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Hruby VJ, Cai M. Design of peptide and peptidomimetic ligands with novel pharmacological activity profiles. Annu Rev Pharmacol Toxicol 2013; 53:557-80. [PMID: 23294313 DOI: 10.1146/annurev-pharmtox-010510-100456] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Peptide hormones and neurotransmitters are of central importance in most aspects of intercellular communication and are involved in virtually all degenerative diseases. In this review, we discuss physicochemical approaches to the design of novel peptide and peptidomimetic agonists, antagonists, inverse agonists, and related compounds that have unique biological activity profiles, reduced toxic side effects, and, if desired, the ability to cross the blood-brain barrier. Designing ligands for specific biological and medical needs is emphasized, as is the close collaboration of chemists and biologists to maximize the chances for success. Special emphasis is placed on the use of conformational (ϕ-ψ space) and topographical (χ space) considerations in design.
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Affiliation(s)
- Victor J Hruby
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA.
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2
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3
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Ying J, Ahn JM, Jacobsen NE, Brown MF, Hruby VJ. NMR solution structure of the glucagon antagonist [desHis1, desPhe6, Glu9]glucagon amide in the presence of perdeuterated dodecylphosphocholine micelles. Biochemistry 2003; 42:2825-35. [PMID: 12627948 DOI: 10.1021/bi026629r] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Glucagon, a 29-residue peptide hormone, plays an important role in glucose homeostasis and in diabetes mellitus. Several glucagon antagonists and agonists have been developed, but limited structural information is available to clarify the basis of their biological activity. The solution structure of the potent glucagon antagonist, [desHis1, desPhe6, Glu9]glucagon amide, was determined by homonuclear 2D NMR spectroscopy at pH 6.0 and 37 degrees C in perdeuterated dodecylphosphocholine micelles. The overall backbone root-mean-square deviation (rmsd) for the structured portion (residues 7-29, glucagon numbering) of the micelle-bound 27-residue peptide is 1.36 A for the 15 lowest-energy structures, after restrained molecular dynamics simulation. The structure consists of four regions (segment backbone rmsd in A): an unstructured N-terminal segment between residues 2 and 5 (1.68), an irregular helix between residues 7 and 14 (0.79), a hinge region between residues 15 and 18 (0.54), and a well-defined alpha-helix between residues 19 and 29 (0.33). The two helices form an L-shaped structure with an angle of about 90 degrees between the helix axes. There is an extended hydrophobic cluster, which runs along the inner surface of the L-structure and incorporates the side chains of the hydrophobic residues of each of the amphipathic helices. The outer surface contains the hydrophilic side chains, with two salt bridges (D15-R18 and R17-D21) implied from close approach of the charged groups. This result is the first clear indication of an overall tertiary fold for a glucagon analogue in the micelle-bound state. The relationship of the two helical structural elements may have important implications for the biological activity of the glucagon antagonist.
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Affiliation(s)
- Jinfa Ying
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
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4
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Abstract
The most ubiquitous mode for controlling and modulating cellular function, intercellular communication, immune response and information-transduction pathways is through peptide-protein non-covalent interactions. Hormones, neurotransmitters, antigens, cytokines and growth factors represent key classes of such peptide ligands. These ligands might either be processed fragments of larger precursor proteins or surface segments of larger proteins. Although there are numerous exceptions, such as insulin, oxytocin and calcitonin, most ligands are not used directly as drugs, and often the most useful ligands for therapy would be analogues that act as antagonists of the native ligands. A search for systematic structure-based or ligand-based approaches to designing such ligands has been an important concern. Today, a robust strategy has been developed for the design of peptides as drugs, drug candidates and biological tools. This strategy includes structural, conformational, dynamic and topographical considerations.
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Affiliation(s)
- Victor J Hruby
- Department of Chemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, USA.
