title: Mammalian diaphanous-related formin Dia1 controls the organization of E-cadherin-mediated cell-cell junctions.
abstract: The formin-homology protein Dia1 is a target of RhoA and a potent activator of nucleation and elongation of actin filaments. Here, we demonstrate that short-hairpin (sh) RNA-mediated downregulation of Dia1 in human MCF7 epithelial cells disrupts adherens junctions, as manifested by the significantly decreased localization of E-cadherin and associated proteins to cell-cell contacts. Expression of mouse Dia1, which is insensitive to the human Dia1-specific shRNA, rescued the junctional integrity. Coexpression of GFP-tagged Dia1 and a constitutively active RhoA mutant, RhoA-V14, resulted in localization of the exogenous GFP-Dia1 to the cell-cell junctions. This localization was accompanied by a strong increase in the width of the adhesion zone and augmentation of the actin, E-cadherin and beta-catenin content of the junctions. A constitutively active Dia1 mutant lacking the N-terminal portion was unable to localize to cell-cell junctions and did not show any junction-strengthening effect. The adherens junction enhancement induced by Dia1 and active RhoA did not require microtubules, but depended on the activity of myosin II. Inhibition of myosin II activity abolished the Dia1-mediated reinforcement of cell-cell junctions and instead induced the formation of numerous actin-rich filopodia at the contact zone. Thus, Dia1 localizes to and controls cadherin-mediated junctions in a RhoA-dependent manner.
authors.affiliation: Department of Molecular Cell Biology, The Weizmann Institute of Science, PO Box 26, Rehovot 76100, Israel.
authors.forename: Letizia
authors.initials: L
authors.lastname: Carramusa
authors.forename: Christoph
authors.initials: C
authors.lastname: Ballestrem
authors.forename: Yuliya
authors.initials: Y
authors.lastname: Zilberman
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Bershadsky
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D022005:Adherens Junctions / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D001483:Base Sequence; D015820:Cadherins / Q000235:genetics / Q000378:metabolism*; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D000080865:Formins; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D051178:alpha Catenin / Q000235:genetics / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015820:Cadherins; D015815:Cell Adhesion Molecules; C108962:DIAPH1 protein, human; D000080865:Formins; D008840:Microfilament Proteins; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D051178:alpha Catenin; D051176:beta Catenin; D000098662:Vasodilator-Stimulated Phosphoprotein; D019000:Phosphotyrosine; D020742:rhoA GTP-Binding Protein