Purification of the two major forms of rat pituitary corticotropin using only reversed-phase liquid chromatography

Chromatographic Methods for the Purification of Granulin Peptides

Progranulin is composed of seven repeating cysteine-rich granulin domains. In some cells and tissues, the progranulin is fragmented by proteolysis to generate the granulin modules as individual peptides, which are collectively referred to as granulins. These peptides are often biologically active, but the activity need not be identical to that of the parental progranulin from which they are derived. Thus, some granulin peptides stimulate cell proliferation, as does progranulin itself, while other granulin peptides suppress proliferation. Similarly, some granulin peptides promote inflammation even though progranulin itself suppresses inflammation. Investigating the structural and biological properties of granulin peptides is challenging. Here we discuss methods that employ reversed-phase high-performance liquid chromatography (RP-HPLC) and in some instances size-exclusion high-performance liquid chromatography (SE-HPLC) to isolate granulin peptides from tissues, in particular those that are rich in inflammatory cells such as neutrophils, bone marrow, or hematopoietic organs of teleost fish.

The pituitary-interrenal axis of fish: a review focusing on the lamprey and flounder

In fish, the pituitary-interrenal axis is associated with stress response and a variety of biological processes such as metabolism, immune response, and growth. The major hormones involved in this axis are adrenocorticotropic hormone (ACTH), released from the pars distalis of the pituitary gland, and corticosteroid, released from the interrenal gland that is embedded in the head kidney in ray-finned fish. The ACTH signal, by which corticosteroid release is stimulated, is transmitted by melanocortin (MC) receptors on interrenal cells. Thus, the interaction of ACTH and MC receptors is the pivotal event for interrenal cells. Knowledge about ACTH and MC receptors in lamprey, cartilaginous fish, and ray-finned fish is available, and it suggests the pituitary-interrenal axis was established early in vertebrate evolution. Moreover, the data, including our recent results from flounders and lampreys, provide interesting features about ligand-receptor interactions. This review focuses on the characteristics of ACTH, the proopiomelanocortin gene encoding ACTH, and the MC receptor, and it is mostly based on the results of our investigations.

On-chip solid-phase extraction pre-concentration/focusing substrates coupled to atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry for high sensitivity biomolecule analysis

Atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI) has proven a convenient and rapid method for ion production in the mass spectrometric (MS) analysis of biomolecules. AP-MALDI and electrospray ionization (ESI) sources are easily interchangeable in most mass spectrometers. However, AP-MALDI suffers from less-than-optimal sensitivity due to ion losses during transport from the atmosphere into the vacuum of the mass spectrometer. Here, we study the signal-to-noise ratio (S/N) gains observed when an on-chip dynamic pre-concentration/focusing approach is coupled to AP-MALDI for the MS analysis of neuropeptides and protein digests. It was found that, in comparison with conventional AP-MALDI targets, focusing targets showed (1) a sensitivity enhancement of approximately two orders of magnitude with S/N gains of 200-900 for hydrophobic substrates, and 150-400 for weak cation-exchange (WCX) substrates; (2) improved detection limits as low as 5 fmol/microL for standard peptides; (3) significantly reduced matrix background; and (4) higher inter-day reproducibility. The improved sensitivity allowed successful tandem mass spectrometric (MS/MS) sequencing of dilute solutions of a derivatized tryptic digest of a protein standard, and enabled the first reported AP-MALDI MS detection of neuropeptides from Aedes aegypti mosquito heads.

Intrinsic neurons of Drosophila mushroom bodies express short neuropeptide F: relations to extrinsic neurons expressing different neurotransmitters

Mushroom bodies constitute prominent paired neuropils in the brain of insects, known to be involved in higher olfactory processing and learning and memory. In Drosophila there are about 2,500 intrinsic mushroom body neurons, Kenyon cells, and a large number of different extrinsic neurons connecting the calyx, peduncle, and lobes to other portions of the brain. The neurotransmitter of the Kenyon cells has not been identified in any insect. Here we show expression of the gene snpf and its neuropeptide products (short neuropeptide F; sNPFs) in larval and adult Drosophila Kenyon cells by means of in situ hybridization and antisera against sequences of the precursor and two of the encoded peptides. Immunocytochemistry displays peptide in intrinsic neuronal processes in most parts of the mushroom body structures, except for a small core in the center of the peduncle and lobes and in the alpha'- and beta'-lobes. Weaker immunolabeling is seen in Kenyon cell bodies and processes in the calyx and initial peduncle and is strongest in the more distal portions of the lobes. We used different antisera and Gal4-driven green fluorescent protein to identify Kenyon cells and different populations of extrinsic neurons defined by their signal substances. Thus, we display neurotransmitter systems converging on Kenyon cells: neurons likely to utilize dopamine, tyramine/octopamine, glutamate, and acetylcholine. Attempts to identify other neurotransmitter components (including vesicular glutamate transporter) in Kenyon cells failed. However, it is likely that the Kenyon cells utilize an additional neurotransmitter, yet to be identified, and that the neuropeptides described here may represent cotransmitters.

Biochemical, molecular, and functional characterization of PISCF-allatostatin, a regulator of juvenile hormone biosynthesis in the mosquito Aedes aegypti

Aedes aegypti PISCF-allatostatin or allatostatin-C (Ae-AS-C) was isolated using a combination of high performance liquid chromatography and enzyme-linked immunosorbent assay (ELISA). The matrix-assisted laser desorption/ionization time-of-flight (TOF) mass spectrum of positive ELISA fractions revealed a molecular mass of 1919.0 Da, in agreement with the sequence qIRYRQCYFNPISCF, with bridged cysteines. This sequence was confirmed by matrix-assisted laser desorption/ionization tandem TOF/TOF mass spectrometry analysis. The corresponding Ae-AS-C cDNA was amplified by PCR, and the sequence of the peptide was confirmed. An in vitro radiochemical assay was used to study the inhibitory effect of synthetic Ae-AS-C on juvenile hormone biosynthesis by the isolated corpora allata (CA) of adult female A. aegypti. The inhibitory action of synthetic Ae-AS-C was dose-dependent; with a maximum at 10(-9) m. Ae-AS-C showed no inhibitory activity in the presence of farnesoic acid, an immediate precursor of juvenile hormone, indicating that the Ae-AS-C target is located before the formation of farnesoic acid in the pathway. The sensitivity of the CA to inhibition by Ae-AS-C in the in vitro assay varied during the adult life; the CA was most sensitive during periods of low synthetic activity. In addition, the levels of Ae-AS-C in the brain were studied using ELISA and reached a maximum at 3 days after eclosion. These studies suggest that Ae-AS-C is an important regulator of CA activity in A. aegypti.

