title: Junctional adhesion molecule A interacts with Afadin and PDZ-GEF2 to activate Rap1A, regulate beta1 integrin levels, and enhance cell migration.
abstract: Junctional adhesion molecule-A (JAM-A) is a transmembrane tight junction protein that has been shown to regulate barrier function and cell migration through incompletely understood mechanisms. We have previously demonstrated that JAM-A regulates cell migration by dimerization of the membrane-distal immunoglobulin-like loop and a C-terminal postsynaptic density 95/disc-large/zona occludens (PDZ) binding motif. Disruption of dimerization resulted in decreased epithelial cell migration secondary to diminished levels of beta1 integrin and active Rap1. Here, we report that JAM-A is physically and functionally associated with the PDZ domain-containing molecules Afadin and PDZ-guanine nucleotide exchange factor (GEF) 2, but not zonula occludens (ZO)-1, in epithelial cells, and these interactions mediate outside-in signaling events. Both Afadin and PDZ-GEF2 colocalized and coimmunoprecipitated with JAM-A. Furthermore, association of PDZ-GEF2 with Afadin was dependent on the expression of JAM-A. Loss of JAM-A, Afadin, or PDZ-GEF2, but not ZO-1 or PDZ-GEF1, similarly decreased cellular levels of activated Rap1, beta1 integrin protein, and epithelial cell migration. The functional effects observed were secondary to decreased levels of Rap1A because knockdown of Rap1A, but not Rap1B, resulted in decreased beta1 integrin levels and reduced cell migration. These findings suggest that JAM-A dimerization facilitates formation of a complex with Afadin and PDZ-GEF2 that activates Rap1A, which regulates beta1 integrin levels and cell migration.
authors.affiliation: Epithelial Pathobiology Research Unit, Department of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Severson
authors.forename: Winston Y
authors.initials: WY
authors.lastname: Lee
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Capaldo
authors.forename: Asma
authors.initials: A
authors.lastname: Nusrat
authors.forename: Charles A
authors.initials: CA
authors.lastname: Parkos
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement; D015536:Down-Regulation; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000166:cytology* / Q000201:enzymology; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D007136:Immunoglobulins / Q000378:metabolism*; D019012:Integrin beta1 / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D011485:Protein Binding; D011956:Receptors, Cell Surface; D015398:Signal Transduction; D062826:Zonula Occludens-1 Protein; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D015815:Cell Adhesion Molecules; C407243:F11R protein, human; D020662:Guanine Nucleotide Exchange Factors; D007136:Immunoglobulins; D019012:Integrin beta1; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; C430803:RAP1A protein, human; C403525:RAPGEF2 protein, human; C485746:RAPGEF6 protein, human; D011956:Receptors, Cell Surface; C569042:TJP1 protein, human; C569043:Tjp1 protein, mouse; D062826:Zonula Occludens-1 Protein; C108835:afadin; D020827:rap1 GTP-Binding Proteins