3. Network of molecular constituents in the spine

Dendritic spines are the specialized structures on which majority of excitatory glutamatergic synapses in the brain have been found. They contain particularly high concentrations of actin, underscoring the likely importance of rapid formation as well as motility. Drebrin is an F-actin binding protein mainly located in neuron. In the adult cerebral cortex, drebrin is concentrated primarily in the dendritic spines. We have shown that drebrin is involved in spine morphology, synapse formation and synapse maintenance considerably. In the purpose of investigating drebrin function in the molecular basis, we have tried molecular cloning of a novel drebrin binding protein. In the course of yeast two-hybrid screen of a rat brain cDNA library using the N-terminal region of drebrin as bait, we isolated many positiveﾐinteracting clones. DNA sequence analysis of these clones revealed that about 70% of these clones were expressing an identical protein. We named this protein drebrin-associated-protein 1 (Drap1). We are now analyzing the physiological interaction between Drap1 and drebrin in the dendritic spines.