RRC ID 39956
Author Yanagida O, Kanai Y, Chairoungdua A, Kim DK, Segawa H, Nii T, Cha SH, Matsuo H, Fukushima J, Fukasawa Y, Tani Y, Taketani Y, Uchino H, Kim JY, Inatomi J, Okayasu I, Miyamoto K, Takeda E, Goya T, Endou H.
Title Human L-type amino acid transporter 1 (LAT1): characterization of function and expression in tumor cell lines.
Journal Biochim Biophys Acta
Abstract System L is a major nutrient transport system responsible for the transport of large neutral amino acids including several essential amino acids. We previously identified a transporter (L-type amino acid transporter 1: LAT1) subserving system L in C6 rat glioma cells and demonstrated that LAT1 requires 4F2 heavy chain (4F2hc) for its functional expression. Since its oncofetal expression was suggested in the rat liver, it has been proposed that LAT1 plays a critical role in cell growth and proliferation. In the present study, we have examined the function of human LAT1 (hLAT1) and its expression in human tissues and tumor cell lines. When expressed in Xenopus oocytes with human 4F2hc (h4F2hc), hLAT1 transports large neutral amino acids with high affinity (K(m)= approximately 15- approximately 50 microM) and L-glutamine and L-asparagine with low affinity (K(m)= approximately 1.5- approximately 2 mM). hLAT1 also transports D-amino acids such as D-leucine and D-phenylalanine. In addition, we show that hLAT1 accepts an amino acid-related anti-cancer agent melphalan. When loaded intracellularly, L-leucine and L-glutamine but not L-alanine are effluxed by extracellular substrates, confirming that hLAT1 mediates an amino acid exchange. hLAT1 mRNA is highly expressed in the human fetal liver, bone marrow, placenta, testis and brain. We have found that, while all the tumor cell lines examined express hLAT1 messages, the expression of h4F2hc is varied particularly in leukemia cell lines. In Western blot analysis, hLAT1 and h4F2hc have been confirmed to be linked to each other via a disulfide bond in T24 human bladder carcinoma cells. Finally, in in vitro translation, we show that hLAT1 is not a glycosylated protein even though an N-glycosylation site has been predicted in its extracellular loop, consistent with the property of the classical 4F2 light chain. The properties of the hLAT1/h4F2hc complex would support the roles of this transporter in providing cells with essential amino acids for cell growth and cellular responses, and in distributing amino acid-related compounds.
Volume 1514(2)
Pages 291-302
Published 2001-10-1
DOI 10.1016/s0005-2736(01)00384-4
PII S0005273601003844
PMID 11557028
MeSH Amino Acid Transport Systems Amino Acids, Essential / metabolism Animals Antigens, CD / biosynthesis Antigens, CD / genetics Carrier Proteins / biosynthesis Carrier Proteins / chemistry Carrier Proteins / genetics Carrier Proteins / metabolism* DNA Probes DNA, Complementary / genetics DNA, Complementary / isolation & purification Fetus / metabolism Fusion Regulatory Protein-1 Humans Molecular Sequence Data Oocytes / metabolism Protein Biosynthesis RNA, Complementary / genetics RNA, Complementary / isolation & purification RNA, Messenger / analysis RNA, Messenger / biosynthesis Substrate Specificity Tumor Cells, Cultured Xenopus
IF 3.411
Times Cited 441
Human and Animal Cells