Tight junctions (top) disassemble without Par-3 (middle) but are rescued by active cofilin (bottom).
Par-3 is one member of an apical polarity-inducing complex that also includes Par-6 and aPKC. The Par proteins are well-known for protein–protein interactions, but how these interactions lead to polarization is less clear. Using RNAi, Chen and Macara had previously shown that Par-3 helps assemble tight junctions (TJs) in epithelial cells by inhibiting an activator of Rac. The study now reveals a second function of Par-3 at TJs.
In the previous work, the authors saw that TJ formation required actin reorganization, so Chen looked for any effects of Par-3 on actin regulators. He now finds that cofilin, an actin filament severing protein, is phosphorylated and thus inactivated in the absence of...
