Immunologic distribution of an organic anion transport protein in
rat liver and kidney.
Bergwerk, Ari J., Xiaoying Shi, Allison C. Ford, Naoaki Kanai,
Emmanuel Jacquemin, Robert D. Burk, Shuang Bai, Phyllis M. Novikoff,
Bruno Stieger, Peter J. Meier, Victor L. Schuster, and Allan W.
Wolkoff.
Marion Bessin Liver Research Center, Division of Nephrology, Albert
Einstein College of Medicine, Bronx, NY 10461; +Unit[acute]e de
Recherche, Bic[circumflex]etre, France; and Division of Clinical
Pharmacology, University Hospital, Zurich, Switzerland
APStracts 3:0032G, 1996.
A Na+-independent organic anion transport protein has recently been
cloned from rat liver using a Xenopus laevis oocyte expression system
(Proc. Natl. Acad. Sci. USA 91:133-137, 1994). Although expression of
this protein is sufficient for cells to transport the organic anion
sulfobromophthalein, little is known about its cell biology or
biochemical characteristics. Northern blot analysis performed under
high stringency revealed hybridization with RNA only from liver and
kidney; transcripts appeared the same in these two organs. Within
kidney, hybridization was greatest using RNA extracted from the outer
medulla. Immunoblot analysis revealed that in liver, the transporter
was enriched in 0.1 M Na2CO3 extracted membranes and sinusoidal
plasma membrane preparations, consistent with its being an integral
membrane protein. This 80 kDa protein migrated as a 65 kDa protein
following treatment with N-glycanase. Immunomorphological examination
of liver revealed basolateral plasma membrane local ization. In 0.1 M
Na2CO3 extracted membranes of kidney, the transporter migrated as an
83 kDa protein on non-reducing SDS-PAGE. Upon reduction, it resolved
into peptides of 33 and 37 kDa. SDS-PAGE migration of the liver
protein was unaffected by reduction. Immunomor phological examination
of kidney revealed apical plasma membrane localization in the S3
segment of the proximal tubule of the outer medulla. Differential
processing and trafficking of this transporter in liver and kidney
may have important functional and regulatory conse quences.
Received 28 August 1995; accepted in final form 26 January 1996.
APS Manuscript Number G374-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 February 96