| 1. |
- Bolognesi, B, et al.
(författare)
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The N-terminus of amyloid-beta plays a crucial role in its aggregation and toxicity
- 2010
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Ingår i: The FEBS Journal. - : Wiley-Blackwell. - 1742-464X .- 1742-4658. ; 277:Suppl. 1, s. 79-80
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The aggregation of Amyloid Beta (Aß) peptide into insolubleamyloid fibrils that deposit in the brain is one of the primarypathogenic events in Alzheimer’s disease. We have previouslyshown, using a Drosophila model of Aß toxicity, that the N terminus of the Aß peptide, despite being unstructured in themature Aß fibril, nonetheless affects Aß induced neurodegeneration in vivo. In order to understand the contribution of the N terminusof Aß to its aggregation behaviour, we have investigated anumber of rationally designed N-terminal mutants in vitro. We find that single amino acid mutations in this region affect significantlythe kinetics of Aß aggregation in vitro as measured by arange of spectroscopic techniques. Furthermore, we observe striking differences in the morphology of the aggregated speciesformed by these different Aß mutants when imaged with TEM or AFM and also in the ß-sheet content of their mature fibrils. Interestingly, mutants with an increased net charge or lower hydrophobicity tend to show slower aggregation kinetics, and to form more ordered aggregates whereas mutations that reduce net charge or increase hydrophobicity favour faster aggregation kinetics and poorly structured aggregates. In addition, the exposed hydrophobicity of aggregates formed in the early stages of aggregation is correlated to their toxicity. These findings demonstrate not only that the N-terminus of the Aß peptide plays a crucial role in its aggregation and toxicity but also suggest that this region of Aß may modulate in vivo toxicity by altering the conformations of aggregates that it forms.
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| 2. |
- Brorsson, Ann-Christin, et al.
(författare)
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Intrinsic determinants of neurotoxic aggregate formation by the amyloid beta peptide
- 2010
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Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 98:8, s. 1677-84
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Tidskriftsartikel (refereegranskat)abstract
- The extent to which proteins aggregate into distinct structures ranging from prefibrillar oligomers to amyloid fibrils is key to the pathogenesis of many age-related degenerative diseases. We describe here for the Alzheimer's disease-related amyloid beta peptide (Abeta) an investigation of the sequence-based determinants of the balance between the formation of prefibrillar aggregates and amyloid fibrils. We show that by introducing single-point mutations, it is possible to convert the normally harmless Abeta40 peptide into a pathogenic species by increasing its relative propensity to form prefibrillar but not fibrillar aggregates, and, conversely, to abolish the pathogenicity of the highly neurotoxic E22G Abeta42 peptide by reducing its relative propensity to form prefibrillar species rather than mature fibrillar ones. This observation can be rationalized by the demonstration that whereas regions of the sequence of high aggregation propensity dominate the overall tendency to aggregate, regions with low intrinsic aggregation propensities exert significant control over the balance of the prefibrillar and fibrillar species formed, and therefore play a major role in determining the neurotoxicity of the Abeta peptide.
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| 3. |
- Brorsson, Ann-Christin, et al.
(författare)
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Methods and models in neurodegenerative and systemic protein aggregation diseases
- 2010
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Ingår i: Frontiers in bioscience : a journal and virtual library. - : Frontiers in Bioscience Publications. - 1093-4715. ; 15, s. 373-396
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Forskningsöversikt (refereegranskat)abstract
- Protein misfolding and aggregation are implicated in a wide range of increasingly prevalent human diseases ranging from dementia to diabetes. In this review we discuss the current experimental strategies that are being employed in the investigation of the pathogenesis of three important protein misfolding disorders. The first, Alzheimers disease (AD), is the most prevalent neurodegenerative disease and is thought to be initiated by the aggregation of a natively unstructured peptide called amyloid beta (Abeta). We discuss methods for the characterization of the aggregation properties of Abeta in vitro and how the results of such experiments can be correlated with data from animal models of disease. We then consider another form of amyloidosis, where a systemic distribution of amyloid deposit is caused by aggregation and deposition of mutational variants of lysozyme. We describe how experiments in vitro, and more recently in vivo, have provided insights into the origins of this disease. Finally we outline the varied paradigms that have been employed in the study of the serpinopathies, and in particular, a dementia caused by neuroserpin polymerization.
