If you have a question about this talk, please contact Dr Georg Krainer.. Many bacteria produce functional amyloid, i.e. proteins which are secreted through dedicated export systems and self-assemble on the bacterial surface, often with the help of nucleator proteins. These amyloid proteins serve a diversity of purposes, but the most prominent one appears to be structural stability; for example, overexpression of the amyloid-forming protein FapC in Pseudomonas species strengthens bacterial biofilm against mechanical insults, increases hydrophobicity and protects against desiccation. Similar properties are ascribed to the curli-forming protein CsgA from E. coli. Unlike pathological amyloid, functional amyloid has been under evolutionary pressure to self-assemble efficiently (i.e. in a single "fast track") to very stable higher-order structures. My lab is engaged in an effort to understand the molecular basis for these properties in more detail and I will present recent progress in this ...
We have revisited the well-studied heat and acidic amyloid fibril formation pathway (pH 1.6, 65 °C) of hen egg-white lysozyme (HEWL) to map the barriers of the misfolding and amyloidogenesis pathways. A comprehensive kinetic mechanism is presented where all steps involving protein hydrolysis, fragmentation, assembly and conversion into amyloid fibrils are accounted for. Amyloid fibril formation of lysozyme has multiple kinetic barriers. First, HEWL unfolds within minutes, followed by irreversible steps of partial acid hydrolysis affording a large amount of nicked HEWL, the 49-101 amyloidogenic fragment and a variety of other species over 5-40 h. Fragmentation forming the 49-101 fragment is a requirement for efficient amyloid fibril formation, indicating that it forms the rate-determining nucleus. Nicked full-length HEWL is recruited efficiently into amyloid fibrils in the fibril growth phase or using mature fibrils as seeds, which abolished the lag phase completely. Mature amyloid fibrils of ...
Amyloid formation is inherent property of proteins which under certain circumstances can become a pathologic feature of a group of diseases called amyloidosis. There are about 30 known human amyloidosis and more than 27 identified proteins involved in these pathologies. Besides these proteins, there are a growing number of proteins non-related to diseases shown to form amyloid-like structures in vitro, which make them excellent tools for studying amyloid formation mechanisms, physicochemical properties of different amyloid species and the nature of their influence on tissues and cells. It is important to understand the mechanisms by which amyloids interact with different types of cells, as the leading hypothesis in amyloid field suggests that amyloids and especially their intermediate states are the main harmful, toxic species causing tissue and cell degeneration.. Using de-novo synthesized protein albebetin as a model of amyloidogenic protein, we demonstrated that it forms amyloid-like ...
Author: Olzscha, H. et al.; Genre: Journal Article; Published in Print: 2011-01-07; Title: Amyloid-like Aggregates Sequester Numerous Metastable Proteins with Essential Cellular Functions
The structures of amyloid fibrils and oligomers represent a vast frontier, of yet unknown scope. The fibrils and aggregates that amyloidogenic peptides and proteins form are rich in β-sheets, and their structures are tremendously important in amyloid diseases. Many structures of amyloid fibrils have been discovered by solid-state NMR spectroscopy of amyloidogenic peptides and proteins and by X-ray crystallography of smaller fragments.1-4 Studying amyloid oligomer structures at high resolution is challenging, because amyloid oligomers are heterogeneous and dynamic, forming various species of different sizes and morphologies. Although a few structures of amyloid oligomers have been discovered in the last decade, there are not enough to provide a full understanding of amyloid assemblies.5-7 Our laboratory has pioneered the use of macrocyclic β-sheets as a tool for exploring the structures of amyloid oligomers. In collaboration with the Eisenberg group, we began using X-ray crystallography to ...
The use of small carbohydrates that stabilize proteins from misfolding is important from pharmaceutical point of view. We have investigated the role of small isomeric amino sugars on the in vitro aggregation of insulin amyloid. Using mass spectrometry, we screened 6 isomeric aminosugars for their role on inhibition of insulin amyloid formation and the results were compared with transmission electron microscopy imaging. We found that three N-acetylamino sugars promote insulin fibril formation. Among three isomeric aminosugars studied, only galactosamine showed few fibrils whereas other two isomers showed enhanced fibrils. The results demonstrated here may contribute to future designing of small amine derivatised galactose sugars as amyloid inhibitors and understanding their action ...
