| 1. |
- Wu, Biying, et al.
(author)
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Megakaryocytes Mediate Hyperglycemia-Induced Tumor Metastasis
- 2021
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In: Cancer Research. - : AMER ASSOC CANCER RESEARCH. - 0008-5472 .- 1538-7445. ; 81:21, s. 5506-5522
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Journal article (peer-reviewed)abstract
- High blood glucose has long been established as a risk factor for tumor metastasis, yet the molecular mechanisms underlying this association have not been elucidated. Here we describe that hyperglycemia promotes tumor metastasis via increased platelet activity. Administration of glucose, but not fructose, reprogrammed the metabolism of megakaryocytes to indirectly prime platelets into a prometastatic phenotype with increased adherence to tumor cells. In megakaryocytes, a glucose metabolism-related gene array identified the mitochondrial molecular chaperone glucose-regulated protein 75 (GRP75) as a trigger for platelet activation and aggregation by stimulating the Ca2+-PKC alpha pathway. Genetic depletion of Glut1 in megakaryocytes blocked MYC-induced GRP75 expression. Pharmacologic blockade of platelet GRP75 compromised tumor-induced platelet activation and reduced metastasis. Moreover, in a pilot clinical study, drinking a 5% glucose solution elevated platelet GRP75 expression and activated platelets in healthy volunteers. Platelets from these volunteers promoted tumor metastasis in a plateletadoptive transfer mouse model. Together, under hyperglycemic conditions, MYC-induced upregulation of GRP75 in megakaryocytes increases platelet activation via the Ca2+-PKC alpha pathway to promote cancer metastasis, providing a potential new therapeutic target for preventing metastasis. Significance: This study provides mechanistic insights into a glucose-megakaryocyte-platelet axis that promotes metastasis and proposes an antimetastatic therapeutic approach by targeting the mitochondrial protein GRP75.
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| 2. |
- Xie, Sisi, et al.
(author)
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Dietary ketone body-escalated histone acetylation in megakaryocytes alleviates chemotherapy-induced thrombocytopenia
- 2022
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In: Science Translational Medicine. - : AMER ASSOC ADVANCEMENT SCIENCE. - 1946-6234 .- 1946-6242. ; 14:673
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Journal article (peer-reviewed)abstract
- Chemotherapy-induced thrombocytopenia (CIT) is a severe complication in patients with cancer that can lead to impaired therapeutic outcome and survival. Clinically, therapeutic options for CIT are limited by severe adverse effects and high economic burdens. Here, we demonstrate that ketogenic diets alleviate CIT in both animals and humans without causing thrombocytosis. Mechanistically, ketogenic diet-induced circulating beta-hydroxybutyrate (beta-OHB) increased histone H3 acetylation in bone marrow megakaryocytes. Gain- and loss-of-function experiments revealed a distinct role of 3-beta-hydroxybutyrate dehydrogenase (BDH)-mediated ketone body metabolism in promoting histone acetylation, which promoted the transcription of platelet biogenesis genes and induced thrombocytopoiesis. Genetic depletion of the megakaryocyte-specific ketone body transporter monocarboxylate transporter 1 (MCT1) or pharmacological targeting of MCT1 blocked beta-OHB-induced thrombocytopoiesis in mice. A ketogenesis-promoting diet alleviated CIT in mouse models. Moreover, a ketogenic diet modestly increased platelet counts without causing thrombocytosis in healthy volunteers, and a ketogenic lifestyle inversely correlated with CIT in patients with cancer. Together, we provide mechanistic insights into a ketone body-MCT1-BDH-histone acetylation-platelet biogenesis axis in megakaryocytes and propose a non-toxic, low-cost dietary intervention for combating CIT.
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| 3. |
- Cohen, Samuel I A, et al.
(author)
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A molecular chaperone breaks the catalytic cycle that generates toxic Aβ oligomers.
