Ouabain Binding to Na+,K+-ATPase Relaxes Cell Attachment and Sends a SpecificSignal (NACos) to the Nucleus

Abstract

Abstract. In previous work we described a "P-->A mechanism" that transduces occupancy of the pump ( P) by ouabain into changes in phosphorylation, stimulation of mitogen-activated protein kinase (MAPK), and endocytosis of cell-cell- and cell-substrate-attaching molecules ( A), thereby causing a release of the cell from the monolayer. In the present work we try to understand the mechanism of this effect; whether, in order to trigger the P-->A mechanism, ouabain should block the pumping activity of Na(+),K(+)-ATPase as pump, or whether it would suffice that the drug occupies this enzyme as a receptor. We assay a series of drugs known to act on the pump, such as ouabain, digoxin, digitoxin, palytoxin, oligomycin, strophanthidin, neothyoside-A, proscillaridin-A, etc. We gauge their ability to block the pump by measuring the K(+) content in the cells, and their ability to detach the cells from the monolayer by determining the amount of protein remaining in the culturing well. None of the drugs tested was able to cause detachment without stopping the pump. Ouabain also enhances phosphorylation, yet pump inhibition and signal transduction do not seem to be intimately associated in a causal chain, but to occur simultaneously. To investigate the response of the site of cell attachment, we analyze the position of beta-catenin by fluorescence confocal microscopy, and find that this adherent junction-associated molecule is sent to the nucleus, where it is known to act as a transcriptional cofactor.

Na/K-ATPase Mimetic pNaKtide Peptide Inhibits the Growth of Human Cancer Cells

“…First, the down-regulation of ␣1 Na/K-ATPase might make it less effective for Na/K-ATPase to interact with and then inhibit cellular Src. This would increase basal Src and FAK activity and consequently promote epithelial cell proliferation, migration, and invasion (34,38,39). Consistently, we found that metastatic prostate cancer cells are highly sensitive to the addition of the Na/K-ATPase ␣1 mimetics, including ND1 (supplemental Fig.…”

The cardiotonic steroid hormone marinobufagenin induces renal fibrosis: implication of epithelial-to-mesenchymal transition

“…Cell detachment and ␤-catenin translocation to the nucleus in the presence of 1 M of ouabain were shown recently in MDCK cells. The authors did not report whether MDCK cells in these experiments underwent EMT (12,37). Another study showed that a concentration of 1 M ouabain was toxic for MDCK cells (1).…”

Cardiac Glycosides Regulate Endothelial Tissue Factor Expression in Culture

“…22,29,30 The effect on TF expression preceded these morphological changes. A nonspecific action of cardiac glycosides on cell viability can be excluded, as LDH release was not enhanced; moreover, ouabain (10 Ϫ7 mol/L) is known to exert an antiapoptotic effect on human umbilical vein endothelial cells, 31 and to reduce VSMC death during up to 30 hours of treatment (10 Ϫ3 mol/L).…”