title: Regulation of AMP-activated protein kinase by cAMP in adipocytes: roles for phosphodiesterases, protein kinase B, protein kinase A, Epac and lipolysis.
abstract: AMP-activated protein kinase (AMPK) is an important regulator of cellular energy status. In adipocytes, stimuli that increase intracellular cyclic AMP (cAMP) have also been shown to increase the activity of AMPK. The precise molecular mechanisms responsible for cAMP-induced AMPK activation are not clear. Phosphodiesterase 3B (PDE3B) is a critical regulator of cAMP signaling in adipocytes. Here we investigated the roles of PDE3B, PDE4, protein kinase B (PKB) and the exchange protein activated by cAMP 1 (Epac1), as well as lipolysis, in the regulation of AMPK in primary rat adipocytes. We demonstrate that the increase in phosphorylation of AMPK at T172 induced by the adrenergic agonist isoproterenol can be diminished by co-incubation with insulin. The diminishing effect of insulin on AMPK activation was reversed upon treatment with the PDE3B specific inhibitor OPC3911 but not with the PDE4 inhibitor Rolipram. Adenovirus-mediated overexpression of PDE3B and constitutively active PKB both resulted in greatly reduced isoproterenol-induced phosphorylation of AMPK at T172. Co-incubation of adipocytes with isoproterenol and the PKA inhibitor H89 resulted in a total ablation of lipolysis and a reduction in AMPK phosphorylation/activation. Stimulation of adipocytes with the Epac1 agonist 8-pCPT-2'O-Me-cAMP led to increased phosphorylation of AMPK at T172. The general lipase inhibitor Orlistat decreased isoproterenol-induced phosphorylation of AMPK at T172. This decrease corresponded to a reduction of lipolysis from adipocytes. Taken together, these data suggest that PDE3B and PDE4 regulate cAMP pools that affect the activation/phosphorylation state of AMPK and that the effects of cyclic AMP on AMPK involve Epac1, PKA and lipolysis.
authors.affiliation: Lund University, Biomedical Center, C11 Department of Experimental Medical Science, 221 84 Lund, Sweden. bilal.omar@med.lu.se
authors.forename: Bilal
authors.initials: B
authors.lastname: Omar
authors.forename: Emilia
authors.initials: E
authors.lastname: Zmuda-Trzebiatowska
authors.forename: Vincent
authors.initials: V
authors.lastname: Manganiello
authors.forename: Olga
authors.initials: O
authors.lastname: Göransson
authors.forename: Eva
authors.initials: E
authors.lastname: Degerman
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism*; D055372:AMP-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017667:Adipocytes / Q000201:enzymology* / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3 / Q000378:metabolism; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4 / Q000378:metabolism; D005786:Gene Expression Regulation; D020662:Guanine Nucleotide Exchange Factors / Q000819:agonists / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D007783:Lactones / Q000494:pharmacology; D008066:Lipolysis / Q000187:drug effects; D000077403:Orlistat; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: C473217:8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate; D020662:Guanine Nucleotide Exchange Factors; D007328:Insulin; D007546:Isoquinolines; D007783:Lactones; C526973:Rapgef3 protein, rat; D013449:Sulfonamides; D000077403:Orlistat; D000242:Cyclic AMP; D051057:Proto-Oncogene Proteins c-akt; D017868:Cyclic AMP-Dependent Protein Kinases; D055372:AMP-Activated Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D007545:Isoproterenol; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide