Stimulation of membrane serine-threonine phosphatase in erythrocytes by hydrogen peroxide and staurosporine.
Indirect evidence has suggested that K-Cl cotransport in human and sheep erythrocytes is activated physiologically by a serine-threonine phosphatase. It is activated experimentally by H2O2 and by staurosporine, a kinase inhibitor. Activation by H2O2 and staurosporine is inhibited by serine-threonine phosphatase inhibitors, suggesting that the activators stimulate the phosphatase. The present study shows that sheep and human erythrocytes contain membrane-associated as well as cytosolic serine-threonine phosphatases, assayed from the dephosphorylation of 32P-labeled glycogen phosphorylase. In cells from both species, the relatively low sensitivity of the membrane enzyme to okadaic acid suggests it is type 1 protein phosphatase. The cytosolic phosphatase was much more sensitive to okadaic acid. Membrane-associated phosphatase was stimulated by both H2O2 and staurosporine. The results support earlier conclusions that the membrane-associated type 1 phosphatase identified here is regulated by phosphorylation and oxidation. The results are consistent with the phosphatase, or a portion of it, being responsible for activating K-Cl cotransport.
Bize
I
I
Department of Biology, Syracuse University, New York 13244, USA.
Muñoz
P
P
Canessa
M
M
Dunham
P B
PB
D000818:Animals; D002352:Carrier Proteins / Q000097:blood; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000201:enzymology; D004912:Erythrocytes / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D066298:In Vitro Techniques; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D012756:Sheep; D019311:Staurosporine / Q000494:pharmacology*; D027981:Symporters; D000096922:K Cl- Cotransporters
D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D006861:Hydrogen Peroxide; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases; D019311:Staurosporine; D027981:Symporters; D000096922:K Cl- Cotransporters