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Chisholm TS, Hunter CA. A closer look at amyloid ligands, and what they tell us about protein aggregates. Chem Soc Rev 2024; 53:1354-1374. [PMID: 38116736 DOI: 10.1039/d3cs00518f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 12/21/2023]
Abstract
The accumulation of amyloid fibrils is characteristic of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease. Detecting these fibrils with fluorescent or radiolabelled ligands is one strategy for diagnosing and better understanding these diseases. A vast number of amyloid-binding ligands have been reported in the literature as a result. To obtain a better understanding of how amyloid ligands bind, we have compiled a database of 3457 experimental dissociation constants for 2076 unique amyloid-binding ligands. These ligands target Aβ, tau, or αSyn fibrils, as well as relevant biological samples including AD brain homogenates. From this database significant variation in the reported dissociation constants of ligands was found, possibly due to differences in the morphology of the fibrils being studied. Ligands were also found to bind to Aβ(1-40) and Aβ(1-42) fibrils with similar affinities, whereas a greater difference was found for binding to Aβ and tau or αSyn fibrils. Next, the binding of ligands to fibrils was shown to be largely limited by the hydrophobic effect. Some Aβ ligands do not fit into this hydrophobicity-limited model, suggesting that polar interactions can play an important role when binding to this target. Finally several binding site models were outlined for amyloid fibrils that describe what ligands target what binding sites. These models provide a foundation for interpreting and designing site-specific binding assays.
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Affiliation(s)
- Timothy S Chisholm
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1 EW, UK.
| | - Christopher A Hunter
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1 EW, UK.
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Abstract
Fibrillar protein aggregates are characteristic of neurodegenerative diseases but represent difficult targets for ligand design, because limited structural information about the binding sites is available. Ligand-based virtual screening has been used to develop a computational method for the selection of new ligands for Aβ(1-42) fibrils, and five new ligands have been experimentally confirmed as nanomolar affinity binders. A database of ligands for Aβ(1-42) fibrils was assembled from the literature and used to train models for the prediction of dissociation constants based on chemical structure. The virtual screening pipeline consists of three steps: a molecular property filter based on charge, molecular weight, and logP; a machine learning model based on simple chemical descriptors; and machine learning models that use field points as a 3D description of shape and surface properties in the Forge software. The three-step pipeline was used to virtually screen 698 million compounds from the ZINC15 database. From the top 100 compounds with the highest predicted affinities, 46 compounds were experimentally investigated by using a thioflavin T fluorescence displacement assay. Five new Aβ(1-42) ligands with dissociation constants in the range 20-600 nM and novel structures were identified, demonstrating the power of this ligand-based approach for discovering new structurally unique, high-affinity amyloid ligands. The experimental hit rate using this virtual screening approach was 10.9%.
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Affiliation(s)
- Timothy S Chisholm
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
| | - Mark Mackey
- Cresset, New Cambridge House, Bassingbourn Road, Litlington SG8 0SS, Cambridgeshire, U.K
| | - Christopher A Hunter
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K
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Kambanis L, Chisholm TS, Kulkarni SS, Payne RJ. Rapid one-pot iterative diselenide-selenoester ligation using a novel coumarin-based photolabile protecting group. Chem Sci 2021; 12:10014-10021. [PMID: 34349969 PMCID: PMC8317654 DOI: 10.1039/d1sc02781f] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 06/24/2021] [Indexed: 11/21/2022] Open
Abstract
The development of an iterative one-pot peptide ligation strategy is described that capitalises on the rapid and efficient nature of the diselenide–selenoester ligation reaction, together with photodeselenisation chemistry. This ligation strategy hinged on the development of a novel photolabile protecting group for the side chain of selenocysteine, namely the 7-diethylamino-3-methyl coumarin (DEAMC) moiety. Deprotection of this DEAMC group can be effected in a mild, reagent-free manner using visible light (λ = 450 nm) without deleterious deselenisation of selenocysteine residues, thus enabling a subsequent ligation reaction without purification. The use of this DEAMC-protected selenocysteine in iterative DSL chemistry is highlighted through the efficient one-pot syntheses of 60- and 80-residue fragments of mucin-1 as well as apolipoprotein CIII in just 2–4 hours. A method for the rapid one-pot iterative assembly of proteins via diselenide–selenoester ligation (DSL) chemistry is described that capitalises on a novel coumarin-based photolabile protecting group for selenocysteine.![]()
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Affiliation(s)
- Lucas Kambanis
- School of Chemistry, The University of Sydney Sydney NSW 2006 Australia.,Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Sydney Sydney NSW 2006 Australia