Researchers first injected transgenic mice expressing human IAPP with preformed fibrils of synthetic IAPP, proIAPP, or beta-amyloid. After 10 months on a high-fat diet, tissue was analyzed using an amyloid-specific dye. The number of islets with amyloid was significantly increased compared to controls by all three types of fibrils, and the amyloid consisted of IAPP in all groups. No amyloid deposits were found in the spleen, kidney, liver, heart, or lungs. The results demonstrate for the first time that fibril injections could seed amyloid formation in the pancreas and also that brain amyloid could cross-seed fibril formation in the pancreas.. In subsequent experiments the investigators analyzed human tissues from the pancreas and brain. Using antibody-based methods, they found that pancreas sections with islet amyloid from patients diagnosed with T2D showed no beta-amyloid immunoreactivity, whereas all samples were immunoreactive for IAPP.. To further investigate whether IAPP and beta-amyloid ...
Misfolding and aggregation of normally soluble proteins into amyloid fibrils and their deposition and accumulation underlies a variety of clinically significant diseases. Fibrillar aggregates with amyloid-like properties can also be generated in vitro from pure proteins and peptides, including those not known to be associated with amyloidosis. Whereas biophysical studies of amyloid-like fibrils formed in vitro have provided important insights into the molecular mechanisms of amyloid generation and the structural properties of the fibrils formed, amyloidogenic proteins are typically exposed to mild or more extreme denaturing conditions to induce rapid fibril formation in vitro. Whether the structure of the resulting assemblies is representative of their natural in vivo counterparts, thus, remains a fundamental unresolved issue. Here we show using Fourier transform infrared spectroscopy that amyloid-like fibrils formed in vitro from natively folded or unfolded β2-microglobulin (the protein ...
Amyloidosis is a protein conformational disorder in which amyloid fibrils accumulate in the extracellular space and induce organ dysfunction. Recently, two different amyloidogenic proteins, transthyretin (TTR) and apolipoprotein A-I (Apo A-I), were identified in amyloid deposits in knee joints in patients with knee osteoarthritis (OA). However, clinicopathological differences related to those two kinds of amyloid deposits in the knee joint remain to be clarified. Here, we investigated the clinicopathological features related to these knee amyloid deposits associated with knee OA and the biochemical characteristics of the amyloid deposits. We found that all of our patients with knee OA had amyloid deposits in the knee joints, especially in the meniscus, and those deposits were primarily derived from TTR and/or Apo A-I. Some patients with knee OA, however, had unclassified amyloid deposits. One of our interesting observations concerned the different effects of aging on each type of amyloid formed. ...
BACKGROUND: The conversion of soluble peptides and proteins into polymeric amyloid structures is a hallmark of many age-related degenerative disorders, including Alzheimers disease, type II diabetes and a variety of systemic amyloidoses. We report here that amyloid formation is linked to another major age-related phenomenon-prostate tissue remodelling in middle-aged and elderly men. METHODOLOGY/PRINCIPAL FINDINGS: By using multidisciplinary analysis of corpora amylacea inclusions in prostate glands of patients diagnosed with prostate cancer we have revealed that their major components are the amyloid forms of S100A8 and S100A9 proteins associated with numerous inflammatory conditions and types of cancer. In prostate protease rich environment the amyloids are stabilized by dystrophic calcification and lateral thickening. We have demonstrated that material closely resembling CA can be produced from S100A8/A9 in vitro under native and acidic conditions and shows the characters of amyloids. This ...
It has long been understood that amyloids can be lethal in systemic diseases. More recently, it has been accepted that local cerebral aggregation of the small peptide A beta is involved in the pathogenesis of Alzheimers disease. Protein aggregation, with the generation of small amyloid deposits in specific organs, also occurs outside the central nervous system and often is associated with increased cell death. In this review, we discuss two lesser known but common localized amyloid fibril-forming proteins: the polypeptide hormone islet amyloid polypeptide (IAPP) and the lactadherin-derived peptide medin. IAPP aggregates and induces the depletion of islet beta-cells in type 2 diabetes and in islets transplanted into type 1 diabetic subjects. Initial amyloid deposition occurs intracellularly and parts of this amyloid consist of proIAPP. Medin derived from lactadherin expressed by smooth muscle cells aggregates into amyloid in certain arteries, particularly the thoracic aortic media layer, and may ...
