Project Summary The aggregate failure of pre-clinical and clinical trials in AD has demonstrated that an improved fundamental understanding of memory and how the molecular components of memory are altered in the AD disease process is necessary to develop effective treatment. The broad objective of the project is to identify the biochemical substrates of long-lasting memories in mammals. The current proposal focuses on a family of RNA-binding, cytoplasmic polyadenylation element binding protein (CPEB), that stabilizes memory in invertebrates and mice. Remarkably, CPEB family protein forms non-disease-causing amyloidogenic aggregates and aggregation of CPEB is necessary to stabilize memory. As amyloids are typically linked to disease states, the question remains how similarly structured Aβ42 or Tau proteins can have opposing effects on memory. Therefore, to develop a better understanding of the relationship between amyloids that support memory and amyloids that disrupt memory, we will use a variety of techniques to solve the structure and function of the CPEB family members, CPEB2 and CPEB3, in human and mice. In Aim 1, we will use cryo- electron microscopy to solve the structure of CPEB aggregates from fresh human frontotemporal lobe tissue collected from 25-50-year-old human subjects undergoing tissue removal under the standard of care for their disease. These tissues would have been otherwise discarded. In Aim 2, mice lacking the ability to form aggregates of CPEB2 and CPEB3 will be trained and tested in a one-trial inhibitory avoidance task to assay their ability to form, maintain, and recall memory. In Aim 2 we will also investigate the consequence of CPEB2 and CPEB3 aggregation in translation of mRNA encoding synaptic proteins. The results would be the first to provide direct structural analysis of a functional amyloid linked to memory in mammals, the structural distinctions, if any, between functional and toxic amyloid in the human brain, and precisely link CPEB2 and CPEB3 aggregation and activity to animals’ ability to form or stabilize memory. This knowledge would provide the foundation to investigate in the future how toxic amyloids of Aβ42 or Tau specifically perturb memory.