Abstract
Skeletal muscle Na(+)-K(+)-2Cl(-) cotransporter (NKCC) activity provides a potential mechanism for regulated K(+) uptake. beta-Adrenergic receptor (beta-AR) activation stimulates skeletal muscle NKCC activity in a MAPK pathway-dependent manner. We examined potential G protein-coupled pathways for beta-AR-stimulated NKCC activity. Inhibition of G(s)-coupled PKA blocked isoproterenol-stimulated NKCC activity in both the slow-twitch soleus muscle and the fast-twitch plantaris muscle. However, the PKA-activating agents cholera toxin, forskolin, and 8-bromo-cAMP (8-BrcAMP) were not sufficient to activate NKCC in the plantaris and partially stimulated NKCC activity in the soleus. Isoproterenol-stimulated NKCC activity in the soleus was abolished by pretreatment with pertussis toxin (PTX), indicating a G(i)-coupled mechanism. PTX did not affect the 8-BrcAMP-stimulated NKCC activity. PTX treatment also precluded the isoproterenol-mediated ERK1/2 MAPK phosphorylation in the soleus, consistent with NKCC's MAPK dependency. Inhibition of isoproterenol-stimulated ERK activity by PTX treatment was associated with an increase in Akt activation and phosphorylation of Raf-1 on the inhibitory residue Ser(259). These results demonstrate a novel, muscle phenotype-dependent mechanism for beta-AR-mediated NKCC activation that involves both G(s) and G(i) protein-coupled mechanisms.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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8-Bromo Cyclic Adenosine Monophosphate / pharmacology
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Adrenergic beta-Agonists / pharmacology
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Animals
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Cyclic AMP-Dependent Protein Kinases / drug effects
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Cyclic AMP-Dependent Protein Kinases / metabolism
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Enzyme Activation / drug effects
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Enzyme Activation / physiology
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Enzyme Activators / pharmacology
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Female
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GTP-Binding Protein alpha Subunits, Gi-Go / metabolism
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GTP-Binding Protein alpha Subunits, Gs / metabolism
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GTP-Binding Proteins / metabolism*
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In Vitro Techniques
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Mitogen-Activated Protein Kinase 1 / metabolism
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases / metabolism
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Muscle, Skeletal / drug effects
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Muscle, Skeletal / metabolism*
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Pertussis Toxin
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Phosphorylation / drug effects
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Protein Serine-Threonine Kinases*
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-akt
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Proto-Oncogene Proteins c-raf / metabolism
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Rats
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Receptors, Adrenergic, beta / metabolism*
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Signal Transduction / physiology
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Sodium-Potassium-Chloride Symporters / drug effects
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Sodium-Potassium-Chloride Symporters / metabolism*
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Virulence Factors, Bordetella / pharmacology
Substances
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Adrenergic beta-Agonists
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Enzyme Activators
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Proto-Oncogene Proteins
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Receptors, Adrenergic, beta
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Sodium-Potassium-Chloride Symporters
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Virulence Factors, Bordetella
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8-Bromo Cyclic Adenosine Monophosphate
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Pertussis Toxin
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Akt1 protein, rat
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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Proto-Oncogene Proteins c-raf
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Cyclic AMP-Dependent Protein Kinases
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases
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GTP-Binding Proteins
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GTP-Binding Protein alpha Subunits, Gi-Go
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GTP-Binding Protein alpha Subunits, Gs