Defining the mechanism of activation of AMP-activated protein kinase by the small molecule A-769662, a member of the thienopyridone family

AMP- activated protein kinase ( AMPK) plays a key role in maintaining energy homeostasis. Activation of AMPK in peripheral tissues has been shown to alleviate the symptoms of metabolic diseases, such as type 2 diabetes, and consequently AMPK is a target for treatment of these diseases. Recently, a small molecule activator ( A- 769662) of AMPK was identified that had beneficial effects on metabolism in ob/ ob mice. Here we show that A- 769662 activates AMPK both allosterically and by inhibiting dephosphorylation of AMPK on Thr- 172, similar to the effects of AMP. A- 769662 activates AMPK harboring a mutation in the gamma subunit that abolishes activation by AMP. An AMPK complex lacking the glycogen binding domain of the beta subunit abolishes the allosteric effect of A- 769662 but not the allosteric activation by AMP. Moreover, mutation of serine 108 to alanine, an autophosphorylation site within the glycogen binding domain of the 1 subunit, almost completely abolishes activation of AMPK by A-769662 in cells and in vitro, while only partially reducing activation by AMP. Based on our results we propose a model for activation of AMPK by A- 769662. Importantly, this model may provide clues for understanding the mechanism by which AMP leads to activation of AMPK, which in turn may help in the identification of other AMPK activators.