The HET-S/s Prion Motif in the Control of Programmed Cell Death.

The [Het-s] prion of the fungus Podospora anserina is a well-studied model system to elucidate the action of prions and beyond. The [Het-s] prion works as an activation trigger of a cell death execution protein termed HET-S. Amyloid transconformation of the prion-forming region of HET-S induces activation of its pore-forming cell death execution HeLo domain. The prion motif functions in a signal transduction process by which a nucleotide-binding oligomerization domain (NOD)-like receptor termed NWD2 controls the HET-S cell death effector. This prion motif thus corresponds to a functional amyloid motif, allowing a conformational crosstalk between homologous motif domains in signal transduction processes that appears to be widespread from the fungal to the mammalian animal kingdoms. This review aims to establish a structure-activity relationship of the HET-S/s prion system and sets it in the context of its wider biological significance.