Mass spectrometry and the amyloid problem—How far can we go in the gas phase?

Ashcroft, Alison E.

doi:10.1016/j.jasms.2010.02.026

Cited by 65 publications

(59 citation statements)

References 86 publications

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“…To gain more insight into soluble oligomeric species invisible to NMR, IM-MS experiments were performed on samples with varying molar ratios of EGCG under conditions designed to probe their solution stoichiometry and structure (35,36,39). In the absence of EGCG, Aβ (10 μM) existed primarily as a mixture of monomers and dimers (Fig.…”

Section: Egcg Directly Binds To Aβ Peptide and Causes Conformational mentioning

confidence: 99%

Insights into antiamyloidogenic properties of the green tea extract (−)-epigallocatechin-3-gallate toward metal-associated amyloid-β species

Hyung¹,

DeToma²,

Brender

et al. 2013

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

219

268

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Despite the significance of Alzheimer's disease, the link between metal-associated amyloid-β (metal-Aβ) and disease etiology remains unclear. To elucidate this relationship, chemical tools capable of specifically targeting and modulating metal-Aβ species are necessary, along with a fundamental understanding of their mechanism at the molecular level. Herein, we investigated and compared the interactions and reactivities of the green tea extract, (−)-epigallocatechin-3-gallate [(2R,3R)-5,7-dihydroxy-2-(3,4,5-trihydroxyphenyl)-3,4-dihydro-2H-1-benzopyran-3-yl 3,4,5-trihydroxybenzoate; EGCG], with metal [Cu(II) and Zn(II)]-Aβ and metal-free Aβ species. We found that EGCG interacted with metal-Aβ species and formed small, unstructured Aβ aggregates more noticeably than in metal-free conditions in vitro. In addition, upon incubation with EGCG, the toxicity presented by metalfree Aβ and metal-Aβ was mitigated in living cells. To understand this reactivity at the molecular level, structural insights were obtained by ion mobility-mass spectrometry (IM-MS), 2D NMR spectroscopy, and computational methods. These studies indicated that (i) EGCG was bound to Aβ monomers and dimers, generating more compact peptide conformations than those from EGCGuntreated Aβ species; and (ii) ternary EGCG-metal-Aβ complexes were produced. Thus, we demonstrate the distinct antiamyloidogenic reactivity of EGCG toward metal-Aβ species with a structurebased mechanism.amyloid-β peptide | metal ions | natural products | amyloidogenesis T he brain of individuals with Alzheimer's disease (AD) has protein aggregates composed of misfolded amyloid-β (Aβ) peptides (1-4). The Aβ peptides are produced endogenously through enzymatic cleavage of amyloid precursor protein. Aβ monomers can misfold and oligomerize into various intermediates before the formation and elongation of fibrils that exhibit a characteristic cross-β-sheet structure (1-4). The accumulation of aggregated Aβ species has been a key feature of the amyloid cascade hypothesis, which cites that these aggregates are possible causative agents in AD. In addition, transition metals, such as Cu and Zn, whose misregulation leads to aberrant neuronal function, have a suggested link to AD pathology (1,(3)(4)(5)(6)(7)(8). In vitro and in vivo studies have provided evidence for the direct interactions of metal ions with Aβ and their presence within Aβ plaques, indicating the formation of metal-associated Aβ (metal-Aβ) species. These metal-Aβ species have been implicated in processes that could lead to neurotoxicity (e.g., metal-induced Aβ aggregation and metal-Aβ-mediated reactive oxygen species generation) (1, 3-8). The involvement of metal-Aβ species in AD pathogenesis, however, has not been clearly elucidated. To advance our understanding of the potential neurotoxicity of metal-Aβ species, efforts to develop chemical tools capable of interacting directly with metal-Aβ species and modulating their reactivity in vitro and in biological systems are under way (1,(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)...

