Plays a major role in tight junction-specific obliteration of the intercellular space, through calcium-independent cell-adhesion activity. Directly interacts with TJP1/ZO-1, TJP2/ZO-2 and TJP3/ZO-3 (PubMed:10601346). The phosphorylated form interacts with EPCAM (By similarity). Colocalizes with EPCAM at the basolateral cell membrane and tight junction. Expressed predominantly in lung and kidney. Phosphorylated. Belongs to the claudin family.