Evolution of melanocortin systems in fish

Proopiomelanocortin (POMC) is a common precursor of melanocortin (MC), the collective term for adrenocorticotropic hormone (ACTH) and melanophore-stimulating hormone (MSH), and of beta-endorphin (beta-END). Over the past decade, considerable progress has been made in the analysis of the POMC gene from a board taxonomic group of vertebrates and invertebrates. The results suggest that three MSHs (alpha-, beta-, and gamma-MSH) and a single END were established in ancestral invertebrates. Thereafter, unequal crossing over may have resulted in class-specific numbers of MSH segments during the radiation of fish. Moreover, duplication of the entire POMC gene may have led to the differentiation of POMC as shown in lampreys; one of the two subtypes is a precursor for ACTH and beta-END, the other is a precursor for two forms of MSH and the other form of beta-END. On the other hand, at least five subtypes of MC receptor (MCR) have been observed in fish. These are G-protein-coupled receptors with seven transmembrane domains. The ancestral MCR is suggested to have appeared before vertebrates, and then MCRs may have diverged by genome duplication and local duplication of each receptor gene during the evolution of vertebrates. They are distributed in many tissues in rather a subtype-specific manner and are responsible for a variety of biological functions. Thus, MC systems may have diverged by producing structurally different MC peptides from POMC and expressing MCR subtypes differing in ligand selectivity in a variety of tissues.

Posttranslational processing of proopiomelanocortin family molecules in sea lamprey based on mass spectrometric and chemical analyses

In gnathostomes, adrenocorticotropic hormone (ACTH), melanophore-stimulating hormones (MSHs), and beta-endorphin (beta-END) are derived from a common precursor, proopiomelanocortin. In sea lamprey, ACTH and two forms of MSHs are contained in independent precursors, proopiocortin (POC), and proopiomelanotropin (POM), respectively, together with a distinct beta-END. Here, we characterized products from POC and POM. An analysis of previously purified ACTH by mass spectrometry (MS) detected four peptides with a molecular weight of 6469.4, 6549.6, 6556.6, or 6636.1. The sequence analysis of an ACTH preparation following enzymatic and chemical cleavage revealed the presence of ACTH(1-59) and ACTH(1-60) corresponding to a molecular weight of 6469.4 and 6556.6, respectively, and of ACTH(1-59) and ACTH(1-60) modified at Ser(35) by a group having a mass of 80, giving the molecular weight 6549.6 and 6636.1, respectively. The modification could be due to phosphorylation based on the increase in molecular weight of 80. Analyses of frozen pituitary slices with MALDI-TOF MS detected several mass numbers corresponding to POC-derived peptides such as ACTH(1-60), modified ACTH(1-60), and (POC)beta-END, and those corresponding to POM-derived peptides such as MSH-A, MSH-B, and the C-terminal fragment of (POM)beta-END lacking a Met-enkephalin segment. The present results together with previous characterizations show that in sea lamprey pituitary the major products derived from POC in the PD by posttranslational processing are ACTH and beta-END as in gnathostomes. The posttranslational processing of POM in the PI is similar to that in gnathostomes in the sense of the occurrence of MSH, however, it differs in that beta-END is further cleaved, thus generating Met-enkephalin.

The zebrafish progranulin gene family and antisense transcripts

Background

Progranulin is an epithelial tissue growth factor (also known as proepithelin, acrogranin and PC-cell-derived growth factor) that has been implicated in development, wound healing and in the progression of many cancers. The single mammalian progranulin gene encodes a glycoprotein precursor consisting of seven and one half tandemly repeated non-identical copies of the cystine-rich granulin motif. A genome-wide duplication event hypothesized to have occurred at the base of the teleost radiation predicts that mammalian progranulin may be represented by two co-orthologues in zebrafish.

Results

The cDNAs encoding two zebrafish granulin precursors, progranulins-A and -B, were characterized and found to contain 10 and 9 copies of the granulin motif respectively. The cDNAs and genes encoding the two forms of granulin, progranulins-1 and -2, were also cloned and sequenced. Both latter peptides were found to be encoded by precursors with a simplified architecture consisting of one and one half copies of the granulin motif. A cDNA encoding a chimeric progranulin which likely arises through the mechanism of trans-splicing between grn1 and grn2 was also characterized. A non-coding RNA gene with antisense complementarity to both grn1 and grn2 was identified which may have functional implications with respect to gene dosage, as well as in restricting the formation of the chimeric form of progranulin. Chromosomal localization of the four progranulin (grn) genes reveals syntenic conservation for grna only, suggesting that it is the true orthologue of mammalian grn. RT-PCR and whole-mount in situ hybridization analysis of zebrafish grns during development reveals that combined expression of grna and grnb, but not grn1 and grn2, recapitulate many of the expression patterns observed for the murine counterpart. This includes maternal deposition, widespread central nervous system distribution and specific localization within the epithelial compartments of various organs.

Conclusion

In support of the duplication-degeneration-complementation model of duplicate gene retention, partitioning of expression between grna and grnb was observed in the intermediate cell mass and yolk syncytial layer, respectively. Taken together these expression patterns suggest that the function of an ancestral grn gene has been devolved upon four paralogues in zebrafish.

A novel form of neurotensin post-translationally modified by arginylation

A novel bioactive form of neurotensin post-translationally modified at a Glu residue was isolated from porcine intestine. Purification of the peptide was guided by detection of intracellular Ca2+ release in SK-N-SH neuroblastoma cells. Using high resolution accurate mass analysis on an ion trap Fourier transform mass spectrometer, the post-translational modification was identified as arginine linked to the gamma-carboxyl of Glu via an isopeptide bond, and we named the newly identified peptide "arginylated neurotensin" (R-NT, N-(neurotensin-C5-4-yl)arginine). Although arginylation is a known modification of N-terminal amino groups in proteins, its presence at a Glu side chain is unique. The finding places neurotensin among the few physiologically active peptides that occur both in post-translationally modified and unmodified forms. Pharmacologically, we characterized R-NT for its ligand activity on three known neurotensin receptors, NTR1, -2, and -3, and found that R-NT has similar pharmacological properties to those of neurotensin, however, with a slightly higher affinity to all three receptors. We expressed the intracellular receptor NTR3 as a soluble protein secreted into the cell culture medium, which allowed characterization of its R-NT and neurotensin binding properties. The creation of soluble NTR3 also provides a potential tool for neutralizing neurotensin action in vivo and in vitro. We have shown that SK-N-SH neuroblastoma cells express NTR1 and NTR3 but not NTR2, suggesting that the Ca2+ mobilization elicited by R-NT is via NTR1.

Pigment-dispersing factor in the locust abdominal ganglia may have roles as circulating neurohormone and central neuromodulator

Pigment-dispersing factor (PDF) is a neuropeptide that has been indicated as a likely output signal from the circadian clock neurons in the brain of Drosophila. In addition to these brain neurons, there are PDF-immunoreactive (PDFI) neurons in the abdominal ganglia of Drosophila and other insects; the function of these neurons is not known. We have analyzed PDFI neurons in the abdominal ganglia of the locust Locusta migratoria. These PDFI neurons can first be detected at about 45% embryonic development and have an adult appearance at about 80%. In each of the abdominal ganglia (A3-A7) there is one pair of lateral PDFI neurons and in each of the A5-A7 ganglia there is additionally a pair of median neurons. The lateral neurons supply varicose branches to neurohemal areas of the lateral heart nerves and perisympathetic organs, whereas the median cells form processes in the terminal abdominal ganglion and supply terminals on the hindgut. Because PDF does not influence hindgut contractility, it is possible that also these median neurons release PDF into the circulation. Release from one or both the PDFI neuron types was confirmed by measurements of PDF-immunoreactivity in hemolymph by enzyme immunoassay. PDF applied to the terminal abdominal ganglion triggers firing of action potentials in motoneurons with axons in the genital nerves of males and the 8th ventral nerve of females. Because this action is blocked in calcium-free saline, it is likely that PDF acts via interneurons. Thus, PDF seems to have a modulatory role in central neuronal circuits of the terminal abdominal ganglion that control muscles of genital organs.

