EGF-induced ERM phosphorylation is ErbB1 dependent. A) HeLa cells were pretreated with DMSO, erlotinib (100 nM), ErbB2 inhibitor (10 μM), or lapatinib (10 μM) for 1 h prior to treatment with EGF (10 ng/ml) or S1P (100 nM) for 5 min. pERM, phosphorylated EGFR (p-EGFR), and phosphorylated ErbB2 (p-ErbB2) levels were then assessed by immunoblotting. B) HeLa cells were treated with AStar, EGFR, or ErbB2 siRNA for 48 h. Cells were then starved for 4 h prior to treatment with EGF (10 ng/ml) for 5 min. pERM, total EGFR, and total ErbB2 levels were then assessed by immunoblotting.