Involved in the establishment of cell polarity in mammalian epithelial cells (By similarity). Regulates the morphogenesis of tight junctions (By similarity). Involved in promoting phosphorylation and cytoplasmic retention of transcriptional coactivators YAP1 and WWTR1/TAZ which leads to suppression of TGFB1-dependent transcription of target genes such as CCN2/CTGF, SERPINE1/PAI1, SNAI1/SNAIL1 and SMAD7 (By similarity). Component of a complex composed of CRB3, PALS1 and PATJ (PubMed:12527193). Interacts (via C-terminus) with PALS1 (via PDZ domain) (By similarity). Interacts with PARD6A (By similarity). Interacts (via intracellular domain) with EPB41L5 (By similarity). Localizes primarily to the apical membrane with a small fraction in the upper part of tight junctions of epithelial cells. The PDZ-binding motif is involved in the interactions with PARD6A and PALS1.