Sodium-dependent phosphate transport protein type IIb (NaPi-IIb)

Sodium-dependent phosphate transport protein type IIb (NaPi-IIb) is a membrane transporter that mediates the electrogenic cotransport of inorganic phosphate and sodium ions into cells, playing a central role in phosphate absorption, especially in the intestine and lung. The protein consists of 690 amino acids, with a molecular weight of approximately 75 kDa. It contains multiple transmembrane domains and is regulated by the parathyroid hormone and other factors. It is critical for systemic phosphate regulation, and its dysfunction leads to substantial disease phenotypes including pulmonary alveolar microlithiasis and altered bone formation. In cancer, NaPi-IIb serves as a tumor-associated antigen and is being pursued as a target for antibody-drug conjugate therapies in ovarian cancer.

Other names

NaPi-IIbNaPi2bSolute carrier family 34 member 2SLC34A2Sodium-phosphate transport protein 2BNaPi-2bNa(+)-dependent phosphate cotransporter 2BSodium/phosphate cotransporter 2B

Antibody-drug conjugate: Selective binding to NaPi-IIb on tumor cells delivers cytotoxic payload Inhibition or modulation of phosphate uptake via competitive or allosteric blockage (theoretical mechanism for small molecules, though clinical use is presently limited)