Fig. 7. Visualization of LDL uptake and receptor distribution when LDL is continuously present. In contrast to ldlA(LDLR), LDL uptake by ldlA(LDLR_H562Y), ldlA(LDLR_H562N) and ldlA(LDLR_1-292LpR_343-850) transfectants is reduced and receptors are not prominently localized to the ERC after prolonged LDL incubation. Transfectants were preincubated for 90 minutes in growth medium with unlabelled LDL, followed by a 15-minute pulse with OG-LDL; the receptor was stained for IF using anti-LDLR antibody C7. Whereas OG-LDL uptake by wt LDLR (A) is not visibly affected upon LDL preincubation, and ligand (left, grey) and receptor (middle, grey) do not colocalize (right – ligand, green; receptor, red; colocalization, yellow), OG-LDL endocytosis by ldlA(LDLR_1-292LpR_343-850) (B), ldlA(LDLR_H562N) (C) and ldlA(LDLR_H562Y) transfectants (D) is decreased, and the receptors are not prominently concentrated in the ERC. (E) LDLR_H562Y appears scattered throughout the cell interior after a 105-minute incubation with unlabelled LDL, reducing receptor visibility to some extent (middle, grey). The receptor distribution is similar to that of the lysosomal marker (left, grey; right – LysoTracker, blue; receptor, red; colocalization, magenta). Scale bar, 10 µm (E, right).