The Role of Cofactors in Prion Propagation and Infectivity

The term ‘‘prion’’ was originally coined by Prusiner to explain the unusual infectious agent in transmissible spongiform encephalopathies (TSEs, also known as prion disease) [1]. Now the term has expanded to include a growing list of fungal proteins that stably maintain an atypical self-propagating conformation and epigenetically modify a variety of cellular processes [2]. Although fungal prions and the TSE agent share the capability of maintaining an atypical self-propagating conformation, fungal prions distinctly differ from the TSE agent in several aspects [3]. Thus far, the TSE agent is the only prion that behaves as a bona fide infectious agent, having an infectious cycle, capable of transmitting horizontally (among a community) and causing epidemic outbreaks [3]. The discussion in this article will be focused on mammalian prion, and the term ‘‘prion’’ specifically refers to the infectious TSE agent.