Rodent intestinal folate transporters (SLC46A1): Secondary structure, functional properties, and response to dietary folate restriction

Andong Qiu, Hee Min Sang, Michaela Jansen, Usha Malhotra, Eugenia Tsai, Diane C. Cabelof, Larry H. Matherly, Rongbao Zhao, Myles Akabas, I. David Goldman

Research output: Contribution to journalArticle

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Abstract

This laboratory recently identified a human gene that encodes a novel folate transporter [Homo sapiens proton-coupled folate transporter (HsPCFT); SLC46A1] required for intestinal folate absorption. This study focused on mouse (Mus musculus) PCFT (MmPCFT) and rat (Rattus norvegicus) PCFT (RnPCFT) and addresses their secondary structure, specificity, tissue expression, and regulation by dietary folates. Both rodent PCFT proteins traffic to the cell membrane with the NH2- and COOH-termini accessible to antibodies targeted to these domains only in permeabilized HeLa cells. This, together with computer-based topological analyses, is consistent with a model in which rodent PCFT proteins likely contain 12 transmembrane domains. Transport of [ 3H]folates was optimal at pH 5.5 and decreased with increasing pH due to an increase in Km and a decrease in Vmax. At pH 7.0, folic acid and methotrexate influx was negligible, but there was residual (6S)5-methyltetrahydrofolate transport. Uptake of folates in PCFT-injected Xenopus oocytes was electrogenic and pH dependent. Folic acid influx K m values of MmPCFT and RnPCFT, assessed electrophysiologically, were 0.7 and 0.3 μM at pH 5.5 and 1.1 and 0.8 μM at pH 6.5, respectively. Rodent PCFTs were highly specific for monoglutamyl but not polyglutamyl methotrexate. MmPCFT mRNA was highly expressed in the duodenum, proximal jejunum, liver, and kidney with lesser expression in the brain and other tissues. MmPCFT protein was localized to the apical brush-border membrane of the duodenum and proximal jejunum. MmPCFT mRNA levels increased ∼13-fold in the proximal small intestine in mice fed a folate-deficient vesus folatereplete diet, consistent with the critical role that PCFT plays in intestinal folate absorption.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Cell Physiology
Volume293
Issue number5
DOIs
StatePublished - Nov 2007

Fingerprint

Folic Acid Transporters
Folic Acid
Rodentia
Intestinal Absorption
Jejunum
Duodenum
Methotrexate
Proton-Coupled Folate Transporter
Tissue
Messenger RNA
Organ Specificity
Proteins
Brushes
Cell membranes
Nutrition
Microvilli
Xenopus
HeLa Cells
Liver
Small Intestine

Keywords

  • Heme carrier protein-1
  • Hereditary folate malabsorption
  • Intestinal folate absorption
  • Proton-coupled folate transporters

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Cell Biology
  • Physiology

Cite this

Rodent intestinal folate transporters (SLC46A1) : Secondary structure, functional properties, and response to dietary folate restriction. / Qiu, Andong; Sang, Hee Min; Jansen, Michaela; Malhotra, Usha; Tsai, Eugenia; Cabelof, Diane C.; Matherly, Larry H.; Zhao, Rongbao; Akabas, Myles; Goldman, I. David.

In: American Journal of Physiology - Cell Physiology, Vol. 293, No. 5, 11.2007.

Research output: Contribution to journalArticle

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AU - Tsai, Eugenia

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