Amyloid accumulation in the brain of Alzheimers patients results from altered processing of the 39- to 43-amino acid amyloid protein (A). [1], [2]. The excessive accumulation of A peptides in AD may be due to enhanced endoproteolytic cleavage of membrane bound amyloid precursor protein (APP), over-expression of APP and/or decreased clearance of A from the central nervous system (CNS) [3]C[5]. Postmortem analyses of AD subjects reveal that amyloid plaques in the brain suffuse vascular cells in addition to the parenchymal. The ramifications of this vascular infiltration for AD has been less well analyzed than the parenchymal A, but has generated 61939-05-7 manufacture considerable interest with studies that -amyloid fibrils accumulate in small blood vessels, capillary vessels and arterioles of Rabbit Polyclonal to PRKY the human brain [6]C[8]. Cerebrovascular amyloid toxicity generally manifests itself in the break of the blood-brain-barrier and improved irritation in the cerebrovasculature [9], ...
In this study, we have compared the biological effects of different Aβ assemblies on primary mixed brain cultures to determine whether nonfibrillar or immature, prefibrillar forms of Aβ may be neurotoxic. This potentially important source of neuronal injury has been overlooked until very recently, perhaps because the neuropathological diagnosis of AD requires the presence of abundant fibrillar amyloid in the form of myriad neuritic plaques in postmortem brain tissue. Because mature amyloid plaques surrounded by dystrophic neurites, activated microglia, and reactive astrocytes are composed principally of Aβ fibrils, it has been generally assumed that fibrillar Aβ is the form most likely to be responsible for neuronal and glial injury in AD. The apparent importance of amyloid fibrils has been reinforced by cell culture studies that consistently show that the aggregation state of Aβ, most notably the formation of amyloid fibrils, is associated with neuronal alteration and loss (Pike et al., ...
Since 1998, a great deal of progress has been made towards determining and understanding the molecular structures of amyloid fibrils, including fibrils formed by the β-amyloid peptide that is...
Actually, the photo depicts amyloid plaques, a frequent topic in the context of Alzheimers disease. Pathologist William Lewis photo reminds us that amyloid can also appear in the heart.. Amyloidosis of the heart is a set of complex diseases caused by the accumulation of cellular proteins that form an amyloid plaque. Although http://www.oakleyonorder.com/ amyloidosis was described more than 100 years ago, the causative proteins were not identified until recent chemical analyses were conducted. This image shows an amyloid plaque stained with Congo red stain and viewed through a polarized lens. The optical properties of the amyloid-forming protein cause it to appear green, while other matrix materials within the plaque appear as orange and blue.. The photo, which was one of the winners of the FASEB (Federation of American Societies for Experimental Biology) 2013 BioArt competition, was featured on NIH director Francis Collins blog this week.. Lewis, who studies the effects of antiretroviral ...
We report on the photophysical and optical properties of a polyfluorene derivative (PFO) and its binding to the amyloid-forming protein insulin. The complexation is based on weak supramolecular interactions between amyloid fibrils and PFO in dissolved and aggregated forms. In particular, complexes of polyflu
Background The conversion of soluble peptides and proteins into polymeric amyloid structures is a hallmark of many age-related degenerative disorders, including Alzheimers disease, type II diabetes and a variety of systemic amyloidoses. We report here that amyloid formation is linked to another major age-related phenomenon - prostate tissue remodelling in middle-aged and elderly men.. Methodology/Principal Findings By using multidisciplinary analysis of corpora amylacea inclusions in prostate glands of patients diagnosed with prostate cancer we have revealed that their major components are the amyloid forms of S100A8 and S100A9 proteins associated with numerous inflammatory conditions and types of cancer. In prostate protease rich environment the amyloids are stabilized by dystrophic calcification and lateral thickening. We have demonstrated that material closely resembling CA can be produced from S100A8/A9 in vitro under native and acidic conditions and shows the characters of amyloids. This ...
