title: Involvement of nectin in the localization of IQGAP1 at the cell-cell adhesion sites through the actin cytoskeleton in Madin-Darby canine kidney cells.
abstract: IQGAP1, a putative downstream target of the Rho family small G proteins, Cdc42 and Rac, localizes at adherens junctions (AJs) in epithelial cells. It has been suggested that IQGAP1 localizes at AJs through its binding to beta-catenin, and negatively regulates the E-cadherin-mediated cell-cell adhesion. Nectin is a Ca(2+)-independent, immunoglobulin-like cell-cell adhesion molecule that localizes at AJs. Nectin is associated with E-cadherin through their respective cytoplasmic tail-binding proteins, afadin and catenins, and involved in the formation of AJs cooperatively with E-cadherin. Here we investigated a role of nectin in the localization of IQGAP1 at AJs. Ca(2+) chelation from the medium causes disruption of the E-cadherin-mediated cell-cell adhesion, but not the nectin-based cell-cell adhesion, in Madin-Darby canine kidney (MDCK) cells. IQGAP1 remained at the residual nectin-based cell-cell adhesion sites where the E-cadherin immunofluorescence signal disappeared. Restoration of Ca(2+) in the medium causes re-accumulation of E-cadherin to the residual nectin-based cell-cell adhesion sites to re-form AJs. Nectin inhibitors inhibit this re-accumulation of E-cadherin to re-form AJs by impairing the nectin-based cell-cell adhesion. The nectin inhibitors also reduced the localization of IQGAP1 at the cell-cell adhesion sites. When MDCK cells were incubated with microbeads coated with the extracellular fragment of nectin that interacts with cellular nectin, IQGAP1 also accumulated at the bead-MDCK cell contact sites. The accumulation of IQGAP1 at the cell-cell adhesion sites was inhibited by actin filament-disrupting agents, latrunculin A and cytochalasin D. These results indicate that nectin is involved in the localization of IQGAP1 at AJs through the actin cytoskeleton.
authors.affiliation: Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine/Faculty of Medicine, Suita, Japan.
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Katata
authors.forename: Kenji
authors.initials: K
authors.lastname: Irie
authors.forename: Atsunori
authors.initials: A
authors.lastname: Fukuhara
authors.forename: Tomomi
authors.initials: T
authors.lastname: Kawakatsu
authors.forename: Akio
authors.initials: A
authors.lastname: Yamada
authors.forename: Kazuya
authors.initials: K
authors.lastname: Shimizu
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Takai
mesh_terms: D000199:Actins; D022005:Adherens Junctions / Q000378:metabolism; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D015820:Cadherins / Q000502:physiology; D002352:Carrier Proteins / Q000032:analysis*; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000494:pharmacology*; D002478:Cells, Cultured; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism; D004285:Dogs; D007668:Kidney; D000075983:Nectins; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D020703:ras GTPase-Activating Proteins
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D015820:Cadherins; D002352:Carrier Proteins; D015815:Cell Adhesion Molecules; C101203:IQ motif containing GTPase activating protein 1; D000075983:Nectins; D013844:Thiazoles; D053778:Thiazolidines; D020703:ras GTPase-Activating Proteins; D015638:Cytochalasin D; C037067:latrunculin A