Long-chain acyl-CoA esters inhibit phosphorylation of AMP-activated protein kinase at threonine-172 by LKB1/STRAD/MO25

Am J Physiol Endocrinol Metab. 2005 Jun;288(6):E1055-61. doi: 10.1152/ajpendo.00516.2004. Epub 2005 Jan 11.

Abstract

Activation of the AMP-activated protein kinase (AMPK) results in acute changes in cellular metabolism and transcriptional events that make the cell more robust when encountering an energy challenge. AMPK is thought to be inhibited by glycogen, the major storage form of intracellular carbohydrate. We hypothesized that long-chain acyl-CoA esters (LCACEs) might also inhibit AMPK signaling. Cytosolic LCACEs are available for immediate transport and oxidation within the mitochondria and accordingly may be representative of the lipid energy charge of the cell. We found that LCACEs inhibited phosphorylation of AMPK by the recombinant AMPK kinase (AMPKK) LKB1/STRAD/MO25 in a concentration-dependent manner. Palmitoyl-CoA (PCoA) did not affect the activity of phosphothreonine-172 AMPK. PCoA potently inhibited AMPKK purified from liver. Conversely, PCoA stimulated the kinase activity of LKB1/STRAD/MO25 toward the peptide substrate LKB1tide. Octanoyl-CoA, palmitate, and palmitoylcarnitine did not inhibit AMPKK activity. Removal of AMP from the reaction mixture resulted in reduced AMPKK activity in the presence of PCoA. In conclusion, these results demonstrate that the AMPKK activity of LKB1/STRAD/MO25 is substrate specific and distinct from the kinase activity of LKB1/STRAD/MO25 toward the peptide substrate LKB1tide. They also demonstrate that LCACEs inhibit the AMPKK activity of LKB1/STRAD/MO25 in a specific manner with a dependence on both a long fatty chain and a CoA moiety. These results suggest that the AMPK signaling cascade may directly sense and respond to the lipid energy charge of the cell.

MeSH terms

  • AMP-Activated Protein Kinase Kinases
  • AMP-Activated Protein Kinases
  • Acyl Coenzyme A / pharmacology
  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Blotting, Western
  • Coenzyme A / pharmacology*
  • Liver / metabolism*
  • Male
  • Malonyl Coenzyme A / pharmacology
  • Multienzyme Complexes / antagonists & inhibitors
  • Multienzyme Complexes / metabolism*
  • Phosphorylation / drug effects
  • Phosphothreonine / metabolism
  • Protein Kinases / metabolism*
  • Protein Serine-Threonine Kinases / antagonists & inhibitors*
  • Protein Serine-Threonine Kinases / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Recombinant Proteins / metabolism
  • Threonine / metabolism

Substances

  • Acyl Coenzyme A
  • Adaptor Proteins, Signal Transducing
  • Multienzyme Complexes
  • Recombinant Proteins
  • Phosphothreonine
  • acetoacetyl CoA
  • Threonine
  • Malonyl Coenzyme A
  • Protein Kinases
  • Protein Serine-Threonine Kinases
  • Stk11 protein, rat
  • AMP-Activated Protein Kinase Kinases
  • AMP-Activated Protein Kinases
  • Coenzyme A