A five-year trial at a Brisbane Hospital has increased the accuracy of diagnosing patients with amyloidosis, a group of rare and incurable diseases caused by abnormal protein deposits in tissues and organs.. Researchers from The University of Queensland and the Princess Alexandra Hospital Amyloidosis Centre used a new test to identify the specific protein that caused the damage in each patient.. Associate Professor Michelle Hill from the UQ Diamantina Institute said different amyloid conditions had different protein culprits, and required different treatments.. "For instance, in one type of amyloidosis known as AL, chemotherapy is required, but chemo is inappropriate and potentially harmful to patients with other amyloid conditions," Dr Hill said.. "In the trial we used cutting-edge techniques including laser-capture microdissection and tandem mass spectrometry to identify proteins in the amyloid deposits.. "This technique was recently reported by the Mayo Clinic in the United States as a new ...
Alzheon presents ALZ-801 data in oral session on the role of amyloid oligomers in Alzheimers Disease 10th Clinical Trials on Alzheimers Disease mtg.
Since its founding in 2003, Kinexis Inc. has pursued several lead development programs, including prokineticin receptor modulators and melanin concentrating hormone (MCH)-1 receptor antagonists. But the San Diego-based companys third lead program - licensed from the University of California at Irvine in 2004 - turned out to be the charm. The program was built around a platform to generate antibodies targeting oligomeric conformations of amyloid proteins, which form the hallmark plaques of Alzheimers disease. And in 2006, the amyloid oligomer program officially became Kinexiss primary focus at the urging of new CEO Kevin Anderson.
Background. Liver transplantation (LTx) is an accepted treatment for hereditary transthyretin (TTR) amyloidosis (ATTR). However, unforeseen heart complications, especially a rapid development of cardiomyopathy after LTx has affected mortality and morbidity. Recently, a relationship between ATTR-fibril composition and cardiomyopathy has been noted. The aim of this study was to investigate whether development of cardiomyopathy and heart failure in LTx ATTR amyloid patients is related to amyloid fibril composition.. Methods. Twenty-four patients with hereditary ATTR amyloidosis who had undergone LTx and have had their amyloid fibril type tested were available for the study. They had been examined by echocardiography including tissue Doppler and speckle tracking echocardiography before and after LTx. Patients were divided into two groups according to fibril composition, 10 patients with type A fibrils (a mixture of truncated and full-length TTR) and 14 patients with type B fibrils (full-length TTR ...
Andreas Bäumler. The protein forming plaques in Alzheimers patients is normally soluble. When the protein folds improperly, it forms amyloid deposits that are associated with brain inflammation. Until now, scientists have not been able to identify what causes this destructive, chronic inflammation.. Bäumler and his colleagues did not expect to be studying Alzheimers disease. They were studying inflammation of the gut caused by bacteria when they discovered that the innate immune system was being triggered by a structural feature of bacterial amyloids and not by the amino acids that make up the proteins in the biofilms.. "When we destroyed the ability of the proteins to aggregate, we no longer saw the same immune response," Bäumler said.. When the researchers figured out the amyloid structure was responsible for triggering the immune system, they decided to see whether the same immune response was being triggered by structurally identical amyloids associated with human disease. They chose to ...
While striatal amyloid may mark the late preclinical phase, Sebastian Palmqvist of Lund University, Sweden, made a case for CSF Aβ42 being one of the earliest preclinical markers of AD. Levels of this fluid biomarker drop as amyloid plaques accumulate in the brain, and this becomes apparent before amyloid PET scans turn positive, Palmqvist claimed. Previous cross-sectional studies had hinted at this, with some participants having low CSF Aβ42 in the absence of an amyloid PET signal, but it was unclear if all of these PET-negative individuals were on track for AD (see Fagan et al., 2009; Mattsson et al., 2015). Confusing matters further, at least one study reported finding a few people with positive amyloid scans and normal CSF Aβ42 (see Landau et al., 2013). To observe the relationship of the two markers over time, Palmqvist and colleagues Niklas Mattsson and Oskar Hansson at Lund stratified 437 ADNI 2 participants according to whether they were positive or negative on each. For brain ...
