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S A St-Pierre

Publications and source records attributed to S A St-Pierre.

14 recordsLinked to original sources
PubMed2001

Biological activities of glucagon-like peptide-1 analogues in vitro and in vivo.

Studies support a role for glucagon-like peptide 1 (GLP-1) as a potential treatment for diabetes. However, since GLP-1 is rapidly degraded in the circulation by cleavage at Ala(2), its clinical application is limited. Hence, understanding the structure-activity of GLP-1 may lead to the development of more stable and potent analogues. In this study, we investigated GLP-1 analogues including those with N-, C-, and midchain modifications and a series of secretin-class chimeric peptides. Peptides were analyzed in CHO cells expressing the hGLP-1 receptor (R7 cells), and in vivo oral glucose tolerance tests (OGTTs) were performed after injection of the peptides in normal and diabetic (db/db) mice. [D-Ala(2)]GLP-1 and [Gly(2)]GLP-1 showed normal or relatively lower receptor binding and cAMP activation but exerted markedly enhanced abilities to reduce the glycemic response to an OGTT in vivo. Improved biological effectiveness of [D-Ala(2)]GLP-1 was also observed in diabetic db/db mice. Similarly, improved biological activity of acetyl- and hexenoic-His(1)-GLP-1, glucagon((1-5)-, glucagon((1-10))-, PACAP(1-5)-, VIP(1-5)-, and secretin((1-10))-GLP-1 was observed, despite normal or lower receptor binding and activation in vitro. [Ala(8/11/12/16)] substitutions also increased biological activity in vivo over wtGLP-1, while C-terminal truncation of 4-12 amino acids abolished receptor binding and biological activity. All other modified peptides examined showed normal or decreased activity in vitro and in vivo. These results indicate that specific N- and midchain modifications to GLP-1 can increase its potency in vivo. Specifically, linkage of acyl-chains to the alpha-amino group of His(1) and replacement of Ala(2) result in significantly increased biological effects of GLP-1 in vivo, likely due to decreased degradation rather than enhanced receptor interactions. Replacement of certain residues in the midchain of GLP-1 also augment biological activity.

Amino Acid Sequence↗
PubMed2000

Micellar electrokinetic chromatography separations of dynorphin peptide analogs.

Prodynorphin is a precursor that has multiple cleavage sites to release various dynorphin opioid peptides. The dynorphin analogs used in this study have 18 amino acid residues. A series of dynorphin-like peptides, differing by a single residue (alanine substitution) were assembled by Fmoc solid-phase procedures and purified by preparative high performance liquid chromatography (HPLC). Separation of the Ala-scan dynorphin analogs was investigated by micellar electrokinetic chromatography (MEKC) employing anionic, cationic and zwitterionic surfactants. The role of electrostatic and hydrophobic forces in analyte-surfactant interactions is discussed with respect to the observed elution patterns. Separation of all dynorphin analogs by MEKC using a zwitterionic surfactant shows this technique to be powerful for separating closely related peptide species. It also demonstrates the potential for using MEKC for the prescreening of peptide libraries to determine their biological activity toward specific receptors. Results from the separation of dynorphin analogs by free solution and ion-pairing capillary electrophoresis are also presented.

Amino Acid Sequence↗
PubMed1999

Cloning and preliminary pharmacological characterization of the anaphylatoxin C5a receptor in the rabbit.

1 The rabbit receptor for C5a was cloned from a genomic library and found to be 79.5% identical to the human homologue, the highest degree of similarity found so far in nonprimate laboratory animals. 2 The rabbit C5a receptor stably expressed in RBL cells binds human 125I-C5a (2 nM). Unlabelled C5a and the C-terminal analogue N-acetyl-Tyr-Ser-Phe-Lys-Pro-Met-Pro-Leu-D-Ala-Arg (Ac-YSFKPMPLaR) were found to be competitors of that binding, the peptide analogue retaining approximately 0.1% of the affinity of human C5a. 3 The order of potency human C5a>Ac-YSFKPMPLaR was conserved in bioassays based on rabbits (relaxation of the isolated portal vein and pulmonary artery; acute in vivo neutropenia), but with a decreasing potency gap between the two compounds, a likely consequence of the resistance to peptidases of the analogue. 4 The molecular definition of the rabbit C5a receptor evidenced a high preservation degree of sequence and pharmacologic properties relative to the human ortholog receptor, thus defining a set of molecular tools for the investigation of the role of C5a in physiologic and pathologic models based on the rabbit (e.g. atherosclerosis, inflammation).

Amino Acid Sequence↗
PubMed1991

Mimicking the membrane-mediated conformation of dynorphin A-(1-13)-peptide: circular dichroism and nuclear magnetic resonance studies in methanolic solution.

