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C Lazure

Publications and source records attributed to C Lazure.

At least 91 records · Page 5Linked to original sources
PubMed1989

Functional diversity of bioactive peptides in the nervous system itself: "how the brain may understand".

The interactions involving cells of the nervous system are a complex form of intercellular communication. Biosynthesis of peptide hormones or active neuropeptides is generally through a precursor which provides increased product choices as a function of the processing pathway. Proteolytic processing as well as other molecular modifications lead to a wide range of mature products which may vary in different tissues even though they are derived from the same precursor. Also the same neuropeptide may exhibit different bioactivities for different target cells. Finally, by means of collective packaging in secretory organelles, a cell may be able by synergism to further broaden its biologic effects. In these ways, what is seen as added complication in the CNS, may be from the point of view of the cell, a successful attempt to increase its survival ability to adapt and influence its bioenvironment.

Animals↗
PubMed1989

Melanin concentrating hormone. V. Isolation and characterization of alpha-melanocyte-stimulating hormone from frog pituitary glands.

The structure of alpha-melanocyte-stimulating hormone (alpha-MSH) has been determined in the pars intermedia of the frog Rana ridibunda. Pulse-chase labeling of frog neurointermediate lobes with selective amino acids revealed that the composition of frog alpha-MSH is similar to that of alpha-MSH from all mammalian species yet studied. Tryptic mapping of nexly synthetized alpha-MSH generated two fragments with the following amino acid composition: (T1) Trp, Pro, Lys, Gly, Val and (T2) Tyr, Arg, Phe, His, Ser, Glu. Concurrently, alpha-MSH was purified from 100 neurointermediate lobes to apparent homogeneity by reverse-phase HPLC. The sequence of the peptide determined by automated Edman degradation was Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val. The structure of frog alpha-MSH is thus identical to mammalian des-N alpha-acetyl alpha-MSH and differs from the sequence of toad (Xenopus laevis) alpha-MSH only by the first residue (Ser instead of Ala). These results confirm that the sequence of alpha-MSH has been highly preserved during evolution.

Amino Acid Sequence↗
PubMed1989

The cDNA structure of rat plasma kallikrein.

From a liver cDNA library we have isolated and characterized the cDNA encoding rat plasma kallikrein. The cDNA structure contains 2,456 nucleotides with a 2,082-nucleotide-long open reading frame. Protein sequence data suggest that the signal peptide is 19 amino acids long. This results in a mature plasma prekallikrein containing 619 amino acids. Determination of tissue distributions using Northern blot analysis (3.0-kb transcript) and the polymerase chain-reaction methodology on RNA preparations demonstrated that in the rat the liver is the main source of this enzyme. Southern blots suggested the presence of a single gene coding for rat plasma kallikrein. Finally, although Southern blots revealed a homologous gene in mouse, the mRNA corresponding to the mouse hepatic proteinase is barely detectable on Northern blots, suggesting inefficient transcription or high turnover of the mRNA in this species.

Amino Acid Sequence↗
PubMed1989

cDNA sequence of neuroendocrine protein 7B2 expressed in beta cell tumors of transgenic mice.

The cDNA for a widely distributed neuroendocrine protein called 7B2 has been cloned from beta cell tumors of transgenic mice and sequenced. As deduced from the cDNA sequence, 7B2 is a secretory protein of 186 amino acids, nearly identical to its human and porcine homologs. The presence of several pairs of basic residues in the carboxyl terminal portion of the protein suggests that 7B2 can undergo proteolytic maturation in secretory granules and thus generate potential bioactive peptides. 7B2 mRNA is about 1.5 kilobase long and is apparently transcribed from a single gene per haploid genome. The use of tissue-specific promoters to express oncogenes in rare cell types of transgenic mice is a powerful tool for immortalization and expansion of these cells, and it facilitates the isolation and the study of rare proteins such as 7B2.

Adenoma, Islet Cell↗
PubMed1989

Ostrich MSEL-neurophysin belongs to the class of two-domain "big" neurophysin as indicated by complete amino acid sequence of the neurophysin/copeptin.