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Moens K, Berger V, Ahn JM, Van Schravendijk C, Hruby VJ, Pipeleers D, Schuit F. Assessment of the role of interstitial glucagon in the acute glucose secretory responsiveness of in situ pancreatic beta-cells. Diabetes 2002; 51:669-75. [PMID: 11872665 DOI: 10.2337/diabetes.51.3.669] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Glucagon is a potent stimulator of insulin release in the presence of a permissive glucose concentration, activating beta-cells in vitro via both glucagon- and glucagon-like peptide-1 (GLP-1)-receptors. It is still unclear whether locally released glucagon amplifies the secretory responsiveness of neighboring beta-cells in the intact pancreas. The present study investigates this question in the perfused pancreas by examining the effects of antagonists for glucagon receptors ([des-His(1),des-Phe(6),Glu(9)]glucagon-NH(2), 10 micromol/l) and GLP-1-receptors [exendin-(9-39)-NH(2), 1 micromol/l] on the insulin secretory response to glucose. The specificity of both antagonists was demonstrated by their selective interaction with glucagon-receptor signaling in rat hepatocytes and GLP-1-receptor signaling in Chinese hamster lung (CHL) fibroblasts. In purified rat beta-cells, the glucagon-receptor antagonist (10 micromol/l) inhibited the effect of 1 nmol/l glucagon upon glucose-induced insulin release by 78 plus minus 6%. In the perfused rat pancreas, neither of these antagonists inhibited the potent secretory response to 20 mmol/l glucose, although they effectively suppressed the potentiating effect of, respectively, an infusion of glucagon (1 nmol/l) or GLP-1 (1 nmol/l) on insulin release. When endogenous glucagon release was enhanced by isoproterenol (100 nmol/l), no amplification was seen in the simultaneous or subsequent insulin secretory response to glucose. It is concluded that, at least under the present selected conditions, the glucose-induced insulin release by the perfused rat pancreas seems to occur independent of an amplifying glucagon signal from neighboring alpha-cells.
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Affiliation(s)
- Karen Moens
- Diabetes Research Center, Vrije Universiteit Brussel, Brussels, Belgium
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6
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Ladouceur GH, Cook JH, Doherty EM, Schoen WR, MacDougall ML, Livingston JN. Discovery of 5-hydroxyalkyl-4-phenylpyridines as a new class of glucagon receptor antagonists. Bioorg Med Chem Lett 2002; 12:461-4. [PMID: 11814820 DOI: 10.1016/s0960-894x(01)00766-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
5-Hydroxyalkyl-4-phenylpyridines have been identified as a novel class of glucagon antagonists with potential utility for the treatment of diabetes. A lead structure with moderate activity was discovered through a high throughput screening assay. Structure-activity relationships led to the discovery of a potent antagonist, IC(50)=0.11 microM, more than 60-fold improvement over the lead structure.
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Affiliation(s)
- Gaetan H Ladouceur
- Department of Chemistry Research, Bayer Research Center, 400Morgan Lane, West Haven, CT 06516, USA.
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Chang LL, Sidler KL, Cascieri MA, de Laszlo S, Koch G, Li B, MacCoss M, Mantlo N, O'Keefe S, Pang M, Rolando A, Hagmann WK. Substituted imidazoles as glucagon receptor antagonists. Bioorg Med Chem Lett 2001; 11:2549-53. [PMID: 11549467 DOI: 10.1016/s0960-894x(01)00498-x] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
A modestly active, nonselective triarylimidazole lead was optimized for binding affinity with the human glucagon receptor. This led to the identification of a 2- and/or 4-alkyl or alkyloxy substituent on the imidazole C4-aryl group as a structural determinant for significant enhancement in binding with the glucagon receptor (e.g., 41, IC(50)=0.053 microM) and selectivity (>1000x) over p38MAP kinase in this class of compounds.
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Affiliation(s)
- L L Chang
- Department of Medicinal Chemical Research, Merck Research Laboratories, Rahway, NJ 07065, USA.
