Fig. 2. Rac1b activation does not affect E-cadherin localization at junctions. (a) The constitutively active Rac1b mutant (Rac1b^Q61L) was expressed for up to 18 hours and stained with Myc-tagged and E-cadherin. Arrow indicates absence of E-cadherin staining; arrowheads show concentration of E-cadherin at cell-cell contact sites. (b) Quantification of the ratio of cadherin staining over junction length after an 8-hour expression of activated Rac1b, Rac1 and Rac3 (see Materials and Methods for details). Values are expressed as the percentage of the total number of junctions found in expressing cells. (c) Rac1b protein is not degraded after microinjection in keratinocytes. Active forms of Rac1 and Rac1b were expressed for 6 hours and detected using anti-Myc antibody (recognizes only exogenous Rac) or an anti-Rac monoclonal antibody [recognizes an epitope in both exogenous and endogenous Rac1 and Rac1b (total Rac)]. Junctions were visualized with -catenin staining. Asterisks show cells with low expression of Rac1^Q61L in which disruption of cell-cell contacts was achieved. (d) Keratinocytes were transfected with activated forms of Rac1, Rac1b and Rac3. Protein lysates were obtained and probed with antibodies against Rac1, Rac1b, Rac3, Myc and actin; arrows indicate endogenous Rac. Scale bars, 20 µm.