Novel role for Na,K-ATPase in phosphatidylinositol 3-kinase signaling and suppression of cell motility

• Published in: Molecular biology of the cell Vol. 16; no. 3; pp. 1082 - 1094
• Main Authors: Barwe, Sonali P, Anilkumar, Gopalakrishnapillai, Moon, Sun Y, Zheng, Yi, Whitelegge, Julian P, Rajasekaran, Sigrid A, Rajasekaran, Ayyappan K
• Format: Journal Article
• Language: English
• Published: United States The American Society for Cell Biology 01.03.2005
• Subjects: Actins - chemistry; Actins - metabolism; Animals; Annexin A2 - chemistry; Annexin A2 - genetics; Cell Line; Cell Movement; Chromatography, Liquid; Chromones - pharmacology; Cloning, Molecular; Cytoplasm - metabolism; Cytoskeleton; Dogs; Epithelial Cells - cytology; Glutathione Transferase - metabolism; Immunoblotting; Immunoprecipitation; Ions; Mass Spectrometry; Microscopy, Confocal; Microscopy, Fluorescence; Models, Biological; Morpholines - pharmacology; Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase - metabolism; Phalloidine - pharmacology; Phosphatidylinositol 3-Kinases - metabolism; Protein Binding; Protein Structure, Tertiary; rac1 GTP-Binding Protein - metabolism; Recombinant Fusion Proteins - metabolism; Signal Transduction; Sodium-Potassium-Exchanging ATPase - chemistry; Sodium-Potassium-Exchanging ATPase - physiology; Tight Junctions
• ISSN: 1059-1524; 1939-4586
• DOI: 10.1091/mbc.E04-05-0427

The Na,K-ATPase, consisting of alpha- and beta-subunits, regulates intracellular ion homeostasis. Recent studies have demonstrated that Na,K-ATPase also regulates epithelial cell tight junction structure and functions. Consistent with an important role in the regulation of epithelial cell structure, both Na,K-ATPase enzyme activity and subunit levels are altered in carcinoma. Previously, we have shown that repletion of Na,K-ATPase beta1-subunit (Na,K-beta) in highly motile Moloney sarcoma virus-transformed Madin-Darby canine kidney (MSV-MDCK) cells suppressed their motility. However, until now, the mechanism by which Na,K-beta reduces cell motility remained elusive. Here, we demonstrate that Na,K-beta localizes to lamellipodia and suppresses cell motility by a novel signaling mechanism involving a cross-talk between Na,K-ATPase alpha1-subunit (Na,K-alpha) and Na,K-beta with proteins involved in phosphatidylinositol 3-kinase (PI3-kinase) signaling pathway. We show that Na,K-alpha associates with the regulatory subunit of PI3-kinase and Na,K-beta binds to annexin II. These molecular interactions locally activate PI3-kinase at the lamellipodia and suppress cell motility in MSV-MDCK cells, independent of Na,K-ATPase ion transport activity. Thus, these results demonstrate a new role for Na,K-ATPase in regulating carcinoma cell motility.