N‐type Ca2+ channel regulation by the light chain 1 (LC1) of the microtubule associated protein B (MAP1B)

Abstract

MAP1B is a protein complex consisting of heavy and light (LC) chains that play an important role in regulating neuronal morphogenesis and function. Recent studies have shown that LC1 interacts with NMDA and HT5 receptors at the postsynapsis regulating their trafficking and surface expression. However, much less is known regarding its role at the presynaptic level where voltage‐gated N‐type Ca2+ channels couple membrane depolarization to neurotransmitter release. Here, using a strategy that combines electrophysiology with biochemical and molecular biology techniques, we investigated whether LC1 interacts with the N‐type channel and whether this interaction has any physiological significance. Hence, using confocal immunofluorescence, co‐localization of these proteins was revealed in hippocampal cells from neonatal mouse, and their interaction was confirmed by pulldown assays using whole brain homogenates. Likewise, heterologous expression of recombinant N‐type channels and LC1 in HEK‐293 cells revealed a significant decrease in whole cell current density without apparent changes in current kinetics, suggesting a diminished number of functional channels in the cell surface. Furthermore, pulldown experiments as well as confocal microscopy showed an interaction between LC1 and the channel in the heterologous system. These results reveal a functional coupling between LC1 and the N‐type channel.This work was supported by Conacyt‐Conicyt binational cooperation program.