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Santi S, Biondi B, Cardena R, Bisello A, Schiesari R, Tomelleri S, Crisma M, Formaggio F. Helical versus Flat Bis-Ferrocenyl End-Capped Peptides: The Influence of the Molecular Skeleton on Redox Properties. Molecules 2022; 27:6128. [PMID: 36144860 PMCID: PMC9503075 DOI: 10.3390/molecules27186128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 09/07/2022] [Accepted: 09/15/2022] [Indexed: 11/30/2022] Open
Abstract
Despite the fact that peptide conjugates with a pendant ferrocenyl (Fc) have been widely investigated, bis-ferrocenyl end-capped peptides are rarely synthetized. In this paper, in addition to the full characterization of the Fc-CO-[L-Dap(Boc)]n-NH-Fc series, we report a comparison of the three series of bis-ferrocenyl homopeptides synthesized to date, to gain insights into the influence of α-amino isobutyric (Aib), 2,3-diamino propionic (Dap) and Cα,β-didehydroalanine (ΔAla) amino acids on the peptide secondary structure and on the ferrocene redox properties. The results obtained by 2D NMR analysis and X-ray crystal structures, and further supported by electrochemical data, evidence different behaviors depending on the nature of the amino acid; that is, the formation of 310-helices or fully extended (2.05-helix) structures. In these foldamers, the orientation of the carbonyl groups in the peptide helix yields a macrodipole with the positive pole on the N-terminal amino acid and the negative pole on the C-terminal amino acid, so that oxidation of the Fc moieties takes place more or less easily depending on the orientation of the macrodipole moment as the peptide chain grows. Conversely, the fully extended conformation adopted by ΔAla flat peptides neither generates a macrodipole nor affects Fc oxidation. The utilization as electrochemical and optical (Circular Dichroism) probes of the two terminal Fc groups, bound to the same peptide chain, makes it possible to study the end-to-end effects of the positive charges produced by single and double oxidations, and to evidence the presence "exciton-coupled" CD among the two intramolecularly interacting Fc groups of the L-Dap(Boc) series.
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Affiliation(s)
- Saverio Santi
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Barbara Biondi
- Institute of Biomolecular Chemistry, Padova Unit, CNR, Via Marzolo 1, 35131 Padova, Italy
| | - Roberta Cardena
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Annalisa Bisello
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Renato Schiesari
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Silvia Tomelleri
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Marco Crisma
- Institute of Biomolecular Chemistry, Padova Unit, CNR, Via Marzolo 1, 35131 Padova, Italy
| | - Fernando Formaggio
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
- Institute of Biomolecular Chemistry, Padova Unit, CNR, Via Marzolo 1, 35131 Padova, Italy
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Biondi B, Bisello A, Cardena R, Schiesari R, Facci M, Cerveson L, Rancan M, Formaggio F, Santi S. Conformational Analysis and Through‐Chain Charge Propagation in Ferrocenyl‐Conjugated Homopeptides of 2,3‐Diaminopropionic acid (Dap). Eur J Inorg Chem 2022. [DOI: 10.1002/ejic.202100966] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Barbara Biondi
- Institute of Biomolecular Chemistry, Padova Unit CNR Via Marzolo 1 35131 Padova Italy
| | - Annalisa Bisello
- Department of Chemical Sciences University of Padova Via Marzolo 1 35131 Padova Italy
| | - Roberta Cardena
- Department of Chemical Sciences University of Padova Via Marzolo 1 35131 Padova Italy
| | - Renato Schiesari
- Department of Chemical Sciences University of Padova Via Marzolo 1 35131 Padova Italy
| | - Martino Facci
- Department of Chemical Sciences University of Padova Via Marzolo 1 35131 Padova Italy
| | - Laura Cerveson
- Department of Chemical Sciences University of Padova Via Marzolo 1 35131 Padova Italy
| | - Marzio Rancan
- Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE) CNR Via Marzolo 1 35131 Padova Italy
| | - Fernando Formaggio
- Institute of Biomolecular Chemistry, Padova Unit CNR Via Marzolo 1 35131 Padova Italy
- Department of Chemical Sciences University of Padova Via Marzolo 1 35131 Padova Italy
| | - Saverio Santi
- Department of Chemical Sciences University of Padova Via Marzolo 1 35131 Padova Italy
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3
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Biondi B, Cardena R, Bisello A, Schiesari R, Cerveson L, Facci M, Rancan M, Formaggio F, Santi S. Flat, Ferrocenyl‐Conjugated Peptides: A Combined Electrochemical and Spectroscopic Study. ChemElectroChem 2021. [DOI: 10.1002/celc.202100597] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Barbara Biondi
- Institute of Biomolecular Chemistry Padova Unit, CNR via Marzolo 1 35131 Padova Italy
| | - Roberta Cardena
- Department of Chemical Sciences University of Padova via Marzolo 1 35131 Padova Italy
| | - Annalisa Bisello
- Department of Chemical Sciences University of Padova via Marzolo 1 35131 Padova Italy
| | - Renato Schiesari
- Department of Chemical Sciences University of Padova via Marzolo 1 35131 Padova Italy
| | - Laura Cerveson
- Department of Chemical Sciences University of Padova via Marzolo 1 35131 Padova Italy
| | - Martino Facci
- Department of Chemical Sciences University of Padova via Marzolo 1 35131 Padova Italy
| | - Marzio Rancan
- Institute of Condensed Matter Chemistry and Technologies for Energy (ICMATE), CNR Via Marzolo, 1 35131 Padova Italy
| | - Fernando Formaggio
- Institute of Biomolecular Chemistry Padova Unit, CNR via Marzolo 1 35131 Padova Italy
- Department of Chemical Sciences University of Padova via Marzolo 1 35131 Padova Italy
| | - Saverio Santi
- Department of Chemical Sciences University of Padova via Marzolo 1 35131 Padova Italy
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Santi S, Bisello A, Cardena R, Tomelleri S, Schiesari R, Biondi B, Crisma M, Formaggio F. Flat, C α,β -Didehydroalanine Foldamers with Ferrocene Pendants: Assessing the Role of α-Peptide Dipolar Moments. Chempluschem 2021; 86:723-730. [PMID: 33825347 DOI: 10.1002/cplu.202100072] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2021] [Revised: 03/22/2021] [Indexed: 12/28/2022]
Abstract
The foldamer field is continuously expanding as it allows to produce molecules endowed with 3D-structures and functions never observed in nature. We synthesized flat foldamers based on the natural, but non-coded, Cα,β -didehydroalanine α-amino acid, and covalently linked to them two ferrocene (Fc) moieties, as redox probes. These conjugates retain the flat and extended conformation of the 2.05 -helix, both in solution and in the crystal state (X-ray diffraction). Cyclic voltammetry measurements agree with the adoption of the 2.05 -helix, characterized by a negligible dipole moment. Thus, elongated α-peptide stretches of this type are insulators rather than charge conductors, the latter being constituted by peptide α-helices. Also, our homo-tetrapeptide has a N-to-C length of about 18.2 Å, almost double than that (9.7 Å) of an α-helical α-tetrapeptide.
