title: Influence of the protein context on the polyglutamine length-dependent elongation of amyloid fibrils.
abstract: Polyglutamine (polyQ) diseases, including Huntington's disease, are neurodegenerative disorders associated with the abnormal expansion of a polyQ tract within nine proteins. The polyQ expansion is thought to be a major determinant in the development of neurotoxicity, triggering protein aggregation into amyloid fibrils, although non-polyQ regions play a modulating role. In this work, we investigate the relative importance of the polyQ length, its location within a host protein, and the conformational state of the latter in the amyloid fibril elongation. Model polyQ proteins made of the β-lactamase BlaP containing up to 79Q inserted at two different positions, and quartz crystal microbalance and atomic force microscopy were used for this purpose. We demonstrate that, independently of the polyQ tract location and the conformational state of the host protein, the relative elongation rate of fibrils increases linearly with the polyQ length. The slope of the linear fit is similar for both sets of chimeras (i.e., the elongation rate increases by ~1.9% for each additional glutamine), and is also similar to that previously observed for polyQ peptides. The elongation rate is, however, strongly influenced by the location of the polyQ tract within BlaP and the conformational state of BlaP. Moreover, comparison of our results with those previously reported for aggregation in solution indicates that these two parameters also modulate the ability of BlaP-polyQ chimeras to form the aggregation nucleus. Altogether our results suggest that non-polyQ regions are valuable targets in order to interfere with the process of amyloid fibril formation associated with polyQ diseases.
authors.affiliation: Laboratory of Enzymology and Protein Folding, Centre for Protein Engineering, University of Liege, Liege, Belgium.
authors.forename: Céline
authors.initials: C
authors.lastname: Huynen
authors.affiliation: Nanochemistry and Molecular Systems, Department of Chemistry, University of Liege, Liege, Belgium.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Willet
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
authors.forename: Alexander K
authors.initials: AK
authors.lastname: Buell
authors.affiliation: Nanochemistry and Molecular Systems, Department of Chemistry, University of Liege, Liege, Belgium.
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Duwez
authors.affiliation: Center for Education and Research on Macromolecules (CERM), Department of Chemistry, University of Liege, Liege, Belgium.
authors.forename: Christine
authors.initials: C
authors.lastname: Jerôme
authors.affiliation: Laboratory of Enzymology and Protein Folding, Centre for Protein Engineering, University of Liege, Liege, Belgium. Electronic address: mdumoulin@ulg.ac.be.
authors.forename: Mireille
authors.initials: M
authors.lastname: Dumoulin
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000648:ultrastructure*; D001665:Binding Sites; D046912:Multiprotein Complexes / Q000737:chemistry / Q000648:ultrastructure; D010455:Peptides / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D000682:Amyloid; D046912:Multiprotein Complexes; D010455:Peptides; C097188:polyglutamine
keywords: Amyloid fibrils; Atomic force microscopy (AFM); BlaP-polyQ chimeras; Fibril elongation; Fibril nucleation; Quartz crystal microbalance (QCM)