Dustin J. Covell

Solid-state NMR structure of a pathogenic fibril of full-length human alpha-synuclein.

Misfolded α-synuclein amyloid fibrils are the principal components of Lewy bodies and neurites, hallmarks of Parkinsons disease (PD). We present a high-resolution structure of an α-synuclein fibril, in a form that induces robust pathology in primary neuronal culture, determined by solid-state NMR spectroscopy and validated by EM and X-ray fiber diffraction. Over 200 unique long-range distance restraints define a consensus structure with common amyloid features including parallel, in-register β-sheets and hydrophobic-core residues, and with substantial complexity arising from diverse structural features including an intermolecular salt bridge, a glutamine ladder, close backbone interactions involving small residues, and several steric zippers stabilizing a new orthogonal Greek-key topology. These characteristics contribute to the robust propagation of this fibril form, as supported by the structural similarity of early-onset-PD mutants. The structure provides a framework for understanding the interactions of α-synuclein with other proteins and small molecules, to aid in PD diagnosis and treatment.

A chiral Lewis acid strategy for enantioselective allylic C-H oxidation.

C–H oxidation reactions have the potential to significantly streamline synthetic processes. However, to be useful for the synthesis of complex molecules, these reactions must proceed with high levels of chemo-, regio-, and stereoselectivity, Chiral bisoxazoline/copper-catalyzed systems have shown promising levels of asymmetric induction in the enantioselective allylic C–H esterification of symmetrical, cyclic olefins. Application of these systems to complex substrates is limited by a lack of chemo- and regioselectivity as well as the need to use a large excess of reactant (4 to 10 equiv).[1] A direct allylic C–H oxidation route would significantly increase the efficiency of producing chiral allylic esters; their syntheses generally require lengthy sequences of functional-group manipulations from preoxidized materials.[2,3]

Sequential allylic C-H amination/vinylic C-H arylation: a strategy for unnatural amino acid synthesis from α-olefins.

Tandem reaction sequences that selectively convert multiple C-H bonds of abundant hydrocarbon feedstocks to functionalized materials enable rapid buildup of molecular complexity in an economical way. A tandem C-H amination/vinylic C-H arylation reaction sequence is described under Pd(II)/sulfoxide-catalysis that furnishes a wide range of α- and β-homophenylalanine precursors from commodity α-olefins and readily available aryl boronic acids. General routes to enantiopure amino acid esters and densely functionalized homophenylalanine derivatives are demonstrated.

Molecular and Biological Compatibility with Host Alpha-Synuclein Influences Fibril Pathogenicity

The accumulation and propagation of misfolded α-synuclein (α-Syn) is a central feature of Parkinsons 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) α-Syn is bidirectionally restricted. Although fibrils formed by Hu-Ms-α-Syn chimeric mutants can overcome this inhibition in cell-free systems, sequence homology poorly predicts their efficiency in inducing α-Syn pathology in primary neurons or after intracerebral injection into wild-type mice. Chimeric α-Syn fibrils demonstrate enhanced or reduced pathogenicities compared with wild-type Hu- or Ms-α-Syn fibrils. Furthermore, α-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 α-Syn seeds and endogenous neuronal α-Syn. Thus, transmission of synucleinopathies is regulated by biological processes in addition to molecular compatibility.

Cellular milieu imparts distinct pathological α-synuclein strains in α-synucleinopathies

In Lewy body diseases—including Parkinson’s disease, without or with dementia, dementia with Lewy bodies, and Alzheimer’s disease with Lewy body co-pathology1—α-synuclein (α-Syn) aggregates in neurons as Lewy bodies and Lewy neurites2. By contrast, in multiple system atrophy α-Syn accumulates mainly in oligodendrocytes as glial cytoplasmic inclusions (GCIs)3. Here we report that pathological α-Syn in GCIs and Lewy bodies (GCI-α-Syn and LB-α-Syn, respectively) is conformationally and biologically distinct. GCI-α-Syn forms structures that are more compact and it is about 1,000-fold more potent than LB-α-Syn in seeding α-Syn aggregation, consistent with the highly aggressive nature of multiple system atrophy. GCI-α-Syn and LB-α-Syn show no cell-type preference in seeding α-Syn pathology, which raises the question of why they demonstrate different cell-type distributions in Lewy body disease versus multiple system atrophy. We found that oligodendrocytes but not neurons transform misfolded α-Syn into a GCI-like strain, highlighting the fact that distinct α-Syn strains are generated by different intracellular milieus. Moreover, GCI-α-Syn maintains its high seeding activity when propagated in neurons. Thus, α-Syn strains are determined by both misfolded seeds and intracellular environments.Distinct strains of misfolded α-synuclein proteins, which aggregate in neurons in Lewy body diseases or in oligodendrocytes in multiple system atrophy, are formed as a consequence of differences between intracellular environments.

Novel conformation-selective alpha-synuclein antibodies raised against different in vitro fibril forms show distinct patterns of Lewy pathology in Parkinson's disease

The aim of this study was to test the hypothesis that different conformations of misfolded α‐synuclein (α‐syn) are present in Parkinsons disease (PD) brain.