Adapter protein involved in asymmetrical cell division and cell polarization processes. Seems to play a central role in the formation of epithelial tight junctions. Targets the phosphatase PTEN to cell junctions By similarity. Association with PARD6B may prevent the interaction of PARD3 with F11R/JAM1, thereby preventing tight junction assembly. The PARD6-PARD3 complex links GTP-bound Rho small GTPases to atypical protein kinase C proteins. Required for establishment of neuronal polarity and normal axon formation in cultured hippocampal neurons.Joberty G., Nat. Cell Biol. 2:531-539(2000).Fang C.M., Cell Res. 11:223-229(2001).Kohjima M., Biochem. Biophys. Res. Commun. 299:641-646(2002).