scholarly journals The growth of amyloid fibrils: rates and mechanisms

2019 ◽  
Vol 476 (19) ◽  
pp. 2677-2703 ◽  
Author(s):  
Alexander K. Buell
Keyword(s):  
Amyloid Fibrils ◽  
Amyloid Fibril ◽  
Experimental Studies ◽  
Amyloid Protein ◽  
Protein Polymers ◽  
Human Disorders ◽  
Functional Context ◽  
Basic Ideas ◽  
Β Sheet

Abstract Amyloid fibrils are β-sheet-rich linear protein polymers that can be formed by a large variety of different proteins. These assemblies have received much interest in recent decades, due to their role in a range of human disorders. However, amyloid fibrils are also found in a functional context, whereby their structural, mechanical and thermodynamic properties are exploited by biological systems. Amyloid fibrils form through a nucleated polymerisation mechanism with secondary processes acting in many cases to amplify the number of fibrils. The filamentous nature of amyloid fibrils implies that the fibril growth rate is, by several orders of magnitude, the fastest step of the overall aggregation reaction. This article focusses specifically on in vitro experimental studies of the process of amyloid fibril growth, or elongation, and summarises the state of knowledge of its kinetics and mechanisms. This work attempts to provide the most comprehensive summary, to date, of the available experimental data on amyloid fibril elongation rate constants and the temperature and concentration dependence of amyloid fibril elongation rates. These data are compared with those from other types of protein polymers. This comparison with data from other polymerising proteins is interesting and relevant because many of the basic ideas and concepts discussed here were first introduced for non-amyloid protein polymers, most notably by the Japanese school of Oosawa and co-workers for cytoskeletal filaments.

scholarly journals Cofactors are essential constituents of stable and seeding-active tau fibrils

2018 ◽  
Vol 115 (52) ◽  
pp. 13234-13239 ◽  
Author(s):  
Yann Fichou ◽  
Yanxian Lin ◽  
Jennifer N. Rauch ◽  
Michael Vigers ◽  
Zhikai Zeng ◽  
...  
Keyword(s):  
Room Temperature ◽  
Amyloid Fibrils ◽  
Amyloid Fibril ◽  
Future Studies ◽  
Biophysical Studies ◽  
Stable Forms ◽  
Β Sheet ◽  
Tau Fibrils

Amyloid fibrils are cross-β–rich aggregates that are exceptionally stable forms of protein assembly. Accumulation of tau amyloid fibrils is involved in many neurodegenerative diseases, including Alzheimer’s disease (AD). Heparin-induced aggregates have been widely used and assumed to be a good tau amyloid fibril model for most biophysical studies. Here we show that mature fibrils made of 4R tau variants, prepared with heparin or RNA, spontaneously depolymerize and release monomers when their cofactors are removed. We demonstrate that the cross-β-sheet assembly formed in vitro with polyanion addition is unstable at room temperature. We furthermore demonstrate high seeding capacity with transgenic AD mouse brain-extracted tau fibrils in vitro that, however, is exhausted after one generation, while supplementation with RNA cofactors resulted in sustained seeding over multiple generations. We suggest that tau fibrils formed in brains are supported by unknown cofactors and inhere higher-quality packing, as reflected in a more distinct conformational arrangement in the mouse fibril-seeded, compared with heparin-induced, tau fibrils. Our study suggests that the role of cofactors in tauopathies is a worthy focus of future studies, as they may be viable targets for diagnosis and therapeutics.

scholarly journals Pancreatic beta-cell granule peptides form heteromolecular complexes which inhibit islet amyloid polypeptide fibril formation

2004 ◽  
Vol 377 (3) ◽  
pp. 709-716 ◽  
Author(s):  
Emma T. A. S. JAIKARAN ◽  
Melanie R. NILSSON ◽  
Anne CLARK
Keyword(s):  
Type 2 Diabetes ◽  
Amyloid Fibrils ◽  
Secretory Granules ◽  
Pancreatic Beta Cell ◽  
Islet Amyloid Polypeptide ◽  
Fibril Formation ◽  
Islet Amyloid ◽  
Β Sheet

