene duplication in the evolution of POMC in particular and the opioid/orphanin gene family in general. The cloning and phylogenetic analysis of two POMC cDNAs from the paddlefish (Polyodon spathula) is reported here and biochemical data on their processed end products are presented. Based on conceptual amino acid translations, the paddlefish cDNAs encode all functional domains and, in most cases, the flanking paired-basic amino acid cleavage sites characteristic of gnathostome POMCs (i.e., signal sequence, gamma-MSH-like region, ACTH (alpha-MSH and CLIP), gamma-LPH, beta-MSH, and beta-endorphin). Phylogenetic analysis of the paddlefish POMC sequences in the context of the duplicated POMCs of sturgeon and salmonids suggests that degeneration of the gamma-MSH core sequence and its amino-terminal proteolytic cleavage site was initiated prior to divergence of the sturgeon and paddlefish lineages over 150 mya. Finally, a comparison of the relative rates of evolutionary divergence between paralogously related POMC genes within chondrostean and salmonid lineages provides potential support for the hypothesis that some taxa (e.g., the Chondrosteii) represent relic species as a result of an exceptionally slow rate of evolutionary change.

Cloning of proopiomelanocortin from the brain of the african lungfish, Protopterus annectens, and the brain of the western spadefoot toad, Spea multiplicatus

A degenerate primer, specific for the opioid core sequence YGGFM, was used to clone and sequence proopiomelanocortin (POMC) cDNAs from the brain of the African lungfish, Protopterus annectens, and from the brain of the western spadefoot toad, Spea multiplicatus. In addition, the opioid-specific primer was used to clone and sequence a 3'RACE product corresponding to a portion of the open reading frame of S. multiplicatus proenkephalin. For both species, cDNA was made from a single brain and a degenerate opioid-specific primer provided a reliable probe for detecting opioid-related cDNAs. The African lungfish POMC cDNA was 1,168 nucleotides in length, and contained regions that are similar to tetrapod POMCs and fish POMCs. The African lungfish POMC encodes a tetrapod-like gamma-MSH sequence that is flanked by sets of paired basic amino acid proteolytic cleavage sites. The gamma-MSH region in ray-finned fish POMCs either has degenerate cleavage sites or is totally absent in some species. However, the African lungfish gamma-MSH sequence does contain a deletion which has not been observed in tetrapod gamma-MSH sequences. The beta-endorphin region of lungfish POMC has the di-amino acid sequence tryptophan-aspartic acid in the N-terminal region and an additional glutamic acid residue in the C-terminal region of beta-endorphin - features found in fish beta-endorphin, but not tetrapod beta-endorphins. The western spadefoot toad POMC was 1,186 nucleotides in length, and exhibited an organizational scheme typical for tetrapod POMCs. However, the toad POMC did lack a paired basic amino acid proteolytic cleavage site N-terminal to the beta-MSH sequence. Thus, like rat POMC, it is doubtful that beta-MSH is an end product in either the toad brain or intermediate pituitary. At the amino acid level, the toad POMC had 76% sequence identity with Xenopus laevis POMC and 68% sequence identity with Rana ribidunda POMC. The use of these POMC sequences to assess phylogenetic relationships within anuran amphibians will be discussed. With respect to the fragment of S. multiplicatus proenkephalin cDNA, two metenkephalin sequences and the metenkephalin-RF sequence were found encoded in this fragment. As seen for X. laevis and R. ridibunda proenkephalin, a leuenkephalin sequence was not detected in the C-terminal region of the S. multiplicatus proenkephalin. The absence of a leuenkephalin sequence may be a common feature of anuran amphibian proenkephalins.

Molecular evolution of the opioid/orphanin gene family

Gene duplication is a recurring theme in the evolution of vertebrate polypeptide hormones and neuropeptides. These duplication events can lead to the formation of gene families in which divergence of function is the usual outcome. In the case of the opioid/orphanin family of genes, duplication events have proceeded along two paths: (a) an apparent duplication of function as seen in the analgesic activity of Proenkephalin and Prodynorphin end-products; and (b) divergence of function as seen in the nociceptic activity of Proorphanin end-products or the melanocortin (color change and chronic stress regulation) activity of Proopiomelanocortin end-products. Although genes coding for Proopiomelanocortin, Proenkephalin, Prodynorphin, and Proorphanin have been extensively studied in mammals, the distribution and radiation of these genes in nonmammalian vertebrates is less well understood. This review will present the hypothesis that the radiation of the opioid/orphanin gene family is the result of the duplication and divergence of the Proenkephalin gene during the radiation of the chordates. To evaluate the Proenkephalin gene duplication hypothesis, a 3'RACE procedure was used to screen for the presence of Prodynorphin-related, Proenkephalin-related, and Proorphanin-related cDNAs expressed in the brains of nonmammalian vertebrates.