Ser(13)-phosphorylated PYY from porcine intestine with a potent biological activity

We have isolated a posttranslationally modified form of peptide YY (PYY) from porcine intestine and shown by MALDI-TOF and electrospray tandem mass spectrometry that it is phosphorylated at Ser(13). Phospho-PYY exhibits high affinity for binding to neuropeptide Y (NPY) receptors Y1, Y2 and Y5. The IC(50) values with the Y1, Y2, and Y5 receptor subtypes were for NPY 2.4, 3.1, and 3.3 nM, for PYY 2.3, 0.94, and 3.2 nM, and for phospho-PYY 4.6, 2.2, and 5.5 nM, respectively. Phospho-PYY potently inhibits forskolin-stimulated cAMP accumulation in SK-N-MC cells with an IC(50) value of 0.5 nM compared to 0.15 nM for non-phosphorylated PYY. The finding of phosphorylation of PYY is unusual among hormonal peptides, and emphasizes the importance of direct protein analysis of gene products.

Proparathyroid hormone processing by the proprotein convertase-7: comparison with furin and assessment of modulation of parathyroid convertase messenger ribonucleic acid levels by calcium and 1,25-dihydroxyvitamin D3

We previously showed that the processing of proparathyroid hormone (proPTH) to PTH was accomplished most efficiently by furin (17). Colocalization studies demonstrated that furin is expressed in the parathyroid, whereas proprotein convertase (PC)1 and PC2 are not. Since that time, another member of the PC family, called PC7, has been identified. Here we show, using coinfection studies, that PC7, as well as furin, can appropriately cleave PTH from proPTH. ProPTH and PTH were purified from cell extracts by reversed-phase HPLC and were identified by Western blot analysis and delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Colocalization studies, using Northern blot and reverse transcriptase-PCR analyses, showed that PC7 messenger RNA (mRNA) is expressed in the parathyroid gland. Therefore, PC7, like furin, has the potential to be involved in the physiological processing of proPTH to PTH. The two major regulators of parathyroid cell synthetic and secretory activity are the extracellular fluid calcium and 1,25-dihydroxyvitamin D [1,25(OH)2D] levels. We investigated whether either of these agents might modulate processing of proPTH to PTH by altering parathyroid convertase gene expression. In both in vitro and in vivo systems in which regulation of PTH mRNA levels were clearly apparent, there was no effect of either calcium or 1,25(OH)2D3 on parathyroid furin or PC7 mRNA levels. This is in contrast to the processing of proinsulin to insulin in the pancreatic beta-cell, which is up-regulated by glucose stimulation of PC1 and PC2 synthesis.

Isolation and identification of three RFamide-immunoreactive peptides from the mosquito Aedes aegypti

Three RFamide-immunoreactive peptides were isolated from headless Aedes aegypti mosquitoes. Their structures were identified by Edman degradation or a combination of amino acid composition analysis and mass spectrometry to be: Aedes head peptide 1 [23], [Pro4]-Aedes head peptide (i.e., pGlu-Arg-Pro-Pro-Ser-Leu-Lys-Thr- Arg-Phe-amide), and Leu-Lys-Thr-Arg-Phe-amide which have been named Aedes head peptides 3 and 4, respectively.

Isolation and identification of a peptide and its cDNA from the mosquito Aedes aegypti related to Manduca sexta allatotropin

Immunocytochemistry revealed that an allatotropin-immunoreactive peptide is produced by several neuroendocrince cells in the abdominal ganglia of the mosquito Aedes aegypti. The immunoreactive peptide was isolated and its structure determined to be Ala-Pro-Phe-Arg-Asn-Ser-Glu-Met-Met-Thr-Ala-Arg-Gly-Phe-amide. A cDNA clone encoding this novel neuropeptide was shown to encode a single copy of this peptide. The cDNA is unusual in that the first seven ATGs are not used for translation initiation.

Isolation of a member of the neurotoxin/cytotoxin peptide family from Xenopus laevis skin which activates dihydropyridine-sensitive Ca2+ channels in mammalian epithelial cells

We have used a sensitive bioassay of calcium-mediated volume changes in mammalian absorptive intestinal epithelial cells to screen extracts of the skin of the amphibian Xenopus laevis for the presence of factors affecting ion transport. A 66-residue peptide, purified using reversed-phase high performance liquid chromatography techniques, caused isotonic volume reduction of guinea pig jejunal villus cells in suspension. This volume reduction required extracellular Ca2+ and was prevented by the dihydropyridine-sensitive Ca2+ channel blocker niguldipine. Structural analysis demonstrated the presence of eight cysteines and a primary structure homologous to that of the neurotoxin/cytotoxin family found in the venom of certain poisonous snakes. The structure of the peptide was identical to that of xenoxin-1 purified from dorsal gland secretions of X. laevis (Kolbe, M., Huber A., Cordier, P., Rasmussen, U., Bouchon, B., Jaquinod, M., Blasak, R., Detot, E., and Kreil, G. (1993) J. Biol. Chem. 268, 16458-16464). Xenoxin-1 (10 nM) caused volume changes that required extracellular Ca2+ and were comparable in magnitude and direction to changes caused by BayK-8644 (100 nM), a dihydropyridine-sensitive Ca2+ channel agonist. The initial rate of dihydropyridine-sensitive 45Ca2+ influx was substantially increased by xenoxin-1. Staurosporine (10 nM) prevented volume changes caused by ATP (250 microM) but had no effect on volume changes caused by BayK-8644 or xenoxin-1. We conclude that xenoxin-1 directly activated dihydropyridine-sensitive Ca2+ channels in villus cells and that a mammalian homologue to xenoxin-1 may exist.

Purification of calcitonin-like peptides from rat brain and pituitary

Accumulating evidence supports the existence of nonthyroidal calcitonin (CT)-like peptides, more similar to fish CTs, which may act as endogenous regulators of CT receptors in brain and other tissues. In this study, we have carried out large-scale extractions from Sprague-Dawley rat brain diencephalon and pituitary, and purified a novel, biologically active, CT-like peptide from pituitary. Monitoring of the calcitonin-like activity of the peptides from rat brain and pituitary required different detection systems. While the brain CT cross-reacted with C-terminally directed salmon CT-specific antisera, the pituitary CT did not. However, the pituitary CT was biologically active, exhibiting specific interaction with CT receptors to activate adenylate cyclase. Conventional chromatographic techniques were employed to purify the CT-like peptides. Although the brain CT was not purified to homogeneity, size exclusion chromatography revealed the presence of multiple molecular weight forms of immunoreactive CT. Of these, only the lowest molecular weight form was biologically active. Purification from the pituitary resulted in the isolation of a biologically active peptide with a mass of 3267 Da. This mass differs from the mass of both salmon and thyroid-derived rat CT. Initial amino acid sequencing of the pituitary CT indicated that it was N-terminally blocked. Following aminopeptidase digestion, a unique six amino acid sequence, EKSQSP, was identified. Elucidation of the amino acid composition provided supporting evidence that the peptide was novel and was consistent with a full length peptide of approximately 30 amino acids. These data support the existence of novel, nonthyroidal, CTs which are potential regulators of CT receptor-mediated functions.

