Involved in the establishment of cell polarity in mammalian epithelial cells (PubMed:12771187, PubMed:14718572, PubMed:23439680). Regulates the morphogenesis of tight junctions (PubMed:12771187, PubMed:14718572). 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). {ECO:0000250|UniProtKB:Q8QZT4, ECO:0000269|PubMed:12771187, ECO:0000269|PubMed:14718572, ECO:0000269|PubMed:23439680}. This is the function of CRB3 (crumbs cell polarity complex component 3, ENSG00000130545).