title: The 4F2hc/LAT1 complex transports L-DOPA across the blood-brain barrier.
abstract: L-DOPA is transported across the blood-brain barrier (BBB) by an amino acid transporter, system L. Recently, it has been demonstrated that system L consists of two subunits, 4F2hc and either LAT1 or LAT2. 4F2hc/LAT1 and 4F2hc/LAT2 show different transport characteristics, while their distribution in the brain has not been determined. To clarify whether 4F2hc/LAT1 participates in L-DOPA transport across the BBB, we first examined the expression of 4F2hc/LAT1 in the mouse brain capillary endothelial cell line, MBEC4, as an in vitro BBB model. Northern hybridization and immunoblotting revealed that both 4F2hc and LAT1 are expressed and form a heterodimer in MBEC4 cells. To confirm whether 4F2hc/LAT1 acts as system L to transport L-DOPA, we characterized L-DOPA uptake into the cells. The uptake process was time-dependent, temperature-sensitive, and Na(+)-independent. Neutral amino acids with bulky side chains and a bicyclic amino acid, 2-aminobicyclo-[2, 2,1]-heptane-2-carboxylic acid (BCH), inhibited L-DOPA uptake into MBEC4 cells to a great extent, while an acidic amino acid, basic amino acids, and glycine had no effect. Other neutral amino acids, such as alanine, asparagine, glutamine, serine, and threonine inhibited L-DOPA uptake by 40-70% at most. These characteristics are more compatible with those of 4F2hc/LAT1, rather than those of 4F2hc/LAT2. Finally, immunohistochemistry with anti-LAT1 antibody demonstrated that LAT1 is predominantly expressed in the microvessels of the central nervous system. This is the first report showing that the 4F2hc/LAT1 complex participates in L-DOPA transport across the BBB.
authors.affiliation: Department of Neurology, Graduate School of Medicine, Kyoto University, 54 Shogoin-Kawaharacho, Sakyo-ku, 606-8507, Kyoto, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kageyama
authors.forename: M
authors.initials: M
authors.lastname: Nakamura
authors.forename: A
authors.initials: A
authors.lastname: Matsuo
authors.forename: Y
authors.initials: Y
authors.lastname: Yamasaki
authors.forename: Y
authors.initials: Y
authors.lastname: Takakura
authors.forename: M
authors.initials: M
authors.lastname: Hashida
authors.forename: Y
authors.initials: Y
authors.lastname: Kanai
authors.forename: M
authors.initials: M
authors.lastname: Naito
authors.forename: T
authors.initials: T
authors.lastname: Tsuruo
authors.forename: N
authors.initials: N
authors.lastname: Minato
authors.forename: S
authors.initials: S
authors.lastname: Shimohama
mesh_terms: D026905:Amino Acid Transport Systems; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D002196:Capillaries / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004730:Endothelium, Vascular / Q000378:metabolism*; D005260:Female; D027261:Fusion Regulatory Protein-1; D007980:Levodopa / Q000097:blood / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D021122:Protein Subunits; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D026905:Amino Acid Transport Systems; D000596:Amino Acids; D015703:Antigens, CD; D002352:Carrier Proteins; D027261:Fusion Regulatory Protein-1; D021122:Protein Subunits; D011994:Recombinant Proteins; D007980:Levodopa