RK-2: a novel rabbit kidney defensin and its implications for renal host defense

Defensins are endogenous antimicrobial peptides. We demonstrated recently the existence of RK-1, a defensin-like peptide in rabbit kidneys. Defining the renal-defensin system is an essential step toward understanding how the kidney responds to infection. Here, using a combination of high-performance liquid chromatography, matrix-assisted laser desorption time-of-flight mass spectrometry, amino acid compositional analysis, and microsequence analysis, we show that the rabbit kidney contains a novel alpha-defensin-like peptide, RK-2. This work establishes the existence of a new subfamily of alpha-defensins in the kidney.

Allatostatin-like-immunoreactive neurons of the tobacco hornworm, Manduca sexta, and isolation and identification of a new neuropeptide related to cockroach allatostatins

The YXFGLamide C-terminus serves to define most members of a family of structurally related neuropeptides, the YXFGLamides. These peptides have been identified from the nervous system of various insects and include the allatostatins of cockroaches and crickets, the schistostatins of locusts, and the callatostatins of blowflies. The YXFGLamides have been shown to have various functions, including inhibition of juvenile hormone biosynthesis in cockroaches and crickets and inhibition of contraction of certain insect visceral muscles. We wanted to know if these peptides occur in Manduca sexta and what functions they might have. A new peptide, AKSYNFGLamide, was isolated and identified from M. sexta and has been named "lepidostatin-1"; this is the first YXFGLamide to be found in a lepidopteran, and there are indications that additional YXFGLamides occur in M. sexta. An antiserum to cockroach allatostatins (YXFGLamides) was shown to recognize lepidostatin-1 of M. sexta and was used to map YXFGLamide-immunoreactive neurons in larvae. Because immunoreactive interneurons were found to form an extensive neuropil, YXFGLamides probably function as neuromodulators in M. sexta. Neuroendocrine cells in the brain, abdominal ganglia, and their respective neurohemal organs were YXFGLamide immunoreactive and appear to release YXFGLamides as neurohormones. Immunoreactivity to YXFGLamides and M. sexta diuretic hormone were found to be colocalized and appear to be coreleased in these neuroendocrine cells, indicating that YXFGLamides may be involved in regulation of fluid transport. Innervation of the corpora allata by YXFGLamide-immunoreactive processes was very sparse, suggesting that this innervation does not play an important role in allatostasis. Many thoracic motor neurons were YXFGLamide immunoreactive, suggesting that YXFGLamides may have a myomodulatory or myotrophic function in larvae. However, this immunoreactivity disappeared early in metamorphosis and did not reappear in the adult. The YXFGLamide-immunoreactive neurons in the terminal abdominal ganglion were found to innervate the hindgut, indicating that YXFGLamides may be involved in the control of the rate of myogenic contractions of the larval hindgut.

Seven tachykinin-related peptides isolated from the brain of the Madeira cockroach: evidence for tissue-specific expression of isoforms

We have isolated seven tachykinin-related peptides (TRPs) from an acidic extract of 1000 brains of the cockroach Leucophaea maderae. Four different reversed-phase high performance liquid chromatography (RP-HPLC) column systems were required to obtain pure peptides. During the purification the fractions were monitored in a radioimmunoassay (RIA) with an antiserum to locust TRP locustatachykinin I (LomTK I) and a cockroach hindgut muscle contraction bioassay. The sequences of the seven isolated LomTK immunoreactive and myostimulatory peptides were determined by Edman degradation. Six of these were confirmed by mass spectrometry and chemical synthesis as: APSGFLGVRamide, APAMGFQGVRamide, APAAGFFGMRamide, VPASGFFGMRamide, GPSMGFHGMRamide, and APSMGFQGMRamide. The seventh peptide, APEESPKRAPSGFLGVRamide, was confirmed only by mass spectrometry. These peptides were designated Leucophaea maderae tachykinin-related peptides 1, 2, 5-9 (LemTRP 1, 2, 5-9). Two more peptides were isolated using the same assays: SGLDSLSGATFGGNR and ALFEESTVSAEPR. The first shares the C-terminus FX1GX2R with the Lem TRPs, whereas the second one is not related to the TRPs (none of these peptides were synthesized and thus putative C-terminal amidation was not confirmed). Three of the brain peptides, LemTRP 1, 2, and 5, have previously been isolated from the midgut of L. maderae, whereas the others appear to be brain specific. Because the LemTRPs 3 and 4 appear to be unique for the midgut, we have indications for tissue-specific expression of TRPs. All seven confirmed LemTRPs of the brain are myotropic and induce increases in the amplitude and frequency of spontaneous contractions and tonus of hindgut muscle in L. maderae.

Ethanol-induced change in cardiac and endogenous opiate function and risk for alcoholism

Susceptibility to alcoholism varies with age, gender, and familial background. Youthful nonalcoholic males with multigenerational family histories of male alcoholism seem at particular risk. Previous investigations suggest that such males are characterized by abnormal psychophysiological response, while sober and alcohol-intoxicated; additional recent studies indicate that the endogenous opiate systems are involved in mediating ethanol reinforcement and modulating intake. We first compared cardiac response to alcohol administration among young (mean = 22.8 years), nonalcoholic men and women with multigenerational, unigenerational, and negative family histories of alcohol dependence and abuse. Then, we compared the ethanol-induced cardiac response of the males in these three groups to that of currently alcohol-dependent older males and age-matched nonalcoholic male controls. Finally, we examined ethanol-induced change in plasma beta-endorphin and cortisol levels among a subset of the nonalcoholic males, divided into those with high and low levels of postethanol administration heart-rate increase. Nonalcoholic males with multigenerational family histories of male alcoholism were characterized by significantly higher [t(301) = 5.70, p < 0.0001, Cohen's d = 0.73] levels of ethanol-induced heart-rate increase than nonalcoholics from all other comparison groups. The magnitude of their increase matched that of current male alcohol-dependents. Nonalcoholic males with high levels of ethanol-induced heart-rate increase also produced significantly more plasma beta-endorphin after consuming alcohol. Peak production of beta-endorphin was highly correlated (r = 0.861, p < 0.001) with magnitude of heart-rate increase. A subset of those at risk for alcoholism may be characterized by sensitivity to ethanol-induced reward, marked by heightened ethanol-induced, heart-rate increase, mediated by ethanol stimulation of endogenous opiate production. This subset might contain those who, once alcoholic, would differentially benefit from treatment with opiate antagonists.

