Figure 4. Knockdown of β-arrestin 2 protein levels allows for transinhibition of HER1.

5637 or HeLa cells were transfected with control siRNA or β-arrestin 2 siRNA, prestimulated for 1 minute with 200 ng/mL CXCL12 and subsequently stimulated with 25 ng/mL HB-EGF for 2, 4, 5, 7, 10 or 15 minutes. In knockdown cells either Y1068 or Y1173 phosphorylation was inhibited as opposed to non-silenced cells at each time observed, as determined by ELISA (p<0.05). This shows that CXCL12 signaling transinhibits HER1 phosphorylation via G-protein-pathways in the absence of β-arrestin 2 activation and further supports that [N33A]CXCL12, which strongly transhinibits HER1, is a G-protein-biased ligand. The means ±SD out of 4 experiments are shown.