title: Interaction of voltage-gated sodium channel Nav1.6 (SCN8A) with microtubule-associated protein Map1b.
abstract: 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 Na(v)1.6 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 Na(v)1.6 channels and Map1b in mouse brain was confirmed by co-immunoprecipitation. Map1b did not interact with the N terminus of the related channel Na(v)1.1. Alanine-scanning mutagenesis of the Na(v)1.6 N terminus demonstrated that residues 77-80 (VAVP) contribute to interaction with Map1b. Co-expression of Na(v)1.6 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 Na(v)1.6 prevented generation of sodium current in transfected cells. The data indicate that Map1b facilitates trafficking of Na(v)1.6 to the neuronal cell surface.
authors.affiliation: Department of Human Genetics, the University of Michigan, Ann Arbor, Michigan 48109-5618, USA.
authors.forename: Janelle E
authors.initials: JE
authors.lastname: O'Brien
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Sharkey
authors.forename: Christina N
authors.initials: CN
authors.lastname: Vallianatos
authors.forename: Chongyang
authors.initials: C
authors.lastname: Han
authors.forename: Julie C
authors.initials: JC
authors.lastname: Blossom
authors.forename: Ting
authors.initials: T
authors.lastname: Yu
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Waxman
authors.forename: Sulayman D
authors.initials: SD
authors.lastname: Dib-Hajj
authors.forename: Miriam H
authors.initials: MH
authors.lastname: Meisler
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D007150:Immunohistochemistry; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D062557:NAV1.6 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D015222:Sodium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D008869:Microtubule-Associated Proteins; D062557:NAV1.6 Voltage-Gated Sodium Channel; D009419:Nerve Tissue Proteins; C491046:Scn8a protein, mouse; D015222:Sodium Channels; C085284:microtubule-associated protein 1B