Studies on the GH/SL gene family: cloning of African lungfish (Protopterus annectens) growth hormone and somatolactin and toad (Bufo marinus) growth hormone

The lungfishes (lobe-finned fish) occupy a unique position in vertebrate phylogeny, being regarded as the closest extant relatives to the tetrapods. The putative pituitary hormone somatolactin (SL) has hitherto been found only in teleost fishes, and the presence of this protein in tetrapods or lobe-finned fishes has not been ascertained. It was therefore of interest to determine the structure of SL in the African lungfish (Protopterus annectens), as this information would be useful for designing probes to facilitate the detection of SL genes in amphibians and other tetrapods. The structural relationships between SL, growth hormone (GH), and prolactin (PRL) strongly suggest that these proteins evolved from a common ancestor. To obtain a more complete picture of the evolution of these hormones in lungfish, African lungfish GH has been cloned and sequenced. The cDNA sequence of a toad (Bufo marinus) GH was determined to facilitate maximum parsimony analysis of GH sequences. Cladistic analysis confirmed that lungfish and amphibian GH sequences form a clade distinct from the GH sequences of ray-finned fishes. A distance matrix analysis of SL sequences indicated that lungfish SL had the lowest primary sequence identity with goldfish SL (47%) and the highest with flounder SL (66%). The detection of SL in a lungfish indicates that the gene duplication within the SL/GH/PRL family, which gave rise to SL, must have occurred in a common ancestor of the ray-finned fishes (Actinopterygii) and the lungfishes (Sarcopterygii) and tetrapods.

Cloning of a second proopiomelanocortin cDNA from the pituitary of the sturgeon, Acipenser transmontanus

A recent study on the pituitary of the sturgeon, Acipenser transmontanus, resulted in the cloning of a cDNA that codes for the prohormone, proopiomelanocortin (POMC). This cDNA is designated sturgeon POMC A. Subsequent analysis of the sturgeon pituitary uncovered a second distinct POMC cDNA (sturgeon POMC B). In both sturgeon POMC cDNAs the open reading frame is 795 nucleotides in length. However, the two sturgeon POMC cDNAs differ at 26 amino acid positions in the opening frame. In addition, the 2 forms of POMC differ at 45 nucleotide positions within the open reading frame. The number and types of point mutations are compared in the 2 sturgeons POMC cDNAs, and the origin of the two POMC genes is discussed.

Impaired adrenocortical response to stress by brown trout, Salmo trutta, living in metal-contaminated waters of the Eagle River, Colorado

Brown trout, Salmo trutta, were collected from two sites contaminated with cadmium (Cd) and zinc (Zn) and one uncontaminated site. These fish were subjected to a continuous confinement stressor in wire cages placed in the river (moderate stress) or in 5-gal. plastic buckets on land (severe stress). Plasma cortisol and corticotropin (ACTH) were determined for fish in buckets by radioimmunoassay after 0, 1, 3, 12, or 24 h of confinement. Plasma cortisol and ACTH levels of brown trout from both contaminated and uncontaminated sites initially were the same and increased with time. However, the rise in plasma cortisol was delayed significantly in fish residing in contaminated sites, even though ACTH secretion initially was elevated compared with control trout. Furthermore, secretion of cortisol and ACTH by these fish declined significantly between 3 and 24 h of confinement. Fish from the uncontaminated site responded more rapidly to confinement with increased cortisol secretion and elevated levels of ACTH and continued to exhibit elevated levels of both hormones up to 24 h of confinement. Caged fish examined after 0, 3, 12, and 24 h of confinement exhibited similar plasma cortisol responses regardless of previous exposure to metals. These results suggest that the overall response to severe, short-term confinement stress by the hypothalamo-pituitary-adrenocortical axis of fish chronically exposed to Cd and Zn was depressed and that these fish could not sustain the stress response as readily as fish living in uncontaminated water.

Immunocytochemical and histological differences in the interrenal axis of feral brown trout, Salmo trutta, in metal-contaminated waters

There are more CRH-like immunoreactive neurons in the preoptic nucleus and nucleus lateralis tuberis in the brain of feral brown trout, Salmo trutta, living in cadmium- and zinc-contaminated regions of the Eagle River than in fish from an uncontaminated control site. Histological analyses revealed that interrenal cells are more stimulated (exhibiting both hypertrophy and hyperplasia) in fish living in contaminated sites than interrenal cells of fish at the control site. These results suggest that the hypothalamo-pituitary-interrenal (HPI) axis of fish living in the metal-contaminated water shows evidence of chronic stimulation. We suggest that assessment of these parameters of the HPI axis may be useful indices of chronic environmental stress in trout.

Deciphering posttranslational processing events in the pituitary of a neopterygian fish: cloning of a gar proopiomelanocortin cDNA

A cDNA that codes for the polypeptide hormone precursor proopiomelanocortin (POMC) was cloned and sequenced from a gar (Lepisosteus osseus) pituitary cDNA library. The gar POMC cDNA is 1237 bp and contains a 780-bp open reading frame. The deduced amino acid sequence for gar POMC is 259 amino acids in length. The general organization of gar POMC is very similar to that of other gnathostome POMC sequences. The beta-endorphin sequence had 91% sequence identity with sockeye A beta-endorphin and 71% sequence identity with Xenopus laevis beta-endorphin. Three melanocyte-stimulating hormone (MSH) core sequences [HFR(W)] were detected. The gar alpha-MSH sequence was identical to the alpha-MSH sequence in rat POMC. The gar beta-MSH sequence had 77% sequence identity with salmonid forms of beta-MSH and 53% sequence identity with tetrapod forms of beta-MSH. The gamma-MSH region of gar POMC only had 26% primary sequence identity with tetrapod gamma-MSH sequences. Gar gamma-MSH had an incomplete MSH core sequence (HRF), an apparent internal deletion of five amino acids, and lacked flanking paired basic amino acids essential for proteolytic cleavage. The apparent degenerate nature of gar gamma-MSH is discussed in light of the absence of this sequence in salmonid fish.

