Protein tyrosine phosphorylation is involved in osmoregulation of ionic conductances
Using the human Intestine 407 cell line as a model, we investigated a possible role for tyrosine kinase(s) in regulating the ion efflux pathways induced by hyposmotic stimulation (regulatory volume decrease, RVD). Pretreatment of 125I(-)-and 86Rb(+)-loaded cells with the phosphotyrosine phosphatase inhibitor sodium orthovanadate (200 microM) potentiated isotope efflux triggered by mild hypotonicity (10-20%) but did not further increase the efflux in response to more vigorous osmotic stimulation (30% hypotonicity). The tyrosine kinase inhibitors herbimycin A and genistein largely reduced the osmoshock-induced efflux in both control and vanadate-pretreated cells, while not affecting calcium-activated 86Rb+ efflux. Potentiation of the RVD response by vanadate was confirmed by direct measurements of hypotonicity-induced changes in cell volume. Hypotonic shock alone triggered a rapid and transient increase in tyrosine phosphorylation of several proteins as well as phosphorylation of mitogen-activated protein kinase. Furthermore, the potentiating effects of vanadate on hypotonicity-induced ion efflux and mitogen-activated protein (MAP) kinase phosphorylation were mimicked by epidermal growth factor. Neither vanadate nor epidermal growth factor provoked a RVD-like ionic response under isotonic conditions. These results indicate that tyrosine phosphorylation is an essential step in the RVD response and suggest a novel role of growth factors in the cellular defense against osmotic stress.
|Keywords||*Water-Electrolyte Balance, Benzoquinones, Ca(2+)-Calmodulin Dependent Protein Kinase, Calcium/metabolism, Cell Line, Genistein, Humans, Hypotonic Solutions, Intestines, Iodides/*metabolism, Isoflavones/pharmacology, Kinetics, Lactams, Macrocyclic, Phosphoproteins/isolation & purification/*metabolism, Phosphorylation, Phosphotyrosine, Protein Kinases/metabolism, Protein-Tyrosine Kinases/antagonists & inhibitors/*metabolism, Quinones/pharmacology, Rubidium/*metabolism, Tyrosine/analogs & derivatives/analysis, Vanadates/pharmacology|
Tilly, B.C., van den Berghe, N., Tertoolen, L.G., Edixhoven, M.J., & de Jonge, H.R.. (1993). Protein tyrosine phosphorylation is involved in osmoregulation of ionic conductances. Journal of Biological Chemistry. Retrieved from http://hdl.handle.net/1765/8548