- 2015
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In: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9985 .- 1545-9993. ; 22:3, s. 207-213
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Journal article (peer-reviewed)abstract
- Alzheimer's disease is an increasingly prevalent neurodegenerative disorder whose pathogenesis has been associated with aggregation of the amyloid-β peptide (Aβ42). Recent studies have revealed that once Aβ42 fibrils are generated, their surfaces effectively catalyze the formation of neurotoxic oligomers. Here we show that a molecular chaperone, a human Brichos domain, can specifically inhibit this catalytic cycle and limit human Aβ42 toxicity. We demonstrate in vitro that Brichos achieves this inhibition by binding to the surfaces of fibrils, thereby redirecting the aggregation reaction to a pathway that involves minimal formation of toxic oligomeric intermediates. We verify that this mechanism occurs in living mouse brain tissue by cytotoxicity and electrophysiology experiments. These results reveal that molecular chaperones can help maintain protein homeostasis by selectively suppressing critical microscopic steps within the complex reaction pathways responsible for the toxic effects of protein misfolding and aggregation.
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| 4. |
- Cukalevski, Risto, et al.
(author)
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The A beta 40 and A beta 42 peptides self-assemble into separate homomolecular fibrils in binary mixtures but cross-react during primary nucleation
- 2015
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In: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6539 .- 2041-6520. ; 6:7, s. 4215-4233
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Journal article (peer-reviewed)abstract
- The assembly of proteins into amyloid fibrils, a phenomenon central to several currently incurable human diseases, is a process of high specificity that commonly tolerates only a low level of sequence mismatch in the component polypeptides. However, in many cases aggregation-prone polypeptides exist as mixtures with variations in sequence length or post-translational modifications; in particular amyloid beta (A beta) peptides of variable length coexist in the central nervous system and possess a propensity to aggregate in Alzheimer's disease and related dementias. Here we have probed the co-aggregation and cross-seeding behavior of the two principal forms of A beta, A beta 40 and A beta 42 that differ by two hydrophobic residues at the C-terminus. We find, using isotope-labeling, mass spectrometry and electron microscopy that they separate preferentially into homomolecular pure A beta 42 and A beta 40 structures during fibril formation from mixed solutions of both peptides. Although mixed fibrils are not formed, the kinetics of amyloid formation of one peptide is affected by the presence of the other form. In particular monomeric A beta 42 accelerates strongly the aggregation of A beta 40 in a concentration-dependent manner. Whereas the aggregation of each peptide is catalyzed by low concentrations of preformed fibrils of the same peptide, we observe a comparably insignificant effect when A beta 42 fibrils are added to A beta 40 monomer or vice versa. Therefore we conclude that fibril-catalysed nucleus formation and elongation are highly sequence specific events but A beta 40 and A beta 42 interact during primary nucleation. These results provide a molecular level description of homomolecular and heteromolecular aggregation steps in mixtures of polypeptide sequence variants.
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| 5. |
- Fang, Evandro F., et al.
(author)
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A research agenda for ageing in China in the 21st century (2nd edition): Focusing on basic and translational research, long-term care, policy and social networks.
