Neuronal Calcium Sensor 1 and Activity-Dependent Facilitation of P/Q-Type Calcium Currents at Presynaptic Nerve Terminals

Abstract

P/Q-type presynaptic calcium currents ( I pCa ) undergo activity-dependent facilitation during repetitive activation at the calyx of the Held synapse. We investigated whether neuronal calcium sensor 1 (NCS-1) may underlie this phenomenon. Direct loading of NCS-1 into the nerve terminal mimicked activity-dependent I pCa facilitation by accelerating the activation time of I pCa in a Ca 2+ -dependent manner. A presynaptically loaded carboxyl-terminal peptide of NCS-1 abolished I pCa facilitation. These results suggest that residual Ca 2+ activates endogenous NCS-1, thereby facilitating I pCa . Because both P/Q-type Ca 2+ channels and NCS-1 are widely expressed in mammalian nerve terminals, NCS-1 may contribute to the activity-dependent synaptic facilitation at many synapses.