Amyloid-beta peptide (25–35) triggers a reorganization of lipid membranes driven by temperature changes
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ABSTRACT:
SUBMITTER: Ivankov O
PROVIDER: S-EPMC8578324 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The formation of amyloid-? plaques is one of the hallmarks of Alzheimer's disease. The presence of an amphiphatic cell membrane can accelerate the formation of amyloid-? aggregates, making it a potential druggable target to delay the progression of Alzheimer's disease. We have prepared unsaturated anionic membranes made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1,2-dimyristoyl-sn-glycero-3-phospho-L-serine (DMPS) and added the trans-membrane segment A?25-35. Peptide plaques spontaneously form in these membranes at high peptide concentrations of 20?mol%, which show the characteristic cross-? motif (concentrations are relative to the number of membrane lipids and indicate the peptide-to-lipid ratio). We used atomic force microscopy, fluorescence microscopy, x-ray microscopy, x-ray diffraction, UV-vis spectroscopy and Molecular Dynamics (MD) simulations to study three membrane-active molecules which have been speculated to have an effect in Alzheimer's disease: melatonin, acetylsalicyclic acid (ASA) and curcumin at concentrations of 5?mol% (drug-to-peptide ratio). Melatonin did not change the structural parameters of the membranes and did not impact the size or extent of peptide clusters. While ASA led to a membrane thickening and stiffening, curcumin made membranes softer and thinner. As a result, ASA was found to lead to the formation of larger peptide aggregates, whereas curcumin reduced the volume fraction of cross-? sheets by ~70%. We speculate that the interface between membrane and peptide cluster becomes less favorable in thick and stiff membranes, which favors the formation of larger aggregates, while the corresponding energy mismatch is reduced in soft and thin membranes. Our results present evidence that cross-? sheets of A?25-35 in anionic unsaturated lipid membranes can be re-dissolved by changing membrane properties to reduce domain mismatch.
| S-EPMC6098001 | biostudies-literature
Project description:Background and purposeCilostazol may be effective in dementia associated with a cerebral ischaemia. In this study, we examined whether it exerts beneficial effects on learning and/or memory impairment induced by A?(25-35) in mice, and compared its effects with those of aspirin.Experimental approachA?(25-35) (9?nmol) was administered to mice i.c.v. Learning and memory behaviour were evaluated by measuring spontaneous alternation in a Y-maze and a step-down type passive avoidance test, on the 5th and 8th days after injection respectively. Levels of lipid peroxidation (malondialdehyde) and cytokines in the frontal cortex and hippocampus were measured 2, 3, 5 and 7 days after the A?(25-35) injection. The effects of repeated administration of cilostazol and aspirin (both at 30 and 100?mg·kg(-1), p.o.) on any changes induced by A?(25-35) were evaluated.Key resultsRepeated administration of cilostazol significantly attenuated the impairment of spontaneous alternation and the shortened step-down latency induced by A?(25-35) . Aspirin did not show any beneficial effect. A significant increase in the levels of malondialdehyde (MDA) and IL-1? (only measured in hippocampus) was observed 2, 3 and 5 days after the A?(25-35) injection in the frontal cortex and hippocampus. Repeated administration of cilostazol (100?mg·kg(-1)) completely prevented the increase in MDA levels but failed to antagonize the increase in the expression of IL-1? induced by A?(25-35).Conclusions and implicationsThese results suggest that the protective effect of cilostazol on A?(25-35)-induced memory impairment may be related to oxidative stress in the frontal cortex and the hippocampus.
| S-EPMC3010591 | biostudies-literature
Project description:The free energy landscape for folding of the Alzheimer's amyloid-beta(25-35) peptide is explored using replica exchange molecular dynamics in both pure water and in HFIP/water cosolvent. This amphiphilic peptide is a natural by-product of the Alzheimer's amyloid-beta(1-40) peptide and retains the toxicity of its full-length counterpart as well as the ability to aggregate into beta-sheet-rich fibrils. Our simulations reveal that the peptide preferentially populates a helical structure in apolar organic solvent, while in pure water, the peptide adopts collapsed coil conformations and to a lesser extent beta-hairpin conformations. The beta-hairpin is characterized by a type II' beta-turn involving residues G29 and A30 and two short beta-strands involving residues N27, K28, I31, and I32. The hairpin is stabilized by backbone hydrogen-bonding interactions between residues K28 and I31; S26 and G33; and by side-chain-to-side-chain interactions between N27 and I32. Implications regarding the mechanism of aggregation of this peptide into fibrils and the role of the environment in modulating secondary structure are discussed.