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Affiliation(s)
- Saverio Santi
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy
| | - Annalisa Bisello
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy
| | - Roberta Cardena
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy
| | - Silvia Tomelleri
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy
| | - Renato Schiesari
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy
| | - Barbara Biondi
- Institute of Biomolecular Chemistry, Padova Unit, CNR, via Marzolo 1, 35131, Padova, Italy
| | - Marco Crisma
- Institute of Biomolecular Chemistry, Padova Unit, CNR, via Marzolo 1, 35131, Padova, Italy
| | - Fernando Formaggio
- Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131, Padova, Italy
- Institute of Biomolecular Chemistry, Padova Unit, CNR, via Marzolo 1, 35131, Padova, Italy
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5
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Rossi S, Bisello A, Cardena R, Santi S. Testing the Conjugative Properties of Benzodithiophene and Benzotrithiophene in Charge Transfer Multi(ferrocenyl) Systems. Organometallics 2018. [DOI: 10.1021/acs.organomet.8b00537] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Serena Rossi
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Annalisa Bisello
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Roberta Cardena
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Saverio Santi
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
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Rossi S, Bisello A, Cardena R, Orian L, Santi S. Benzodithiophene and Benzotrithiophene as π Cores for Two- and Three-Blade Propeller-Shaped Ferrocenyl-Based Conjugated Systems. European J Org Chem 2017. [DOI: 10.1002/ejoc.201701045] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Serena Rossi
- Department of Chemical Sciences; University of Padova; Via Marzolo 1 35131 Padova Italy
| | - Annalisa Bisello
- Department of Chemical Sciences; University of Padova; Via Marzolo 1 35131 Padova Italy
| | - Roberta Cardena
- Department of Chemical Sciences; University of Padova; Via Marzolo 1 35131 Padova Italy
| | - Laura Orian
- Department of Chemical Sciences; University of Padova; Via Marzolo 1 35131 Padova Italy
| | - Saverio Santi
- Department of Chemical Sciences; University of Padova; Via Marzolo 1 35131 Padova Italy
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Bisello A, Cardena R, Rossi S, Crisma M, Formaggio F, Santi S. Hydrogen-Bond-Assisted, Concentration-Dependent Molecular Dimerization of Ferrocenyl Hydantoins. Organometallics 2017. [DOI: 10.1021/acs.organomet.7b00248] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Annalisa Bisello
- Department
of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Roberta Cardena
- Department
of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Serena Rossi
- Department
of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Marco Crisma
- Institute
of Biomolecular Chemistry, Padova Unit, CNR, via Marzolo 1, 35131 Padova, Italy
| | - Fernando Formaggio
- Department
of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Saverio Santi
- Department
of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
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8
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Donoli A, Marcuzzo V, Moretto A, Crisma M, Toniolo C, Cardena R, Bisello A, Santi S. New bis-ferrocenyl end-capped peptides: synthesis and charge transfer properties. Biopolymers 2016; 100:14-24. [PMID: 23335164 DOI: 10.1002/bip.22197] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 09/26/2012] [Accepted: 10/30/2012] [Indexed: 01/19/2023]
Abstract
In this article, the successful preparation of a new series of 3(10) -helical peptides of different length containing two terminal ferrocenyl (Fc) units and based on the strongly foldameric α-aminoisobutyric (Aib) acid is reported. The synthesis of the Fc-CO-(Aib)(n) -NH-Fc (n = 1-5) homo-peptides was performed by solution methods. Moderate to good yields (26-85%) were obtained in each of the difficult coupling steps of Fc-COOH and the corresponding H-(Aib)(n)-NH-Fc compounds by C-activation with the 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide/7-aza-1-hydroxy-1,2,3-benzotriazole method. Information on the C=O···H-N intramolecularly hydrogen-bonded networks was initially obtained from FT-IR absorption measurements. The N-H stretching (amide A) region allowed us to distinguish which amide protons are involved in intramolecular hydrogen bonds and indicates the formation of an incipient 3(10) -helix structure for peptides containing at least two Aib residues. This conclusion was confirmed by (1)H NMR titrations of the N-H groups of the peptides in CDCl(3) with dimethylsulfoxide and by crystallographic analysis of the N(α) -acylated Fc-CO-(Aib)(5)-NH-Fc pentapeptide amide. The two redox-active Fc groups covalently bound to the termini of the foldameric peptide architectures were used as electrochemical probes. The end-to-end effects of electron holes generated by single and double oxidations were analyzed by means of electrochemical and spectroelectrochemical techniques. The results of these studies indicate that charge transfer across the peptide main chain does occur in the five peptides. In particular, in the pentapeptide 5, charge is transferred through an intramolecular Fe···Fe separation of 14 Å.
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Affiliation(s)
- Alessandro Donoli
- Department of Chemical Sciences, University of Padova, 35131 Padova, Italy
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9
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Affiliation(s)
- Alessandro Donoli
- Department
of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Annalisa Bisello
- Department
of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Roberta Cardena
- Department
of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Marco Crisma
- Institute
of Biomolecular Chemistry, Padova Unit, CNR, via Marzolo 1, 35131 Padova, Italy
| | - Laura Orian
- Department
of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
| | - Saverio Santi
- Department
of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy
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10
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Santi S, Bisello A, Cardena R, Donoli A. Key multi(ferrocenyl) complexes in the interplay between electronic coupling and electrostatic interaction. Dalton Trans 2015; 44:5234-57. [DOI: 10.1039/c4dt03581j] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this review, the properties of the most significant examples of multi(ferrocenyl) cations containing a number of ferrocenyl units from two to six are discussed and the results are compared with the outcomes of some of our recent studies on conjugated ferrocenyl complexes.
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Affiliation(s)
- Saverio Santi
- Department of Chemical Sciences
- University of Padova
- 35131 Padova
- Italy
| | - Annalisa Bisello
- Department of Chemical Sciences
- University of Padova
- 35131 Padova
- Italy
| | - Roberta Cardena
- Department of Chemical Sciences
- University of Padova
- 35131 Padova
- Italy
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Song G, Bisello A. Novel mechanism for the vascular effect of EBP50: Akt-mediated phosphorylation of ebp50. Atherosclerosis 2014. [DOI: 10.1016/j.atherosclerosis.2014.05.096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Donoli A, Bisello A, Cardena R, Prinzivalli C, Crisma M, Santi S. Charge Transfer Properties in Cyclopenta[l]phenanthrene Ferrocenyl Complexes. Organometallics 2014. [DOI: 10.1021/om4009668] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Alessandro Donoli
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Annalisa Bisello
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Roberta Cardena
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Cristina Prinzivalli
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Marco Crisma
- Institute of Biomolecular Chemistry, Padova Unit, CNR, via Marzolo
1, 35131 Padova, Italy
| | - Saverio Santi
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
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13
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Affiliation(s)
- Alessandro Donoli
- Dipartimento di
Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Annalisa Bisello
- Dipartimento di
Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Roberta Cardena
- Dipartimento di
Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Cristina Prinzivalli
- Dipartimento di
Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Saverio Santi
- Dipartimento di
Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
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14
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Williams K, Abanquah D, Joshi-Gokhale S, Otero A, Lin H, Guthalu NK, Zhang X, Mozar A, Bisello A, Stewart AF, Garcia-Ocaña A, Vasavada RC. Systemic and acute administration of parathyroid hormone-related peptide(1-36) stimulates endogenous beta cell proliferation while preserving function in adult mice. Diabetologia 2011; 54:2867-77. [PMID: 21800111 DOI: 10.1007/s00125-011-2260-z] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Accepted: 06/03/2011] [Indexed: 11/25/2022]
Abstract
AIMS/HYPOTHESIS A major focus in the treatment of diabetes is to identify factors that stimulate endogenous beta cell growth while preserving function. The first 36 amino acids of parathyroid hormone-related protein (PTHrP) are sufficient to enhance proliferation and function in rodent and human beta cells in vitro. This study examined whether acute and systemic administration of the amino-terminal PTHrP(1-36) peptide can achieve similar effects in rodent beta cells in vivo. METHODS Adult male mice were injected with 40, 80 or 160 μg of PTHrP(1-36) per kg body weight or with vehicle for 25 days. Glucose and beta cell homeostasis, as well as expression of differentiation markers and cell cycle genes were analysed. RESULTS All three doses of PTHrP(1-36) significantly enhanced beta cell proliferation in vivo at day 25, with 160 μg/kg PTHrP(1-36) increasing proliferation as early as day 5. Importantly, the two higher doses of PTHrP(1-36) caused a significant 30% expansion of beta cell mass, with a short-term improvement in glucose tolerance. PTHrP(1-36) did not cause hypercalcaemia, or change islet number, beta cell size, beta cell death or expression of differentiation markers. Analysis of islet G1/S cell cycle proteins revealed that chronic overabundance of PTHrP(1-139) in the beta cell significantly increased the cell cycle activator cyclin D2 and decreased levels of cyclin-dependent kinase 4 inhibitor (p16( Ink4a ) [Ink4a also known as Cdkn2a]), but acute treatment with PTHrP(1-36) did not. CONCLUSIONS/INTERPRETATION Acute and systemic administration of PTHrP(1-36) increases rodent beta cell proliferation and mass without negatively affecting function or survival. These findings highlight the future potential therapeutic effectiveness of this peptide under diabetes-related pathophysiological conditions.
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Affiliation(s)
- K Williams
- Division of Endocrinology, University of Pittsburgh, 200 Lothrop St, BST-E1157, Pittsburgh, PA 15261, USA
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15
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Donoli A, Bisello A, Cardena R, Ceccon A, Bassetti M, D’Annibale A, Pasquini C, Raneri A, Santi S. Electron transfer within C4 unsaturated spacers between terminal ferrocenyl moieties. Inorganica Chim Acta 2011. [DOI: 10.1016/j.ica.2011.03.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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16
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Donoli A, Marcuzzo V, Moretto A, Toniolo C, Cardena R, Bisello A, Santi S. Charge mapping in 3(10)-helical peptide chains by oxidation of the terminal ferrocenyl group. Org Lett 2011; 13:1282-5. [PMID: 21341757 DOI: 10.1021/ol102864s] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Two series of 3(10)-helical peptides of different lengths and rigidity, based on the strongly foldameric α-aminoisobutyric acid and containing a terminal ferrocenyl unit, have been synthesized. Oxidation-state sensitive spectroscopic tags of helical peptides, the N-H groups, allowed mapping of the charge delocalization triggered by oxidation of the terminal ferrocenyl moiety and were monitored by IR spectroelectrochemistry.