Radioimmunoassay determination of tachykinin-related peptide in different portions of the central nervous system and intestine of the cockroach Leucophaea maderae

A radioimmunoassay was developed for insect tachykinin-related peptides with the use of an antiserum raised to the locust neuropeptide locustatachykinin I (LomTK I). Determination of tachykinin-related peptide was performed in different tissues of the cockroach Leucophaea maderae. The largest amounts of LomTK-like immunoreactivity (LomTK-LI) reside in the brain and in the midgut. Relatively large amounts were also found in the suboesophageal ganglion and throughout the ganglia of the ventral nerve cord, whereas smaller amounts of LomTK-LI were detected in the corpora cardiaca, foregut and hindgut. Extracts of unfused abdominal ganglia and midguts, respectively, were analysed by a combination of reversed phase high performance liquid chromatography, and radioimmunoassay for LomTK-LI. The extracts of abdominal ganglia and midguts both contain LomTK-LI material which separates in at least two major components. This LomTK-LI material had retention times corresponding approximately to those of synthetic LomTK I and II. Since the cellular source of LomTK-LI material in the foregut and hindgut was not known from earlier studies, we investigated these tissues by immunocytochemistry. We found that the LomTK-LI material associated with the foregut was in arborizing fibres in the oesophageal and gastric nerves and in the ingluvial ganglion. In the hindgut the muscle layer was innervated by immunoreactive fibres derived from cell bodies in the terminal ganglion. The amount of LomTK-LI material in other portions of the nervous system correlates well with previous immunocytochemical data. We conclude that L. maderae have two or more isoforms of tachykinin-related peptides in the nervous system and intestine and that these are present in various amounts in different parts of the central nervous system and intestine. The relative large amounts of LomTK-LI material in the suboesophageal ganglion, oesophageal nerve and associated ganglia and intestine indicate important roles of tachykinin-related peptides in feeding and digestion.

Isolation of five tachykinin-related peptides from the midgut of the cockroach Leucophaea maderae: existence of N-terminally extended isoforms

Using a radioimmunoassay (RIA) with an antiserum to the locust neuropeptide locustatachykinin I (LomTK I) and a cockroach hindgut contraction bioassay as monitors, we isolated 5 tachykinin-related peptides from an acidic extract of 600 midguts of the cockroach Leucophaea maderae. A series of 4 different reversed-phase high performance liquid chromatography (rpHPLC) column systems were required to obtain pure peptides. The sequences of the 5 isolated myostimulatory and LomTK immunoreactive peptides were determined by Edman degradation. Four of these were confirmed by mass spectrometry and chemical synthesis as: APSGFLGVRamide, NGERAPGSKKAPSGFLGTRamide, APAMGFQGVRamide and APSGFMGMRamide. The fifth peptide, APEESPKRAPSGFLGVRamide, was confirmed only by mass spectrometry. These peptides, which were designated Leucophaea tachykinin-related peptides 1-5 (LemTRP 1-5), are structurally related to tachykinin-related peptides previously isolated from a locust, blowfly and mosquito species, but showed a somewhat larger variability in their amino-acid sequence (including the carboxy terminus). The two N-terminally extended forms contain putative cleavage sites (KR and KK, respectively) and such extended tachykinins have not been previously identified in insects. All 5 LemTRPs are myotropic and induce increases in the tonus and frequency of spontaneous contractions of hindgut muscle in L. maderae. The potency of the different synthetic isoforms is very similar; they all have a stimulus threshold concentration of 2.5 x 10(-10) M and an ED50 of about 10(-9) M. The synthetic peptides were tested in RIA and found to cross react to different degrees with the antiserum to LomTK I, but it is likely that in immunocytochemistry performed earlier, all 5 forms were detected in the midgut. It is, however, not clear which isoforms are located in endocrine cells and neural fibers of the midgut, respectively.

Relationship between circulating levels of calcitonin gene-related peptide, nitric oxide metabolites and hemodynamic changes in human septic shock

This study is aimed to investigate the relationship between plasma concentrations of nitrite and nitrate as a measure of ongoing nitric oxide (NO) production, the vasodilatory neuropeptides calcitonin gene-related peptide (CGRP) and substance P (SP), endotoxemia and hemodynamic changes in human septic shock. Thirteen patients with septic shock were studied within 6 h after the development of hypotension. Hemodynamic measurements and blood samples were recorded simultaneously at 2-h intervals from study admission. Eighteen normotensive patients with sepsis were included as control group of patients. On study entry, circulating levels of endotoxin did not relate to either CGRP or nitrite and nitrate plasma values. Septic shock patients had significantly higher plasma CGRP, and nitrite and nitrate concentrations, at each of the four time points, than patients with sepsis, as well as both groups of patients compared to normal subjects. No differences were found in plasma SP levels between the two groups of patients. For pooled data from all septic shock patients and measurements (n = 52), both plasma concentrations of CGRP and nitrite and nitrate were inversely correlated, independently from each other, to systemic vascular resistance. On study admission and at 2-h intervals, plasma CGRP concentrations correlated directly with nitrite and nitrate values. Our observations, thus, point to CGRP acting in concert with NO as important mediators responsible for hypotension in human septic shock.

Pheromone biosynthesis activating neuropeptides: functions and chemistry

Sex pheromones are critical for reproductive success in most species of Lepidoptera and their production is regulated by the action of pheromone biosynthesis activating neuropeptides (PBAN). These peptides, composed of 33-34 amino acids, have approximately 80% sequence homology and share the C-terminal sequence FSPRL-NH2, which has been shown to be the minimum sequence required for pheromonotropic activity. This pentamer is structurally similar to the active core (FXPRL-NH2, X = V, T or G) of the insect myotropic pyrokinins. Structure-activity studies have shown that all of the pyrokinins have various degrees of pheromonotropic activity and that some have a superagonistic effect. Peptides that only have sequence homology with PBAN in the C-terminal pentapeptide region, but that are pheromonotropic, also have been identified from months. These findings suggest that induction of pheromone biosynthesis may be regulated by more than one peptide, that PBAN may have a number of physiological functions, and that these peptides regulate induction of pheromone production in a variety of ways.

Immunohistological localization of regulatory peptides in the midgut of the female mosquito Aedes aegypti

The midgut of the female mosquito Aedes aegypti was studied immunohistologically with antisera to various regulatory peptides. Endocrine cells immunoreactive with antisera to perisulfakinin, RFamide, bovine pancreatic polypeptide, urotensin 1, locustatachykinin 2 and allatostatins A1 and B2 were found in the midgut. Perisulfakinin, RFamide and bovine pancreatic polypeptide all react with the same, about 500 endocrine cells, which were evenly distributed throughout the posterior midgut, with the exception of its most frontal and caudal regions. In addition, these antisera recognized three to five neurons in each ingluvial ganglion and their axons, which ran longitudinally over the anterior midgut, as well as axons innervating the pyloric sphincter. The latter axons appear to be derived from neurons located in the abdominal ganglia. Antisera to two different allatostatins recognized about 70 endocrine cells in the most caudal area of the posterior midgut and axons in the anterior midgut whose cell bodies were probably located in either the brain or the frontal ganglion. Antiserum to locustatachykinin 2 recognized endocrine cells present in the anterior midgut and the most frontal part of the posterior midgut, as well as about 50 cells in the most caudal region of the posterior midgut. Urotensin 1 immunoreactivity was found in endocrine cells in the same region as the perisulfakinin-immunoreactive cells, but no urotensin-immunoreactive axons were found in the midgut. Double labeling experiments showed that the urotensin and perisulfakinin immunoreactivities were located in different cells. Such experiments also showed that the locustatachykinin and allatostatin immunoreactivities in the most caudal area of the posterior midgut were present in different cells. No immunoreactivity was found in the mosquito midgut when using antisera to corazonin, allatropin or leucokinin IV. Since these peptides have either been isolated from, or can reasonably be expected to be present in mosquitoes, it was concluded that these peptides are not present in the mosquito midgut.