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Ahn JM, Gitu PM, Medeiros M, Swift JR, Trivedi D, Hruby VJ. A new approach to search for the bioactive conformation of glucagon: positional cyclization scanning. J Med Chem 2001; 44:3109-16. [PMID: 11543679 DOI: 10.1021/jm010091q] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In search for the bioactive conformation of glucagon, "positional cyclization scanning" was used to determine secondary structures of glucagon required for maximal interaction with the glucagon receptor. Because glucagon is flexible in nature, its bioactive conformation is not known except for an amphiphilic helical conformation at the C-terminal region. To understand the conformational requirement for the N-terminal region that appears to be essential for signal transduction, a series of glucagon analogues conformationally constrained by disulfide or lactam bridges have been designed and synthesized. The conformational restrictions via disulfide bridges between cysteine i and cysteine i + 5, or lactam bridges between lysine i and glutamic acid i + 4, were applied to induce and stabilize certain corresponding secondary structures. The results from the binding assays showed that all the cyclic analogues with disulfide bridges bound to the receptor with significantly reduced binding affinities compared to their linear counterparts. On the contrary, glucagon analogues containing lactam bridges, in particular, c[Lys(5), Glu(9)]glucagon amide (10) and c[Lys(17), Glu(21)]glucagon amide (14), demonstrated more than 7-fold increased receptor binding affinities than native glucagon. These results suggest that the bioactive conformation of glucagon may adopt a helical conformation at the N-terminal region as well as the C-terminal region, which was not evident from earlier biophysical studies of glucagon.
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Affiliation(s)
- J M Ahn
- Department of Chemistry, University of Arizona, Tucson, 85721, USA
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Ahn JM, Medeiros M, Trivedi D, Hruby VJ. Development of potent glucagon antagonists: structure-activity relationship study of glycine at position 4. THE JOURNAL OF PEPTIDE RESEARCH : OFFICIAL JOURNAL OF THE AMERICAN PEPTIDE SOCIETY 2001; 58:151-8. [PMID: 11532074 DOI: 10.1034/j.1399-3011.2001.00880.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We examined the functional role of glycine at position 4 in the potent glucagon antagonist [desHis(1), Glu(9)]glucagon amide, by substituting the L- and D-enantiomers of alanine and leucine for Gly(4) in this antagonist. The methyl and isobutyl side-chain substituents were introduced to evaluate the preference shown by the glucagon receptor, if any, for the orientation of the N-terminal residues. The L-amino acids demonstrated only slightly better receptor recognition than the D-enantiomers. These results suggest that the Gly(4) residue in glucagon antagonists may be exposed to the outside of the receptor. The enhanced binding affinities of analogs 1 and 3 compared with the parent antagonist, [desHis(1), Glu(9)]glucagon amide, may have resulted from the strengthened hydrophobic patch in the N-terminal region and/or the increased propensity for a helical conformation due to the replacement of alanine and leucine for glycine. Thus, as a result of the increased receptor binding affinities, antagonist activities of analogs 1-4 were increased 10-fold compared with the parent antagonist, [desHis(1), Glu(9)]glucagon amide. These potent glucagon antagonists have among the highest pA(2) values of any glucagon analogs reported to date.
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Affiliation(s)
- J M Ahn
- Department of Chemistry, University of Arizona, Tucson 85721, USA
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10
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Abstract
In pursuit of truncated glucagon analogues that can interact with the glucagon receptor with substantial binding affinity, 23 truncated glucagon analogues have been designed and synthesized. These truncated analogues consist of several fragments of glucagon with 11 or 12 amino acid residues (1-4), conformationally constrained analogues containing the sequence of the middle region of glucagon (5-15), and truncated analogues containing the sequence of the C-terminal region (16-23). Biological assays of these analogues showed that the truncated glucagon analogues with the sequence of the C-terminal region possess significantly better binding affinity compared to the truncated analogues with the sequence of the middle region, and these analogues (17-23) demonstrated potent antagonistic activity (pA(2) values between 6.5 and 7.5). On the basis of these results, it can be suggested that glucagon interacts with its receptor with two hydrophobic patches located in the middle and the C-terminal regions of glucagon, and both hydrophobic patches are necessary for significant receptor recognition. These two hydrophobic binding motifs, located in two different regions of glucagon, appear to be the reason why the earlier attempts to obtain truncated analogues with good binding affinity did not result in any success. Long peptide hormones such as glucagon seem to require more than one binding pocket on the receptors for maximal interaction.
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Affiliation(s)
- J M Ahn
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
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de Laszlo SE, Hacker C, Li B, Kim D, MacCoss M, Mantlo N, Pivnichny JV, Colwell L, Koch GE, Cascieri MA, Hagmann WK. Potent, orally absorbed glucagon receptor antagonists. Bioorg Med Chem Lett 1999; 9:641-6. [PMID: 10201821 DOI: 10.1016/s0960-894x(99)00081-5] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The SAR of 2-pyridyl-3,5-diaryl pyrroles, ligands of the human glucagon receptor and inhibitors of p38 kinase, were investigated. This effort resulted in the identification of 2-(4-pyridyl)-5-(4-chlorophenyl)-3-(5-bromo-2-propyloxyphenyl)pyrr ole 49 (L-168,049), a potent (Kb = 25 nM), selective antagonist of glucagon.
