Self-Assembly of β-Amyloid 42 Is Retarded by Small Molecular Ligands at the Stage of Structural Intermediates (original) (raw)
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Inhibitors of Amyloid Toxicity Based on β-sheet Packing of Aβ40 and Aβ42
Biochemistry, 2006
Amyloid fibrils associated with Alzheimer's disease and a wide range of other neurodegenerative diseases have a cross β-sheet structure where main chain hydrogen bonding occurs between β-strands in the direction of the fibril axis. The surface of the β-sheet has pronounced ridges and grooves when the individual β-strands have a parallel orientation and the amino acids are in-register with one another. Here we show that in Aβ amyloid fibrils, Met35 packs against Gly33 in the C-terminus of Aβ40 and against Gly37 in the C-terminus of Aβ42. These packing interactions suggest that the protofilament subunits are displaced relative to one another in the Aβ40 and Aβ42 fibril structures. We take advantage of this corrugated structure to design a new class of inhibitors that prevent fibril formation by placing alternating glycine and aromatic residues on one face of a β-strand. We show that peptide inhibitors based on a GxFxGxF framework disrupt sheet-to-sheet packing and inhibit the formation of mature Aβ fibrils as assayed by thioflavin T fluorescence, electron microscopy and solid-state NMR spectroscopy. The alternating large and small amino acids in the GxFxGxF sequence are complementary to the corresponding amino acids in the IxGxMxG motif found in the C-terminal sequence of Aβ40 and Aβ42. Importantly, the designed peptide inhibitors significantly reduce the toxicity induced by Aβ42 on cultured rat cortical neurons.
Inhibitors of Amyloid Toxicity Based on -sheet Packing of A 40 and A 42
Amyloid fibrils associated with Alzheimer's disease and a wide range of other neurodegenerative diseases have a cross-sheet structure, where main chain hydrogen bonding occurs between-strands in the direction of the fibril axis. The surface of the-sheet has pronounced ridges and grooves when the individual-strands have a parallel orientation and the amino acids are in-register with one another. Here we show that in A amyloid fibrils, Met35 packs against Gly33 in the C-terminus of A 40 and against Gly37 in the C-terminus of A 42. These packing interactions suggest that the protofilament subunits are displaced relative to one another in the A 40 and A 42 fibril structures. We take advantage of this corrugated structure to design a new class of inhibitors that prevent fibril formation by placing alternating glycine and aromatic residues on one face of a-strand. We show that peptide inhibitors based on a GxFxGxF framework disrupt sheet-to-sheet packing and inhibit the formation of mature A fibrils as assayed by thioflavin T fluorescence, electron microscopy, and solid-state NMR spectroscopy. The alternating large and small amino acids in the GxFxGxF sequence are complementary to the corresponding amino acids in the IxGxMxG motif found in the C-terminal sequence of A 40 and A 42. Importantly, the designed peptide inhibitors significantly reduce the toxicity induced by A 42 on cultured rat cortical neurons. Amyloid deposits associated with neurodegenerative diseases result from the folding of cellular proteins into non-native conformations. This alternative fold allows protein association and the formation of fibrils characterized by a cross-sheet structure (1). The challenge for developing specific inhibitors that block oligomer or fibril formation is that there are no high-resolution molecular structures that can guide the design. The design strategies developed to date have involved using short sequences related to the native sequence of the fibril forming protein (2, 3) or have taken advantage of the limited structural information available, that is, that these proteins polymerize through the association of-strands to form a cross-sheet structure. For instance, it has been possible to block hydrogen bonding within a-sheet by using peptides containing N-methyl amino acids or ester bonds in alternate positions along the peptide backbone (4-8), by inserting prolines within a-strand peptide as-breakers (9, 10), or a combination of these strategies (11, 12). We have recently noted that in fibrillogenic peptides derived from transmembrane helices, glycine often occurs in a GxxxG motif contained within a sequence of hydro-phobic amino acids (13). The GxxxG motif places two glycines on the same side of a transmembrane helix or on the same face of a-sheet. When the individual-strands within a-sheet have a parallel orientation and the amino acids are in-register with one another, glycines can form molecular notches or grooves in the surface of the-sheet that can run the length of the amyloid fibril. The association of-strands in a parallel and in-register orientation has been observed in several amyloid fibrils, such as those associated with Alzheimer's disease (14-16). In these fibrils, amino acids with large side chains form complementary molecular ridges that can pack into the glycine grooves and stabilize sheet-to-sheet packing (13). We show that this packing
Structural conversion of neurotoxic amyloid-β1–42 oligomers to fibrils
Nature Structural & Molecular Biology, 2010
The Aβ42 peptide rapidly aggregates to form oligomers, protofibils and fibrils en route to the deposition of amyloid plaques associated with Alzheimer's disease. We show that low temperature and low salt can stabilize disc-shaped oligomers (pentamers) that are significantly more toxic to murine cortical neurons than protofibrils and fibrils. We find that these neurotoxic oligomers do not have the β-sheet structure characteristic of fibrils. Rather, the oligomers are composed of loosely aggregated strands whose C-terminus is protected from solvent exchange and which have a turn conformation placing Phe19 in contact with Leu34. On the basis of NMR spectroscopy, we show that the structural conversion of Aβ42 oligomers to fibrils involves the association of these loosely aggregated strands into β-sheets whose individual β-strands polymerize in a parallel, inregister orientation and are staggered at an inter-monomer contact between Gln15 and Gly37. A major pathological hallmark of Alzheimer's disease (AD) is the formation of neuritic plaques within the gray matter of AD patients 1. These plaques are composed primarily of filamentous aggregates (fibrils) of the 39-42 amino acid long amyloid-β (Aβ) peptide formed from the proteolytic cleavage of the amyloid precursor protein by βand γ-secretases 2-5. The major species of Aβ production are the Aβ40 and Aβ42 peptides, with Aβ42 being predominant in neuritic plaques of AD patients and exhibiting a higher in vitro propensity to Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
Structural conversion of neurotoxic amyloid-[beta] 1-42 oligomers to fibrils
Nature structural & …, 2010
The amyloid-β 142 (Aβ42) peptide rapidly aggregates to form oligomers, protofibils and fibrils en route to the deposition of amyloid plaques associated with Alzheimer's disease. We show that low-temperature and low-salt conditions can stabilize disc-shaped oligomers ( ...
