Structure and cytotoxicity of novel insulin noodle-like filamentous amyloids

• Published in: The FEBS journal Vol. 276; no. Suppl. s1; p. 173
• Main Authors: Zako, T., Kobayashi, T., Sakono, M., Lindgren, M., Hammarström, Per, Nilsson, Peter, Maeda, M.
• Format: Journal Article
• Language: English
• Published: 2009
• Subjects: NATURAL SCIENCES; NATURVETENSKAP
• ISSN: 1742-4658; 1742-464X
• DOI: 10.1111/j.1742-4658.2009.07049.x

Insulin is a small peptide hormone that is known to form proteinassembly called amyloid fibrils under acidic conditions. We havepreviously shown that filamentous (‘noodle’-like) insulin amyloidwhich was morphologically different from fibrous (‘needle’-like)insulin amyloid was formed in the presence of a reducing agent,tris (2-carboxyethyl) phosphine hydrochloride (TCEP). The CDspectra showed that both of insulin fibrils and filaments containa beta-sheet structure. Nevertheless, Thioflavin T (ThT) bindingproperty was very different between them, suggesting a differencein inner structure. In this study, we examined their cell toxicitiesusing two different cell lines with MTT assay, and also examineddifference in their inner structures using novel luminescent conjugatedpolyelectrolyte probes (LCPs) 1–4 . The cytotoxicity of theinsulin filaments against rat PC12 and human HEK293 cell linewas also extremely low while the fibrils were toxic, suggestingthat the insulin filaments were generally nontoxic. This findingsupports the idea that cell toxicity of amyloids correlates withtheir morphology. The fluorescence measurement in the presenceof Polythiophene acetic acid (PTAA) 1–4 , one of the conformationsensitive LCPs, showed that PTAA weakly bound to the insulinfilaments and that the insulin fibrils’ spectrum revealed a spectral red shift in comparison to the PTAA-filaments interaction. Thissuggests that the insulin ‘noodle’-like filaments are formed byloose assembly of insulin molecules. References: 1. Nilsson et al., Adv Mat 2008; 20: 2639. 2. Chem Bio Chem 2006; 7:1096. 3. ACS Chem Biol 2007; 4: 553. 4. Sigurdson et al., Nature Methods 2007; 4: 1023.