Expression of junctional adhesion molecule-A prevents spontaneous and random motility

Abstract

Junctional adhesion molecule-A (JAM-A) is a cell-surface glycoprotein that localizes to intercellular junctions and associates with intracellular proteins via PSD95-Dlg-ZO1-binding residues. To define the functional consequences of JAM-A expression, we have produced endothelial cells from JAM-A-deficient mice. We report here that the absence of JAM-A enhanced spontaneous and random motility. In turn, the enhanced motility of JAM-A-negative cells was abrogated either on transfection of exogenous JAM-A or on treatment with inhibitors of glycogen synthase kinase-3β (GSK-3β). In addition, in JAM-A-positive cells, motility was enhanced on inactivation of protein kinase Cζ (PKCζ), which is an inhibitor of GSK-3β. Although these findings suggested that JAM-A might inhibit GSK-3β, we found that expression per se of JAM-A did not change the levels of inactive GSK-3β. Thus, JAM-A expression may regulate effectors of motility that are also downstream of the PKCζ/GSK-3β axis. In support of this view, we found that JAM-A absence increased the number of actin-containing protrusions, reduced the stability of microtubules and impaired the formation of focal adhesions. Notably, all the functional consequences of JAM-A absence were reversed either on treatment with GSK-3β inhibitors or on transfection of full-length JAM-A, but not on transfection of a JAM-A deletion mutant devoid of the PSD95-Dlg-ZO1-binding residues. Thus, by regulating cytoskeletal and adhesive structures, JAM-A expression prevents cell motility, probably in a PSD95-Dlg-ZO1-dependent manner.

Junctional Adhesion Molecule A Interacts with Afadin and PDZ-GEF2 to Activate Rap1A, Regulate β1 Integrin Levels, and Enhance Cell Migration

“…We recently reported that in epithelial cells, JAM-A dimerization and the JAM-A PDZ binding motif are necessary for stabilization of ␤1 integrin and regulation of cell migration (Severson et al, 2008). These findings are consistent with those observed in endothelial cells where decreased cell migration in JAM-A-deficient endothelial cells was restored after transfection of cells with full-length JAM-A but not expression of JAM-A lacking the PDZ binding motif (Bazzoni et al, 2005). Furthermore, Naik et al (2003b) reported that overexpression of JAM-A increased cell migration in endothelial cells through ␣ v ␤ 3 integrin and activation of mitogen-activated protein kinase.…”

“…It has been reported previously that JAM-A regulates epithelial and endothelial cell migration (Naik et al, 2003a;Bazzoni et al, 2005;Severson et al, 2008). To confirm that JAM-A regulates cell migration in SKCO-15 cells, we evaluated the effect of decreased JAM-A protein levels on wound closure in a scratch wound assay.…”

“…In these cells, JAM-A has been reported to play a role in the regulation of epithelial barrier function (Mandell et al, 2005;Laukoetter et al, 2007), endothelial cell migration (Naik et al, 2003a;Bazzoni et al, 2005), angiogenesis (Naik et al, 2003a), platelet aggregation (Babinska et al, 2002), and leukocyte adhesion (Martin-Padura et al, 1998;Del Maschio et al, 1999). Recent reports suggest that JAM-A not only directly decreases paracellular permeability (Mandell et al, 2005;Laukoetter et al, 2007) but also promotes epithelial cell migration (Severson et al, 2008), which is critical for the maintenance of intestinal barrier in health and disease (Lacy, 1988;Fenteany et al, 2000).…”

Glycogen Synthase Kinase-3 (GSK3): Inflammation, Diseases, and Therapeutics

“…Localized inhibition of GSK3 also occurs in growth cones [6]. PKCζ-induced inhibition of GSK3 has also been shown to abolish random motility of endothelial cells [29]. These studies clearly document that local inhibition of GSK3 promotes migration.…”

Cis-Dimerization Mediates Function of Junctional Adhesion Molecule A

“…The cytoplasmic tail of JAM-A has been reported to associate, either directly or indirectly, with PDZ domain-containing proteins, such as zona occludens-1 (Bazzoni et al, 2000;Ebnet et al, 2000), AF-6/Afadin (Ebnet et al, 2000) and Par3/ASIP (Ebnet et al, 2001;Itoh et al, 2001), through characteristic hydrophobic residues (FLV) at the carboxy terminus. Evidence suggests that the cytoplasmic tail plays an important role in directing JAM-A localization to intercellular contacts (Ozaki et al, 2000), formation of tight junctions (Rehder et al, 2006), and transduction of intracellular signaling events (Bazzoni et al, 2005;Mandell et al, 2005;Naik and Naik, 2006). The extracellular domain of JAM-A can form homodimers through its N-terminal Ig loop (Prota et al, 2003).…”