title: The RapGEF PDZ-GEF2 is required for maturation of cell-cell junctions.
abstract: The small G-protein Rap1 is a critical regulator of cell-cell contacts and is activated by the remodeling of adherens junctions. Here we identify the Rap1 guanine nucleotide exchange factor PDZ-GEF2 as an upstream activator of Rap1 required for the maturation of adherens junctions in the lung carcinoma cells A549. Knockdown of PDZ-GEF2 results in the persistence of adhesion zippers at cell-cell contacts. Activation of Rap1A rescues junction maturation in absence of PDZ-GEF2, demonstrating that Rap1A is downstream of PDZ-GEF2 in this process. Moreover, depletion of Rap1A, but not Rap1B, impairs adherens junction maturation. siRNA for PDZ-GEF2 also lowers the levels of E-cadherin, an effect that can be mimicked by Rap1B, but not Rap1A siRNA. Since junctions in Rap1B depleted cells have a mature appearance, these data suggest that PDZ-GEF2 activates Rap1A and Rap1B to perform different functions. Our results present the first direct evidence that PDZ-GEF2 plays a critical role in the maturation of adherens junctions.
authors.affiliation: Department of Physiological Chemistry, Centre for Biomedical Genetics and Cancer Genomics Centre, Utrecht, The Netherlands.
authors.forename: Nadia
authors.initials: N
authors.lastname: Dubé
authors.forename: Matthijs R H
authors.initials: MR
authors.lastname: Kooistra
authors.forename: Willem-Jan
authors.initials: WJ
authors.lastname: Pannekoek
authors.forename: Marjolein J
authors.initials: MJ
authors.lastname: Vliem
authors.forename: Viola
authors.initials: V
authors.lastname: Oorschot
authors.forename: Judith
authors.initials: J
authors.lastname: Klumperman
authors.forename: Holger
authors.initials: H
authors.lastname: Rehmann
authors.forename: Johannes L
authors.initials: JL
authors.lastname: Bos
mesh_terms: D022005:Adherens Junctions / Q000378:metabolism* / Q000648:ultrastructure; D015820:Cadherins / Q000378:metabolism; D002448:Cell Adhesion; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism / Q000648:ultrastructure; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D020668:rap GTP-Binding Proteins / Q000378:metabolism; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D015820:Cadherins; D020662:Guanine Nucleotide Exchange Factors; C430803:RAP1A protein, human; C116122:RAPGEF3 protein, human; C485746:RAPGEF6 protein, human; C116753:RAP1B protein, human; D020668:rap GTP-Binding Proteins; D020827:rap1 GTP-Binding Proteins