Fig. 5. S1P induces activation of Src kinase. Serum-starved confluent monolayers were treated with S1P (0.5 µM) or thrombin (10 nM) for the indicated times and an immunoprecipitation kinase assay was performed using anti-Src family kinase antibody (cst-1) as described in Materials and Methods. Src autophosphorylation is shown in the upper panel. Equal loading was verified by blotting aliquots of supernatants from each sample with cst-1.