Cousin, MichaelMalladi, ChandraTan, TimothyRaymond, ClarkeSmillie, KarenRobinson, Phillip J2015-12-130021-9258http://hdl.handle.net/1885/78344Maintaining synaptic transmission requires replenishment of docked synaptic vesicles within the readily releasable pool (RRP) from synaptic vesicle clusters in the synapsin-bound reserve pool. We show that synapsin forms a complex with phosphatidylinositol 3-kinase (PI 3-kinase) in intact nerve terminals and that synapsin-associated kinase activity increases on depolarization. Disruption of either PI 3-kinase activity or its interaction with synapsin inhibited replenishment of the RRP, but did not affect exocytosis from the RRP. Thus we conclude that a synapsin-associated PI 3-kinase activity plays a role in synaptic vesicle delivery to the RRP. This also suggests that PI 3-kinase contributes to the maintenance of synaptic transmission during periods of high activity, indicating a possible role in synaptic plasticity.Keywords: Biochemistry; Complexation; Cytology; Neurology; Synapsin; Proteins; phosphatidylinositol 3 kinase; synapsin I; animal tissue; article; complex formation; depolarization; enzyme activity; exocytosis; nerve cell plasticity; nerve conduction; nerve ending;200310.1074/jbc.M3023862002015-12-11