Control Of Glycogen Synthase

JBC paper
"Dual Regulation of Glycogen Synthase Kinase-3β by the α1A-Adrenergic Receptor".
The α1A-Adrenergic receptor cascade involves Gq, PLC, IP3, Ca+2 and diacyl glycerol. Ca+2 and diacyl glycerol activate PKC and PKC phosphorylates GSK3β (Glycogen Synthase Kinase -3β). The phosphorylated form of GSK3β is inactive and thus can not phosphorylate Glycogen Synthase (GS). This makes Glycogen Synthase more active and promotes glycogen synthesis; this is the opposite of what is in your book. The book gives a general statement that activation of PKC inhibits glycogen synthase.

After reading this journal article, the full story becomes clearer. The α1A-Adrenergic receptor has another pathway that does inhibit glycogen synthesis. The α1A-Adrenergic receptor cascade inactivates Akt (aka PKB). Akt is activated by the Insulin cascade: which is shown in the video and in the powerpoint slides. When Akt is inactivated by the α1A-Adrenergic receptor cascade, it does not phosphorylate GSK3β. The unphosphorylated form of GSK3β is active, it phosphorylates Glycogen Synthase to make GS less active. Catecholamines work against insulin by binding to the Gq coupled receptor that results in the inactivation of Akt (mechanism under study). This allows GSK3β to remain active and it phosphorylates and inactivates GS. The net result of catecholamines binding to the α1A-Adrenergic receptor is less glycogen synthesis, as stated (vaguely) in the text.

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