title: Occludin localizes to centrosomes and modifies mitotic entry.
abstract: Proper control of cell cycle progression and barrier function are essential processes to the maintenance of epithelial cell homeostasis. The contribution of tight junction proteins to barrier function is well established, whereas their contribution to cell cycle control is only beginning to be understood. Centrosomes are the principal microtubule organizing centers in eukaryotic cells and centrosome duplication and separation are linked to the cell cycle and mitotic entry. Here we demonstrate that occludin localizes with centrosomes in Madin-Darby canine kidney cells. Immunocytochemistry and biochemical fractionation studies reveal occludin localizes with centrosomes during interphase and occludin Ser-490 phosphorylation at centrosomes increases with mitotic entry. Stable expression of aspartic acid phosphomimetic (S490D) results in centrosomal localization of occludin and increases cell numbers. Furthermore, we provide evidence that occludin regulates centrosome separation and mitotic entry as the nonphosphorylatable alanine mutation (S490A) impedes centrosome separation, delays mitotic entry, and reduces proliferation. Collectively, these studies demonstrate a novel location and function for occludin in centrosome separation and mitosis.
authors.affiliation: Departments of Cellular and Molecular Physiology, Hershey, Pennsylvania 17033.
authors.forename: E Aaron
authors.initials: EA
authors.lastname: Runkle
authors.affiliation: Ophthalmology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Sundstrom
authors.affiliation: Departments of Cellular and Molecular Physiology, Hershey, Pennsylvania 17033.
authors.forename: Kristin B
authors.initials: KB
authors.lastname: Runkle
authors.affiliation: University of Michigan Kellogg Eye Center, Ann Arbor, Michigan 48105.
authors.forename: Xuwen
authors.initials: X
authors.lastname: Liu
authors.affiliation: University of Michigan Kellogg Eye Center, Ann Arbor, Michigan 48105. Electronic address: dantonet@umich.edu.
authors.forename: David A
authors.initials: DA
authors.lastname: Antonetti
mesh_terms: D000409:Alanine / Q000737:chemistry; D000818:Animals; D019556:COS Cells; D018385:Centrosome / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D002522:Chlorocebus aethiops; D004285:Dogs; D005786:Gene Expression Regulation; D007150:Immunohistochemistry / Q000379:methods; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D008856:Microscopy, Fluorescence / Q000379:methods; D008938:Mitosis; D062793:Occludin; D010766:Phosphorylation; D012694:Serine / Q000737:chemistry; D013347:Subcellular Fractions; D014404:Tubulin / Q000737:chemistry
chemical_list: D008565:Membrane Proteins; D062793:Occludin; D014404:Tubulin; D012694:Serine; D000409:Alanine