Differential effects of vanadate on UDP-N-acetylglucosaminyl transferase activity derived from cytosol and nucleosol.
UDP-N-acetylglucosaminyl transferase (OGT) is a key enzyme of a novel signal transduction pathway that regulates protein function through O-linked glycosylation. In the current study, we found that sodium vanadate potently inhibits OGT activity in brain cytosol (IC50 = 55 microM) and nucleosol (IC50 = 150 microM), but fails to alter activity of a related enzyme (UDP-galactosyltransferase). Vanadate also inhibits OGT activity in cytosol (IC50 of 2.3 microM) and nucleosol (IC50 of 130) derived from a stable HeLa cell line that overexpresses OGT. When HeLa cytosol was immunopurified to separate OGT from other cellular proteins, vanadate still inhibited OGT activity (IC50 = 2 microM). We conclude that OGT derived from cytosol exhibits greater vanadate sensitivity than nucleosol OGT and that a large difference exists (25-fold) in vanadate sensitivity when comparing OGT activity in different cell types (IC50 of 55 microM for brain cytosol vs. 2.3 microM for HeLa cytosol). Understanding the mechanism(s) by which a tyrosine phosphatase inhibitor differentially reduces OGT activity should lead to new insights into OGT function and regulation.
Marshall
Stephen
S
Hexos, Inc., Woodinville, WA 98072, USA. Hexos@comcast.net
Okuyama
Ryo
R
D000818:Animals; D001921:Brain / Q000201:enzymology; D002467:Cell Nucleus / Q000201:enzymology*; D003600:Cytosol / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005700:Galactosyltransferases / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D017351:N-Acetylglucosaminyltransferases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D014537:Uridine Diphosphate N-Acetylglucosamine / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D014638:Vanadates; D014537:Uridine Diphosphate N-Acetylglucosamine; D005700:Galactosyltransferases; D017351:N-Acetylglucosaminyltransferases