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Identification of a nanomolar affinity α-synuclein fibril imaging probe by ultra-high throughput in silico screening.

ABSTRACT: Small molecules that bind with high affinity and specificity to fibrils of the α-synuclein (αS) protein have the potential to serve as positron emission tomography (PET) imaging probes to aid in the diagnosis of Parkinson's disease and related synucleinopathies. To identify such molecules, we employed an ultra-high throughput in silico screening strategy using idealized pseudo-ligands termed exemplars to identify compounds for experimental binding studies. For the top hit from this screen, we used photo-crosslinking to confirm its binding site and studied the structure-activity relationship of its analogs to develop multiple molecules with nanomolar affinity for αS fibrils and moderate specificity for αS over Aβ fibrils. Lastly, we demonstrated the potential of the lead analog as an imaging probe by measuring binding to αS-enriched homogenates from mouse brain tissue using a radiolabeled analog of the identified molecule. This study demonstrates the validity of our powerful new approach to the discovery of PET probes for challenging molecular targets.

SUBMITTER: Ferrie JJ

PROVIDER: S-EPMC8047729 | biostudies-literature |

REPOSITORIES: biostudies-literature

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α-Helical peptidic scaffolds to target α-synuclein toxic species with nanomolar affinity.

Project description:α-Synuclein aggregation is a key driver of neurodegeneration in Parkinson's disease and related syndromes. Accordingly, obtaining a molecule that targets α-synuclein toxic assemblies with high affinity is a long-pursued objective. Here, we exploit the biophysical properties of toxic oligomers and amyloid fibrils to identify a family of α-helical peptides that bind to these α-synuclein species with low nanomolar affinity, without interfering with the monomeric functional protein. This activity is translated into a high anti-aggregation potency and the ability to abrogate oligomer-induced cell damage. Using a structure-guided search we identify a human peptide expressed in the brain and the gastrointestinal tract with analogous binding, anti-aggregation, and detoxifying properties. The chemical entities we describe here may represent a therapeutic avenue for the synucleinopathies and are promising tools to assist diagnosis by discriminating between native and toxic α-synuclein species.

| S-EPMC8213730 | biostudies-literature

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| S-EPMC6451039 | biostudies-literature

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| S-EPMC2244645 | biostudies-literature

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Evidence for copper-dioxygen reactivity during alpha-synuclein fibril formation.

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| S-EPMC2880511 | biostudies-literature

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Project description:Synucleinopathies like Parkinson's disease are neurodegenerative diseases which are associated with the deposition of fibrillar aggregates of the endogenous protein α-synuclein (α-syn). The inhibition of the elongation of α-syn fibrils is of great scientific interest and an option in the design of therapeutic strategies. Previously, we developed a disulfide-containing mutant of α-syn, called CC48, which inhibits fibril elongation by blocking of fibril ends. Surprisingly, wildtype (WT) α-syn molecules supported the blocked state, and a fusion of CC48 with WT α-syn, denoted WT-CC48, exhibited increased inhibitory potential. Here, we studied which regions of WT-CC48 are responsible for the strong inhibitory effect. To this end, we investigated a set of truncated versions of WT-CC48 by kinetic elongation assays, density gradient centrifugation, and atomic force microscopy. We show that in both the WT and the CC48 part of the fusion construct the hairpin region (residue 32-60) and NAC region (61-95), but not N- and C-terminal regions, are required for strong inhibition of fibril elongation. The required regions correspond to the segments forming the β-sheet core of α-syn fibrils. As α-syn fibrils typically consist of two protofilaments, the dimeric construct WT-CC48 provides the critical regions sufficient to cover the full β-sheetcore interface exposed at the fibril end, which can explain its high inhibitory efficiency. We suggest a mechanistic model of CC48-mediated inhibition of fibril elongation in which CC48 and WT α-syn cooperatively form an oligomer-like cap at the amyloid fibril end.

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Project description: Not available

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Project description:The accumulation and propagation of misfolded ?-synuclein (?-Syn) is a central feature of Parkinson's disease and other synucleinopathies. Molecular compatibility between a fibrillar seed and its native protein state is a major determinant of amyloid self-replication. We show that cross-seeded aggregation of human (Hu) and mouse (Ms) ?-Syn is bidirectionally restricted. Although fibrils formed by Hu-Ms-?-Syn chimeric mutants can overcome this inhibition in cell-free systems, sequence homology poorly predicts their efficiency in inducing ?-Syn pathology in primary neurons or after intracerebral injection into wild-type mice. Chimeric ?-Syn fibrils demonstrate enhanced or reduced pathogenicities compared with wild-type Hu- or Ms-?-Syn fibrils. Furthermore, ?-Syn mutants induced to polymerize by fibrillar seeds inherit the functional properties of their template, suggesting that transferable pathogenic and non-pathogenic states likely influence the initial engagement between exogenous ?-Syn seeds and endogenous neuronal ?-Syn. Thus, transmission of synucleinopathies is regulated by biological processes in addition to molecular compatibility.

| S-EPMC5087609 | biostudies-literature

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