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Zheng Q, Carty SN, Lazo ND. Helix Dipole and Membrane Electrostatics Delineate Conformational Transitions in the Self-Assembly of Amyloidogenic Peptides. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:8389-8397. [PMID: 32628488 PMCID: PMC8095063 DOI: 10.1021/acs.langmuir.0c00723] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The self-assembly of amyloidogenic peptides on membrane surfaces is associated with the death of neurons and β-cells in Alzheimer's disease and type 2 diabetes, respectively. The early events of self-assembly in vivo are not known, but there is increasing evidence for the importance of the α-helix. To test the hypothesis that electrostatic interactions involving the helix dipole play a key role in membrane-mediated peptide self-assembly, we studied IAPP[11-25(S20G)-NH2] (R11LANFLVHSGNNFGA25-NH2), which under certain conditions self-assembles in hydro to form β-sheet assemblies through an α-helix-containing intermediate. In the presence of small unilamellar vesicles composed solely of zwitterionic lipids, the peptide does not self-assemble presumably because of the absence of stabilizing electrostatic interactions between the membrane surface and the helix dipole. In the presence of vesicles composed solely of anionic lipids, the peptide forms a long-lived α-helix presumably stabilized by dipole-dipole interactions between adjacent helix dipoles. This helix represents a kinetic trap that inhibits β-sheet formation. Intriguingly, when the amount of anionic lipids was decreased to mimic the ratio of zwitterionic and anionic lipids in cells, the α-helix was short-lived and underwent an α-helix to β-sheet conformational transition. Our work suggests that the helix dipole and membrane electrostatics delineate the conformational transitions occurring along the self-assembly pathway to the amyloid.
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Affiliation(s)
- Qiuchen Zheng
- Carlson School of Chemistry and Biochemistry, Clark University, 950 Main Street, Worcester, Massachusetts 01610, United States
| | - Senegal N Carty
- Carlson School of Chemistry and Biochemistry, Clark University, 950 Main Street, Worcester, Massachusetts 01610, United States
| | - Noel D Lazo
- Carlson School of Chemistry and Biochemistry, Clark University, 950 Main Street, Worcester, Massachusetts 01610, United States
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Nguyen PT, Zottig X, Sebastiao M, Bourgault S. Role of Site-Specific Asparagine Deamidation in Islet Amyloid Polypeptide Amyloidogenesis: Key Contributions of Residues 14 and 21. Biochemistry 2017; 56:3808-3817. [PMID: 28665109 DOI: 10.1021/acs.biochem.7b00209] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Deamidation of an asparagine residue is a spontaneous non-enzymatic post-translational modification that results in the conversion of asparagine into a mixture of aspartic acid and isoaspartic acid. This chemical conversion modulates protein conformation and physicochemical properties, which could lead to protein misfolding and aggregation. In this study, we investigated the effects of site-specific Asn deamidation on the amyloidogenicity of the aggregation-prone peptide islet amyloid polypeptide (IAPP). IAPP is a 37-residue peptidic hormone whose deposition as insoluble amyloid fibrils is closely associated with type 2 diabetes. Asn residues were successively substituted with an Asp or isoAsp, and amyloid formation was evaluated by a thioflavin T fluorescence assay, circular dichroism spectroscopy, atomic force microscopy, and transmission electron microscopy. Whereas deamidation at position 21 inhibited IAPP conformational conversion and amyloid formation, the N14D mutation accelerated self-assembly and led to the formation of long and thick amyloid fibrils. In contrast, IAPP was somewhat tolerant to the successive deamidation of Asn residues 22, 31, and 35. Interestingly, a small molar ratio of IAPP deamidated at position 14 promoted the formation of nucleating species and the elongation from unmodified IAPP. Besides, using the rat pancreatic β cell line INS-1E, we observed that site-specific deamidation did not significantly alter IAPP-induced toxicity. These data indicate that Asn deamidation can modulate IAPP amyloid formation and fibril morphology and that the site of modification plays a critical role. Above all, this study reinforces the notion that IAPP amyloidogenesis is governed by precise intermolecular interactions involving specific Asn side chains.
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Affiliation(s)
- Phuong Trang Nguyen
- Department of Chemistry, University of Québec in Montreal , C.P. 8888, Succursale Centre-Ville, Montreal H3C 3P8, Canada.,Quebec Network for Research on Protein Function, Engineering, and Applications, PROTEO
| | - Ximena Zottig
- Department of Chemistry, University of Québec in Montreal , C.P. 8888, Succursale Centre-Ville, Montreal H3C 3P8, Canada.,Quebec Network for Research on Protein Function, Engineering, and Applications, PROTEO
| | - Mathew Sebastiao
- Department of Chemistry, University of Québec in Montreal , C.P. 8888, Succursale Centre-Ville, Montreal H3C 3P8, Canada.,Quebec Network for Research on Protein Function, Engineering, and Applications, PROTEO
| | - Steve Bourgault
- Department of Chemistry, University of Québec in Montreal , C.P. 8888, Succursale Centre-Ville, Montreal H3C 3P8, Canada.,Quebec Network for Research on Protein Function, Engineering, and Applications, PROTEO
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Qiao Q, Qi R, Wei G, Huang X. Dynamics of the conformational transitions during the dimerization of an intrinsically disordered peptide: a case study on the human islet amyloid polypeptide fragment. Phys Chem Chem Phys 2016; 18:29892-29904. [DOI: 10.1039/c6cp05590g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Dimerization pathways of the human islet amyloid polypeptide fragment are elucidated from extensive molecular dynamics simulations.