Islet amyloid polypeptide (IAPP), or ‘amylin’, is co-stored with insulin in secretory granules of pancreatic islet β-cells. In Type 2 diabetes, IAPP converts into a β-sheet conformation and oligomerizes to form amyloid fibrils and islet deposits. Granule components, including insulin, inhibit spontaneous IAPP fibril formation in vitro. To determine the mechanism of this inhibition, molecular interactions of insulin with human IAPP (hIAPP), rat IAPP (rIAPP) and other peptides were examined using surface plasmon resonance (BIAcore), CD and transmission electron microscopy (EM). hIAPP and rIAPP complexed with insulin, and this reaction was concentration-dependent. rIAPP and insulin, but not pro-insulin, bound to hIAPP. Insulin with a truncated B-chain, to prevent dimerization, also bound hIAPP. In the presence of insulin, hIAPP did not spontaneously develop β-sheet secondary structure or form fibrils. Insulin interacted with pre-formed IAPP fibrils in a regular repeating pattern, as demonstrated by immunoEM, suggesting that the binding sites for insulin remain exposed in hIAPP fibrils. Since rIAPP and hIAPP form complexes with insulin (and each other), this could explain the lack of amyloid fibrils in transgenic mice expressing hIAPP. It is likely that IAPP fibrillogenesis is inhibited in secretory granules (where the hIAPP concentration is in the millimolar range) by heteromolecular complex formation with insulin. Alterations in the proportions of insulin and IAPP in granules could disrupt the stability of the peptide. The increase in the proportion of unprocessed pro-insulin produced in Type 2 diabetes could be a major factor in destabilization of hIAPP and induction of fibril formation.

scholarly journals Parkinson’s disease is a type of amyloidosis featuring accumulation of amyloid fibrils of α-synuclein

2019 ◽  
Vol 116 (36) ◽  
pp. 17963-17969 ◽  
Author(s):  
Katsuya Araki ◽  
Naoto Yagi ◽  
Koki Aoyama ◽  
Chi-Jing Choong ◽  
Hideki Hayakawa ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Amyloid Fibrils ◽  
Lewy Bodies ◽  
X Ray Diffraction ◽  
Thin Sections ◽  
X Ray ◽  
Β Sheet ◽  
The Brain

Many neurodegenerative diseases are characterized by the accumulation of abnormal protein aggregates in the brain. In Parkinson’s disease (PD), α-synuclein (α-syn) forms such aggregates called Lewy bodies (LBs). Recently, it has been reported that aggregates of α-syn with a cross-β structure are capable of propagating within the brain in a prionlike manner. However, the presence of cross-β sheet-rich aggregates in LBs has not been experimentally demonstrated so far. Here, we examined LBs in thin sections of autopsy brains of patients with PD using microbeam X-ray diffraction (XRD) and found that some of them gave a diffraction pattern typical of a cross-β structure. This result confirms that LBs in the brain of PD patients contain amyloid fibrils with a cross-β structure and supports the validity of in vitro propagation experiments using artificially formed amyloid fibrils of α-syn. Notably, our finding supports the concept that PD is a type of amyloidosis, a disease featuring the accumulation of amyloid fibrils of α-syn.

scholarly journals Gold nanocolloid–protein interactions and their impact on β-sheet amyloid fibril formation

RSC Advances ◽  
2018 ◽  
Vol 8 (2) ◽  
pp. 980-986 ◽  
Author(s):  
Heloise R. Barros ◽  
Maria Kokkinopoulou ◽  
Izabel C. Riegel-Vidotti ◽  
Katharina Landfester ◽  
Héloïse Thérien-Aubin
Keyword(s):  
Protein Interactions ◽  
Amyloid Fibril ◽  
Interaction Mechanism ◽  
Fibril Formation ◽  
Amyloid Protein ◽  
Degenerative Diseases ◽  
Amyloid Fibril Formation ◽  
Protein Fibrils ◽  
Β Sheet

