Component of the epithelial apical junction complex that is essential for the tight junction integrity. Proposed to function as a homophilic cell adhesion molecule. Recruits MPDZ to intercellular contact sites. Probably involved in transepithelial migration of polymorphonuclear leukocytes (PMN) through adhesive interactions with AMICA1/JAML located in the plasma membrane of PMN.

Expressed in pancreas, brain, heart, small intestine, testis, prostate and at a lower level in liver and lung. Isoform 5 is ubiquitously expressed. Isoform 3 is expressed in heart, lung and pancreas. In skeletal muscle, isoform 1 is found at the neuromuscular junction and isoform 2 is found in blood vessels. In cardiac muscle, isoform 1 and isoform 2 are found at intercalated disks. In heart expressed in subendothelial layers of the vessel wall but not in the luminal endothelial surface. Expression is elevated in hearts with dilated cardiomyopathy.

Contains 2 Ig-like C2-type (immunoglobulin-like) domains.

The Ig-like C2-type 1 domain probably mediates homodimerization and interaction with JAML.
The PDZ-binding motif mediates interaction with MPDZ and BAIAP1.

N-glycosylated.
Palmitoylated on Cys-259 and/or Cys-260; required for proper localization to the plasma membrane.

Secreted and Cell membrane. Cell junction > tight junction. Cell junction > adherens junction. Basolateral cell membrane. In epithelial cells localizes to the apical junction complex composced of tight and adherens junctions. In airway epithelial cells localized to basolateral membrane but not to apical surface.