Monitoring the assembly of Ig light-chain amyloid fibrils by atomic force microscopy

Ionescu-Zanetti, Cristian; Khurana, Rohit; Gillespie, Joel R.; Petrick, Jay S.; Trabachino, Lynne C.; Minert, Lauren J.; Carter, Sue A.; Fink, Anthony L.

doi:10.1073/pnas.96.23.13175

Cited by 201 publications

(154 citation statements)

References 23 publications

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“…Studies using Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) spectroscopy indicate that the initial aggregates retain their predominantly helical structure, but that there is a subsequent conversion to ␤-sheet structure as well organized fibrils become visible in negative stain EM images (14). EM and atomic force microscopy studies of other amyloid proteins have indicated similar assembly pathways (25)(26)(27)(28).…”

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confidence: 99%

The protofilament structure of insulin amyloid fibrils

Jiménez

Nettleton

Bouchard

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

779

822

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Under solution conditions where the native state is destabilized, the largely helical polypeptide hormone insulin readily aggregates to form amyloid fibrils with a characteristic cross-␤ structure. However, there is a lack of information relating the 4.8 Å ␤-strand repeat to the higher order assembly of amyloid fibrils. We have used cryo-electron microscopy (EM), combining single particle analysis and helical reconstruction, to characterize these fibrils and to study the three-dimensional (3D) arrangement of their component protofilaments. Low-resolution 3D structures of fibrils containing 2, 4, and 6 protofilaments reveal a characteristic, compact shape of the insulin protofilament. Considerations of protofilament packing indicate that the cross-␤ ribbon is composed of relatively flat ␤-sheets rather than being the highly twisted, ␤-coil structure previously suggested by analysis of globular protein folds. Comparison of the various fibril structures suggests that very small, local changes in ␤-sheet twist are important in establishing the long-range coiling of the protofilaments into fibrils of diverse morphology.U nder conditions that destabilize the native state, proteins can self-aggregate into insoluble, fibrillar assemblies (1-3). In the form of amyloid fibrils or fibril precursors, the proteins not only lack their original biological function but also may be harmful to organisms, causing pathologies such as Alzheimer's and prion diseases. Although amyloid precursor proteins do not share any sequence or structural homology, amyloid fibrils are typically unbranched, protease-resistant filaments approximately 100 Å in diameter and composed of Ϸ20-35 Å wide protofilaments, which are sometimes arranged around an electron lucent core (4, 5). Recently, several nonpathological proteins and short peptides have been shown to self-assemble into amyloid-like fibrils (6-9), leading to the suggestion that amyloid formation is a generic property of polypeptide chains (3, 10).The overall morphology of amyloid aggregates depends on the conditions in which fibrillogenesis takes place, and different fibril morphologies are often observed in the same preparation (7,(11)(12)(13)(14). Variable structures also are seen in ex vivo fibrils extracted from amyloidotic tissue (4, 15). The morphological variation seems to be caused by fibrils with a variable number and arrangement of protofilaments. X-ray fiber diffraction studies reveal a characteristic cross-␤ structure with ␤-strands of the precursor protein arranged perpendicular to, and ribbon-like ␤-sheets parallel to, the fibril axis (2, 16, 17). The ␤-strand repeat has also been directly visualized by cryo-EM (8). However, there is a lack of three-dimensional (3D) structural information on how the 4.8 Å ␤-strand repeat relates to the overall fibril assembly.The polypeptide hormone insulin has a mainly helical native structure, with its two polypeptide chains linked by two interchain and one intra-chain disulfide bonds (18). In vitro, insulin is readily converted to an inactiv...

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mentioning

confidence: 99%

The protofilament structure of insulin amyloid fibrils

Jiménez

Nettleton

Bouchard

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

779

822

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“…by optical experiments [10][11][12][13][14], obtaining kinetic plots with a characteristic sigmoidal shape [15][16][17] . An important quantity, called the lag time t lag 18,19 , can then be extracted; it is defined as the waiting time before a sharp increase of fibril mass appears in the sigmoidal plot.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms and rates of nucleation of amyloid fibrils

