title: Differential roles for actin polymerization and a myosin II motor in assembly of the epithelial apical junctional complex.
abstract: Differentiation and polarization of epithelial cells depends on the formation of the apical junctional complex (AJC), which is composed of the tight junction (TJ) and the adherens junction (AJ). In this study, we investigated mechanisms of actin reorganization that drive the establishment of AJC. Using a calcium switch model, we observed that formation of the AJC in T84 intestinal epithelial cells began with the assembly of adherens-like junctions followed by the formation of TJs. Early adherens-like junctions and TJs readily incorporated exogenous G-actin and were disassembled by latrunculin B, thus indicating dependence on continuous actin polymerization. Both adherens-like junctions and TJs were enriched in actin-related protein 3 and neuronal Wiskott-Aldrich syndrome protein (N-WASP), and their assembly was prevented by the N-WASP inhibitor wiskostatin. In contrast, the formation of TJs, but not adherens-like junctions, was accompanied by recruitment of myosin II and was blocked by inhibition of myosin II with blebbistatin. In addition, blebbistatin inhibited the ability of epithelial cells to establish a columnar phenotype with proper apico-basal polarity. These findings suggest that actin polymerization directly mediates recruitment and maintenance of AJ/TJ proteins at intercellular contacts, whereas myosin II regulates cell polarization and correct positioning of the AJC within the plasma membrane.
authors.affiliation: Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA 30322, USA. aiivano@emory.edu
authors.forename: Andrei I
authors.initials: AI
authors.lastname: Ivanov
authors.forename: Dirk
authors.initials: D
authors.lastname: Hunt
authors.forename: Markus
authors.initials: M
authors.lastname: Utech
authors.forename: Asma
authors.initials: A
authors.lastname: Nusrat
authors.forename: Charles A
authors.initials: CA
authors.lastname: Parkos
mesh_terms: D000199:Actins / Q000378:metabolism*; D022005:Adherens Junctions / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology; D002460:Cell Line; D016764:Cell Polarity / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology; D008871:Microvilli / Q000187:drug effects / Q000648:ultrastructure; D008954:Models, Biological; D020409:Molecular Motor Proteins / Q000378:metabolism*; D024462:Myosin Type II / Q000378:metabolism*; D011108:Polymers; D011412:Propanolamines / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D019108:Tight Junctions / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002227:Carbazoles; D006576:Heterocyclic Compounds, 4 or More Rings; D020409:Molecular Motor Proteins; D011108:Polymers; D011412:Propanolamines; D013844:Thiazoles; D053778:Thiazolidines; C489942:wiskostatin; C472645:blebbistatin; D024462:Myosin Type II; C037068:latrunculin B