RESUMO
Cyclic adenosine 3', 5'-monophosphate (cAMP) is a ubiquitous mediator of intracellular signalling events. It acts principally through stimulation of cAMP-dependent protein kinases (PKAs) but also activates certain ion channels and guanine nucleotide exchange factors (Epacs). Metabolism of cAMP is catalysed by phosphodiesterases (PDEs). Here we identify a cAMP-responsive signalling complex maintained by the muscle-specific A-kinase anchoring protein (mAKAP) that includes PKA, PDE4D3 and Epac1. These intermolecular interactions facilitate the dissemination of distinct cAMP signals through each effector protein. Anchored PKA stimulates PDE4D3 to reduce local cAMP concentrations, whereas an mAKAP-associated ERK5 kinase module suppresses PDE4D3. PDE4D3 also functions as an adaptor protein that recruits Epac1, an exchange factor for the small GTPase Rap1, to enable cAMP-dependent attenuation of ERK5. Pharmacological and molecular manipulations of the mAKAP complex show that anchored ERK5 can induce cardiomyocyte hypertrophy. Thus, two coupled cAMP-dependent feedback loops are coordinated within the context of the mAKAP complex, suggesting that local control of cAMP signalling by AKAP proteins is more intricate than previously appreciated.
Assuntos
3',5'-AMP Cíclico Fosfodiesterases/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , AMP Cíclico/metabolismo , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Transdução de Sinais , 3',5'-AMP Cíclico Fosfodiesterases/genética , Animais , Linhagem Celular , Nucleotídeo Cíclico Fosfodiesterase do Tipo 4 , Citocinas/metabolismo , Humanos , Hipertrofia/induzido quimicamente , Proteína Quinase 7 Ativada por Mitógeno/metabolismo , Complexos Multiproteicos/química , Complexos Multiproteicos/genética , Complexos Multiproteicos/metabolismo , Miocárdio/metabolismo , Miocárdio/patologia , RatosRESUMO
mAKAP (muscle-selective A-kinase-anchoring protein) co-ordinates a cAMP-sensitive negative-feedback loop comprising PKA (cAMP-dependent protein kinase) and the cAMP-selective PDE4D3 (phosphodiesterase 4D3). In vitro and cellular experiments demonstrate that PKA-phosphorylation of PDE4D3 on Ser-13 increases the affinity of PDE4D3 for mAKAP. Our data suggest that activation of mAKAP-anchored PKA enhances the recruitment of PDE4D3, allowing for quicker signal termination.
Assuntos
3',5'-AMP Cíclico Fosfodiesterases/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/fisiologia , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Sítios de Ligação , Nucleotídeo Cíclico Fosfodiesterase do Tipo 4 , Ativação Enzimática/fisiologia , Humanos , Rim/citologia , Rim/embriologia , Rim/enzimologia , Mimetismo Molecular/fisiologia , Fragmentos de Peptídeos/metabolismo , Peptídeos/metabolismo , Fosforilação , Ligação Proteica/fisiologia , Mapeamento de Interação de Proteínas , Serina/metabolismoRESUMO
Compartmentalization of kinases and phosphatases is a key determinant in the specificity of second messenger-mediated signaling events. Localization of the cAMP-dependent protein kinase (PKA) and other signaling enzymes is mediated by interaction with A-kinase anchoring proteins (AKAPs). This study focused on recent advances that further our understanding of AKAPs, with particular emphasis on the bidirectional regulation of signaling events by AKAP signaling complexes and their contribution to the control of actin reorganization events.