Towards an understanding of organic anion transporters: structure-function relationships

Organic anion transporters (OAT) play essential roles in the body disposition of clinically important anionic drugs, including anti-viral drugs, anti-tumor drugs, antibiotics, anti-hypertensives, and anti-inflammatories. The activities of OATs are directly linked to drug toxicity and drug-drug interactions. So far, four members of the OAT family have been identified: OAT1, OAT2, OAT3, and OAT4. These transporters share several common structural features including 12 transmembrane domains, multiple glycosylation sites localized in the first extracellular loop between transmembrane domains 1 and 2, and multiple phosphorylation sites present in the intracellular loop between transmembrane domains 6 and 7, and in the carboxyl terminus. The impact of these structural features on the function of these transporters has just begun to be explored. In the present review, the author will summarize recent progress made from her laboratory as well as from others, on the molecular characterization of the structure-function relationships of OATs, including particular amino acid residues/regions of the transporter protein ("molecular domains") that potentially determine transport characteristics.