Amyloid aggregation
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One of the grand challenges of biophysical chemistry is to understand the principles that govern protein misfolding and aggregation, which is a highly complex process that is sensitive to initial conditions, operates on a huge range of length- and timescales, and has products that range from protein dimers to macroscopic amyloid fibrils. Aberrant aggregation is associated with more than 25 diseases, which include Alzheimer's, Parkinson's, Huntington's, and type II diabetes. Amyloid aggregation has been extensively studied in the test tube, therefore under conditions that are far from physiological relevance. Hence, there is dire need to extend these investigations to in vivo conditions where amyloid formation is affected by a myriad of biochemical interactions. As a hallmark of neurodegenerative diseases, these interactions need to be understood in detail to develop novel therapeutic interventions, as millions of people globally suffer from neurodegenerative disorders and type II diabetes. The aim of this review is to document the progress in the research on amyloid formation from a physicochemical perspective with a special focus on the physiological factors influencing the aggregation of the amyloid-β peptide, the islet amyloid polypeptide, α-synuclein, and the hungingtin protein.
In this perspective we summarize current knowledge of the effect of monosialoganglioside GM1 on the membrane-mediated aggregation of the β-amyloid (Aβ) peptide. GM1 has been suggested to be actively involved in the development of Alzheimer's disease due to its ability to seed the aggregation of Aβ. However, GM1 is known to be neuroprotective against Aβ-induced toxicity. Here we suggest that the two scenarios are not mutually exclusive but rather complementary, and might depend on the organization of GM1 in membranes. Improving our understanding of the molecular details behind the role of gangliosides in neurodegenerative amyloidoses might help in developing disease-modifying treatments.
- MeSH
- amyloidní beta-protein chemie metabolismus MeSH
- G(M1) gangliosid chemie metabolismus MeSH
- lidé MeSH
- mozek metabolismus MeSH
- patologická konformace proteinů metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
- Názvy látek
- amyloidní beta-protein MeSH
- G(M1) gangliosid MeSH
BACKGROUND: Aggregation of the neuronal protein α-synuclein into amyloid fibrils is a hallmark of Parkinson's disease. The propensity of α-synuclein to aggregate increases with the protein concentration. For the development of efficient inhibitors of α-synuclein aggregation, it is important to know the critical concentration of aggregation (the concentration of monomeric protein, below which the protein does not aggregate). METHODS: We performed in vitro aggregation studies of α-synuclein at low concentrations (0.11-20 μM). Aggregation kinetics was measured by ThT fluorescence. Obtained aggregates were characterized using CD-spectroscopy, fluorescent spectroscopy, dynamic light scattering and AFM imaging. RESULTS: Monomeric α-synuclein at concentrations 0.45 μM and above was able to bind to fibril ends resulting in fibril growth. At the protein concentrations below 0.4 μM, monomers did not fibrillize, and fibrils disaggregated. In the absence of seeds, fibrils were formed only at monomer concentrations higher than 10 μM. At low micromolar concentrations, we observed formation of prefibrillar amyloid aggregates, which are able to induce fibril formation in α-synuclein solutions of high concentrations. CONCLUSIONS: The critical concentration of α-synuclein fibril growth is ~0.4 μM. Prefibrillar amyloid aggregates appear at concentrations between 0.45 and 3 μM and are an intermediate state between monomers and fibrils. Although morphologically different from fibrils, prefibrillar aggregates have similar properties to those of fibrils. GENERAL SIGNIFICANCE: We determined the critical concentration of α-synuclein fibril growth. We showed that fibrils can grow at much lower monomer concentrations than that required for de novo fibril formation. We characterized a prefibrillar intermediate species formed upon aggregation of α-synuclein at low micromolar concentration.
