Regulation of ground squirrel Na+K+-ATPase activity by reversible phosphorylation during hibernation

Biochem Biophys Res Commun. 1999 Jan 19;254(2):424-9. doi: 10.1006/bbrc.1998.9960.

Abstract

Maintenance of skeletal muscle energy status during hibernation in ground squirrels, Spermophilus lateralis, was accompanied by a decrease in Na+K+-ATPase pump activity. Energy charge was maintained (0.89) during hibernation at the expense of total adenylates (decreased by 41%). Muscle Na+K+-ATPase activity was 9.1 U/mg protein in euthermic controls but decreased by 60% during hibernation. Enzyme activity was similarly suppressed in vitro when extracts of control muscle were incubated with ATP plus second messengers of protein kinases A, G or C whereas stimulation of protein phosphatases in muscle extracts from hibernators increased Na+K+-ATPase activity. Additional studies confirmed that suppression and reactivation of the enzyme in euthermic muscle extracts can be achieved with protein kinase A and alkaline phosphatase treatments, respectively, and indicated that phosphorylation changes the ATP dependency of the enzyme. Thus, hibernation-induced suppression of Na+K+-ATPase activity in muscle and other organs of ground squirrels, which is a key part of the overall suppression of metabolic rate that constitutes torpor, appears to be regulated via reversible protein phosphorylation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine Nucleotides / metabolism
  • Adenosine Triphosphate / metabolism
  • Animals
  • Body Temperature
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Cyclic GMP-Dependent Protein Kinases
  • Energy Metabolism
  • Hibernation / physiology*
  • Inosine Monophosphate / metabolism
  • Kinetics
  • Muscle, Skeletal / enzymology*
  • Phosphoprotein Phosphatases / metabolism
  • Phosphorylation
  • Protein Kinase C / metabolism
  • Protein Kinases / metabolism
  • Sciuridae / physiology*
  • Second Messenger Systems
  • Sodium-Potassium-Exchanging ATPase / metabolism*

Substances

  • Adenine Nucleotides
  • Inosine Monophosphate
  • Adenosine Triphosphate
  • Protein Kinases
  • Cyclic AMP-Dependent Protein Kinases
  • Cyclic GMP-Dependent Protein Kinases
  • Protein Kinase C
  • Phosphoprotein Phosphatases
  • Sodium-Potassium-Exchanging ATPase