Polymorphic Fibrillar Assembly of Human Amylin

Goldsbury, Claire; Cooper, Garth J. S.; Goldie, Kenneth N.; Müller, Shirley A.; Saafi, Etuate L.; Gruijters, W. T. M.; Misur, Martin P.; Engel, Andréas; Aebi, Ueli; Kistler, Joerg

doi:10.1006/jsbi.1997.3858

Cited by 287 publications

(325 citation statements)

References 24 publications

Supporting

Mentioning

291

Contrasting

Unclassified

Order By: Relevance

“…That propensity is concentration dependent, suggesting that higher amylin concentrations in Type II diabetes patients can lead to aggregation of the protein. 5 Note that amylin aggregates are commonly found as amyloid deposits in pancreatic islets from diabetic patients. 6 While the causative relationship between aggregation of human amylin peptide and Type II diabetes is not known, it has been established that aggregates of human amylin can induce apoptopic cell-death of the insulin producing β-cells.…”

Section: Introductionmentioning

confidence: 99%

α-helix to β-hairpin transition of human amylin monomer

Singh

Chiu

Reddy

et al. 2013

The Journal of Chemical Physics

View full text Add to dashboard Cite

The human islet amylin polypeptide is produced along with insulin by pancreatic islets. Under some circumstances, amylin can aggregate to form amyloid fibrils, whose presence in pancreatic cells is a common pathological feature of Type II diabetes. A growing body of evidence indicates that small, early stage aggregates of amylin are cytotoxic. A better understanding of the early stages of the amylin aggregation process and, in particular, of the nucleation events leading to fibril growth could help identify therapeutic strategies. Recent studies have shown that, in dilute solution, human amylin can adopt an α-helical conformation, a β-hairpin conformation, or an unstructured coil conformation. While such states have comparable free energies, the β-hairpin state exhibits a large propensity towards aggregation. In this work, we present a detailed computational analysis of the folding pathways that arise between the various conformational states of human amylin in water. A free energy surface for amylin in explicit water is first constructed by resorting to advanced sampling techniques. Extensive transition path sampling simulations are then employed to identify the preferred folding mechanisms between distinct minima on that surface. Our results reveal that the α-helical conformer of amylin undergoes a transformation into the β-hairpin monomer through one of two mechanisms. In the first, misfolding begins through formation of specific contacts near the turn region, and proceeds via a zipping mechanism. In the second, misfolding occurs through an unstructured coil intermediate. The transition states for these processes are identified. Taken together, the findings presented in this work suggest that the inter-conversion of amylin between an α-helix and a β-hairpin is an activated process and could constitute the nucleation event for fibril growth.

show abstract

Section: Introductionmentioning

confidence: 99%

α-helix to β-hairpin transition of human amylin monomer

Singh

Chiu

Reddy

et al. 2013

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…From the standpoint of molecular structure, the defining feature of an amyloid fibril is the presence of cross-β supramolecular structure, meaning that the β-sheets within the fibril are formed by β-strand segments that run approximately perpendicular to the long axis of the fibril and are linked by hydrogen bonds that run approximately parallel to this axis (11)(12)(13). Although determination of the molecular structures of amyloid fibrils is made difficult by their inherent noncrystallinity and insolubility, techniques such as solid state nuclear magnetic resonance (NMR) (12,(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33), electron paramagnetic resonance (EPR) (34-36), electron microscopy (37-43), hydrogen/deuterium exchange (29,(44)(45)(46)(47), scanning mutagenesis (48), chemical crosslinking (27,49,50), and x-ray diffraction of amyloid-like crystals (51,52) have recently shed substantial light on these structures.In vitro, amylin readily forms amyloid fibrils with a variety of morphologies as seen in transmission electron microscope (TEM) and atomic force microscope (AFM) images (40,41), and with typical cross-β diffraction patterns (53). Early solid state NMR studies by Griffiths et al focused on fibrils formed by a peptide representing residues 20-29 of amylin.…”

mentioning

confidence: 99%

Peptide Conformation and Supramolecular Organization in Amylin Fibrils: Constraints from Solid-State NMR