- 2020
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In: Ageing Research Reviews. - : Elsevier BV. - 1568-1637. ; 64
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Journal article (peer-reviewed)abstract
- One of the key issues facing public healthcare is the global trend of an increasingly ageing society which continues to present policy makers and caregivers with formidable healthcare and socio-economic challenges. Ageing is the primary contributor to a broad spectrum of chronic disorders all associated with a lower quality of life in the elderly. In 2019, the Chinese population constituted 18 % of the world population, with 164.5 million Chinese citizens aged 65 and above (65+), and 26 million aged 80 or above (80+). China has become an ageing society, and as it continues to age it will continue to exacerbate the burden borne by current family and public healthcare systems. Major healthcare challenges involved with caring for the elderly in China include the management of chronic non-communicable diseases (CNCDs), physical frailty, neurodegenerative diseases, cardiovascular diseases, with emerging challenges such as providing sufficient dental care, combating the rising prevalence of sexually transmitted diseases among nursing home communities, providing support for increased incidences of immune diseases, and the growing necessity to provide palliative care for the elderly. At the governmental level, it is necessary to make long-term strategic plans to respond to the pressures of an ageing society, especially to establish a nationwide, affordable, annual health check system to facilitate early diagnosis and provide access to affordable treatments. China has begun work on several activities to address these issues including the recent completion of the of the Ten-year Health-Care Reform project, the implementation of the Healthy China 2030 Action Plan, and the opening of the National Clinical Research Center for Geriatric Disorders. There are also societal challenges, namely the shift from an extended family system in which the younger provide home care for their elderly family members, to the current trend in which young people are increasingly migrating towards major cities for work, increasing reliance on nursing homes to compensate, especially following the outcomes of the ‘one child policy’ and the ‘empty-nest elderly’ phenomenon. At the individual level, it is important to provide avenues for people to seek and improve their own knowledge of health and disease, to encourage them to seek medical check-ups to prevent/manage illness, and to find ways to promote modifiable health-related behaviors (social activity, exercise, healthy diets, reasonable diet supplements) to enable healthier, happier, longer, and more productive lives in the elderly. Finally, at the technological or treatment level, there is a focus on modern technologies to counteract the negative effects of ageing. Researchers are striving to produce drugs that can mimic the effects of ‘exercising more, eating less’, while other anti-ageing molecules from molecular gerontologists could help to improve ‘healthspan’ in the elderly. Machine learning, ‘Big Data’, and other novel technologies can also be used to monitor disease patterns at the population level and may be used to inform policy design in the future. Collectively, synergies across disciplines on policies, geriatric care, drug development, personal awareness, the use of big data, machine learning and personalized medicine will transform China into a country that enables the most for its elderly, maximizing and celebrating their longevity in the coming decades. This is the 2nd edition of the review paper (Fang EF et al., Ageing Re. Rev. 2015).
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| 6. |
- Flagmeier, Patrick, et al.
(author)
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Direct measurement of lipid membrane disruption connects kinetics and toxicity of Aβ42 aggregation
- 2020
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In: Nature Structural and Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 27:10, s. 886-891
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Journal article (peer-reviewed)abstract
- The formation of amyloid deposits in human tissues is a defining feature of more than 50 medical disorders, including Alzheimer’s disease. Strong genetic and histological evidence links these conditions to the process of protein aggregation, yet it has remained challenging to identify a definitive connection between aggregation and pathogenicity. Using time-resolved fluorescence microscopy of individual synthetic vesicles, we show for the Aβ42 peptide implicated in Alzheimer’s disease that the disruption of lipid bilayers correlates linearly with the time course of the levels of transient oligomers generated through secondary nucleation. These findings indicate a specific role of oligomers generated through the catalytic action of fibrillar species during the protein aggregation process in driving deleterious biological function and establish a direct causative connection between amyloid formation and its pathological effects.
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| 7. |
- Meisl, Georg, et al.
(author)
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Differences in nucleation behavior underlie the contrasting aggregation kinetics of the Aβ40 and Aβ42 peptides.
- 2014
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In: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 111:26, s. 9384-9389
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Journal article (peer-reviewed)abstract
- The two major forms of the amyloid-beta (Aβ) peptide found in plaques in patients suffering from Alzheimer's disease, Aβ40 and Aβ42, only differ by two amino acids in the C-terminal region, yet they display markedly different aggregation behavior. The origins of these differences have remained challenging to connect to specific molecular-level processes underlying the aggregation reaction. In this paper we use a general strategy to apply the conventional workflow of chemical kinetics to the aggregation of the Aβ40 peptide to identify the differences between Aβ40 and Aβ42 in terms of the microscopic determinants of the aggregation reaction. Our results reveal that the major source of aggregates in the case of Aβ40 is a fibril-catalyzed nucleation process, the multistep nature of which is evident through its saturation behavior. Moreover, our results show that the significant differences in the observed behavior of the two proteins originate not simply from a uniform increase in all microscopic rates for Aβ42 compared with Aβ40, but rather are due to a shift of more than one order of magnitude in the relative importance of primary nucleation versus fibril-catalyzed secondary nucleation processes. This analysis sheds light on the microscopic determinants of the aggregation behavior of the principal forms of Aβ and outlines a general approach toward achieving an understanding at the molecular level of the aberrant deposition of insoluble peptides in neurodegenerative disorders.
