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Function and regulation of OATP1B1 and OATP1B3

Wei Yue

Principal Investigator

Agency: NIH-NIGMS (R01)

Abstract

Hepatic uptake transport proteins are now recognized as clinically relevant determinants of variable drug responsiveness and unexpected drug-drug interactions. Organic anion transporting polypeptides (OATP) 1B1 and OATP1B3 are liver-specific, and are major uptake transport proteins that mediate uptake, from blood into the liver, of a diverse array of endogenous compounds (e.g. bile acides), environmental toxins, and many clinically important drugs, including lipid-lowering statins, antibiotics, immunosuppressants, cardiac glycosides, antidiabetic and anticancer agents. Therefore, OATP proteins have significant relevance to human health.
 
Dysfunction of OATP1B1 and OATP1B3 is closely related with altered drug pharmacokinetics and toxicity. Genetic polymorphisms of OATP1B1 and OATP1B3 that have decreased transport function are associated with markedly increased plasma concentrations/systemic exposure of many substrates (e.g., statins, innotecan, digoxin). The c.512TC (V174A) variant of OATP1B1 is the most robust and important predictor of statin-induced myopathy.
 
The long-term goal of this research program is to define the moledular mechanism(s) that affect drug/toxin disposition through OATP1B1 and OATP1B3, and to predict and prevent OATP-mediated drug-drug interactions in humans. To date, only scattered information is known regarding mechanisms involved in regulating OATP1B1 and OATP1B3 function, most of which were studied at the transcriptional level.
 
The objectives of this application are to elucidate the potential role of post-translational regulation via phosphorylation and the ubiquitin system in modulating OATP1B1 and OATP1B3 function.