title: The tails of apical scaffolding proteins EBP50 and E3KARP regulate their localization and dynamics.
abstract: The closely related apical scaffolding proteins ERM-binding phosphoprotein of 50 kDa (EBP50) and NHE3 kinase A regulatory protein (E3KARP) both consist of two postsynaptic density 95/disks large/zona occludens-1 (PDZ) domains and a tail ending in an ezrin-binding domain. Scaffolding proteins are thought to provide stable linkages between components of multiprotein complexes, yet in several types of epithelial cells, EBP50, but not E3KARP, shows rapid exchange from microvilli compared with its binding partners. The difference in dynamics is determined by the proteins' tail regions. Exchange rates of EBP50 and E3KARP correlated strongly with their abilities to precipitate ezrin in vivo. The EBP50 tail alone is highly dynamic, but in the context of the full-length protein, the dynamics is lost when the PDZ domains are unable to bind ligand. Proteomic analysis of the effects of EBP50 dynamics on binding-partner preferences identified a novel PDZ1 binding partner, the I-BAR protein insulin receptor substrate p53 (IRSp53). Additionally, the tails promote different microvillar localizations for EBP50 and E3KARP, which localized along the full length and to the base of microvilli, respectively. Thus the tails define the localization and dynamics of these scaffolding proteins, and the high dynamics of EBP50 is regulated by the occupancy of its PDZ domains.
authors.affiliation: Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853.
authors.forename: Damien
authors.initials: D
authors.lastname: Garbett
authors.forename: Cécile
authors.initials: C
authors.lastname: Sauvanet
authors.forename: Raghuvir
authors.initials: R
authors.lastname: Viswanatha
authors.forename: Anthony
authors.initials: A
authors.lastname: Bretscher
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D018938:Caco-2 Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D008871:Microvilli / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D009154:Mutation; D054731:PDZ Domains / Q000235:genetics; D010750:Phosphoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D059008:Time-Lapse Imaging / Q000379:methods; D000099149:Ezrin
chemical_list: D003598:Cytoskeletal Proteins; D049452:Green Fluorescent Proteins; D010750:Phosphoproteins; D017923:Sodium-Hydrogen Exchangers; D000099149:Ezrin; C093376:sodium-hydrogen exchanger regulatory factor