Adapter protein (clathrin-associated sorting protein (CLASP)) required for efficient endocytosis of the LDL receptor (LDLR). Also involved in the vitellogenin receptor mediated endocytosis of nutrients during oogenesis. Interacts (via PID domain) with ldlr (via NPXY motif) (PubMed:12591597). Binds to soluble clathrin trimers and to the adapter protein complex 2 (AP-2, beta 2 subunit). Binds to phosphoinositides, which regulate clathrin bud assembly at the cell surface. Interacts with the VLDL receptor (vldlr) (By similarity). Interacts with the vitellogenin receptor (PubMed:12591597). Expressed at high level during oogenesis and embryogenesis. Found at low level in the adult liver and spleen. Found at very low level in testis and heart. Not found in the oocyte vegetal cortex. Expressed throughout oogenesis. Homogeneously distributed in stages I and II oocytes and only later localized primarily to the vegetal cortex. Expressed in early stage embryos, but expression decreases during gastrulation, reaching barely detectable levels by tailbud stages. 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.