タイトル：Role of A Nucleolar Protein ApLLP in Synaptic Plasticity and Memory
演者：Bong-Kiun Kaang (School of Biological Sciences&s_comma; College of Natural
Sciences&s_comma; Seoul National University)
Synaptic plasticity is a key feature of long-term memory formation in various organisms. Previously&s_comma; we cloned a LAPS18-like protein in Aplysia (ApLLP) and showed that ApLLP is localized in the nucleus&s_comma; mainly in the nucleolus&s_comma; and its localization is mediated by N- and C-terminal nuclear localization signals (NLSs) (Kim et al.&s_comma; 2003). In Limax marginatus&s_comma; the ApLLP homologue Learning Associative Protein of Slug 18 kD (LAPS18) is induced by odor-taste associative learning&s_comma; which evokes odor avoidance by association of conditioned stimulus (carrot juice smell) and unconditioned stimulus (quinidine sulfate solution) (Nakaya et al.&s_comma; 2001). These results suggested that LAPS18 might be involved in the synthesis of RNA or protein&s_comma; which is required for long-term synaptic plasticity. Therefore&s_comma; we hypothesized that ApLLP may be induced by a memory-related signal and participates in the synthesis of new RNA or protein required for long-term synaptic plasticity. We used the Aplysia culture system to examine the effect of depolarization on ApLLP and the ability of ApLLP to increase synaptic strength. Here&s_comma; we demonstrate that ApLLP&s_comma; a novel nucleolus protein is critically involved in both long-term facilitation (LTF) and behavioral sensitization. Membrane depolarization induced ApLLP expression&s_comma; which activated ApC/EBP expression through a direct binding to CRE. LTF was produced by a single pulse of 5-HT 30 min after the membrane depolarization. This LTF was blocked when either ApLLP or ApC/EBP were blocked by specific antibodies. In contrast&s_comma; ApLLP overexpression induced LTF in response to a single 5-HT treatment. Simultaneously&s_comma; a siphon noxious stimulus (SNS) to intact Aplysia induced ApLLP and ApC/EBP expression&s_comma; and single tail shock 30 min after SNS transformed short-term sensitization to long-term sensitization of siphon withdrawal reflex. These results suggest that ApLLP is an activity-dependent transcriptional activator that switches short-term facilitation to long-term facilitation.
Reference: Kim H et al. "A Nucleolar Protein ApLLP Induces ApC/EBP Expression Required for Long-Term Synaptic Facilitation in Aplysia Neurons." Neuron. 2006&s_comma; 49(5):707-718.