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. 2000 Feb 1;97(3):1032–1037. doi: 10.1073/pnas.97.3.1032

Figure 2.

Figure 2

Activation of MAPK triggers ligand-dependent PR down-regulation. (A) MEK inhibitors block ligand-induced PR down-regulation. T47D-YB cells were pretreated with vehicle (DMSO) or with PD98059 [PD (100 μM)] or SB202190 [SB190 (40 μM)] for 30 min before challenge with R5020 [10 nM (Upper)] or EGF [30 ng/ml (Lower)] for the indicated times. PR-B protein levels (Upper) and MAPK activity (Lower) were measured by immunoblotting with PR- or MAPK-phosphospecific antibodies, respectively. Total MAPK levels remained unchanged (data not shown). (B) Ligand-induced PR down-regulation requires activation of p42 and p44 MAPKs, but not p38 MAPK. T47D-YB cells were pretreated with vehicle (DMSO), SB202190 [SB190 (40 μM)], or SB203580 [SB580 (40 μM)] for 30 min before challenge with R5020 [10 nM (Upper)] or EGF [30 ng/ml (Lower)] for the indicated times. PR-B protein levels (Upper) were measured with specific antibodies, and p42/p44 and p38 MAPK activities (Lower) were measured with phosphospecific antisera for each kinase; 100 μg of protein was loaded per lane.