Role of the l -amino Acid Transporter-1 (LAT-1) in Mouse Trophoblast Cell Invasion

• Published in: Placenta (Eastbourne) 2010-06, Vol.31 (6), p.528-534
• Main Authors: Chrostowski, M.K, McGonnigal, B.G, Stabila, J.P, Padbury, J.F
• Format: Article
• Language: English
• Subjects: Amino Acid Transport System y+ - genetics; Amino Acid Transport System y+ - metabolism; Analysis of Variance; Animals; Biological and medical sciences; Blotting, Western; Cells, Cultured; Down-Regulation - drug effects; Down-Regulation - genetics; Embryology: invertebrates and vertebrates. Teratology; Fundamental and applied biological sciences. Psychology; Gene Expression; Implantation; Internal Medicine; Invasion; L amino acid transporter; LAT-1; Leucine - pharmacology; Mice; Obstetrics and Gynecology; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - genetics; RNA, Messenger - metabolism; RNA, Small Interfering; Slc7a5; Stem Cells; Time Factors; Trophoblast stem cell; Trophoblasts - drug effects; Trophoblasts - metabolism
• ISSN: 0143-4004; 1532-3102
• DOI: 10.1016/j.placenta.2009.12.010

Abstract LAT-1 (L-type amino acid transporter 1) is a system L, Na+ -independent amino acid transporter responsible for transport of large neutral amino acids. Dysregulated expression of LAT-1 is characteristic of many primary human cancers and it's over expression is related to tumor invasion. LAT-1 is highly expressed in the trophoblast giant cells (TGCs) at the time of implantation. Since trophoblast giant cells are highly invasive during the process of endometrial implantation and placentation, LAT-1 may play a role in the invasive phenotype. Our objectives were to identify the effects of increased and decreased LAT-1 expression on mouse trophoblast invasion. We therefore examined the role of amino acid deprivation, pharmacologic blockade specific to leucine transport and gene silencing (siRNA) on LAT-1 expression and trophoblast cell invasion. We utilized mouse primary trophoblast stem (TS) cells. LAT-1 mRNA expression was quantified by real time qPCR, protein by Western blotting and cell invasion was measured in Transwell plates through Matrigel . Amino acid transport using uptake of tritiated leucine. Under limited leucine availability and/or pharmacologic blockage, LAT-1 gene expression was significantly increased, p < 0.05. This was associated with a 3-fold increase in cell invasion, p < 0.05. In contrast, following si RNA-mediated gene silencing decreased LAT-1 expression (both mRNA and protein) was associated with decreased cell invasion and decreased leucine uptake, p < 0.05. Upregulation of LAT-1 gene expression via limited amino acid availability or following pharmacologic blockade of transport leads to an increase in mouse trophoblast stem cell invasiveness. Downregulation of LAT-1 expression via genetic silencing leads to inhibition of invasiveness. These results demonstrate that LAT-1 plays an important role in trophoblast invasion.