The N-type Ca channel, along with the P/Q-type, plays a central role in chemical synaptic transmissions in the nervous system. As these Ca2+ channels determine the amount, timing and location of Ca2+ influx at nerve terminals, changes in Ca2+ channel biophysical properties, especially their inactivation kinetics, can profoundly affect the temporal dynamics of evoked neurotransmitter release. Despite recent advances, there are still major gaps in our understanding of molecular mechanism for Ca2+ channel inactivation, as well as their regulations by signally proteins in neurons. This proposal seeks to understand the cellular and molecular mechanisms of regulation of N-type Ca2+ channels by 14-3-3 proteins, a family of brain-rich proteins that participate in multiple cellular processes. In our preliminary studies, we not only discovered and characterized the novel protein-protein interaction between the N-type Ca2+ channel and 14-3-3, but also determined a profound modulation of inactivation properties of N-type Ca2+ channels by 14-3-3. Furthermore, we revealed a significant change in short-term synaptic plasticity by antagonizing 14-3-3 binding in the presynaptic neuron. In this application, we will build on these findings and further investigate the function and mechanism of this regulatory complex using a combination of molecular, biochemical and electrophysiological techniques. Our specific aims are: (1) Determine the mechanism underlying 14-3-3-dependent modulation of N-type Ca2+ channel inactivation. Specifically, we will investigate whether 14-3-3 modulates inactivation properties of N-type Ca2+ channels through its binding to the channel. (2) Determine the mechanism underlying 14-3-3- dependent modulation of short-term synaptic plasticity. Specifically, we will investigate whether 14-3-3 regulates short-term plasticity by modulating N-type Ca2+ channel inactivation. (3) Determine dynamic interactions between 14-3-3 and N-type Ca2+ channels in neurons. Specifically, we will investigate whether formation of this protein complex is promoted by recurring presynaptic activity, via enhancing CaMKII-dependent phosphorylation of the N-type Ca2+ channel. Together, these studies will provide a novel mechanism for regulation of N-type Ca2+ channels and help to understand 14-3-3's functions in the nervous system.