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.
Tilly
B C
BC
Department of Biochemistry, Medical Faculty, Erasmus University, Rotterdam, The Netherlands.
van den Berghe
N
N
Tertoolen
L G
LG
Edixhoven
M J
MJ
de Jonge
H R
HR
D016227:Benzoquinones; D002118:Calcium / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002460:Cell Line; D019833:Genistein; D006801:Humans; D007038:Hypotonic Solutions; D007422:Intestines; D007454:Iodides / Q000378:metabolism*; D007529:Isoflavones / Q000494:pharmacology; D007700:Kinetics; D047029:Lactams, Macrocyclic; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine; D011494:Protein Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011809:Quinones / Q000494:pharmacology; D017828:Rifabutin / Q000031:analogs & derivatives; D012413:Rubidium / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis; D014638:Vanadates / Q000494:pharmacology; D014882:Water-Electrolyte Balance
D016227:Benzoquinones; D007038:Hypotonic Solutions; D007454:Iodides; D007529:Isoflavones; D047029:Lactams, Macrocyclic; D010750:Phosphoproteins; D011809:Quinones; D017828:Rifabutin; D019000:Phosphotyrosine; D014638:Vanadates; D014443:Tyrosine; C020754:herbimycin; D019833:Genistein; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D012413:Rubidium; D002118:Calcium