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: 286/3/G491    most recent 00361.2003v1 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 (22) Citing Articles via Google Scholar Google Scholar Articles by Said, H. M. Articles by Marchant, J. S. Search for Related Content PubMed PubMed Citation Articles by Said, H. M. Articles by Marchant, J. S.

MUCOSAL BIOLOGY

Expression and functional contribution of hTHTR-2 in thiamin absorption in human intestine

¹Veterans Affairs Medical Center, Long Beach 90822; ²University of California College of Medicine, Irvine, California 92697; and ³University of Minnesota Medical School, Minneapolis, Minnesota 55455

Submitted 21 August 2003 ; accepted in final form 22 October 2003

The aim of this study was to investigate expression and relative contribution of human thiamin transporter (hTHTR)-2 toward overall carrier-mediated thiamin uptake by human intestinal epithelial cells. Northern blot analysis showed that the message of the hTHTR-2 is expressed along the native human gastrointestinal tract with highest expression being in the proximal part of small intestine. hTHTR-2 protein was found, by Western blot analysis, to be expressed at the brush-border membrane (BBM), but not at the basolateral membrane, of native human enterocytes. This pattern of expression was confirmed in studies using a fusion protein of hTHTR-2 with the enhanced green fluorescent protein (hTHTR2-EGFP) expressed in living Caco-2 cells grown on filter. Pretreating Caco-2 cells (which also express the hTHTR-2 at RNA and protein levels) with hTHTR-2 gene-specific small interfering RNA (siRNA) led to a significant (P < 0.01) and specific inhibition (48%) in carrier-mediated thiamin uptake. Similarly, pretreating Caco-2 cells with siRNA that specifically target hTHTR-1 (which is expressed in Caco-2 cells) also significantly (P < 0.01) and specifically inhibited (by 56%) carrier-mediated thiamin uptake. When Caco-2 cells were pretreated with siRNAs against both hTHTR-2 and hTHTR-1 genes, an almost complete inhibition in carrier-mediated thiamin uptake was observed. These results show that the message of hTHTR-2 is expressed along the human gastrointestinal tract and that expression of its protein in intestinal epithelia is mainly localized to the apical BBM domain. In addition, results show that this transporter plays a significant role in carrier-mediated thiamin uptake in human intestine.

thiamin transport; polarized expression; small interfering RNA; Caco-2 cells

This article has been cited by other articles:

				B. Ashokkumar, J. S. Kumar, G. A. Hecht, and H. M. Said Enteropathogenic Escherichia coli inhibits intestinal vitamin B1 (thiamin) uptake: studies with human-derived intestinal epithelial Caco-2 cells Am J Physiol Gastrointest Liver Physiol, October 1, 2009; 297(4): G825 - G833. [Abstract] [Full Text] [PDF]

				J. C. Reidling, V. S. Subramanian, T. Dahhan, M. Sadat, and H. M. Said Mechanisms and regulation of vitamin C uptake: studies of the hSVCT systems in human liver epithelial cells Am J Physiol Gastrointest Liver Physiol, December 1, 2008; 295(6): G1217 - G1227. [Abstract] [Full Text] [PDF]

				V. S. Subramanian, Z. M. Mohammed, A. Molina, J. S. Marchant, N. D. Vaziri, and H. M. Said Vitamin B1 (thiamine) uptake by human retinal pigment epithelial (ARPE-19) cells: mechanism and regulation J. Physiol., July 1, 2007; 582(1): 73 - 85. [Abstract] [Full Text] [PDF]

				V. S. Subramanian, J. S. Marchant, and H. M. Said Biotin-responsive basal ganglia disease-linked mutations inhibit thiamine transport via hTHTR2: biotin is not a substrate for hTHTR2 Am J Physiol Cell Physiol, November 1, 2006; 291(5): C851 - C859. [Abstract] [Full Text] [PDF]

				B. Ashokkumar, N. D. Vaziri, and H. M. Said Thiamin uptake by the human-derived renal epithelial (HEK-293) cells: cellular and molecular mechanisms Am J Physiol Renal Physiol, October 1, 2006; 291(4): F796 - F805. [Abstract] [Full Text] [PDF]

				S. M. Nabokina, M. L. Kashyap, and H. M. Said Mechanism and regulation of human intestinal niacin uptake Am J Physiol Cell Physiol, July 1, 2005; 289(1): C97 - C103. [Abstract] [Full Text] [PDF]

				J. C. Reidling and H. M. Said Adaptive regulation of intestinal thiamin uptake: molecular mechanism using wild-type and transgenic mice carrying hTHTR-1 and -2 promoters Am J Physiol Gastrointest Liver Physiol, June 1, 2005; 288(6): G1127 - G1134. [Abstract] [Full Text] [PDF]

				L. de Jong, Y. Meng, J. Dent, and S. Hekimi Thiamine Pyrophosphate Biosynthesis and Transport in the Nematode Caenorhabditis elegans Genetics, October 1, 2004; 168(2): 845 - 854. [Abstract] [Full Text] [PDF]

				S. M. Nabokina and H. M. Said Characterization of the 5'-regulatory region of the human thiamin transporter SLC19A3: in vitro and in vivo studies Am J Physiol Gastrointest Liver Physiol, October 1, 2004; 287(4): G822 - G829. [Abstract] [Full Text] [PDF]