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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.

SUBMITTER: Severson EA

PROVIDER: S-EPMC2366836 | biostudies-other | 2008 May

REPOSITORIES: biostudies-other

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Cis-dimerization mediates function of junctional adhesion molecule A.

Severson Eric A EA Jiang Liangyong L Ivanov Andrei I AI Mandell Kenneth J KJ Nusrat Asma A Parkos Charles A CA

Molecular biology of the cell 20080213 5

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. Overexpr ...[more]

PMID: 18272784

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Project description:Multiple sclerosis is a chronic neuroinflammatory disorder characterized by demyelination, oligodendrocyte damage/loss and neuroaxonal injury in the context of immune cell infiltration in the central nervous system. No neuroprotective therapy is available to promote the survival of oligodendrocytes and protect their myelin processes in immune-mediated demyelinating diseases. Pro-inflammatory CD4 T helper (Th)17 cells can directly interact with oligodendrocytes in multiple sclerosis and its animal model, causing injury to myelinating processes and cell death through direct contact. However, the molecular mechanisms underlying the close contact and subsequent detrimental interaction of Th17 cells with oligodendrocytes remain unclear. In this study we conducted single cell RNA sequencing of human primary oligodendrocytes cultured alone, in contact or separated by an insert with primary Th17 polarized T cells and identified several cell adhesion molecules that may modulate T cell contact mediated damage of oligodendrocytes. Furthermore, we used flow cytometry and immunofluorescence studies on central nervous system tissue from multiple sclerosis subjects, its animal model and controls to characterize the expression of cell adhesion molecules by mature oligodendrocytes. We found that a significant proportion of human and murine mature oligodendrocytes express melanoma cell adhesion molecule and activated leukocyte cell adhesion molecule in multiple sclerosis, EAE and controls although their regulation differ between human and mouse. We observed that exposure to pro-inflammatory cytokines or to human activated T cells are associated with a marked downregulation of the expression of melanoma cell adhesion molecule but not activated leukocyte cell adhesion molecule at the surface of human primary oligodendrocytes. Furthermore, we used in vitro live-imaging, immunofluorescence, and flow cytometry to determine the contribution of these molecules to Th17-polarized cell adhesion and cytotoxicity towards human oligodendrocytes. Silencing and blocking activated leukocyte cell adhesion molecule but not melanoma cell adhesion molecule limited prolonged interactions between oligodendrocytes and Th17-polarized cells, resulting in decreased adhesion of Th17-polarized cells to oligodendrocytes and conferred significant protection of oligodendrocytic processes.

Dataset Information

Cis-dimerization mediates function of junctional adhesion molecule A.

Publications

Cis-dimerization mediates function of junctional adhesion molecule A.

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