title: Mechanistic target of rapamycin (mTOR) regulates trophoblast folate uptake by modulating the cell surface expression of FR-α and the RFC.
abstract: Folate deficiency in fetal life is strongly associated with structural malformations and linked to intrauterine growth restriction. In addition, limited availability of methyl donors, such as folate, during pregnancy may result in abnormal gene methylation patterns and contribute to developmental programming. The fetus is dependent on placental transfer of folate, however the molecular mechanisms regulating placental folate transport are unknown. We used cultured primary human trophoblast cells to test the hypothesis that mechanistic target of rapamycin complex 1 (mTORC1) and 2 (mTORC2) regulate folate transport by post-translational mechanisms. Silencing raptor (inhibits mTORC1) or rictor (inhibits mTORC2) markedly decreased basal folate uptake. Folate uptake stimulated by insulin + IGF-1 was mediated by mTORC2 but did not involve mTORC1. mTORC1 or mTORC2 silencing markedly decreased the plasma membrane expression of FR-α and RFC transporter isoforms without affecting global protein expression. Inhibition of the ubiquitin ligase Nedd4-2 had no effect on folate transport. In conclusion, we report for the first time that mTORC1/C2 are positive regulators of cellular folate uptake by modulating the cell surface abundance of specific transporter isoforms. We propose that regulation of placental folate transport by mTOR signaling provide a direct link between placental function, gene methylation and fetal programming.
authors: Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
authors: Fredrick J
authors: FJ
authors: Rosario
authors: Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.|Section of Neonatology, Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
authors: Theresa L
authors: TL
authors: Powell
authors: Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.
authors: Thomas
authors: T
authors: Jansson
mesh_terms: D000328:Adult; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D019175:DNA Methylation; D005260:Female; D058975:Folate Receptor 1 / Q000378:metabolism*; D005492:Folic Acid / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing; D006801:Humans; D008423:Maternal Age; D000075702:Nedd4 Ubiquitin Protein Ligases / Q000378:metabolism; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D034622:RNA Interference; D000076226:Rapamycin-Insensitive Companion of mTOR Protein / Q000378:metabolism; D000076223:Regulatory-Associated Protein of mTOR / Q000378:metabolism; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D014327:Trophoblasts / Q000378:metabolism*
chemical_list: C548696:FOLR1 protein, human; D058975:Folate Receptor 1; C492571:RICTOR protein, human; C463659:RPTOR protein, human; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D000076223:Regulatory-Associated Protein of mTOR; D005492:Folic Acid; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618485:Nedd4L protein, human; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases