title: Structural requirements for interaction of sodium channel beta 1 subunits with ankyrin.
abstract: Sodium channel beta subunits modulate channel kinetic properties and cell surface expression levels and function as cell adhesion molecules. beta 1 and beta 2 participate in homophilic cell adhesion resulting in ankyrin recruitment to cell contact sites. We hypothesized that a tyrosine residue in the cytoplasmic domain of beta 1 may be important for ankyrin recruitment and tested our hypothesis using beta 1 mutants replacing Tyr(181) with alanine (beta 1Y181A), phenylalanine (beta 1Y181F), or glutamate (beta 1Y181E), or a truncated construct deleting all residues beyond Tyr(181) (beta 1L182(STOP)). Ankyrin recruitment was observed in beta 1L182(STOP), showing that residues Ile(166)-Tyr(181) contain the major ankyrin recruiting activity of beta 1. Ankyrin recruitment was abolished in beta 1Y181E, suggesting that tyrosine phosphorylation of beta 1 may inhibit beta 1-ankyrin interactions. Ankyrin(G) and beta 1 associate in rat brain membranes and in transfected cells expressing beta 1 and ankyrin(G) in the absence of sodium channel alpha subunits. beta 1 subunits are recognized by anti-phosphotyrosine antibodies following treatment of these cell lines with fibroblast growth factor. beta 1 and ankryin(G) association is not detectable in cells following treatment with fibroblast growth factor. Ankyrin(G) and beta 1Y181E do not associate even in the absence of fibroblast growth factor treatment. beta 1 subunit-mediated cell adhesion and ankyrin recruitment may contribute to sodium channel placement at nodes of Ranvier. The phosphorylation state of beta 1Y181 may be a critical regulatory step in these developmental processes.
authors: Department of Pharmacology, the University of Michigan, Ann Arbor, Michigan 48109, USA.
authors: Jyoti D
authors: JD
authors: Malhotra
authors: Matthew C
authors: MC
authors: Koopmann
authors: Kristin A
authors: KA
authors: Kazen-Gillespie
authors: Nicholas
authors: N
authors: Fettman
authors: Michael
authors: M
authors: Hortsch
authors: Lori L
authors: LL
authors: Isom
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017487:Ankyrins / Q000378:metabolism*; D002448:Cell Adhesion; D006224:Cricetinae; D003412:Cricetulus; D004330:Drosophila; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011487:Protein Conformation; D011817:Rabbits; D015222:Sodium Channels / Q000737:chemistry / Q000502:physiology*; D013329:Structure-Activity Relationship; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism
chemical_list: D017487:Ankyrins; D015222:Sodium Channels; D014443:Tyrosine