The role of MAP1A light chain 2 in synaptic surface retention of Ca V2.2 channels in hippocampal neurons

Abstract

Cav2.2 channels are localized at nerve terminals where they play a critical role in neurotransmission. However, the determinant that controls surface retention of these channels has not been identified. Here, we report that presynaptic surface localization of Cav2.2 is mediated through its interaction with light chain 2 (LC2) of microtubule-associated protein MAP1A. Deletion of a 23-residue binding domain within the Cav2.2 C terminus resulted in reduced synaptic distribution of the mutant channels. Using an antibody generated against an extracellular epitope of Cav2.2, we demonstrate that interfering the interaction with LC2 reduced surface expression of endogenous Cav2.2 at presynaptic boutons. In addition, the disruption of LC2-Cav2.2 coupling reduced Ca2+-influx into nerve terminals through Cav2.2 and impaired activity-dependent FM4-64 uptake. The treatments of neurons with Latrunculin A to disrupt actin filaments resulted in reduced density of surface Cav2.2-positive boutons. Furthermore, LC2NT, a LC2 truncated mutant lacking the actin-binding domain, could not rescue Cav2.2 surface expression after suppressing LC2 expression with RNAi. Because actin filaments are major cytomatric components at the presynaptic boutons, these observations suggest a mechanism by which LC2 provides anchoring of surface Cav2.2 to the actin cytoskeleton, thus contributing to presynaptic function. Copyright © 2008 Society for Neuroscience.