Fig. 7. Incubation with water-soluble cholesterol decreases tyrosine phosphorylation of the EGFR. A431 cells and HEp-2 cells were pre-incubated with (+) or without (-) 0.4 mg/ml water-soluble cholesterol for 30 minutes at 37°C, cooled with ice-cold PBS, and further incubated with 10 nM EGF in the absence or presence of cholesterol for 15 minutes on ice. Blotting with antibody to PY1173 revealed a large decrease in EGFR phosphorylation in cells incubated with water-soluble cholesterol. However, blotting with antibody to EGFR showed equal amounts of EGFR in cell lysates irrespective of addition of cholesterol.