Fig. 2.

Conserved proteins in eukaryotic cell polarity. The PAR proteins are conserved regulators of polarity across cell types in eukaryotic organisms. After fertilization, the C. elegans embryo becomes asymmetrical with different PAR proteins localizing to either the anterior or posterior end (a). Polarization along an apical–basal axis in epithelial cells is also regulated by the mutual exclusion of PAR3–PAR6–aPKC complex and DLG–LGL–SCRIB complex. While the PAR3–PAR6–aPKC and the CRB–PALS–PATJ complex localizes to the apical region, the DLG–LGL–SCRIB complex localizes to the basolateral region of the polarized cell (b). This is accomplished by interactions between members of the three complexes and phosphorylation. aPKC has been reported to phosphorylate Crb, Par6, Par3, and Lgl (b). Known protein–protein interactions including domains involved are listed in (c)