Fig. 5. Phosphomimetic paxillin inhibits the formation of long stress fibers and fibronectin fibrillogenesis. Cells expressing wild-type or mutant YFP-paxillin were grown for 48 hours and then fixed and stained for F-actin (A) and fibronectin (B). In cells expressing the phosphomimetic mutant (Y2E) there is a conspicuous absence of long actin stress fibers, whereas they are overly abundant in the non-phosphorylatable mutant (Y2F) (A). Similarly, fibronectin fibrillogenesis is impaired in Y2E, and enhanced in Y2F (B). (C) The extent of fibronectin fibrillogenesis was quantified by measuring the average intensity of fibronectin per cell (n=10). Means ± s.d. are shown. Bar, 5 µm.