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| 4. |
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| 5. |
- Brorsson, S., 1973-, et al.
(författare)
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Two different sets of handexercises improved grip strength after after eight weeks in patients with arthritis
- 2014
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Ingår i: Annals of the Rheumatic Diseases. - London : BMJ Books. - 0003-4967 .- 1468-2060. ; 73:Suppl. 2, s. 1210-1210
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Tidskriftsartikel (refereegranskat)abstract
- Background Hand function measured as grip force and finger extension force is often impaired in patients with rheumatoid arthritis (RA) and hand osteoarthritis (HOA) affecting performance of daily activities why hand exercises are recommended. A number of hand exercises are often used in the clinic but there is little information about “the effects of a minimal set of hand exercises” and if the choice of exercises is important to improve strength and function in the hand.Objectives To study the effect on grip- and finger extension strength and patient reported hand function from two different sets of handexercises performed over 8 weeks using a randomized study design.Methods Female patients with arthritis (RA and HOA, n=121) were randomly assigned to two different sets of handexercises (HE) for 8 weeks. The four hand exercises applied in the program were exercises commonly used in traditional hand training programs. The exercises were split into two groups depending on if the muscle activation (measured with EMG) were greater in forearm flexor (HE I, n=62) or in extensor muscles (HE II, n=59) (REF). HE I: isolated finger opposition (digits II-V) and rolling the putty with a flat hand, HE II: squeezing the putty and finger extension with putty resistance. The two HE were performed daily and each set was repeated 15 times, training time per day was maximum 5 minutes 7 days/week.Grip strength was measured with Grippit and finger extension strength with EX-it both validated instruments (unit: N). Pain was measured with a Visual Analogue Scale (VAS), 0-10 (best to worst). Hand functions were evaluated with the patient reported questionnaire Quick Disability Arm Shoulder and Hand (QuickDASH), 0-100 (best to worst).Results Mean grip strength (p=0.01) and mean finger extension force (p=0.004) increased after the training period in the group using HE I. In HE II the mean finger extension force increased (p=0.044), table 1. Hand function was stable over the training period.Table 1.Descriptive data of finger extension (EXIT) force and grip strength in the right hand, hand function (QuickDASH) and VAS pain presented as mean ± SD (min–max)Conclusions Five daily minutes with two hand exercises resulted increased grip strength and finger extension force after eight weeks. We suggest that hand exercises should be combined and selected to improve both flexor and extensor muscle strength of the forearm.
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| 6. |
- Kumita, Janet R, et al.
(författare)
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Disease-related amyloidogenic variants of human lysozyme trigger the unfolded protein response and disturb eye development in Drosophila melanogaster
- 2012
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Ingår i: The FASEB Journal. - : Federation of American Society of Experimental Biology (FASEB). - 0892-6638 .- 1530-6860. ; 26:1, s. 192-202
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Tidskriftsartikel (refereegranskat)abstract
- We have created a Drosophila model of lysozyme amyloidosis to investigate the in vivo behavior of disease-associated variants. To achieve this objective, wild-type (WT) protein and the amyloidogenic variants F57I and D67H were expressed in Drosophila melanogaster using the UAS-gal4 system and both the ubiquitous and retinal expression drivers Act5C-gal4 and gmr-gal4. The nontransgenic w(1118) Drosophila line was used as a control throughout. We utilized ELISA experiments to probe lysozyme protein levels, scanning electron microscopy for eye phenotype classification, and immunohistochemistry to detect the unfolded protein response (UPR) activation. We observed that expressing the destabilized F57I and D67H lysozymes triggers UPR activation, resulting in degradation of these variants, whereas the WT lysozyme is secreted into the fly hemolymph. Indeed, the level of WT was up to 17 times more abundant than the variant proteins. In addition, the F57I variant gave rise to a significant disruption of the eye development, and this correlated to pronounced UPR activation. These results support the concept that the onset of familial amyloid disease is linked to an inability of the UPR to degrade completely the amyloidogenic lysozymes prior to secretion, resulting in secretion of these destabilized variants, thereby leading to deposition and associated organ damage.-Kumita, J. R., Helmfors, L., Williams, J., Luheshi, L. M., Menzer, L., Dumoulin, M., Lomas, D. A., Crowther, D. C., Dobson, C. M., Brorsson, A.-C. Disease-related amyloidogenic variants of human lysozyme trigger the unfolded protein response and disturb eye development in Drosophila melanogaster.
