LDLRAP1 is a cytosolic protein that holds a phosphotyrosine binding (PTD) domain and performing as a cytosolic adaptor it couples LDLR to endocytic machinery. Mutations in LDLRAP1 are the reason for autosomal recessive hypercholesterolemia (ARH) which is a condition triggered by defective internalization of LDL receptors (LDLR) in the liver.