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Affiliation(s)
- S E de Laszlo
- Department of Medicinal Chemistry, Merck Research Laboratories, Rahway, NJ 07065, USA
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Sturm NS, Lin Y, Burley SK, Krstenansky JL, Ahn JM, Azizeh BY, Trivedi D, Hruby VJ. Structure-function studies on positions 17, 18, and 21 replacement analogues of glucagon: the importance of charged residues and salt bridges in glucagon biological activity. J Med Chem 1998; 41:2693-700. [PMID: 9667960 DOI: 10.1021/jm980084a] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We have designed and synthesized eight compounds 2-9 which incorporate various amino acid residues in positions 17, 18, and 21 of the glucagon molecule: 2, [Lys17]glucagon amide; 3, [Lys18]glucagon amide; 4, [Nle17,Lys18,Glu21]glucagon amide; 5, [Orn17,18, Glu21]glucagon amide; 6, [d-Arg17]glucagon; 7, [d-Arg18]glucagon; 8, [d-Phe17]glucagon; and 9, [d-Phe18]glucagon. Compared to glucagon (IC50 = 1.5 nM), analogues 2-9 were found to have binding affinity IC50 values (in nM) of 0.7, 4.1, 1.0, 2.0, 5.0, 25.0, 43.0, and 32.0, respectively. When these compounds were tested for their ability to stimulate adenylate cyclase (AC) activity, they were found to be full or partial agonists having maximum stimulation values of 100, 100, 100, 100, 87, 78, 94, and 100%, respectively. On the basis of the X-ray crystal structure of [Lys17,18,Glu21]glucagon amide reported here, the ability to form a salt bridge between Lys18 and Glu21 is probably key to their increased binding and second messenger activities. Among the eight analogues synthesized here, only analogue 4 preserves the ability to form a salt bridge between Lys18 and Glu21. However, since these modifications are minor they do not seem to change the amphiphilic character of the C-terminus, allowing these analogues to reach 78-100% stimulation in the adenylate cyclase assay. Biological data from analogues 6-9 supports the idea that position 18 of glucagon may influence binding only, while position 17 may influence both receptor recognition and transduction.
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Affiliation(s)
- N S Sturm
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, Howard Hughes Medical Institute, The Rockefeller University, New York, New York 10021, USA
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Recent Advances in the Development of Agents for the Treatment of Type 2 Diabetes. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 1998. [DOI: 10.1016/s0065-7743(08)61086-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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Azizeh BY, Ahn JM, Caspari R, Shenderovich MD, Trivedi D, Hruby VJ. The role of phenylalanine at position 6 in glucagon's mechanism of biological action: multiple replacement analogues of glucagon. J Med Chem 1997; 40:2555-62. [PMID: 9258362 DOI: 10.1021/jm960800d] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Extensive evidence gathered from structure-activity relationship analysis has identified and confirmed specific positions in the glucagon sequence that are important either for binding to its receptor or for signal transduction. Fifteen glucagon analogues have been designed and synthesized by incorporating structural changes in the N-terminal region of glucagon, in particular