AMP-activated protein kinase (AMPK) plays a key role in integrating metabolic pathways in response to energy demand. AMPK activation results in a wide range of downstream responses, many of which are associated with improved metabolic outcome, making AMPK an attractive target for the treatment of metabolic diseases. AMPK is a heterotrimeric complex consisting of a catalytic subunit (α) and two regulatory subunits (β and γ). The γ subunit harbours the nucleotide binding sites and plays an important role in AMPK regulation in response to cellular energy levels. In mammals, there are 3 isoforms of the γ subunit and these respond differently to regulation by nucleotides, but there is limited information regarding their role in activation by small molecules. Here we determined the effect of different γ isoforms on AMPK by a direct activator, 991. In cells, 991 led to a greater activation of γ2-containing AMPK complexes compared to either γ1 or γ3. This effect was dependent on the long N-terminal region of the γ2 isoform. We were able to rule out an effect of Ser108 phosphorylation, since mutation of Ser108 to alanine in the β2 isoform had no effect on activation of AMPK by 991 in either γ1- or γ2-complexes. The rate of dephosphorylation of Thr172 was slower for γ2- compared to γ1-complexes, both in the absence or presence of 991. Our studies show that activation of AMPK by 991 depends on the nature of the γ isoform. This finding may have implications for the design of isoform-selective AMPK activators.
- protein-serine-threonine kinases
- metabolic regulation
- ©2017 The Author(s)
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