Fig. 11. Colchicine-induction of PAI-1 expression is sensitive to PP1, puromycin and PD98059 and associated with ERK activation. Pretreatment of quiescent R22 cultures with PP1 significantly attenuated and completely ablated colchicine-mediated PAI-1 expression at 170 and 340 nM, respectively (A, left panel). PAI-1 induction was also effectively inhibited by exposure to puromycin (100 µg/ml) (A, right panel). Similarly, PD98059 at a final concentration of 10 µM reduced cellular PAI-1 levels by 65% whereas use of the inhibitor at 25 µM effectively blocked CD-induced PAI-1 synthesis (B). Exposure of quiescent R22 cells to colchicine-stimulated ERK1/2 phosphorylation by 30 minutes and ERK remained activated for at least 4 hours after addition of the drug (C). ERK phosphorylation, like PAI-1 induction, was PD98059 sensitive. In all cases, colchicine was used at 10 µM.