Sturgeon proopiomelanocortin has a remnant of gamma-melanotropin

For the investigation of the evolution of the proopiomelanocortin (POMC) gene in early ray-finned fishes, nucleotide sequence of POMC cDNA from a chondrostean fish, the sturgeon has been determined. POMC cDNA was amplified by PCR from double-strand cDNA prepared from sturgeon pituitary and ligated with lambdaZAP II. The POMC cDNA consists of 1079 bp without a poly-A. An open reading frame of the POMC cDNA encodes 263 amino acid residues. Sturgeon POMC contains ACTH, alpha-melanotropin (MSH), beta-MSH and beta-END at positions (115-153), (115-127), (186-202) and (205-238), respectively. Location of POMC(51-72) is homologous to gamma-MSH, whereas the third residue of MSH-core sequence, His-Phe-Arg-Trp, is changed to His. Moreover, there are no basic amino acids to serve as a processing signal on the N-terminal side of POMC(51-72). These structural characteristics suggest that an ancestor of the ray-finned fishes had gamma-MSH, whereas significant mutations occurred during the evolution of chondrostean fish.

Is it possible to construct phylogenetic trees using polypeptide hormone sequences?

Because of the high degree of primary sequence conservation in neuropeptides and low molecular weight polypeptide hormones, these polypeptides are not useful for constructing phylogenetic trees based on maximum parsimony analysis. This review focuses on the organization of neuropeptide and polypeptide hormone precursors and discusses strategies for aligning polypeptide precursors for phylogenetic analysis. Examples are provided to support the hypothesis that some neuropeptide and polypeptide precursors and some high molecular weight polypeptide hormones can be used as data sets for resolving deep divergences among vertebrate taxa.

A comparative analysis of somatolactin-related immunoreactivity in the pituitaries of four neopterygian fishes and one chondrostean fish: an immunohistochemical study

An antiserum to cod somatolactin (SL) was used for immunohistochemical screening for the pars intermedia of two teleosts (Oreochromis mossambicus and Gymothorax meleagris), two holostean fishes (Lepisosteus osseus and Amia calva), and a chondrostean fish (Acipenser fulvescens) for SL-immunopositive (SL-IR) cells. As expected, a subset of the epithelial cells in the pars intermedia of O. mossambicus (tilapia) was immunopositive for SL, and the remainder of the epithelial cells was immunopositive for alpha-MSH-specific antiserum (alpha-MSH-IR). SL-IR was not detected in any of the epithelial cells in the pars intermedia of the moray eel G. meleagris. To determine whether SL-IR could be detected in nonteleost fishes, immunohistochemical analyses were done on the pituitaries of two holostean fishes and one chondrostean fish. In the pars intermedia of the gar, L. osseus, a subset of cells was immunopositive for alpha-MSH only. However, in the pars intermedia of the bowfin, A. calva, all of the epithelial cells indicated the presence of both SL and alpha-MSH. Finally, no SL-positive cells were detected in the pars intermedia of the sturgeon, A. fulvescens.

Cloning of a gar (Lepisosteus osseus) GH cDNA: trends in actinopterygian GH structure

A cDNA containing the sequence of GH was cloned and sequenced from a pituitary cDNA library for the holostean fish Lepisosteus osseus (common name: gar). The gar GH cDNA contained an open reading frame of 633 nucleotides and a 3' untranslated region (including the terminal codon TAG) of 1058 nucleotides. The overall length of the gar GH cDNA including leader sequence, signal sequence, hormone sequence and 3' untranslated region was 1713 nucleotides. Thus, the gar GH cDNA is the largest vertebrate GH cDNA yet cloned. A comparison of GH sequences from ancient (holostean fishes-gar and bowfin; one chondrostean fish-the Russian sturgeon) and more modern (27 species of teleosts) members of class Actinopterygii indicate that members of this class have maintained many of the invariant residues deemed necessary for GH folding motifs (intramolecular relationships) observed in mammals.

POMC-related products in the intermediate pituitary of the amphibian, Bufo marinus: differential subcellular processing in the Golgi and secretory granules