New class of inhibitors of amyloid-β fibril formation
2002
The amyloid hypothesis suggests that the process of amyloid- protein (A) fibrillogenesis is responsible for triggering a cascade of physiological events that contribute directly to the initiation and progression of Alzheimer's disease. Consequently, preventing this process might provide a viable therapeutic strategy for slowing and/or preventing the progression of this devastating disease. A promising strategy to achieve prevention of this disease is to discover compounds that inhibit A polymerization and deposition. Herein, we describe a new class of small molecules that inhibit A aggregation, which is based on the chemical structure of apomorphine. These molecules were found to interfere with A1-40 fibrillization as determined by transmission electron microscopy, Thioflavin T fluorescence and velocity sedimentation analytical ultracentrifugation studies. Using electron microscopy, time-dependent studies demonstrate that apomorphine and its derivatives promote the oligomerization of A but inhibit its fibrillization. Preliminary structural activity studies demonstrate that the 10,11-dihydroxy substitutions of the D-ring of apomorphine are required for the inhibitory effectiveness of these aporphines, and methylation of these hydroxyl groups reduces their inhibitory potency. The ability of these small molecules to inhibit A amyloid fibril formation appears to be linked to their tendency to undergo rapid autoxidation, suggesting that autoxidation product(s) acts directly or indirectly on A and inhibits its fibrillization. The inhibitory properties of the compounds presented suggest a new class of small molecules that could serve as a scaffold for the design of more efficient inhibitors of A amyloidogenesis in vivo.
Cellular and Molecular Life Sciences, 2011
Alzheimer's disease (AD) is a neurodegenerative disorder occurring in the elderly. It is widely accepted that the amyloid beta peptide (Ab) aggregation and especially the oligomeric states rather than fibrils are involved in AD onset. We used infrared spectroscopy to provide structural information on the entire aggregation pathway of Ab(1-40), starting from monomeric Ab to the end of the process, fibrils. Our structural study suggests that conversion of oligomers into fibrils results from a transition from antiparallel to parallel b-sheet. These structural changes are described in terms of H-bonding rupture/formation, b-strands reorientation and b-sheet elongation. As antiparallel b-sheet structure is also observed for other amyloidogenic proteins forming oligomers, reorganization of the b-sheet implicating a reorientation of b-strands could be a generic mechanism determining the kinetics of protein misfolding. Elucidation of the process driving aggregation, including structural transitions, could be essential in a search for therapies inhibiting aggregation or disrupting aggregates.
Biomacromolecules, 2014
The formation of extracellular neuritic plaques in the brain of individuals who suffered from Alzheimer's disease (AD) is a major pathological hallmark. These plaques consist of filamentous aggregates of the amyloid beta (1−42) (Aβ 42 ) proteins. Prevention or reduction of the formation of these fibrils is foreseen as a potential therapeutic approach. In this context, we investigated the interactions between the Aβ 42 protein and polyions, in particular short single stranded synthetic nucleotide sequences. The experimental outcomes reported herein provide evidence of the inhibition of amyloid fibril genesis as well as disassembly of existing fibers through electrostatic interaction between the Aβ 42 protein and the polyions. Since the polyions and the Aβ 42 protein are oppositely charged, the formation of (micellar) inter polyelectrolyte complexes (IPECs) is likely to occur. Since the abnormal deposition of amyloid fibers is an archetype of AD, the outcomes of these investigations, supported by atomic force microscopy imaging in the dry and liquid states, as well as circular dichroism and Fourier transform infrared spectroscopy, are of high interest for the development of future strategies to cure a disease that concerns an ever aging population.
The Properties of Amyloid-β Fibrils Are Determined by their Path of Formation
Journal of molecular biology, 2018
Fibril formation of the amyloid-β peptide (Aβ) follows a nucleation-dependent polymerization process and is associated with Alzheimer's disease. Several different lengths of Aβ are observed in vivo, but Aβ1-40 and Aβ1-42 are the dominant forms. The fibril architectures of Aβ1-40 and Aβ1-42 differ and Aβ1-42 assemblies are generally considered more pathogenic. We show here that monomeric Aβ1-42 can be cross-templated and incorporated into the ends of Aβ1-40 fibrils, while incorporation of Aβ1-40 monomers into Aβ1-42 fibrils is very poor. We also show that via cross-templating incorporated Aβ monomers acquire the properties of the parental fibrils. The suppressed ability of Aβ1-40 to incorporate into the ends of Aβ1-42 fibrils and the capacity of Aβ1-42 monomers to adopt the properties of Aβ1-40 fibrils may thus represent two mechanisms reducing the total load of fibrils having the intrinsic, and possibly pathogenic, features of Aβ1-42 fibrils in vivo. We also show that the transf...