@article {2020|2126, title = {Impact of A2T and D23N Mutations on Tetrameric Aβ42 Barrel within a Dipalmitoylphosphatidylcholine Lipid Bilayer Membrane by Replica Exchange Molecular Dynamics.}, journal = {J Phys Chem B}, volume = {124}, year = {2020}, month = {2020 Feb 20}, pages = {1175-1182}, abstract = {

In Alzheimer\&$\#$39;s disease (AD), many experimental and computational studies support the amyloid pore hypothesis of the Aβ42 peptide. We recently designed a β-barrel tetramer in a membrane-mimicking environment consistent with some low-resolution experimental data. In this earlier study, by using extensive replica exchange molecular dynamics simulations, we found that the wild-type (WT) Aβ42 peptides have a high propensity to form β-barrels, while the WT Aβ40 peptides do not. In this work, we have investigated the effect of mutations D23N and A2T on the Aβ42 barrel tetramer by using the same enhanced conformational sampling technique. It is known that the D23N mutation leads to early onset AD, while the A2T mutation protects from AD. This computational study in a dipalmitoylphosphatidylcholine (DPPC) lipid bilayer membrane shows that the WT sequence and its A2T variant have similar β-barrel populations and the three-dimensional model is slightly destabilized for D23N compared to its WT sequence. These extensive modeling calculations indicate that the lower and higher induced toxicity of these two mutations in AD cannot be correlated to their β-barrel tetramer stabilities in a DPPC lipid bilayer membrane.

}, issn = {1520-5207}, doi = {10.1021/acs.jpcb.9b11881}, author = {Ngo, Son Tung and Phuong Hoang Nguyen and Philippe Derreumaux} } @article {2020|2125, title = {Impact of the Astaxanthin, Betanin, and EGCG Compounds on Small Oligomers of Amyloid Aβ Peptide.}, journal = {J Chem Inf Model}, volume = {60}, year = {2020}, month = {2020 Mar 23}, pages = {1399-1408}, abstract = {

There is experimental evidence that the astaxanthin, betanin, and epigallocatechin-3-gallate (EGCG) compounds slow down the aggregation kinetics and the toxicity of the amyloid-β (Aβ) peptide. How these inhibitors affect the self-assembly at the atomic level remains elusive. To address this issue, we have performed for each ligand atomistic replica exchange molecular dynamic (REMD) simulations in an explicit solvent of the Aβ trimer from the U-shape conformation and MD simulations starting from Aβ dimer and tetramer structures characterized by different intra- and interpeptide conformations. We find that the three ligands have similar binding free energies on small Aβ oligomers but very distinct transient binding sites that will affect the aggregation of larger assemblies and fibril elongation of the Aβ peptide.

}, issn = {1549-960X}, doi = {10.1021/acs.jcim.9b01074}, author = {Minh Hung, Huynh and Nguyen, Minh Tho and Tran, Phuong-Thao and Truong, Vi Khanh and Chapman, James and Quynh Anh, Le Huu and Philippe Derreumaux and Vu, Van V and Ngo, Son Tung} } @article {2020|2116, title = {Stability of Aβ11-40 Trimers with Parallel and Antiparallel β-Sheet Organizations in a Membrane-Mimicking Environment by Replica Exchange Molecular Dynamics Simulation}, journal = {The Journal of Physical Chemistry B}, year = {2020}, author = {Ngo, Son Tung and Phuong Hoang Nguyen and Philippe Derreumaux} } @article {2019|2127, title = {C-Terminal Plays as the Possible Nucleation of the Self-Aggregation of the S-Shape Aβ Tetramer in Solution: Intensive MD Study.}, journal = {ACS Omega}, volume = {4}, year = {2019}, month = {2019 Jun 30}, pages = {11066-11073}, abstract = {

Amyloid beta (Aβ) peptides are characterized as the major factors associated with neuron death in Alzheimer\&$\#$39;s disease, which is listed as the most common form of neurodegeneration. Disordered Aβ peptides are released from proteolysis of the amyloid precursor protein. The Aβ self-assembly process roughly takes place via five steps: disordered forms \→ oligomers \→ photofibrils \→ mature fibrils \→ plaques. Although Aβ fibrils are often observed in patient brains, oligomers were recently indicated to be major neurotoxic elements. In this work, the neurotoxic compound S-shape Aβ tetramer (S4Aβ) was investigated over 10 μs of unbiased MD simulations. In particular, the S4Aβ oligomer adopted a high dynamics structure, resulting in unsuccessful determination of their structures in experiments. The C-terminal was suggested as the possible nucleation of the Aβ aggregation. The sequences 27-35 and 39-40 formed rich β-content, whereas other residues mostly adopted coil structures. The mean value of the β-content over the equilibrium interval is \∼42 \± 3\%. Furthermore, the dissociation free energy of the S4Aβ peptide was predicted using a biased sampling method. The obtained free energy is Δ = -58.44 kcal/mol which is roughly the same level as the corresponding value of the U-shape Aβ peptide. We anticipate that the obtained S4Aβ structures could be used as targets for AD inhibitor screening over the in silico study.

