Key result
Insulin suppresses ischemia-induced cardiac AMPK activation through hierarchical phosphorylation of Ser485/491.
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Previous studies showed that insulin antagonizes AMP-activated protein kinase activation by ischemia and that protein kinase B might be implicated. Here we investigated whether the direct phosphorylation of AMP-activated protein kinase by protein kinase B might participate in this effect. Protein kinase B phosphorylated recombinant bacterially expressed AMP-activated protein kinase heterotrimers at Ser(485) of the alpha1-subunits. In perfused rat hearts, phosphorylation of the alpha1/alpha2 AMP-activated protein kinase subunits on Ser(485)/Ser(491) was increased by insulin and insulin pretreatment decreased the phosphorylation of the alpha-subunits at Thr(172) in a subsequent ischemic episode. It is proposed that the effect of insulin to antagonize AMP-activated protein kinase activation involves a hierarchical mechanism whereby Ser(485)/Ser(491) phosphorylation by protein kinase B reduces subsequent phosphorylation of Thr(172) by LKB1 and the resulting activation of AMP-activated protein kinase.
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Horman et al. (2005) studied Ischemia. Insulin was evaluated on Phosphorylation of the alpha-subunits at Thr172 and Ser485/491. Insulin antagonized ischemia-induced AMPK activation in perfused rat hearts via hierarchical phosphorylation of Ser485/491, reducing subsequent Thr172 phosphorylation.
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