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Interaction between amyloid beta peptide and an aggregation blocker peptide mimicking islet amyloid polypeptide.

ABSTRACT: Assembly of amyloid-beta peptide (A?) into cytotoxic oligomeric and fibrillar aggregates is believed to be a major pathologic event in Alzheimer's disease (AD) and interfering with A? aggregation is an important strategy in the development of novel therapeutic approaches. Prior studies have shown that the double N-methylated analogue of islet amyloid polypeptide (IAPP) IAPP-GI, which is a conformationally constrained IAPP analogue mimicking a non-amyloidogenic IAPP conformation, is capable of blocking cytotoxic self-assembly of A?. Here we investigate the interaction of IAPP-GI with A?40 and A?42 using NMR spectroscopy. The most pronounced NMR chemical shift changes were observed for residues 13-20, while residues 7-9, 15-16 as well as the C-terminal half of A?--that is both regions of the A? sequence that are converted into ?-strands in amyloid fibrils--were less accessible to solvent in the presence of IAPP-GI. At the same time, interaction of IAPP-GI with A? resulted in a concentration-dependent co-aggregation of A? and IAPP-GI that was enhanced for the more aggregation prone A?42 peptide. On the basis of the reduced toxicity of the A? peptide in the presence of IAPP-GI, our data are consistent with the suggestion that IAPP-GI redirects A? into nontoxic "off-pathway" aggregates.

SUBMITTER: Rezaei-Ghaleh N

PROVIDER: S-EPMC3102090 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Interaction between amyloid beta peptide and an aggregation blocker peptide mimicking islet amyloid polypeptide.

Rezaei-Ghaleh Nasrollah N Andreetto Erika E Yan Li-Mei LM Kapurniotu Aphrodite A Zweckstetter Markus M

PloS one 20110525 5

Assembly of amyloid-beta peptide (Aβ) into cytotoxic oligomeric and fibrillar aggregates is believed to be a major pathologic event in Alzheimer's disease (AD) and interfering with Aβ aggregation is an important strategy in the development of novel therapeutic approaches. Prior studies have shown that the double N-methylated analogue of islet amyloid polypeptide (IAPP) IAPP-GI, which is a conformationally constrained IAPP analogue mimicking a non-amyloidogenic IAPP conformation, is capable of bl ...[more]

PMID: 21633500

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Project description:Complement inhibitor C4b-binding protein (C4BP) is synthesized in liver and pancreas and composed of 7 identical alpha chains and one unique beta chain. We showed previously that C4BP binds islet amyloid polypeptide (IAPP) and affects fibril formation in vitro. Now we found that polymeric C4BP inhibited lysis of human erythrocytes incubated with monomeric IAPP while no erythrocyte lysis was observed after incubation with preformed IAPP fibrils. In contrast, monomeric alpha chain of C4BP had significantly reduced activity. Further, addition of monomeric IAPP to a rat insulinoma cell line (INS-1) resulted in decreased cell viability, which was restored in the presence of physiological concentrations of C4BP. Accordingly, addition of C4BP rescued the ability of INS-1 cells and isolated rat islets to respond to glucose stimulation with insulin secretion, which was impaired in the presence of IAPP alone. C4BP was internalized together with IAPP into INS-1 cells and therefore we aimed to study its effect on gene expression. Pathway analyses of mRNA expression microarray data indicated that cells exposed to C4BP and IAPP in comparison to IAPP alone increased expression of genes involved in cholesterol synthesis. Depletion of cholesterol through methyl-Î²-cyclodextrin or cholesterol oxidase abolished the protective effect of C4BP on IAPP cytotoxicity of INS-1 cells. Also, inhibition of phosphoinositide 3-kinase but not NF-ÎºB had a similar effect. Taken together, one of the mechanisms by which C4BP protects beta-cells from IAPP cytotoxicity is by enhancing cholesterol synthesis. The INS-1 cells were grown as 5 separate clones for 10 passages before plating in a 12-well plate (Nunc) at 100.000 cells per well and grown in complete RPMI 1640 medium to 70% confluency for approximately 48 h. The cells were then challenged by adding 77 Î¼M monomeric IAPP alone or together with C4BP (0.6 Î¼M). DMSO (1%) used as solvent for IAPP as well as C4BP (0.6 Î¼M) alone were used as controls. RNA was extracted after 10h incubation and analysis carried out using Rat Gene 2.0 array chip (Affymetrix).

Dataset Information

Interaction between amyloid beta peptide and an aggregation blocker peptide mimicking islet amyloid polypeptide.

Publications

Interaction between amyloid beta peptide and an aggregation blocker peptide mimicking islet amyloid polypeptide.

Similar Datasets

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