Inhibition of intestinal secretion by rice

Rates of stool output are reduced when cooked rice is incorporated into oral rehydration solutions. We found that a fraction extracted from rice inhibited the response of intestinal epithelial crypt cells to adenosine 3'5'-cyclic monophosphate, a major intracellular mediator of secretion. This response to rice was seen as an inhibition of cell shrinkage and of chloride efflux in fresh suspended guinea pig crypt cells. The active fraction was of low molecular weight (< 1.5 kDa), hydrophobic, and not a peptide or glycoprotein. It may be chloride-channel blocker.

Proparathyroid hormone is preferentially cleaved to parathyroid hormone by the prohormone convertase furin. A mass spectrometric study

Parathyroid hormone (PTH), an 84-amino acid peptide, is the major regulator of blood calcium homeostasis. Its mRNA, in addition to encoding the mature peptide, also encodes a "pre" sequence of 25 amino acids and a basic "pro" hexapeptide. To assess which of the subtilisin-like prohormone convertases can process proPTH to PTH we coinfected cells with a vaccinia virus construct expressing human preproPTH and vaccinia virus constructs expressing furin, PC1 or PC2. BSC-40 cells, having a constitutive secretory pathway, and GH4C1 cells, having a regulated secretory pathway, were used. PTH biosynthetic products in cell extracts and media were purified by high performance liquid chromatography, identified by radioimmunoassay, and unambiguously defined as either proPTH or PTH by ion-spray mass spectrometry. In both cell types, furin was the most effective in processing proPTH to PTH. In all cases only PTH was released into the medium. In addition, partially purified furin and PC1 were tested for their ability to appropriately cleave a tridecapeptide spanning the prohormone cleavage site found in proPTH. Here too furin was much more effective at cleaving at the correct site. Northern blot analysis and in situ hybridization showed that furin and preproPTH mRNA are co-expressed in the parathyroid, whereas PC1, PC2, and PC5 are not and PACE4 is expressed only at very low levels. Taken together these studies strongly suggest that furin is the enzyme responsible for the physiological processing of proPTH to PTH.

Mass spectrometric and biological characterization of guinea-pig corticotrophin

Guinea-pig ACTH has been found to be distinct from other mammalian ACTHs in having an alanine for proline substitution at position 24 and in having superagonist aldosterone-stimulating activity relative to synthetic ACTH(1-24) in an isolated rat glomerulosa cell bioassay. We have purified ACTH from extracts of guinea-pig anterior pituitary and confirmed its unusual structural characteristics by amino acid analysis and mass spectrometry. Using isolated rat adrenal fasciculata-reticularis and glomerulosa cell bioassays, guinea pig ACTH was found to have similar activity to that of human ACTH with respect to corticosterone- and aldosterone-stimulating activity, in terms of maximal steroid output but was slightly more potent in terms of the concentration which elicited half-maximal steroid secretion. Under the assay conditions used, guinea-pig ACTH appeared not to be a superagonist as previously suggested. Various biosynthetic derivatives of guinea-pig pro-opiomelanocortin were identified by amino acid analysis and mass spectrometry. Joining peptide, a major product of pro-opiomelanocortin processing, was found in extracts of both anterior and neurointermediate lobes of the pituitary. Post-translational modification of other products of intermediate lobe processing were observed. N- and O-acetylation of alpha-melanotropin, partial O-phosphorylation of corticotropin-like intermediate lobe peptide and carboxyl-terminal amidation of beta-melanotropin were identified.

Isolation of two AKH-related peptides from cicadas

Two peptides related to locust adipokinetic hormone and crustacean red pigment concentrating hormone were isolated by high performance liquid chromatography from the cicadas Cacama valavata and Diceroprocta semicincta. Both species have the same peptides. The structure of one of the peptides is pGlu-Val-Asn-Phe-Ser-Pro-Ser-Trp-Gly-Asn-amide. The mass spectrum, amino acid composition, and amino acid sequence of the other peptide suggest that it is almost identical to the first peptide. However, the exact nature of the difference between the two peptides could not be determined.

Postembryonic development of corazonin-containing neurons and neurosecretory cells in the blowfly, Phormia terraenovae

An antiserum against the cockroach cardioactive peptide corazonin was used to investigate the distribution of immunoreactive neurons and neurosecretory cells in the nervous system of the blowfly, Phormia terraenovae, during postembryonic development. A small number of corazonin-immunoreactive neurons was found at larval, pupal, and adult stages. At all postembryonic stages two cell groups were found in the protocerebrum of the brain: 1) two lateral cell clusters and 2) two median cells. In the larva eight bilateral cell pairs were found in thoracic and abdominal neuromeres of the fused ventral ganglion. The lateral brain neurons are located in the lateral neurosecretory cell group and extend axons with branches in several components of the retrocerebral neuroendocrine complex, in the stomatogastric nervous system of larvae and adults, and additionally in muscles of the alimentary canal in the adult. The most prominent element of these peripheral processes is a large plexus of varicose fibers located in the wall of the aorta, the main site for the release of neurohormones produced in the brain of blowflies. The presence of corazonin-immunoreactive material in the aortic plexus suggests that this peptide functions as a neurohormone. During metamorphosis, the immunoreactive neurons found in the thoracic-abdominal ganglion of the larva disappear, and in the brain new immunoreactive neurons are added to those that persist from larval stages. The bulk of the corazonin-immunoreactive material extracted from adult brains and corpora cardiaca-aorta complexes was found to co-elute with synthetic corazonin in reversed-phase high-performance liquid chromatography as monitored with enzyme-linked immunosorbent assay.

Manipulation of ion-pairing reagents for reversed-phase high-performance liquid chromatographic separation of phosphorylated opioid peptides from their non-phosphorylated analogues

The use of reversed-phase high-performance liquid chromatography for the separation of a mixture of 14 phosphorylated and non-phosphorylated enkephalins is described. The influence of two homologous series of hydrophobic ion-pairing reagents, consisting of perfluorinated carboxylic (trifluoroacetic, pentafluoropropionic and hexafluorobutyric) acids and sodium salts of sulfonic (butane-, hexane- and heptane-) acids, on the retention of enkephalin peptides was investigated. The incorporation of the phosphate group reduces retention time in proportion with the resulting change in hydrophobicity of the peptide. All peptides exhibit increase in retention time with increase in the counter ion hydrophobicity. The increase is proportional to the number of positively charged groups present in a peptide. Phosphopeptides show small increases in retention times than their corresponding non-phospho derivatives. The near-neighbor effect of the Tyr-O-phosphate group is responsible for suppression of the ion-pairing interaction of the mobile phase counter ions with the positively charged terminal amino group of enkephalins.

