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

TY - JOUR

T1 - Role of the AMPKgamma3 isoform in hypoxia-stimulated glucose transport in glycolytic skeletal muscle

AU - Deshmukh, Atul S

AU - Glund, Stephan

AU - Tom, Robby Z

AU - Zierath, Juleen R

PY - 2009/12

Y1 - 2009/12

N2 - 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.

AB - 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.

KW - AMP-Activated Protein Kinases

KW - Animals

KW - Benzylamines

KW - Biological Transport

KW - Calcium

KW - Calcium-Calmodulin-Dependent Protein Kinase Type 2

KW - Cell Hypoxia

KW - Female

KW - GTPase-Activating Proteins

KW - Glucose

KW - Glucose Transport Proteins, Facilitative

KW - Immunohistochemistry

KW - In Vitro Techniques

KW - Male

KW - Mice

KW - Mice, Inbred C57BL

KW - Mice, Knockout

KW - Muscle Fibers, Fast-Twitch

KW - Muscle, Skeletal

KW - Nuclear Proteins

KW - Phosphorylation

KW - Protein Kinase Inhibitors

KW - Signal Transduction

KW - Sulfonamides

KW - Journal Article

KW - Research Support, Non-U.S. Gov't

U2 - 10.1152/ajpendo.00125.2009

DO - 10.1152/ajpendo.00125.2009

M3 - Journal article

C2 - 19826102

SN - 0193-1849

VL - 297

SP - E1388-94

JO - American Journal of Physiology: Endocrinology and Metabolism

JF - American Journal of Physiology: Endocrinology and Metabolism

IS - 6

ER -