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) Supplemental Video All Versions of this Article: 294/1/C233    most recent 00468.2007v1 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 (1) Citing Articles via Google Scholar Google Scholar Articles by Subramanian, V. S. Articles by Said, H. M. Search for Related Content PubMed PubMed Citation Articles by Subramanian, V. S. Articles by Said, H. M.

PROTEIN AND VESICLE TRAFFICKING, CYTOSKELETON

Apical membrane targeting and trafficking of the human proton-coupled transporter in polarized epithelia

Departments of ¹Medicine and ²Physiology and Biophysics, University of California, Irvine, California; ³Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota; and ⁴Department of Veterans Affairs Medical Center, Long Beach, California

Submitted 5 October 2007 ; accepted in final form 7 November 2007

The human proton-coupled folate transporter (hPCFT) is a recently discovered intestinal transporter involved in folate uptake in epithelia (and possibly other cells). Little is currently known about the structure-function relationship of the different domains of this transporter, particularly which regions are important for substrate transport as well as targeting of the transporter to the apical cell surface of polarized cells. Here we have investigated the role of the COOH-terminal domain and a well-conserved sequence separating transmembrane (TM) domains TM2 and TM3 (DXXGRR; amino acids 109–114) speculated by others to be important for transport function. Using live cell imaging approaches, we show that 1) an hPCFT-yellow fluorescent protein construct is functionally expressed at the apical membrane domain and is localized differentially to the human reduced folate carrier; 2) the predicted cytoplasmic COOH-terminal region of hPCFT is not essential for apical targeting or transporter functionality; 3) mutations that ablate a consensus β-turn sequence separating predicted TM2 and TM3 abolished apical [³H]folic acid uptake as a consequence of endoplasmic reticulum retention of mutant, likely misfolded, transporters; and 4) cell surface delivery of hPCFT is disrupted by microtubule depolymerization or by overexpression of the dynactin complex dynamitin (p50). For the first time, our data present information regarding structure-function and membrane targeting of the hPCFT polypeptide, as well as the mechanisms that control its steady-state expression in polarized cells.

folate

This article has been cited by other articles:

				V. S. Subramanian, J. S. Marchant, M. J. Boulware, T. Y. Ma, and H. M. Said Membrane targeting and intracellular trafficking of the human sodium-dependent multivitamin transporter in polarized epithelial cells Am J Physiol Cell Physiol, April 1, 2009; 296(4): C663 - C671. [Abstract] [Full Text] [PDF]

				I. Lasry, B. Berman, R. Straussberg, Y. Sofer, H. Bessler, M. Sharkia, F. Glaser, G. Jansen, S. Drori, and Y. G. Assaraf A novel loss-of-function mutation in the proton-coupled folate transporter from a patient with hereditary folate malabsorption reveals that Arg 113 is crucial for function Blood, September 1, 2008; 112(5): 2055 - 2061. [Abstract] [Full Text] [PDF]

				J. F. Collins Novel insights into intestinal and renal folate transport. Focus on "Apical membrane targeting and trafficking of the human proton-coupled folate transporter in polarized epithelia" Am J Physiol Cell Physiol, February 1, 2008; 294(2): C381 - C382. [Full Text] [PDF]