Small‐Molecule Inhibitors of Islet Amyloid Polypeptide Fibril Formation

Mishra, Rajesh; Bulic, Bruno; Sellin, Daniel; Jha, Suman; Waldmann, Herbert; Winter, Roland

doi:10.1002/ange.200705372

Cited by 33 publications

(35 citation statements)

References 31 publications

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“…The small molecule is most efficient when present at a 1:1 ratio (mol:mol), suggesting that it interacts with the monomeric state of the protein or with an assembly formed in the early stages of self-assembly. 26,27 More recently, we showed that curcumin modulates the self-assembly of IAPP by unfolding α-helix. 28 Because of its insolubility in water, curcumin stock solutions were prepared in 100% ethanol.…”

mentioning

confidence: 99%

Kinetic Profile of Amyloid Formation in the Presence of an Aromatic Inhibitor by Nuclear Magnetic Resonance

Liu

Gaines

Robbins

et al. 2012

ACS Med. Chem. Lett.

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The self-assembly of amyloid proteins into β-sheet rich assemblies is associated with human amyloidoses including Alzheimer's disease, Parkinson's disease, and type 2 diabetes. An attractive therapeutic strategy therefore is to develop small molecules that would inhibit protein self-assembly. Natural polyphenols are potential inhibitors of β-sheet formation. How these compounds affect the kinetics of self-assembly studied by thioflavin T (ThT) fluorescence is not understood primarily because their presence interferes with ThT fluorescence. Here, we show that by plotting peak intensities from nuclear magnetic resonance (NMR) against incubation time, kinetic profiles in the presence of the polyphenol can be obtained from which kinetic parameters of self-assembly can be easily determined. In applying this technique to the selfassembly of the islet amyloid polypeptide in the presence of curcumin, a biphenolic compound found in turmeric, we show that the kinetic profile is atypical in that it shows a prenucleation period during which there is no observable decrease in NMR peak intensities. KEYWORDS: amyloid, ThT fluorescence, curcumin, NMR A total of 27 proteins have been identified to form the extracellular β-sheet containing amyloid fibrils associated with human amyloidoses. 1 These include the amyloid-β protein (Aβ) in Alzheimer's disease, α-synuclein in Parkinson's disease, and the islet amyloid polypeptide (IAPP) in type 2 diabetes (T2D). In spite of the large differences in the primary structure of the precursor proteins, the mature fibrils possess common characteristics including unbranched, 10 nm wide morphology as determined by electron microscopy, the ability to bind Congo red and exhibit green birefringence, and X-ray diffraction patterns consistent with cross-β-sheet. 1 Mechanistic studies of fibril formation in hydro have shown that Aβ, α-synuclein, and IAPP undergo a random coil to β-sheet conformational transition. 2 IAPP is a 37-residue polypeptide ( Figure 1A) that is cosecreted with insulin by β-cells of the islets of Langerhans in the pancreas. Molecular biological, biophysical, and genetic evidence support a central role for IAPP in β-cell death and dysfunction associated with T2D. 3,4 The progressive formation of islet amyloid leads to a decrease in β-cell mass. 5 The toxicity of fibrillar IAPP was first demonstrated in the early 1990s, 6 but more recent studies suggest that oligomeric assemblies could be the proximate cytotoxic species in T2D. 3,7 A number of mechanisms behind the toxicity of IAPP oligomers have been proposed, 8 but recent biophysical studies have focused on the ability of IAPP to disrupt model membranes, as reviewed recently. 3 A missense mutation involving the substitution of serine at position 20 with glycine ( Figure 1A) has been linked to an early onset, more severe form of T2D. 9 The mutant polypeptide aggregates faster 10,11 and is more toxic than wildtype IAPP. 10 Together, these findings suggest that molecules that significantly delay or completely inhibit IAP...

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confidence: 99%

Kinetic Profile of Amyloid Formation in the Presence of an Aromatic Inhibitor by Nuclear Magnetic Resonance

Liu

Gaines

Robbins

et al. 2012

ACS Med. Chem. Lett.

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“…By itself, resveratrol is a potent anti-oxidant which is thought to be responsible for the French Paradox [65]; relating to the low incidence of cardiovascular disease in a French population with high intake of saturated fats. In addition to its demonstrated capacity to inhibit (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35) fibril formation in vitro [16], resveratrol is also capable of promoting intracellular uptake and degradation of through a proteosome-dependent mechanism [66] and protecting against -induced neurotoxicity [67,68], possibly through activation of the NAD-dependent histone deacetylase, SIRT1 [69]. In the present study using the ELISA-based assay, catechin showed no inhibitory activity during the early stages of oligomerization, whereas rosmarinic acid demonstrated some activity at the highest concentration tested.…”

Section: Discussionmentioning

confidence: 99%

“…While the identity of a number of oligomerization inhibitors have been reported, few address the stoichiometric relationship between inhibitor and peptide, and when calculated, suggest inhibitor to peptide ratios of no greater than one, or in some cases less than one [26][27][28][29][30][31][32]. Presuming that inhibitors must physically bind to peptide to prevent oligomerization [33,34], it is difficult to imagine a mechanism of action where inhibitor to peptide ratios are less than 1.…”

