title: Protein kinase C phosphorylates AMP-activated protein kinase α1 Ser487.
abstract: The key metabolic regulator, AMP-activated protein kinase (AMPK), is reported to be down-regulated in metabolic disorders, but the mechanisms are poorly characterised. Recent studies have identified phosphorylation of the AMPKα1/α2 catalytic subunit isoforms at Ser487/491, respectively, as an inhibitory regulation mechanism. Vascular endothelial growth factor (VEGF) stimulates AMPK and protein kinase B (Akt) in cultured human endothelial cells. As Akt has been demonstrated to be an AMPKα1 Ser487 kinase, the effect of VEGF on inhibitory AMPK phosphorylation in cultured primary human endothelial cells was examined. Stimulation of endothelial cells with VEGF rapidly increased AMPKα1 Ser487 phosphorylation in an Akt-independent manner, without altering AMPKα2 Ser491 phosphorylation. In contrast, VEGF-stimulated AMPKα1 Ser487 phosphorylation was sensitive to inhibitors of protein kinase C (PKC) and PKC activation using phorbol esters or overexpression of PKC-stimulated AMPKα1 Ser487 phosphorylation. Purified PKC and Akt both phosphorylated AMPKα1 Ser487 in vitro with similar efficiency. PKC activation was associated with reduced AMPK activity, as inhibition of PKC increased AMPK activity and phorbol esters inhibited AMPK, an effect lost in cells expressing mutant AMPKα1 Ser487Ala. Consistent with a pathophysiological role for this modification, AMPKα1 Ser487 phosphorylation was inversely correlated with insulin sensitivity in human muscle. These data indicate a novel regulatory role of PKC to inhibit AMPKα1 in human cells. As PKC activation is associated with insulin resistance and obesity, PKC may underlie the reduced AMPK activity reported in response to overnutrition in insulin-resistant metabolic and vascular tissues.
authors: Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K.
authors: Helen R
authors: HR
authors: Heathcote
authors: Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K.
authors: Sarah J
authors: SJ
authors: Mancini
authors: Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K.
authors: Anastasiya
authors: A
authors: Strembitska
authors: Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K.
authors: Kunzah
authors: K
authors: Jamal
authors: Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K.
authors: James A
authors: JA
authors: Reihill
authors: Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K.
authors: Timothy M
authors: TM
authors: Palmer
authors: Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K.
authors: Gwyn W
authors: GW
authors: Gould
authors: Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, U.K.
authors: Ian P
authors: IP
authors: Salt
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D002460:Cell Line; D057809:HEK293 Cells; D006367:HeLa Cells; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology
chemical_list: D042461:Vascular Endothelial Growth Factor A; D012694:Serine; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D055372:AMP-Activated Protein Kinases
keywords: AMPK; protein kinase C; vascular endothelial growth factor