The Journal of Neuroscience, October 29, 2008, 28(44):11333-11346; doi:10.1523/JNEUROSCI.3078-08.2008
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Cellular/Molecular
The Role of MAP1A Light Chain 2 in Synaptic Surface Retention of CaV2.2 Channels in Hippocampal Neurons
A. G. Miriam Leenders,1
Lin Lin,2
Li-Dong Huang,2
Claudia Gerwin,1
Pei-Hua Lu,2 and
Zu-Hang Sheng1
1Synaptic Function Section, The Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke–National Institutes of Health, Bethesda, Maryland 20892-3701, and 2Department of Neurobiology, Shanghai Jiao-Tong University School of Medicine, Shanghai 200025, China
Correspondence should be addressed to Zu-Hang Sheng, Synaptic Function Section, the Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke–National Institutes of Health, Building 35, Room 3B203, 35 Convent Drive, Bethesda, MD 20892-3701. Email: shengz{at}ninds.nih.gov
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.
Key words: calcium channels; presynaptic; surface expression; synaptic; axonal transport; microtubule; presynaptic regulation; actin
Received July 2, 2008;
revised Sept. 8, 2008;
accepted Sept. 22, 2008.
Correspondence should be addressed to Zu-Hang Sheng, Synaptic Function Section, the Porter Neuroscience Research Center, National Institute of Neurological Disorders and Stroke–National Institutes of Health, Building 35, Room 3B203, 35 Convent Drive, Bethesda, MD 20892-3701. Email: shengz{at}ninds.nih.gov
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