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Affiliation(s)
- Alessandro Donoli
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
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17
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Donoli A, Bisello A, Cardena R, Benetollo F, Ceccon A, Santi S. Single Two-Electron Transfers and Successive One-Electron Transfers in Biferrocenyl−Indacene Isomers. Organometallics 2011. [DOI: 10.1021/om101123a] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Alessandro Donoli
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Annalisa Bisello
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Roberta Cardena
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Franco Benetollo
- CNR, Istituto di Chimica Inorganica e delle Superfici, C.so Stati Uniti 4, 35127 Padova, Italy
| | - Alberto Ceccon
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Saverio Santi
- CNR, Istituto di Chimica Inorganica e delle Superfici, C.so Stati Uniti 4, 35127 Padova, Italy
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18
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Santi S, Durante C, Donoli A, Bisello A, Orian L, Ganis P, Ceccon A, Benetollo F. Intervalence Charge Transfer in Cationic Heterotrinuclear Fe(III)−Rh(I)−Cr(0) Triads of the Polyaromatic Cyclopentadienyl−Indenyl Ligand. Organometallics 2010. [DOI: 10.1021/om900903e] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Saverio Santi
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Christian Durante
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Alessandro Donoli
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Annalisa Bisello
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Laura Orian
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Paolo Ganis
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Alberto Ceccon
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padova, Italy
| | - Franco Benetollo
- CNR, Istituto di Chimica Inorganica e delle Superfici, C.so Stati Uniti 4, 35127 Padova, Italy
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Santi S, Durante C, Donoli A, Bisello A, Orian L, Ceccon A, Crociani L, Benetollo F. Mixed Valence Properties in Ferrocenyl-Based Bimetallic FeCp−Indenyl−MLn Complexes: Effect of the MLn Group. Organometallics 2009. [DOI: 10.1021/om800954b] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Santi S, Orian L, Donoli A, Bisello A, Scapinello M, Benetollo F, Ganis P, Ceccon A. Synthesis of the Prototypical Cyclic Metallocene Triad: Mixed‐Valence Properties of [(FeCp)3(trindenyl)] Isomers. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200801124] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Santi S, Orian L, Donoli A, Bisello A, Scapinello M, Benetollo F, Ganis P, Ceccon A. Synthesis of the Prototypical Cyclic Metallocene Triad: Mixed‐Valence Properties of [(FeCp)3(trindenyl)] Isomers. Angew Chem Int Ed Engl 2008; 47:5331-4. [DOI: 10.1002/anie.200801124] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Santi S, Orian L, Donoli A, Durante C, Bisello A, Ganis P, Ceccon A, Crociani L, Benetollo F. Charge Transfer through Isomeric Unsaturated Hydrocarbons. Redox Switchable Optical Properties and Electronic Structure of Substituted Indenes with a Pendant Ferrocenyl. Organometallics 2007. [DOI: 10.1021/om700673m] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Santi S, Orian L, Durante C, Bencze EZ, Bisello A, Donoli A, Ceccon A, Benetollo F, Crociani L. Metal–Metal Electronic Coupling insyn andanti Stereoisomers of Mixed-Valent (FeCp)2-, (RhL2)2-, and (FeCp)(RhL2)-as-Indacenediide Ions. Chemistry 2007; 13:7933-47. [PMID: 17616957 DOI: 10.1002/chem.200700052] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The extent of metal-metal electronic coupling was quantified for a series of syn and anti stereoisomers of (FeCp)(2)-, (RhL(2))(2)- and (FeCp)(RhL(2))- (L(2)=1,5-cyclooctadiene (cod), L=CO) as-indacenediide mixed-valent ions by spectroelectrochemical and DFT studies. The effect of the syn/anti orientation of the metal units with respect to the planar aromatic ligand indicates that electron transfer occurs through the bridge rather than through space. The nature of the metal was found to be crucial: while homobimetallic diiron species are localised valence-trapped ions (Class II), the dirhodium analogues are almost delocalised mixed-valent ions (borderline and Class III). Finally, despite their redox asymmetry, even in the heterobimetallic iron-rhodium as-indacenediide complexes, strong metal-metal coupling is present. In fact, oxidation of the iron centre is accompanied by electron transfer from rhodium to iron and formation of a reactive 17-electron rhodium site. syn and anti Fe-Rh as-indacenediide complexes are rare examples of heterobimetallic systems which can be classified as borderline Class II/Class III species.
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Affiliation(s)
- Saverio Santi
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova via Marzolo 1, 35131 Padova, Italy.
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Santi S, Orian L, Durante C, Bisello A, Benetollo F, Crociani L, Ganis P, Ceccon A. Tuning the Electronic Communication in Heterobimetallic Mixed-Valence Ions of (1-Ferrocenyl)- and (2-Ferrocenyl)indenyl Rhodium Isomers. Chemistry 2007; 13:1955-68. [PMID: 17171728 DOI: 10.1002/chem.200600724] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A series of heterobimetallic complexes of general structure [RhL(2){eta(5)-(2-ferrocenyl)indenyl}] (L(2)=cod, nbd, L=CO; cod=cyclooctadiene; nbd=norbornadiene) has been synthesised with the aim of tuning the metal-metal interaction in their mixed-valence ions generated both by chemical and electrochemical oxidation, and the results are compared with those obtained for [RhL(2){eta(5)-(1-ferrocenyl)indenyl}] isomers. Crystallographic studies and DFT calculations provide a detailed description of the structural and electronic features of these complexes evidencing a significant difference in the extent of planarity of the flexible bridging ligand between the 1- and 2-ferrocenyl isomers. Independent experimental probes, in particular the potential splitting in the cyclic voltammograms and the IT bands in the near-IR spectra, are rationalised in the framework of Marcus-Hush theory and at quantum chemistry level by DFT and TD-DFT methods. These methods allow us to establish a trend based on the magnitude of iron-rhodium electronic coupling H(ab) ranging from valence trapped to almost delocalised ions. The quasi planar bridge and the olefin ancillary ligands make [Rh(nbd){eta(5)-(2-ferrocenyl)indenyl}](+) and [Rh(cod){eta(5)-(2-ferrocenyl)indenyl}](+) rare examples of heterobimetallic systems which can be classified as borderline Class II/Class III species.
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Affiliation(s)
- Saverio Santi
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, via Marzolo 1, 35131 Padua, Italy.
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Santi S, Ceccon A, Bisello A, Durante C, Ganis P, Orian L, Benetollo F, Crociani L. Designing Molecules for Metal−Metal Electronic Communication: Synthesis and Molecular Structure of the Couple of Heterobimetallic Isomers [η6-(2-Ferrocenyl)indene]-Cr(CO)3 and [η6-(3-Ferrocenyl)indene]-Cr(CO)3. Organometallics 2005. [DOI: 10.1021/om050307c] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Orian L, Bisello A, Santi S, Ceccon A, Saielli G. 103Rh NMR Chemical Shifts in Organometallic Complexes: A Combined Experimental and Density Functional Study. Chemistry 2004; 10:4029-40. [PMID: 15316995 DOI: 10.1002/chem.200305671] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Experimental 103Rh NMR chemical shifts of mono- and binuclear rhodium(I) complexes containing s- or as-hydroindacenide and indacenediide bridging ligands with different ancillary ligands (1,5-cyclooctadiene, ethylene, carbonyl) are presented. A protocol, based on density functional theory calculations, was established to determine 103Rh NMR shielding constants in order to rationalise the effects of electronic and structural variations on the spectroscopic signal, and to gain insight into the efficiency of this computational method when applied to organometallic systems. Scalar and spin-orbit relativistic effects based on the ZORA (zeroth order regular approximation) level have been taken into account and discussed. A good agreement was found for model compounds over a wide range of chemical shifts of rhodium (approximately 10,000 ppm). This allowed us to discuss the experimental and calculated delta(103Rh) in larger complexes and to relate it to their electronic structure.
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Affiliation(s)
- Laura Orian
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
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Ceccon A, Santi S, Orian L, Bisello A. Electronic communication in heterobinuclear organometallic complexes through unsaturated hydrocarbon bridges. Coord Chem Rev 2004. [DOI: 10.1016/j.ccr.2004.02.007] [Citation(s) in RCA: 273] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Schievano E, Mammi S, Carretta E, Fiori N, Corich M, Bisello A, Rosenblatt M, Chorev M, Peggion E. Conformational and biological characterization of human parathyroid hormone hPTH(1-34) analogues containing beta-amino acid residues in positions 17-19. Biopolymers 2004; 70:534-47. [PMID: 14648764 DOI: 10.1002/bip.10508] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The N-terminal 1-34 fragment of parathyroid hormone (PTH) elicits the full spectrum of bone-related biological activities of the intact native sequences. It has been suggested that the structural elements essential for bioactivity are two helical segments located at the N-terminal and C-terminal sequences, connected by hinges or flexible points around positions 12 and 19. In order to assess the relevance of the local conformation around Gly(18) upon biological function, we synthesized and characterized the following human (h) PTH(1-34) analogues containing beta-amino acid residues: [analogues: see text]. Biological activity and binding affinity of analogue I are one order of magnitude lower than those of the parent compound. In analogue II, both binding affinity and biological activity are partially recovered. Analogues III and V have no binding affinity and very low biological activity. Both bioactivity and binding affinity are partially recovered in analogue IV. The conformational properties of the analogues in aqueous solution containing dodecylphosphocholine micelles were studied by CD, 2D-nuclear magnetic resonance and molecular dynamics calculations. The results confirmed the presence in all analogues of two helical segments located at the N-terminal and C-terminal sequences. The insertion of beta-amino acid residues around position 18 does not cause appreciable conformational differences in the five analogues. The differences in biological activity and binding affinity among the five analogues cannot be related to structural differences in the membrane mimetic environment reported in this study. Our results stress the importance of the side-chain functionalities in the sequence 17-19 for biological function.