| S-EPMC1544315 | biostudies-literature
Project description:The amyloid β (Aβ) peptide and its shorter variants, including a highly cytotoxic Aβ25-35 peptide, exert their neurotoxic effect during Alzheimer's disease by various mechanisms, including cellular membrane permeabilization. The intrinsic polymorphism of Aβ has prevented the identification of the molecular basis of Aβ pore formation by direct structural methods, and computational studies have led to highly divergent pore models. Here, we have employed a set of biophysical techniques to directly monitor Ca2+-transporting Aβ25-35 pores in lipid membranes, to quantitatively characterize pore formation, and to identify the key structural features of the pore. Moreover, the effect of membrane cholesterol on pore formation and the structure of Aβ25-35 has been elucidated. The data suggest that the membrane-embedded peptide forms 6- or 8-stranded β-barrel like structures. The 8-stranded barrels may conduct Ca2+ ions through an inner cavity, whereas the tightly packed 6-stranded barrels need to assemble into supramolecular structures to form a central pore. Cholesterol affects Aβ25-35 pore formation by a dual mechanism, i.e., by direct interaction with the peptide and by affecting membrane structure. Collectively, our data illuminate the molecular basis of Aβ membrane pore formation, which should advance both basic and clinical research on Alzheimer's disease and membrane-associated pathologies in general.
| S-EPMC6389947 | biostudies-literature
Project description:The behavior of the amyloid β-peptide (Aβ) within a membrane environment is integral to its toxicity and the progression of Alzheimer's disease. Ganglioside GM1 has been shown to enhance the aggregation of Aβ, but the underlying mechanism is unknown. Using atomistic molecular dynamics simulations, we explored the interactions between the 40-residue alloform of Aβ (Aβ(40) ) and several model membranes, including pure palmitoyloleoylphosphatidylcholine (POPC) and palmitoyloleoylphosphatidylserine (POPS), an equimolar mixture of POPC and palmitoyloleoylphosphatidylethanolamine (POPE), and lipid rafts, both with and without GM1, to understand the behavior of Aβ(40) in various membrane microenvironments. Aβ(40) remained inserted in POPC, POPS, POPC/POPE, and raft membranes, but in several instances exited the raft containing GM1. Aβ(40) interacted with GM1 largely through hydrogen bonding, producing configurations containing β-strands with C-termini that, in some cases, exited the membrane and became exposed to solvent. These observations provide insight into the release of Aβ from the membrane, a previously uncharacterized process of the Aβ aggregation pathway.
| S-EPMC3190148 | biostudies-literature
Project description:Fibrillar aggregates of misfolded amyloid proteins are involved in a variety of diseases such as Alzheimer disease (AD), type 2 diabetes, Parkinson, Huntington and prion-related diseases. In the case of AD amyloid ? (A?) peptides, the toxicity of amyloid oligomers and larger fibrillar aggregates is related to perturbing the biological function of the adjacent cellular membrane. We used atomistic molecular dynamics (MD) simulations of A? 9-40 fibrillar oligomers modeled as protofilament segments, including lipid bilayers and explicit water molecules, to probe the first steps in the mechanism of A?-membrane interactions. Our study identified the electrostatic interaction between charged peptide residues and the lipid headgroups as the principal driving force that can modulate the further penetration of the C-termini of amyloid fibrils or fibrillar oligomers into the hydrophobic region of lipid membranes. These findings advance our understanding of the detailed molecular mechanisms and the effects related to A?-membrane interactions, and suggest a polymorphic structural character of amyloid ion channels embedded in lipid bilayers. While inter-peptide hydrogen bonds leading to the formation of ?-strands may still play a stabilizing role in amyloid channel structures, these may also present a significant helical content in peptide regions (e.g., termini) that are subject to direct interactions with lipids rather than with neighboring A? peptides.
| S-EPMC3609060 | biostudies-literature
Project description:The amyloid-?(25-35) peptide plays a key role in the etiology of Alzheimer's disease due to its extreme toxicity even in the absence of aging. Because of its high tendency to aggregate and its low solubility in water, the structure of this peptide is still unknown. In this work, we sought to understand the early stages of aggregation of the amyloid-?(25-35) peptide by conducting simulations of oligomers ranging from monomers to tetramers. Our simulations show that although the monomer preferentially adopts a ?-hairpin conformation, larger aggregates have extended structures, and a clear transition from compact ?-hairpin conformations to extended ?-strand structures occurs between dimers and trimers. Even though ?-hairpins are not present in the final architecture of the fibril, our simulations indicate that they play a critical role in fibril growth. Our simulations also show that ?-sheet structures are stabilized when a ?-hairpin is present at the edge of the sheet. The binding of the hairpin to the sheet leads to a subsequent destabilization of the hairpin, with part of the hairpin backbone dangling in solution. This free section of the peptide can then recruit an extra monomer from solution, leading to further sheet extension. Our simulations indicate that the peptide must possess sufficient conformational flexibility to switch between a hairpin and an extended conformation in order for ?-sheet extension to occur, and offer a rationalization for the experimental observation that overstabilizing a hairpin conformation in the monomeric state (for example, through chemical cross-linking) significantly hampers the fibrillization process.