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Affiliation(s)
- Qin Qiao
- Hefei National Laboratory for Physical Sciences at the Microscale and Collaborative Innovation Center of Chemistry for Energy Materials (iChEM)
- University of Science and Technology of China
- Hefei
- China
| | - Ruxi Qi
- State Key Laboratory of Surface Physics
- Key Laboratory for Computational Physical Sciences (MOE)
- and Department of Physics
- Fudan University
- Shanghai
| | - Guanghong Wei
- State Key Laboratory of Surface Physics
- Key Laboratory for Computational Physical Sciences (MOE)
- and Department of Physics
- Fudan University
- Shanghai
| | - Xuhui Huang
- Department of Chemistry
- The Hong Kong University of Science and Technology
- Kowloon
- Hong Kong
- Division of Biomedical Engineering
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Qi R, Luo Y, Ma B, Nussinov R, Wei G. Conformational distribution and α-helix to β-sheet transition of human amylin fragment dimer. Biomacromolecules 2014; 15:122-31. [PMID: 24313776 PMCID: PMC6429924 DOI: 10.1021/bm401406e] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Experiments suggested that the fibrillation of the 11-25 fragment (hIAPP(11-25)) of human islet amyloid polypeptide (hIAPP or amylin) involves the formation of transient α-helical intermediates, followed by conversion to β-sheet-rich structure. However, atomic details of α-helical intermediates and the transition mechanism are mostly unknown. We investigated the structural properties of the monomer and dimer in atomistic detail by replica exchange molecular dynamics (REMD) simulations. Transient α-helical monomers and dimers were both observed in the REMD trajectories. Our calculated H(α) chemical shifts based on the monomer REMD run are in agreement with the solution-state NMR experimental observations. Multiple 300 ns MD simulations at 310 K show that α-helix-to-β-sheet transition follows two mechanisms: the first involved direct transition of the random coil part of the helical conformation into antiparallel β-sheet, and in the second, the α-helical conformation unfolded and converted into antiparallel β-sheet. In both mechanisms, the α-helix-to-β-sheet transition occurred via random coil, and the transition was accompanied by an increase of interpeptide contacts. In addition, our REMD simulations revealed different temperature dependencies of helical and β-structures. Comparison with experimental data suggests that the propensity for hIAPP(11-25) to form α-helices and amyloid structures is concentration- and temperature-dependent.
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Affiliation(s)
- Ruxi Qi
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (MOE), and Department of Physics, Fudan University , Shanghai, China
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Liu G, Gaines JC, Robbins KJ, Lazo ND. Kinetic profile of amyloid formation in the presence of an aromatic inhibitor by nuclear magnetic resonance. ACS Med Chem Lett 2012; 3:856-9. [PMID: 24900390 DOI: 10.1021/ml300147m] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 08/28/2012] [Indexed: 11/29/2022] Open
Abstract
The self-assembly of amyloid proteins into β-sheet rich assemblies is associated with human amyloidoses including Alzheimer's disease, Parkinson's disease, and type 2 diabetes. An attractive therapeutic strategy therefore is to develop small molecules that would inhibit protein self-assembly. Natural polyphenols are potential inhibitors of β-sheet formation. How these compounds affect the kinetics of self-assembly studied by thioflavin T (ThT) fluorescence is not understood primarily because their presence interferes with ThT fluorescence. Here, we show that by plotting peak intensities from nuclear magnetic resonance (NMR) against incubation time, kinetic profiles in the presence of the polyphenol can be obtained from which kinetic parameters of self-assembly can be easily determined. In applying this technique to the self-assembly of the islet amyloid polypeptide in the presence of curcumin, a biphenolic compound found in turmeric, we show that the kinetic profile is atypical in that it shows a prenucleation period during which there is no observable decrease in NMR peak intensities.
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Affiliation(s)
- Gai Liu
- Carlson School of Chemistry
and Biochemistry, Clark University, 950
Main Street, Worcester, Massachusetts
01610, United States
| | - Jennifer C. Gaines
- Carlson School of Chemistry
and Biochemistry, Clark University, 950
Main Street, Worcester, Massachusetts
01610, United States
| | - Kevin J. Robbins
- Carlson School of Chemistry
and Biochemistry, Clark University, 950
Main Street, Worcester, Massachusetts
01610, United States
| | - Noel D. Lazo
- Carlson School of Chemistry
and Biochemistry, Clark University, 950
Main Street, Worcester, Massachusetts
01610, United States
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