title: Role for actin filament turnover and a myosin II motor in cytoskeleton-driven disassembly of the epithelial apical junctional complex.
abstract: Disassembly of the epithelial apical junctional complex (AJC), composed of the tight junction (TJ) and adherens junction (AJ), is important for normal tissue remodeling and pathogen-induced disruption of epithelial barriers. Using a calcium depletion model in T84 epithelial cells, we previously found that disassembly of the AJC results in endocytosis of AJ/TJ proteins. In the present study, we investigated the role of the actin cytoskeleton in disassembly and internalization of the AJC. Calcium depletion induced reorganization of apical F-actin into contractile rings. Internalized AJ/TJ proteins colocalized with these rings. Both depolymerization and stabilization of F-actin inhibited ring formation and disassembly of the AJC, suggesting a role for actin filament turnover. Actin reorganization was accompanied by activation (dephosphorylation) of cofilin-1 and its translocation to the F-actin rings. In addition, Arp3 and cortactin colocalized with these rings. F-actin reorganization and disassembly of the AJC were blocked by blebbistatin, an inhibitor of nonmuscle myosin II. Myosin IIA was expressed in T84 cells and colocalized with F-actin rings. We conclude that disassembly of the AJC in calcium-depleted cells is driven by reorganization of apical F-actin. Mechanisms of such reorganization involve cofilin-1-dependent depolymerization and Arp2/3-assisted repolymerization of actin filaments as well as myosin IIA-mediated contraction.
authors.affiliation: Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia 30322, USA. aiivano@emory.edu
authors.forename: Andrei I
authors.initials: AI
authors.lastname: Ivanov
authors.forename: Ingrid C
authors.initials: IC
authors.lastname: McCall
authors.forename: Charles A
authors.initials: CA
authors.lastname: Parkos
authors.forename: Asma
authors.initials: A
authors.lastname: Nusrat
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D051339:Actin Depolymerizing Factors; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000378:metabolism; D022005:Adherens Junctions / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D002118:Calcium / Q000172:deficiency / Q000378:metabolism; D045744:Cell Line, Tumor; D016764:Cell Polarity; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000737:chemistry / Q000378:metabolism*; D051345:Destrin; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D008840:Microfilament Proteins / Q000378:metabolism; D020409:Molecular Motor Proteins / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000737:chemistry / Q000378:metabolism; D024507:Nonmuscle Myosin Type IIA / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019108:Tight Junctions / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: C495926:ACTR2 protein, human; C495928:ACTR3 protein, human; D051339:Actin Depolymerizing Factors; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; D003598:Cytoskeletal Proteins; D051345:Destrin; D008840:Microfilament Proteins; D020409:Molecular Motor Proteins; D046912:Multiprotein Complexes; D024507:Nonmuscle Myosin Type IIA; D002118:Calcium