Regulation of glycogen metabolism, muscle

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Regulation of glycogen metabolism, liver

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Contributors

Vasundra Touré, Luiz Ladeira, Tatiana Serebriyskaya, Valeriya Berzhitskaya, Alexander Mazein, John Albanese

Description

Intracellular glycogen stores contribute to blood-glucose homeostasis during fasting, provide energy for muscle contraction and support a broad range of cellular activities in many tissues. Glycogen synthase and glycogen phosphorylase control glycogen synthesis and breakdown, respectively. Glycogen phosphorylases, including the liver, muscle and brain forms PYGL, PYGM and PYGB, catalyse glycogen breakdown to glucose-1-phosphate.

The muscle map represents regulation through insulin signalling, adrenergic signalling and calcium-dependent activation of phosphorylase kinase. Epinephrine activates the ADRB2–Gs–adenylate cyclase–cAMP–PKA pathway, promoting phosphorylation and activation of muscle glycogen phosphorylase PYGM, while insulin signalling through PI3K–PDPK1–AKT1 regulates glycogen synthase through inhibition of GSK3B.

The liver map represents complementary regulation by insulin and glucagon. Glucagon signalling through GCGR activates the Gs–adenylate cyclase–cAMP–PKA pathway and promotes glycogen utilisation, whereas insulin signalling favours glycogen synthesis. In liver, the corresponding major metabolic enzymes are glycogen synthase GYS2 and glycogen phosphorylase PYGL.

References

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