Ouabain-induced signaling and vascular smooth muscle cell proliferation.
The hypothesis of this study is that the sodium pump complex acts as an intracellular signal-transducing molecule in canine vascular smooth muscle cells through its interaction with other membrane and cytoskeletal proteins. We have demonstrated that 1 nm ouabain induced transactivation of the epidermal growth factor receptor (EGFR), resulting in increased proliferation and bromodeoxyuridine (BrdUrd) uptake. Immunoprecipitation and Western blotting showed that the EGFR and Src were phosphorylated within 5 min of 10(-9) m ouabain stimulation. Both ouabain-induced DNA synthesis (BrdUrd uptake) and MAPK42/44 phosphorylation were inhibited by the Src inhibitor PP2, the EGFR kinase inhibitor AG1478, the tyrosine kinase inhibitor genistein, and the MEK1 inhibitor PD98059. Ouabain concentrations higher than 1 nm had little or no stimulating effect on proliferation or BrdUrd uptake but did minimally activate ERK1/2. Thus, low concentrations of ouabain, which do not inhibit the sodium pump sufficiently to perturb the resting cellular ionic milieu, initiate a transactivational signaling cascade leading to vascular smooth muscle cell proliferation.
Aydemir-Koksoy
A
A
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030, USA.
Abramowitz
J
J
Allen
J C
JC
D000818:Animals; D015153:Blotting, Western; D002455:Cell Division / Q000187:drug effects*; D002478:Cells, Cultured; D004261:DNA Replication / Q000187:drug effects; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
D004791:Enzyme Inhibitors; D010042:Ouabain; D066246:ErbB Receptors; D019061:src-Family Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases