CHARACTERIZATION AND PHOSPHORYLATION OF CREB-LIKE PROTEINS IN APLYSIACENTRAL-NERVOUS-SYSTEM

Studies in Aplysia californica indicate that cAMP-mediated gene expres sion is necessary for long-term facilitation, a correlate of long-term memory. It has been shown that blocking the expression of cAMP-induci ble genes in sensory neurons impedes long-term facilitation without an y effect on short-term facilitation. Specifically, blocking the bindin g of CREB-like proteins or inhibiting the expression of a cAMP-inducib le gene, C\EBP, impairs long-term facilitation. In this report, we sho w the presence of a family of CREB-like proteins in Aplysia CNS that s pecifically bind to the CRE sequence and cross-react with rat CREB ant ibodies. Similar to mammalian CREB proteins, Aplysia homologues intera ct with each other via leucine zipper domains. This interaction can be disrupted by peptides containing the CREB leucine zipper sequence. We demonstrate that a 43 kDa CREB-like protein present in CNS extracts c an be phosphorylated in vitro by cAMP-dependent protein kinase A. More over, exposure of ganglia to serotonin (5-HT), a transmitter involved in long-term facilitation, increases the phosphorylation of this prote in. This biochemical data further supports the involvement of CREB-lik e proteins in memory storage.