Expression in Sf9 insect cells, purification and functional reconstitution of the human proton-coupled folate transporter (PCFT, SLC46A1)

PLoS One. 2017 May 11;12(5):e0177572. doi: 10.1371/journal.pone.0177572. eCollection 2017.

Abstract

The proton-coupled folate transporter (PCFT) provides an essential uptake route for the vitamin folic acid (B9) in mammals. In addition, it is currently of high interest for targeting chemotherapeutic agents to tumors due to the increased folic acid requirement of rapidly dividing tumor cells as well as the upregulated PCFT expression in several tumors. To understand its function, determination of its atomic structure and molecular mechanism of transport are essential goals that require large amounts of functional PCFT. Here, we present a high-level heterologous expression system for human PCFT using a recombinant baculovirus and Spodoptera frugiperda (Sf9) insect cells. We demonstrate folate transport functionality along the PCFT expression, isolation, and purification process. Importantly, purified PCFT transports folic acid after reconstitution. We thus succeeded in overcoming heterologous expression as a major bottleneck of PCFT research. The availability of an overexpression system for human PCFT provides the basis for future biochemical, biophysical and structural studies.

MeSH terms

  • Animals
  • Chromatography, Affinity
  • Chromatography, Gel
  • Detergents / pharmacology
  • Folic Acid / metabolism
  • Gene Expression*
  • Humans
  • Liposomes / metabolism
  • Proton-Coupled Folate Transporter / isolation & purification*
  • Proton-Coupled Folate Transporter / metabolism*
  • Sf9 Cells / metabolism*
  • Solubility
  • Tritium / metabolism

Substances

  • Detergents
  • Liposomes
  • Proton-Coupled Folate Transporter
  • SLC46A1 protein, human
  • Tritium
  • Folic Acid

Grants and funding

This work was supported in part by seed grants from the Laura W. Bush Institute for Women’s Health and University Medical Center in Lubbock, Texas (to MJ and GAA), the Center for Membrane Protein Research, School of Medicine, TTUHSC (to MJ), and the TTUHSC Office of Research (to MJ). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.