title: GEP100/BRAG2: activator of ADP-ribosylation factor 6 for regulation of cell adhesion and actin cytoskeleton via E-cadherin and alpha-catenin.
abstract: GEP(100) (p100) was identified as an ADP-ribosylation factor (ARF) guanine nucleotide-exchange protein (GEP) that partially colocalized with ARF6 in the cell periphery. p100 preferentially accelerated guanosine 5[gamma-thio]triphosphate (GTPgammaS) binding by ARF6, which participates in protein trafficking near the plasma membrane, including receptor recycling, cell adhesion, and cell migration. Here we report that yeast two-hybrid screening of a human fetal brain cDNA library using p100 as bait revealed specific interaction with alpha-catenin, which is known as a regulator of adherens junctions and actin cytoskeleton remodeling. Interaction of p100 with alpha-catenin was confirmed by coimmunoprecipitation of the endogenous proteins from human HepG2 or CaSki cells, although colocalization was difficult to demonstrate microscopically. alpha-Catenin enhanced GTPgammaS binding by ARF6 in vitro in the presence of p100. Depletion of p100 by small interfering RNA (siRNA) treatment in HepG2 cells resulted in E-cadherin content 3-fold that in control cells and blocked hepatocyte growth factor-induced redistribution of E-cadherin, consistent with a known role of ARF6 in this process. F-actin was markedly decreased in normal rat kidney (NRK) cells overexpressing wild-type p100, but not its GEP-inactive mutants, also consistent with the conclusion that p100 has an important role in the activation of ARF6 for its functions in both E-cadherin recycling and actin remodeling.
authors.affiliation: Pulmonary-Critical Care Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA. hiroit@nhlbi.nih.gov
authors.forename: Toyoko
authors.initials: T
authors.lastname: Hiroi
authors.forename: Akimasa
authors.initials: A
authors.lastname: Someya
authors.forename: Walter
authors.initials: W
authors.lastname: Thompson
authors.forename: Joel
authors.initials: J
authors.lastname: Moss
authors.forename: Martha
authors.initials: M
authors.lastname: Vaughan
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D022005:Adherens Junctions / Q000378:metabolism; D015820:Cadherins / Q000502:physiology*; D002448:Cell Adhesion / Q000502:physiology; D045744:Cell Line, Tumor; D003599:Cytoskeleton / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000502:physiology*; D006801:Humans; D051178:alpha Catenin / Q000502:physiology*
chemical_list: D000089982:ADP-Ribosylation Factor 6; D000199:Actins; D015820:Cadherins; D020662:Guanine Nucleotide Exchange Factors; C504483:IQSEC1 protein, human; D051178:alpha Catenin; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715349:Arf6 protein, rat