- Klíčová slova
- Amyloid fibrils, Critical concentration, Fibril disaggregation, Intermediates, Kd, Kinetics,
- MeSH
- alfa-synuklein chemie metabolismus MeSH
- amyloid chemie metabolismus MeSH
- cirkulární dichroismus MeSH
- fluorescenční spektrometrie MeSH
- lidé MeSH
- proteinové agregáty * MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- alfa-synuklein MeSH
- amyloid MeSH
- proteinové agregáty * MeSH
- SNCA protein, human MeSH Prohlížeč
Coumarins are well-known for their unique chemical structure and a wide range of biological effects. Various substituted coumarin-based compounds have emerged as promising candidates for the development of novel therapeutic agents against numerous diseases. This study was focused on the synthesis of new 4,7-disubstituted coumarin derivatives and investigation of their ability to inhibit the aggregation of Aβ40 peptide, their cytotoxic effect on SH-SY5Y cells, their antioxidant properties, and their ability to penetrate the blood-brain barrier (BBB). The results revealed that the trihydroxy derivatives 5a-c had been the most effective inhibitors of Aβ aggregation, promoting the formation of non-toxic, amorphous aggregates instead. Importantly, no significant decrease in the viability of SH-SY5Y neuroblastoma cells was observed after treatment with the studied coumarins. Among them, coumarin 5a demonstrated the strongest antioxidant activity, while compound 5b also exhibited good antioxidant properties, along with the best inhibition of Aβ aggregation (IC50 = 13.5 μM), and adequate permeability across the blood-brain barrier. These findings suggest that compound 5b is a promising candidate for further investigation in Alzheimer's disease pharmacotherapy.
- Klíčová slova
- Alzheimer's disease, Amyloid aggregation, Antioxidant activity, Aβ peptide, Cell viability assay, Coumarin derivatives,
- MeSH
- amyloidní beta-protein * antagonisté a inhibitory metabolismus MeSH
- antioxidancia * farmakologie chemie chemická syntéza MeSH
- hematoencefalická bariéra metabolismus MeSH
- kumariny * farmakologie chemie chemická syntéza MeSH
- lidé MeSH
- molekulární struktura MeSH
- nádorové buněčné linie MeSH
- peptidové fragmenty * metabolismus antagonisté a inhibitory MeSH
- proteinové agregáty účinky léků MeSH
- viabilita buněk účinky léků MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- vztahy mezi strukturou a aktivitou MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- amyloidní beta-protein * MeSH
- antioxidancia * MeSH
- coumarin MeSH Prohlížeč
- kumariny * MeSH
- peptidové fragmenty * MeSH
- proteinové agregáty MeSH
Amyloid aggregates are associated with a range of human neurodegenerative disorders, and it has been shown that neurotoxicity is dependent on aggregate size. Combining molecular simulation with analytical theory, a predictive model is proposed for the adsorption of amyloid aggregates onto oppositely charged surfaces, where the interaction is governed by an interplay between electrostatic attraction and entropic repulsion. Predictions are experimentally validated against quartz crystal microbalance-dissipation experiments of amyloid beta peptides and fragmented fibrils in the presence of a supported lipid bilayer. Assuming amyloids as rigid, elongated particles, we observe nonmonotonic trends for the extent of adsorption with respect to aggregate size and preferential adsorption of smaller aggregates over larger ones. Our findings describe a general phenomenon with implications for stiff polyions and rodlike particles that are electrostatically attracted to a surface.
The complexity of Alzheimer's disease (AD) calls for search of multifunctional compounds as potential candidates for effective therapy. A series of phthalimide and saccharin derivatives linked by different alicyclic fragments (piperazine, hexahydropyrimidine, 3-aminopyrrolidine or 3-aminopiperidine) with phenylalkyl moieties attached have been designed, synthesized, and evaluated as multifunctional anti-AD agents with cholinesterase, β-secretase and β-amyloid inhibitory activities. In vitro studies showed that the majority of saccharin derivatives with piperazine moiety and one phthalimide derivative with 3-aminopiperidine fragment exhibited inhibitory potency toward acetylcholinesterase (AChE) with EeAChE IC50 values ranging from 0.83 μM to 19.18 μM. The target compounds displayed inhibition of human β-secretase-1 (hBACE1) ranging from 26.71% to 61.42% at 50 μM concentration. Among these compounds, two multifunctional agents (26, [2-(2-(4-benzylpiperazin-1-yl)ethyl)benzo[d]isothiazol-3(2H)-one 1,1-dioxide] and 52, 2-(2-(3-(3,5-difluorobenzylamino)piperidin-1-yl)ethyl)isoindoline-1,3-dione) have been identified. Compound 26 exhibited the highest inhibitory potency against EeAChE (IC50 = 0.83 μM) and inhibitory activity against hBACE1 (33.61% at 50 μM). Compound 52 is a selective AChE inhibitor (IC50 AChE = 6.47 μM) with BACE1 inhibitory activity (26.3% at 50 μM) and it displays the most significant Aβ anti-aggregating properties among all the obtained compounds (39% at 10 μM). Kinetic and molecular modeling studies indicate that 26 may act as non-competitive AChE inhibitor able to interact with both catalytic and peripheral active site of the enzyme.
