Sulfur amino acid restriction induces the pi class of glutathione S-transferase expression in primary rat hepatocytes.
The regulation of genes by amino acids is attracting increasing attention. In the present study, we investigated the restriction of expression of the pi class of glutathione S-transferase (GST Yp) by sulfur amino acids. Hepatocytes isolated from male Sprague-Dawley rats were cultured with L-15-based medium containing low (LSAA; 0.1 mmol/L L-methionine and 0.1 mmol/L L-cysteine) or high (HSAA; 0.5 mmol/L L-methionine and 0.2 mmol/L L-cysteine) amounts of sulfur amino acids for up to 6 d. Cellular protein contents did not differ between LSAA- and HSAA-treated cells over the entire period. In contrast, glutathione concentrations were suppressed by the LSAA medium and on d 6 were only 20% of those of HSAA-treated cells (P < 0.05). As shown by immunoblot analysis, GST Yp protein levels were greater in LSAA-treated cells than in HSAA-treated cells (P < 0.05). The induction of GST Yp by L-methionine and L-cysteine restriction was not affected by insulin and dexamethasone, but the latter suppressed GST Yp expression (P < 0.05). LSAA increased GST Yp mRNA levels and GST activity toward ethacrynic acid (P < 0.05). GST Yp induction occurred only in cells with a limited supply of L-methionine; restriction of L-isoleucine, L-leucine, L-lysine, and L-phenylalanine had no significant effect. In contrast with the induction of GST Yp, the expression of the GST isoforms Ya and Yb was not changed by amino acid restriction. In conclusion, hepatic GST Yp gene expression is upregulated by a limited availability of sulfur amino acids.
Tsai
Chia-Wen
CW
Department of Nutrition, Chung Shan Medical University, Taichung, Taiwan.
Chen
Haw-Wen
HW
Yang
Jaw-Ji
JJ
Liu
Kai-Li
KL
Lii
Chong-Kuei
CK
D000603:Amino Acids, Sulfur / Q000172:deficiency* / Q000494:pharmacology*; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D003907:Dexamethasone / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase / Q000235:genetics*; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology*; D007328:Insulin / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000603:Amino Acids, Sulfur; D017931:DNA Primers; D007328:Insulin; D007527:Isoenzymes; D003907:Dexamethasone; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase; C496558:Gstp1 protein, rat