AMN (amnion associated transmembrane protein) is a membrane-bound component of the endocytic receptor complex formed with CUBN (Cubilin) 12. AMN is essential for proper CUBN glycosylation and trafficking to the cell surface 12. The AMN-CUBN complex mediates efficient vitamin B12 (cobalamin) absorption through receptor-mediated endocytosis 314. Additionally, AMN functions in CUBN-mediated protein transport in the kidney, contributing to renal protein absorption. Mutations in AMN cause Imerslund-Grasbeck syndrome 2, a disorder characterized by impaired B12 absorption and protein malabsorption. AMN localizes to the apical plasma membrane and microvillus membrane, positioning it strategically for intestinal and renal nutrient uptake. The protein functions as a cargo receptor in endocytic vesicles and is involved in Golgi-to-plasma membrane trafficking. Through its essential role in the AMN-CUBN receptor complex, AMN enables the body's capacity to absorb critical micronutrients, particularly cobalamin, which is vital for neurological function and cellular metabolism.