title: Upregulation of the heteromeric y⁺LAT2 transporter contributes to ammonia-induced increase of arginine uptake in rat cerebral cortical astrocytes.
abstract: Increased l-Arg (Arg) uptake to astrocytes and neurons is thought to contribute to enhanced nitric oxide (NO) synthesis and oxidative/nitrosative stress associated with hyperammonemia (HA). Recently we had shown that HA increases the expression in the brain of y(+)LAT2, an isoform of the y(+)L heteromeric transporter which promotes [(3)H]Arg efflux form brain cells in the presence of l-glutamine (Gln) (Zielińska et al., 2011). In this study, we demonstrate that a significant proportion of [(3)H]Arg uptake to cultured cortical astrocytes is likewise mediated by system y(+)L, in addition to the uptake showing characteristics of systems y(+), B(0+) and b(0+). However, stimulation of [(3)H]Arg uptake by treatment with 5mM ammonium chloride ("ammonia") for 48 h could be solely ascribed to the y(+)L-mediated component of the uptake. Ammonia treatment increased the expression of the brain specific y(+)L isoform, y(+)LAT2, both at the mRNA and protein level, and silencing of the Slc7a6 gene coding for y(+)LAT2 protein specifically reduced the ammonia-induced [(3)H]Arg uptake. This study suggests an important role of y(+)LAT2 in the modulation of NO synthesis in the ammonia-exposed astrocytes.
authors.affiliation: Department of Neurotoxicology, Mossakowski Medical Research Centre, Polish Academy of Sciences, Pawińskiego 5 Str., 02-106 Warsaw, Poland. madziul@cmdik.pan.pl
authors.forename: Magdalena
authors.initials: M
authors.lastname: Zielińska
authors.forename: Marta
authors.initials: M
authors.lastname: Skowrońska
authors.forename: Inez
authors.initials: I
authors.lastname: Fręśko
authors.forename: Jan
authors.initials: J
authors.lastname: Albrecht
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D000818:Animals; D001120:Arginine / Q000378:metabolism*; D001253:Astrocytes / Q000378:metabolism*; D015153:Blotting, Western; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D015854:Up-Regulation
chemical_list: D026901:Membrane Transport Proteins; D000641:Ammonia; D001120:Arginine