- Klíčová slova
- Acetylcholinesterase inhibitors, Alzheimer's disease, Aβ aggregation, BACE1 inhibitors, Molecular docking, Multifunctional agents,
- MeSH
- aminy chemie farmakologie MeSH
- amyloidní beta-protein metabolismus MeSH
- cholinesterasy metabolismus MeSH
- ftalimidy chemická syntéza chemie farmakologie MeSH
- hematoencefalická bariéra účinky léků MeSH
- inhibiční koncentrace 50 MeSH
- inhibitory enzymů chemická syntéza chemie farmakologie MeSH
- lékové transportní systémy MeSH
- lidé MeSH
- molekulární struktura MeSH
- patologická konformace proteinů MeSH
- peptidové fragmenty metabolismus MeSH
- racionální návrh léčiv MeSH
- sacharin chemická syntéza chemie farmakologie MeSH
- sekretasy metabolismus MeSH
- vazba proteinů účinky léků MeSH
- vazebná místa MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- aminy MeSH
- amyloid beta-protein (1-34) MeSH Prohlížeč
- amyloidní beta-protein MeSH
- cholinesterasy MeSH
- ftalimidy MeSH
- inhibitory enzymů MeSH
- peptidové fragmenty MeSH
- phthalimide MeSH Prohlížeč
- sacharin MeSH
- sekretasy MeSH
The formation and accumulation of amyloid aggregates are the phenomena that accompany amyloidoses, which are currently untreatable and include Alzheimer's and Parkinson's diseases, diabetes mellitus, non-neuropathic lysozyme systemic amyloidosis, and others. One of the very promising therapeutic approaches seems to be an inhibition of amyloid formation and/or clearance of amyloid aggregates. Small molecules have a great potential to interfere with amyloid fibrillation of peptides and polypeptides, which can be improved by connection of cyclic structures into single multicyclic molecules and their dimerization. In our study, we focused on heterodimers consisting of 7-methoxytacrine (7-MEOTA) and 2-aminobenzothiazole (BTZ) parent molecules connected by an aliphatic linker. Using in vitro and in silico methods, we investigated the ability of studied compounds to inhibit the amyloid aggregation of hen egg white lysozyme. Heterodimerization led to significant improvement of inhibitory activity compared to that of the parent molecules. The efficiency of the heterodimers varied; the most effective inhibitor contained the longest linker, eight carbons long. We suggest that binding of a heterodimer to a lysozyme blocks the interaction between the β-domain and C-helix region essential for the formation of amyloid cross-β structure. Elongation of the linker ultimately enhances the compound's ability to prevent this interaction by allowing the BTZ part of the heterodimer to bind more effectively, increasing the compound's binding affinity, and also by greater steric obstruction. This study represents an important contribution to the recent rational design of potential lead small molecules with anti-amyloid properties, and the heterodimers studied are prospective candidates for the treatment of systemic lysozyme amyloidosis and other amyloid-related diseases.
- Klíčová slova
- Protein aggregation, amyloid, heterodimerization, inhibition, lysozyme, small molecules,
- MeSH
- amyloid * MeSH
- amyloidogenní proteiny MeSH
- amyloidóza * MeSH
- lidé MeSH
- prospektivní studie MeSH
- takrin analogy a deriváty MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- 7-methoxytacrine MeSH Prohlížeč
- amyloid * MeSH
- amyloidogenní proteiny MeSH
- takrin MeSH
α-Synuclein is a neuronal protein involved in synaptic vesicle trafficking. During the course of Parkinson's disease, it aggregates, forming amyloid fibrils that accumulate in the midbrain. This pathological fibrillization process is strongly modulated by physiological interactions of α-synuclein with lipid membranes. However, the detailed mechanism of this effect remains unclear. In this work, we used environment-sensitive fluorescent dyes to study the influence of model lipid membranes on the kinetics of α-synuclein fibrillization. We observed that formation of the fibrils from α-synuclein monomers is strongly delayed even by small amounts of lipids. Furthermore, we found that membrane-bound α-synuclein monomers are not involved in fibril elongation. Hence, presence of lipids slows down fibril growth proportionally to the fraction of membrane-bound protein.