| S-EPMC3414875 | biostudies-other
Project description:The interactions of the Alzheimer's β-amyloid peptide, Aβ(25-35), with 18:1 (Δ9-Cis) PC 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), L-α-phosphatidylcholine (EPC), 1,2-dioleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt) (DOPG), and L-α-phosphatidylglycerol (EPG) phospholipid vesicles with and without cholesterol (Ch) are studied by the nitroxide spin probe electron paramagnetic resonance (EPR) method. Two nitroxide spin probes, 2,2,6,6-tetramethyl-piperidin-1-oxyl-4-yl hexadecanoate (TP, TEMPO-Palmitate) and 2-Ethyl-2-(15-methoxy-15-oxopentadecyl)-4,4-dimethyl-3-oxazolidinyloxy (16-DSE), are utilized in the study. TEMPO-Palmitate has the reporting EPR moiety located at the top of this spin probe, while 16-DSE has the reporting EPR moiety located at the tail of the spin probe. These two probes enable us to sample the surface and the middle of the phospholipid bilayer, respectively. All EPR measurements are done above the melting points of all four phospholipids when the bilayer is in the liquid crystal phase, the physiologically relevant phase. Due to non-linear spectral line fitting, the EPR spectral parameters are extracted with high precision. The results show that there are two populations of Aβ(25-35) and that one of them is located in the hydrophobic phospholipid layer below the hydrophilic headgroup region. The second population appears to be weakly coupled to the surface of the bilayer. Both hydrophobic and electrostatic interactions affect the insertion of Aβ(25-35) in the bilayer. Also, there is strong evidence for an interaction between cholesterol and Aβ(25-35), which affects the dielectric and dynamic properties of the bilayer.
| S-EPMC6342288 | biostudies-literature
Project description:Beta-amyloid (Abeta) peptides may cause malfunction and death of neurons in Alzheimer's disease. We investigated the effect of Abeta on key transporters of amino acid neurotransmission in cells cultured from rat cerebral cortex. The cultures were treated with Abeta(25-35) at 3 and 10 microM for 12 and 24 h followed by quantitative analysis of immunofluorescence intensity. In mixed neuronal-glial cell cultures (from P1 rats), Abeta reduced the concentration of system A glutamine transporter 1 (SAT1), by up to 50% expressed relative to the neuronal marker microtubule-associated protein 2 (MAP2) in the same cell. No significant effects were detected on vesicular glutamate transporters VGLUT1 or VGLUT2 in neurons, or on glial system N glutamine transporter 1 (SN1). In neuronal cell cultures (from E18 rats), Abeta(25-35) did not reduce SAT1 immunoreactivity, suggesting that the observed effect depends on the presence of astroglia. The results indicate that Abeta may impair neuronal function and transmitter synthesis, and perhaps reduce excitotoxicity, through a reduction in neuronal glutamine uptake.
| S-EPMC2226019 | biostudies-other
Project description:The homopentameric B-subunit of bacterial protein Shiga toxin (STxB) binds to the glycolipid Gb(3) in plasma membranes, which is the initial step for entering cells by a clathrin-independent mechanism. It has been suggested that protein clustering and lipid reorganization determine toxin uptake into cells. Here, we elucidated the molecular requirements for STxB induced Gb(3) clustering and for the proposed lipid reorganization in planar membranes. The influence of binding site III of the B-subunit as well as the Gb(3) lipid structure was investigated by means of high resolution methods such as fluorescence and scanning force microscopy. STxB was found to form protein clusters on homogenous 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/cholesterol/Gb(3) (65:30:5) bilayers. In contrast, membranes composed of DOPC/cholesterol/sphingomyelin/Gb(3) (40:35:20:5) phase separate into a liquid ordered and liquid disordered phase. Dependent on the fatty acid composition of Gb(3), STxB-Gb(3) complexes organize within the liquid ordered phase upon protein binding. Our findings suggest that STxB is capable of forming a new membrane phase that is characterized by lipid compaction. The significance of this finding is discussed in the context of Shiga toxin-induced formation of endocytic membrane invaginations.
| S-EPMC2705791 | biostudies-literature