Vitamin B12 transport and receptor system

The Vitamin B12 transport and receptor system is a multi-component physiological pathway essential for the absorption and cellular delivery of cobalamin. The process begins with Gastric Intrinsic Factor (GIF) binding dietary B12 in the small intestine, forming a complex that is recognized by the Cubam receptor—a heterodimer of Cubilin (CUBN) and Amnionless (AMN)—in the terminal ileum [1][2]. Following endocytosis and release into the bloodstream, B12 is bound by Transcobalamin II (TCN2) and delivered to peripheral tissues via the CD320 receptor [4]. This system is the primary therapeutic target for treating B12 deficiency and pernicious anemia through the administration of various cobalamin forms [3]. Beyond supplementation, the high-affinity Cubam-mediated uptake mechanism is being investigated as a vehicle for the oral delivery of therapeutic peptides and other poorly absorbed drugs [2]. Dysfunctions in this system, whether due to autoimmune destruction of intrinsic factor or genetic mutations in the receptors, lead to severe hematological and neurological disorders [3]. This entry is marked as incorrect because it aggregates multiple distinct proteins (GIF, CUBN, AMN, TCN2, and CD320) into a single functional system rather than a single molecular target.

Other names

Cobalamin transport systemIntrinsic factor-cobalamin receptor systemCubam complexIF-Cbl receptorTranscobalamin receptor system

Exogenous cobalamin ligands bind to transport proteins (Intrinsic Factor or Transcobalamin) to facilitate receptor-mediated endocytosis via the Cubam complex or CD320 receptor, restoring physiological vitamin levels.