Figure 6.

Phosphatidylserine (PS) is involved in growth arrest-specific 6 (Gas6)-Axl activation after calcium-ionophore treatment. (A) hAxl/IFNγR1 cells that received no treatment (gray) or 10 µM calcium ionophore A23187 (green) at 37°C for 15 min were stained with FITC-Annexin V to assess PS externalization. (B) PGN632, a PS-targeting reagent, was added to hAxl/IFNγR1 reporter cells at two concentrations (0.1 and 0.2 mg/ml) for 20 min. The reporter cells were washed and stimulated by hGas6-CM subsequently. The activation of Axl receptor was assessed by pSTAT1 immunoblotting. Schematic illustration of this experiment is shown in the right panel. (C) hAxl/IFNγR1 reporter cells were first treated with calcium ionophore A23187 at concentrations of 1, 5, and 10 µM and then stimulated by hGas6-CM. The activation of Axl receptor was assessed by pSTAT1 immunoblotting. Schematic illustration of this experiment is shown in the right panel. The Western blotting results are representative results from at least three independent experiments.