PKA-activated ApAF-ApC/EBP heterodimer is a key downstream effector of ApCREB and is necessary and sufficient for the consolidation of long-term facilitation

Long-term memory requires transcriptional regulation by a combination of positive and negative transcription factors. Aplysia activating factor (ApAF) is known to be a positive transcription factor that forms heterodimers with ApC/EBP and ApCREB2. How these heterodimers are regulated and how they participate in the consolidation of long-term facilitation (LTF) has not, however, been characterized. We found that the functional activation of ApAF required phosphorylation of ApAF by PKA on Ser-266. In addition, ApAF lowered the threshold of LTF by forming a heterodimer with ApCREB2. Moreover, once activated by PKA, the ApAF-ApC/EBP heterodimer transactivates enhancer response element-containing genes and can induce LTF in the absence of CRE- and CREB-mediated gene expression. Collectively, these results suggest that PKA-activated ApAF-ApC/EBP heterodimer is a core downstream effector of ApCREB in the consolidation of LTF.