Regulation of Ca2+ handling by phosphorylation status in mouse fast- and slow-twitch skeletal muscle fibers.
The effects of phosphorylation status on Ca2+ release and Ca2+ removal were studied in fast-twitch flexor digitorum brevis and slow-twitch soleus skeletal muscle fibers enzymatically isolated from wild-type and phospholamban knockout (PLBko) mice. In all fibers the adenosine 3',5'-cyclic monophosphate-dependent protein kinase (PKA) inhibitor H-89 decreased the peak amplitude of the intracellular Ca2+ concentration ([Ca2+]) transient for a single action potential, and the PKA activator dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP) reversed this effect, indicating modulation of Ca2+ release by phosphorylation status in all fibers. H-89 decreased the decay rate constant of the [Ca2+] transient and DBcAMP reversed this effect only in phospholamban-expressing fibers (wild-type soleus), indicating modulation of Ca2+ removal only in the presence of phospholamban. A high basal level of PKA phosphorylation in soleus fibers maintained under our control conditions was indicated by the lack of effect of direct application of DBcAMP on Ca2+ release or Ca2+ removal in wild-type or PLBko soleus fibers and was confirmed by analysis of phospholamban from wild-type soleus fibers.
Liu
Y
Y
Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore 21201, USA.
Kranias
E G
EG
Schneider
M F
MF
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000251:Adenosine Triphosphatases / Q000502:physiology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000172:deficiency / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D018656:Muscle Fibers, Fast-Twitch / Q000187:drug effects / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010766:Phosphorylation; D013449:Sulfonamides; D000099211:Phospholamban
D000251:Adenosine Triphosphatases; D003994:Bucladesine; D002118:Calcium; D002135:Calcium-Binding Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; D004791:Enzyme Inhibitors; D007546:Isoquinolines; D013449:Sulfonamides; D000099211:Phospholamban; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide