Fig. 3. PAK is necessary for Rac1-induced destabilization of E-cadherin complexes from junctions. (a, left panels) Rac1^Q61L was co-expressed with kinase-dead PAK1^K299R or with the auto-inhibitory domain Myc-PAK^AID. Seven hours post-injection, cells were fixed and immunostained for epitope tags and -catenin. (Right panels) As controls, Rac1^Q61L, PAK^K299R or Myc-tagged PAK^AID were microinjected alone and stained as above. Arrow indicates absence of -catenin. Arrowheads show the presence of -catenin at cell-cell contacts. Scale bars, 20 µm. (b) Effects of co-expression of constitutively active Rac1 and PAK mutants were quantified by measuring the ratio of the length in cadherin staining to the length of the cell-cell contact (corner to corner of neighbouring expressing cells). Controls were arbitrarily set as 100% (length in cadherin staining = length of the cell-cell contact). ^*P<0.05; ^**P<0.01. (c) Keratinocytes express PAK1 mRNA, but not PAK2 or PAK3 mRNAs. Keratinocyte and monocyte RNAs were subjected to RT-PCR using primers specific for members of the class I PAK family.