Role of protein phosphorylation in control of K flux pathways of trout red blood cells.
The role of protein phosphatases in the regulation of K flux pathways of the trout red blood cell has been investigated using the phosphatase inhibitors calyculin A and okadaic acid. Both inhibitors completely blocked an oxygenation-activated Cl-dependent K flux with a 50% inhibitory concentration of 17 and 675 nmol/l, respectively, but not the hypotonically activated Cl-independent K uptake. N-ethylmaleimide (NEM) and staurosporine caused an increase in the Cl-dependent flux. In both cases preincubation with calyculin A blocked activation but, when added during activation, it prevented any further increase with NEM but abolished the staurosporine-induced uptake. K uptake that was activated by NEM and "clamped" by calyculin A was volume sensitive, indicating a dual influence on this pathway. Chelerythrine, a protein kinase inhibitor, activated a Cl-independent K uptake that was unaffected by calyculin A. It is concluded that activation and deactivation of both Cl-dependent and Cl-independent pathways require changes in the phosphorylation of an as yet unidentified target protein(s), although with different sets of protein kinase and/or phosphatases. These observations also suggest a complex model of kinase-phosphatase regulation and provide drugs for the pharmacological definition and manipulation of Cl-dependent and Cl-independent K flux pathways.
Cossins
A R
AR
Department of Environmental and Evolutionary Biology, University of Liverpool, United Kingdom.
Weaver
Y R
YR
Lykkeboe
G
G
Nielsen
O B
OB
D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D002352:Carrier Proteins / Q000502:physiology; D004912:Erythrocytes / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D010617:Phenanthridines / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000502:physiology*; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism*; D011493:Protein Kinase C / Q000502:physiology; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000502:physiology*; D011506:Proteins / Q000378:metabolism; D027981:Symporters; D014337:Trout; D000096922:K Cl- Cotransporters
D000470:Alkaloids; D053119:Benzophenanthridines; D002352:Carrier Proteins; D005033:Ethylmaleimide; D010617:Phenanthridines; D010749:Phosphoprotein Phosphatases; D011188:Potassium; D011493:Protein Kinase C; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D011506:Proteins; D027981:Symporters; D000096922:K Cl- Cotransporters; C016299:chelerythrine