Transcobalamin receptor (CD320) (CD320)

The cellular cobalamin uptake system, primarily mediated by the transcobalamin receptor (CD320), is the essential pathway for transporting vitamin B12 (cobalamin) from the bloodstream into cells (UniProt: Q9NPF9). Vitamin B12 is a vital cofactor for enzymes involved in DNA synthesis and fatty acid metabolism, making its uptake critical for rapidly dividing cells (Quadros, 2010 [PMID: 19118206]). The process involves the binding of transcobalamin-bound cobalamin to CD320 on the plasma membrane, triggering receptor-mediated endocytosis (Alam et al., 2016 [PMID: 27345170]). Because many cancer cells overexpress CD320 to meet high metabolic demands, this system is frequently explored as a target for tumor-targeted drug delivery and diagnostic imaging using cobalamin conjugates (Waibel et al., 2008 [PMID: 18808185]). Dysfunctions in this uptake system, such as genetic mutations in CD320, lead to intracellular B12 deficiency, resulting in clinical conditions like megaloblastic anemia and methylmalonic aciduria. Therapeutic strategies often focus on supplementing cobalamin or utilizing the receptor's high affinity for its ligand to deliver cytotoxic agents or imaging probes directly to diseased tissues.

Other names

TCblR8D6 antigenTranscobalamin II receptorCD320 moleculeCellular cobalamin uptake system

The system facilitates the cellular entry of vitamin B12 by binding the transcobalamin-cobalamin complex (Holo-TC) at the cell surface via the CD320 receptor, followed by receptor-mediated endocytosis and lysosomal release of the vitamin (Alam et al., 2016 [PMID: 27345170]).