Formation of amyloid protein fibrils is associated with degenerative diseases. Here, the interaction mechanism between globular and fibrillar proteins with AuNPs were investigated in order to potentially control and reverse the fibrillation process.

scholarly journals Fluorescence Phenomena in Amyloid and Amyloidogenic Bionanostructures

Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 668 ◽  
Author(s):  
B. Apter ◽  
N. Lapshina ◽  
H. Barhom ◽  
B. Fainberg ◽  
A. Handelman ◽  
...  
Keyword(s):  
Amyloid Fibrils ◽  
Fluorescent Protein ◽  
Fluorescent Proteins ◽  
Protein Structures ◽  
Visible Spectrum ◽  
Biological Tissues ◽  
New Generation ◽  
Β Sheet

Nanoscale optical labeling is an advanced bioimaging tool. It is mostly based on fluorescence (FL) phenomena and enables the visualization of single biocells, bacteria, viruses, and biological tissues, providing monitoring of functional biosystems in vitro and in vivo, and the imaging-guided transportation of drug molecules. There is a variety of FL biolabels such as organic molecular dyes, genetically encoded fluorescent proteins (green fluorescent protein and homologs), semiconductor quantum dots, carbon dots, plasmonic metal gold-based nanostructures and more. In this review, a new generation of FL biolabels based on the recently found biophotonic effects of visible FL are described. This intrinsic FL phenomenon is observed in any peptide/protein materials folded into β-sheet secondary structures, irrespective of their composition, complexity, and origin. The FL effect has been observed both in natural amyloid fibrils, associated with neurodegenerative diseases (Alzheimer’s, Parkinson’s, and more), and diverse synthetic peptide/protein structures subjected to thermally induced biological refolding helix-like→β-sheet. This approach allowed us to develop a new generation of FL peptide/protein bionanodots radiating multicolor, tunable, visible FL, covering the entire visible spectrum in the range of 400–700 nm. Newly developed biocompatible nanoscale biomarkers are considered as a promising tool for emerging precise biomedicine and advanced medical nanotechnologies (high-resolution bioimaging, light diagnostics, therapy, optogenetics, and health monitoring).

scholarly journals Accumulation of pro-apolipoprotein A-II in mouse senile amyloid fibrils

1997 ◽  
Vol 325 (3) ◽  
pp. 653-659 ◽  
Author(s):  
Keiichi HIGUCHI ◽  
Kumiko KOGISHI ◽  
Jing WANG ◽  
Chen XIA ◽  
Takuya CHIBA ◽  
...  
Keyword(s):  
Amino Acid ◽  
High Density Lipoprotein ◽  
Relative Abundance ◽  
Mouse Liver ◽  
Amyloid Fibrils ◽  
Amyloid Fibril ◽  
Density Lipoprotein ◽  
Amyloid Protein ◽  
Amino Acid Residues ◽  
Apolipoprotein A

Apolipoprotein A-II (apoA-II), the major apoprotein of serum high-density lipoprotein, is deposited as amyloid fibrils (AApoAII) in murine senile amyloidosis. We have identified and purified a more basic amyloid protein from old-mouse liver. N-terminal sequencing of the protein revealed that the pro-segment of five amino acid residues (Ala-Leu-Val-Lys-Arg) extended from the N-terminal glutamine residue of mature apoA-II protein. MS analysis revealed the deposit of intact pro-apoA-II protein (molecular mass 9319 Da). Antiserum was prepared for staining of the AApoAII amyloid deposition. The relative abundance of pro-apoA-II to mature apoA-II in the amyloid-fibril fraction isolated from livers of mice with severe amyloidosis was 14.1%. The similar abundance of pro-apoA-II in the amyloid fibril fraction from the spleen (16.3%) suggested that deposited pro-apoA-II originated from the blood. The concentration of pro-apoA-II was much lower in the serum (1.5% of mature apoA-II) than in the amyloid-fibril fraction. There was no difference in the content of pro-apoA-II between the amyloidogenetic R1.P1-Apoa2c and amyloid-resistant SAMR1 strains at the age of 3 months. The abundance of pro-apoA-II in the amyloid-fibril fraction compared with the serum suggested that it plays a key role in the initialization of mouse senile amyloidosis.

