Phosphoinositide 3-kinase γ inhibits cardiac GSK-3 independently of Akt.
Sci Signal
; 6(259): ra4, 2013 Jan 22.
Article
em En
| MEDLINE
| ID: mdl-23354687
ABSTRACT
Activation of cardiac phosphoinositide 3-kinase α (PI3Kα) by growth factors, such as insulin, or activation of PI3Kγ downstream of heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors stimulates the activity of the kinase Akt, which phosphorylates and inhibits glycogen synthase kinase-3 (GSK-3). We found that PI3Kγ inhibited GSK-3 independently of the insulin-PI3Kα-Akt axis. Although insulin treatment activated Akt in PI3Kγ knockout mice, phosphorylation of GSK-3 was decreased compared to control mice. GSK-3 is activated when dephosphorylated by the protein phosphatase 2A (PP2A), which is activated when methylated by the PP2A methyltransferase PPMT-1. PI3Kγ knockout mice showed increased activity of PPMT-1 and PP2A and enhanced nuclear export of the GSK-3 substrate NFATc3. GSK-3 inhibits cardiac hypertrophy, and the hearts of PI3Kγ knockout mice were smaller compared to those of wild-type mice. Cardiac overexpression of a catalytically inactive PI3Kγ (PI3Kγ(inact)) transgene in PI3Kγ knockout mice reduced the activities of PPMT-1 and PP2A and increased phosphorylation of GSK-3. Furthermore, PI3Kγ knockout mice expressing the PI3Kγ(inact) transgene had larger hearts than wild-type or PI3Kγ knockout mice. Our studies show that a kinase-independent function of PI3Kγ could directly inhibit GSK-3 function by preventing the PP2A-PPMT-1 interaction and that this inhibition of GSK-3 was independent of Akt.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Cardiomegalia
/
Quinase 3 da Glicogênio Sintase
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Proteínas Proto-Oncogênicas c-akt
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Classe Ib de Fosfatidilinositol 3-Quinase
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Proteínas Musculares
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Miocárdio
Limite:
Animals
/
Humans
Idioma:
En
Revista:
Sci Signal
Assunto da revista:
CIENCIA
/
FISIOLOGIA
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Estados Unidos