The structural requirements for the binding of dynorphin to the kappa-opioid receptor are of profound clinical interest in the search for a powerful nonaddictive analgesic. These requirements are thought to be met by the membrane-mediated conformation of the opioid peptide dynorphin A-(1-13)-peptide, Tyr1-Gly2-Gly3-Phe4-Leu5-Arg6-Arg7-Ile8-Arg9-Pro10- Lys11-Leu12-Lys13. Schwyzer has proposed an essentially alpha-helical membrane-mediated conformation of the 13 amino acid peptide [Schwyzer, R. (1986) Biochemistry 25, 4281-4286]. In the present study, circular dichroism (CD) studies on dynorphin A-(1-13)-peptide bound to an anionic phospholipid signified negligible helical content of the peptide. CD studies also demonstrated that the aqueous-membraneous interphase may be mimicked by methanol. The 500- and 620-MHz 1H nuclear magnetic resonance (NMR) spectra of dynorphin A-(1-13)-peptide in methanolic solution were sequence-specifically assigned with the aid of correlated spectroscopy (COSY), double-quantum filtered phase-sensitive COSY (DQF-COSY), relayed COSY (RELAY), and nuclear Overhauser enhancement spectroscopy (NOESY). 2-D CAMELSPIN/ROESY experiments indicated that at least the part of the molecule from Arg7 to Arg9 was in an extended or beta-strand conformation, which agreed with deuterium-exchange and temperature-dependence studies of the amide protons and analysis of the vicinal spin-spin coupling constants 3JHN alpha. The results clearly demonstrated the absence of extensive alpha-helix formation. chi 1 rotamer analysis of the 3J alpha beta demonstrated no preferred side-chain conformations.

Cell Membrane↗
PubMed1981

Synthetic model for two-stranded alpha-helical coiled-coils. Design, synthesis, and characterization of an 86-residue analog of tropomyosin.

A 43-residue peptide analog of tropomyosin Ac-AB4C-OH (A = Lys-Cys-Ala-Glu-Leu-Glu-Gly, B = Lys-Leu-Glu-Ala-Leu-Glu-Gly, C = Lys-Leu-Glu-Ala-Leu-Glu-Gly-Lys) was synthesized. The 86-residue disulfide-linked dimer was prepared by air oxidation of the single cysteine residue in the NH2-terminal Fragment A of the 43-residue peptide to provide a two-stranded alpha-helical coiled-coil of defined molecular weight with the chains in-register and parallel. The physical properties of the 86-residue dimer were determined and compared to CM-tropomyosin and sequential polyheptapeptides. The stabilizing effect of the disulfide bridge in the synthetic dimer was indicated by the shift in the transition of the thermal unfolding profile (t 1/2) of +6.5 degrees C from 72.5 degrees C for the reduced sample to 79 degrees C for the oxidized sample. The 86-residue disulfide-linked dimer maintains 65% of the original helicity at 65 degrees C, and the polyheptapeptide [Leu-Glu-Serr-Leu-Glu-Ser-Lys]n of 9,500 daltons in denaturant maintains 75% helicity at 65 degrees C, whereas CM-tropomyosin is completely denatured at this temperature. These results show a shift in the transition of the thermal unfolding profile (t 1/2) of greater than 39 degrees C for the above two synthetic peptides relative to CM-tropomyosin. The polyheptapeptide [Leu-Glu-Ser-Leu-Glu-Ser-Lys]n maintains 95% of the original helicity in 3 M urea, whereas 50% remains in CM-tropomyosin. Comparison of the CD spectra of three polyheptapeptides, [Leu-Glu-Ser-Leu-Glu-Ser-Lys]n, [Ala-Glu-Ser-Leu-Glu-Ser-Lys]n, and [Ala-Glu-Ser-Ala-Glu-Ser-Lys]n showed that the ellipticities increased as the size of the hydrophobic side chains increased in the positions responsible for the formation and stabilization of the coiled-coil. That substituting residues in the outer positions of the coiled-coil can affect alpha-helix stabilization is shown by comparing the CD spectra of three polymers [Leu-Glu-Ser-Leu-Glu-Ser-Lys]n, [Leu-Glu-Ser(Ac)-Leu-Glu-Ser(Ac)-Lys]n, and [Leu-Glu-Ala-Leu-Glu-Ala-Lys]n.

Amino Acid Sequence↗
PubMed1979

Receptors for bradykinin and kallidin.

