Nuclear gating of a Drosophila dCREB2 activator is involved in memory formation

• The majority of dCREB2-encoded protein is cytoplasmic.
• Long-term memory formation transiently increases nuclear abundance of p35.
• The precursor of p35 is probably tethered by other dCREB2 isoforms in the cytoplasm.
• S6K induction increases dCREB2 proteins in the nucleus.
• S6K induction enhances long-term memory formation.

The transcription factor CREB is an important regulator of many adaptive processes in neurons, including sleep, cellular homeostasis, and memory formation. The Drosophila dCREB2 family includes multiple protein isoforms generated from a single gene. Overexpression of an activator or blocker isoform has been shown to enhance or block memory formation, but the molecular mechanisms underlying these phenomena remain unclear. In the present study, we generate isoform-specific antibodies and new transgenic flies to track and manipulate the activity of different dCREB2 isoforms during memory formation. We find that nuclear accumulation of a dCREB2 activator-related species, p35+, is dynamically regulated during memory formation. Furthermore, various dCREB2 genetic manipulations that enhance or block memory formation correspondingly increase or decrease p35+ levels in the nucleus. Finally, we show that overexpression of S6K can enhance memory formation and increase p35+ nuclear abundance. Taken together, these results suggest that regulation of dCREB2 localization may be a key molecular convergence point in the coordinated host of events that lead to memory formation.