RT Journal Article
SR Electronic
T1 Insulin Signaling Regulates γ-Glutamylcysteine Ligase Catalytic Subunit Expression in Primary Cultured Rat Hepatocytes
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 99
OP 108
DO 10.1124/jpet.104.070375
VO 311
IS 1
A1 Sang K. Kim
A1 Kimberley J. Woodcroft
A1 Sarah S. Khodadadeh
A1 Raymond F. Novak
YR 2004
UL http://jpet.aspetjournals.org/content/311/1/99.abstract
AB Decreased glutathione (GSH) levels and γ-glutamylcysteine ligase (GCL) activity have been observed in diabetic patients, and insulin reportedly increases GSH synthesis via increased GCL catalytic subunit (GCLC) gene expression. The signaling pathways responsible for mediating insulin effects on GCLC expression and GSH levels, however, are unknown. The signaling pathways involved in the regulation of GSH synthesis in response to insulin were examined in primary cultured rat hepatocytes. GSH levels, GCL activity, GCLC protein, and mRNA levels were increased to 140, 160, 600, and 340% of that monitored in untreated cells, respectively, in hepatocytes cultured with 100 nM insulin. The phosphatidylinositol 3-kinase (PI3K) inhibitors, wortmannin and LY294002 [2-(4-morpholinyl)-9-phenyl-4H-1-benzopyran-4-one], dominant-negative Akt, or rapamycin, an inhibitor of mTOR (mammalian target of rapamycin) and ribosomal p70 S6 kinase (p70S6K) phosphorylation, inhibited the insulin-mediated increase in GCLC protein and GSH levels. Although the mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinase, p38 MAPK, and JNK (c-Jun N-terminal kinase) were activated in response to insulin, PD98059 (2′-amino-3′-methoxyflavone), an inhibitor of mitogen-activated protein kinase kinase, SP600125 (1,9-pyrazoloanthrone), an inhibitor of JNK, and SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole], an inhibitor of p38 MAPK, failed to inhibit the insulin-mediated increase in GCLC protein levels. In conclusion, these data show that insulin signaling pathways involving PI3K/Akt/p70S6K, but not MAPKs, are active in the insulin-mediated regulation of GSH synthesis via increased GCLC expression. The American Society for Pharmacology and Experimental Therapeutics