HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 285/2/G371    most recent 00358.2002v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (8) Citing Articles via Google Scholar Google Scholar Articles by Lee, T. K. Articles by Ballatori, N. Search for Related Content PubMed PubMed Citation Articles by Lee, T. K. Articles by Ballatori, N.

LIVER AND BILIARY TRACT

N-glycosylation controls functional activity of Oatp1, an organic anion transporter

Departments of ¹Environmental Medicine and ²Pathology, University of Rochester School of Medicine, Rochester, New York 14642

Submitted 23 August 2002 ; accepted in final form 3 April 2003

Rat Oatp1 (Slc21a1) is an organic anion-transporting polypeptide believed to be an anion exchanger. To characterize its mechanism of transport, Oatp1 was expressed in Saccharomyces cerevisiae under control of the GAL1 promoter. Protein was present at high levels in isolated S. cerevisiae secretory vesicles but had minimal posttranslational modifications and failed to exhibit taurocholate transport activity. Apparent molecular mass (M) of Oatp1 in yeast was similar to that of unmodified protein, 62 kDa, whereas in liver plasma membranes Oatp1 has an M of 85 kDa. To assess whether underglycosylation of Oatp1 in yeast suppressed functional activity, Oatp1 was expressed in Xenopus laevis oocytes with and without tunicamycin, a glycosylation inhibitor. With tunicamycin, M of Oatp1 decreased from 72 to 62 kDa and transport activity was nearly abolished. Mutations to four predicted N-glycosylation sites on Oatp1 (Asn to Asp at positions 62, 124, 135, and 492) revealed a cumulative effect on function of Oatp1, leading to total loss of taurocholate transport activity when all glycosylation sites were removed. M of the quadruple mutant was 62 kDa, confirming that these asparagine residues are sites of glycosylation in Oatp1. Relatively little of the quadruple mutant was able to reach the plasma membrane, and most remained in unidentified intracellular compartments. In contrast, two of the triple mutants tested (N62/124/135D and N124/135/492D) were present in the plasma membrane fraction yet exhibited minimal transport activity. These results demonstrate that both membrane targeting and functional activity of Oatp1 are controlled by the extent of N-glycosylation.

membrane transport; posttranslational modifications; protein trafficking; yeast; Xenopus oocytes

This article has been cited by other articles:

				P. Wang, S. Hata, Y. Xiao, J. W. Murray, and A. W. Wolkoff Topological assessment of oatp1a1: a 12-transmembrane domain integral membrane protein with three N-linked carbohydrate chains Am J Physiol Gastrointest Liver Physiol, April 1, 2008; 294(4): G1052 - G1059. [Abstract] [Full Text] [PDF]

				R. M. Pelis, W. M. Suhre, and S. H. Wright Functional influence of N-glycosylation in OCT2-mediated tetraethylammonium transport Am J Physiol Renal Physiol, May 1, 2006; 290(5): F1118 - F1126. [Abstract] [Full Text] [PDF]