}, issn = {2470-1343}, doi = {10.1021/acsomega.9b00992}, author = {Tung, Nguyen Thanh and Philippe Derreumaux and Vu, Van V and Nam, Pham Cam and Ngo, Son Tung} } @article {2019|2128, title = {Probable Transmembrane Amyloid α-Helix Bundles Capable of Conducting Ca Ions.}, journal = {J Phys Chem B}, volume = {123}, year = {2019}, month = {2019 Mar 28}, pages = {2645-2653}, abstract = {

Amyloid β (Aβ) peptides are considered the major causative agents of Alzheimer\&$\#$39;s disease (AD). In a widely accepted mechanism for AD pathogenesis, Aβ peptides are proposed to play multiple roles in damaging brain cells and their synaptic communications. Due to the heterogeneous nature of Aβ oligomers, their in vivo structures have not been understood. Most experimental and computational studies favored β-rich structures of Aβ as observed in Aβ fibrils. In this in silico study, we investigated an alternative perspective on the structures and function of Aβ oligomers in the cell membrane. Transmembrane α-helix bundles of the Aβ tetramer and trimer were observed in extensive temperature replica exchange molecular dynamics (REMD) simulations. We observed three minima on the free-energy landscape of each oligomer, namely, A, B, and C for the tetramer and D, E, and F for the trimer. Except for F, the minima consist of 4 or 3 parallel helices spanning across the membrane model dipalmitoylphosphatidylcholine. Replica exchange molecular dynamics-umbrella sampling (REMD-US) simulation was applied to study the process of a Ca crossing the pore formed by the α-helix bundles in A-E in comparison to that in a calcium channel and a proton channel. REMD-US reveals that A, C, and D allow Ca to cross their pore with a free-energy barrier comparable to that found for the calcium channel. In contrast, the free-energy barrier of a Ca ion crossing B, E, and the proton channel is significantly higher. This result suggests that Aβ peptide oligomers could form transmembrane α-helix bundles that provide feasible pathways for Ca transport. This is an intriguing observation that will stimulate further studies.

}, issn = {1520-5207}, doi = {10.1021/acs.jpcb.8b10792}, author = {Ngo, Son Tung and Philippe Derreumaux and Vu, Van V} } @article {2019|2106, title = {Tetrameric Aβ40 and Aβ42 β-Barrel Structures by Extensive Atomistic Simulations. I. In a Bilayer Mimicking a Neuronal Membrane.}, journal = {J Phys Chem B}, volume = {123}, year = {2019}, month = {2019 May 02}, pages = {3643-3648}, abstract = {

The amyloid-β (Aβ) 42 oligomers are much more toxic than Aβ40 oligomers in Alzheimer\&$\#$39;s disease. Numerous experiments indicate that toxicity could involve the formation of pores in membranes, but experimental high-resolution structure determination of these pore-forming Aβ oligomers has been impeded by aggregate heterogeneity. Using extensive atomistic simulations, low-resolution data obtained in lipid bilayers, and other theoretical factors, we proposed atomic structures of Aβ40 and Aβ42 β-barrels in a bilayer mimicking a neuronal membrane. The 3D model, which consists of tetramer subunits, two distinct β-hairpin motifs and an asymmetric arrangement of eight antiparallel β-strands, is drastically destabilized for Aβ40 compared to its Aβ42 counterpart. Our computational modeling has several implications in Alzheimer\&$\#$39;s disease, sheds light on the amyloid pore hypothesis, and explains the higher deleterious property of Aβ42.

}, issn = {1520-5207}, doi = {10.1021/acs.jpcb.9b01206}, author = {Phuong Hoang Nguyen and Campanera, Josep M and Ngo, Son Tung and Loquet, Antoine and Philippe Derreumaux} } @article {2019|2105, title = {Tetrameric Aβ40 and Aβ42 β-Barrel Structures by Extensive Atomistic Simulations. II. In Aqueous Solution.}, journal = {J Phys Chem B}, volume = {123}, year = {2019}, month = {2019 Aug 08}, pages = {6750-6756}, abstract = {

Alzheimer\&$\#$39;s disease (AD) is characterized by the accumulation of extracellular Aβ42 and Aβ40 oligomers and plaques. In a recent computational study, we found that the presence of the residues I41 and A42 increases significantly the propensity of Aβ to form a tetrameric β-barrel structure in a bilayer mimicking a neuronal membrane. In this work, we have determined the propensity of the two Aβ proteins to form tetrameric β-barrel structures in aqueous solution using four atomistic protein fields, that is, Amber99SB-ILDN/TIP3P, OPLS/TIP3P, CHARMM36m/TIP3P-modified, and Amber99SB/DISP. Extensive replica exchange molecular dynamics simulations make it clear that a β-barrel, made of two distinct β-hairpin motifs and an asymmetric arrangement of eight antiparallel β-strands with an inner pore diameter of 0.7 nm, exists transiently for Aβ42 peptide, but this is less the case for Aβ40 peptide, due to the change of the CHC-CHC and the Cter-Cter interfaces. This study has several implications in AD.

}, issn = {1520-5207}, doi = {10.1021/acs.jpcb.9b05288}, author = {Phuong Hoang Nguyen and Campanera, Josep M and Ngo, Son Tung and Loquet, Antoine and Philippe Derreumaux} }