Hyperglycemia inhibits endothelial nitric oxide synthase activity by posttranslational modification at the Akt site

Citation
Xl. Du et al., Hyperglycemia inhibits endothelial nitric oxide synthase activity by posttranslational modification at the Akt site, J CLIN INV, 108(9), 2001, pp. 1341-1348
Citations number
31
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Medical Research General Topics
Journal title
JOURNAL OF CLINICAL INVESTIGATION
ISSN journal
0021-9738 → ACNP
Volume
108
Issue
9
Year of publication
2001
Pages
1341 - 1348
Database
ISI
SICI code
0021-9738(200111)108:9<1341:HIENOS>2.0.ZU;2-V
Abstract
Endothelial nitric oxide synthase (eNOS) is activated by phosphorylation of serine 1177 by the protein kinase Akt/PKB. Since hyperglycemia-induced mit ochondrial superoxide overproduction increases O-linked N-acetylglucosamine modification and decreases O-linked phosphorylation of the transcription f actor Sp1, the effect of hyperglycemia and the hexosamine pathway on eNOS w as evaluated. In bovine aortic endothelial cells, hyperglycemia inhibited e NOS activity 67%, and treatment with glucosamine had a similar effect. Hype rglycemia-associated inhibition of eNOS was accompanied by a twofold increa se in O-linked N-acetylglucosamine modification of eNOS and a reciprocal de crease in O-linked serine phosphorylation at residue 1177. Both the inhibit ion of eNOS and the changes in its post-translational modifications were re versed by antisense inhibition of glutamine:fructose-6-phosphate amidotrans ferase, the rate-limiting enzyme of the hexosamine pathway, or by blocking mitochondrial superoxide overproduction with uncoupling protein-1 (UCP-1) o r manganese superoxide dismutase (MnSOD). Immunoblot analysis of cells expr essing myc-tagged wild-type human eNOS confirmed the reciprocal increase in O-linked N-acetylglucosamine and decrease in O-linked serine 1177 phosphor ylation in response to hyperglycemia. in contrast, when myc-tagged human eN OS carried a mutation at the Akt phosphorylation site (Ser1177), O-linked N -acetylglucosamine modification was unchanged by hyperglycemia and phospho- eNOS was undetectable. Similar changes in eNOS activity and covalent modifi cation were found in aortae from diabetic animals. Chronic impairment of eN OS activity by this mechanism may partly explain the accelerated atheroscle rosis of diabetes.