Is phosphorylation of the alpha1 subunit at Ser-16 involved in the control of Na,K-ATPase activity by phorbol ester-activated protein kinase C?
Mol Biol Cell
; 11(1): 39-50, 2000 Jan.
Article
em En
| MEDLINE
| ID: mdl-10637289
ABSTRACT
The alpha1 subunit of Na,K-ATPase is phosphorylated at Ser-16 by phorbol ester-sensitive protein kinase(s) C (PKC). The role of Ser-16 phosphorylation was analyzed in COS-7 cells stably expressing wild-type or mutant (T15A/S16A and S16D-E) ouabain-resistant Bufo alpha1 subunits. In cells incubated at 37 degrees C, phorbol 12, 13-dibutyrate (PDBu) inhibited the transport activity and decreased the cell surface expression of wild-type and mutant Na,K-pumps equally ( approximately 20-30%). This effect of PDBu was mimicked by arachidonic acid and was dependent on PKC, phospholipase A(2), and cytochrome P450-dependent monooxygenase. In contrast, incubation of cells at 18 degrees C suppressed the down-regulation of Na,K-pumps and revealed a phosphorylation-dependent stimulation of the transport activity of Na,K-ATPase. Na,K-ATPase from cells expressing alpha1-mutants mimicking Ser-16 phosphorylation (S16D or S16E) exhibited an increase in the apparent Na affinity. This finding was confirmed by the PDBu-induced increase in Na sensitivity of the activity of Na,K-ATPase measured in permeabilized nontransfected COS-7 cells. These results illustrate the complexity of the regulation of Na,K-ATPase alpha1 isozymes by phorbol ester-sensitive PKCs and reveal 1) a phosphorylation-independent decrease in cell surface expression and 2) a phosphorylation-dependent stimulation of the transport activity attributable to an increase in the apparent Na affinity.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Serina
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Proteína Quinase C
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Dibutirato de 12,13-Forbol
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ATPase Trocadora de Sódio-Potássio
Limite:
Animals
Idioma:
En
Revista:
Mol Biol Cell
Assunto da revista:
BIOLOGIA MOLECULAR
Ano de publicação:
2000
Tipo de documento:
Article
País de afiliação:
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