AT1R–EGFR transactivation is reduced when cells are transfected with siRNAs targeting AT1R, Gq/11 and EGFR expression. Cells were transfected with Dharmacon siGENOME SMARTpool siRNAs targeting the ectopically expressed AT1R (siAgtr1a), Gq/11 (GNAQ, siGNAQ) or EGFR (siEGFR) mRNA transcripts. (A,B) Cells transfected with siAgtr1a demonstrated mRNA knockdown of ∼80% at 24 hours (A), and the AT1R–EGFR transactivation at 72 hour knockdown was abolished (B) (n = 3 experiments; ***P = 0.0009, paired two-tailed Student's t-test). (C,D) Transfection with siGNAQ resulted in over an 85% knockdown of GNAQ mRNA at 24 hours (C), and a reduction in EGFR and ERK1/2 phosphorylation post-AngII stimulation (72 hour knockdown; D) (n = 3 experiments; ***P = 0.0002, paired two-tailed Student's t-test). (E,F) Similarly, when cells were transfected with siEGFR, ∼75% knockdown of EGFR mRNA was observed at 24 hours post-transfection (E) and the AT1R–EGFR transactivation response was blunted at 72 hours (F) (n = 3 experiments; ***P = 0.0004, paired two-tailed Student's t-test). Western blot is representative of all of the experiments carried out (n = 3).