Because many types of bacteria depend on amyloid-rich curli to stick to host surfaces, disrupting these structures might open a new avenue for combating biofilms. Amyloid structures, which consist of aggregated fibers of insoluble protein in web-like sheets, are a substantial part of what makes curli so good at this task. Moreover, in addition to enhancing how well cells stick to surfaces, the aggregated fibers within curli help them to resist heat and chemical damage. More and more microbiologists admit to being intrigued by amyloid structures.
The generation and assembly of Aβ peptides into pathological aggregates is associated with neurodegenerative diseases including Alzheimers disease. Goal of this project was to better understand the dynamics of γ-secretase a key enzyme for the formation of Aβ peptides using large scale Molecular Dynamics simulations and how it associates with substrate molecules. Using the HPC system SuperMUC it was possible to characterize local and global motions of γ-secretase in atomic detail and how it is related to function. In addition, large scale simulations were employed to investigate the amyloid propagation mechanism at the tip of an already formed amyloid fragment. The kinetics and thermodynamics of the process were analyzed and compared to alternative amyloid secondary nucleation events.
DNA sequences encoding β-amyloid-related proteins associated with Alzheimers disease are disclosed. Also provided herein is a DNA sequence encoding a novel protease inhibitor. These sequences are used in producing or constructing recombinant β-amyloid core protein, β-amyloid-related proteins and recombinant or synthetic immunogenic peptides. Antibodies generated against the recombinant proteins or immunogenic peptides derived therefrom can be used for cerebral fluid or serum protein diagnosis of Alzheimers disease.
Amyloid oligomers are nonfibrillar polypeptide aggregates linked to diseases, such as Alzheimers and Parkinsons. Here we show that these aggregates possess a compact, quasi-crystalline architect ...
A few months ago, experts were talking about the next generation of "disease-modifying" drugs that were expected to help treat Alzheimers disease by attacking amyloid plaque in the brain. In fact, they were arguing that any newly written treatment guidelines were likely to be quickly outdated by the advent of new, powerful drugs. Drug companies were also optimistic, developing all kinds of "anti-amyloid" drugs that were expected to fundamentally alter the course of the disease.. "Amyloid" is the stuff that gets in the brain in Alzheimers disease. The theory is that amyloid is toxic to the brain, setting up the slow burn we know as Alzheimers disease. Based on that theory, weve assumed that drugs that prevent amyloid from developing, or that promote its removal, are drugs that would be good for treating Alzheimers.. So the scientists of the world attacked amyloid with a vengeance, generating drugs to clamp down on the enzyme that produces it, on the process that causes it to crystallize in ...
Background:. Alzheimers dementia (AD) is a common disorder of the aging brain causing progressive and irreversible impairment in memory and cognitive function. Beginning with the initial description of Alzheimers dementia (AD) in 1906 when abnormal accumulations of plaques and tangles in the brain of a woman with severe cognitive impairment were first noted, the pathophysiology of AD has been intimately associated with a progressive neuropathologic process involving abnormal protein deposition in brain. More recent work has implicated the accumulation of β-amyloid as an early feature of AD, which may be directly responsible for some of the clinical manifestations of the disease. Pathologic studies suggest levels of β-amyloid are elevated even in cases classified as having questionable dementia (CDR score = 0.5), and increases in amyloid are strongly correlated with cognitive decline. Increases in β-amyloid precede significant tau pathology suggesting the formation of plaques early in the ...
Alzheimers disease (AD) and familial Danish dementia (FDD) are degenerative neurological diseases characterized by amyloid pathology. Normal human sera contain IgG antibodies that specifically bind diverse preamyloid and amyloid proteins and have shown therapeutic potential in vitro and in vivo. We cloned one of these antibodies, 3H3, from memory B cells of a healthy individual using a hybridoma method. 3H3 is an affinity-matured IgG that binds a pan-amyloid epitope, recognizing both Aβ and λ Ig light chain (LC) amyloids, which are associated with AD and primary amyloidosis, respectively. The pan-amyloid-binding properties of 3H3 were demonstrated using ELISA, immunohistochemical studies, and competition binding assays. Functional studies showed that 3H3 inhibits both Aβ and LC amyloid formation in vitro and abrogates disruption of hippocampal synaptic plasticity by AD-patient-derived soluble Aβ in vivo. A 3H3 single-chain variable fragment (scFv) retained the binding specificity of the 3H3 IgG and
Extracellular Curli formation by bacteria together with the intralumenal formation of pMel17 Mα fibrous striations by mammalian cells demonstrate that amyloid-like fibrils can be a natural product-a quaternary protein nanostructure formed by biological systems. The fact that mammalian cells utilize a fibril structure to mediate function emphasizes that tuning of protein structure by proteolysis can be a very powerful determinant for expanding the biological diversity of polypeptides. It is apparent that E. coli and Salmonella go to great lengths to control amyloidogenesis, as evidenced by the dedication of at least two operons to harness the potential of the amyloid quaternary structure to perform a useful biological function, and to prevent misassembly elsewhere in the cell. It is almost certain that numerous mammalian genes are also used to control amyloid-like fibril formation within organelles such as the melanosome to allow to its potential to be recognized. Interestingly, the process of ...
