title: A novel actin barbed-end-capping activity in EPS-8 regulates apical morphogenesis in intestinal cells of Caenorhabditis elegans.
abstract: Redundant gene function frequently hampers investigations of the physiological roles of mammalian proteins. This is the case for Eps8, a receptor tyrosine kinase (RTK) substrate that participates in the activation of the Rac-specific guanine nucleotide-exchange function of Sos1 (refs 2-5), thereby regulating actin remodelling by RTKs. EPS8-knockout mice, however, exhibit no evident phenotype, owing to the redundant function of three other EPS8-related genes. Here we show that in the nematode Caenorhabditis elegans, only one orthologue of the EPS8 gene exists, which gives rise to two alternatively spliced isoforms, EPS-8A and EPS-8B, differing at their carboxyl termini. In the nematode, eps-8 is essential for embryonic development. Furthermore, EPS-8A, but not EPS-8B, is specifically required for proper apical morphogenesis in the intestinal cells. This latter phenotype could be precisely correlated with a previously unknown actin barbed-end-capping activity, which is present in the C terminus of the EPS-8A isoform. Therefore, nematode genetics allowed not only the unmasking of distinct EPS-8-linked phenotypes, but also the definition of a novel function for this molecule in actin dynamics.
authors.affiliation: IFOM Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milan, Italy.
authors.forename: Assunta
authors.initials: A
authors.lastname: Croce
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Cassata
authors.forename: Andrea
authors.initials: A
authors.lastname: Disanza
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: Gagliani
authors.forename: Carlo
authors.initials: C
authors.lastname: Tacchetti
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Malabarba
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Carlier
authors.forename: Giorgio
authors.initials: G
authors.lastname: Scita
authors.forename: Ralf
authors.initials: R
authors.lastname: Baumeister
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Di Fiore
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D000199:Actins / Q000096:biosynthesis*; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D004847:Epithelial Cells / Q000378:metabolism / Q000648:ultrastructure; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000196:embryology* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008871:Microvilli / Q000378:metabolism / Q000648:ultrastructure; D008969:Molecular Sequence Data; D038081:Organogenesis / Q000502:physiology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000235:genetics; D011506:Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D018076:DNA, Complementary; C495310:EPS-8 protein, C elegans; C083430:Eps8 protein, mouse; D020033:Protein Isoforms; D011506:Proteins