Mammalian neurohypophyseal hormones, oxytocin and vasopressin, are known to be synthesized as part of two larger precursors containing, respectively, a VLDV-neurophysin and a MSEL-neurophysin together with its associated glycopeptide. Starting from ostrich neurohypophyses, a "big" neurophysin was isolated and chemically characterized. Following sequence determination of the CNBr-derived fragments and of peptides obtained from trypsin and V8-protease digestion of the oxidized protein, this "big" neurophysin was found to contain an MSEL-neurophysin moiety (94 residues) still covalently associated with the COOH-terminal glycopeptide (38 residues, copeptin). This study demonstrates that the ostrich MSEL-neurophysin sequence closely resembles all known MSEL-neurophysin sequences and that, furthermore, it does not contain the single amino acid insertion shown previously in the ostrich VLDV-neurophysin. It is also shown that the stretch of amino acids, linking the MSEL-neurophysin and the copeptin, is clearly different from its mammalian homologues and lacks the Arg residue normally recognized by the cleaving enzyme. This study also demonstrates that the ostrich copeptin is more closely related to the amphibian copeptin sequence than to its mammalian homologue, leading to the hypothesis that two families of copeptin molecules might exist. Thus, the ostrich MSEL-neurophysin-copeptin molecule is the first "big" neurophysin reported in birds and, together with the guinea pig and amphibian homologues, represents the third example of partial or no neurophysin-copeptin cleavage.

Amino Acid Sequence↗
PubMed1989

Aldosterone secretion inhibitory factor: a novel neuropeptide in bovine chromaffin cells.

We report the identification and the primary structure of a novel neuroendocrine peptide which inhibits aldosterone secretion. The peptide was isolated from 1.5 x 10(10) cultured bovine chromaffin cells by reversed phase and ion exchange HPLC. It is chromatographically and structurally distinct from atrial natriuretic factor (ANF), which we formely identified in chromaffin tissue. This new Aldosterone Secretion Inhibitory Factor (ASIF) is predominant in cultured chromaffin cells and cross-reacts with ANF receptor sites involved in the inhibition of aldosterone production in zona glomerulosa cells. The sequence of this 35-amino acid peptide includes the shorter fragment isolated from porcine brain confirming its neuropeptide character. ASIF might be involved in concert with ANF in the paracrine regulation of aldosterone secretion and the presence of both peptides in cultured chromaffin cells indicates that this system can be used as a model for studying natriuretic neuropeptide production.

Adrenal Glands↗
PubMed1989

Purification and primary structure of pro-aldosterone secretion inhibitory factor from bovine adrenal chromaffin cells.

This report documents the purification and the complete primary structure of bovine aldosterone secretion inhibitory factor precursor (pro-ASIF). ASIF-(1-103) contains at position 69-103 of its carboxy-terminal end the formely identified 35-amino acid biologically active form, hence confirming the endogenous character of ASIF in the adrenal medulla. Compared to atrial natriuretic factor (ANF)-related peptide precursors, bovine ASIF displays 65% homology at the carboxy-terminal while the remaining amino-terminal part shows much more variability. Bovine pro-ASIF exhibits 73% homology with porcine pro-brain natriuretic peptide (BNP), a situation reminiscent of the relationship of pro-ANF in various species. When ANF- and BNP-related COOH-termini of bovine, porcine, human, rat, and chicken are compared, it appears that bovine ASIF and porcine BNP are closely related and belong to the same family which however appears to be much more heterogenous than the ANF-related family. These results strongly suggest that bovine ASIF is encoded by a precursor gene similar to the gene of BNP but different from the one encoding ANF.

Adrenal Medulla↗
PubMed1989

[Endorphins 1989: neuroendocrine aspects].

Endorphins represent a family of brain peptides having an opioid core structure responsible for their morphinomimetic activity. We present an overview of the biology of endorphins including their origin, neuroanatomical distribution, regulatory mechanisms and interaction with opioid receptors taking neuronal cellular function in situ as our focal point of interest. Differential biochemical processing and regulatory mechanisms both at the pre- and post-translational level in the various brain areas contribute to the biochemical and functional diversity of peptides generated from common precursors in keeping with the selective needs and functions of neuronal circuits. Physiological significance requires interaction of the various endogenous ligands thus generated with appropriate receptors, sometimes located well beyond the distance of a synaptic cleft as demonstrated by the diverging ligand/receptors neurochemical topographical maps. Physiological analysis reveals a multitude of potential interactions between peptides and classical neurotransmitters in part as a result of their common subcellular location within individual synaptic vesicles but also in relation to qualitatively different post-synaptic effects and metabolism, enhancing the complexity of their potential role in neuronal function. Endorphins may contribute to major neuroendocrine systems such as analgesia, endocrine and autonomic function, mental function and behavior. Their implication in various neuropsychiatric and endocrine clinical disorders will be briefly reviewed.

Animals↗
PubMed1988

Correct processing and secretion of a human prostatic secretory protein (PSP94) in Escherichia coli.

