Fig. 7. Cell proliferation mediated by P2Y₁R stimulation involves EGFR transactivation, PKC, Src and metalloprotease activity. (A) Induction of cell proliferation mediated by P2Y₁R stimulation requires EGFR activation. The EGFR tyrosine kinase blocker AG1478 inhibits the proliferation of FRT cells induced by either 1 µM 2-MeSADP or 10 nM EGF in a concentration-dependent manner (n=4). (B) HeLa cells pre-incubated for 30 minutes in the absence or presence of 1 µM of MRS2179 (P2Y₁R antagonist), Ro 318220 (non-selective PKC inhibitor), PP2 (Src kinase inhibitor), AG1478 (blocker of EGFR tyrosine-kinase activity) or Ilomastat (metalloprotease inhibitor), were then stimulated with 1 µM 2-MeSADP for 1 hour in the presence of each inhibitor. Results are normalized against control cells incubated only with the agonist. Values are the means ± s.e.m. ^*P<0.05, ^**P<0.01; Dunnett's test compared with control (n=3-6). (C) ERK1/2 activation in response to P2Y₁R agonist depends on EGFR activity. The EGFR tyrosine kinase blocker AG1478 (100 nM) completely abrogates ERK1/2 activation induced by 2-MeSADP (10 nM, 5 minutes), in FRT and HeLa cells. The immunoblot is representative of three independent experiments.