Several neurodegenerative diseases such as transmissible spongiform 
encephalopathies, Alzheimer's and Parkinson's diseases are caused by the 
conversion of cellular proteins to a pathogenic conformer. Despite differences 
in the primary structure and subcellular localization of these proteins, which 
include the prion protein, α-synuclein and amyloid precursor protein (APP), 
striking similarity has been observed in their ability to seed and convert naïve 
protein molecules as well as transfer between cells. This review aims to cover 
what is known about the intracellular trafficking of these proteins as well as 
their degradation mechanisms and highlight similarities in their movement 
through the endocytic pathway that could contribute to the pathogenic conversion 
and seeding of these proteins which underlies the basis of these diseases.