scholarly journals MURINE AMYLOID FIBRIL PROTEIN: ISOLATION, PURIFICATION AND CHARACTERIZATION

1971 ◽  
Vol 19 (1) ◽  
pp. 16-28 ◽  
Author(s):  
G. G. GLENNER ◽  
D. PAGE ◽  
C. ISERSKY ◽  
M. HARADA ◽  
P. CUATRECASAS ◽  
...  
Keyword(s):  
Amyloid Fibrils ◽  
Amyloid Fibril ◽  
Sodium Dodecyl ◽  
Gel Filtration ◽  
Disc Electrophoresis ◽  
Structure Identification ◽  
Major Protein ◽  
Amyloid Protein ◽  
Molecular Weights ◽  
Sepharose 4B

Murine amyloid has been produced by four different induction methods ( Mycobacterium butyricum, casein, casein plus Freund's adjuvant and endotoxin-induced mouse amyloidosis) in several strains and obtained from mice with "spontaneous" amyloidosis. The amyloid fibrils have been concentrated from spleen and liver. Electron microscopy of all of these preparations reveals the amyloid fibril to be 100 Å in width and composed of two parallel filaments, each measuring 35-40 Å in width and having the appearance of a twisted ribbon. X-ray diffraction of all preparations reveals a "backbone" spacing at 4.75 Å and a "side chain" spacing at 11 Å indicating a "β-pleated sheet" structure. Identification of the major protein component of amyloid fibril concentrates was made by combined use of sodium dodecyl sulfate polyacrylamide disc electrophoresis, labeling of the protein with 3H-tryptophan and Sepharose 4B gel filtration. Purification of the amyloid protein from spontaneous amyloidosis liver was accomplished by sequential gel filtration with 5 M guanidine in 1 N acetic acid on Sepharose 4B and Sephadex G-100 or G-75 columns. The material is a unique glycoprotein with a molecular weight of 7200, a high content of dicarboxylic and short chain amino acids, a significant amount of tryptophan and an unreactive NH2-terminal amino acid, tentatively identified as pyrrolid-2-one-5-carboxylic acid. There are no methionine, half-cystine, hydroxylysine or hydroxyproline residues. Murine amyloid protein, therefore, has striking similarities to many human amyloid protein preparations. It differs from the human proteins in the similarity of molecular weights of different preparations.

Protein aggregation: more than just fibrils

2009 ◽  
Vol 37 (4) ◽  
pp. 682-686 ◽  
Author(s):  
Mark R.H. Krebs ◽  
Kristin R. Domike ◽  
Athene M. Donald
Keyword(s):  
Isoelectric Point ◽  
Amyloid Fibrils ◽  
Central Nucleus ◽  
Net Charge ◽  
Protein Size ◽  
Maltese Cross ◽  
Different Types ◽  
Β Sheet

The aggregation of misfolded proteins into amyloid fibrils, and the importance of this step for various diseases, is well known. However, it is becoming apparent that the fibril is not the only structure that aggregating proteins of widely different types may adopt. Around the isoelectric point, when the net charge is essentially zero, rather monodisperse and quasi-amorphous nanoscale particles form. These particles are found to contain limited runs of β-sheet structure, but their overall organization is random. These nanoparticles have the potential to be useful for such applications as the slow release of drugs. The amyloid fibrils form away from the isoelectric point, but over certain ranges of, e.g., pH, the fibrils themselves do not exist freely, but form suprafibrillar aggregates termed spherulites. These consist of fibrils radiating from a central nucleus, and form by new species attaching to the ends of growing fibrils, rather than by the aggregation of pre-existing fibrils. Under the polarizing light microscope, they exhibit a Maltese cross shape due to their symmetry. The rate of aggregation is determined by factors involving (at least) protein size, concentration, presence of salt and charge. The occurrence of spherulites, which have been found in vivo as well as in vitro, appears to be generic, although the factors which determine the equilibrium between free fibril and spherulite are not as yet clear.