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Affiliation(s)
- E Schievano
- Department of Organic Chemistry, University of Padova, Institute of Biomolecular Chemistry, C.N.R, Via Marzolo 1, 35131 Padova, Italy
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Peggion E, Mammi S, Schievano E, Silvestri L, Schiebler L, Bisello A, Rosenblatt M, Chorev M. Structure-function studies of analogues of parathyroid hormone (PTH)-1-34 containing beta-amino acid residues in positions 11-13. Biochemistry 2002; 41:8162-75. [PMID: 12069609 DOI: 10.1021/bi0200155] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The 1-34 N-terminal fragments of human parathyroid hormone (PTH) and PTH-related protein (PTHrP) elicit the full spectrum of bone-relevant activities characteristic of the intact hormones. The structural elements believed to be required for receptor binding and biological activity are two helical segments, one N-terminal and one C-terminal, connected by hinges or flexible points located around positions 12 and 19. To test this hypothesis, we synthesized and characterized the following analogues of PTH-(1-34), each containing single or double substitutions with beta-amino acid residues around the putative hinge located at position 12: I. [Nle(8,18),beta-Ala(11,12),Nal(23),Tyr(34)]bPTH-(1-34)NH(2); II. [Nle(8,18),beta-Ala(12,13),Nal(23),Tyr(34)]bPTH-(1-34)NH(2); III. [Nle(8,18),beta-Ala(11),Nal(23),Tyr(34)]bPTH-(1-34)NH(2); IV. [Nle(8,18),beta-hLeu(11),Nal(23),Tyr(34)]bPTH-(1-34)NH(2); V. [Nle(8,18),beta-Ala(12), Nal(23),Tyr(34)]bPTH-(1-34)NH(2); VI. [Nle(8,18),beta-Ala(13), Nal(23),Tyr(34)]bPTH-(1-34)NH(2) (beta-hLeu = beta-homo-leucine; beta-Ala = beta-alanine; Nal = L-2-naphthyl-alanine; Nle = norleucine). Analogues I and III exhibit very low binding affinity and are devoid of adenylyl cyclase activity. Analogue II, despite its very low binding capacity is an agonist. Biological activity and binding capacity are partially restored in analogue IV, and completely restored in analogues V and VI. The conformational properties of the analogues were investigated in aqueous solution containing dodecylphosphocholine (DPC) micelles as a membrane-mimetic environment using CD, 2D-NMR, and molecular dynamics calculations. All peptides fold partially into the alpha-helical conformation in the presence of DPC micelles, with a maximum helix content in the range of 30-35%. NMR analysis reveals the presence of two helical segments, one N-terminal and one C-terminal, as a common structural motif in all analogues. Incorporation of beta-Ala dyads at positions 11,12 and 12,13 in analogues I and II, respectively, enhances the conformational disorder in this portion of the sequence but also destabilizes the N-terminal helix. This could be one of the possible reasons for the lack of biological activity in these analogues. The partial recovery of binding affinity and biological activity in analogue IV, compared to the structurally similar analogue III, is clearly the consequence of the reintroduction of Leu side-chain of the native sequence. In the fully active analogues V and VI, the helix stability at the N-terminus is further increased. Taken together, these results stress the functional importance of the conformational stability of the helical activation domain in PTH-(1-34). Contrary to expectation, insertion of a single beta-amino acid residue in positions 11, 12, or 13 in analogues III-VI does not favor a disordered structure in this portion of the sequence.
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Affiliation(s)
- Evaristo Peggion
- Department of Organic Chemistry, Biopolymer Research Center, University of Padova, CNR, Via Marzolo 1, I-35131 Padua, Italy.
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Santi S, Ceccon A, Carli F, Crociani L, Bisello A, Tiso M, Venzo A. Heterobimetallic Iron−Rhodium Complexes. Synthesis and Characteristics of CpFe(μ-η5:η5-as-indacenediide)RhL2 (L2 = COD, NBD, (ethylene)2). Organometallics 2002. [DOI: 10.1021/om020047o] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Saverio Santi
- Dipartimento di Chimica Fisica, Università degli Studi di Padova, via Loredan 2, 35131 Padova, Italy, and CNR, Centro di Studio sugli Stati Molecolari Radicalici ed Eccitati, via Loredan 2, 35131 Padova, Italy
| | - Alberto Ceccon
- Dipartimento di Chimica Fisica, Università degli Studi di Padova, via Loredan 2, 35131 Padova, Italy, and CNR, Centro di Studio sugli Stati Molecolari Radicalici ed Eccitati, via Loredan 2, 35131 Padova, Italy
| | - Flavio Carli
- Dipartimento di Chimica Fisica, Università degli Studi di Padova, via Loredan 2, 35131 Padova, Italy, and CNR, Centro di Studio sugli Stati Molecolari Radicalici ed Eccitati, via Loredan 2, 35131 Padova, Italy
| | - Laura Crociani
- Dipartimento di Chimica Fisica, Università degli Studi di Padova, via Loredan 2, 35131 Padova, Italy, and CNR, Centro di Studio sugli Stati Molecolari Radicalici ed Eccitati, via Loredan 2, 35131 Padova, Italy
| | - Annalisa Bisello
- Dipartimento di Chimica Fisica, Università degli Studi di Padova, via Loredan 2, 35131 Padova, Italy, and CNR, Centro di Studio sugli Stati Molecolari Radicalici ed Eccitati, via Loredan 2, 35131 Padova, Italy
| | - Mauro Tiso
- Dipartimento di Chimica Fisica, Università degli Studi di Padova, via Loredan 2, 35131 Padova, Italy, and CNR, Centro di Studio sugli Stati Molecolari Radicalici ed Eccitati, via Loredan 2, 35131 Padova, Italy
| | - Alfonso Venzo
- Dipartimento di Chimica Fisica, Università degli Studi di Padova, via Loredan 2, 35131 Padova, Italy, and CNR, Centro di Studio sugli Stati Molecolari Radicalici ed Eccitati, via Loredan 2, 35131 Padova, Italy
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Schievano E, Bisello A, Chorev M, Bisol A, Mammi S, Peggion E. Aib-rich peptides containing lactam-bridged side chains as models of the 3(10)-helix. J Am Chem Soc 2001; 123:2743-51. [PMID: 11456960 DOI: 10.1021/ja0027261] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Aib-rich side chain lactam-bridged oligomers with n =1, 2, 3, were designed and synthesized as putative models of the 3(10)-helix. These peptides were conformationally characterized in aqueous solution containing SDS micelles by CD, NMR, and computer simulations. The lactam bridge between the side chains of L-Glu and L-Lys in (i) and (i+3) positions was introduced in order to enhance the conformational preference toward the right-handed 3(10)-helix. The NMR results clearly indicate that there is an increase of 3(10)-helix formation upon chain elongation. In the dimer and trimer (n = 2 and n = 3, respectively, in the structure reported above) the observed NOE connectivities are compatible with the 3(10)-helical arrangement, confirmed by the temperature coefficients of the amide proton resonances which suggest the presence of a hydrogen-bonded structure. The phi and psi dihedral angles of the structures obtained by molecular dynamics calculations are also compatible with the 3(10)-helix. Identification of the hydrogen-bond pattern indicate that C=O(i)- - -HN(i+3) hydrogen bonds, typical of the 3(10)-helical conformation, are highly probable in all low-energy structures. The CD spectra of these Aib-rich lactam-bridged oligopeptides, obtained in the same solvent system used for NMR experiments, provide important insight into the spectroscopic characteristics of the 3(10)-helix.
