PDGF-BB AND IGF-I USE DIFFERENT SIGNALING PATHWAYS TO INDUCE NaK-ATPase SUBUNITS IN CULTURED RAT THORACIC AORTIC SMOOTH MUSCLE CELLS

Abstract

(Na++K+)-adenosine triphosphatase (NaK-ATPase), an ubiquitous membrane transport protein consisting of α and β subunits, regulates Na+/K+fluxes and maintains many vital physiological functions, including cell growth. Results have indicated that platelet-derived growth factor (PDGF) and insulin-like growth factor-I (IGF-I) both enhance NaK-ATPase subunits. Genistein, an inhibitor of tyrosine phosphorylation, inhibits serum- and PDGF-BB-induced NaK-ATPase α1subunit protein levels without inhibiting IGF-I-induced NaK-ATPase α1subunit protein levels. These results indicate that PDGF-BB and IGF-I utilize separate signaling pathways to induce the synthesis of NaK-ATPase α1subunits. In addition, genistein failed to inhibit PDGF-BB-stimulated NaK-ATPase β1subunit levels, suggesting that two separate pathways are involved to induce the synthesis of the NaK-ATPase α1and β1subunits, respectively.