Involved in the establishment of cell polarity in mammalian epithelial cells (By similarity). Regulates the morphogenesis of tight junctions (PubMed:21145499). 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 (PubMed:21145499). Component of a complex composed of CRB3, PALS1 and PATJ (By similarity). Interacts (via C-terminus) with PALS1 (via PDZ domain) (PubMed:12527193). 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. Expressed in the apical renal tubules (at protein level) (PubMed:17920587). Expressed in the retinal pigment epithelium (PubMed:26404741). Expressed in the branchial arches, optic vesicle and mesonephric tubules of the kidney at 10.5 dpc (PubMed:17920587). Expressed in the internal endodermal layer and in the nascent bronchial tips of the lung at 11.5 dpc (PubMed:17920587). The PDZ-binding motif is involved in the interactions with PARD6A and PALS1.