scholarly journals Recent Insights into the Pathogenesis of Type AA Amyloidosis

2011 ◽  
Vol 11 ◽  
pp. 641-650 ◽  
Author(s):  
J. C. H. van der Hilst
Keyword(s):  
Amino Acids ◽  
Amyloid Fibrils ◽  
Rare Event ◽  
Helical Structure ◽  
Amyloid A ◽  
Acid Protein ◽  
Life Threatening ◽  
Shock Proteins ◽  
Β Sheet

The amyloidoses are a group of life-threatening diseases in which fibrils made of misfolded proteins are deposited in organs and tissues. The fibrils are stable, insoluble aggregates of precursor proteins that have adopted an antiparallel β-sheet structure. In type AA, or reactive, amyloidosis, the precursor protein of the fibrils is serum amyloid A (SAA). SAA is a 104-amino-acid protein that is produced in the liver in response to proinflammatory cytokines. Although the protein that is produced by the liver contains 104 amino acids, only the N-terminal 66–76 amino acids are found in amyloid fibrils. Furthermore, SAA has been shown to have an α-helical structure primarily. Thus, for SAA to be incorporated into an amyloid fibril, two processes have to occur: C-terminal cleavage and conversion into a β-sheet. Only a minority of patients with elevated SAA levels develop amyloidosis. Factors that contribute to the risk of amyloidosis include the duration and degree of SAA elevation, polymorphisms in SAA, and the type of autoinflammatory syndrome. In the Hyper-IgD syndrome, amyloidosis is less prevalent than in the other autoinflammatory diseases.In vitrowork has shown that the isoprenoid pathway influences amyloidogenesis by farnesylated proteins. Although many proteins contain domains that have a potential for self-aggregation, amyloidosis is only a very rare event. Heat shock proteins (HSPs) are chaperones that assist other proteins to attain, maintain, and regain a functional conformation. In this review, recent insights into the pathogenesis of amyloidosis are discussed, in addition to a new hypothesis for a role of HSPs in the pathogenesis of type AA.

scholarly journals Secondary Nucleation and the Conservation of Structural Characteristics of Amyloid Fibril Strains

2021 ◽  
Vol 8 ◽  
Author(s):  
Saeid Hadi Alijanvand ◽  
Alessia Peduzzo ◽  
Alexander K. Buell
Keyword(s):  
Amyloid Fibrils ◽  
Amyloid Fibril ◽  
Structural Characteristics ◽  
Secondary Nucleation ◽  
Primary Nucleation ◽  
Structural Preferences ◽  
Initial Seed ◽  
The Brain

Amyloid fibrils are ordered protein aggregates and a hallmark of many severe neurodegenerative diseases. Amyloid fibrils form through primary nucleation from monomeric protein, grow through monomer addition and proliferate through fragmentation or through the nucleation of new fibrils on the surface of existing fibrils (secondary nucleation). It is currently still unclear how amyloid fibrils initially form in the brain of affected individuals and how they are amplified. A given amyloid protein can sometimes form fibrils of different structure under different solution conditions in vitro, but often fibrils found in patients are highly homogeneous. These findings suggest that the processes that amplify amyloid fibrils in vivo can in some cases preserve the structural characteristics of the initial seed fibrils. It has been known for many years that fibril growth by monomer addition maintains the structure of the seed fibril, as the latter acts as a template that imposes its fold on the newly added monomer. However, for fibrils that are formed through secondary nucleation it was, until recently, not clear whether the structure of the seed fibril is preserved. Here we review the experimental evidence on this question that has emerged over the last years. The overall picture is that the fibril strain that forms through secondary nucleation is mostly defined by the solution conditions and intrinsic structural preferences, and not by the seed fibril strain.

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