Sodium-hydrogen exchanger regulatory factor-1-deficient (
NHERF-1(-/-)) mice demonstrate increases in the urinary excretion of
phosphate,
calcium, and
uric acid associated with interstitial deposition of
calcium in the papilla of the kidney. These studies examine the role of NHERF-1 in the tubular reabsorption of
uric acid and regulation of mouse
urate transporter 1 (mURAT1), a newly described transporter that is responsible for the renal tubular reabsorption of
uric acid. In primary cultures of mouse renal proximal tubule cells,
uric acid uptake was significantly lower in
NHERF-1(-/-) cells compared with wild-type cells over a large range of
uric acid concentrations in the media. Western immunoblotting revealed a 56 +/- 6% decrease in the brush border membrane (BBM) expression of mURAT1 in
NHERF-1(-/-) compared with wild-type control kidneys (P < 0.05). Confocal microscopy confirmed the reduced apical membrane expression of mURAT1 in
NHERF-1(-/-) kidneys and demonstrated mislocalization of mURAT1 to intracellular vesicular structures. Para-aminohippurate significantly inhibited
uric acid uptake in wild-type cells (41 +/- 2%) compared with
NHERF-1(-/-) cells (8.2 +/- 3%).
Infection of
NHERF-1(-/-) cells with adenovirus-green fluorescence protein-NHERF-1 resulted in significantly higher rates of
uric acid transport (15.4 +/- 1.1 pmol/microg
protein per 30 min) compared with null cells that were infected with control adenovirus-green fluorescence
protein (7.9 +/- 0.3) and restoration of the inhibitory effect of para-aminohippurate (% inhibition 34 +/- 4%). These findings indicate that NHERF-1 exerts a significant effect on the renal tubular reabsorption of
uric acid in the mouse by modulating the BBM abundance of mURAT1 and possibly other BBM
uric acid transporters.