title: Expression and regulation of 4F2hc and hLAT1 in human trophoblasts.
abstract: The neutral amino acid transport system L is a sodium-independent transport system in human placenta and choriocarcinoma cells. Recently, it was found that the heterodimer composed of hLAT1 (a light-chain protein) and 4F2 heavy chain (4F2hc), a type II transmembrane glycoprotein, is responsible for system L amino acid transport. We found that the mRNAs of 4F2hc and hLAT1 were expressed in the human placenta and a human choriocarcinoma cell line. The levels of the 4F2hc and hLAT1 proteins in the human placenta increased at full term compared with those at midtrimester. Immunohistochemical data showed that these proteins were localized mainly in the placental apical membrane. Data from leucine uptake experiments, Northern blot analysis, and immunoblot analysis showed that this transport system was partially regulated by protein kinase C and calcium ionophore in the human choriocarcinoma cell line. Our results suggest that the heterodimer of 4F2hc and hLAT1 may play an important role in placental amino acid transport system L.
authors.affiliation: Department of Obstetrics and Gynecology, Osaka University Faculty of Medicine, Osaka 565-0871, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Okamoto
authors.forename: Masahiro
authors.initials: M
authors.lastname: Sakata
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Ogura
authors.forename: Toshiya
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Masaaki
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Keiichi
authors.initials: K
authors.lastname: Tasaka
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Kurachi
authors.forename: Masato
authors.initials: M
authors.lastname: Tsurudome
authors.forename: Yuji
authors.initials: Y
authors.lastname: Murata
mesh_terms: D002118:Calcium / Q000378:metabolism; D002822:Choriocarcinoma; D027282:Fusion Regulatory Protein 1, Heavy Chain / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D015151:Immunoblotting; D007476:Ionophores / Q000378:metabolism; D027283:Large Neutral Amino Acid-Transporter 1 / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D007930:Leucine / Q000493:pharmacokinetics; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D014316:Tritium; D014327:Trophoblasts / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D014407:Tumor Cells, Cultured
chemical_list: D027282:Fusion Regulatory Protein 1, Heavy Chain; D007476:Ionophores; D027283:Large Neutral Amino Acid-Transporter 1; D012333:RNA, Messenger; D014316:Tritium; D011493:Protein Kinase C; D007930:Leucine; D002118:Calcium