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Exploring the F-actin/CPEB3 interaction and its possible role in the molecular mechanism of long-term memory

Significance The growth and stabilization of dendritic spines is thought to be essential for strengthening the connections between neurons and thereby memories. Actin cytoskeleton remodeling in spines is the basis of this growth and stabilization. A functional prion that binds mRNA, CPEB3, which interacts with actin, has been reported to be involved in the maintenance of long-term memory by forming stable aggregates. Here we study the interaction between actin and CPEB3 and propose a molecular model for the complex structure of CPEB3 bound to an actin filament. Our model gives insights into the actin/CPEB3 positive feedback loop underlying long-term memory which involves CPEB3’s binding to actin, its aggregation, and its regulation by SUMOylation. Dendritic spines are tiny membranous protrusions on the dendrites of neurons. Dendritic spines change shape in response to input signals, thereby strengthening the connections between neurons. The growth and stabilization of dendritic spines is thought to be essential for maintaining long-term memory. Actin cytoskeleton remodeling in spines is a key element of their formation and growth. More speculatively, the aggregation of CPEB3, a functional prion that binds RNA, has been reported to be involved in the maintenance of long-term memory. Here we study the interaction between actin and CPEB3 and propose a molecular model for the complex structure of CPEB3 and an actin filament (F-actin). The results of our computational modeling, including both energetic and structural analyses, are compared with novel data from peptide array experiments. Our model of the CPEB3/F-actin interaction suggests that F-actin potentially triggers the aggregation-prone structural transition of a short CPEB3 sequence by zipping it into a beta-hairpin form. We also propose that the CPEB3/F-actin interaction might be regulated by the SUMOylation of CPEB3, based on bioinformatic searches for potential SUMOylation sites as well as SUMO interacting motifs in CPEB3. On the basis of these results and the existing literature, we put forward a possible molecular mechanism underlying long-term memory that involves CPEB3’s binding to actin, its aggregation, and its regulation by SUMOylation.