title: IQGAP1 controls tight junction formation through differential regulation of claudin recruitment.
abstract: IQGAP1 is a scaffolding protein previously implicated in adherens junction formation. However, its role in the establishment or maintenance of tight junctions (TJs) has not been explored. We hypothesized that IQGAP1 could regulate TJ formation by modulating the expression and/or localization of junctional proteins, and we systematically tested this hypothesis in the model Madin-Darby canine kidney (MDCK) cell line. We find that IQGAP1 silencing enhances a transient increase in transepithelial electrical resistance (TER) observed during the early stages of TJ formation (Cereijido et al., 1978). Quantitative microscopy and biochemical experiments suggest that this effect of IQGAP1 on TJ assembly is accounted for by reduced expression and TJ recruitment of claudin 2, and increased TJ recruitment of claudin 4. Furthermore, we show that IQGAP1 also regulates TJ formation through its interactor CDC42, because IQGAP1 knockdown increases the activity of the CDC42 effector JNK and dominant-negative CDC42 prevents the increase in TER caused by IQGAP1 silencing. Hence, we provide evidence that IQGAP1 modulates TJ formation by a twofold mechanism: (1) controlling the expression and recruitment of claudin 2 and recruitment of claudin 4 to the TJ, and (2) transient inhibition of the CDC42-JNK pathway.
authors.affiliation: Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medical College, New York, NY 10065, USA Barbara.tanos@icr.ac.uk Boulan@med.cornell.edu.
authors.forename: Barbara E
authors.initials: BE
authors.lastname: Tanos
authors.affiliation: Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medical College, New York, NY 10065, USA.
authors.forename: Andres E
authors.initials: AE
authors.lastname: Perez Bay
authors.affiliation: Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medical College, New York, NY 10065, USA.
authors.forename: Susana
authors.initials: S
authors.lastname: Salvarezza
authors.affiliation: Human Oncology & Pathogenesis Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
authors.forename: Igor
authors.initials: I
authors.lastname: Vivanco
authors.affiliation: Human Oncology & Pathogenesis Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065, USA Department of Neurology, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.
authors.forename: Ingo
authors.initials: I
authors.lastname: Mellinghoff
authors.affiliation: Department of Molecular Pharmacology, Physiology and Biotechnology, Division of Biology and Medicine, Alpert School of Medicine, Brown University, Providence, RI 02912, USA.
authors.forename: Mahasin
authors.initials: M
authors.lastname: Osman
authors.affiliation: Department of Laboratory Medicine, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: David B
authors.initials: DB
authors.lastname: Sacks
authors.affiliation: Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medical College, New York, NY 10065, USA Department of Cell and Developmental Biology, Weill Cornell Medical College, New York, NY 10065, USA Barbara.tanos@icr.ac.uk Boulan@med.cornell.edu.
authors.forename: Enrique
authors.initials: E
authors.lastname: Rodriguez-Boulan
mesh_terms: D000818:Animals; D062446:Claudin-2 / Q000235:genetics / Q000378:metabolism*; D062506:Claudin-4 / Q000235:genetics / Q000378:metabolism*; D004285:Dogs; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism; D061985:Madin Darby Canine Kidney Cells; D019108:Tight Junctions / Q000235:genetics / Q000378:metabolism*; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020703:ras GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D062446:Claudin-2; D062506:Claudin-4; C101203:IQ motif containing GTPase activating protein 1; D020703:ras GTPase-Activating Proteins; D048670:MAP Kinase Kinase 4; D020764:cdc42 GTP-Binding Protein
keywords: Claudin; IQGAP1; Paracellular permeability; Polarized epithelium; Tight junction