In the intermediate pituitary of the anuran amphibian, Bufo marinus, the N-acetylation of ACTH(1-13)-NH2 to yield alpha-MSH occurs as a cosecretory processing event, whereas the N-acetylation of beta-endorphin occurs as a posttranslational processing event. To understand how these two N-acetylation reactions are segregated, B. marinus intermediate pituitary cells were analyzed by immunogold labeling electron microscopy, and by using an ultracentrifugation procedure. The immunogold labeling studies indicated that ACTH(1-13)-NH2-related immunoreactivity was colocalized with N-acetylated beta-endorphin-related immunoreactivity in secretory granules. Furthermore, ACTH(1-13)-NH2-related immunoreactivity was not detected in either the ER or the Golgi. N-Acetylated beta-endorphin-related immunoreactivity, however, was detected in the Golgi. Ultracentrifugation analysis revealed that in an ER/microsomal fraction, beta-LPH-sized and nonacetylated beta-endorphin-sized immunoreactive material were present in a molar ratio of 1:2. No N-acetylated forms of beta-endorphin were detected in the ER/microsomal fraction. In a Golgi/secretory granule fraction, the molar ratio of beta-LPH to beta-endorphin was 1:9 with 58% of the beta-endorphin being N-acetylated. Collectively, these data support the following hypotheses. The proteolytic cleavage of ACTH (1-39) to yield ACTH (1-13)-NH2 is a late processing event occurring in secretory granules. The cleavage of beta-LPH to yield nonacetylated beta-endorphin is an early processing event that may occur in the ER or the Golgi. Because N-acetylated beta-endorphin and nonacetylated ACTH(1-13)-NH2 are colocalized in secretory granules, it appears, therefore, that the N-acetylation of beta-endorphin is completed prior to loading into secretory granules. Thus, there is a spatial and temporal separation of the posttranslational processing events associated with the beta-LPH portion and ACTH portion of the POMC biosynthetic pathway in amphibian intermediate pituitary cells.

Obtaining a more resolute teleost growth hormone phylogeny by the introduction of gaps in sequence alignment

In order to obtain a more resolute phylogeny of teleosts based on growth hormone (GH) sequences, phylogenetic analyses were performed in which deletions (gaps), which appear to be order specific, were upheld to maintain GH's structural information. Sequences were analyzed at 194 amino acid positions. In addition, the two closest genealogically related groups to the teleosts, Amia calva and Acipenser guldenstadti, were used as outgroups. Modified sequence alignments were also analyzed to determine clade stability. Analyses indicated, in the most parsimonious cladogram, that molecular and morphological relationships for the orders of fishes are congruent. With GH molecular sequence data it was possible to resolve all clades at the familial level. Analyses of the primary sequence data indicate that: (a) the halecomorphean and chondrostean GH sequences are the appropriate outgroups for generating the most parsimonious cladogram for teleosts; (b) proper alignment of teleost GH sequence by the inclusion of gaps is necessary for resolution of the Percomorpha; and (c) removal of sequence information by deleting improperly aligned sequence decreases the phylogenetic signal obtained.

Cloning of a growth hormone from a primitive bony fish and its phylogenetic relationships

Growth hormone (GH), prolactin, and their relatives constitute a multigene family which is considered to have evolved from a common ancestor. The structural and functional domains of GH appear to be highly conserved among vertebrates. In order to investigate the phylogenetic relationships among GHs in the Actinopterygii and Sarcopterygii, we have cloned and sequenced GH from the pituitary of the primitive bony fish, Amia calva. Bony fishes (teleosts) and Amia (Halecomorphi) are purported sister-groups within the Neoptergii, hence studies on this perspective group of fish can provide insights into the evolution of GH. The deduced amino acid (aa) sequence from A. calva GH (amGH) cDNA revealed that the mature GH consists of 190 residues. Phylogenetic comparisons with GH aa sequences from blue shark, sturgeon, four teleosts (eel, carp, porgy, flounder), and two sarcopterygians (African lungfish and bullfrog) indicated, in the most parsimonious cladogram, that amGH clusters as the sister-group to the teleosts, that sturgeon is the sister-group to the Neopterygii, and that the African lungfish and bullfrog are in the same clade.

Melanotropes of the lizard, Anolis carolinensis, lack N-acetylating mechanisms for both alpha-melanocyte-stimulating hormone and beta-endorphin

In order to determine whether Anolis carolinensis intermediate pituitary cells have the capacity to N-acetylate either ACTH(1-13)NH2 or beta-endorphin during secretion, individual intermediate pituitary explants were incubated in DMEM/CO2 for 24 h at 28 degrees C. Although alpha-melanocyte-stimulating hormone (alpha-MSH)- and beta-endorphin-related products were spontaneously released into the medium, none of these forms were N-acetylated. It appears that unlike most gnathostomes, A. carolinensis has secondarily lost the POMC-specific N-acetylation mechanisms. A ramification of this observation is that the alpha-MSH for A. carolinensis is ACTH(1-13)NH2.

Analysis of the post-translational processing of alpha-MSH in the pituitaries of the chondrostean fishes, Acipenser transmontanus and Polyodon spathula

Multiple forms of alpha-MSH were isolated from the pituitaries of the white sturgeon, Acipenser transmontanus, and the paddlefish, Polyodon spathula, following fractionation of the pituitary extracts by reversed-phase HPLC. In both species, immunoreactive forms which eluted with the same retention times as synthetic mammalian ACTH(1-13)NH2, monoacetylated alpha-MSH, and diacetylated alpha-MSH were detected. In the pituitary of the sturgeon, N-acetylated forms of alpha-MSH represented 91% of the total alpha-MSH isolated. However, in the pituitary of the paddlefish, N-acetylated forms of alpha-MSH accounted for only 45% of the total alpha-MSH isolated. The presence of N-acetylated forms of alpha-MSH in the pituitaries of representatives of the two extant genera of chondrostean fish coupled with the observation that N-acetylated forms of alpha-MSH are present in the pituitaries of cladistian and neopterygian fishes indicates that the alpha-MSH specific N-acetylation mechanism evolved prior to the radiation of the Actinopterygii. A conspicuous feature of the chondrostean alpha-MSH N-acetylation reaction was the low levels of diacetylated alpha-MSH produced relative to the levels of monoacetylated alpha-MSH. Similar observations have been made for the cladistian fish, Calamoichthys calabaricus, and the cartilaginous fish, Hydrolagus colliei. However, in holostean fishes, lungfishes, and tetrapods, the diacetylated form of alpha-MSH is the major end product produced in the intermediate pituitary. The phylogenetic implications of these observations will be discussed.

