| 1. |
- Chemerovski-Glikman, Marina, et al.
(författare)
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Self-Assembled Cyclic D,L-alpha-Peptides as Generic Conformational Inhibitors of the alpha-Synuclein Aggregation and Toxicity : In Vitro and Mechanistic Studies
- 2016
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 22:40, s. 14236-14246
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Tidskriftsartikel (refereegranskat)abstract
- Many peptides and proteins with large sequences and structural differences self-assemble into disease-causing amyloids that share very similar biochemical and biophysical characteristics, which may contribute to their cross-interaction. Here, we demonstrate how the self-assembled, cyclic D,L-alpha-peptide CP-2, which has similar structural and functional properties to those of amyloids, acts as a generic inhibitor of the Parkinson's disease associated alpha-synuclein (alpha-syn) aggregation to toxic oligomers by an, off-pathway mechanism. We show that CP-2 interacts with the N-terminal and the non-amyloid-beta component region of alpha-syn, which are responsible for alpha-syn's membrane intercalation and self-assembly, thus changing the overall conformation of alpha-syn. CP-2 also remodels alpha-syn fibrils to nontoxic amorphous species and permeates cells through endosomes/lysosomes to reduce the accumulation and toxicity of intracellular alpha-syn in neuronal cells overexpressing alpha-syn. Our studies suggest that targeting the common structural conformation of amyloids may be a promising approach for developing new therapeutics for amyloidogenic diseases.
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| 2. |
- Leshem, Guy, et al.
(författare)
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Photoactive chlorin e6 is a multifunctional modulator of amyloid-β aggregation and toxicity via specific interactions with its histidine residues
- 2019
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Ingår i: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 10:1, s. 208-217
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Tidskriftsartikel (refereegranskat)abstract
- The self-assembly of A to -sheet-rich neurotoxic oligomers is a main pathological event leading to Alzheimer's disease (AD). Selective targeting of A oligomers without affecting other functional proteins is therefore an attractive approach to prevent the disease and its progression. In this study, we report that photodynamic treatment of A in the presence of catalytic amounts of chlorin e6 can selectively damage A and inhibit its aggregation and toxicity. Chlorin e6 also reversed the amyloid aggregation process in the dark by binding its soluble and low molecular weight oligomers, as shown by thioflavin T (ThT) fluorescence and photoinduced cross-linking of unmodified protein (PICUP) methods. Using HSQC NMR spectroscopy, ThT assays, amino acid analysis, SDS/PAGE, and EPR spectroscopy, we show that catalytic amounts of photoexcited chlorin e6 selectively damage the A histidine residues H6, H13, and H14, and induce A cross-linking by generating singlet oxygen. In contrast, photoexcited chlorin e6 was unable to cross-link ubiquitin and -synuclein, demonstrating its high selectivity for A. By binding to the A histidine residues, catalytic amounts of chlorin e6 can also inhibit the Cu2+-induced aggregation and toxicity in darkness, while at stoichiometric amounts it acts as a chelator to reduce the amount of free Cu2+. This study demonstrates the great potential of chlorin e6 as a multifunctional agent for treatment of AD, and shows that the three N-terminal A histidine residues are a suitable target for A-specific drugs.
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| 3. |
- Richman, Michal, et al.
(författare)
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In Vitro and Mechanistic Studies of an Antiamyloidogenic Self-Assembled Cyclic D,L-alpha-Peptide Architecture
- 2013
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 135:9, s. 3474-3484
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Tidskriftsartikel (refereegranskat)abstract
- Misfolding of the A beta protein and its subsequent aggregation into toxic oligomers are related to Alzheimer's disease. Although peptides of various sequences can self-assemble into amyloid structures, these structures share common three-dimensional features that may promote their cross-reaction. Given the significant similarities between amyloids and the architecture of self-assembled cyclic D,L-alpha-peptide, we hypothesized that the latter may bind and stabilize a nontoxic form of A beta thereby preventing its aggregation into toxic forms. By screening a focused library of six-residue cyclic D,L-alpha-peptides and optimizing the activity of a lead peptide, we found one cyclic D,L-alpha-peptide (CP-2) that interacts strongly with A beta and inhibits its aggregation. In transmission electron microscopy, optimized thioflavin T and cell survival assays, CP-2 inhibits the formation of A beta aggregates, entirely disassembles preformed aggregated and fibrillar A beta, and protects rat pheochromocytoma PC12 cells from A beta toxicity, without inducing any toxicity by itself. Using various immunoassays, circular dichroism spectroscopy, photoinduced cross-linking of unmodified proteins (PICUP) combined with SDS/PAGE, and NMR, we probed the mechanisms underlying CP-2's antiamyloidogenic activity. NMR spectroscopy indicates that CP-2 interacts with A beta through its self-assembled conformation and induces weak secondary structure in A beta. Upon coincubation, CP-2 changes the aggregation pathway of A beta and alters its oligomer distribution by stabilizing small oligomers (1-3 mers). Our results support studies suggesting that toxic early oligomeric states of A beta may be composed of antiparallel beta-peptide structures and that the interaction of A beta with CP-2 promotes formation of more benign parallel beta-structures. Further studies will show whether these kinds of abiotic cyclic D,L-alpha-peptides are also beneficial as an intervention in related in vivo models.
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| 4. |
- Tiiman, Ann, et al.
(författare)
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Specific Binding of Cu(II) Ions to Amyloid-Beta Peptides Bound to Aggregation-Inhibiting Molecules or SDS Micelles Creates Complexes that Generate Radical Oxygen Species
- 2016
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Ingår i: Journal of Alzheimer's Disease. - : IOS Press. - 1387-2877 .- 1875-8908. ; 54:3, s. 971-982
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Tidskriftsartikel (refereegranskat)abstract
- Aggregation of the amyloid-beta (A beta) peptide into insoluble plaques is a major factor in Alzheimer's disease (AD) pathology. Another major factor in AD is arguably metal ions, as metal dyshomeostasis is observed in AD patients, metal ions modulate A beta aggregation, and AD plaques contain numerous metals including redox-active Cu and Fe ions. In vivo, A beta is found in various cellular locations including membranes. So far, Cu(II)/A beta interactions and ROS generation have not been investigated in a membrane environment. Here, we study Cu(II) and Zn(II) interactions with A beta bound to SDS micelles or to engineered aggregation-inhibiting molecules (the cyclic peptide CP-2 and the Z(A beta 3)(12-58) Y18L Affibody molecule). In all studied systems the A beta N-terminal segment was found to be unbound, unstructured, and free to bind metal ions. In SDS micelles, A beta was found to bind Cu(II) and Zn(II) with the same ligands and the same K-D as in aqueous solution. ROS was generated in all Cu(II)/A beta complexes. These results indicate that binding of A beta to membranes, drugs, and other entities that do not interact with the A beta N-terminal part, appears not to compromise the N-terminal segment's ability to bind metal ions, nor impede the capacity of N-terminally bound Cu(II) to generate ROS.
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