Binds LDL, the major cholesterol-carrying lipoprotein of plasma, and transports it into cells by endocytosis. In order to be internalized, the receptor-ligand complexes must first cluster into clathrin-coated pits. Interacts (via NPXY motif) with DAB2 (via PID domain); the interaction is impaired by tyrosine phosphorylation of the NPXY motif. Interacts (via NPXY motif) with LDLRAP1 (via PID domain). Interacts with ARRB1. Interacts with SNX17. Interacts with the full-length immature form of PCSK9 (via C-terminus). Rapidly endocytosed upon ligand binding. The NPXY motif mediates the interaction with the clathrin adapter DAB2 and with LDLRAP1 which are involved in receptor internalization. A few residues outside the motif also play a role in the interaction. N- and O-glycosylated. Ubiquitinated by MYLIP leading to degradation. Defects in LDLR are the cause of familial hypercholesterolemia (FH). Belongs to the LDLR family.