title: Mammalian target of rapamycin signalling modulates amino acid uptake by regulating transporter cell surface abundance in primary human trophoblast cells.
abstract: Abnormal fetal growth increases the risk for perinatal complications and predisposes for the development of obesity, diabetes and cardiovascular disease later in life. Emerging evidence suggests that changes in placental amino acid transport directly contribute to altered fetal growth. However, the molecular mechanisms regulating placental amino acid transport are largely unknown. Here we combined small interfering (si) RNA-mediated silencing approaches with protein expression/localization and functional studies in cultured primary human trophoblast cells to test the hypothesis that mammalian target of rapamycin complex 1 (mTORC1) and 2 (mTORC2) regulate amino acid transporters by post-translational mechanisms. Silencing raptor (inhibits mTORC1) or rictor (inhibits mTORC2) markedly decreased basal System A and System L amino acid transport activity but had no effect on growth factor-stimulated amino acid uptake. Simultaneous inhibition of mTORC1 and 2 completely inhibited both basal and growth factor-stimulated amino acid transport activity. In contrast, mTOR inhibition had no effect on serotonin transport. mTORC1 or mTORC2 silencing markedly decreased the plasma membrane expression of specific System A (SNAT2, SLC38A2) and System L (LAT1, SLC7A5) transporter isoforms without affecting global protein expression. In conclusion, mTORC1 and mTORC2 regulate human trophoblast amino acid transporters by modulating the cell surface abundance of specific transporter isoforms. This is the first report showing regulation of amino acid transport by mTORC2. Because placental mTOR activity and amino acid transport are decreased in human intrauterine growth restriction our data are consistent with the possibility that dysregulation of placental mTOR plays an important role in the development of abnormal fetal growth.
authors.affiliation: Center for Pregnancy and Newborn Research, Department of Obstetrics and Gynecology, University of Texas Health Science Center San Antonio, Mail Code 7836, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA. josephf@uthscsa.edu
authors.forename: Fredrick J
authors.initials: FJ
authors.lastname: Rosario
authors.forename: Yoshikatsu
authors.initials: Y
authors.lastname: Kanai
authors.forename: Theresa L
authors.initials: TL
authors.lastname: Powell
authors.forename: Thomas
authors.initials: T
authors.lastname: Jansson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D026924:Amino Acid Transport System A / Q000378:metabolism*; D027062:Amino Acid Transport System L / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007930:Leucine / Q000378:metabolism; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D046912:Multiprotein Complexes / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D000076223:Regulatory-Associated Protein of mTOR; D012701:Serotonin / Q000378:metabolism; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D014327:Trophoblasts / Q000166:cytology / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D026924:Amino Acid Transport System A; D027062:Amino Acid Transport System L; D002352:Carrier Proteins; D046912:Multiprotein Complexes; C492571:RICTOR protein, human; D034741:RNA, Small Interfering; C463659:RPTOR protein, human; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D000076223:Regulatory-Associated Protein of mTOR; D012701:Serotonin; D007334:Insulin-Like Growth Factor I; C546842:MTOR protein, human; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D058570:TOR Serine-Threonine Kinases; D007930:Leucine