Rifampicin Does Not Prevent Amyloid Fibril Formation by Human Islet Amyloid Polypeptide but Does Inhibit Fibril Thioflavin-T Interactions: Implications for Mechanistic Studies of β-Cell Death

Meng, Fanling; Marek, Peter; Potter, Kathryn; Verchere, C. Bruce; Raleigh, Daniel P.

doi:10.1021/bi702518m

Cited by 86 publications

(102 citation statements)

References 50 publications

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“…35 Therefore, we examined the effect of CLR01 on IAPP fibril formation by EM (Figure 1). At t = 0, IAPP incubated in the absence or presence of MTs was predominantly amorphous.…”

Section: Acs Chemical Biologymentioning

confidence: 99%

Molecular Tweezers Inhibit Islet Amyloid Polypeptide Assembly and Toxicity by a New Mechanism

Lopes¹,

Attar²,

Nair³

et al. 2015

ACS Chem. Biol.

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In type-2 diabetes (T2D), islet amyloid polypeptide (IAPP) self-associates into toxic assemblies causing islet β-cell death. Therefore, preventing IAPP toxicity is a promising therapeutic strategy for T2D. The molecular tweezer CLR01 is a supramolecular tool for selective complexation of K residues in (poly)peptides. Surprisingly, it inhibits IAPP aggregation at substoichiometric concentrations even though IAPP has only one K residue at position 1, whereas efficient inhibition of IAPP toxicity requires excess CLR01. The basis for this peculiar behavior is not clear. Here, a combination of biochemical, biophysical, spectroscopic, and computational methods reveals a detailed mechanistic picture of the unique dual inhibition mechanism for CLR01. At low concentrations, CLR01 binds to K1, presumably nucleating nonamyloidogenic, yet toxic, structures, whereas excess CLR01 binds also to R11, leading to nontoxic structures. Encouragingly, the CLR01 concentrations needed for inhibition of IAPP toxicity are safe in vivo, supporting its development toward diseasemodifying therapy for T2D.

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“…35 Therefore, we examined the effect of CLR01 on IAPP fibril formation by EM (Figure 1). At t = 0, IAPP incubated in the absence or presence of MTs was predominantly amorphous.…”

Section: Acs Chemical Biologymentioning

confidence: 99%

Molecular Tweezers Inhibit Islet Amyloid Polypeptide Assembly and Toxicity by a New Mechanism

Lopes¹,

Attar²,

Nair³

et al. 2015

ACS Chem. Biol.

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“…This may occur because they absorb strongly which leads to inner filter effects, or because they quench the bound thioflavin-T fluorescence, or because they inhibit thioflavin-T binding to amyloid. 48,49 The compounds under study here have the potential to interfere with thioflavin-T assays. Figure 2 shows the results of a thioflavin-T-monitored kinetic experiment in the presence of Myricetin.…”

Section: Hydroxyflavones Can Interfere With Standard Fluorescence Assmentioning

confidence: 99%

Morin hydrate inhibits amyloid formation by islet amyloid polypeptide and disaggregates amyloid fibers

2012

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The polypeptide hormone Islet Amyloid Polypeptide (IAPP, amylin) is responsible for islet amyloid formation in type-2 diabetes and in islet cell transplants, where it may contribute to graft failure. Human IAPP is extremely amyloidogenic and fewer inhibitors of IAPP amyloid formation have been reported than for the Alzheimer's Ab peptide or for a-synuclein. The ability of a set of hydroxyflavones to inhibit IAPP amyloid formation was tested. Fluorescence detected thioflavin-Tbinding assays are the most popular methods for measuring the kinetics of amyloid formation and for screening potential inhibitors; however, we show that they can lead to false positives with hydroxyflavones. Several of the compounds inhibit thioflavin-T fluorescence, but not amyloid formation; a result which highlights the hazards of relying solely on thioflavin-T assays to screen potential inhibitors. Transmission electron microscopy (TEM) and right-angle light scattering show that Morin hydrate (2 0 ,3,4 0 ,5,7-Pentahydroxyflavone) inhibits amyloid formation by human IAPP and disaggregates preformed IAPP amyloid fibers. In contrast, Myricetin, Kaempferol, and Quercetin, which differ only in hydroxyl groups on the B-ring, are not effective inhibitors. Morin hydrate represents a new type of IAPP amyloid inhibitor and the results with the other compounds highlight the importance of the substitution pattern on the B-ring.

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“…However, it was recently reported that rifampicin interferes with Thioflavin T measurements, thereby negatively affecting tests for the toxicity of hIAPP fibrils (Meng, et al 2008).…”

Section: Concerns About the Toxic Oligomers Hypothesismentioning

confidence: 99%

Membrane permeabilization by Islet Amyloid Polypeptide

Engel

2009

Chemistry and Physics of Lipids

117

121

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Membrane permeabilization by Islet Amyloid Polypeptide (IAPP) is suggested to be the main mechanism for IAPP-induced cytotoxicity and death of insulin-producing -cells in type 2 diabetes mellitus (T2DM).The insoluble fibrillar IAPP deposits (amyloid) present in the pancreas of most T2DM patients are not the primary suspects responsible for permeabilization of -cell membranes. Instead, soluble IAPP oligomers are thought to be cytotoxic by forming membrane channels or by inducing bilayer disorder. In addition, the elongation of IAPP fibrils at the membrane, but not the fibrils themselves, could cause membrane disruption. Recent reports substantiate the formation of an -helical, membrane-bound IAPP monomer as possible intermediate on the aggregation pathway. Here, the structures and membrane interactions of various IAPP species will be reviewed, and the proposed hypotheses for IAPP-induced membrane permeabilization and cytotoxicity will be discussed.

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Rifampicin Does Not Prevent Amyloid Fibril Formation by Human Islet Amyloid Polypeptide but Does Inhibit Fibril Thioflavin-T Interactions: Implications for Mechanistic Studies of β-Cell Death

Cited by 86 publications

References 50 publications

Molecular Tweezers Inhibit Islet Amyloid Polypeptide Assembly and Toxicity by a New Mechanism

Molecular Tweezers Inhibit Islet Amyloid Polypeptide Assembly and Toxicity by a New Mechanism

Morin hydrate inhibits amyloid formation by islet amyloid polypeptide and disaggregates amyloid fibers

Membrane permeabilization by Islet Amyloid Polypeptide

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