Adapter protein (clathrin-associated sorting protein (CLASP)) required for efficient endocytosis of the LDL receptor (LDLR) in polarized cells such as hepatocytes and lymphocytes, but not in non-polarized cells (fibroblasts). May be required for LDL binding and internalization but not for receptor clustering in coated pits. May facilitate the endocytosis of LDLR and LDLR-LDL complexes from coated pits by stabilizing the interaction between the receptor and the structural components of the pits. May also be involved in the internalization of other LDLR family members. Binds to phosphoinositides, which regulate clathrin bud assembly at the cell surface. Required for trafficking of LRP2 to the endocytic recycling compartment which is necessary for LRP2 proteolysis, releasing a tail fragment which translocates to the nucleus and mediates transcriptional repression (By similarity). Interacts (via PID domain) with LDLR (via NPXY motif). Binds to soluble clathrin trimers. Interacts with AP2B1; the interaction mediates the association with the AP-2 complex (By similarity). Interacts with VLDLR (PubMed:12746448). Interacts with LRP2 (By similarity). The [DE]-X(1,2)-F-X-X-[FL]-X-X-X-R motif mediates interaction the AP-2 complex subunit AP2B1. The PID domain mediates interaction with the NPXY internalization motif of LDLR. Mice are extremely sensitive to cholesterol intake. LDLR are expressed at normal levels, but are sequestered at the hepatocyte surface. LDL internalization defect is caused by the inability of the LDLR to enter the endocytic cycle. Truncated N-terminus.