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Section: Egcg Directly Binds To Aβ Peptide and Causes Conformational mentioning

confidence: 99%

Insights into antiamyloidogenic properties of the green tea extract (−)-epigallocatechin-3-gallate toward metal-associated amyloid-β species

Hyung¹,

DeToma²,

Brender

et al. 2013

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

219

268

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“…Figure 1. CD spectra of di-ubiquitin conjugates with Lys63-and Lys48-specific linkages peptides and proteins [46][47][48][49]. Here, we focus on comparative studies of the Lys63-linked (Ub_1) and Lys48-linked (Ub_2) ubiquitin conjugates.…”

Section: Comparison Of Collision Cross-sections and Conformational Chmentioning

confidence: 99%

Differentiation of Compact and Extended Conformations of Di-Ubiquitin Conjugates with Lysine-Specific Isopeptide Linkages by Ion Mobility-Mass Spectrometry

Jung

Pierson

Marquardt

et al. 2011

J. Am. Soc. Mass Spectrom.

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Modification of ubiquitin, a key cellular regulatory polypeptide of 76 amino acids, to polyubiquitin conjugates by lysine-specific isopeptide linkage at one of its seven lysine residues has been recognized as a central pathway determining its biochemical properties and cellular functions. Structural details and differences of distinct lysine-isopeptidyl ubiquitin conjugates that reflect their different functions and reactivities, however, are only partially understood. Ion mobility spectrometry (IMS) combined with mass spectrometry (MS) has recently emerged as a powerful tool for probing conformations and topology involved in protein interactions by an electric fielddriven separation of polypeptide ions through a drift gas. Here we report the conformational characterization and differentiation of Lys63-and Lys48-linked ubiquitin conjugates by IMS-MS. Lys63-and Lys48-linked di-ubiquitin conjugates were prepared by recombinant bacterial expression and by chemical synthesis using a specific chemical ligation strategy, and characterized by high-resolution Fourier transform ion cyclotron resonance mass spectrometry, circular dichroism spectroscopy, and molecular modeling. IMS-MS was found to be an effective tool for the identification of structural differences of ubiquitin complexes in the gas phase. The comparison of collision cross-sections of Lys63-and Lys48-linked di-ubiquitin conjugates showed a more elongated conformation of Lys63-linked di-ubiquitin. In contrast, the Lys48-linked di-ubiquitin conjugate showed a more compact conformation. The IMS-MS results are consistent with published structural data and a comparative molecular modeling study of the Lys63-and Lys48-linked conjugates. The results presented here suggest IMS techniques can provide information that complements MS measurements in differentiating higher-order polyubiquitins and other isomeric protein linkages.

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“…This correlation greatly expands the scope of gas phase structural investigations such as ion mobility measurements [22][23][24], gas phase hydrogen exchange [25], and optical spectroscopy [26]. In addition, a host of ion activation methods are available for the dissociation of protein assemblies [27][28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 97%

An Electrostatic Charge Partitioning Model for the Dissociation of Protein Complexes in the Gas Phase

Sciuto

Liu

Konermann

2011

J. Am. Soc. Mass Spectrom.

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Electrosprayed multi-protein complexes can be dissociated by collisional activation in the gas phase. Typically, these processes follow a mechanism whereby a single subunit gets ejected with a disproportionately high amount of charge relative to its mass. This asymmetric behavior suggests that the departing subunit undergoes some degree of unfolding prior to being separated from the residual complex. These structural changes occur concomitantly with charge (proton) transfer towards the subunit that is being unraveled. Charge accumulation takes place up to the point where the subunit loses physical contact with the residual complex. This work develops a simple electrostatic model for studying the relationship between conformational changes and charge enrichment during collisional activation. Folded subunits are described as spheres that carry continuum surface charge. The unfolded chain is envisioned as random coil bead string. Simulations are guided by the principle that the system will adopt the charge configuration with the lowest potential energy for any backbone conformation. A finite-difference gradient algorithm is used to determine the charge on each subunit throughout the dissociation process. Both dimeric and tetrameric protein complexes are investigated. The model reproduces the occurrence of asymmetric charge partitioning for dissociation events that are preceded by subunit unfolding. Quantitative comparisons of experimental MS/MS data with model predictions yield estimates of the structural changes that occur during collisional activation. Our findings suggest that subunit separation can occur over a wide range of scission point structures that correspond to different degrees of unfolding.

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Mass spectrometry and the amyloid problem—How far can we go in the gas phase?

Cited by 65 publications

References 86 publications

Insights into antiamyloidogenic properties of the green tea extract (−)-epigallocatechin-3-gallate toward metal-associated amyloid-β species

Insights into antiamyloidogenic properties of the green tea extract (−)-epigallocatechin-3-gallate toward metal-associated amyloid-β species

Differentiation of Compact and Extended Conformations of Di-Ubiquitin Conjugates with Lysine-Specific Isopeptide Linkages by Ion Mobility-Mass Spectrometry

An Electrostatic Charge Partitioning Model for the Dissociation of Protein Complexes in the Gas Phase

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