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| 8. |
- Meisl, Georg, et al.
(author)
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Modulation of electrostatic interactions to reveal a reaction network unifying the aggregation behaviour of the Aβ42 peptide and its variants
- 2017
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In: Chemical Science. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 8:6, s. 4352-4362
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Journal article (peer-reviewed)abstract
- The aggregation of the amyloid β peptide (Aβ42), which is linked to Alzheimer's disease, can be altered significantly by modulations of the peptide's intermolecular electrostatic interactions. Variations in sequence and solution conditions have been found to lead to highly variable aggregation behaviour. Here we modulate systematically the electrostatic interactions governing the aggregation kinetics by varying the ionic strength of the solution. We find that changes in the solution ionic strength induce a switch in the reaction pathway, altering the dominant mechanisms of aggregate multiplication. This strategy thereby allows us to continuously sample a large space of different reaction mechanisms and develop a minimal reaction network that unifies the experimental kinetics under a wide range of different conditions. More generally, this universal reaction network connects previously separate systems, such as charge mutants of the Aβ42 peptide, on a continuous mechanistic landscape, providing a unified picture of the aggregation mechanism of Aβ42.
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| 9. |
- Meisl, Georg, et al.
(author)
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Quantitative analysis of intrinsic and extrinsic factors in the aggregation mechanism of Alzheimer-associated Aβ-peptide.
- 2016
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 6
-
Journal article (peer-reviewed)abstract
- Disease related mutations and environmental factors are key determinants of the aggregation mechanism of the amyloid-β peptide implicated in Alzheimer's disease. Here we present an approach to investigate these factors through acquisition of highly reproducible data and global kinetic analysis to determine the mechanistic influence of intrinsic and extrinsic factors on the Aβ aggregation network. This allows us to translate the shift in macroscopic aggregation behaviour into effects on the individual underlying microscopic steps. We apply this work-flow to the disease-associated Aβ42-A2V variant, and to a variation in pH as examples of an intrinsic and an extrinsic perturbation. In both cases, our data reveal a shift towards a mechanism in which a larger fraction of the reactive flux goes via a pathway that generates potentially toxic oligomeric species in a fibril-catalyzed reaction. This is in agreement with the finding that Aβ42-A2V leads to early-onset Alzheimer's disease and enhances neurotoxicity.
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| 10. |
- Saar, Kadi L., et al.
(author)
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On-chip label-free protein analysis with downstream electrodes for direct removal of electrolysis products
- 2017
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In: Lab on a Chip. - : Royal Society of Chemistry (RSC). - 1473-0197 .- 1473-0189. ; 18:1, s. 162-170
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Journal article (peer-reviewed)abstract
- The ability to apply highly controlled electric fields within microfluidic devices is valuable as a basis for preparative and analytical processes. A challenge encountered in the context of such approaches in conductive media, including aqueous buffers, is the generation of electrolysis products at the electrode/liquid interface which can lead to contamination, perturb fluid flows and generally interfere with the measurement process. Here, we address this challenge by designing a single layer microfluidic device architecture where the electric potential is applied outside and downstream of the microfluidic device while the field is propagated back to the chip via the use of a co-flowing highly conductive electrolyte solution that forms a stable interface at the separation region of the device. The co-flowing electrolyte ensures that all the generated electrolysis products, including Joule heat and gaseous products, are flowed away from the chip without coming into contact with the analytes while the single layer fabrication process where all the structures are defined lithographically allows producing the devices in a simple yet highly reproducible manner. We demonstrate that by allowing stable and effective application of electric fields in excess of 100 V cm-1, the described platform provides the basis for rapid separation of heterogeneous mixtures of proteins and protein complexes directly in their native buffers as well as for the simultaneous quantification of their charge states. We illustrate this by probing the interactions in a mixture of an amyloid forming protein, amyloid-β, and a molecular chaperone, Brichos, known to inhibit the process of amyloid formation. The availability of a platform for applying stable electric fields and its compatibility with single-layer soft-lithography processes opens up the possibility of separating and analysing a wide range of molecules on chip, including those with similar electrophoretic mobilities.
