Characterization of amino acid transport system L in HTB-41 human salivary gland epidermoid carcinoma cells

Background: The amino acid transport system L is a major nutrient transport system that is responsible for transport of neutral amino acids, including several essential amino acids. The current study attempted to investigate the expression and functional characterization of amino acid transport system L in HTB-41 human submaxillary salivary gland epidermoid carcinoma cells. Materials and Methods: RT-PCR analysis, Western blot analysis and amino acid transport measurements were used. Results: The HTB-41 cells expressed the L-type amino acid transporter 1 (LAT1) together with its associating protein heavy chain of 4F2 antigen (4F2hc) in the plasma membrane, whereas the HTB-41 cells did not express the L-type amino acid transporter 2 (LAT2). The uptakes of [ ¹⁴C]L-leucine were Na⁺-independent and completely inhibited by a system L selective inhibitor, 2-aminobicyclo-(2,2,1)-heptane-2- carboxylic acid (BCH). The affinity of [¹⁴C]L-leucine uptake and the inhibition profile of [¹⁴C]L-leucine uptake by various L-amino acids in the HTB-41 cells were comparable with those for the LAT1 expressed in Xenopus oocytes. Conclusion: The transport of neutral amino acids including several essential amino acids into the HTB-41 human submaxillary salivary gland epidermoid carcinoma cells are mediated by LAT1.