An analysis of the proopiomelanocortin systems in the pituitary of the squamate reptile Lacerta galloti

Acid extracts of the pars intermedia of the squamate reptile Lacerta galloti were screened for immunoreactive forms of proopiomelanocortin (POMC)-related end products following Sephadex G-50 column chromatography. alpha-MSH-sized end products were detected with a Val-NH2, C-terminal-specific RIA, and beta-endorphin-sized end products were detected with a separate C-terminal-directed RIA. Five peaks of alpha-MSH-related immunoreactivity were isolated following fractionation by reversed-phase HPLC. Based on a comparison of the reversed-phase HPLC properties and the net positive charges (pH 2.75) of the Lacerta forms of alpha-MSH to those of the mammalian forms of alpha-MSH and Anolis carolinensis ACTH(1-13)NH2, it appears that the N-acetylation of alpha-MSH is a major post-translational processing event in the pars intermedia of L. galloti. Although multiple forms of beta-endorphin were detected in the pars intermedia of L. galloti following cation-exchange chromatography, the low levels of N-acetylated beta-endorphin detected with an N-acetyl-specific beta-endorphin RIA indicate that the N-acetylation of beta-endorphin in this species is a minor post-translational processing event. This pattern of POMC processing in the pars intermedia of L. galloti is similar to the processing events observed for the turtle Pseudemys scripta, but distinct from the processing events observed in the squamate reptile A. carolinensis.

The posttranslational modification of beta-endorphin in the intermediate pituitary of the toad, Bufo marinus, includes processing at a monobasic cleavage site

Fractionation of an acid extract of 15 B. marinus intermediate pituitaries by a combination of gel filtration chromatography and cation exchange chromatography revealed one major and five minor forms of beta-endorphin in this tissue. Based on reversed-phase HPLC and immunological properties, as well as amino acid composition and primary sequence analysis, it was deduced that the sequence of the major form of B. marinus beta-endorphin is N-acetyl-YGGFMTPE. Overall, the steady-state analyses of the minor forms of beta-endorphin indicated that the posttranslational processing of beta-endorphin in the toad intermediate pituitary includes endoproteolytic cleavage at both paired basic and monobasic cleavage sites.

Detection of N-acetylated forms of alpha-MSH and beta-endorphin in the intermediate pituitary of the holostean fishes, Lepisosteus spatula, Lepisosteus osseus, and Amia calva

Acid extracts of the intermediate pituitaries of the gars, L. spatula and L. osseus, were fractionated by Sephadex G-50 column chromatography and analyzed by radioimmunoassay. This procedure revealed that immunoreactive forms of N-acetylated beta-endorphin- and alpha-MSH-sized material were present in equimolar amounts and represented the major end products of the POMC biosynthetic pathway in these species. Cation-exchange chromatography indicated that multiple N-acetylated forms of beta-endorphin were present in the intermediate pituitaries of the two species of gar, and that these forms differed in their net positive charge and in their apparent molecular weight. Reversed-phase HPLC analysis of the alpha-MSH-related material indicated that up to 90% of the total MSH in the pituitary of the gar was N-acetylated. Furthermore, the predominant form of alpha-MSH in both species of gar was N,O-diacetyl-ACTH(1-13)-NH2. Nearly identical results were obtained following the analysis of alpha-MSH-related peptides in the intermediate pituitary of the bowfin, A. calva. The pattern of posttranslational processing of POMC observed in the intermediate pituitaries of holostean fishes is very similar to the processing events observed in lungfishes, turtles, and mammals; hence, the processing of POMC has been remarkably conserved during vertebrate evolution.

Proteolytic cleavage of ACTH in corticotropes of sexually mature axolotls (Ambystoma mexicanum)

Immunohistochemical analysis of the pituitary of sexually mature axolotls revealed both ACTH(1-39)-related and alpha-MSH-related immunoreactivity present in corticotropic cells located in the rostral anterior pituitary. Gel filtration analysis indicated that the ACTH(1-39)-sized immunoreactivity and the alpha-MSH-sized immunoreactivity detected in acid extracts of the axolotl anterior pituitary were present in a ratio in a range between 1:1 and 1:0.6. Reversed-phase HPLC analyses indicated that the alpha-MSH-sized immunoreactivity had the same retention time as synthetic ACTH(1-13)-NH2. The corticotropic activity of the ACTH(1-39)-sized immunoreactivity and the purified ACTH(1-13)-NH2 was tested in a heterologous, larval bullfrog adrenal bioassay system. As expected, the ACTH(1-39)-sized immunoreactivity stimulated corticosterone release; however, the purified ACTH(1-13)-NH2 lacked glucocorticoid activity. The proteolytic cleavage of ACTH in corticotropes of sexually mature axolotls was identical to the cleavage events observed in neotenic Ambystoma tigrinum that had not reached sexual maturity. These studies indicate that the transient expression of ACTH cleavage activity is not affected by the reproductive state of the animal. Since axolotls do not undergo metamorphosis, it is possible that events associated with metamorphosis may induce the decline in ACTH cleavage activity observed in amphibian corticotropes.

