Prion Strains and Amyloid Polymorphism Influence Phenotypic Variation

The deposition of protein aggregates is a unifying feature of a large class of diseases known as protein conformational disorders, which includes Alzheimer disease and prion diseases. One of the most fascinating and puzzling aspects of such diseases is the phenomenon of amyloid polymorphism, whereby a single disease-associated protein forms different types of ordered aggregate structures. This is best exemplified in prion diseases, in which these different structures, called prion strains, are responsible for much of the variation in pathology and disease transmission. Here, we review the current knowledge of prion strains and amyloid polymorphism, highlighting how diversity in amyloid structure relates to phenotypic differences.