| | - Timothy S Chisholm
- School of Chemistry, The University of Sydney Sydney NSW 2006 Australia.,Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Sydney Sydney NSW 2006 Australia
| | - Sameer S Kulkarni
- School of Chemistry, The University of Sydney Sydney NSW 2006 Australia.,Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Sydney Sydney NSW 2006 Australia
| | - Richard J Payne
- School of Chemistry, The University of Sydney Sydney NSW 2006 Australia.,Australian Research Council Centre of Excellence for Innovations in Peptide and Protein Science, The University of Sydney Sydney NSW 2006 Australia
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Sanna E, Rodrigues M, Fagan SG, Chisholm TS, Kulenkampff K, Klenerman D, Spillantini MG, Aigbirhio FI, Hunter CA. Mapping the binding site topology of amyloid protein aggregates using multivalent ligands. Chem Sci 2021; 12:8892-8899. [PMID: 34257890 PMCID: PMC8246084 DOI: 10.1039/d1sc01263k] [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] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 05/19/2021] [Indexed: 11/21/2022] Open
Abstract
A key process in the development of neurodegenerative diseases such as Alzheimer's and Parkinson's diseases is the aggregation of proteins to produce fibrillary aggregates with a cross β-sheet structure, amyloid. The development of reagents that can bind these aggregates with high affinity and selectivity has potential for early disease diagnosis. By linking two benzothiazole aniline (BTA) head groups with different length polyethylene glycol (PEG) spacers, fluorescent probes that bind amyloid fibrils with low nanomolar affinity have been obtained. Dissociation constants measured for interaction with Aβ, α-synuclein and tau fibrils show that the length of the linker determines binding affinity and selectivity. These compounds were successfully used to image α-synuclein aggregates in vitro and in the post-mortem brain tissue of patients with Parkinson's disease. The results demonstrate that multivalent ligands offer a powerful approach to obtain high affinity, selective reagents to bind the fibrillary aggregates that form in neurodegenerative disease. Multivalent ligands offer a powerful approach to obtain high affinity reagents to bind the aggregates that form in neurodegenerative disease. Selectivity for different proteins was achieved by using different linkers to connect the head groups.![]()
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Affiliation(s)
- Elena Sanna
- Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
| | - Margarida Rodrigues
- Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
| | - Steven G Fagan
- Department of Clinical Neurosciences, Clifford Allbutt Building, University of Cambridge Cambridge CB2 0AH UK
| | - Timothy S Chisholm
- Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
| | - Klara Kulenkampff
- Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
| | - David Klenerman
- Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
| | - Maria Grazia Spillantini
- Department of Clinical Neurosciences, Clifford Allbutt Building, University of Cambridge Cambridge CB2 0AH UK
| | - Franklin I Aigbirhio
- Department of Clinical Neuroscience, Wolfson Brain Imaging Centre, University of Cambridge CB2 0QQ UK
| | - Christopher A Hunter
- Department of Chemistry, University of Cambridge Lensfield Road Cambridge CB2 1EW UK
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Chisholm TS, Kulkarni SS, Hossain KR, Cornelius F, Clarke RJ, Payne RJ. Peptide Ligation at High Dilution via Reductive Diselenide-Selenoester Ligation. J Am Chem Soc 2019; 142:1090-1100. [DOI: 10.1021/jacs.9b12558] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
| | - Sameer S. Kulkarni
- School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
| | | | - Flemming Cornelius
- Department of Biomedicine, University of Aarhus, DK-8000 Aarhus C, Denmark
| | - Ronald J. Clarke
- School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
- The University of Sydney Nano Institute, Sydney, NSW 2006, Australia
| | - Richard J. Payne
- School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia
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Abstract
Native chemical ligation (NCL) combined with desulfurization chemistry has revolutionized the way in which large polypeptides and proteins are accessed by chemical synthesis. Herein, we outline the use of flow chemistry for the ligation-based assembly of polypeptides. We also describe the development of a novel photodesulfurization transformation that, when coupled with flow NCL, enables efficient access to native polypeptides on time scales up to 2 orders of magnitude faster than current batch NCL-desulfurization methods. The power of the new ligation-photodesulfurization flow platform is showcased through the rapid synthesis of the 36 residue clinically approved HIV entry inhibitor enfuvirtide and the peptide diagnostic agent somatorelin.
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Affiliation(s)
- Timothy S Chisholm
- School of Chemistry , The University of Sydney , Sydney , NSW 2006 , Australia
| | - Daniel Clayton
- School of Chemistry , The University of Sydney , Sydney , NSW 2006 , Australia
| | - Luke J Dowman
- School of Chemistry , The University of Sydney , Sydney , NSW 2006 , Australia
| | - Jessica Sayers
- School of Chemistry , The University of Sydney , Sydney , NSW 2006 , Australia
| | - Richard J Payne
- School of Chemistry , The University of Sydney , Sydney , NSW 2006 , Australia
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