Figure 7
From: Membrane estrogen receptor-α levels predict estrogen-induced ERK1/2 activation in MCF-7 cells
Time course of extracellular signal-regulated kinase (ERK)1/2 activation with 17β-estradiol (E2) and impeded ligand in membrane estrogen receptor (mER)-α-enriched (mERhigh) and mER-α-depleted (mERlow) MCF-7 cells, and receptor-less cells. After 72 hours in medium with dextran-coated charcoal-stripped serum (DCSS), cells were treated with 1 pmol/l E2, or an equivalent concentration of hormone contained in an E2-peroxidase conjugate, for different time intervals. (a, b) mERhigh MCF-7 cells treated with E2 and E2-peroxidase, respectively. (c) mERlow MCF-7 cells treated with E2. (d) Estrogen receptor-α-negative MDA-MB-231 cells treated with E2. Each experiment was repeated at least three times, each time point represents 16 replicate wells, and the values are expressed as mean ± standard error. Insets: inhibition of ERK1/2 activation with U0126 upstream mitogen-activated protein kinase kinase (MEK)1/2 inhibitor. The cells were pretreated for 15 min with 40 μmol/l inhibitor (gray bars) and E2-induced activation of ERK1/2 was tested at activation times appropriate for each cell type (after 3, 6 and 10 min in the case of mERhigh or 6 min in the case of mERlow cells). The asterisks indicate the significant reduction in ERK1/2 activation compared with cells treated only with E2 (black bars).