A comparative study of leucokinin-immunoreactive neurons in insects

Antisera were raised against leucokinin IV, a member of the leucokinin peptide family. Immunohistochemical localization of leucokinin immunoreactivity in the brain of the cockroach Nauphoeta cinerea revealed neurosecretory cells in the pars intercerebralis and pars lateralis, several bilateral pairs of interneurons in the protocerebrum, and a group of interneurons in the optic lobe. Several immunoreactive interneurons were found in the thoracic ganglia, while the abdominal ganglia contained prominent immunoreactive neurosecretory cells, which projected to the lateral cardiac nerve. The presence of leucokinins in the abdominal nerve cord was confirmed by HPLC combined with ELISA. Leucokinin-immunoreactive neurosecretory cells were also found in the pars intercerebralis of the cricket Acheta domesticus and the mosquito Aedes aegypti, but not in the locust Schistocerca americana or the honey bee Apis mellifera. However, all these species have leucokinin-immunoreactive neurosecretory cells in the abdominal ganglia. The neurohemal organs innervated by abdominal leucokinin-immunoreactive cells were different in each species.

Characterization of beta-endorphin- and alpha-MSH-related peptides in rat heart

POMC-derived peptides and mRNA have been identified in heart tissue, although POMC processing has not been fully characterized. In the present study, we found that beta-lipotropin and ACTH were localized in rat heart, although they were almost entirely converted to beta-endorphin- and alpha-MSH-related peptides. Ion exchange HPLC analysis revealed that beta-endorphin(1-31) was further processed to alpha-N-acetyl-beta-endorphin(1-31), which comprised 35.9 +/- 0.1% of total immunoreactivity, and smaller amounts of beta-endorphin(1-27), beta-endorphin(1-26), and their alpha-N-acetylated derivates. The predominant alpha-MSH immunoreactive peptides coeluted with alpha-MSH and N,O-diacetyl-alpha-MSH by reverse-phase HPLC, although small amounts of ACTH(1-13)-NH2 were also present. Thus, multiple forms of beta-endorphin and alpha-MSH are localized in rat heart. beta-Endorphin(1-31) is a minor constituent, however, indicating that nonopioid beta-endorphin peptides predominate.

Localization of corazonin in the nervous system of the cockroach Periplaneta americana

Antisera raised to the cardioactive peptide corazonin were used to localize immunoreactive cells in the nervous system of the American cockroach. Sera obtained after the seventh booster injection were sufficiently specific to be used for immunocytology. They recognized a subset of 10 lateral neurosecretory cells in the protocerebrum that project to, and arborize and terminate in the ipsilateral corpus cardiacum. They also reacted with bilateral neurons in each of the thoracic and abdominal neuromeres, a single dorsal unpaired median neuron in the suboesophageal ganglion, an interneuron in each optic lobe, and other neurons at the base of the optic lobe, in the tritocerebrum and deutocerebrum. The presence of corazonin in the abdominal neurons and the lateral neurosecretory cells was confirmed by HPLC fractionation of extracts of the abdominal ganglia, brains and retrocerebral complexes, followed by determination of corazonin by ELISA, which revealed in each tissue a single immunoreactive peak co-eluting with corazonin in two different HPLC systems. Antisera obtained after the first three booster injections recognized a large number of neuroendocrine cells and neurons in the brain and the abdominal nerve cord. However, the sera from the two rabbits reacted largely with different cells, indicating that the majority of this immunoreactivity was due to cross-reactivity. These results indicate that the production of highly specific antisera to some neuropeptides may require a considerable number of booster injections.

Prosomatostatin processing in Neuro2A cells. Role of beta-turn structure in the vicinity of the Arg-Lys cleavage site

Proline residues located near the processing sites of human prosomatostatin were previously shown to be important for cleavage of the precursor into somatostatin 28 and somatostatin 14 [Gomez, S., Boileau, G., Zollinger, L., Nault, C., Rholam, M. & Cohen, P. (1989) EMBO J. 8, 2911-2916]. In this study, site-directed and regional mutagenesis of the human prosomatostatin cDNA coupled with analysis by circular-dichroism and Fourier-transform-infrared spectroscopies of the native and mutated peptide sequences were used to elucidate the role of proline in proteolytic processing. Glycine was substituted for proline a position -5 and the beta-turn-promoting sequence Pro-Arg-Glu-Arg, located near the somatostatin-14 cleavage site and predicted to form a beta-turn structure, was replaced by Ser-Ser-Asn-Arg or Tyr-Lys-Gly-Arg, which have been shown by X-ray diffraction to form beta turns in other proteins. Analysis of the prosomatostatin-derived peptides produced by expression of the mutated cDNA species in Neuro2A cells indicated that while Pro-5-->Ala abolished cleavage at the dibasic site, the formation of mutants [Gly-5] prosomatostatin, [Ser-5, Ser-4, Arg-3] prosomatostatin and [Tyr-5, Lys-4, Gly-3] prosomatostatin did not affect cleavage at the dibasic site but produced modifications in both the relative proportions of the generated hormones and in precursor processing efficiency. Moreover, spectroscopical analysis showed that whereas these substitutions did not modify the presence of a beta turn structure in the corresponding peptide sequences, replacement of Pro-5-->Ala resulted in a dramatic increase in alpha-helix accompanied by the significant decrease of other structures including beta turn. The data support the hypothesis that the proline residue near the processing site for somatostatin-14 production is an important structural feature for conferring on the cleavage domain the adequate conformation for accessibility to processing enzymes and permitting production of equivalent amounts of both hormones.

Analysis of proinsulin and its conversion products by reversed-phase high-performance liquid chromatography

Proinsulin is synthesized in the beta-cells of the endocrine pancreas, one of the four cell types found in the islets of Langerhans. Specific enzymatic cleavage of proinsulin results in the formation of equimolar amounts of insulin and C-peptide, via several intermediate split-proinsulin forms. Most mammals produce a single insulin, but in rodents two non-allelic insulin genes are expressed. There is an inverse ratio between the two insulins in rats and mice, the reason for this being unknown. It has been suggested that differences in transcription, translation (biosynthesis) and/or posttranslational processes (enzymatic conversion, intracellular degradation) could be possible explanations. Elevated amounts of proinsulin-immunoreactive material (PIM) have been described to occur in various conditions/diseases, suggesting alterations in beta-cell function, but the composition of the secreted PIM (intact proinsulin or its intermediates) has been incompletely determined. Studies of the biosynthesis of proinsulins and their conversion with the purpose of revealing some of these points depend on accessible reversed-phase high-performance liquid chromatographic (RP-HPLC) analyses capable of separating all the relevant, closely related polypeptides involved. This review will deal with the optimization of the RP-HPLC separations as well as sample preparation and recovery. Applications of the selected methods in the study of proinsulin biosynthesis and its conversion will also be presented.