The cDNA for PSP94, a cysteine-rich protein secreted by the human prostate, was unidirectionally digested with exonuclease III to generate deletion mutants with varying 5' ends. These were placed under the control of the lac promoter of the Bluescribe plasmid (pbs) to encode hybrid proteins containing the N terminus of beta-galactosidase (beta Gal) and various fragments of PSP94. Escherichia coli clones transformed by these constructs and expressing PSP94 epitopes were identified by radioimmunoassay of cellular and periplasmic extracts. One such clone (I-25) secreted most of its immunoreactive material into the periplasmic space. Nucleotide sequencing showed that a new consensus ribosome-binding site had been generated fortuitously, allowing expression of pre-PSP94 free of any beta Gal sequence. Periplasmic PSP94 is indistinguishable from the natural human protein, indicating correct processing and folding of this cysteine-rich protein in bacteria.

Amino Acid Sequence↗
PubMed1988

Two-dimensional immunoblotting analysis and immunocytochemical localization of the secretory polypeptide 7B2 in adrenal medulla.

The soluble proteins of bovine chromaffin granules were subjected to 2D-electrophoresis followed by immunoblotting with an antiserum against the pituitary peptide 7B2. One immunoreactive spot was visualized at a position corresponding to a molecular weight of 24,000 and to a pI of 5.2. Using peroxidase-antiperoxidase (PAP) pre-embedding immunocytochemical technique for electron microscopy, 7B2 has been localized within secretory granules with diameters of approximately 115 and 190 nm in noradrenergic and adrenergic cells respectively. These data establish that in chromaffin granules 7B2 represents a minor component of the acidic proteins which include the chromogranins A and B, secretogranin II and the enkephalin-containing peptides.

Adrenal Medulla↗
PubMed1988

The amino acid sequences of frog heart atrial natriuretic-like peptide and mammalian ANF are closely related.

Despite few studies conducted in non-mammalian species, there has been a number of reports pertaining to the occurrence of a natriuretic-like substance in lower organisms. Thus, an immunoreactive substance reacting with antibodies directed against mammalian atrial natriuretic factor has previously been detected both in heart atria and ventricles of a chordate, the frog. This substance was isolated and purified from frog heart atria and its amino acid sequence established. The sequence, Ala-Pro-Arg-Ser-Ser-Asp-Cys-Phe-Gly-Ser-Arg-Ile-Asp-Arg-Ile-Gly-Ala-Gln- Ser-Gly - Met-Gly-Cys-Gly-Arg-(Phe), is highly homologous to known mammalian ANF sequences. However, when aligned with the complete mammalian ANF precursor sequence at positions 121 to 151, it exhibits a single amino acid insertion at position 129 and other substitutions at positions 121, 125, 133, 135, 144, 147 and 148. Some evidence is also presented concerning the occurrence of uncleaved frog pronatriodilatin, the precursor form of ANF. This study represents the first report pertaining to the structure of a non-mammalian ANF and its precursor.

Amino Acid Sequence↗
PubMed1988

Amino acids of the Torpedo marmorata acetylcholine receptor alpha subunit labeled by a photoaffinity ligand for the acetylcholine binding site.

The acetylcholine-binding sites on the native, membrane-bound acetylcholine receptor from Torpedo marmorata were covalently labeled with the photoaffinity reagent [3H]-p-(dimethylamino)-benzenediazonium fluoroborate (DDF) in the presence of phencyclidine by employing an energy-transfer photolysis procedure. The alpha-chains isolated from receptor-rich membranes photolabeled in the absence or presence of carbamoylcholine were cleaved with CNBr and the radiolabeled fragments purified by high-performance liquid chromatography. Amino acid and/or sequence analysis demonstrated that the alpha-chain residues Trp-149, Tyr-190, Cys-192, and Cys-193 and an unidentified residue(s) in the segment alpha 31-105 were all labeled by the photoaffinity reagent in an agonist-protectable manner. The labeled amino acids are located within three distinct regions of the large amino-terminal hydrophilic domain of the alpha-subunit primary structure and plausibly lie in proximity to one another at the level of the acetylcholine-binding sites in the native receptor. These findings are in accord with models proposed for the transmembrane topology of the alpha-chain that assign the amino-terminal segment alpha 1-210 to the synaptic cleft. Furthermore, the results suggest that the four identified [3H]DDF-labeled residues, which are conserved in muscle and neuronal alpha-chains but not in the other subunits, may be directly involved in agonist binding.

