title: Up-regulation of L-type amino acid transporter 1 (LAT1) in cultured rat retinal capillary endothelial cells in response to glucose deprivation.
abstract: We investigated the regulation of L-type amino acid transporter 1 (LAT1) in a conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2 cells) in response to glucose deprivation. The amounts of LAT1 and 4F2 heavy chain (4F2hc) mRNA in TR-iBRB2 cells exposed to glucose-free culture medium for 8 to 24 h were significantly elevated compared with those in control medium. Concomitantly, [³H]L-leucine uptake activity was increased, suggesting that LAT1 transport activity is induced under glucose-deprivation. To determine the transcriptional activity of the LAT1 gene under glucose-free conditions, the promoter activity of the LAT1 gene of approximately 2 kbp (-1958 bp to +70 bp) in TR-iBRB2 cells was assayed using a dual-luciferase reporter assay system. The transcriptional activity of the 2 kbp LAT1 promoter under the glucose-free conditions was 1.7-fold greater than that under normal glucose conditions. The presence of an activator site(s) between -162 bp and -155 bp was indicated by the low activities exhibited by the construct spanning this region and mutagenesis. These results suggest that the glucose deprivation sensitivity of LAT1 expression is transcriptionally regulated, and cis-elements within the LAT1 promoter region from -162 bp to -155 bp mediate this regulation.
authors.affiliation: Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Matsuyama
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Tomi
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Akanuma
authors.forename: Akiko
authors.initials: A
authors.lastname: Tabuchi
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Kubo
authors.forename: Masanori
authors.initials: M
authors.lastname: Tachikawa
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Hosoya
mesh_terms: D027062:Amino Acid Transport System L / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D001813:Blood-Retinal Barrier; D002196:Capillaries / Q000378:metabolism*; D002460:Cell Line; D004730:Endothelium, Vascular / Q000378:metabolism*; D027282:Fusion Regulatory Protein 1, Heavy Chain / Q000235:genetics / Q000378:metabolism; D017930:Genes, Reporter; D005947:Glucose / Q000378:metabolism*; D007511:Ischemia / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D009154:Mutation; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D012171:Retinal Vessels / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D027062:Amino Acid Transport System L; D027282:Fusion Regulatory Protein 1, Heavy Chain; C420942:ILAT protein, rat; D012333:RNA, Messenger; D011994:Recombinant Proteins; D007930:Leucine; D005947:Glucose