Is tau ready for admission to the prion club?

Aggregation-prone proteins associated with neurodegenerative disease, such as alpha-synuclein and beta-amyloid, now appear to share key prion-like features with mammalian prion protein, such as the ability to recruit normal proteins to aggregates and to translocate between neurons. These features may shed light on the genesis of stereotyped lesion development patterns in conditions such as Alzheimer disease and Lewy body dementia. We discuss the qualifications of tau protein as a possible prionoid mediator of lesion spread based on recent characterizations of the secretion, uptake and transneuronal transfer of human tau isoforms in a variety of tauopathy models, and in human patients. In particular, we consider (1) the possibility that prionoid behavior of misprocessed tau in neurodegenerative disease may involve other aggregation-prone proteins, including PrP itself and (2) whether prionlike tau lesion propagation might include mechanisms other than protein-protein templating.