RESUMEN
Obesity has become the most common metabolic disorder worldwide. Promoting brown adipose tissue (BAT) and beige adipose tissue formation, and therefore, a functional increase in energy expenditure, may counteract obesity. Mice lacking type IIß regulatory subunit of adenosine 3',5' cyclic monophosphate (cAMP)-dependent protein kinase A (PKA-RIIB) display reduced adiposity and resistance to diet-induced obesity. PKA-RIIB, encoded by the Prkar2b gene, is most abundant in BAT and white adipose tissue (WAT) and in the brain. In this study, we show that mice lacking PKA-RIIB have increased energy expenditure, limited weight gain, and improved glucose metabolism. PKA-RIIB deficiency induces brownlike adipocyte in inguinal WAT (iWAT). PKA-RIIB deficiency also increases the expression of uncoupling protein 1 and other thermogenic genes in iWAT and primary preadipocytes from iWAT through a mechanism involving increased PKA activity, which is represented by increased phosphorylation of PKA substrate, cAMP response element binding protein, and P38 mitogen-activated protein kinase. Our study provides evidence for the role of PKA-RIIB deficiency in regulating thermogenesis in WAT, which may potentially have therapeutic implications for the treatment of obesity and related metabolic disorders.
Asunto(s)
Adipocitos Marrones , Tejido Adiposo Blanco/citología , Subunidad RIIbeta de la Proteína Quinasa Dependiente de AMP Cíclico/deficiencia , Metabolismo Energético , Termogénesis , Animales , Metabolismo de los Hidratos de Carbono , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Epidídimo/citología , Glucosa/metabolismo , Metabolismo de los Lípidos , Masculino , Ratones , Obesidad/metabolismo , Proteína Desacopladora 1/metabolismo , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismoRESUMEN
BACKGROUND: Protein kinase A (PKA) is a holoenzyme that consists of a dimer of regulatory subunits and two inactive catalytic subunits that bind to the regulatory subunit dimer. Four regulatory subunits (RIα, RIß, RIIα, RIIß) and four catalytic subunits (Cα, Cß, Cγ, Prkx) have been described in the human and mouse genomes. Previous studies showed that complete inactivation of the Prkar1a subunit (coding for RIα) in the germline leads to embryonic lethality, while Prkar1a-deficient mice are viable and develop schwannomas, thyroid, and bone neoplasms, and rarely lymphomas and sarcomas. Mice with inactivation of the Prkar2a and Prkar2b genes (coding for RIIα and RIIß, respectively) are also viable but have not been studied for their susceptibility to any tumors. METHODS: Cohorts of Prkar1a (+/-) , Prkar2a (+/-) , Prkar2a (-/-) , Prkar2b (+/-) and wild type (WT) mice have been observed between 5 and 25 months of age for the development of hematologic malignancies. Tissues were studied by immunohistochemistry; tumor-specific markers were also used as indicated. Cell sorting and protein studies were also performed. RESULTS: Both Prkar2a (-/-) and Prkar2a (+/-) mice frequently developed hematopoietic neoplasms dominated by histiocytic sarcomas (HS) with rare diffuse large B cell lymphomas (DLBCL). Southern blot analysis confirmed that the tumors diagnosed histologically as DLBCL were clonal B cell neoplasms. Mice with other genotypes did not develop a significant number of similar neoplasms. CONCLUSIONS: Prkar2a deficiency predisposes to hematopoietic malignancies in vivo. RIIα's likely association with HS and DLBCL was hitherto unrecognized and may lead to better understanding of these rare neoplasms.