(Phys.org)-Several fatal brain disorders, including Parkinsons disease, are connected by the misfolding of specific proteins into disordered clumps and stable, insoluble fibrils called amyloid. Amyloid fibrils are hard ...
Alzheimers disease is the leading cause of late-life dementia. An increasing body of evidence has linked assemblies of a common peptide, the amyloid protein, to the disease. While plaques formed from large assemblies of this protein are known to be the eventual result of Alzheimers, recent evidence suggests that small assemblies - or oligomers - of amyloid are the toxic agents responsible for the disease symptoms.. In this research, scientists used mass spectrometry to study the mixture of oligomers formed by the amyloid 42 protein. While many types of amyloid assemblies have been described, the researchers found that oligomers made up of 12 units of amyloid 42 appear to be a key neurotoxic agent in the development of Alzheimers.. ...
Since the beginning of the years 2000, more and more examples of functional amyloid fibers have been discovered in bacteria and fungi as well as in the mammals realm[1-2]. Very recently, a study on about forty peptide hormones has demonstrated that those were stored inside pituitary secretory granules under the form of amyloid fibers[3]. Beyond the structural biology question, we are especially interested in these molecules because we think they might be appropriate models to tackle broader issues like biomimetic self-assembly and amyloid formation - amyloid understood as
Since the beginning of the years 2000, more and more examples of functional amyloid fibers have been discovered in bacteria and fungi as well as in the mammals realm[1-2]. Very recently, a study on about forty peptide hormones has demonstrated that those were stored inside pituitary secretory granules under the form of amyloid fibers[3]. Beyond the structural biology question, we are especially interested in these molecules because we think they might be appropriate models to tackle broader issues like biomimetic self-assembly and amyloid formation - amyloid understood as
en] Amyloidogenic model peptides are invaluable for investigating assembly mechanisms in disease related amyloids and in protein folding. During aggregation, such peptides can undergo bifurcation leading to fibrils or crystals, however the mechanisms of fibril-to-crystal conversion are unclear. We navigate herein the energy landscape of amyloidogenic peptides by studying a homologous series of hexapeptides found in animal, human and disease related proteins. We observe fibril-to-crystal conversion occurring within single aggregates via untwisting of twisted ribbon fibrils possessing saddle-like curvature and cross-sectional aspect ratios approaching unity. Changing sequence, pH or concentration shifts the growth towards larger aspect ratio species assembling into stable helical ribbons possessing mean-curvature. By comparing atomistic calculations of desolvation energies for association of peptides we parameterise a kinetic model, providing a physical explanation of fibril-to-crystal ...
Aortic medial amyloid (AMA) occurs as localised non-atheromatous plaques in virtually all individuals over the age of 50. The major protein component of AMA is the 50-residue polypeptide medin. Here we propose two methods of manipulating medin aggregation to reduce the cytotoxic species of medin: either by promoting formation of larger benign species or retaining small non-cytotoxic species. Medin co-localises with a variety of factors including glycosaminoglycans (GAGs). The first approach shows that the GAG heparin enhances the rate of medin aggregation and alters the morphology of the amyloid fibrils. Cellular viability measurements suggest that heparin eliminates small cytotoxic species of medin, promoting formation of benign fibrils. The second approach applies a previously successful approach of designing small peptide moieties that are complementary to the key amyloidogenic sequence but which contain modified amino acids known to disrupt hydrogen bonding and therefore prevent aggregation ...
