Fig. 11. GRIF1 knockdown inhibits EGF-induced EGFR degradation. (A) PC12 cells transfected with the indicated siRNAs or untransfected controls were incubated in the presence or absence of 100 ng/ml EGF for 1 hour at 37°C. Equal amounts of protein from whole cell lysates were analyzed by immunoblotting with antibodies against EGFR (top), GRIF1 (middle), or actin (bottom). (B) The degraded EGFR is expressed as a percentage of the EGFR level of the corresponding untreated cells. (C) PC12 cells transfected with the indicated siRNAs or untransfected controls were allowed to internalize ¹²⁵I-EGF for 10 minutes and then chased for 1 hour at 37°C. The degraded ¹²⁵I-EGF is expressed as a percentage of the initially internalized ¹²⁵I-EGF. Values are mean ± s.e.m. from three (C) or six (B) independent experiments. The asterisks indicate a statistically significant difference (P<0.05) from untransfected control cells.