Prions in Long-term Memory and Learning

In the 1990’s, a Mad Cow Disease epidemic in Great Britain resulted in the destruction of about one million cattle. The cause of the epidemic was believed to be the ingestion of feed contaminated with a new and strange kind of pathogen devoid of nucleic acids. According to the prion hypothesis, misfolded prion protein is the infectious agent that results in the transmission of prion disease. Thus, prions, which may present as genetic, infectious or sporadic disorders, have the ability to produce some fatal neurodegenerative diseases by an intriguing novel mechanism that involves a posttranslational change in cellular proteins. While the prion hypothesis was developed to explain these unusual neurodegenerative diseases, increasing data suggest that prion-based mechanisms underlie normal biological processes. For example, in yeast, the Sup35 protein functions as a translation termination factor. Under severe stress, this protein undergoes a prion-like switch from a functional soluble protein to a nonfunctional aggregated one. Translation through the normal stop codon results in C-terminal extended proteins with novel potentially beneficial functions. This presentation focuses on an analogous story that is emerging as a molecular mechanism underlying the processes of learning and memory. The story focuses on a “cytoplasmic polyadenylation element-binding protein” (CPEB), which has been implicated in synaptic plasticity and long-term memory maintenance