Glucocorticoid effects on the molecular forms of adrenocorticotrophic hormone secreted by cultures of rat anterior pituitary cell monolayers

The effects of glucocorticoids and corticotrophin-releasing factor (CRF) on the release of various molecular forms of adrenocorticotrophic hormone (ACTH) have been investigated in primary cultures of rat anterior pituitary. The rat cells responded to a 30 min challenge with CRF by secreting increased amounts of ACTH, as assessed both by bioassay, using rat adrenocortical cells, and by radioimmunoassay. Inclusion of a synthetic glucocorticoid, such as dexamethasone (DEX), in the incubation for 5 min prior to, and during the CRF challenge, had no effect on the response as measured by radioimmunoassay. Bioassay, however, indicated profound suppression of the response to CRF. This discrepancy between ACTH immuno- and bioactivity was investigated by fractionating the immunoreactive ACTH species using high-performance liquid chromatography. The lower molecular weight (<15kd) forms (ACTH(1-39) , phosphorylated ACTH(1-39) and glycosylated ACTH(1±39) ) were separated from higher molecular weight (>15kd) forms (i.e. ACTH biosynthetic intermediate and proopiomelanocortin) using C-18 Sep-Pak. The lower molecular weight molecules were further resolved into glycosylated and non-glycosylated ACTH, using an acetonitrile gradient high-performance liquid chromatography with trifluoroacetic acid as an ion-pairer. Neither the proportion of low molecular weight forms of ACTH, nor that of glycosylated ACTH(1-39) secreted in response to CRF, were affected by DEX. Further fractionation of non-glycosylated ACTH, also using acetonitrile gradient high-performance liquid chromatography but with heptafluorobutyric acid as the ion-pairer, yielded peaks corresponding to phosphorylated and non-phosphorylated ACTH(1-39) . DEX significantly increased the proportion of phosphorylated ACTH secreted in response to CRF by 18%. An additional effect of DEX was revealed when Sep-Pak extracts were treated with alkaline phosphatase, prior to analysis. After dephosphorylation, it became clear that the peptides released by CRF-stimulated cells were different if DEX was present in the medium. The peptide released in the presence of DEX (ACTH-S) had a slightly, but consistently, different retention time on high-performance liquid chromatography and very little biological activity. Antibody cross-reactivity studies suggested that ACTH-S was modified in the 1-24 region of the peptide. It is concluded that challenge of anterior pituitary cells in primary culture with CRF, following 5 min previous exposure to DEX, results in a molecular change. The consequence of this is that ACTH immunoreactivity is released, but the molecule has reduced biological activity. This may be part of the mechanism by which fast feedback inhibition of ACTH secretion is effected.

Purification of cationic cystine-rich peptides from rat bone marrow. Primary structures and biological activity of the rat corticostatin family of peptides

Seven cationic, cystine-rich peptides of 29 to 32 amino acid residues have been purified from extracts of rat bone marrow (R-1, R-1a, R-1b, R-2, R-3, R-4 and R-5). Structural analysis clearly indicated that all seven peptides belong to the corticostatin/defensin family of leukocyte-derived peptides known to participate in oxygen-independent killing of phagocytosed bacteria. For R-1 to R-5, six cysteine residues were found at characteristic and highly conserved positions. R-1a and R-1b were partially characterized and appear to be structural variants of R-1. Aside from the conserved cysteines, there is a remarkable degree of structural diversity evident within the sequences of those members of the corticostatin/defensin family characterized so far. The structures of the peptides that we have purified can be compared directly with the sequences obtained for rat defensins isolated from extracts of peritoneal neutrophils (Lehrer, Ganz and Selsted, Cell, 64 (1991) 229-230). Some discrepancies are apparent which can be explained in terms of proteolytic cleavage of several of these peptides at both amino- and carboxyl-termini. The corticostatins owe their bioactivity to their ability to compete with corticotropin for occupancy of the corticotropin receptor (Zhu, Hu, Mulay, Esch, Shimasaki and Solomon, Proc. Natl. Acad. Sci. USA, 85 (1988) 592-596). The potency of these peptides can be expressed in terms of their capacity to inhibit the steroidogenic response of isolated rat adrenocrotical cells half-maximally stimulated by corticotropin (i.e., at the ED50 concentration for corticotropin in this assay, namely 33 pM). In this assay, the rat peptides R-1, R-2 and R-3 were shown to be inactive. In contrast, the more cationic peptides R-4 and R-5 were found to inhibit steroidogenesis. R-4 was somewhat less active than rabbit corticostatin (IC50 25 nM) showing an IC50 value of 50 nM. R-5 appeared to be significantly less potent than R-4. The lower yield of R-5 precluded an accurate estimate of the corticostatic potency of this peptide. R-4 differs in structure from R-5 in having an arginine to serine substitution at position 7. It can be concluded that an arginine at this position accounts, at least in part, for the corticostatic activity of R-4.(ABSTRACT TRUNCATED AT 400 WORDS)

ACTH-like peptides in postimplantation mouse embryos: a possible role in myoblast proliferation and muscle histogenesis

ACTH and related peptides are mitogens for certain mesodermal cell types such as adrenocortical cells, T-lymphocytes, and skeletal myoblasts. In order to postulate a possible physiological role for these peptides in skeletal muscle histogenesis, it is necessary to establish whether they are present in muscle forming anlagens of postimplantation mouse embryos. By radioimmunoassay and immunofluorescence with antibodies specific for ACTH, we have detected these peptides in many areas of mouse embryos including neural tube, limb buds, eye lens, and myotomal muscles. During fetal development, immunoreactivity decreased in muscle tissue and appeared in visceral ganglia. Furthermore, primary myotubes or C2C12 myotubes, but not muscle or 3T3 fibroblasts, release significant levels of ACTH immunoreactive peptides into the culture medium. Using a microassay for mitogen production, primary myotubes or C2C12 myotubes, but not other mesodermal cells (with the exception of dermal fibroblasts) were shown to release factors into the medium which support myoblast proliferation. Neutralizing antibodies against ACTH inhibit myoblast but not fibroblast proliferation in a dose-dependent fashion. Based on these results, we propose that myotube-derived mitogens (including ACTH-like peptides) promote the proliferation of surrounding myoblast during muscle histogenesis in vivo.

Plasmatic somatostatin as a marker of positive symptoms of schizophrenia

1. Somatostatin displays a regulatory function on several aminergic neurotransmitters, including dopamine. In addition, decreased CSF levels of the peptide has been found in Schizophrenia and other neuropsychiatric disorders. 2. In the present work, we have investigated levels of plasmatic somatostatin in a sample of 50 schizophrenic patients compared with a normal control group. 3. Somatostatin was increased in the patient group (p less than 0.01) as a whole but statistical analysis revealed that the increase was associated with the presence of positive symptoms (Factorial Analysis) with a significant correlation, specially with delusion and hallucination scores in the Andreasen rating scales.