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: 293/2/C670    most recent 00516.2006v1 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 Google Scholar Google Scholar Articles by Balamurugan, K. Articles by Said, H. M. Search for Related Content PubMed PubMed Citation Articles by Balamurugan, K. Articles by Said, H. M.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Cloning and functional characterization of a folate transporter from the nematode Caenorhabditis elegans

¹Veterans Affairs Medical Center, Long Beach; and ²Departments of Medicine (Nephrology) and Physiology/Biophysics and ³Department of Anatomy and Neurobiology, School of Medicine, University of California, Irvine, California

Submitted 4 October 2006 ; accepted in final form 27 April 2007

Two putative orthologs to the human reduced folate carrier (hRFC), folt-1 and folt-2, which share a 40 and 31% identity, respectively, with the hRFC sequence, have been identified in the Caenorhabditis elegans genome. Functional characterization of the open reading frame of the putative folt-1 and folt-2 showed folt-1 to be a specific folate transporter. Transport of folate by folt-1 expressed in a heterologous expression system showed an acidic pH dependence, saturability (apparent K_m of 1.23 ± 0.18 µM), a similar degree of inhibition by reduced and substituted folate derivatives, sensitivity to the anti-inflammatory drug sulfasalazine (apparent K_i of 0.13 mM), and inhibition by anion transport inhibitors, e.g., DIDS. Knocking down (silencing) or knocking out the folt-1 gene led to a significant inhibition of folate uptake by intact living C. elegans. We also cloned the 5'-regulatory region of the folt-1 gene and confirmed promoter activity of the construct in vivo in living C. elegans. With the use of the transcriptional fusion construct (i.e., folt-1::GFP), the expression pattern of folt-1 in different tissues of living animal was found to be highest in the pharynx and intestine. Furthermore, folt-1::GFP expression was developmentally and adaptively regulated in vivo. These studies demonstrate for the first time the existence of a specialized folate uptake system in C. elegans that has similar characteristics to the folate uptake process of the human intestine. Thus C. elegans provides a genetically tractable model that can be used to study integrative aspects of the folate uptake process in the context of the whole animal level.

integrative transport physiology; folate transport; transport regulation