Studies on the mechanism of signal transduction of Arc, a gene involved in synaptic plasticity

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To define the changes in gene expression that may underlie long-lasting behavioral effects by cocaine and methamphetamine, drug-induced immediate early gene Arc has been characterized and proteins are screened the two-hybrid library to identify interacting partners of Arc in our laboratory. I found a novel SH3 protein, SH3P13 bound to Arc in vivo. SH3P13 consists of twoalternative splicing products 13L and 13S, and binds to dynamin that is involved in endocytotic machinery. immunohistochemistry of primary hippocampal neurons showed that both dynamin and SH3P13 proteins were expressed in neurons and co-localized at synapses. Furthermore, immunoelectron microscopy reveal that SH3P13 was localized to postsynaptic spines. It activated the GTPase of dynamin, which is known to regulate dopamine receptor-mediated endocytosis. Therefore, we examined whether overexpression of SH3P13 in COS-7 cells regulates dynamin-dependent internalization of dopamine D2 receptor. Unexpectedly, coexpression of SH3P13 almost completely inhibited sequestration of D2 receptor after dopamine stimulation. These results suggest that SH3P13 negatively regulates dopamine receptor mediated-endocytosis by competing with endogenous dynamin-binding protein(s) in COS-7 cells. Arc protein induced by cocaine or methamphetamine might regulate dynamin-dependent internalization of dopamine receptor via binding to SH3P13. The study of the regulation of SH3P13 on the dopamine-dependent endocytosis by Arc may provide an insight into physiological function of SH3P13 and Arc protein.