In order to establish if bradykinin (BK) and Lys-bradykinin (Lys-BK), alias kallidin, act on the same or on different receptors, experiments were performed on strips of cat terminal ileum and of rabbit aorta. The first preparation contains receptor B2 and the second has the newly identified receptor B1. The criterion used for establishing the identity of receptors for BK and Lys-BK in the cat ileum (receptor B2) was desensitization, while for the rabbit aorta (receptor B1) we measured the apparent affinity (pA2 value) of a competitive and specific inhibitor of BK, [Leu-OMe3,des-Arg9]-BK. Since cat ileum desensitized with BK or Lys-BK shows a significant decrease or a complete disappearance of the response to the other agent, while maintaining full sensitivity for histamine, and since the pA2 values of [Leu-OMe8,des-Arg9]-BK against BK and Lys-BK are identical in the rabbit aorta, we conclude that the two kinins act on the same types of receptors.

Animals↗
PubMed1979

Structure-activity studies of [des-Arg9]-bradykinin on the B1 receptor of the rabbit aorta.

Eight L-alanine analogues of [des-Arg9]-bradykinin and a few other compounds substituted in positions 5 and (or) 8 have been tested on rabbit aortic strips in order to identify the group(s) responsible for binding and (or) stimulation of the B1 receptor. The results obtained with the L-Ala series have shown that the active group is located at the C-terminal end and it is probably Phe8, while the middle part and the N-terminal end of the peptide molecule are primarily involved in binding the agonist to the receptor. An aromatic ring is required in position 8 for activation of receptors, since the elimination or aromaticity (as in [Leu8,des-Arg9]-bradykinin and in [cyclohexylalanine8,des-Arg9]-bradykinin) brings about pure and competitive antagonists. Some compounds exert an angiotensin-like effect when applied at very high concentrations.

Alanine↗
PubMed1978

Photoaffinity labeling of the angiotensin II receptor. 1. Synthesis and biological activities of the labeling peptides.

The synthesis and biological activities of analogues of the peptide hormone angiotensin II (AT) for use in photoaffinity labeling and receptor isolation are described. In the modified sequence of AT, Sar-Arg-Val-Tyr-Val-His-Pro-Phe, the aromatic residues Tyr and Phe have been either singly or simultaneously replaced by L-4'-nitrophenylalanine, L-4'-amino-3',5'-diiodophenylalanine, L-4'-aminophenylalanine, L-4'-diazoniumphenylalanine, and L-4'-azidophenylalanine. The peptides were assembled by solid-phase synthesis and the functional groups in position 4 and/or 8 chemically modified. Radioactivity was introduced by catalytic tritiation of the iodinated peptides to form the photolabeling precursors containing L-4'-amino-3',5'-diiodophenylalanine. On rabbit aorta the AT analogues substituted in position 4 showed poor affinities (0--15%), in position 8 high relative affinities (16--118%), and in position 4 and 8 additive effects of simultaneous substitutions. It is also shown that the new Boc derivative of L-4'-amino-3',5'-diiodophenylalanine can be used in peptide synthesis without side-chain protection.

Affinity Labels↗
PubMed1978

Synthesis of peptides by the solid-phase method. III. Bradykinin: fragments and analogs.

The natural sequence of bradykinin (BK) and 55 fragments or analogs of this peptide were perpared via the solid-phase method. The peptides were purified using ion-exchange (O-carboxymethyl(CM) and partition (Sephadex G-25) chromatography. The purity of each peptide was established by paper and thin-layer chromatography, paper electrophoresis, amino acid analysis, and biological assays. The compounds were tested in anesthetized rats (tested in vivo) and in two smooth-muscle preparations (rabbit aorta strip, cat ileum strip) in which BK produces contraction by stimulating specific receptors of different types. Some of the new peptides are interesting in that they either resist pulmonary inactivation, or are more potent than BK itself, or antagonize the myotropic effect of BK in rabbit aorta strips.

Animals↗
PubMed1977

The solution synthesis of sequential polypeptides as models for the double-stranded coiled-coil structure of tropomyosin.

The syntheses of the three sequential polyheptapeptides [L-Leu-L-Glu-L-Ser-L-Leu-L-Glu-L-Ser-L-Lys)n, [L-Ala-L-Glu-L-Ser-L-Ala-L-Glu-L-Ser-L-Lys]n, [L-Ala-L-Glu-L-Ser-L-Leu-L-Glu-L-Ser-L-Lys]n and of the polytetrapeptide [L-Leu-L-Glu-L-Ser-L-Lys]n by solution methods are described. The syntheses were performed using a combination of a modified mixed carbonic anhydride method and an active ester coupling method. The N-hydroxysuccinimide ester was used as the active group for the polymerization of the monomers. These compounds were prepared as model polypeptides for the coiled-coil structure of tropomyosin.

Amino Acid Sequence↗