histidine-1, phenylalanine-6, and aspartic acid-9. This investigation was conducted to study the role of phenylalanine at position 6 on the glucagon mechanism of action. These glucagon analogues have been made by either deleting or substituting hydrophobic groups, hydrophilic groups, aromatic amino acids, or a D-phenylalanine residue at this position. The structures of the new analogues are as follows: [des-His1, des-Phe6, Glu9]glucagon-NH2 (1); [des-His1,Ala6,Glu9]glucagon-NH2 (2); [des-His1,Tyr6,Glu9]glucagon-NH2 (3); [des-His1,Trp6,Glu9]-glucagon-NH2 (4); [des-His1,D-Phe6,Glu9]glucagon-NH2 (5); [des-His1,Nle6,Glu9]glucagon-NH2 (6); [des-His1,Asp6,Glu9]glucagon-NH2 (7); [des-His1,des-Gly4,Glu9]glucagon-NH2 (8); [desPhe6,-Glu9]glucagon-NH2 (9); [des-Phe6]glucagon-NH2 (10); [des-His1, des-Phe6]glucagon-NH2 (11); [des-His1, des-Phe6,Glu9]glucagon (12); [des-Phe6,Glu9]glucagon (13); [des-Phe6]glucagon (14); and [des-His1, des-Phe6]glucagon (15). The receptor binding potencies IC50 values are 48 (1), 126 (2), 40 (3), 19 (4), 100 (5), 48 (6), 2000 (7), 52 (8), 113 (9), 512 (10), 128 (11), 1000 (12), 2000 (13), 500 (14), and 200 nM (15). All analogues were found to be antagonists unable to activate the adenylate cyclase system even at concentrations as high as 10(-5) M except for analogues 6 and 8, which were found to be weak partial agonists/partial antagonists with maximum stimulation between 6-12%. In competitive inhibition experiments, all the analogues caused a right shift of the glucagon-stimulated adenylate cyclase dose-response curve. The pA2 values were 8.20 (1), 6.40 (2), 6.20 (3), 6.25 (4), 6.30 (5), 6.30 (7), 6.05 (8), 6.20 (9), 6.30 (10), 6.25 (11), 6.10 (12), 6.20 (13), 6.20 (14), and 6.35 (15).
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Affiliation(s)
- B Y Azizeh
- Department of Chemistry, University of Arizona, Tucson 85721, USA
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Sturm NS, Hutzler AM, David CS, Azizeh BY, Trivedi D, Hruby VJ. Structure-activity studies of hydrophobic amino acid replacements at positions 9, 11 and 16 of glucagon. THE JOURNAL OF PEPTIDE RESEARCH : OFFICIAL JOURNAL OF THE AMERICAN PEPTIDE SOCIETY 1997; 49:293-9. [PMID: 9176812 DOI: 10.1111/j.1399-3011.1997.tb01129.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have designed and synthesized eight compounds 2-9 which incorporate neutral, hydrophobic amino acid residues in positions 9, 11 and 16 of the glucagon molecule: (2) [desHis1, Val9. Ile11,16] glucagon amide, (3) [desHis1, Val9,11,16] glucagon amide, (4) [desHis1, Val9, Leu11,16]glucagon amide, (5) [desHis1, Nle9, Ile11,16]glucagon amide, (6) [desHis1, Nle9, Val11,16] glucagon amide, (7) [desHis1,-Nle9, Leu11,16] glucagon amide, (8) [desHis1, Val9, Leu11,16, Lys17,18, Glu21] glucagon amide and (9) [desHis1, Nle9, Leu11,16, Lys17,18, Glu21] glucagon amide. The effect of neutral, hydrophobic residues at positions 9, 11 and 16 led to good binding to the glucagon receptor. Compared to glucagon (IC50 = 1.5 nM), analogues 2-9 were found to have IC50 values of 6.0, 6.0, 11.0, 9.0, 2.5, 2.8, 6.5 and 7.0 nM, respectively. When these compounds were tested for their ability to block adenylate cyclase (AC) activity, they were found to be antagonists having no stimulation of adenyl cyclase, with pA2 values of 6.15, 6.20, 6.30, 7.25, 6.10, 7.30, 6.25 and 7.25, respectively.
