Abstract
Gout is caused by elevated serum urate levels, which can be treated using inhibitors of the uric acid transporter, URAT1. We exploited affinity differences between the human and rat transporters to map inhibitor binding sites in URAT1. Human-rat transporter chimeras revealed that human URAT1 serine-35, phenylalanine-365 and isoleucine-481 are necessary and sufficient to provide up to a 100-fold increase in affinity for inhibitors. Moreover, serine-35 and phenylalanine-365 are important for high-affinity interaction with the substrate urate. A novel URAT1 binding assay provides support for direct interaction with these amino acids; thus, current clinically important URAT1 inhibitors likely bind the same site in URAT1. A structural model suggests that these three URAT1 residues are in close proximity potentially projecting within the channel. Our results indicate that amino acids from several transmembrane segments functionally cooperate to form a high-affinity URAT1 inhibitor binding site that, when occupied, prevents substrate interactions.
Highlights
Gout is caused by elevated serum urate levels, which can be treated using inhibitors of the uric acid transporter, URAT1
Gout is a metabolic disease caused by chronically elevated serum uric acid levels and deposition of urate in the joints, which leads to painful inflammatory arthritis[1,2]
Genome-wide association studies indicate that a large number of uric acid transporters are involved in urate homeostasis, including the solute carrier (SLC) transporters URAT1 (SLC22A12), organic anion transporter (OAT4), (SLC22A11), GLUT9 (SLC2A9), NPT1 (SLC17A1), NPT4 (SLC17A3), OAT2 (SLC22A7) and the ATP-binding cassette transporter ABCG2/BCRP (ABCG2)[11,12,13,14,15]
Summary
Gout is caused by elevated serum urate levels, which can be treated using inhibitors of the uric acid transporter, URAT1. Our results indicate that amino acids from several transmembrane segments functionally cooperate to form a high-affinity URAT1 inhibitor binding site that, when occupied, prevents substrate interactions. Gout is a metabolic disease caused by chronically elevated serum uric acid (sUA) levels (hyperuricemia) and deposition of urate in the joints, which leads to painful inflammatory arthritis[1,2]. NPT1, NPT4 and ABCG2, on the other hand, are involved in uric acid secretion based on biochemical and physiological studies, and genetic polymorphisms that reduce the activity of these transporters are associated with elevated sUA levels and gout[21,22,23]. Correspondence and requests for materials should be addressed to P.K.T. (email: ptphiltan@ gmail.com) www.nature.com/scientificreports/
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