Role of the AMPKgamma3 isoform in hypoxia-stimulated glucose transport in glycolytic skeletal muscle

Am J Physiol Endocrinol Metab. 2009 Dec;297(6):E1388-94. doi: 10.1152/ajpendo.00125.2009. Epub 2009 Oct 13.

Abstract

Skeletal muscle glucose transport is regulated via the canonical insulin-signaling cascade as well as by energy-sensing signals. 5'-AMP-activated protein kinase (AMPK) has been implicated in the energy status regulation of glucose transport. We determined the role of the AMPKgamma3 isoform in hypoxia-mediated energy status signaling and glucose transport in fast-twitch glycolytic extensor digitorum longus (EDL) muscle from AMPKgamma3-knockout (KO) mice and wild-type mice. Although hypoxia increased glucose transport (P < 0.001) in wild-type mice, this effect was attenuated in AMPKgamma3-KO mice (45% reduction, P < 0.01). The role of Ca(2+)-mediated signaling was tested using the Ca(2+)/calmodulin competitive inhibitor KN-93. KN-93 exposure reduced hypoxia-mediated glucose transport in AMPKgamma3-KO and wild-type mice (P < 0.05). To further explore the underlying signaling mechanisms, phosphorylation of CaMKII, AMPK, ACC, and TBC1D1/D4 as well as isoform-specific AMPK activity was determined. Basal and hypoxia-mediated phosphorylation of CaMKII, AMPK, and ACC as well as alpha1- and alpha2-associated AMPK activity was comparable between AMPKgamma3-KO and wild-type mice. KN-93 reduced hypoxia-mediated CaMKII phosphorylation in AMPKgamma3-KO and wild-type mice (P < 0.05), whereas phosphorylation of AMPK and ACC as well as alpha1- and alpha2-associated AMPK activity was unaltered. Hypoxia increased TBC1D1/D4 phosphorylation in AMPKgamma3-KO and wild-type mice (P < 0.001). KN-93 exposure prevented this effect in AMPKgamma3-KO, but not in wild-type mice. Taken together, we provide direct evidence for a role of the AMPKgamma3 isoform in hypoxia-mediated glucose transport in glycolytic muscle. Moreover, hypoxia-mediated TBC1D1/D4 phosphorylation was uncoupled from glucose transport in AMPKgamma3-KO mice, indicating that TBC1D1/D4-independent mechanisms contribute to glucose transport in skeletal muscle.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / metabolism*
  • Animals
  • Benzylamines / pharmacology
  • Biological Transport
  • Calcium / metabolism
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2 / metabolism
  • Cell Hypoxia / physiology
  • Female
  • GTPase-Activating Proteins
  • Glucose / metabolism*
  • Glucose Transport Proteins, Facilitative / metabolism*
  • Immunohistochemistry
  • In Vitro Techniques
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Muscle Fibers, Fast-Twitch / enzymology
  • Muscle Fibers, Fast-Twitch / metabolism*
  • Muscle, Skeletal / enzymology
  • Muscle, Skeletal / metabolism*
  • Nuclear Proteins / metabolism
  • Phosphorylation
  • Protein Kinase Inhibitors / pharmacology
  • Signal Transduction
  • Sulfonamides / pharmacology

Substances

  • Benzylamines
  • GTPase-Activating Proteins
  • Glucose Transport Proteins, Facilitative
  • Nuclear Proteins
  • Protein Kinase Inhibitors
  • Sulfonamides
  • Tbc1d1 protein, mouse
  • KN 93
  • Prkag3 protein, mouse
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • AMP-Activated Protein Kinases
  • Glucose
  • Calcium