Prions and memory

As we now know Prions are really just misshapen forms of a normal protein that occurs in everyone. This raises the important question of just what these 'normal' prions do in the body. One suggestion is that they may be involved in the maintenance of memory:  Prions as adaptive conduits of memory and inheritance (in yeast) and Hippocampal synaptic plasticity in mice devoid of cellular prion protein (in mice). From the first paper:

Any molecular basis for long-term memory formation must explain its endurance (for many years) despite the continuous turnover (every few hours) of the proteins that might encode them. Information storage despite molecular turnover is traditionally explained by autophosphorylation loops, self-sustaining feedback loops in complex signalling networks, or transcription factors that stimulate their own synthesis once they cross a threshold concentration. The conformational replication of prions provides another durable form of molecular memory. Moreover, as is clear from studies in yeast, prion conformations are not usually toxic. Incredibly, prion-based mechanisms might operate in individual neuronal synapses to maintain their growth and contingent long-term facilitation.

Fungal prions are proving to be a very useful model organism for studying mammalian prions since numerous forms have now been identified, they are infectious and self-replicating like mammalian prions but they do not appear to be associated with disease in fungi. In fact there are several suggestions they may have aided fungal evolution.