Fig. 4.

PCSK9-promoted LDLR degradation. A–C: Effects of PCSK9 on LDLR expression. HEK293 cells transiently expressing the WT or mutant LDLR were incubated with DMEM in the presence or absence of different amount of PCSK9 (A, 8 μg; B, 6 μg; and C, 4 μg) as indicated at 37°C for 12 h. After washing, whole-cell lysate was prepared, and the same amount of total proteins was subjected to immunoblotting using 15A6 (PCSK9), HL-1 (LDLR), and a monoclonal anti-transferrin receptor (TFR). Similar results were obtained from at least one more experiment.