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: 285/5/C1091    most recent 00021.2003v1 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 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 Web of Science (8) Citing Articles via Google Scholar Google Scholar Articles by Kempson, S. A. Articles by Montrose, M. H. Search for Related Content PubMed PubMed Citation Articles by Kempson, S. A. Articles by Montrose, M. H.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Subcellular redistribution of the renal betaine transporter during hypertonic stress

Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202-5120

Submitted 15 January 2003 ; accepted in final form 30 June 2003

The betaine transporter (BGT1) protects cells in the hypertonic renal inner medulla by mediating uptake and accumulation of the osmolyte betaine. Transcriptional regulation plays an essential role in upregulation of BGT1 transport when renal cells are exposed to hypertonic medium for 24 h. Posttranscriptional regulation of the BGT1 protein is largely unexplored. We have investigated the distribution of BGT1 protein in live cells after transfection with BGT1 tagged with enhanced green fluorescent protein (EGFP). Fusion of EGFP to the NH₂ terminus of BGT1 produced a fusion protein (EGFP-BGT) with transport properties identical to normal BGT1, as determined by ion dependence, inhibitor sensitivity, and apparent K_m for GABA. Confocal microscopy of EGFP-BGT fluorescence in transfected Madin-Darby canine kidney (MDCK) cells showed that hypertonic stress for 24 h induced a shift in subcellular distribution from cytoplasm to plasma membrane. This was confirmed by colocalization with anti-BGT1 antibody staining. In fibroblasts, transfected EGFP-BGT caused increased transport in response to hypertonic stress. The activation of transport was not accompanied by increased expression of EGFP-BGT, as determined by Western blotting. Membrane insertion of EGFP-BGT protein in MDCK cells began within 2-3 h after onset of hypertonic stress and was blocked by cycloheximide. We conclude that posttranscriptional regulation of BGT1 is essential for adaptation to hypertonic stress and that insertion of BGT1 protein to the plasma membrane may require accessory proteins.

Madin-Darby canine kidney cells; fibroblasts; enhanced green fluorescent protein; fluorescence; transfection; laser scanning confocal microscopy

This article has been cited by other articles:

				S. A. Kempson, J. M. Edwards, A. Osborn, and M. Sturek Acute inhibition of the betaine transporter by ATP and adenosine in renal MDCK cells Am J Physiol Renal Physiol, July 1, 2008; 295(1): F108 - F117. [Abstract] [Full Text] [PDF]

				S. A. Kempson, J. M. Edwards, and M. Sturek Inhibition of the renal betaine transporter by calcium ions Am J Physiol Renal Physiol, August 1, 2006; 291(2): F305 - F313. [Abstract] [Full Text] [PDF]

				J. Xu, R. T. Worrell, H. C. Li, S. L. Barone, S. Petrovic, H. Amlal, and M. Soleimani Chloride/Bicarbonate Exchanger SLC26A7 Is Localized in Endosomes in Medullary Collecting Duct Cells and Is Targeted to the Basolateral Membrane in Hypertonicity and Potassium Depletion J. Am. Soc. Nephrol., April 1, 2006; 17(4): 956 - 967. [Abstract] [Full Text] [PDF]