title: Sodium-hydrogen exchanger regulatory factor-1 interacts with mouse urate transporter 1 to regulate renal proximal tubule uric acid transport.
abstract: 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.
authors.affiliation: Department of Medicine, University of Maryland School of Medicine, 22 S. Greene St., N3W143, Baltimore, MD 21201, USA. rcunning@medicine.umaryland.edu
authors.forename: Rochelle
authors.initials: R
authors.lastname: Cunningham
authors.forename: Marc
authors.initials: M
authors.lastname: Brazie
authors.forename: Srilatha
authors.initials: S
authors.lastname: Kanumuru
authors.forename: Xiaofei
authors.initials: X
authors.lastname: E
authors.forename: Rajat
authors.initials: R
authors.lastname: Biswas
authors.forename: Fengying
authors.initials: F
authors.lastname: Wang
authors.forename: Deborah
authors.initials: D
authors.lastname: Steplock
authors.forename: James B
authors.initials: JB
authors.lastname: Wade
authors.forename: Naohiko
authors.initials: N
authors.lastname: Anzai
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Endou
authors.forename: Shirish
authors.initials: S
authors.lastname: Shenolikar
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Weinman
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008871:Microvilli / Q000378:metabolism; D027361:Organic Anion Transporters / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D011485:Protein Binding; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D014162:Transfection; D014527:Uric Acid / Q000378:metabolism*
chemical_list: D008565:Membrane Proteins; D027361:Organic Anion Transporters; D010750:Phosphoproteins; C109687:Slc22a12 protein, mouse; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D014527:Uric Acid