title: Mechanical stress affects glucagon fibrillation kinetics and fibril structure.
abstract: Mechanical stress can strongly influence the capability of a protein to aggregate and the kinetics of aggregation, but there is little insight into the underlying mechanism. Here we study the effect of different mechanical stress conditions on the fibrillation of the peptide hormone glucagon, which forms different fibrils depending on temperature, pH, ionic strength, and concentration. A combination of spectroscopic and microscopic data shows that fibrillar polymorphism can also be induced by mechanical stress. We observed two classes of fibrils: a low-stress and a high-stress class, which differ in their kinetic profiles, secondary structure as well as morphology and that are able to self-propagate in a template-dependent fashion. The bending rigidity of the low-stress fibrils is sensitive to the degree of mechanical perturbation. We propose a fibrillation model, where interfaces play a fundamental role in the switch between the two fibrillar classes. Our work also raises the cautionary note that mechanical perturbation is a potential source of variability in the study of fibrillation mechanisms and fibril structures.
authors.affiliation: iNANO, Center for Insoluble Protein Structures (inSPIN), Department of Molecular Biology, Aarhus University, Gustav Wieds Vej 10C, DK-8000 Aarhus C, Denmark.
authors.forename: Francesca
authors.initials: F
authors.lastname: Macchi
authors.forename: Søren V
authors.initials: SV
authors.lastname: Hoffmann
authors.forename: Martin
authors.initials: M
authors.lastname: Carlsen
authors.forename: Brian
authors.initials: B
authors.lastname: Vad
authors.forename: Alberto
authors.initials: A
authors.lastname: Imparato
authors.forename: Christian
authors.initials: C
authors.lastname: Rischel
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Otzen
mesh_terms: D002942:Circular Dichroism; D005934:Glucagon / Q000737:chemistry*; D007700:Kinetics; D018625:Microscopy, Atomic Force; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000145:classification; D058105:Polymerization; D017550:Spectroscopy, Fourier Transform Infrared; D013314:Stress, Mechanical
chemical_list: D046912:Multiprotein Complexes; D005934:Glucagon