title: Scaffolding protein GOPC regulates tight junction structure.
abstract: GOPC (FIG/PIST/CAL) is a PDZ-domain scaffolding protein that regulates the trafficking of a wide array of proteins, including small GTPases, receptors and cell surface molecules such as cadherin 23 and cystic fibrosis transmembrane regulator. In Madin-Darby canine kidney (MDCK) cells, we find that GOPC localizes to the trans-Golgi network (TGN) but not to the cis- or trans-Golgi cisternae. Colocalization occurs with the early endosome Rab GTPase Rab5 and a TGN/endosome marker Rab14 but not with Rab11, a marker of recycling endosomes. No localization of GOPC was detected to the lateral membranes or tight junctions. Knockdown of GOPC in MDCK cells results in decreased transepithelial resistance and increased paracellular flux. This might be attributable to the compromised trafficking of tight junction components from the TGN, as GOPC-knockdown cells have decreased lateral labeling of the tight junction protein claudin-1 and decreased protein levels of claudin-2. GOPC might mediate the trafficking of newly synthesized tight junction proteins from the TGN to the cell surface or the recycling of these proteins from specialized endosomal compartments.
authors.affiliation: Department of Cellular and Molecular Medicine, University of Arizona, PO Box 245044, Tucson, AZ 85724, USA.
authors.forename: Ruifeng
authors.initials: R
authors.lastname: Lu
authors.forename: Lorraine
authors.initials: L
authors.lastname: Stewart
authors.forename: Jean M
authors.initials: JM
authors.lastname: Wilson
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004285:Dogs; D011992:Endosomes / Q000235:genetics / Q000378:metabolism; D061985:Madin Darby Canine Kidney Cells; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D019108:Tight Junctions / Q000235:genetics / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D021601:trans-Golgi Network / Q000235:genetics / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D008565:Membrane Proteins; D020696:rab5 GTP-Binding Proteins