Section: Introductionmentioning

confidence: 99%

A Sensitive Aβ Oligomerization Assay for Identification of Small Molecule Inhibitors

Gonzales¹,

Orlando²

2009

TOBIOTJ

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Amyloid deposits found in Alzheimer's disease result from aggregation of peptide which leads to loss of synaptic function, chronic microglial activation and cognitive impairment. Because of this, identification of small molecule inhibitors of aggregation as potential therapeutics is a topic of current interest. The majority of inhibitor screening approaches rely on in vitro assays that lack the necessary sensitivity to distinguish low-molecular weight oligomers from larger, more advanced-stage fibrillar structures. Differentiating between these two structures is of vital concern since recent studies indicate that small, early-stage oligomers are the most neurotoxic form of peptide aggregate. To address this limitation, we have explored the adaptability of a recently described ELISA-based assay for discovery of small molecule inhibitors of oligomerization. Results show that this assay is highly sensitive as it is able to quantify oligomers with as little as 80 nM input peptide. In addition, data were obtained re-confirming the function of curcumin as a potent inhibitor of aggregation (IC 50 = 2 μM) and defining its inhibitor:peptide functional stoichiometry. Further examination of other known anti-aggregation compounds showed that this assay is able to discriminate between inhibitors of early-stage, low-molecular weight oligomers and later-stage, high-molecular weight fibrillar structures. These findings indicate that this new ELISA-based assay is capable of identifying novel small molecule inhibitors that function during the initial stages of peptide assembly.

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“…In contrast to synthetic chemistry, inhibitions of their formations are studied in biochemistry. For example, islet amyloid fibril formation (IAPP) stabilized by hydrogen bonds, which is involved in devastating diseases such as type II diabetes mellitus, can be prevented by altering the amino-acid sequence 23 and analogs of IAPP methylated at amide bonds, 24,25 as well as by using small molecules 26,27 as inhibitors, which act by replacing interactions such as hydrogen bonds and p-p stacking during a part of amyloid fibril formation. Inspired by these interesting phenomena, we wanted to explore whether a chiral-conjugated polymer acts as an inhibitor of tubules or fibers assembled by the p-stacking interaction of an opposite chiralconjugated polymer.…”

Section: Introductionmentioning

confidence: 99%

Quantum yield and morphology control of BODIPY-based supramolecular self-assembly with a chiral polymer inhibitor

Nagai

Kokado

Miyake

et al. 2010

Polym J

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Chiral rod-coil-type organoboron polymers S-poly and R-poly were prepared from the palladium-catalyzed SonogashiraHagihara coupling reaction of boron dipyrromethene-based monomer 1, which has bisiodophenyl and decyl groups with S-or R-6,6¢-diethynyl-2,2¢-dioctyloxy-1,1¢-binaphthyls (S-2 and R-2), in a solvent mixture (tetrahydrofuran (THF)/triethylamine¼2/1 (v/v)) at 40 1C for 24 h. The obtained polymers were characterized by hydrogen-1 nuclear magnetic resonance (NMR), carbon-13 NMR ( 13 C NMR), boron-11 NMR ( 11 B NMR) and infrared spectroscopy. The scanning electron microscopy (SEM) analysis of each chiral polymer clearly revealed micrometer-sized fiber-like structures formed by the aggregation of each particle, as we expected. Next, we examined the relationship between the ratio of photoluminescence (PL) intensity (I/I 0 ¼R-poly/S-poly) and particle diameter, measured by dynamic light scattering analysis, versus the R-poly content of the mixed polymer of S-poly and R-poly in THF, which varied from 0 to 100%. As a result, the PL intensity and diameter showed maximum and minimum (about 32 nm) values, respectively, at 70% content, depending on the differences between both the molecular weights and absolute values of the chiral characters. These findings indicate that the PL intensity of S-poly influences morphology change by adding R-poly; that is, R-poly acts as an inhibitor toward the aggregation of S-poly. Furthermore, the SEM image of the mixed polymer (S-poly/R-poly¼30/70) showed complete particle structures from nano-to micrometer sizes, which were roughly 480 nm to 1.19 lm in diameter, and the U F of the mixed polymer was significantly high (0.98).

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Small‐Molecule Inhibitors of Islet Amyloid Polypeptide Fibril Formation

Cited by 33 publications

References 31 publications

Kinetic Profile of Amyloid Formation in the Presence of an Aromatic Inhibitor by Nuclear Magnetic Resonance

Kinetic Profile of Amyloid Formation in the Presence of an Aromatic Inhibitor by Nuclear Magnetic Resonance

A Sensitive Aβ Oligomerization Assay for Identification of Small Molecule Inhibitors

Quantum yield and morphology control of BODIPY-based supramolecular self-assembly with a chiral polymer inhibitor

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