Reconstitution of calyculin-inhibited K-Cl cotransport in dog erythrocyte ghosts by exogenous PP-1.
Osmotic swelling of dog and other mammalian erythrocytes activates Cl-dependent K transport, K-Cl cotransport. This activation can be abolished by nanomolar concentrations of calyculin, a potent inhibitor of serine-threonine protein phosphatases. Therefore, K-Cl cotransport is probably activated by dephosphorylation by a type 1 and/or type 2A protein phosphatase (PP-1 and PP-2A, respectively). This was tested directly by incorporating exogenous protein phosphatases into resealed ghosts made from dog erythrocytes previously exposed to calyculin. K-Cl cotransport was nearly completely inhibited in the ghosts. Incorporation of PP-1 reconstituted K-Cl cotransport. Maximal reconstitution was up to 90% of the control flux in the ghosts and 0.1 U PP-1/ml lysate gave half-maximal reconstitution of cotransport. In contrast, PP-2A had no effect. This result with PP-1 provides direct evidence that K-Cl cotransport is activated by PP-1 in dog erythrocytes. Half-maximal activation of K-Cl cotransport required approximately 180 molecules of PP-1 per ghost.
Krarup
T
T
Department of Biology, Syracuse University, New York,13244-1220, USA.
Dunham
P B
PB
D000818:Animals; D002352:Carrier Proteins / Q000097:blood* / Q000187:drug effects; D002712:Chlorides / Q000097:blood / Q000494:pharmacology; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008387:Marine Toxins; D010080:Oxazoles / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011188:Potassium / Q000097:blood; D027981:Symporters; D000096922:K Cl- Cotransporters
D002352:Carrier Proteins; D002712:Chlorides; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; D010749:Phosphoprotein Phosphatases; D011188:Potassium; D027981:Symporters; D000096922:K Cl- Cotransporters; C059041:calyculin A