Differential N-acetylation of alpha-MSH and beta-endorphin in the intermediate pituitary of the turtle, Pseudemys scripta

Steady-state analyses of the intermediate pituitary of the turtle, Pseudemys scripta, indicated that alpha-MSH-sized immunoreactive forms and beta-endorphin-sized immunoreactive forms are major end products of melanotropic cells. Three forms of alpha-MSH-related immunoreactivity were detected. The two major forms had the same reversed-phase HPLC properties as synthetic N,O-diacetyl-ACTH(1-13)-NH2 and N-acetyl-ACTH(1-13)-NH2. These forms accounted for 97% of the total alpha-MSH-related immunoreactivity detected. A minor peak of ACTH(1-13)-NH2 was also detected. Multiple forms of beta-endorphin-related immunoreactivity were detected, which varied in net positive charge (+1 to +5), apparent molecular weight (2.4 to 3.5 kDa), and degree of N-terminal acetylation. Although N-acetylated forms of beta-endorphin were detected in the turtle intermediate pituitary, the major forms of turtle beta-endorphin were nonacetylated. These features of the turtle intermediate pituitary POMC-specific N-acetylation mechanism are similar to, yet distinct from, the POMC N-acetylation mechanisms observed for mammals. These data suggest that POMC-specific N-acetylation mechanisms were present in reptiles prior to the divergence of the anapsid and synapsid lines.

Isolation of prolactin and growth hormone from the pituitary of the holostean fish Amia calva

Pituitaries from adult male and female Amia calva (Order Holostei) were acid extracted and fractionated by gel filtration column chromatography and reversed-phase high performance liquid chromatography. This two-step isolation procedure yielded homogeneous pools of Amia prolaction (PRL) and growth hormone (GH). The amino acid composition of both purified polypeptides was determined. Primary sequence analysis of the first 22 positions at the N-terminal of Amia PRL revealed that this region has 63% sequence identity with eel PRL-1. The N-terminal region of Amia PRL lacks the disulfide bridge which is characteristic of tetrapod PRLs. Primary sequence analysis of the first 24 positions at the N-terminal of Amia GH revealed that this region has 62% sequence identity with eel GH and 54% sequence identity with both blue shark GH and sea turtle GH. Based on N-terminal analysis, it appears that Amia PRL and GH are more closely related to teleost PRLs and GHs than they are to tetrapod PRLs and GHs.

An anatomical and biochemical study of the pituitary proopiomelanocortin systems in the polypteriform fish Calamoichthys calabaricus

Immunohistochemical and biochemical analyses were performed on the pituitary Proopiomelanocortin (POMC) systems of the polypteriform fish Calamoichthys calabaricus. Immunohistochemical staining of the pituitary revealed a clustering of ACTH immunopositive cells within the rostral pars distalis. alpha-Melanocyte stimulating hormone (alpha-MSH)-related and beta-endorphin-related immunoreactivity were found colocalized in epithelial cells of the pars intermedia. Biochemical analyses included Sephadex G-50 column chromatography, reversed-phase HPLC, and cation exchange chromatography. These analyses revealed the presence of immunoreactive forms of ACTH which stimulated glucocorticoid release when tested on isolated Bufo marinus adrenocortical tissue. Three forms of alpha-MSH were detected, and the major form had the same HPLC chromatographic properties as synthetic monoacetylated alpha-MSH. Finally, five forms of beta-endorphin were detected, and all of these forms were N-acetylated. Based on these observations, it appears that N-acetylation is a major post-translational processing event within the melanotropic cells of C. calabaricus. Given the position of Order Cladistia in the phylogeny of actinopterygian fish, it appears that N-acetylation of POMC-related products is an ancestral trait of osteichthyean fish.

Catecholaminergic cells and fibers in the brain of the lizard Anolis carolinensis identified by traditional as well as whole-mount immunohistochemistry

Using traditional as well as whole-mount immunohistochemistry, we described the location of tyrosine hydroxylase- and dopamine beta hydroxylase-positive cells and fibers in the brain of the lizard Anolis carolinensis. Major catecholaminergic cell groups were in the ependyma in certain ventricular regions, along the periventricular floor in the preoptic region, within the anterior hypothalamic and lateral hypothalamic areas, and in the mesencephalic tegmental region, locus coeruleus, nucleus of the solitary tract, vagal motor nucleus, and rhombencephalic reticular formation. Major catecholaminergic fibers, tracts and varicosities included tuberohypophysial, mesolimbic, nigrostriatal, isthmocortical, medullohypothalamic, and coeruleospinal systems. Although the catecholaminergic systems in A. carolinensis are similar to those in the brains of other lizards studied, there are a few species differences. Our information about A. carolinensis will be used to help localize the hypothalamic asymmetry in catecholamine metabolism previously described in this lizard.

