Intercellular junctions and cellular polarity: the PAR-aPKC complex, a conserved core cassette playing fundamental roles in cell polarity

Two PDZ-domain-containing adapter-like proteins, PAR-3 and PAR-6, and a pro tein kinase, atypical protein kinase C (PKC), cooperate together to establi sh cell polarity in a variety of biological contexts. These include asymmet ric cell division in early Caenorhabditis elegans embryo and Drosophila neu roblasts, as well as the establishment and maintenance of apical-basal pola rity in Drosophila and mammalian epithelial cells. Recent studies on the ro le of this PAR-aPKC complex in epithelia[ cell polarization provide new ins ights into the molecular basis of epithelial junctional formation and cell polarity.