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Affiliation(s)
- E Schievano
- University of Padova, Department of Organic Chemistry, Biopolymer Research Center, C.N.R, Via Marzolo 1, 35131 Padua, Italy
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Ferrari SL, Bisello A. Cellular distribution of constitutively active mutant parathyroid hormone (PTH)/PTH-related protein receptors and regulation of cyclic adenosine 3',5'-monophosphate signaling by beta-arrestin2. Mol Endocrinol 2001; 15:149-63. [PMID: 11145746 DOI: 10.1210/mend.15.1.0587] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
PTH promotes endocytosis of human PTH receptor 1 (PTH1Rc) by activating protein kinase C and recruiting beta-arrestin2. We examined the role of beta-arrestin2 in regulating the cellular distribution and cAMP signaling of two constitutively active PTH1Rc mutants, H223R and T410P. Overexpression of a beta-arrestin2-green fluorescent protein (GFP) conjugate in COS-7 cells inhibited constitutive cAMP accumulation by H223R and T410P in a dose-dependent manner, as well as the response to PTH of both mutant and wild-type PTH1Rcs. The cellular distribution of PTH1Rc-GFP conjugates, fluorescent ligands, and ssarrestin2-GFP was analyzed by fluorescence microscopy in HEK-293T cells. In cells expressing either receptor mutant, a ligand-independent mobilization of beta-arrestin2 to the cell membrane was observed. In the absence of ligand, H223R and wild-type PTH1Rcs were mainly localized on the cell membrane, whereas intracellular trafficking of T410P was also observed. While agonists promoted beta-arrestin2-mediated endocytosis of bot PTH1Rc mutants, antagonists were rapidly internalized only with T410P. The protein kinases inhibitor, staurosporine, significantly decreased internalization of ligand-PTH1Rc mutant complexes, although the recruitment of beta-arrestin2 to the cell membrane was unaffected. Moreover, in cells expressing a truncated wild-type PTH1Rc lacking the C-terminal cytoplasmic domain, agonists stimulated translocation of beta-arrestin2 to the cell membrane followed by ligand-receptor complex internalization without associated beta-arrestin2. In conclusion, cAMP signaling by constitutively active mutant and wild-type PTH1Rcs is inhibited by a receptor interaction with beta-arrestin2 on the cell membrane, possibly leading to uncoupling from G(s)alpha. This phenomenon is independent from protein kinases activity and the receptor C-terminal cytoplasmic domain. In addition, there are differences in the cellular localization and internalization features of constitutively active PTH1Rc mutants H223R and T410P.
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Affiliation(s)
- S L Ferrari
- Harvard-Thorndike and Charles A. Dana Research Laboratories, Department of Medicine Beth Israel Deaconess Medical Center and Harvard Medical School Boston, Massachusetts 02215, USA.
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Greenberg Z, Bisello A, Mierke DF, Rosenblatt M, Chorev M. Mapping the bimolecular interface of the parathyroid hormone (PTH)-PTH1 receptor complex: spatial proximity between Lys(27) (of the hormone principal binding domain) and leu(261) (of the first extracellular loop) of the human PTH1 receptor. Biochemistry 2000; 39:8142-52. [PMID: 10889020 DOI: 10.1021/bi000195n] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In an effort to characterize the bimolecular interface between parathyroid hormone (PTH) and its human receptor PTH1-Rc (hPTH1-Rc), we previously identified two contact sites in the receptor: one for position 1 and another for position 13 (located at the ends of the principal activation domain) in PTH(1-34). The present study reports a third, novel "contact site" between hPTH1-Rc and Lys(27) of PTH(1-34). Lys(27) is located in the principal binding domain of the hormone (residues 25-34). The photoreactive PTH(1-34) analogue K27 contains a benzophenone (BP) moiety on Lys(27). The analogue binds to stably transfected HEK 293/C-21 cells (which express a high level of recombinant hPTH1-Rc) and stimulates adenylyl cyclase activity with a potency similar to PTH(1-34). In addition, (125)I-K27 cross-links effectively and specifically to the hPTH1-Rc. Enzymatic (Glu-C and Lys-C) and chemical (CNBr and BNPS-skatole) digestions of the photoconjugate between (125)I-K27 and hPTH1-Rc were performed. In addition, photoconjugates involving the bioactive mutants [L261M]- and [R262K]-hPTH1-Rc, transiently expressed in COS-7 cells, were also digested. The data obtained clearly identify L(261) or R(262) of the first extracellular loop of hPTH1-Rc as the contact site for Lys(27) in the hormone. On the basis of (i) the similarity in molecular mass between the CNBr digest of the (125)I-K27-[L261M]hPTH1-Rc conjugate and free (125)I-K27 and (ii) the failure to cross-link (125)I-K27 to a bioactive mutant receptor [L261A]hPTH1-Rc, we conclude that L(261) is the cross-linking site. These results provide the first demonstration of an interaction between the principal binding domain of PTH and the first extracellular loop of hPTH1-Rc. Revealing proximity of Lys(27) (in PTH) to L(261) (in hPTH1-Rc) provides additional insight into the nature of the ligand-receptor bimolecular interface and clearly illustrates that the extracellular loops of the receptor contribute to the specificity of the PTH-PTH1-Rc interaction. Taken together with previous studies, the new findings add important constraints on the possible positioning of the C-terminal helix of PTH (which contains the principal binding domain) relative to the first extracellular loop and the distal C-terminal helix of the large extracellular amino terminal domain of the PTH1-Rc.
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Affiliation(s)
- Z Greenberg
- Division of Bone and Mineral Metabolism, Charles A. Dana and Thorndike Laboratories, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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Piserchio A, Bisello A, Rosenblatt M, Chorev M, Mierke DF. Characterization of parathyroid hormone/receptor interactions: structure of the first extracellular loop. Biochemistry 2000; 39:8153-60. [PMID: 10889021 DOI: 10.1021/bi000196f] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structural features of the first extracellular loop (ECL1) of the parathyroid hormone receptor (PTH1R) in the presence of dodecylphosphocholine micelles have been determined using high-resolution NMR techniques. The structure of the receptor fragment, PTH1R(241-285), includes three alpha-helices for residues 241-244, 256-264, and 275-284. The first and third correspond to the end and the beginning of transmembrane helices 2 and 3, respectively. Centrally located in the second helix is L(261), found to cross-link to Lys(27) of parathyroid hormone, PTH(1-34) [Greenberg, Z., Bisello, A., Mierke, D. F., Rosenblatt, M., and Chorev, M. (2000) Biochemistry 39, 8142-8152]. On the basis of nitroxide radical-induced relaxation studies, the central helix is found to associate with the surface of the membrane mimetic. These data, in conjunction with previous results indicating a preference of PTH for the lipid surface, suggest a membrane-associated pathway for the initial recognition and binding of PTH to its G-protein-coupled receptor. Using the structural features of ECL1 as determined here, along with the structure of the PTH(1-34), the intermolecular interactions consistent with the contact point between L(261)(receptor)-Lys(27)(ligand) are identified.
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Affiliation(s)
- A Piserchio
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA
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Ceccon A, Bisello A, Crociani L, Gambaro A, Ganis P, Manoli F, Santi S, Venzo A. Synthesis, structure and reactivity of homobimetallic Rh(I) and Ir(I) complexes of s- and as-indacene-diide. J Organomet Chem 2000. [DOI: 10.1016/s0022-328x(00)00034-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Han Y, Bisello A, Nakamoto C, Rosenblatt M, Chorev M. 3-(3'-fluorenyl-9'-oxo)-L-alanine: a novel photoreactive conformationally constrained amino acid. J Pept Res 2000; 55:230-9. [PMID: 10727105 DOI: 10.1034/j.1399-3011.2000.00175.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Photoaffinity scanning of the ligand-G-protein-coupled receptor bimolecular interface is a direct approach to mapping the interactions of ligands and receptors. Such studies are an important first step toward generating an experimentally based model of the ligand-receptor complex. The synthesis and spectroscopic characterization of Boc-3-(3'-fluorenyl-9'-oxo)-L-alanine and 9-fluorenone-3-carboxylic acid are described. Incorporation of these two photophores into the parathyroid hormone (PTH) molecule yields potent agonists. These photoreactive analogs cross-link specifically with the recombinant human PTH1 receptor stably expressed in human embryonic kidney cells. The availability of the 9-fluorenone (a conformationally constrained derivative of benzophenone, the abundantly used photophore) for photoaffinity scanning provides an important tool to probe the effect of conformational flexibility of the photophore on the selection of the cross-linking site in the macromolecular acceptor.
