- Yan Y, Zhou XE, Novick SJ, Shaw SJ, Li Y, Brunzelle JS, Hitoshi Y, Griffin PR, Xu HE, Melcher K
- Structures of AMP-activated protein kinase bound to novel pharmacological activators in phosphorylated, non-phosphorylated, and nucleotide-free states.
- J Biol Chem. 2018 Nov 26. pii: RA118.004883. doi: 10.1074/jbc.RA118.004883.
- AMP-activated protein kinase (AMPK) is an attractive therapeutic target for managing metabolic diseases. A class of pharmacological activators, including Merck 991, binds the AMPK ADaM site, which forms the interaction surface between the kinase domain (KD) of the alpha subunit and the carbohydrate-binding module (CBM) of the beta subunit. Here, we report the development of two new 991-derivative compounds, R734 and R739, which potently activate AMPK in a variety of cell types, including beta2-specific skeletal muscle cells. Surprisingly, we found that they have only minor effects on direct kinase activity of the recombinant alpha1beta2gamma1 isoform, yet robustly enhance protection against activation loop dephosphorylation. This mode of activation is reminiscent of that of ADP, which activates AMPK by binding to the nucleotide-binding sites in the gamma subunit, more than 60 A away from the ADaM site. To understand the mechanisms of full and partial AMPK activation, we determined the crystal structures of fully active phosphorylated AMPK alpha1beta1gamma1 bound to AMP and R734/R739, as well as partially active non-phosphorylated AMPK bound to R734 and AMP, and phosphorylated AMPK bound to R734 in the absence of added nucleotides at < 3 A resolution. These structures and associated analyses identified a novel conformational state of the AMPK autoinhibitory domain associated with partial kinase activity and provide new insights into phosphorylation-dependent activation loop stabilization in AMPK.