Regulation of glycogen synthase in skeletal muscle during exercise.
Glycogen synthase (GS) catalyses the incorporation of uridine diphosphate-glucose into glycogen in skeletal muscle. In concert with the glucose transport step, GS activity is thought to be rate-limiting in the disposal of glucose as muscle glycogen. Glycogen synthase is regulated by both allosteric factors (primarily glucose 6-phosphate) and covalent modification by reversible phosphorylation and dephosphorylation leading to inactivation and activation of GS, respectively. Exercise activates both stimulatory and inhibitory regulators of GS and it is thought that the resultant activity of GS during exercise depends on the relative strength of opposing signals. However, the mechanisms by which exercise regulates GS activity are not fully understood. Glycogen breakdown, the GM-protein phosphatase 1 complex and possibly cellular relocalization of GS may be considered important factors involved in the stimulation of GS activity during exercise, while adenosine monophosphate-activated protein kinase and plasma adrenaline (via protein kinase A) can be considered as essential for the exercise-induced inhibitory signals to GS.
Nielsen
J N
JN
Department of Human Physiology, Copenhagen Muscle Research Centre, Institute of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark. jnnielsen@aki.dk
Richter
E A
EA
D055372:AMP-Activated Protein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D019298:Glucose-6-Phosphate / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D006006:Glycogen Synthase / Q000378:metabolism*; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D006801:Humans; D009097:Multienzyme Complexes / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism
D009097:Multienzyme Complexes; D019298:Glucose-6-Phosphate; D006003:Glycogen; D006006:Glycogen Synthase; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3; D055372:AMP-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D005947:Glucose