Abstract
Amphiphysin I, a member of the BAR (Bin-Amphiphysin-Rvsp) protein super family, plays a key role in clathrin-mediated endocytosis of synaptic vesicles. Amphiphysin I mediates invagination and fission of synaptic vesicles in cooperation with Dynamin. We have shown that the function of Amphiphysin I is regulated by Cdk5- and calcineurin-dependent phosphorylation and dephosphorylation. Cdk5-dependent phosphorylation of the protein inhibits the association with the binding proteins such as β-adaptin. In the present study, we found that Amphiphysin I was cleaved to three fragments by treatment with high KCl (80 mM) in the mouse hippocampus slices. The cleavages were inhibited by treatment with ALLM, a potent calpain inhibitor. The high K+ stimulation also induced the cleavage of α-spectrin, a physiological substrate of calpain. Treatment with FK506, a potent calcineurin inhibitor, increased the extent of the KCl-induced cleavages of Amphiphysin I in the hippocampal slices. In contrast, treatment with roscovitine, a Cdk5 inhibitor, inhibited the cleavages. These results suggest that Amphiphysin I may be a substrate of calpain in presynaptic terminals and the cleavages may be regulated by the phosphorylation states. And the calpain-induced cleavages of Amphiphysin might be an important step to prevent neuron from abnormal excitement caused by high K stimulus. [Jpn J Physiol 55 Suppl:S148 (2005)]
