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Hydrophobic residues as a key determinant in hexoses exchange urate mechanism mediated by human glucose transporter 9, hSLC2A9
Author(s) -
Long Wentong,
Cheeseman Chris I.,
Witkowska Kate
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.lb863
Subject(s) - hyperuricemia , efflux , chemistry , fructose , hexose , transporter , biochemistry , glucose transporter , mutant , uric acid , enzyme , biology , endocrinology , gene , insulin
Human GLUT9 (hSLC2A9) is a urate/hexose transporter expressed predominantly in the liver and kidney where human urate homeostasis is achieved. hSLC2A9 has two splice variants: 9a and 9b differing in their N‐termini and targeted differentially within polarized epithelia. The transporter shows trans‐acceleration between urate and hexoses, however, the mechanism is unknown. Hydrophobic residues in TM7 of GLUTs have been shown to play a role in hexose selectivity. Objective To investigate urate/hexose exchange mediated by SLC2A9 isoforms and their mutants. Methods hSLC2A9 isoforms and I335V mutants were overexpressed in X. laevis oocytes. Urate induced currents and I‐V curves were obtained using Two Micro‐Electrode Voltage Clamp (TEVC) recordings. Urate transport and hexose trans‐stimulation activities were determined by radiolabelled urate uptake and efflux measurements. Results TEVC studies demonstrated that the membrane potential plays a major role in urate transport mediated by hSLC2A9. Fructose was found to trans‐stimulate urate uptake and efflux in wild type hSLC2A9a; whereas it stimulates only urate efflux in the I335V mutant. These finding advance our understanding of how fructose intake is linked with serum urate levels and implicates hSLC2A9 as an important transporter that may contribute to pathophysiological conditions involving urate or fructose. Supported by CIHR.