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Interaction of Voltage-gated Sodium Channel Nav1.6 (SCN8A) with Microtubule-associated Protein Map1b*
9 auth. Janelle E. O’Brien, L. Sharkey, Christina N. Vallianatos, Chongyang Han, Julie C. Blossom, Ting Yu, ...
Background: Specific sodium channels have unique subcellular localizations within neurons. Results: We identified a novel interaction of sodium channel Nav1.6 with a microtubule-associated protein. Conclusion: Trafficking of Nav1.6 to the cell membr…
Background: Specific sodium channels have unique subcellular localizations within neurons. Results: We identified a novel interaction of sodium channel Nav1.6 with a microtubule-associated protein. Conclusion: Trafficking of Nav1.6 to the cell membrane is mediated by interaction with Map1b. Significance: Correct localization of sodium channels is essential to prevent neurological disorders such as epilepsy and ataxia. The mechanism by which voltage-gated sodium channels are trafficked to the surface of neurons is not well understood. Our previous work implicated the cytoplasmic N terminus of the sodium channel Nav1.6 in this process. We report that the N terminus plus the first transmembrane segment (residues 1–153) is sufficient to direct a reporter to the cell surface. To identify proteins that interact with the 117-residue N-terminal domain, we carried out a yeast two-hybrid screen of a mouse brain cDNA library. Three clones containing overlapping portions of the light chain of microtubule-associated protein Map1b (Mtap1b) were recovered from the screen. Interaction between endogenous Nav1.6 channels and Map1b in mouse brain was confirmed by co-immunoprecipitation. Map1b did not interact with the N terminus of the related channel Nav1.1. Alanine-scanning mutagenesis of the Nav1.6 N terminus demonstrated that residues 77–80 (VAVP) contribute to interaction with Map1b. Co-expression of Nav1.6 with Map1b in neuronal cell line ND7/23 resulted in a 50% increase in current density, demonstrating a functional role for this interaction. Mutation of the Map1b binding site of Nav1.6 prevented generation of sodium current in transfected cells. The data indicate that Map1b facilitates trafficking of Nav1.6 to the neuronal cell surface.
Published in
Journal of Biological Chemistry
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5
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5 | 2012 |
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