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| 11. |
- Törnquist, Mattias, et al.
(author)
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Secondary nucleation in amyloid formation
- 2018
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In: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 54:63, s. 8667-8684
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Journal article (peer-reviewed)abstract
- Nucleation of new peptide and protein aggregates on the surfaces of amyloid fibrils of the same peptide or protein has emerged in the past two decades as a major pathway for both the generation of molecular species responsible for cellular toxicity and for the autocatalytic proliferation of peptide and protein aggregates. A key question in current research is the molecular mechanism and driving forces governing such processes, known as secondary nucleation. In this context, the analogies with other self-assembling systems for which monomer-dependent secondary nucleation has been studied for more than a century provide a valuable source of inspiration. Here, we present a short overview of this background and then review recent results regarding secondary nucleation of amyloid-forming peptides and proteins, focusing in particular on the amyloid β peptide (Aβ) from Alzheimer's disease, with some examples regarding α-synuclein from Parkinson's disease. Monomer-dependent secondary nucleation of Aβ was discovered using a combination of kinetic experiments, global analysis, seeding experiments and selective isotope-enrichment, which pinpoint the monomer as the origin of new aggregates in a fibril-catalyzed reaction. Insights into driving forces are gained from variations of solution conditions, temperature and peptide sequence. Selective inhibition of secondary nucleation is explored as an effective means to limit oligomer production and toxicity. We also review experiments aimed at finding interaction partners of oligomers generated by secondary nucleation in an ongoing aggregation process. At the end of this feature article we bring forward outstanding questions and testable mechanistic hypotheses regarding monomer-dependent secondary nucleation in amyloid formation.
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| 12. |
- Wu, Jieyu, et al.
(author)
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Disruption of the Clock Component Bmal1 in Mice Promotes Cancer Metastasis through the PAI-1-TGF-beta-myoCAF-Dependent Mechanism
- 2023
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In: Advanced Science. - : WILEY. - 2198-3844. ; 10:24
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Journal article (peer-reviewed)abstract
- The circadian clock in animals and humans plays crucial roles in multiple physiological processes. Disruption of circadian homeostasis causes detrimental effects. Here, it is demonstrated that the disruption of the circadian rhythm by genetic deletion of mouse brain and muscle ARNT-like 1 (Bmal1) gene, coding for the key clock transcription factor, augments an exacerbated fibrotic phenotype in various tumors. Accretion of cancer-associated fibroblasts (CAFs), especially the alpha smooth muscle actin positive myoCAFs, accelerates tumor growth rates and metastatic potentials. Mechanistically, deletion of Bmal1 abrogates expression of its transcriptionally targeted plasminogen activator inhibitor-1 (PAI-1). Consequently, decreased levels of PAI-1 in the tumor microenvironment instigate plasmin activation through upregulation of tissue plasminogen activator and urokinase plasminogen activator. The activated plasmin converts latent TGF-beta into its activated form, which potently induces tumor fibrosis and the transition of CAFs into myoCAFs, the latter promoting cancer metastasis. Pharmacological inhibition of the TGF-beta signaling largely ablates the metastatic potentials of colorectal cancer, pancreatic ductal adenocarcinoma, and hepatocellular carcinoma. Together, these data provide novel mechanistic insights into disruption of the circadian clock in tumor growth and metastasis. It is reasonably speculated that normalization of the circadian rhythm in patients provides a novel paradigm for cancer therapy.
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| 13. |
- Yang, Xiaoting
(author)
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Amyloid beta aggregation kinetics : The role of intrinsic and extrinsic factors.
