Opposite effects of tumor necrosis factor and soluble fibronectin on junctional adhesion molecule-A in endothelial cells

Abstract

Junctional adhesion molecule-A (JAM-A) regulates key inflammatory responses, such as edema formation and leukocyte transmigration. Although it has been reported that the inflammatory cytokine tumor necrosis factor (TNF) causes the disassembly of JAM-A from the intercellular junctions, the mechanism has not been elucidated fully. Here, we report that TNF enhances the solubility of JAM-A in Triton X-100 and increases the amount of Triton-soluble JAM-A dimers at the cell surface but does not change the total levels of cellular JAM-A. Thus we hypothesized that TNF causes the redistribution of JAM-A from the junctions to the cell surface and that junction disassembly is sufficient to account for JAM-A redistribution. Intriguingly, however, even after complete disassembly of the junctions (with EDTA and trypsin), higher levels of JAM-A are detectable at the cell surface (by FACS analysis) in cells that had been previously incubated in the presence of TNF than in its absence. Thus we propose that TNF causes not only the disassembly of JAM-A from the junctions and its subsequent redistribution to the cell surface but also its dispersal in such a way that JAM-A becomes more easily accessible to the antibodies used for FACS analysis. Finally, we evaluated whether soluble fibronectin might attenuate the effects of TNF on JAM-A, as some inflammatory conditions are associated with the depletion of plasma fibronectin. We found that fibronectin reduces the effect of TNF on the disassembly of JAM-A, but not on its dispersal, thus further stressing that disassembly and dispersal can be functionally dissociated.

Regulated release and functional modulation of junctional adhesion molecule A by disintegrin metalloproteinases

“…11,12 Cytokine stimulation was also associated with a translocation of JAM-A from Triton-insoluble to Triton-soluble microdomains. 34 However, as we demonstrate here, shedding by ADAM17 and ADAM10 is another important modality of JAM-A regulation. Increased JAM-A shedding leads to the downregulation of the molecule from vascular junctions and to its disappearance from Triton-insoluble microdomains, and inhibition of shedding prevents these effects.…”

“…34 We therefore questioned where JAM-A shedding would occur in endothelial cells. Western blot analysis revealed that JAM-A shedding was restricted to the Triton-insoluble fraction, as indicated by the absence of JAM-A in the respective extracts after cytokine stimulation and complete restoration of JAM-A in the presence of the ADAM17/10 inhibitor GW280264X ( Figure 6A).…”

Endothelial Junctional Adhesion Molecule-A Guides Monocytes Into Flow-Dependent Predilection Sites of Atherosclerosis

“…Previous work has addressed the redistribution of endothelial JAM-A, showing that JAM-A is relocalized to the apical surface in a cytokine-dependent manner under static or flow conditions in vitro. [15][16][17]34 We extend these findings by unveiling a focal upregulation and redistribution of JAM-A expression in endothelial cells of carotid arteries under atherogenic conditions of hyperlipidemia. The increased luminal JAM-A availability could mediate enhanced recruitment and higher content of macrophages and T-cells in atherosclerotic plaques of hyperlipidemic mice.…”

Dual Role of Melanoma Cell Adhesion Molecule (MCAM)/CD146 in Lymphocyte Endothelium Interaction: MCAM/CD146 Promotes Rolling via Microvilli Induction in Lymphocyte and Is an Endothelial Adhesion Receptor

“…In contrast, MCAM-l ϩ lymphocytes would roll and adhere to MCAM-l presented by the incompletely polarized endothelium, for instance, at inflammation sites. Indeed, treatment of HUVEC by proinflammatory cytokines TNF-␣ and IFN-␥ leads to redistribution of adhesion molecules such as JAM-A and PECAM-1 away from intercellular junctions (63)(64)(65).…”