Involvement of LAT1 and LAT2 in the high- and low-affinity transport of L-leucine in human retinal pigment epithelial cells (ARPE-19 cells)

Atsushi Yamamoto, Shin Ichi Akanuma, Masanori Tachikawa, Ken Ichi Hosoya

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)

Abstract

System L, which is encoded by LAT1 and LAT2, is an amino acid transport system that transports neutral amino acids, including several essential amino acids in an Na+-independent manner. Due to its broad substrate selectivity, system L has been proposed to mediate the transport of amino-acid-related drugs across the blood-tissue barriers. We characterized L-leucine transport and its corresponding transporter in a human retinal pigment epithelial cell line (ARPE-19 cells) as an in vitro model of the outer blood-retinal barrier. [3H]L-leucine uptake by ARPE-19 cells took place in an Na+-, Cl--independent and saturable manner with Km values of 8.71 and 220 μM. This process was more potently cis-inhibited by substrates of LAT1 than those of LAT2. [3H]L-leucine efflux from ARPE-19 cells was trans-stimulated by substrates of LAT1 and LAT2 through the obligatory exchange mechanism of system L. Although RT-PCR analysis demonstrated that LAT1 and LAT2 mRNA are expressed in ARPE-19 cells, the LAT1 mRNA concentration is 42-fold higher than that of LAT2. Moreover, immunoblot analysis demonstrated that LAT1 is expressed in ARPE-19 cells. In conclusion, although the transport function of LAT1 is greater than that of LAT2, LAT1 and LAT2 are involved in L-leucine transport in ARPE-19 cells.

Original languageEnglish
Pages (from-to)2475-2482
Number of pages8
JournalJournal of Pharmaceutical Sciences
Volume99
Issue number5
DOIs
Publication statusPublished - 2010 May

Keywords

  • Carrier-mediated transport
  • L-leucine
  • LAT1
  • LAT2
  • Outer blood-retinal barrier

ASJC Scopus subject areas

  • Pharmaceutical Science

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