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Affiliation(s)
- N S Sturm
- Department of Chemistry, University of Arizona, Tucson, USA
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Azizeh BY, Van Tine BA, Trivedi D, Hruby VJ. Pure glucagon antagonists: biological activities and cAMP accumulation using phosphodiesterase inhibitors. Peptides 1997; 18:633-41. [PMID: 9213355 DOI: 10.1016/s0196-9781(97)00131-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Five new glucagon analogues have been designed, synthesized, characterized and their biological activities tested. The investigation was centered on modifications in the N-terminal region in particular, residues at Thr5, Phe6 and Tyr10 positions, with the goal of obtaining pure glucagon antagonists in our newly developed high sensitivity cAMP accumulation assay. The structures of the designed compounds are: [des-His1, des-Phe6, Glu9] glucagon-NH2 (1); [des-His1, des-Phe6, Glu9, Phe10]glucagon-NH2 (2); [des-His1, Tyr5, des-Phe6, Glu9]glucagon-NH2 (3); [des-His1, Phe5, des-Phe6, Glu9]glucagon-NH2 (4) and [des-His1, des-Phe6, Glu9, D-Arg18]glucagon-NH2 (5). The binding potencies IC50 values in (nM) were 48.0, 27.4, 26.0, 20.0 and 416.0, respectively. All of these analogues when tested in the classical adenylate cyclase assay demonstrate antagonist properties, and in competition experiments, all caused a rightward-shift of the glucagon stimulated adenylate cyclase dose-response curve. The pA2 values for these analogues were 8.20 (1); 6.25 (2); 6.10 (3); 6.25 (4); and 6.08 (5), respectively. A newly revised assay has been developed to determine the intracellular cAMP accumulation levels in hepatocytes at the highest possible sensitivity. Four of the five glucagon analogues in this report (analogues 1, 2, 4 and 5), did not activate the adenylate cyclase in the presence of Rolipram up to a maximal physiological concentration of 1 microM, and thus are pure antagonists.
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Affiliation(s)
- B Y Azizeh
- Department of Chemistry, University of Arizona, Tucson 85721, USA
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Azizeh BY, Shenderovich MD, Trivedi D, Li G, Sturm NS, Hruby VJ. Topographical amino acid substitution in position 10 of glucagon leads to antagonists/partial agonists with greater binding differences. J Med Chem 1996; 39:2449-55. [PMID: 8691441 DOI: 10.1021/jm960130b] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The role of position 10 in the beta-turn region of glucagon was investigated by substituting chiral constrained amino acids and other modifications in the N-terminal region. A series of glucagon analogues have been designed and synthesized by incorporating beta-methylphenylalanine isomers (2S,3S, 2S,3R, 2R,3R, and 2R,3S) at position 10 in order to explore the structural and topographical requirements of the glucagon receptor, and, in addition, utilizing previous studies which indicated that antagonism could be enhanced by modifications (des-His1, Glu9) and a bulky group at position 5. The structures of the new analogues are as follows: [des-His1,-Tyr5,Glu9]glucagon-NH2 (II), [des-His1,Tyr5,Glu9,Phe10]glucagon-NH2 (III), [des-His1,Tyr5,Glu9,-Ala10]glucagon-NH2 (IV), [des-His1,Tyr5,Glu9,(2S,3R)-beta-MePhe10]glucagon-NH2 (V), [des-His1,-Tyr5,Glu9,(2S,3S)-beta-MePhe10]glucagon-NH2 (VI), [des-His1,Tyr5,Glu9,D-Tyr10]glucagon-NH2 (VII), [des-His1,Tyr5,Glu9,D-Phe10]glucagon-NH2 (VIII), [des-His1,Tyr5,Glu9,D-Ala10]glucagon-NH2 (IX), [des-His1,Tyr5,Glu9,(2R,3R)-beta-MePhe10]glucagon-NH2 (X), and [des-His1,Tyr5,Glu9,(2R,3S)-beta-MePhe10]glucagon-NH2 (XI). These analogues led to dramatically different changes in in vitro binding affinities for glucagon receptors. Their receptor binding potencies IC50 values (nM) are 2.3 (II), 4.1 (III), 395.0 (IV), 10.0 (V), 170.0 (VI), 74.0 (VII), 34.5 (VIII), 510.0 (IX), 120.0 (X), and 180.0 (XI). Analogues II, III, V, VI, and XI were found to be weak partial agonists/partial antagonists with maximum stimulation between 5%-9%, while the other compounds (IV and VII-X) were antagonists unable to activate the adenylate cyclase system even at concentrations as high as 10(-5) M. In competition experiments, all of the analogues caused a right shift of the glucagon-stimulated adenylate cyclase dose-response curve. The pA2 values were 6.60 (II), 6.85 (III), 6.20 (IV), 6.20 (V), 6.10 (VI), 6.50 (VII), 6.20 (VIII), 5.85 (IX), 6.20 (X), and 6.00 (XI). Putative topographical requirements of the glucagon receptor for the aromatic side chain conformation in position 10 of glucagon antagonists are discussed.
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Affiliation(s)
- B Y Azizeh
- Department of Chemistry, University of Arizona, Tucson 85721, USA
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