title: Na,K-ATPase activity modulates Src activation: a role for ATP/ADP ratio.
abstract: Digitalis-like compounds (DLCs), specific inhibitors of Na,K-ATPase, are implicated in cellular signaling. Exposure of cell cultures to ouabain, a well-known DLC, leads to up- or down regulation of various processes and involves activation of Src kinase. Since Na,K-ATPase is the only known target for DLC binding an in vitro experimental setup using highly purified Na,K-ATPase from pig kidney and commercially available recombinant Src was used to investigate the mechanism of coupling between the Na,K-ATPase and Src. Digoxin was used as a representative DLC for inhibition of Na,K-ATPase. The activation of Src kinase was measured as the degree of its autophosphorylation. It was observed that in addition to digoxin, Src activation was dependent on concentrations of other specific ligands of Na,K-ATPase: Na(+), K(+), vanadate, ATP and ADP. The magnitude of the steady-state ATPase activity therefore seemed to affect Src activation. Further experiments with an ATP regenerating system showed that the ATP/ADP ratio determined the extent of Src activation. Thus, our model system which represents the proposed very proximal part of the Na,K-ATPase-Src signaling cascade, shows that Src kinase activity is regulated by both ATP and ADP concentrations and provides no evidence for a direct interaction between Na,K-ATPase and Src.
authors.affiliation: Department of Pharmacology and Toxicology 149, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands. K.Weigand@pharmtox.umcn.nl
authors.forename: Karl M
authors.initials: KM
authors.lastname: Weigand
authors.forename: Herman G P
authors.initials: HG
authors.lastname: Swarts
authors.forename: Natalya U
authors.initials: NU
authors.lastname: Fedosova
authors.forename: Frans G M
authors.initials: FG
authors.lastname: Russel
authors.forename: Jan B
authors.initials: JB
authors.lastname: Koenderink
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D004071:Digitalis Glycosides / Q000737:chemistry; D004077:Digoxin / Q000737:chemistry; D004789:Enzyme Activation / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000737:chemistry / Q000378:metabolism; D010042:Ouabain / Q000737:chemistry*; D010766:Phosphorylation / Q000502:physiology; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013552:Swine; D019061:src-Family Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D004071:Digitalis Glycosides; D011994:Recombinant Proteins; D010042:Ouabain; D000244:Adenosine Diphosphate; D004077:Digoxin; D000255:Adenosine Triphosphate; D019061:src-Family Kinases; D000254:Sodium-Potassium-Exchanging ATPase