Divergent CPEB prion-like domains reveal different assembly mechanisms for a generic amyloid-like fold

Abstract

Functional amyloids are present in a wide variety of organisms ranging from bacteria to humans. Experience-dependent aggregation of the cytoplasmic polyadenylation element-binding (CPEB) prion-like protein to a translationally active state has emerged as a plausible biochemical substrate of long-lasting memories. CPEB aggregation is driven by prion-like domains (PLD) that are highly divergent in sequence across species. Here, we describe the amyloid-like features of the neuronal Aplysia CPEB (ApCPEB) PLD in vitro using single-molecule and bulk biophysical methods and compare them with those previously reported for neuronal Drosophila CPEB, Orb2 PLD. The existence of transient oligomers and mature filaments suggests similarities in the late stages of the assembly pathway for both PLDs. However, while prior to aggregation the Orb2 PLD monomer remains as a random coil in solution, ApCPEB PLD adopts a diversity of conformations comprising -helical structures that evolve to coiled-coil species, suggesting structural differences at the beginning of their amyloid assembly pathways. Our results show how divergent PLDs of CPEB proteins from different species retain the ability to form a generic amyloid-like fold through different assembly mechanisms.