Reversed phase HPLC analysis of proenkephalin-related and prodynorphin-related end-products in the brain of a urodele amphibian, Ambystoma tigrinum

Acid extracts of the brain of a urodele amphibian, Ambystoma tigrinum, were screened with radioimmunoassays specific for enkephalin-related products and dynorphin-related products. Following Sephadex G-50 column chromatography a peak of enkephalin-sized immunoreactive material was detected near the total volume of the column. The enkephalin-sized immunoreactivity was further analyzed by reversed phase HPLC. This analysis detected peaks of authentic Met-enkephalin and Leu-enkephalin. However, the molar ratio of Met-enkephalin to Leu-enkephalin in the brain of this amphibian was approximately 80:1. These observations would suggest that the Leu-enkephalin detected in the brain of Ambystoma may be derived from a source other than the Proenkephalin precursor. Neither Met-enkephalin-RGL or Met-enkephalin-RF were detected by radioimmunoassay in brain extracts from this urodele. However, following digestion with trypsin and carboxypeptidase B, a novel peak of C-terminally extended Met-enkephalin was detected. Two peaks of Prodynorphin-related products were also detected following gel filtration chromatography. These immunoreactive forms were detected using antisera specific for alpha-neo-endorphin and dynorphin B(1-13). No immunoreactive forms with antigenic determinants similar to mammalian dynorphin A(1-17) or dynorphin A(1-8) were detected in this species. Reversed phase HPLC analysis indicated that the major form of urodele alpha-neo-endorphin eluted with the same retention time as synthetic mammalian alpha-neo-endorphin. Urodele dynorphin B(1-13)-related immunoreactivity eluted as a single peak, however, this form did not elute with the same retention time as synthetic mammalian dynorphin B(1-13).(ABSTRACT TRUNCATED AT 250 WORDS)

Arginine vasotocin concentrations in the supraoptic nucleus of the lizard Anolis carolinensis are associated with reproductive state but not oviposition

Arginine vasotocin (AVT) is a neuropeptide involved in reproductive function in many nonmammalian vertebrates. We determined brain and plasma AVT concentrations during the estrous cycle and oviposition in the lizard Anolis carolinensis. There were no differences in AVT concentrations in the plasma or any brain region during the ovipositional sequence. However, we found that females with an egg in each oviduct and a large pre-ovulatory follicle (diameter > 4.5 mm) in one-ovary had significantly higher AVT concentrations in the supraoptic nucleus (SON) of the hypothalamus than did females with small pre-ovulatory follicles in both ovaries. In a second study, females with an egg in each oviduct and a large pre-ovulatory follicle had significantly greater AVT concentrations in the SON than females with only one oviductal egg and a large pre-ovulatory follicle or females with an egg in each oviduct and a small pre-ovulatory follicle in each ovary. Concentrations of AVT in other brain regions and in the plasma did not differ among these groups. Changes in steroid profiles during estrous and/or direct neural communication between the uterus, ovary, and brain may account for the changes in AVT concentrations seen in the supraoptic nucleus during the estrous cycle of Anolis carolinensis.

Detection of Met-enkephalin in the pars intermedia of the lampreys, Ichthyomyzon castaneus and Petromyzon marinus

Acid extracts of the brain and pars intermedia of the chestnut lamprey, Ichthyomyzon castaneus, were fractionated by a combination of gel filtration chromatography and reversed-phase HPLC, and screened with RIAs specific for Met-enkephalin and Leu-enkephalin, respectively. In the brain extract, both Met-enkephalin and Leu-enkephalin were detected in a molar ratio of approximately 4:1. These results would suggest that these two enkephalins were derived from a lamprey Proenkephalin precursor. However, reversed-phase HPLC analysis of the pars intermedia of this species revealed the presence of Met-enkephalin, but not Leu-enkephalin. Analysis of the pars intermedia of the marine lamprey, Petromyzon marinus, also indicated the presence of Met-enkephalin but not Leu-enkephalin. These results would suggest that the Met-enkephalin present in the pars intermedia of lampreys may not be derived from Proenkephalin, but may originate from another opioid precursor. This possibility and alternative hypotheses to explain these observations are discussed.

Detection and partial characterization of proopiomelanocortin-related end-products from the pars intermedia of the toad, Bombina orientalis

Steady-state analyses were performed on the proopiomelanocortin (POMC)-related end-products present in acid extracts of the pars intermedia of the anuran amphibian, Bombina orientalis. Sephadex G-75 gel filtration chromatography indicated that immunoreactive alpha-MSH-sized material and N-acetylated beta-endorphin-related material are the major POMC-related products present in this tissue. The alpha-MSH-sized immunoreactivity was further fractionated by reversed phase HPLC. The major peak of immunoreactivity isolated by this procedure eluted with the same retention time as synthetic ACTH(1-13)amide. Cation exchange chromatography supported the conclusion that the major storage form of alpha-MSH in the pars intermedia of Bombina is ACTH(1-13)amide. Analysis of Bombina pars intermedia in culture indicated that mono-acetylated and di-acetylated alpha-MSH were the major forms of alpha-MSH secreted into the medium. The major peak of N-acetylated beta-endorphin-related material was further analyzed by cation exchange chromatography and Sephadex G-25 gel filtration column chromatography. The major storage form of beta-endorphin in this tissue is N-acetylated, has a net positive charge at pH 2.75 of +1, and has an apparent molecular weight of 1.2K. The beta-endorphin present in the pars intermedia of this tissue does not undergo further N-acetylation at the time of secretion. These results indicate that in the pars intermedia of the archaeobatrachian, Bombina orientalis, the N-acetylation of alpha-MSH is a cosecretory processing event, whereas N-acetylation of beta-endorphin is a post-translational processing event. These results are compared to other archaeobatrachian and neobatrachian pituitary POMC systems that have been analyzed.

