Inhibition of Na+K+ATPase activity in membranes of Sindbis virus-infected chick cells.
Alterations in intracellular concentrations of Na+ and K+ in Sindbis virus-infected cells result largely from inhibition of ouabain-sensitive Na+K+ATPase (Na+ pump) activity. Here we report that membrane preparations derived from Sindbis virus-infected chick cells exhibit reduced Na+K+ATPase activity, indicating that limitation of cellular factors is not responsible for inhibition of ion transport. In vitro phosphorylation of the Na+K+ATPase by [32P]orthophosphate or [gamma 32P]ATP is unaltered in membranes of Sindbis virus-infected cells, indicating that a loss of specific enzymatic functions unrelated to formation of Na+ pump phosphoenzyme intermediates occurs during the course of viral infection. However, phosphoenzyme intermediates of the Na+K+ATPase prepared from membranes of Sindbis virus-infected cells are inherently less stable than those prepared with membranes of uninfected cells. The instability of these intermediates in vitro is correlated with an altered capacity of the Na+ pump to transport monovalent cations into virus-infected cells. 22Na+ transport studies reveal enhanced ouabain-sensitive Na+ uptake by Sindbis virus-infected cells, suggesting that the Na+ pump may catalyze enhanced Na+-Na+ exchange in the infected cells. These results indicate that the capacity of the Na+K+ATPase to discriminate between binding of extracellular Na+ and K+ is specifically altered during the course of infection by Sindbis virus.
Ulug
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ET
Section of Virology and Oncology, Kansas State University, Manhattan, 66506-4901, USA.
Garry
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RF
Bose
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HR
D002462:Cell Membrane / Q000201:enzymology; D002478:Cells, Cultured; D007700:Kinetics; D010042:Ouabain / Q000494:pharmacology; D010766:Phosphorylation; D012845:Sindbis Virus / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*
D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase