| 15848195 |
Uchiyama T, Matsuda Y, Wada M, Takahashi S, Fujita T: Functional regulation of Na+-dependent neutral amino acid transporter ASCT2 by S-nitrosothiols and nitric oxide in Caco-2 cells. FEBS Lett. 2005 Apr 25;579(11):2499-506.
We describe the regulation mechanisms of the Na (+)-dependent neutral amino acid transporter ASCT2 via nitric oxide (NO) in the human intestinal cell line, Caco-2. Exposure of Caco-2 cells to S-nitrosothiol, such as S-nitroso-N-acetyl-DL-penicillamine (SNAP) and S-nitrosoglutathione, and the NO-donor, NOC12, concentration- and time-dependently increased Na (+)-dependent alanine uptake. Kinetic analyses indicated that SNAP increases the maximal velocity (V (max)) of Na (+)-dependent alanine uptake in Caco-2 cells without affecting the Michaelis-Menten constant (K (t)). The stimulatory effect was partially eliminated by actinomycin D and cycloheximide. Increased Na (+)-dependent alanine uptake by SNAP was partially abolished by the NO scavengers, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide sodium salt (carboxy-PTIO) and N-(dithiocarboxy) sarcosine disodium salts (DTCS), as well as the NADPH oxidase inhibitor, diphenyleneiodonium. RT-PCR revealed that Caco-2 cells expressed the Na (+)-dependent neutral amino acid transporter ASCT2, but not the other Na (+)-dependent neutral amino acid transporters ATB (0,+) and B (0) AT1. These results suggested that functional up-regulation of ASCT2 by SNAP might be partially associated with an increase in the density of transporter protein via de novo synthesis. |
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