Filamentous amyloid aggregates are crucial for the pathology of Alzheimers disease. Despite the tremendous biomedical importance of amyloid fibrils, the molecular mechanism and the dynamic pathways involved in their formation remain elusive and challenging to investigate in experiments and simulations. We use a combination of detailed MD simulations and energy-landscape theory to overcome the challenge due to the different timescales involved in fibril growth. In the first step, we calculate the free energy profile for fibril elongation by a single monomer at the two struc-turally unequal fibril tips and for the association of larger fibril fragments. The forces driving fibril formation are investigated in a detailed enthalpy/entropy decomposition providing insight into the role of solvent entropy as the main driving force for assembly. In the second step, we calculate the local diffusion profile which gives insight into the degrees of freedom perpendicular to the distance between fibril and ...
Non-ionic Triton X-100 extracts a portion of insoluble Aβ. As with chelators, the portion of insoluble Aβ extracted by non-deterents is dependent on age/stage of mice. For early stage of β-amyloid deposition (i.e. mice ,12 months) up to 80% of total mouse brain Aβ is extracted by Triton X-100. Proportion drops rapidly 20% or less in old animals (i.e. mice , 18 months) with heavy mature β-amyloid deposition. Biolegends Aβ ELISAs (and most other ELISAs) are compatible with non-ionic detergents ...
2Institute for Medical Physics and Biophysics, University Leipzig, Germany. Amyloids are well ordered protein aggregates involved in many functional and pathogenic processes of life. Various structural models of the molecular architecture of amyloids have been derived in the last decade mainly driven by advances in solid state NMR. This talk will summarize our NMR efforts to study not only structural features of mature fibrils but the amyloid formation mechanism. Two systems will be covered: the Alzheimer peptide Aβ(1-40) and variants as well as the human parathyroid hormone PTH(1-84). For Aβ(1-40) we show that backbone hydrogen bonds are the main driving force for fibril structure formation overwriting side chain effect and buffer conditions [1,2]. Additionally, we show that morphological properties of fibril seeds do not necessarily propagate towards the growing fibril [3]. Several molecular observations during the formation of PTH(1-84) fibrils will be presented [4] to classify them as ...
2Institute for Medical Physics and Biophysics, University Leipzig, Germany. Amyloids are well ordered protein aggregates involved in many functional and pathogenic processes of life. Various structural models of the molecular architecture of amyloids have been derived in the last decade mainly driven by advances in solid state NMR. This talk will summarize our NMR efforts to study not only structural features of mature fibrils but the amyloid formation mechanism. Two systems will be covered: the Alzheimer peptide Aβ(1-40) and variants as well as the human parathyroid hormone PTH(1-84). For Aβ(1-40) we show that backbone hydrogen bonds are the main driving force for fibril structure formation overwriting side chain effect and buffer conditions [1,2]. Additionally, we show that morphological properties of fibril seeds do not necessarily propagate towards the growing fibril [3]. Several molecular observations during the formation of PTH(1-84) fibrils will be presented [4] to classify them as ...
This report represents the initial findings from what is designed to be a longitudinal study to delineate the natural history of amyloid deposition in eoFAD. To our knowledge, this is the first report of amyloid imaging in asymptomatic carriers of PS1 mutations, some of whom are more than 10 years younger than the age at which onset of cognitive symptoms would be expected (e.g., 48 years for the PS1C410Y mutation carriers). The findings suggest that amyloid deposition in these two families begins in the striatum well before the onset of cognitive symptoms.. Previous studies using structural MRI and [18F]fluorodeoxyglucose (FDG) PET determination of cerebral metabolic rate for glucose have shown changes in presymptomatic and symptomatic eoFAD subjects. Fox and colleagues (Schott et al., 2003; Ridha et al., 2006) reported that changes in hippocampal atrophy rate were evident 5.5 years before a diagnosis of AD. Two early reports showed decreased cerebral metabolism by FDG-PET in symptomatic eoFAD ...