Detection of prodynorphin end products in lizard, turtle, and alligator brain extracts

Heterologous radioimmunoassays (RIAs) for the mammalian prodynorphin end products, alpha-neo-endorphin, dynorphin A(1-17), dynorphin A(1-8), and dynorphin B(1-13) were used to screen brain extracts obtained from representatives of the major surviving orders of reptiles: Chelonia (Pseudemys scripta), Squamata (Anolis carolinensis), and Crocodylia (Alligator mississippiensis). Methanol/acid extracts of whole brains obtained from each species were separately fractionated by gel filtration chromatography and reversed-phase HPLC. In all three species, an immunoreactive form of alpha-neo-endorphin was detected with the same retention time as synthetic mammalian alpha-neo-endorphin following reversed-phase HPLC analysis. In all three species, reversed-phase HPLC analysis revealed a novel form of dynorphin B(1-13)-related immunoreactivity. With the available immunological probes, dynorphin A products were only detected in the Anolis brain extracts. Both dynorphin A(1-17) and dynorphin A(1-8) were detected in this species.

Detection of a novel sequence change in the major form of alpha-MSH isolated from the intermediate pituitary of the reptile, Anolis carolinensis

Intermediate pituitaries of the reptile, Anolis carolinensis, were separately pulse labeled with [3H]Trp and [3H]Tyr. The major form of alpha-MSH was purified by immunoprecipitation and isolated by reverse phase HPLC. Tryptic peptide analysis indicated that the [3H]Trp-labeled C-terminal fragment of Anolis alpha-MSH had the same retention time as mammalian ACTH(9-13) amide; however, the [3H]Tyr-labeled N-terminal fragment did not coelute with either mammalian ACTH(1-8) or N-acetyl-ACTH(1-8). Purification of alpha-MSH from 76 Anolis intermediate pituitaries confirmed that a sequence change had occurred in the N-terminal region of Anolis alpha-MSH. The tissues were acid extracted and purified by Sephadex G-25 chromatography and reverse phase HPLC to yield 4.5 micrograms of purified Anolis alpha-MSH for amino acid composition analysis and automated Edman degradation sequence analysis. The major form of Anolis alpha-MSH is nonacetylated and has the following novel primary sequence: Ser-Tyr-Ala-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro(Val-amide). The presence of Val-amide was verified by immunological analysis, tryptic peptide analysis and amino acid composition analysis.

The phylogeny of Met-enkephalin and Leu-enkephalin: studies on the holostean fish Lepisosteus platyrhincus and the Australian lungfish, Neoceratodus forsteri

Acid extracts of the brain of the holostean fish Lepisosteus platyrhincus and the forebrain of the dipnoan fish Neoceratodus forsteri were separately fractionated by Sephadex G-50 column chromatography. For both species, Met-enkephalin-related immunoreactivity was detected coeluting with the total volume internal standard. Higher-molecular-weight Met-enkephalin-containing immunoreactive peaks were not detected in these chromatographs. Furthermore, immunoreactive forms with antigenic determinants identical to mammalian dynorphin A(1-17), dynorphin A(1-8), alpha-neo-endorphin, or dynorphin B(1-13) were not detected in either species. Reverse-phase HPLC analysis of enkephalin-sized immunoreactive material indicated the presence of authentic Met-enkephalin and Leu-enkephalin in the extracts of both species. In the brain of L. platyrhincus the molar ratio of Met-enkephalin to Leu-enkephalin was approximately 3:1, whereas, the molar ratio of these enkephalins in the forebrain of N. forsteri was approximately 5:1 [corrected]. C-terminally extended forms of Met-enkephalin were also detected in the extracts of both species. These results suggest that the ancestral proenkephalin gene of both actinopterygian and sarcopterygian fish contained both the Met-enkephalin and Leu-enkephalin sequences.

Detection of Met-enkephalin in the CNS of the teleosts, Anguilla rostrata and Oncorhynchus kisutch

Acid extracts of the brains of the American eel, Anguilla rostrata, and the coho salmon, Oncorhynchus kisutch, were screened for enkephalin-related products and dynorphin-related products. Following Sephadex G-50 column chromatography, a peak of Met-enkephalin-related immunoreactivity was detected near the total volume of the column for both species. No higher molecular weight forms of Met-enkephalin-related material were detected, nor were any immunoreactive forms with antigenic determinants similar to mammalian dynorphin A(1-17), dynorphin A(1-8), dynorphin B(1-13) or alpha-neo-endorphin detected for either species. The enkephalin-sized immunoreactivity was further analyzed by reverse phase HPLC. For both species, a peak of authentic Met-enkephalin was detected. However, Leu-enkephalin, Met-enkephalin-RGL and Met-enkephalin-RF were not detected by RIA in either species. In addition, no novel C-terminally extended forms of Met-enkephalin were detected in either species. Finally, opiate receptor binding activity was only found associated with the peak of immunoreactive Met-enkephalin.