Figure 2.

SiRNA knockdown demonstrates a role for IQGAP1 in ceramide-induced ERK1/2 activation. (A) Aortic smooth muscle cells were treated with control, IQGAP1, or KSR1 siRNA. 5 days after transfection, cells were treated with ceramide (6 hours, 50 µg/ml). Additionally, cells were stimulated with FBS (10%) for 5 minutes before preparation of cell extracts. Cell lysates were analyzed for expression of IQGAP1, KSR1, phospho-ERK1/2 and total ERK1/2 using specific antibodies. GAPDH staining is shown as reference. Cropped gels are shown. (B) The statistical analysis of 5 independent experiments shows a significant decrease of relative ERK1/2 phosphorylation after knock down of IQGAP, but not KSR1. Statistical analysis of the degree of siRNA-induced knock down are shown in (C) for IQGAP1 and in (D) for KSR1.