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| 7. |
- Luheshi, Leila M., et al.
(författare)
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Sequestration of the A beta Peptide Prevents Toxicity and Promotes Degradation In Vivo
- 2010
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Ingår i: PLoS biology. - : Public Library of Science (PLoS). - 1544-9173 .- 1545-7885. ; 8:3, s. e1000334-
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Tidskriftsartikel (refereegranskat)abstract
- Protein aggregation, arising from the failure of the cell to regulate the synthesis or degradation of aggregation-prone proteins, underlies many neurodegenerative disorders. However, the balance between the synthesis, clearance, and assembly of misfolded proteins into neurotoxic aggregates remains poorly understood. Here we study the effects of modulating this balance for the amyloid-beta (A beta) peptide by using a small engineered binding protein (Z(A beta 3)) that binds with nanomolar affinity to A beta, completely sequestering the aggregation-prone regions of the peptide and preventing its aggregation. Co-expression of Z(A beta 3) in the brains of Drosophila melanogaster expressing either A beta(42) or the aggressive familial Alzheimer's disease (AD) associated E22G variant of A beta(42) abolishes their neurotoxic effects. Biochemical analysis indicates that monomer A beta binding results in degradation of the peptide in vivo. Complementary biophysical studies emphasize the dynamic nature of A beta aggregation and reveal that Z(A beta 3) not only inhibits the initial association of A beta monomers into oligomers or fibrils, but also dissociates pre-formed oligomeric aggregates and, although very slowly, amyloid fibrils. Toxic effects of peptide aggregation in vivo can therefore be eliminated by sequestration of hydrophobic regions in monomeric peptides, even when these are extremely aggregation prone. Our studies also underline how a combination of in vivo and in vitro experiments provide mechanistic insight with regard to the relationship between protein aggregation and clearance and show that engineered binding proteins may provide powerful tools with which to address the physiological and pathological consequences of protein aggregation.
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| 8. |
- Sorensen, J. S., et al.
(författare)
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Islet autoantibodies and residual beta cell function in type 1 diabetes children followed for 3-6 years
- 2012
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Ingår i: Diabetes Research and Clinical Practice. - : Elsevier BV. - 1872-8227 .- 0168-8227. ; 96:2, s. 204-210
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Tidskriftsartikel (refereegranskat)abstract
- Aims: To test if islet autoantibodies at diagnosis of type 1 diabetes (T1DM) and after 3-6 years with T1D predict residual beta-cell function (RBF) after 3-6 years with T1D. Methods: T1D children (n = 260, median age at diagnosis 9.4, range 0.9-14.7 years) were tested for GAD65, IA-2, ZnT8R, ZnT8W and ZnT8Q autoantibodies (A) at diagnosis, and 3-6 years after diagnosis when also fasting and stimulated RBF were determined. Results: For every 1-year increase in age at diagnosis of TID, the odds of detectable C-peptide increased 1.21 (1.09, 1.34) times for fasting C-peptide and 1.28 (1.15, 1.42) times for stimulated C-peptide. Based on a linear model for subjects with no change in IA-2A levels, the odds of detectable C-peptide were 35% higher than for subjects whose IA-2A levels decreased by half (OR = 1.35 (1.09, 1.67), p = 0.006); similarly for ZnT8WA (OR = 1.39 (1.09, 1.77), p = 0.008) and ZnT8QA (OR = 1.55 (1.06, 2.26) p = 0.024). Such relationship was not detected for GADA or ZnT8RA. All OR adjusted for confounders. Conclusions: Age at diagnosis with T1D was the major predictor of detectable C-peptide 3-6 years post-diagnosis. Decreases in IA-2A, and possibly ZnT8A, levels between diagnosis and post-diagnosis were associated with a reduction in RBF post-diagnosis. (C) 2012 Elsevier Ireland Ltd. All rights reserved.
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