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Affiliation(s)
- Y Han
- Division of Bone and Mineral Metabolism, Beth Israel Deaconess Medical Center/Harvard Medical School, Boston, MA 02215, USA
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Ferrari SL, Traianedes K, Thorne M, Lafage-Proust MH, Genever P, Cecchini MG, Behar V, Bisello A, Chorev M, Rosenblatt M, Suva LJ. A role for N-cadherin in the development of the differentiated osteoblastic phenotype. J Bone Miner Res 2000; 15:198-208. [PMID: 10703921 DOI: 10.1359/jbmr.2000.15.2.198] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Cadherins are a family of cell surface adhesion molecules that play an important role in tissue differentiation. A limited repertoire of cadherins has been identified in osteoblasts, and the role of these molecules in osteoblast function remains to be elucidated. We recently cloned an osteoblast-derived N-cadherin gene from a rat osteoblast complementary DNA library. After in situ hybridization of rat bone and immunohistochemistry of human osteophytes, N-cadherin expression was localized prominently in well-differentiated (lining) osteoblasts. Northern blot hybridization in primary cultures of fetal rat calvaria and in human SaOS-2 and rat ROS osteoblast-like cells showed a relationship between N-cadherin messenger RNA expression and cell-to-cell adhesion, morphological differentiation, and alkaline phosphatase and osteocalcin gene expression. Treatment with a synthetic peptide containing the His-Ala-Val (HAV) adhesion motif of N-cadherin significantly decreased bone nodule formation in primary cultures of fetal rat calvaria and inhibited cell-to-cell contact in rat osteoblastic TRAB-11 cells. HAV peptide also regulated the expression of specific genes such as alkaline phosphatase and the immediate early gene zif268 in SaOS-2 cells. Transient transfection of SaOS-2 cells with a dominant-negative N-cadherin mutant (NCADdeltaC) significantly inhibited their morphological differentiation. In addition, aggregation of NCTC cells derived from mouse connective tissue stably transfected with osteoblast-derived N-cadherin was inhibited by either treatment with HAV or transfection with NCADdeltaC. Together, these results strongly support a role for N-cadherin, in concert with other previously identified osteoblast cadherins, in the late stages of osteoblast differentiation.
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Affiliation(s)
- S L Ferrari
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts, USA
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Behar V, Bisello A, Bitan G, Rosenblatt M, Chorev M. Photoaffinity cross-linking identifies differences in the interactions of an agonist and an antagonist with the parathyroid hormone/parathyroid hormone-related protein receptor. J Biol Chem 2000; 275:9-17. [PMID: 10617579 DOI: 10.1074/jbc.275.1.9] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Analogs of parathyroid hormone (PTH)-related protein (PTHrP), singularly substituted with a photoreactive L-p-benzoylphenylalanine (Bpa) at each of the first 6 N-terminal positions, were pharmacologically evaluated in human embryonic kidney cells stably expressing the recombinant human PTH/PTHrP receptor. Two of these analogs, in which the photoreactive residue is either in position 1 or 2 (Bpa(1)- and Bpa(2)-PTHrP, respectively) displayed high affinity binding. Bpa(1)-PTHrP also displayed high efficacy for the stimulation of increased cAMP levels. Surprisingly, Bpa(2)-PTHrP was found to be a potent antagonist, despite the presence of the principal activation domain (sequence 1-6). Analysis of the digestion profiles of the ligand-receptor photoconjugates revealed that both the agonist and the antagonist cross-link to the S-CH(3) group of Met(425) in transmembrane domain 6 of the human PTH/PTHrP receptor. However, the antagonist Bpa(2)-PTHrP also cross-links to a proximal site within the receptor domain Pro(415)-Met(425). Unlike the antagonist Bpa(2)-PTHrP, the potent agonist Bpa(2)-PTH, also bearing the Bpa residue in position 2, cross-links only to the S-CH(3) group of Met(425) (similar to Bpa(1)-PTHrP and Bpa(1)-PTH). Taken together, these results suggest that the antagonist Bpa(2)-PTHrP is able to distinguish between two distinct conformations of the receptor. The comparison between PTHrP analogs substituted by Bpa at two consecutive positions and across PTH and PTHrP reveals insights into the PTH/PTHrP ligand-receptor bimolecular interaction at the level of a single amino acid.
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Affiliation(s)
- V Behar
- Division of Bone and Mineral Metabolism, Charles A. Dana Laboratories, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA
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Venzo A, Bisello A, Ceccon A, Manoli F, Santi S. Low hapticity intermediates in the carbonylation of (η5-2,6-dimethyl-5-hydro-s-indacenide)-Ir(η4-COD). INORG CHEM COMMUN 2000. [DOI: 10.1016/s1387-7003(99)00167-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Ferrari SL, Behar V, Chorev M, Rosenblatt M, Bisello A. Endocytosis of ligand-human parathyroid hormone receptor 1 complexes is protein kinase C-dependent and involves beta-arrestin2. Real-time monitoring by fluorescence microscopy. J Biol Chem 1999; 274:29968-75. [PMID: 10514480 DOI: 10.1074/jbc.274.42.29968] [Citation(s) in RCA: 132] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endocytosis and intracellular trafficking of the human parathyroid hormone receptor subtype 1 (hPTH1-Rc) and its ligands was monitored independently by real-time fluorescence microscopy in stably transfected HEK-293 cells. Complexes of fluorescence-labeled parathyroid hormone (PTH)-(1-34) agonist bound to the hPTH1-Rc internalized rapidly at 37 degrees C via clathrin-coated vesicles, whereas fluorescent PTH-(7-34) antagonist-hPTH1Rc complexes did not. A functional C terminus epitope-tagged receptor (C-Tag-hPTH1-Rc) was immunolocalized to the cell membrane and, to a lesser extent, the cytoplasm. PTH and PTH-related protein agonists stimulated C-Tag-hPTH1-Rc internalization. Relocalization to the cell membrane occurred 1 h after removal of the ligand. Endocytosis of fluorescent PTH agonist-hPTH1-Rc complexes was blocked by the protein kinase C (PKC) inhibitor staurosporine but not by the specific protein kinase A inhibitor N-(2-(methylamino)ethyl)-5-isoquinoline-sulfonamide. Fluorescent PTH antagonist-hPTH1-Rc complexes were rapidly internalized after PKC activation by phorbol 12-myristate 13-acetate or thrombin, but not after stimulation of the cAMP/protein kinase A pathway by forskolin. In cells co-expressing the hPTH1-Rc and a green fluorescent protein-beta-arrestin2 fusion protein (beta-Arr2-GFP), PTH agonists stimulated beta-Arr2-GFP mobilization to the cell membrane. Subsequently, fluorescent PTH-(1-34)-hPTH1Rc complexes and beta-Arr2-GFP co-localized intracellularly. In conclusion, agonist-activated hPTH1-Rc internalization involves beta-arrestin mobilization and targeting to clathrin-coated vesicles. Our results also indicate that receptor occupancy, rather than receptor-mediated signaling, is necessary, although not sufficient, for endocytosis of the hPTH1-Rc. Activation of PKC, however, is absolutely required.
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Affiliation(s)
- S L Ferrari
- Division of Bone and Mineral Metabolism, Harvard-Thorndike Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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Behar V, Bisello A, Rosenblatt M, Chorev M. Direct identification of two contact sites for parathyroid hormone (PTH) in the novel PTH-2 receptor using photoaffinity cross-linking. Endocrinology 1999; 140:4251-61. [PMID: 10465299 DOI: 10.1210/endo.140.9.6950] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Direct examination of the interacting sites between PTH and the human PTH2 receptor (PTH2R) was conducted by photoaffinity cross-linking followed by protein digestion and mapping of the radiolabeled photoconjugated receptor. Photoreactive analogs of PTH, individually substituted with an L-p-benzoylphenylalanine (Bpa) at each of the first 6 N-terminal positions, were pharmacologically evaluated in cells stably expressing recombinant PTH2R. One highly bioactive analog, [Bpa1,Nle8,18,Arg13,26,27,L-2-Nal23,Tyr34]PTH-(1-34)NH 2 (Bpa1-PTH), was chosen for cross-linking studies. In addition, a PTH analog in which the photoreacive moiety is at the mid-region position 13 (K13) was demonstrated to be bioactive, then cross-linked to PTH2R. The minimal digestion-restricted domain containing the contact site ("contact domain") for 125I-Bpa1-PTH is in the sixth transmembrane domain and part of the third extracellular loop, spanning residues Ser364-Met395 of the receptor. This domain was further confirmed and refined by cross-linking 125I-Bpa1-PTH to two receptor mutants, PTH2R[V380M]- and PTH2R[V380M,M395L]-receptors. Treatment of the cross-linked conjugates with cyanogen bromide identified a single amino acid (position 380) as the putative contact point. The contact domain for 125I-K13 is located in the N-terminal extracellular tail of the receptor (in the C-terminal portion) and spans Gln138-Met147. Further validation of this contact domain was accomplished by photocross-linking to point-mutated PTH2R[K137R] receptor. Previous studies in which PTH analogs were cross-linked to human PTH/PTHrP receptor (PTH1R) identified Met425 and Phe173-Met189 as the contact sites for Bpa1-PTH and K13, respectively. These studies demonstrate that both receptor subtypes, PTH1- and PTH2-receptors, use analogous sites for interaction with positions 1 and 13 in PTH.
