title: Direct activation of AMP-activated protein kinase stimulates nitric-oxide synthesis in human aortic endothelial cells.
abstract: Recent studies have indicated that endothelial nitric-oxide synthase (eNOS) is regulated by reversible phosphorylation in intact endothelial cells. AMP-activated protein kinase (AMPK) has previously been demonstrated to phosphorylate and activate eNOS at Ser-1177 in vitro, yet the function of AMPK in endothelium is poorly characterized. We therefore determined whether activation of AMPK with 5'-aminoimidazole-4-carboxamide ribonucleoside (AICAR) stimulated NO production in human aortic endothelial cells. AICAR caused the time- and dose-dependent stimulation of AMPK activity, with a concomitant increase in eNOS Ser-1177 phosphorylation and NO production. AMPK was associated with immunoprecipitates of eNOS, yet this was unaffected by increasing concentrations of AICAR. AICAR also caused the time- and dose-dependent stimulation of protein kinase B phosphorylation. To confirm that the effects of AICAR were indeed mediated by AMPK, we utilized adenovirus-mediated expression of a dominant negative AMPK mutant. Expression of dominant negative AMPK attenuated AICAR-stimulated AMPK activity, eNOS Ser-1177 phosphorylation and NO production and was without effect on AICAR-stimulated protein kinase B Ser-473 phosphorylation or NO production stimulated by insulin or A23187. These data suggest that AICAR-stimulated NO production is mediated by AMPK as a consequence of increased Ser-1177 phosphorylation of eNOS. We propose that stimuli that result in the acute activation of AMPK activity in endothelial cells stimulate NO production, at least in part due to phosphorylation and activation of eNOS. Regulation of endothelial AMPK therefore provides an additional mechanism by which local vascular tone may be controlled.
authors.affiliation: The Henry Wellcome Laboratory of Cell Biology, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, G12 8QQ, United Kingdom.
authors.forename: Valerie A
authors.initials: VA
authors.lastname: Morrow
authors.forename: Fabienne
authors.initials: F
authors.lastname: Foufelle
authors.forename: John M C
authors.initials: JM
authors.lastname: Connell
authors.forename: John R
authors.initials: JR
authors.lastname: Petrie
authors.forename: Gwyn W
authors.initials: GW
authors.lastname: Gould
authors.forename: Ian P
authors.initials: IP
authors.lastname: Salt
mesh_terms: D055372:AMP-Activated Protein Kinases; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D001011:Aorta / Q000166:cytology / Q000378:metabolism*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D009097:Multienzyme Complexes / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D010766:Phosphorylation; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012265:Ribonucleotides / Q000494:pharmacology
chemical_list: D009097:Multienzyme Complexes; D012265:Ribonucleotides; D009569:Nitric Oxide; D000620:Aminoimidazole Carboxamide; C496314:NOS3 protein, human; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide