| First Author | Jensen TE | Year | 2015 |
| Journal | Biochem J | Volume | 467 |
| Issue | 3 | Pages | 461-72 |
| PubMed ID | 25695398 | Mgi Jnum | J:224566 |
| Mgi Id | MGI:5688260 | Doi | 10.1042/BJ20141142 |
| Citation | Jensen TE, et al. (2015) PT-1 selectively activates AMPK-gamma1 complexes in mouse skeletal muscle, but activates all three gamma subunit complexes in cultured human cells by inhibiting the respiratory chain. Biochem J 467(3):461-72 |
| abstractText | AMP-activated protein kinase (AMPK) occurs as heterotrimeric complexes in which a catalytic subunit (alpha1/alpha2) is bound to one of two beta subunits (beta1/beta2) and one of three gamma subunits (gamma1/gamma2/gamma3). The ability to selectively activate specific isoforms would be a useful research tool and a promising strategy to combat diseases such as cancer and Type 2 diabetes. We report that the AMPK activator PT-1 selectively increased the activity of gamma1- but not gamma3-containing complexes in incubated mouse muscle. PT-1 increased the AMPK-dependent phosphorylation of the autophagy-regulating kinase ULK1 (unc-51-like autophagy-activating kinase 1) on Ser555, but not proposed AMPK-gamma3 substrates such as Ser231 on TBC1 (tre-2/USP6, BUB2, cdc16) domain family, member 1 (TBC1D1) or Ser212 on acetyl-CoA carboxylase subunit 2 (ACC2), nor did it stimulate glucose transport. Surprisingly, however, in human embryonic kidney (HEK) 293 cells expressing human gamma1, gamma2 or gamma3, PT-1 activated all three complexes equally. We were unable to reproduce previous findings suggesting that PT-1 activates AMPK by direct binding between the kinase and auto-inhibitory domains (AIDs) of the alpha subunit. We show instead that PT-1 activates AMPK indirectly by inhibiting the respiratory chain and increasing cellular AMP:ATP and/or ADP:ATP ratios. Consistent with this mechanism, PT-1 failed to activate AMPK in HEK293 cells expressing an AMP-insensitive R299G mutant of AMPK-gamma1. We propose that the failure of PT-1 to activate gamma3-containing complexes in muscle is not an intrinsic feature of such complexes, but is because PT-1 does not increase cellular AMP:ATP ratios in the specific subcellular compartment(s) in which gamma3 complexes are located. |
