title: The function and dynamics of the apical scaffolding protein E3KARP are regulated by cell-cycle phosphorylation.
abstract: We examine the dynamics and function of the apical scaffolding protein E3KARP/NHERF2, which consists of two PDZ domains and a tail containing an ezrin-binding domain. The exchange rate of E3KARP is greatly enhanced during mitosis due to phosphorylation at Ser-303 in its tail region. Whereas E3KARP can substitute for the function of the closely related scaffolding protein EBP50/NHERF1 in the formation of interphase microvilli, E3KARP S303D cannot. Moreover, the S303D mutation enhances the in vivo dynamics of the E3KARP tail alone, whereas in vitro the interaction of E3KARP with active ezrin is unaffected by S303D, implicating another factor regulating dynamics in vivo. A-Raf is found to be required for S303 phosphorylation in mitotic cells. Regulation of the dynamics of EBP50 is known to be dependent on its tail region but modulated by PDZ domain occupancy, which is not the case for E3KARP. Of interest, in both cases, the mechanisms regulating dynamics involve the tails, which are the most diverged region of the paralogues and probably evolved independently after a gene duplication event that occurred early in vertebrate evolution.
authors: Department of Molecular Biology and Genetics, Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, NY 14853.
authors: Cécile
authors: C
authors: Sauvanet
authors: Department of Molecular Biology and Genetics, Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, NY 14853.
authors: Damien
authors: D
authors: Garbett
authors: Department of Molecular Biology and Genetics, Weill Institute for Molecular and Cell Biology, Cornell University, Ithaca, NY 14853 apb5@cornell.edu.
authors: Anthony
authors: A
authors: Bretscher
mesh_terms: D001665:Binding Sites; D018938:Caco-2 Cells; D018929:Cell Culture Techniques; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D006801:Humans; D013058:Mass Spectrometry; D008938:Mitosis / Q000502:physiology; D034521:Nuclear Matrix-Associated Proteins / Q000378:metabolism; D054731:PDZ Domains / Q000235:genetics; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D010802:Phylogeny; D011485:Protein Binding; D048491:Proto-Oncogene Proteins A-raf / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D000099149:Ezrin
chemical_list: D003598:Cytoskeletal Proteins; D034521:Nuclear Matrix-Associated Proteins; D010750:Phosphoproteins; D048491:Proto-Oncogene Proteins A-raf; D017923:Sodium-Hydrogen Exchangers; D000099149:Ezrin; C093376:sodium-hydrogen exchanger regulatory factor