- 2016
-
Doctoral thesis (other academic/artistic)abstract
- Cerebral senile plaque is one of the main pathologies of Alzheimer's disease (AD). The amyloid cascade hypothesis suggests that the aggregation of amyloid beta (Abeta) peptide is involved in the pathogenesis of AD, which is supported by the fact that Abeta overexpression or production of more aggregation-prone variants lead to early-onset dementia. In this work, we mainly studied the in vitro Abeta aggregation kinetics, to investigate the mechanistic shift as a result of intrinsic factors and extrinsic factors. We employ a fluorescence probe Thioflavin T (ThT) to follow the aggregation kinetics. The aggregation half-time is then extracted and plotted against monomer concentration. By fitting the curve with a power function, a scaling exponent is extracted and reflects the aggregation monomer dependence. The ThT data can be globally fitted using master equations to determine the dominant aggregation reaction step at the microscopic level. Circular dichroism spectroscopy and cryogenic transmission electron microscopy are used to study the fibril structure transition and morphology. Surface plasmon resonance and mass spectrometry provide information of molecular interaction and the latter one is also used to identify peptide segments of the soluble and insoluble Abeta species. Our results show a two-step saturated secondary nucleation dominated mechanism in several cases: Abeta mutants E22K, E22Q, E22G, D23N and A2V, which link to an early-onset of AD, Abeta40 aggregation at high monomer concentration (> 30 uM, pH 7.4), and Abeta42 aggregation at high ionic strength (> 92 mM) and at pH 7.4. The mechanistic shift in these cases is mainly attributed to a reduced repulsion between monomers and other aggregating species due to decreased absolute charges from point mutation or pH shifting to a value close to the isoelectric point, or due to increased ionic strength by adding salt. This effect is combined with additional hydrophobic effect or other side chain properties in some cases to reach a more enhanced secondary nucleation. The secondary nucleation that produces enormous amount of toxic oligomers is found to be severely inhibited by a chaperone protein, Brichos, through specifically binding to the fibril surface and blocking the catalytic cycle. In our co-aggregation work, the most abundant Abeta variants, Abeta40 and Abeta42 that differ in length at C-terminus, do not co-aggregate and do not form mixed fibrils. The result implies that Abeta40 and Abeta42 interact exclusively at primary nucleation level and Abeta aggregation is a highly selective process that tolerates a low level of sequence mismatch in C-terminus.
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| 14. |
- Yang, Xiaoting, et al.
(author)
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On the role of sidechain size and charge in the aggregation of Aβ42 with familial mutations
- 2018
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 115:26, s. 5849-5858
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Journal article (peer-reviewed)abstract
- The aggregation of the amyloid-β (Aβ) peptide is linked to the pathogenesis of Alzheimer’s disease (AD). In particular, some point mutations within Aβ are associated with early-onset familial Alzheimer’s disease. Here we set out to explore how the physical properties of the altered side chains, including their sizes and charges, affect the molecular mechanisms of aggregation. We focus on Aβ42 with familial mutations—A21G (Flemish), E22K (Italian), E22G (Arctic), E22Q (Dutch), and D23N (Iowa)—which lead to similar or identical pathology with sporadic AD or severe cerebral amyloid angiopathy. Through global kinetic analysis, we find that for the E22K, E22G, E22Q, and D23N mutations, the acceleration of the overall aggregation originates primarily from the modulation of the nucleation processes, in particular secondary nucleation on the surface of existing fibrils, whereas the elongation process is not significantly affected. Remarkably, the D23 position appears to be responsible for most of the charge effects during nucleation, while the size of the side chain at the E22 position plays a more significant role than its charge. Thus, we have developed a kinetic approach to determine the nature and the magnitude of the contribution of specific residues to the rate of individual steps of the aggregation reaction, through targeted mutations and variations in ionic strength. This strategy can help rationalize the effect of some disease-related mutations as well as yield insights into the mechanism of aggregation and the transition states of the wild-type protein.
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