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Affiliation(s)
- V Behar
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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Bisello A, Behar V, Greenberg Z, Suva LJ, Rosenblatt M, Chorev M. Development of a photoreactive parathyroid hormone antagonist to probe antagonist-receptor bimolecular interaction. J Pept Res 1999; 54:120-8. [PMID: 10461746 DOI: 10.1034/j.1399-3011.1999.00096.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Parathyroid hormone (PTH) and PTH-related protein (PTHrP) exert their calciotropic activities by binding to a specific seven-transmembrane-helix-containing G protein-coupled receptor mainly located in bone and kidney cells. In order to map in detail the nature of hormone-receptor interaction, we are employing 'photoaffinity scanning' of the bimolecular interface. To this end, we have developed photoreactive benzophenone (BP)-containing PTH analogs which can be specifically and efficiently cross-linked to the human (h) PTH/PTHrP receptor. In this report, we describe the photocross-linking of a BP-containing PTH antagonist, [Nle8,18,D-2-Nal12,Lys13(epsilon-BP),2-Nal23,Tyr34]bPT H(7-34)NH2 (ANT) to the recombinant hPTH/PTHrP receptor stably expressed in human embryonic kidney cells (HEK-293, clone C-21). This photoreactive antagonist has high affinity for the hPTH/PTHrP receptor and inhibits agonist-induced cyclase activity and intracellular calcium release. The photo-induced cross-linking of the radioiodinated antagonist (125I-ANT) to the recombinant hPTH/PTHrP receptor followed by SDS-PAGE analysis reveals a single radiolabeled band of approximately 85kDa, similar to that observed after cross-linking of a radioiodinated BP-containing agonist. The formation of this covalent 125I-ANT - hPTH/PTHrP receptor conjugate is competed dose-dependently by a variety of unlabelled PTH- and PTHrP-derived agonists and antagonists. This is the first report of a specific and efficient photocross-linking of a radioiodinated PTH antagonist to the hPTH/PTHrP receptor. Therefore, it provides the opportunity to study directly the nature of the bimolecular interaction of PTH antagonist with the hPTH/PTHrP receptor.
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Affiliation(s)
- A Bisello
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA
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Abstract
The N-terminal 1-34 segments of both parathyroid hormone (PTH) and parathyroid hormone-related protein (PTHrP) bind and activate the same membrane receptor in spite of major differences in their amino acid sequence. The hypothesis was made that they share the same bioactive conformation when bound to the receptor. A common structural motif in all bioactive fragments of the hormone in water/trifluoroethanol mixtures or in aqueous solution containing detergent micelles is the presence of two helical segments at the N- and C-termini of the sequence. In order to stabilize the helical structures, we have recently synthesized and studied the PTHrP(1-34) analog [(Lys13-Asp17, Lys26-Asp30)]PTHrP(1-34)NH2, which contains lactam-constrained Lys-Asp side chains at positions i, i+4. This very potent agonist exhibits enhanced helix stability with respect to the corresponding linear peptide and also two flexible sites at positions 12 and 19 in 1:1 trifluoroethanol/water. These structural elements have been suggested to play a critical role in bioactivity. In the present work we have extended our conformational studies on the bicyclic lactam-constrained analog to aqueous solution. By CD, 2D-NMR and structure calculations we have shown that in water two helical segments are present in the region of the lactam bridges (13-18, and 26-31) with high flexibility around Gly12 and Arg19. Thus, the essential structural features observed in the aqueous-organic medium are maintained in water even if, in this solvent, the overall structure is more flexible. Our findings confirm the stabilizing effect of side-chain lactam constraints on the alpha-helical structure.
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Affiliation(s)
- E Schievano
- Department of Organic Chemistry, Biopolymer Research Center, University of Padova, Italy
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Adams AE, Bisello A, Chorev M, Rosenblatt M, Suva LJ. Arginine 186 in the extracellular N-terminal region of the human parathyroid hormone 1 receptor is essential for contact with position 13 of the hormone. Mol Endocrinol 1998; 12:1673-83. [PMID: 9817594 DOI: 10.1210/mend.12.11.0198] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
PTH maintains blood calcium concentrations within the physiological range by acting on a G protein-coupled heptahelical receptor (PTH1 Rc) located primarily in cells in bone and kidney. We have undertaken a photoaffinity cross-linking approach to elucidate the nature of the bimolecular interaction of PTH with the human (h) PTH1 Rc. Specifically, we have studied the region of the receptor that interacts with the midregion of PTH-(1-34), position 13, using a benzophenone-containing photoaffinity ligand, 125I-[Nle(8,18),Lys13(epsilon-pBz2),L-2-NaI23,Arg(26,2 7),Tyr34]bPTH-(1-34)NH2 (125I-K13). Using site-directed mutagenesis in combination with biochemical analysis, we have reduced our previously identified contact domain, 17 residues in the extracellular region of the receptor (173-189), to an 8-amino acid domain (182-189). Furthermore, we have found arginine 186 to be of critical importance to the interaction of the hPTH1 Rc with 125I-K13: modification of Arg186 to either lysine or alanine does not modify receptor avidity or signal transduction by the receptor, but eliminates cross-linking to 125I-K13.
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Affiliation(s)
- A E Adams
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA.
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Pellegrini M, Bisello A, Rosenblatt M, Chorev M, Mierke DF. Binding domain of human parathyroid hormone receptor: from conformation to function. Biochemistry 1998; 37:12737-43. [PMID: 9737850 DOI: 10.1021/bi981265h] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A 31 amino acid fragment of the extracellular N-terminus of the human G-protein coupled receptor for parathyroid hormone (PTH1R) has been structurally characterized by NMR and molecular dynamics simulations. The fragment PTH1R[168-198] includes residues 173-189, shown by photoaffinity cross-linking to be a contact domain with position 13 of parathyroid hormone (PTH). The structure of PTH1R[168-198], determined in a micellar solution of dodecylphosphocholine to mimic the membrane environment, consists of three alpha-helices, separated by a well-defined turn and a flexible region. The topological orientation of PTH1R[168-198] was determined from nitroxide-radical induced relaxation of NMR signals utilizing 5- and 16-doxylstearic acid. The C-terminal helix (residues 190-196), consisting of seven amino acids of the first transmembrane domain, is very hydrophobic and embedded in the lipid core. This helix is preceded by a well-defined turn, forming an approximate 90 degrees bend, placing the other helices (residues 169-176 and 180-189), both of which are amphipathic, on the surface of the micelle. In this orientation, many hydrophilic residues of the receptor, including Glu177, Arg179, Arg181, Glu182, Asp185, and Arg186, are projecting toward the solvent available to form complementary Coulombic interactions with the polar residues of the principal binding domain of the ligand (e.g., Arg25, Lys26, Lys27, Asp30, and His32). Given that the binding domain of PTH adopts an amphipathic alpha-helix which lies on the membrane, we visualize ligand binding as a two stage process involving a nonspecific hydrophobic interaction of amphipathic helices with the membrane, followed by two-dimensional diffusion leading to highly specific, ligand-receptor interaction.
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Affiliation(s)
- M Pellegrini
- Department of Molecular Pharmacology, Physiology, & Biotechnology, Division of Biology & Medicine, Brown University, Providence, Rhode Island 02912, USA
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Maretto S, Schievano E, Mammi S, Bisello A, Nakamoto C, Rosenblatt M, Chorev M, Peggion E. Conformational studies of a potent Leu11,D-Trp12-containing lactam-bridged parathyroid hormone-related protein-derived antagonist. J Pept Res 1998; 52:241-8. [PMID: 9774237 DOI: 10.1111/j.1399-3011.1998.tb01481.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Human parathyroid hormone-related protein (PTHrP) is expressed in various tissues where it acts as an endocrine/paracrine factor involved in cellular growth, differentiation and development of fetal skeleton. As for parathyroid hormone (PTH), which is the hormone responsible for regulation of extracellular calcium homeostasis, the N-terminal 1-34 fragment can reproduce the full spectrum of calciotropic activities inherent in full-length PTH. Truncation of six amino acid residues from the N-terminus of both hormone sequences generates 7-34 fragments which act as weak antagonists. Although PTH(7-34) is a pure antagonist, PTHrP(7-34) acts as partial agonist against the receptor shared by both hormones, the PTH/PTHrP receptor. In the current study, we analyzed the conformation of [Leu11,D-Trp12, Lys26,Asp30]PTHrP(7-34)NH2 (hybrid-lactam) in a 1:1 mixture of H2O/TFE-d3 at pH approximately equal to 4 by circular dichroism, nuclear magnetic resonance and distance geometry calculations. This weak antagonist (Kb = 650 nM) combines two modifications: Leu11,D-Trp12 (Kb = 5.1 nM), reported to eliminate partial agonism and enhance potency, and Lys26-Asp30 lactamization (Kb = 31 nM), aimed to stabilize the helical structure of the principal binding domain attributed to residues 25-34. The helical content in 30% trifluoroethanol is 88%, i.e., higher than the corresponding linear analog, and comprises the D-Trp12-Thr33 segment. This hybrid lactam contains a rigid helical segment spanning the 14-18 sequence followed by a hinge motif around Arg19-20, but the sequence 14-18 forms a stable helix. In all potent lactam-containing, PTHrP-derived agonists and antagonists studied so far, the dominant structural motif consists of two helical domains at the two ends of the sequence and of two hinge regions centered around Gly12-Lys13 and Arg19. The weakly active agonists and antagonists do not exhibit the "hinge" around position 19. These findings suggest that the presence and location of discrete hinge regions that connect the N- and C-terminal helices are essential for generating the bioactive conformation of ligands for the PTH/PTHrP receptor.