Asunto(s)
Subunidad RIIalfa de la Proteína Quinasa Dependiente de AMP Cíclico/deficiencia , Subunidad RIIalfa de la Proteína Quinasa Dependiente de AMP Cíclico/genética , Neoplasias Hematológicas/genética , Animales , Transformación Celular Neoplásica/genética , Subunidad RIIalfa de la Proteína Quinasa Dependiente de AMP Cíclico/metabolismo , Subunidad RIIbeta de la Proteína Quinasa Dependiente de AMP Cíclico/deficiencia , Subunidad RIIbeta de la Proteína Quinasa Dependiente de AMP Cíclico/genética , Subunidad RIIbeta de la Proteína Quinasa Dependiente de AMP Cíclico/metabolismo , Subunidad RIalfa de la Proteína Quinasa Dependiente de AMP Cíclico/deficiencia , Subunidad RIalfa de la Proteína Quinasa Dependiente de AMP Cíclico/genética , Subunidad RIalfa de la Proteína Quinasa Dependiente de AMP Cíclico/metabolismo , Modelos Animales de Enfermedad , Estudios de Asociación Genética , Predisposición Genética a la Enfermedad , Genotipo , Neoplasias Hematológicas/patología , Inmunofenotipificación , Ratones , Ratones Noqueados , Fenotipo , Factores de TiempoRESUMEN
Ethanol causes pathological changes in GABAA receptor trafficking and function. These changes are mediated in part by ethanol activation of protein kinase A (PKA). The current study investigated the expression of the GABAA α1 and α4 subunits and the kinase anchoring protein AKAP150, as well as bicuculline-induced seizure threshold, at baseline and following acute injection of ethanol (3.5 g/kg IP) in a mouse line lacking the regulatory RIIß subunit of PKA. Whole cerebral cortices were harvested at baseline, 1 h, or 46 h following injection of ethanol or saline and subjected to fractionation and western blot analysis. Knockout (RIIß-/-) mice had similar baseline levels of PKA RIIα and GABAA α1 and α4 subunits compared to wild type (RIIß+/+) littermates, but had deficits in AKAP150. GABAA α1 subunit levels were decreased in the P2 fraction of RIIß-/-, but not RIIß+/+, mice following 1 h ethanol, an effect that was driven by decreased α1 expression in the synaptic fraction. GABAA α4 subunits in the P2 fraction were not affected by 1 h ethanol; however, synaptic α4 subunit expression was increased in RIIß+/+, but not RIIß-/- mice, while extrasynaptic α4 and δ subunit expression were decreased in RIIß-/-, but not RIIß+/+ mice. Finally, RIIß knockout was protective against bicuculline-induced seizure susceptibility. Overall, the results suggest that PKA has differential roles in regulating GABAA receptor subunits. PKA may protect against ethanol-induced deficits in synaptic α1 and extrasynaptic α4 receptors, but may facilitate the increase of synaptic α4 receptors.
Asunto(s)
Subunidad RIIbeta de la Proteína Quinasa Dependiente de AMP Cíclico/deficiencia , Etanol/administración & dosificación , Regulación de la Expresión Génica , Receptores de GABA-A/biosíntesis , Convulsiones/metabolismo , Animales , Ratones , Ratones de la Cepa 129 , Ratones Endogámicos C57BL , Ratones Noqueados , Convulsiones/inducido químicamenteRESUMEN
PKA is an important mediator of signal transduction downstream of G-protein-coupled receptors and plays a key role in the regulation of metabolism and triglyceride storage. It is a ubiquitous cellular kinase that phosphorylates serine and threonine residues in response to cAMP. PKA consists of two regulatory subunits, RI and RII, that are activated by cAMP to release two catalytic subunits, Calpha and Cbeta. We have shown that C57/BL6J male mice lacking the regulatory RIIbeta subunit have extended lifespan and are resistant to age-related conditions including cardiac decline. In addition to being protected from diet-induced pathologies, PKA Cbeta null mutant mice are protected from age-related problems such as weight gain and enlarged livers, as well as cardiac dysfunction and hypertrophy. Several possible mechanisms for the age sparing effects of PKA inhibition are discussed including A kinase anchoring protein signaling, alterations in the beta-adrenergic pathway, and activation of AMPK. Since PKA is a major metabolic regulator of gene signaling, the human gene homologs are potential pharmacological targets for age-related conditions including heart disease associated with declining cardiac performance.
Asunto(s)
Envejecimiento/fisiología , Proteínas Quinasas Dependientes de AMP Cíclico/fisiología , Corazón/fisiología , Animales , Subunidad RIIbeta de la Proteína Quinasa Dependiente de AMP Cíclico/deficiencia , Subunidad RIIbeta de la Proteína Quinasa Dependiente de AMP Cíclico/genética , Subunidad RIIbeta de la Proteína Quinasa Dependiente de AMP Cíclico/fisiología , Hígado Graso/enzimología , Hígado Graso/prevención & control , Femenino , Cardiopatías/enzimología , Cardiopatías/prevención & control , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Modelos Animales , Modelos Cardiovasculares , Obesidad/enzimología , Obesidad/prevención & control , Fenotipo , Transducción de Señal/fisiologíaRESUMEN
The cAMP/protein kinase A (PKA) signaling cascade is crucial for synaptic plasticity in a wide variety of species. PKA regulates Ca2+ permeation through NMDA receptors (NMDARs) and induction of NMDAR-dependent synaptic plasticity at the Schaffer collateral to CA1 pyramidal cell synapse. Whereas the role of PKA in induction of NMDAR-dependent LTP at CA1 synapses is established, the identity of PKA isoforms involved in this phenomenon is less clear. Here we report that protein synthesis-independent NMDAR-dependent LTP at the Schaffer collateral-CA1 synapse in the hippocampus is deficient, but NMDAR-dependent LTD is normal, in young (postnatal day 10 (P10)-P14) mice lacking PKA RIIbeta, the PKA regulatory protein that links PKA to NMDARs at synaptic sites. In contrast, in young adult (P21-P28) mice lacking PKA RIIbeta, LTP is normal and LTD is abolished. These findings indicate that distinct PKA isoforms may subserve distinct forms of synaptic plasticity and are consistent with a developmental switch in the signaling cascades required for LTP induction.