The down-regulation (top) of Rac1 activity (colored) at cell contact sites is lost if Fak is inhibited (bottom).
Although most cells travel in isolation, some epithelial cell types migrate as a sheet, as during gastrulation or in carcinoma metastasis. Yano et al. find that HeLa cells (derived from a carcinoma) need the focal adhesion proteins Fak and paxillin to maintain their N-cadherin–based cell contacts.
When integrins at focal adhesions bind to the matrix, paxillin joins the complex. The new results suggest that paxillin recruits Fak to focal adhesions. Then, activated Fak somehow down-regulates only the Rac1 at sites of cell contact, although the direct Fak substrates are not yet known. When either paxillin or Fak was inhibited, the resulting Rac1 activity caused...