Acetylcholine↗
PubMed1987

Chromogranin B (secretogranin I), a putative precursor of two novel pituitary peptides through processing at paired basic residues.

During the course of reversed-phase high-pressure liquid chromatography (RP-HPLC) purification of the 7B2 peptide originally isolated in our laboratory from human pituitary gland extracts, two novel peptides were identified and purified to homogeneity. The complete amino acid sequence of the first one was established in 1985 and recently found to be entirely homologous to positions 420-493 of the just published chromogranin B sequence. This peptide, denoted GAWK, could originate from chromogranin B following specific cleavage at the basic amino acids flanking both termini of GAWK. Moreover, another peptide isolated in our laboratory from the same source and denoted CCB has been discovered and its sequence is also part of the same chromogranin B molecule. Here again, this peptide, occupying positions 597-653 and located at the COOH-terminal region of chromogranin B, could derive from specific processing at basic amino acids, Arg-Lys-Lys, present at positions 594-596. In a manner reminiscent of the relationship between pancreastatin and chromogranin A, it is proposed that both GAWK and CCB are produced from chromogranin B after specific processing at basic amino acids. These data are thus in favor of a putative role of chromogranins as precursors to potentially bioactive peptides.

Amino Acid Sequence↗
PubMed1987

Bovine adrenal chromaffin granules are a site of synthesis of atrial natriuretic factor.

We have previously reported the existence of a peptide factor in the adrenal medulla which inhibits aldosterone secretion in cultured bovine zona glomerulosa cells. The acid extracts of chromaffin granules from bovine adrenal medulla were purified by a four step high performance liquid chromatography procedure. Two active fractions exhibited sequence homology with bovine atrial natriuretic factor ANF (Ser99-Tyr126) and its polypeptide precursor (Asn1-Tyr126). The occurrence of both precursor and mature forms of ANF within chromaffin granules indicates the endogenous character of ANF in the adrenal medulla and suggests the potential usefulness of cultured adrenal chromaffin cells for investigating the synthesis, maturation and secretion of atrial peptides.

Adrenal Medulla↗
PubMed1987

Chromogranin A can act as a reversible processing enzyme inhibitor. Evidence from the inhibition of the IRCM-serine protease 1 cleavage of pro-enkephalin and ACTH at pairs of basic amino acids.

Bovine parathyroid chromogranin A inhibits the cleavage of Z-Ala-Lys-Arg-AMC by either trypsin or IRCM-serine protease 1 (IRCM-SP1), a putative novel processing enzyme originally isolated from porcine pituitary anterior and neurointermediate lobes. On larger substrates, chromogranin A is a reversible competitive inhibitor of the cleavage at pairs of basic amino acids by IRCM-SP1. The substrates tested included pituitary ACTH and adrenal medulla pro-enkephalin-derived peptides such as the 8.6 kDa synenkephalin-containing precursor and peptide B. Chromogranin A is itself selectively processed by IRCM-SP1, and ACTH was shown to compete for such cleavage. These data suggest that chromogranins as a class of acidic proteins could participate in the tissue-specific processing of pro-hormones.

Adrenocorticotropic Hormone↗
PubMed1987

The propeptide Asn1-Tyr126 is the storage form of rat atrial natriuretic factor.

Granules from rat atria were isolated by differential centrifugation and by a 53% (v/v) Percoll gradient after tissue homogenization in 0.25 M-sucrose/50 mM-Na2EDTA. About 40% of the immunoreactive ANF (atrial natriuretic factor) sedimented with the atrial granules during differential centrifugations. On the Percoll gradient, two distinct bands were observed. Cell debris, mitochondria, lysosomes, myofilaments and microsomes were mostly contained in the lightest-density (rho) (1.03-1.07 g/ml) fraction, as demonstrated by electron microscopy and by enzymic markers such as lactate dehydrogenase, monoamine oxidase, cytochrome c reductase, beta-glucuronidase and acid phosphatase. Atrial granules were mostly contained in the denser (rho 1.11-1.15 g/ml) band and were only slightly contaminated by lysosomes, as shown by beta-glucuronidase activity. Analysis of the ANF content in these isolated granules by h.p.l.c., amino acid composition and sequencing demonstrated that it was only the pro-ANF [ANF-(Asn1-Tyr126)-peptide]. The precursor was present in all granules, as demonstrated by immunocytochemistry. Since hormonal propeptides usually undergo intracellular processing, and the matured peptides are subsequently stored in the secretory granules, these results indicate that the processing pathway of ANF may be different from that of other hormonal peptides.

Amino Acid Sequence↗