- Klíčová slova
- amyloid, fibril, fibrillization, kinetics, lag time, liposomes,
- MeSH
- alfa-synuklein * MeSH
- amyloid MeSH
- kinetika MeSH
- lidé MeSH
- lipidy MeSH
- Parkinsonova nemoc * MeSH
- patologická konformace proteinů MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- alfa-synuklein * MeSH
- amyloid MeSH
- lipidy MeSH
Over the past thirty years, researchers have highlighted the role played by a class of proteins or polypeptides that forms pathogenic amyloid aggregates in vivo, including i) the amyloid Aβ peptide, which is known to form senile plaques in Alzheimer's disease; ii) α-synuclein, responsible for Lewy body formation in Parkinson's disease and iii) IAPP, which is the protein component of type 2 diabetes-associated islet amyloids. These proteins, known as intrinsically disordered proteins (IDPs), are present as highly dynamic conformational ensembles. IDPs can partially (mis) fold into (dys) functional conformations and accumulate as amyloid aggregates upon interaction with other cytosolic partners such as proteins or lipid membranes. In addition, an increasing number of reports link the toxicity of amyloid proteins to their harmful effects on membrane integrity. Still, the molecular mechanism underlying the amyloidogenic proteins transfer from the aqueous environment to the hydrocarbon core of the membrane is poorly understood. This review starts with a historical overview of the toxicity models of amyloidogenic proteins to contextualize the more recent lipid-chaperone hypothesis. Then, we report the early molecular-level events in the aggregation and ion-channel pore formation of Aβ, IAPP, and α-synuclein interacting with model membranes, emphasizing the complexity of these processes due to their different spatial-temporal resolutions. Next, we underline the need for a combined experimental and computational approach, focusing on the strengths and weaknesses of the most commonly used techniques. Finally, the last two chapters highlight the crucial role of lipid-protein complexes as molecular switches among ion-channel-like formation, detergent-like, and fibril formation mechanisms and their implication in fighting amyloidogenic diseases.
- Klíčová slova
- Aggregation, Amyloid, Ion channel-like, Lipid-chaperone, Model membrane, Toxic oligomer,
- MeSH
- alfa-synuklein chemie MeSH
- amyloid chemie MeSH
- amyloidogenní proteiny chemie MeSH
- amyloidóza * etiologie MeSH
- diabetes mellitus 2. typu * metabolismus MeSH
- lidé MeSH
- lipidy MeSH
- molekulární chaperony MeSH
- peptidy MeSH
- vnitřně neuspořádané proteiny * chemie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
- Názvy látek
- alfa-synuklein MeSH
- amyloid MeSH
- amyloidogenní proteiny MeSH
- lipidy MeSH
- molekulární chaperony MeSH
- peptidy MeSH
- vnitřně neuspořádané proteiny * MeSH
Alzheimer's Disease (AD) is a neurodegenerative disorder with an increasing impact on society. Because currently available therapy has only a short-term effect, a huge number of novel compounds are developed every year exploiting knowledge of the various aspects of AD pathophysiology. To better address the pathological complexity of AD, one of the most extensively pursued strategies by medicinal chemists is based on Multi-target-directed Ligands (MTDLs). Donepezil is one of the currently approved drugs for AD therapy acting as an acetylcholinesterase inhibitor. In this review, we have made an extensive literature survey focusing on donepezil-derived MTDL hybrids primarily targeting on different levels cholinesterases and amyloid beta (Aβ) peptide. The targeting includes direct interaction of the compounds with Aβ, AChE-induced Aβ aggregation, inhibition of BACE-1 enzyme, and modulation of biometal balance thus impeding Aβ assembly.
- Klíčová slova
- Acetylcholinesterase, Alzheimer`s disease, amyloid-β, beta-secretase 1, biometal, butyrylcholinesterase, multitarget directed ligands, neuroprotection.,
- MeSH
- acetylcholinesterasa metabolismus MeSH
- Alzheimerova nemoc farmakoterapie metabolismus MeSH
- amyloidní beta-protein metabolismus MeSH
- cholinesterasové inhibitory farmakologie terapeutické užití MeSH
- donepezil analogy a deriváty MeSH
- lidé MeSH
- patologická konformace proteinů farmakoterapie metabolismus MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
- Názvy látek
- acetylcholinesterasa MeSH
- amyloidní beta-protein MeSH
- cholinesterasové inhibitory MeSH
- donepezil MeSH