Figure 6

PAI-1 enhancement of matrix assembly requires vitronectin. A – MG-63 cells were plated overnight on fibronectin- or vitronectin-coated wells in serum-free media. Cells were then pretreated with PAI-1 (1μg/ml) for 20 minutes in the presence of ¹²⁵I-fibronectin and 50 μM peptide was added for 6 hours. Cell layers were extracted in 1% DOC, and ¹²⁵I-fibronectin that was incorporated into the detergent-insoluble matrix was recovered by centrifugation and measured by gamma scintillation. Control levels (S25-treated cells) of fibronectin incorporation were set at 1 for each substrate. B – MG-63 cells were incubated overnight on wells coated with vitronectin or vitronectin fragment 40–459 in serum-free media. Cells were then pretreated with 1 μg/ml wild-type PAI-1 for 20 minutes in the presence of ¹²⁵I-fibronectin and 50 μM peptide was added for 6 hours. Cell layers were processed as described in A.