AMP-activated protein kinase phosphorylates and inactivates liver glycogen synthase

Biochem J. 2012 Apr 1;443(1):193-203. doi: 10.1042/BJ20112026.

Abstract

Recombinant muscle GYS1 (glycogen synthase 1) and recombinant liver GYS2 were phosphorylated by recombinant AMPK (AMP-activated protein kinase) in a time-dependent manner and to a similar stoichiometry. The phosphorylation site in GYS2 was identified as Ser7, which lies in a favourable consensus for phosphorylation by AMPK. Phosphorylation of GYS1 or GYS2 by AMPK led to enzyme inactivation by decreasing the affinity for both UDP-Glc (UDP-glucose) [assayed in the absence of Glc-6-P (glucose-6-phosphate)] and Glc-6-P (assayed at low UDP-Glc concentrations). Incubation of freshly isolated rat hepatocytes with the pharmacological AMPK activators AICA riboside (5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside) or A769662 led to persistent GYS inactivation and Ser7 phosphorylation, whereas inactivation by glucagon treatment was transient. In hepatocytes from mice harbouring a liver-specific deletion of the AMPK catalytic α1/α2 subunits, GYS2 inactivation by AICA riboside and A769662 was blunted, whereas inactivation by glucagon was unaffected. The results suggest that GYS inactivation by AMPK activators in hepatocytes is due to GYS2 Ser7 phosphorylation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / chemistry
  • AMP-Activated Protein Kinases / metabolism*
  • Amino Acid Sequence
  • Aminoimidazole Carboxamide / analogs & derivatives
  • Aminoimidazole Carboxamide / pharmacology
  • Animals
  • Apraxia, Ideomotor
  • Biphenyl Compounds
  • Cells, Cultured
  • Consensus Sequence
  • Cyclic AMP-Dependent Protein Kinases / chemistry
  • Enzyme Activation / drug effects
  • Enzyme Activators / pharmacology
  • Glycogen Synthase / chemistry
  • Glycogen Synthase / metabolism*
  • Hepatocytes / drug effects
  • Hepatocytes / enzymology*
  • Hepatocytes / metabolism
  • Humans
  • Liver / cytology
  • Liver / enzymology*
  • Liver / metabolism
  • Male
  • Mice
  • Mice, Knockout
  • Phosphorylation
  • Protein Processing, Post-Translational*
  • Pyrones / pharmacology
  • Rats
  • Rats, Wistar
  • Ribonucleotides / pharmacology
  • Thiophenes / pharmacology

Substances

  • Biphenyl Compounds
  • Enzyme Activators
  • Pyrones
  • Ribonucleotides
  • Thiophenes
  • Aminoimidazole Carboxamide
  • Glycogen Synthase
  • Cyclic AMP-Dependent Protein Kinases
  • AMP-Activated Protein Kinases
  • AICA ribonucleotide
  • 4-hydroxy-3-(4-(2-hydroxyphenyl)phenyl)-6-oxo-7H-thieno(2,3-b)pyridine-5-carbonitrile