The growth of amyloid fibrils requires a disordered or partially unfolded protein to bind to the fibril and adapt the same conformation and alignment established by the fibril template. Since the H-bonds stabilizing the fibril are interchangeable, it is inevitable that H-bonds form between incorrect pairs of amino acids which are either incorporated into the fibril as defects or must be broken before the correct alignment can be found. This process is modeled by mapping the formation and breakage of H-bonds to a one-dimensional random walk. The resulting microscopic model of fibril growth is governed by two timescales: the diffusion time of the monomeric proteins, and the time required for incorrectly bound proteins to unbind from the fibril. The theory predicts that the Arrhenius behavior observed in experiments is due to off-pathway states rather than an on-pathway transition state. The predicted growth rates are in qualitative agreement with experiments on insulin fibril growth rates as a ...
The cholesteryl-ester transfer protein (CETP) facilitates the transfer of cholesterol esters and triglycerides between lipoproteins in plasma where the critical site for its function is situated in the C-terminal domain. Our group has previously shown that this domain presents conformational changes in a non-lipid environment when the mutation D470N is introduced. Using a series of peptides derived from this C-terminal domain, the present study shows that these changes favor the induction of a secondary β-structure as characterized by spectroscopic analysis and fluorescence techniques. From this type of secondary structure, the formation of peptide aggregates and fibrillar structures with amyloid characteristics induced cytotoxicity in microglial cells in culture. These supramolecular structures promote cell cytotoxicity through the formation of reactive oxygen species (ROS) and change the balance of a series of proteins that control the process of endocytosis, similar to that observed when β-amyloid
α2-Macroglobulin (α2M) is an extracellular chaperone that inhibits amorphous and fibrillar protein aggregation. The reaction of α2M with proteases results in an activated conformation, where the proteases become covalently-linked within the interior of a cage-like structure formed by α2M. This study investigates, the effect of activation on the ability of α2M to inhibit amyloid formation by Aβ1-42 and I59T human lysozyme and shows that protease-activated α2M can act via two distinct mechanisms: (i) by trapping proteases that remain able to degrade polypeptide chains and (ii) by a chaperone action that prevents misfolded clients from continuing along the amyloid forming pathway.
After dealing with disease or defect for a long period of time, the body may start to produce abnormally folded protein deposits. This process is referred to as amyloidosis, and the deposits themselves have been termed
Amyloidosis is a condition in which a waxy translucent substance - consisting primarily of protein - deposits in a cats organs and tissues. Prolonged excess of this condition may lead to organ failure.
TY - JOUR. T1 - Fibrillogenesis of huntingtin and other glutamine containing proteins. AU - Lyubchenko, Yuri L.. AU - Krasnoslobodtsev, Alexey V.. AU - Luca, Sorin. PY - 2012. Y1 - 2012. N2 - This chapter focuses on the aggregation of glutamine containing peptides and proteins with an emphasis on huntingtin protein, whose aggregation leads to the development of Huntingtons disease. The kinetics that leads to the formation of amyloids, the structure of aggregates of various types and the morphological mechanical properties of amyloid fibrils are described. The kinetics of amyloid fibril formation has been proposed to follow a nucleation dependent polymerization model, dependent upon the size of the nucleus. This model and the effect of the polyglutamine length on the nucleus size are reviewed. Aggregate structure is characterized at two different levels. The atomic-scale resolution structure of fibrillar and crystalline aggregates of polyglutamine containing proteins and peptides was determined ...
The aggregation of peptides and proteins into highly organized aggregates such as amyloid fibrils is a very important and fundamental process in biology. Most p...
Misfolding of proteins and peptides is closely linked to several neurodegenerative disorders, among them Alzheimers disease (AD), the most prominent example of brain diseases. The self-assembly of the amyloid β peptide (Aβ) into amyloid fibrils is one histologic hallmark of AD. A detailed knowledge about the underlying mechanism(s) of Aβ aggregation is crucial for advances toward a fundamental understanding of the disease, which may promote the search for and design of efficient therapeutics. The work presented in this thesis deals with modulation of the aggregation process by various compounds, i.e. small organic molecules (e.g. lacmoid and Congo red), surfactants and metal ions. These results provide insight into the molecular mechanism of modulator interactions and interference with Aβ and its aggregation pathways. Applying a combination of kinetic and dynamic studies as well as structural investigations we characterized the molecular interactions between Aβ and aggregation modulators ...