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The methylmercury‐ l ‐cysteine conjugate is a substrate for the L‐type large neutral amino acid transporter
Author(s) -
Yin Zhaobao,
Jiang Haiyan,
Syversen Tore,
Rocha João B. T.,
Farina Marcelo,
Aschner Michael
Publication year - 2008
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2008.05683.x
Subject(s) - cysteine , chemistry , lactate dehydrogenase , biochemistry , conjugate , methionine , amino acid transporter , cysteic acid , amino acid , viability assay , organic anion transporter 1 , transporter , cell , enzyme , cystine , mathematical analysis , mathematics , gene
Methylmercury (MeHg) is a potent neurotoxin. The mechanism(s) that governs MeHg transport across the blood‐brain barrier and other biological membranes remains unclear. This study addressed the role of the L‐type large neutral amino acid transporter, LAT1, in MeHg transport. Studies were carried out in CHO‐k1 cells. Over‐expression of LAT1 in these cells was associated with enhanced uptake of [ 14 C]‐MeHg when treated with l ‐cysteine, but not with the d ‐cysteine conjugate. In the presence of excess l ‐methionine, a substrate for LAT1, l ‐cysteine‐conjugated [ 14 C]‐MeHg uptake was significantly attenuated. Treatment of LAT‐1 over‐expressing CHO‐k1 cells with l ‐cysteine‐conjugated MeHg was also associated with increased leakage of lactate dehydrogenase into the media as well as reduced cell viability measured by the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide reduction assay. In contrast, knock‐down of LAT1 decreased the uptake of l ‐cysteine‐conjugated MeHg and attenuated the effects of MeHg on lactate dehydrogenase leakage and CHO‐k1 cell viability. These results indicate that the MeHg‐ l ‐cysteine conjugate is a substrate for the neutral amino acid transporter, LAT1, which actively transports MeHg across membranes.