title: The MAL protein is crucial for proper membrane condensation at the ciliary base, which is required for primary cilium elongation.
abstract: The base of the primary cilium contains a zone of condensed membranes whose importance is not known. Here, we have studied the involvement of MAL, a tetraspanning protein that exclusively partitions into condensed membrane fractions, in the condensation of membranes at the ciliary base and investigated the importance of these membranes in primary cilium formation. We show that MAL accumulates at the ciliary base of epithelial MDCK cells. Knockdown of MAL expression resulted in a drastic reduction in the condensation of membranes at the ciliary base, the percentage of ciliated cells and the length of the cilia, but did not affect the docking of the centrosome to the plasma membrane or produce missorting of proteins to the pericentriolar zone or to the membrane of the remaining cilia. Rab8 (for which there are two isoforms, Rab8A and Rab8b), IFT88 and IFT20, which are important components of the machinery of ciliary growth, were recruited normally to the ciliary base of MAL-knockdown cells but were unable to elongate the primary cilium correctly. MAL, therefore, is crucial for the proper condensation of membranes at the ciliary base, which is required for efficient primary cilium extension.
authors.affiliation: Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Reales
authors.affiliation: Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: Bernabé-Rubio
authors.affiliation: Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Casares-Arias
authors.affiliation: Departament de Biologia Cel·lular, Immunologia i Neurociències, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Barcelona 08036, Spain.
authors.forename: Carles
authors.initials: C
authors.lastname: Rentero
authors.affiliation: Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain.
authors.forename: Jaime
authors.initials: J
authors.lastname: Fernández-Barrera
authors.affiliation: Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Rangel
authors.affiliation: Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain.
authors.forename: Isabel
authors.initials: I
authors.lastname: Correas
authors.affiliation: Departament de Biologia Cel·lular, Immunologia i Neurociències, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, Barcelona 08036, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Enrich
authors.affiliation: Electron Microscopy Unit, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain.
authors.forename: Germán
authors.initials: G
authors.lastname: Andrés
authors.affiliation: Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas and Universidad Autónoma de Madrid, Cantoblanco, Madrid 28049, Spain maalonso@cbm.csic.es.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Alonso
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000502:physiology*; D002478:Cells, Cultured; D018385:Centrosome / Q000502:physiology*; D002923:Cilia / Q000502:physiology* / Q000648:ultrastructure*; D004285:Dogs; D005455:Fluorescent Antibody Technique; D006801:Humans; D061985:Madin Darby Canine Kidney Cells; D008854:Microscopy, Electron; D009024:Morphogenesis; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C569026:MAL protein, human; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D020691:rab GTP-Binding Proteins
keywords: Centrosome; Condensed membranes; MAL; Primary ciliogenesis