Interaction of Junctional Adhesion Molecule with the Tight Junction Components ZO-1, Cingulin, and Occludin

TLDR

Junctional adhesion molecule (JAM) is known to colocalize with tight junction proteins occludin, ZO‑1, and cingulin, yet direct evidence of these associations had been lacking. In CHO cells, JAM expression—alone or with occludin—promoted junctional recruitment of endogenous ZO‑1 and cotransfected occludin, and co‑precipitation studies in Caco‑2 cells showed JAM associates with ZO‑1 via a PDZ‑binding motif and with cingulin via its amino‑terminal globular head. These results demonstrate that JAM is a component of the tight junction multiprotein complex and may facilitate junction assembly.

Abstract

Junctional adhesion molecule (JAM) is an integral membrane protein that has been reported to colocalize with the tight junction molecules occludin, ZO-1, and cingulin. However, evidence for the association of JAM with these molecules is missing. Transfection of Chinese hamster ovary cells with JAM (either alone or in combination with occludin) resulted in enhanced junctional localization of both endogenous ZO-1 and cotransfected occludin. Additionally, JAM was coprecipitated with ZO-1 in the detergent-insoluble fraction of Caco-2 epithelial cells. A putative PDZ-binding motif at the cytoplasmic carboxyl terminus of JAM was required for mediating the interaction of JAM with ZO-1, as assessed by <i>in vitro</i> binding and coprecipitation experiments. JAM was also coprecipitated with cingulin, another cytoplasmic component of tight junctions, and this association required the amino-terminal globular head of cingulin. Taken together, these data indicate that JAM is a component of the multiprotein complex of tight junctions, which may facilitate junction assembly.