Regulation of ERK1/2 by ouabain and Na-K-ATPase-dependent energy utilization and AMPK activation in parotid acinar cells.
Am J Physiol Cell Physiol
; 295(3): C590-9, 2008 Sep.
Article
em En
| MEDLINE
| ID: mdl-18632735
ABSTRACT
We previously found that the phosphorylation of ERK1/2 by submaximal concentrations of the muscarinic receptor ligand carbachol was potentiated in rat parotid acinar cells exposed to ouabain, a cardiac glycoside that inhibits the Na-K-ATPase. We now report that this signaling phenomenon involves the prevention of negative regulation of extracellular signal-regulated kinase-1/2 (ERK1/2) that is normally mediated by AMP-activated protein kinase (AMPK). Carbachol increases the turnover of the ATP-consuming Na-K-ATPase, reducing intracellular ATP and promoting the phosphorylation/activation of the energy sensor AMPK. Ouabain blocks the reduction in ATP and subsequent AMPK phosphorylation, which is regulated by the AMP-to-ATP ratio. The ouabain-promoted enhancement of ERK1/2 phosphorylation was not reproduced in Par-C10 cells, an immortalized rat parotid cell line that did not respond to carbachol with an ATP reduction and that employs an upstream AMPK kinase (Ca(2+)/calmodulin-dependent protein kinase kinase, CaMKK) different from that (LKB1) in native cells. In native parotid cells, inhibitory effects of AMPK on ERK1/2 signaling were examined by activating AMPK with 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR), which is converted to an AMP mimetic but does not alter parotid ATP levels. AICAR-treated cells display increases in AMPK phosphorylation and a reduced phosphorylation of ERK1/2 subsequent to activation of muscarinic and P2X(7) receptors, which promote increases in Na-K-ATPase turnover, but not upon epidermal growth factor receptor activation. These results suggest that carbachol-initiated AMPK activation can produce a negative feedback on ERK1/2 signaling in response to submaximal muscarinic receptor activation and that increases in fluid secretion can modulate receptor-initiated signaling events indirectly by producing ion transport-dependent decreases in ATP.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Ouabaína
/
Glândula Parótida
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Proteínas Serina-Treonina Quinases
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ATPase Trocadora de Sódio-Potássio
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Proteína Quinase 1 Ativada por Mitógeno
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Proteína Quinase 3 Ativada por Mitógeno
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Metabolismo Energético
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Inibidores Enzimáticos
/
Complexos Multienzimáticos
Limite:
Animals
Idioma:
En
Ano de publicação:
2008
Tipo de documento:
Article