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Affiliation(s)
- S Maretto
- Department of Organic Chemistry, Biopolymer Research Center, University of Padova, Italy
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Bisello A, Adams AE, Mierke DF, Pellegrini M, Rosenblatt M, Suva LJ, Chorev M. Parathyroid hormone-receptor interactions identified directly by photocross-linking and molecular modeling studies. J Biol Chem 1998; 273:22498-505. [PMID: 9712875 DOI: 10.1074/jbc.273.35.22498] [Citation(s) in RCA: 162] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Direct mapping of the interface between parathyroid hormone (PTH) and its receptor (hPTH1-Rc) was carried out by photoaffinity scanning studies. Photoreactive analogs of PTH singularly substituted with a p-benzoylphenylalanine (Bpa) at each of the first six N-terminal positions have been prepared. Among these, the analog [Bpa1,Nle8,18,Arg13,26,27,L-2-Nal23,Tyr34]bPTH-(1-34)N H2 (Bpa1-PTH-(1-34)) displayed in vitro activity with potency similar to that of PTH-(1-34). The radioiodinated analog 125I-Bpa1-PTH-(1-34) cross-linked specifically to the hPTH1-Rc stably expressed in human embryonic kidney cells. A series of chemical and enzymatic digestions of the hPTH1-Rc-125I-Bpa1-PTH-(1-34) conjugate suggested that a methionine residue (either Met414 or Met425) within the contact domain hPTH1-Rc-(409-437), which includes the transmembrane helix 6 and part of the third extracellular loop, as the putative contact point. Site-directed mutagenesis (M414L or M425L) identified Met425 as the putative contact point. Molecular modeling of the hPTH1-Rc together with the NMR-derived high resolution structure of hPTH-(1-34), guided by the cross-linking data, strongly supports Met425, at the extracellular end of transmembrane helix 6, as the residue interacting with the N-terminal residue of the hPTH-(1-34). The photocross-linking and molecular modeling studies provide insight into the topologic arrangement of the receptor-ligand complex.
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Affiliation(s)
- A Bisello
- Division of Bone and Mineral Metabolism, Charles A. Dana and Thorndike Laboratories, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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Pellegrini M, Bisello A, Rosenblatt M, Chorev M, Mierke DF. Conformational studies of RS-66271, an analog of parathyroid hormone-related protein with pronounced bone anabolic activity. J Med Chem 1997; 40:3025-31. [PMID: 9301664 DOI: 10.1021/jm970181o] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Both the parathyroid hormone (PTH) and the functionally similar parathyroid hormone-related protein (PTHrP) have served as templates for the development of novel bone anabolic agents for the treatment of osteoporosis. The PTHrP analog RS-66271 (Vickery, B. H.; Avnur, Z.; Cheng Y.; Chiou, S.-S.; Leaffer, D.; Caulfield, J. P.; Kimmel, D. B.; Ho, T.; Krstenansky, J. L. J. Bone Miner. Res. 1996, 11, 1943-1951), in which the amino acids 22-31 have been substituted by the sequence E22-L-L-E-K-L-L-E-K-L31 (a model amphiphilic peptide), is a potent bone anabolic agent in vivo. Therefore, RS-66271 is a good candidate for structural analysis with the aim of developing a structure-activity relationship. The structural characterization described here was carried out in aqueous solution employing circular dichroism and nuclear magnetic resonance spectroscopy. We find that the incorporated amphiphilic decapeptide is indeed helical. In addition, it induces the adjacent residues, up to residue 16, to adopt the helical conformation. The helical domain, including residues 16-32, incorporates most of the previously identified principal receptor binding domain PTHrP(25-34). We discuss the relevance of the distinct and extensive helicity in light of the reduced in vitro receptor affinity/ activity and the enhanced in vivo bone anabolic efficacy of RS-66271.
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Affiliation(s)
- M Pellegrini
- Gustaf H. Carlson School of Chemistry, Clark University, Worcester, Massachusetts 01610, USA
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Mierke DF, Maretto S, Schievano E, DeLuca D, Bisello A, Mammi S, Rosenblatt M, Peggion E, Chorev M. Conformational studies of mono- and bicyclic parathyroid hormone-related protein-derived agonists. Biochemistry 1997; 36:10372-83. [PMID: 9265617 DOI: 10.1021/bi970771o] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Parathyroid hormone-related protein (PTHrP) is expressed in a wide variety of cells where it acts as an autocrine and/or paracrine factor involved in regulation of cellular growth, differentiation, and embryonic development. It may also play a physiological endocrine role in calcium transport across the placenta or during lactation. The N-terminal portion, PTHrP-(1-34), retains all the calciotropic parathyroid hormone-like activity and is a lead structure for the design of novel, bone anabolic agents for the treatment of bone disorders such as osteoporosis. To characterize the putative bioactive conformation, we have carried out a detailed structural analysis of a series of three conformationally constrained PTHrP-(1-34)-based mono- and bicyclic lactam-containing biologically active analogs: (III) The conformational properties were studied by circular dichroisim, nuclear magnetic resonance spectroscopy, distance geometry calculations, and molecular dynamic simulations in water/trifluoroethanol (TFE) mixtures. The helical content in water of both monocyclic analogs I and II is approximately 22%; that of the bicyclic analog III is approximately 40%. In 30% TFE, all analogs reached a maximal helical content of 80%, corresponding to 26 or 27 residues out of 34 in a helical conformation. High-resolution structures obtained with 50:50 TFE/water revealed that all three analogs display two helical domains and a hinge region around Gly12-Lys13. The highly potent mono- and bicyclic agonists I and III display a second hinge around Arg19-Arg20 which is shifted to Ser14-Asp17 in the weakly potent monocyclic agonist II. We suggest that the presence and localization of discrete hinges in the sequence together with the high propensity for helicity of the C-terminal sequence and the enhancement of helical nucleation at the N-terminal sequence are essential for generating a PTH/PTHrP receptor-compatible bioactive conformation.
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Affiliation(s)
- D F Mierke
- Department of Pharmacology and Molecular Toxicology, University of Massachusetts Medical School, 55 Lake Avenue North, Worcester, Massachusetts 01610, USA.
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Zhou AT, Bessalle R, Bisello A, Nakamoto C, Rosenblatt M, Suva LJ, Chorev M. Direct mapping of an agonist-binding domain within the parathyroid hormone/parathyroid hormone-related protein receptor by photoaffinity crosslinking. Proc Natl Acad Sci U S A 1997; 94:3644-9. [PMID: 9108031 PMCID: PMC20494 DOI: 10.1073/pnas.94.8.3644] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Parathyroid hormone (PTH) and PTH-related protein (PTHrP) are calciotropic hormones interacting with a shared seven-transmembrane domain G protein-coupled receptor, which is located predominantly in bone and kidney. To map the interface of the bimolecular interaction between hormone and receptor, we designed and radioiodinated a bioactive, photoreactive PTH agonist, (125)I-[Nle(8,18),Lys13(epsilon-p-(3-I-Bz)Bz),L-2-Nal(23),Arg(26,2 7),Tyr34] bPTH-(1-34)NH2 ((125)I-all-R-K13). This ligand contains a photoreactive benzophenone moiety attached to the side chain of Lys13. All other lysyl residues are substituted by argynyls. The analog photocrosslinks specifically to the recombinant hPTH/PTHrP receptor stably transfected into human embryonic kidney cells (HEK-293/C-21 cells, approximately 400,000 receptors per cell), generating a diffuse approximately 87-kDa band on SDS/PAGE autoradiography. To identify the "contact domain" within the hPTH/PTHrP receptor involved in binding of (125)I-all-R-K13, the radiolabeled band containing the ligand-receptor conjugate was subjected to chemical and enzymatic cleavage. Two independent pathways of sequential digestion were used: Route A, lysyl endopeptidase C, then endo-N-glycosidase F, followed by cyanogen bromide; Route B, cyanogen bromide followed by endo-N-glycosydase F. The identified domain is in contact with position 13 in (125)I-all-R-K13 and corresponds to amino acids 173-189 of the hPTH/PTHrP receptor, located at the C-terminal region of the N-terminal extracellular domain.
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Affiliation(s)
- A T Zhou
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, USA
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