Site-specific dynamic nuclear polarization of hydration water as a generally applicable approach to monitor protein aggregation

Pavlova, Ànna; McCarney, Evan R.; Peterson, Dylan W.; Dahlquist, Frederick W.; Lew, John I.; Han, Songi

doi:10.1039/b906101k

Cited by 44 publications

(72 citation statements)

References 37 publications

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“…4C) protein−water HB relaxation times are longer around the fibrillated peptides, suggesting that both rotational and translational diffusions are reduced around the amyloid assembly. A reduction in the local dynamics of water molecules around the core domain in tau fibers (in particular around the residue Cys322) has also been observed in Overhauser dynamic nuclear polarization NMR experiments (39). Therefore, we propose that it is the water dynamics not around the core domain but around the fuzzy coat that is increased when tau has formed amyloid fibers, resulting in the average increase in water dynamics observed in our neutron experiments.…”

Section: Discussionsupporting

confidence: 48%

Hydration water mobility is enhanced around tau amyloid fibers

Fichou

Schirò

Gallat

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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The paired helical filaments (PHF) formed by the intrinsically disordered human protein tau are one of the pathological hallmarks of Alzheimer disease. PHF are fibers of amyloid nature that are composed of a rigid core and an unstructured fuzzy coat. The mechanisms of fiber formation, in particular the role that hydration water might play, remain poorly understood. We combined protein deuteration, neutron scattering, and all-atom molecular dynamics simulations to study the dynamics of hydration water at the surface of fibers formed by the full-length human protein htau40. In comparison with monomeric tau, hydration water on the surface of tau fibers is more mobile, as evidenced by an increased fraction of translationally diffusing water molecules, a higher diffusion coefficient, and increased mean-squared displacements in neutron scattering experiments. Fibers formed by the hexapeptide 306 VQIVYK 311 were taken as a model for the tau fiber core and studied by molecular dynamics simulations, revealing that hydration water dynamics around the core domain is significantly reduced after fiber formation. Thus, an increase in water dynamics around the fuzzy coat is proposed to be at the origin of the experimentally observed increase in hydration water dynamics around the entire tau fiber. The observed increase in hydration water dynamics is suggested to promote fiber formation through entropic effects. Detection of the enhanced hydration water mobility around tau fibers is conjectured to potentially contribute to the early diagnosis of Alzheimer patients by diffusion MRI.hydration water | tau protein | amyloid fibers | intrinsically disordered proteins | neutron scattering A myloid fibers are the most stable forms of ordered protein aggregates. They have attracted much attention because of their implication in so-called conformational diseases, which include a variety of neurodegenerative disorders (1). Consequently, means of hindering or reversing fiber formation are actively researched (2). Pathological fibers are often formed by intrinsically disordered proteins (IDPs) that lack a well-defined 3D structure in their native state and are best described by an ensemble of different conformations (3). The human protein tau is an IDP that normally regulates microtubule stability in neurons. When tau aggregates, it forms paired helical filaments (PHF) that are one of the two histological hallmarks of Alzheimer disease (AD) (4, 5). As yet, and despite considerable effort over the past 30 y, the understanding of tau fibrillation in AD and other taupathies remains largely incomplete (6). The longest human tau isoform, htau40, is composed of 441 amino acid residues and is organized into several domains (see Fig. 1), including the repeat domains R1−R4 (residues 244-369) that constitute, together with the P1 and P2 domains, the microtubule binding regions (7). Essential for the nucleation of tau fibers is the presence of hexapeptides ( 275 VQIINK 280 and 306 VQIVYK 311 ) in R2 and R3 (8) that have a high propensity t...

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Section: Discussionsupporting

confidence: 48%

Hydration water mobility is enhanced around tau amyloid fibers

Fichou

Schirò

Gallat

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…The ODNP measurement was used to derive (as discussed in SI Overview of the ODNP Technique in detail) the translational correlation time, τ, of water within ∼1 nm of the R1 label tethered to the protein surface, together with two relaxivity parameters termed "k σ " and "k ρ " that report on contributions from freely diffusing water near the protein surface and bound water to the protein surface on the timescale of a few nanoseconds or longer, respectively. Thus, when a characteristic dispersion, i.e., an increased heterogeneity, of surface water diffusivity develops on the Δtau187 surface, as it transforms from monomeric species to oligomeric and larger fibrillar species, this indirectly shows that Δtau187 is undergoing structural transformation (18). However, ODNP analysis alone cannot differentiate between intraprotein or interprotein structural changes, nor does it offer population information.…”

Section: Significancementioning

confidence: 99%

“…We have previously established a broadly applicable spectroscopic method, Overhauser dynamic nuclear polarizationenhanced NMR relaxometry (ODNP) (16,17), to probe changes in translational diffusivity of local water within 1 nm of nitroxide radical-based electron spin labels tethered to specific protein residues, and successfully reported on the study of protein folding, protein aggregation, and conformational changes of globular and membrane protein segments (18)(19)(20)(21). ODNP has revealed increased heterogeneity, i.e., dispersion, in local water diffusivity on the surface of a folded protein, compared with its unfolded counterpart or folding intermediate (20).…”

mentioning

confidence: 99%

Protein structural and surface water rearrangement constitute major events in the earliest aggregation stages of tau

Pavlova

Cheng

Kinnebrew

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Protein aggregation plays a critical role in the pathogenesis of neurodegenerative diseases, and the mechanism of its progression is poorly understood. Here, we examine the structural and dynamic characteristics of transiently evolving protein aggregates under ambient conditions by directly probing protein surface water diffusivity, local protein segment dynamics, and interprotein packing as a function of aggregation time, along the third repeat domain and C terminus of Δtau187 spanning residues 255-441 of the longest isoform of human tau. These measurements were achieved with a set of highly sensitive magnetic resonance tools that rely on sitespecific electron spin labeling of Δtau187. Within minutes of initiated aggregation, the majority of Δtau187 that is initially homogeneously hydrated undergoes structural transformations to form partially structured aggregation intermediates. This is reflected in the dispersion of surface water dynamics that is distinct around the third repeat domain, found to be embedded in an intertau interface, from that of the solvent-exposed C terminus. Over the course of hours and in a rate-limiting process, a majority of these aggregation intermediates proceed to convert into stable β-sheet structured species and maintain their stacking order without exchanging their subunits. The population of β-sheet structured species is >5% within 5 min of aggregation and gradually grows to 50-70% within the early stages of fibril formation, while they mostly anneal block-wisely to form elongated fibrils. Our findings suggest that the formation of dynamic aggregation intermediates constitutes a major event occurring in the earliest stages of tau aggregation that precedes, and likely facilitates, fibril formation and growth.biological water | soluble oligomers | amyloid formation | site-directed spin labeling | Alzheimer's disease

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“…The DNP parameter therefore contains 'water accessibility' information in terms of local dynamics of water-label collisions (n) and in terms of exchange between local water and bulk water (f). Up to date, biochemical DNP studies focused on monitoring protein aggregation [22] or hydration dynamics in synthetic soft matter [23][24][25][26] and water soluble proteins [27,28]. The hydration dynamics studies made use of the theoretical force-free hardsphere model [29] to extract absolute values of water diffusivity.…”

Section: Introductionmentioning

confidence: 99%