Fig. 4.

Effects of GRK2 knockdown on FLS function and EP4 receptor signaling. a, b Verification of effective sequence of siRNA for FLS GRK2 gene silencing (GRK2-rat-796: GRK2 siRNA 1, GRK2-rat-673: GRK2 siRNA 2, GRK2-rat-585: GRK2 siRNA 3). c Effects of GRK2 knockdown on FLS proliferation. **P < 0.01 vs. control ($\overline{x}$ ± s, n = 3). d, e The change in the EP4 receptor on the cell membrane in response to the EP4 receptor agonist treatment in FLSs transfected with GRK2 siRNA 1 was detected by flow cytometry. *P < 0.05, **P < 0.01 vs. control ($\overline{x}$ ± s, n = 3). f The level of cAMP in GRK2 silencing FLSs stimulated by an EP4 receptor agonist ($\overline{x}$ ± s, n = 3)