Activation of the sarcoplasmic reticulum Ca2+-ATPase induced by exercise

Deborah A. Ferrington, J. C. Reijneveld, P. R. Bär, Diana J. Bigelow

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Abstract

Prolonged exercise has been shown to cause disruption of intracellular calcium homeostasis in skeletal muscle, which is normally maintained by the sarcoplasmic reticulum (SR) Ca2+-ATPaSe. We have investigated the response of this enzyme to increased intracellular calcium levels by investigating the functional and physical characteristics of the SR Ca2+-ATPaSe and membrane lipids following 2 h of treadmill running and throughout a period of post-exercise recovery. The Ca2+-ATPaSe of SR membranes purified from exercised rats shows increases in enzymatic activity correlating with post-exercise recovery time. Corresponding increases in active Ca2+-ATPaSe pump units are observed, as measured by the concentration of phosphorylated enzyme intermediate formed from ATP. However, catalytic turnover rates of the Ca2+-ATPaSe are unchanged. Using spin-label electron paramagnetic resonance to assess both membrane fluidity and associations between individual Ca2+-ATPaSe polypeptide chains, we find no exercise-induced alterations in membrane dynamics which could explain the observed increases in Ca2+-ATPaSe activity. Nor do we find evidence for altered membrane purification as a result of exercise. We suggest that the cell responds to the challenge of increased cytosolic calcium levels by increasing the proportion of functional SR Ca2+-ATPase proteins in the membrane for the rapid restoration of calcium homeostasis.

Original languageEnglish (US)
Pages (from-to)203-213
Number of pages11
JournalBiochimica et Biophysica Acta - Biomembranes
Volume1279
Issue number2
DOIs
StatePublished - Mar 13 1996

Keywords

  • ATPase, Ca-
  • Calcium homeostasis
  • EPR
  • Exercise
  • Sarcoplasmic reticulum

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