Critical Role of Amyloid-like Oligomers of Drosophila Orb2 in the Persistence of Memory

Abstract

A long-standing question in the study of long-term memory is how a memory trace persists for years when the proteins that initiated the process turn over and disappear within days. Previously, we postulated that self-sustaining amyloidogenic oligomers of cytoplasmic polyadenylation element-binding protein (CPEB) provide a mechanism for the maintenance of activity-dependent synaptic changes and, thus, the persistence of memory. Here, we found that the Drosophila CPEB Orb2 forms amyloid-like oligomers, and oligomers are enriched in the synaptic membrane fraction. Of the two protein isoforms of Orb2, the amyloid-like oligomer formation is dependent on the Orb2A form. A point mutation in the prion-like domain of Orb2A, which reduced amyloid-like oligomerization of Orb2, did not interfere with learning or memory persisting up to 24 hr. However the mutant flies failed to stabilize memory beyond 48 hr. These results support the idea that amyloid-like oligomers of neuronal CPEB are critical for the persistence of long-term memory.

Evolutionarily conserved intercalated disc protein Tmem65 regulates cardiac conduction and connexin 43 function

“…These data suggest a possibly unique function for the dimer in the developed heart. The dimer was stable to heat even in SDS 14,15 , but was monomerized by heating the adult cardiac lysate in 6M urea 14 ( Supplementary Fig. 1b).…”

Long-term memory consolidation: The role of RNA-binding proteins with prion-like domains

“…The Orb2A has a short 8 amino acid stretch whereas in Orb2B isoform it is 162 amino acids long. 147,148 Both Orb2A and Orb2B interact with transcripts of Tequila, DaPKC and Murashka, which are required for LTM formation. Removal of the Zn finger RNAbinding domain from the Orb2B isoform abolishes its association with these target mRNA suggestive of direct interaction with target RNAs.…”

Prions, amyloids, and RNA: Pieces of a puzzle

“…Mutational inactivation of Orb2A oligomerization leads to the impairment of long-term memory. 161 Moreover, Orb2A stability and oligomerization was observed to be controlled by the protein network consisting of Lim kinase, protein phosphatase 2A, and Tob transcription regulator. 169 Finally, three recent manuscripts analyzed aggregation and self-perpetuation of the mouse ortholog of ApCPEB, CPEB3.…”

“…Remarkable examples of the translation-coupled functional amyloids in multicellular organisms are neuron-specific forms of the cytoplasmic polyadenylation element binding protein (CPEB), ApCPEB, Orb2, and CPEB3 in the mollusk Aplysia californica, 24,159,160 fruit fly Drosophila melanogaster, 161 and mouse, 59,162,163 correspondingly. CPEB represents a family of RNA-binding proteins that bind U-rich sequences called CPE elements, which are located in the 3 0 untranslated regions of a number of cellular mRNAs.…”

“…160,168 Like ApCPEB, Orb2 exists in two states in the brain of D. melanogaster, monomeric and amyloid-like oligomeric. Multimerization of Orb2 is induced following stimulation with dopamine, octopamine, or tyramine, and persists up to 24 h. 161 The Orb2 locus encodes six proteins, only two of which, Orb2A and Orb2B, are CPEB orthologs containing the same prion domain. Orb2A is shorter and, being fused to GFP, forms fluorescent foci, while Orb2B does not form aggregates alone.…”