Figure 4

LDLR and IR form a complex and LDL stimulates endocytosis of both receptors. (A) HUVECs were harvested and co-immunoprecipitation was performed with IR antibody or IgG (as negative control) prior to Western blot analysis, n = 3. (B) HUVECs were starved by culture in serum-free medium overnight then treated with LDL (50 μg/mL) for 5, 10 or 30 min. Cytoplasmic and membrane proteins were extracted and the expression of IR and LDLR analyzed by western blots. (C) HUVECs were starved by culture in serum-free medium overnight then treated with LDL (50 μg/mL) for 5 min. Cytoplasmic and membrane proteins were extracted and co-immunoprecipitation was performed with IR antibody, LDLR antibody or IgG (as negative control) prior to Western blot analysis, n = 3. Expression in Ctr group cells was assigned the value of 1, n = 3. ^*p < 0.05 versus Ctr. Data expressed as mean ± S.E.M.