Regulation of Ca2+ handling by phosphorylation status in mouse fast- and slow-twitch skeletal muscle fibers |
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Authors: | Liu, Yewei Kranias, Evangelia G. Schneider, Martin F. |
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Abstract: | The effects ofphosphorylation status on Ca2+release and Ca2+ removal werestudied in fast-twitch flexor digitorum brevis and slow-twitch soleusskeletal muscle fibers enzymatically isolated from wild-type andphospholamban knockout (PLBko) mice. In all fibers the adenosine3',5'-cyclic monophosphate-dependent protein kinase (PKA)inhibitor H-89 decreased the peak amplitude of the intracellularCa2+ concentration([Ca2+]) transient fora single action potential, and the PKA activator dibutyryl adenosine3',5'-cyclic monophosphate (DBcAMP) reversed this effect,indicating modulation of Ca2+release by phosphorylation status in all fibers. H-89 decreased thedecay rate constant of the[Ca2+] transient andDBcAMP reversed this effect only in phospholamban-expressing fibers(wild-type soleus), indicating modulation ofCa2+ removal only in the presenceof phospholamban. A high basal level of PKA phosphorylation in soleusfibers maintained under our control conditions was indicated bythe lack of effect of direct application of DBcAMP onCa2+ release orCa2+ removal in wild-type or PLBkosoleus fibers and was confirmed by analysis of phospholamban fromwild-type soleus fibers. |
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