Modulation of Na+,K(+)-ATPase activity by a tyrosine phosphorylation process in rat proximal convoluted tubule.
1. In the rat kidney proximal convoluted tubule, epidermal growth factor and insulin have been reported to stimulate Na+ reabsorption. Because most of the effects of these growth factors are mediated by a process of tyrosine phosphorylation and Na+,K(+)-ATPase drives Na+ reabsorption, the influence of tyrosine kinases and tyrosine phosphatases on Na+,K(+)-ATPase activity located in the proximal convoluted tubule was evaluated. 2. Activation of receptor tyrosine kinases by epidermal growth factor and insulin stimulated ouabain-sensitive 86Rb+ uptake. The effects of epidermal growth factor and insulin were prevented by genistein, a tyrosine kinase inhibitor, but were unaffected by GF109203X, a protein kinase C inhibitor. 3. Inhibition of tyrosine phosphatases by orthovanadate (10(-7) and 10(-6)M) mimicked the effects of activation of receptor tyrosine kinases: stimulation of the ouabain-sensitive 86Rb+ uptake and of the hydrolytic activity of Na+,K(+)-ATPase under rate-limiting Na+ concentration, and absence of modification of the maximal activity (Vmax) of the enzyme. The effects of orthovanadate and insulin on the ouabain-sensitive 86Rb+ uptake were not additive. 4. The present results show that both activation of receptor tyrosine kinases and inhibition of tyrosine phosphatases stimulate the Na+,K(+)-ATPase activity through a common mechanism. Thus, a tyrosine phosphorylation process directly controls the Na+,K(+)-ATPase activity and contributes to the physiological control of water and solute reabsorption in the proximal convoluted tubule.
Féraille
E
E
Division de Néphrologie, Hôpital Cantonal Universitaire, Genève, Switzerland.
Carranza
M L
ML
Rousselot
M
M
Favre
H
H
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D008297:Male; D009399:Nephrons / Q000187:drug effects / Q000378:metabolism*; D017027:Protein Tyrosine Phosphatases / Q000187:drug effects* / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects*
D004815:Epidermal Growth Factor; D011505:Protein-Tyrosine Kinases; D017027:Protein Tyrosine Phosphatases; D000254:Sodium-Potassium-Exchanging ATPase