title: Signaling the signal, cyclic AMP-dependent protein kinase inhibition by insulin-formed H2O2 and reactivation by thioredoxin.
abstract: Catecholamines in adipose tissue promote lipolysis via cAMP, whereas insulin stimulates lipogenesis. Here we show that H(2)O(2) generated by insulin in rat adipocytes impaired cAMP-mediated amplification cascade of lipolysis. These micromolar concentrations of H(2)O(2) added before cAMP suppressed cAMP activation of type IIbeta cyclic AMP-dependent protein kinase (PKA) holoenzyme, prevented hormone-sensitive lipase translocation from cytosol to storage droplets, and inhibited lipolysis. Similarly, H(2)O(2) impaired activation of type IIalpha PKA holoenzyme from bovine heart and from that reconstituted with regulatory IIalpha and catalytic alpha subunits. H(2)O(2) was ineffective (a) if these PKA holoenzymes were preincubated with cAMP, (b) if added to the catalytic alpha subunit, which is active independently of cAMP activation, and (c) if the catalytic alpha subunit was substituted by its C199A mutant in the reconstituted holoenzyme. H(2)O(2) inhibition of PKA activation remained after H(2)O(2) elimination by gel filtration but was reverted with dithiothreitol or with thioredoxin reductase plus thioredoxin. Electrophoresis of holoenzyme in SDS gels showed separation of catalytic and regulatory subunits after cAMP incubation but a single band after H(2)O(2) incubation. These data strongly suggest that H(2)O(2) promotes the formation of an intersubunit disulfide bond, impairing cAMP-dependent PKA activation. Phylogenetic analysis showed that Cys-97 is conserved only in type II regulatory subunits and not in type I regulatory subunits; hence, the redox regulation mechanism described is restricted to type II PKA-expressing tissues. In conclusion, phylogenetic analysis results, selective chemical behavior, and the privileged position in holoenzyme lead us to suggest that Cys-97 in regulatory IIalpha or IIbeta subunits is the residue forming the disulfide bond with Cys-199 in the PKA catalytic alpha subunit. A new molecular point for cross-talk among heterologous signal transduction pathways is demonstrated.
authors.affiliation: Departamento de Bioquímica, Facultad de Medicina, and Unidad de Biomedicina, Facultad de Estudios Superiores Iztacala, Universidad Nacional Autónoma de México, México, DF 04510, México.
authors.forename: Martha Zentella
authors.initials: MZ
authors.lastname: de Piña
authors.forename: Héctor
authors.initials: H
authors.lastname: Vázquez-Meza
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Pardo
authors.forename: Juan Luis
authors.initials: JL
authors.lastname: Rendón
authors.forename: Rafael
authors.initials: R
authors.lastname: Villalobos-Molina
authors.forename: Héctor
authors.initials: H
authors.lastname: Riveros-Rosas
authors.forename: Enrique
authors.initials: E
authors.lastname: Piña
mesh_terms: D017667:Adipocytes / Q000187:drug effects / Q000201:enzymology; D000818:Animals; D002384:Catalysis / Q000187:drug effects; D020134:Catalytic Domain; D002417:Cattle; D000242:Cyclic AMP / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors* / Q000302:isolation & purification / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D020035:Holoenzymes / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism* / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D008066:Lipolysis / Q000187:drug effects; D008297:Male; D008954:Models, Biological; D009206:Myocardium / Q000201:enzymology; D010084:Oxidation-Reduction / Q000187:drug effects; D010802:Phylogeny; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects*; D002787:Sterol Esterase / Q000378:metabolism; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013879:Thioredoxins / Q000494:pharmacology*
chemical_list: D004220:Disulfides; D020035:Holoenzymes; D007328:Insulin; D013439:Sulfhydryl Reagents; D013879:Thioredoxins; D006861:Hydrogen Peroxide; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D002787:Sterol Esterase