Lee

Terentjev

2017

The Journal of Chemical Physics

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The classical nucleation theory finds the rate of nucleation proportional to the monomer concentration raised to the power, which is the 'critical nucleaus size', n c . The implicit assumption, that amyloids nucleate in the same way, has been recently challenged by an alternative two-step mechanism, when the soluble monomers first form a metastable aggregate (micelle), and then undergo conversion into the conformation rich in β-strands that are able to form a stable growing nucleus for the protofilament. Here we put together the elements of extensive knowledge about aggregation and nucleation kinetics, using a specific case of Aβ 1−42 amyloidogenic peptide for illustration, to find theoretical expressions for the effective rate of amyloid nucleation. We find that at low monomer concentration in solution, and also at low interaction energy between two peptide conformations in the micelle, the nucleation occurs via the classical route. At higher monomer concentration, and a range of other interaction parameters between peptides, the two-step 'aggregation-conversion' mechanism of nucleation takes over. In this regime, the effective rate of the process can be interpreted as a power of monomer concentration in a certain range of parameters, however, the exponent is determined by a complicated interplay of interaction parameters and is not related to the minimum size of the growing nucleus (which we find to be ∼ 7-8 for Aβ 1−42 ).

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“…Nascent protofilaments can nucleate and elongate through the addition of partially folded oligomeric intermediates to the ends of the growing protofilaments. Protofilaments can further intertwine to form protofibrils and fibrils (4,5). Glycosaminoglycans (GAGs) are one of the major components of the extracellular matrix.…”

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confidence: 99%

Role of Glycosaminoglycan Sulfation in the Formation of Immunoglobulin Light Chain Amyloid Oligomers and Fibrils

Ren

Hong

Gong³

et al. 2010

Journal of Biological Chemistry

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Primary amyloidosis (AL) results from overproduction of unstable monoclonal immunoglobulin light chains (LCs) and the deposition of insoluble fibrils in tissues, leading to fatal organ disease. Glycosaminoglycans (GAGs) are associated with AL fibrils and have been successfully targeted in the treatment of other forms of amyloidosis. We investigated the role of GAGs in LC fibrillogenesis. Ex vivo tissue amyloid fibrils were extracted and examined for structure and associated GAGs. The GAGs were detected along the length of the fibril strand, and the periodicity of heparan sulfate (HS) along the LC fibrils generated in vitro was similar to that of the ex vivo fibrils. To examine the role of sulfated GAGs on AL oligomer and fibril formation in vitro, a 1 LC purified from urine of a patient with AL amyloidosis was incubated in the presence or absence of GAGs. The fibrils generated in vitro at physiologic concentration, temperature, and pH shared morphologic characteristics with the ex vivo 1 amyloid fibrils. The presence of HS and over-O-sulfatedheparin enhanced the formation of oligomers and fibrils with HS promoting the most rapid transition. In contrast, GAGs did not enhance fibril formation of a non-amyloidogenic 1 LC purified from urine of a patient with multiple myeloma. The data indicate that the characteristics of the full-length 1 amyloidogenic LC, containing post-translational modifications, possess key elements that influence interactions of the LC with HS. These findings highlight the importance of the variable and constant LC regions in GAG interaction and suggest potential therapeutic targets for treatment.Amyloid deposition is hypothesized to play a role in many diseases including rheumatoid arthritis and diabetes, as well as the amyloidoses themselves (1). The amyloidoses are a group of systemic and localized diseases that exhibit deposition of insoluble fibrillar proteins in organs and tissues. Primary amyloidosis (AL) 2 is the most common systemic form in the UnitedStates. It results from a plasma cell dyscrasia in which clonal B cells produce an excess of amyloidogenic immunoglobulin light chains (LCs), which circulate and deposit as insoluble fibrils throughout the body (2). A structural rearrangement from nonfibril-prone oligomers to more fibril-prone conformers is required for protofilament formation (3). Nascent protofilaments can nucleate and elongate through the addition of partially folded oligomeric intermediates to the ends of the growing protofilaments. Protofilaments can further intertwine to form protofibrils and fibrils (4, 5). Glycosaminoglycans (GAGs) are one of the major components of the extracellular matrix. They consist of disaccharide repeating units that are unbranched and attached to a serine residue of a core protein through a trisaccharide linker. Each GAG has a unique sequence, and post-assembly modifications, which can be induced by a number of factors, lead to alterations in sulfation, acetylation, or length of chain (6). Recently, Staples et al. (7) showed that the fu...

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Monitoring the assembly of Ig light-chain amyloid fibrils by atomic force microscopy

Cited by 201 publications

References 23 publications

The protofilament structure of insulin amyloid fibrils

The protofilament structure of insulin amyloid fibrils

Mechanisms and rates of nucleation of amyloid fibrils

Role of Glycosaminoglycan Sulfation in the Formation of Immunoglobulin Light Chain Amyloid Oligomers and Fibrils

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