In several
neurodegenerative disorders,
proteins that typically exhibit an α-helical structure misfold into an
amyloid conformation rich in β-sheet content. Through a self-templating mechanism, these amyloids are able to induce additional
protein misfolding, facilitating their propagation throughout the central nervous system. This disease mechanism was originally identified for the
prion protein (PrP), which misfolds into PrPSc in a number of disorders, including
variant Creutzfeldt-Jakob disease (vCJD) and
bovine spongiform encephalopathy (BSE). More recently, the
prion mechanism of disease was expanded to include other
proteins that rely on this self-templating mechanism to cause progressive degeneration, including α-
synuclein misfolding in
Parkinson's disease (PD). Several studies now suggest that PD patients can be subcategorized based on where in the body misfolded α-
synuclein originates, either the brain or the gut, similar to patients developing
sporadic CJD or vCJD. In this review, we discuss the human and animal model data indicating that α-
synuclein and PrPSc misfolding originates in the gut in body-first PD and vCJD, and summarize the data identifying the role of the autonomic nervous system in the gut-brain axis of both diseases.