Immunolocalization of the sat-1 sulfate-oxalate-bicarbonate anion
exchanger in the rat kidney..
Karniski, Lawrence P., Marius L[diaeresis]otscher, Monica Fucentese,
Helen Hilfiker, J[umlaut]urg Biber, and Heini Murer.
Laboratory of Epithelial Transport, Department of Internal
Medicine, Dept. of Veterans' Affairs Medical Center and University of
Iowa, Iowa City, IA 52242, Institutes of Anatomy and Physiology,
University of Zurich, Winterthurerstrasse 190, 8057 Zurich,
Switzerland
APStracts 5:0068F, 1998.
The rat liver sulfate-bicarbonate-oxalate exchanger (sat-1) transports
sulfate across the canalicular membrane in exchange for either
bicarbonate or oxalate. Sulfate/oxalate exchange has been detected in
the proximal tubule of the kidney where it is probably involved in
the reabsorption of filtered sulfate and the secretion of oxalate,
and may contribute to oxalate-dependent chloride reabsorption.
Screening of a renal cortex cDNA library determined that sat-1 is
expressed in the rat kidney. To evaluate this anion exchanger, the
sat-1 protein was expressed in Sf9 cells. Sodium-independent sulfate
and oxalate uptake was enhanced 7.3-fold and 13.1-fold respectively
in Sf9 cells expressing the sat-1 protein compared to cells infected
with wild type virus. We determined that sat-1 is glycosylated in the
kidney; however anion exchange via sat-1 is observed despite
incomplete glycosylation of sat-1 in Sf9 cells. The sat-1 protein,
with an added carboxy terminus 6 x histidine tag, was purified on a
nickel-affinity column and used to generate anti-sat-1 monoclonal
antibodies. Sat-1 was localized to the basolateral membrane, but not
the apical membrane, of the proximal tubule by both Western blot
analysis and immunohistochemistry. These studies demonstrate that
sulfate/oxalate exchange on the apical and basolateral membranes of
the proximal tubule represents transport on two different anion
exchangers.
Received 7 November 1997; accepted in final form 6 March 1998.
APS Manuscript Number F351-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 6 April 1998