et al. 2007

View full text Add to dashboard Cite

The 37-residue amylin peptide, also known as islet amyloid polypeptide, forms fibrils that are the main peptide or protein component of amyloid that develops in the pancreas of type 2 diabetes patients. Amylin also readily forms amyloid fibrils in vitro that are highly polymorphic under typical experimental conditions. We describe a protocol for the preparation of synthetic amylin fibrils that exhibit a single predominant morphology, which we call a striated ribbon, in electron microscope and atomic force microscope images. Solid state nuclear magnetic resonance (NMR) measurements on a series of isotopically labeled samples indicate a single molecular structure within the striated ribbons. We use scanning transmission electron microscopy and several types of one-dimensional and two-dimensional solid state NMR techniques to obtain constraints on the peptide conformation and supramolecular structure in these amylin fibrils, and derive molecular structural models that are consistent with the experimental data. The basic structural unit in amylin striated ribbons, which we call the protofilament, contains four-layers of parallel β-sheets, formed by two symmetric layers of amylin molecules. The molecular structure of amylin protofilaments in striated ribbons closely resembles the protofilament in amyloid fibrils with similar morphology formed by the 40-residue β-amyloid peptide that is associated with Alzheimer's disease. Keywordsislet amyloid polypeptide; type 2 diabetes; amyloid fibril structure; electron microscopy; atomic force microscopy Amylin, also called islet amyloid polypeptide or IAPP, is a 37-residue peptide that is cosecreted with insulin by the β-cells of pancreas. The normal biological effects of amylin secretion include inhibition of glucagon secretion and reduction of the rate of gastric emptying, effects that contribute to the maintenance of postprandial glucose homeostasis (1). Amylin is the major peptide or protein component of the islet amyloid found in the pancreas of approximately 90% of type 2 (or non-insulin-dependent) diabetes patients (2,3). Fibrillar amylin has been shown * Corresponding author: Dr. Robert Tycko, National Institutes of Health, Building 5, Room 112, Bethesda, MD 20892-0520. phone 301-402-8272. fax 301-496-0825. e-mail robertty@mail.nih.gov.Supporting Information Available HPLC chromatograms from the purification of both reduced and oxidized amylin by reverse-phase chromatography ( Figure S1); FPLC chromatograms from the purification of both human and rodent amylin by size-exclusion chromatography ( Figure S2); 1D 13 C spectra of amylin fibrils with various isotopic labeling patterns, in lyophilized and rehydrated conditions ( Figures S3-S5); Table of 13 C NMR chemical shifts in amylin fibrils, TALOS predictions of backbone torsion angles based on these shifts, and torsion angles determined from 15 N fpRFDR-CT measurements (Table S1). This material is freely available on the World Wide Web at http://www.acs.org. to be toxic to cultured β-cells (4), and has been propo...

show abstract

“…Oligomers are now known to form spontaneously in human amylin solutions, among and often concomitantly with the larger, precipitable fibrillar structures that have typically been visualised by electron microscopy [26]. Amylin oligomers, which are usually at least two orders of magnitude smaller than fibrils, are initially a few nm in diameter [37].…”

mentioning

confidence: 99%

“…Misfolding of syndrome-specific proteins, termed 'monomers', leading to the formation of tissue-resident aggregates, or amyloid, formed mainly from polymorphic assemblies of these monomers [26], is clearly implicated in the pathogenesis of the neurodegenerative diseases mentioned above. There is also a group of genetically transmitted forms of amyloidosis, in which coding mutations in specific monomers cause pathogenic gainsof-function (amyloid formation and toxicity) [27][28][29][30].…”

mentioning

confidence: 99%

“…In our experience, the methods that measure the properties of individual aggregates, rather than of bulk assemblages have generally been more informative. For example, scanning-transmission electron microscopy has enabled detection and measurement of the amylin protofibril, the probable basecomponent of the higher order structures in amyloid deposits [26], and AFM has charted the dimensions and kinetics of amylin oligomer formation [37]. Zraika et al point out that many of the biophysical methods that have been informative for evaluating the properties of amyloidogenic monomers such as Aβ (the monomer of Alzheimer's disease) have proven much less effective where human amylin is concerned, probably because of its high propensity to aggregate more rapidly in aqueous solutions.…”

mentioning

confidence: 99%

See 1 more Smart Citation