The methylmercury-L-cysteine conjugate is a substrate for the L-type large neutral amino acid transporter

Zhaobao Yin, Haiyan Jiang, Tore Syversen, João B T Rocha, Marcelo Farina, Michael Aschner

Research output: Contribution to journalArticle

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Abstract

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 [14C]-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 [14C]-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.

Original languageEnglish (US)
Pages (from-to)1083-1090
Number of pages8
JournalJournal of Neurochemistry
Volume107
Issue number4
DOIs
StatePublished - 2008
Externally publishedYes

Fingerprint

Amino Acid Transport System L
Cysteine
CHO Cells
Substrates
L-Lactate Dehydrogenase
Cell Survival
Neutral Amino Acid Transport Systems
Biological membranes
Membranes
Neurotoxins
Blood-Brain Barrier
Methionine
methylmercury cysteine
Assays
Cells

Keywords

  • Amino acid transport
  • L-type large neutral amino acid transporter
  • Methylmercury
  • Neurotoxicity

ASJC Scopus subject areas

  • Biochemistry
  • Medicine(all)
  • Cellular and Molecular Neuroscience

Cite this

The methylmercury-L-cysteine conjugate is a substrate for the L-type large neutral amino acid transporter. / Yin, Zhaobao; Jiang, Haiyan; Syversen, Tore; Rocha, João B T; Farina, Marcelo; Aschner, Michael.

In: Journal of Neurochemistry, Vol. 107, No. 4, 2008, p. 1083-1090.

Research output: Contribution to journalArticle

Yin, Zhaobao ; Jiang, Haiyan ; Syversen, Tore ; Rocha, João B T ; Farina, Marcelo ; Aschner, Michael. / The methylmercury-L-cysteine conjugate is a substrate for the L-type large neutral amino acid transporter. In: Journal of Neurochemistry. 2008 ; Vol. 107, No. 4. pp. 1083-1090.
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AB - 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 [14C]-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 [14C]-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.

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