title: Cis-dimerization mediates function of junctional adhesion molecule A.
abstract: Junctional adhesion molecule-A (JAM-A) is a transmembrane component of tight junctions that has been proposed to play a role in regulating epithelial cell adhesion and migration, yet mechanistic structure-function studies are lacking. Although biochemical and structural studies indicate that JAM-A forms cis-homodimers, the functional significance of dimerization is unclear. Here, we report the effects of cis-dimerization-defective JAM-A mutants on epithelial cell migration and adhesion. Overexpression of dimerization-defective JAM-A mutants in 293T cells inhibited cell spreading and migration across permeable filters. Similar inhibition was observed with using dimerization-blocking antibodies. Analyses of cells expressing the JAM-A dimerization-defective mutant proteins revealed diminished beta1 integrin protein but not mRNA levels. Further analyses of beta1 protein localization and expression after disruption of JAM-A dimerization suggested that internalization of beta1 integrin precedes degradation. A functional link between JAM-A and beta1 integrin was confirmed by restoration of cell migration to control levels after overexpression of beta1 integrin in JAM-A dimerization-defective cells. Last, we show that the functional effects of JAM dimerization require its carboxy-terminal postsynaptic density 95/disc-large/zonula occludins-1 binding motif. These results suggest that dimerization of JAM-A regulates cell migration and adhesion through indirect mechanisms involving posttranscriptional control of beta1 integrin levels.
authors.affiliation: Epithelial Pathobiology Research Unit, Department of Pathology, Emory University, Atlanta, GA 30322, USA.
authors.forename: Eric A
authors.initials: EA
authors.lastname: Severson
authors.forename: Liangyong
authors.initials: L
authors.lastname: Jiang
authors.forename: Andrei I
authors.initials: AI
authors.lastname: Ivanov
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Mandell
authors.forename: Asma
authors.initials: A
authors.lastname: Nusrat
authors.forename: Charles A
authors.initials: CA
authors.lastname: Parkos
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000737:chemistry* / Q000378:metabolism*; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D019281:Dimerization; D005353:Fibronectins / Q000494:pharmacology; D022001:Focal Adhesions / Q000187:drug effects / Q000378:metabolism; D005799:Genes, Dominant; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D062726:Junctional Adhesion Molecules; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D051419:Paxillin / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017434:Protein Structure, Tertiary; D014158:Transcription, Genetic / Q000187:drug effects; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000906:Antibodies; D015815:Cell Adhesion Molecules; D005353:Fibronectins; D019012:Integrin beta1; D062726:Junctional Adhesion Molecules; D051419:Paxillin; D020827:rap1 GTP-Binding Proteins