Structures of Pathological and Functional Amyloids and Prions, a Solid-State NMR Perspective
Asen Daskalov, Nadia El Mammeri, Alons Lends, Jayakrishna Shenoy, Gaëlle Lamon, Yann Fichou, Ahmad Saad, Dênis Martinez, Estelle Morvan, Mélanie Berbon, Axelle Grélard, Brice Kauffmann, Mathias Ferber, Benjamin Bardiaux, Birgit Habenstein, Sven J. Saupe, Antoine Loquet
Abstract
Infectious proteins or prions are a remarkable class of pathogens, where pathogenicity and infectious state correspond to conformational transition of a protein fold. The conformational change translates into the formation by the protein of insoluble amyloid aggregates, associated in humans with various neurodegenerative disorders and systemic protein-deposition diseases. The prion principle, however, is not limited to pathogenicity. While pathological amyloids (and prions) emerge from protein misfolding, a class of functional amyloids has been defined, consisting of amyloid-forming domains under natural selection and with diverse biological roles. Although of great importance, prion amyloid structures remain challenging for conventional structural biology techniques. Solid-state nuclear magnetic resonance (SSNMR) has been preferentially used to investigate these insoluble, morphologically heterogeneous aggregates with poor crystallinity. SSNMR methods have yielded a wealth of knowledge regarding the fundamentals of prion biology and have helped to solve the structures of several prion and prion-like fibrils. Here, we will review pathological and functional amyloid structures and will discuss some of the obtained structural models. We will finish the review with a perspective on integrative approaches combining solid-state NMR, electron paramagnetic resonance and cryo-electron microscopy, which can complement and extend our toolkit to structurally explore various facets of prion biology.