title: Maximal beta3-adrenergic regulation of lipolysis involves Src and epidermal growth factor receptor-dependent ERK1/2 activation.
abstract: Catecholamine-stimulated lipolysis is primarily a beta-adrenergic and cAMP-dependent event. In previous studies we established that the beta(3)-adrenergic receptor (beta(3)AR) in adipocytes utilizes a unique mechanism to stimulate extracellular signal-regulated kinases 1 and 2 (ERK) by direct recruitment and activation of Src kinase. Therefore, we investigated the role of the ERK pathway in adipocyte metabolism and found that the beta(3)AR agonist CL316,243 regulates lipolysis through both cAMP-dependent protein kinase (PKA) and ERK. Inhibition of PKA activity completely eliminated lipolysis at low (subnanomolar) CL316,243 concentrations and by 75-80% at higher nanomolar concentrations. The remaining 20-25% of PKA-independent lipolysis, as well as ERK activation, was abolished by inhibiting the activity of either Src (PP2 or small interfering RNA), epidermal growth factor receptor (EGFR with AG1478 or small interfering RNA), or mitogen-activated protein kinase kinase 1 or 2 (MKK1/2 with PD098059). PD098059 inhibited lipolysis by 53% in mice as well. Finally, the effect of estradiol, a reported acute activator of ERK and lipolysis, was also totally prevented by PP2, AG1478, and PD098059. These results suggest that ERK activation by beta(3)AR depends upon Src and epidermal growth factor receptor kinase activities and is responsible for the PKA-independent portion of the lipolytic response. Together these results illustrate the distinct and complementary roles for PKA and ERK in catecholamine-stimulated lipolysis.
authors.affiliation: Program in Endocrine Biology, Division of Biological Sciences, CIIT Centers for Health Research, Research Triangle Park, North Carolina 27709, USA.
authors.forename: Jacques
authors.initials: J
authors.lastname: Robidoux
authors.forename: Naresh
authors.initials: N
authors.lastname: Kumar
authors.forename: Kiefer W
authors.initials: KW
authors.lastname: Daniel
authors.forename: Fatiha
authors.initials: F
authors.lastname: Moukdar
authors.forename: Michel
authors.initials: M
authors.lastname: Cyr
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Medvedev
authors.forename: Sheila
authors.initials: S
authors.lastname: Collins
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D058667:Adrenergic beta-3 Receptor Agonists; D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004149:Dioxoles / Q000494:pharmacology; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D008066:Lipolysis / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D011799:Quinazolines; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D022702:Receptors, Adrenergic, beta-3 / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology; D020032:Tyrphostins / Q000494:pharmacology; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D058667:Adrenergic beta-3 Receptor Agonists; D004149:Dioxoles; D005419:Flavonoids; D007546:Isoquinolines; D011799:Quinazolines; D034741:RNA, Small Interfering; D022702:Receptors, Adrenergic, beta-3; D013449:Sulfonamides; D020032:Tyrphostins; C076126:disodium (R,R)-5-(2-((2-(3-chlorophenyl)-2-hydroxyethyl)-amino)propyl)-1,3-benzodioxole-2,3-dicarboxylate; C101044:RTKI cpd; D004958:Estradiol; D066246:ErbB Receptors; D019061:src-Family Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one