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 AMPKγ3 isoform in hypoxia-mediated energy status signaling and glucose transport. Isolated mouse fast-twitch glycolytic extensor digitorum longus (EDL) muscle from AMPKγ3 knock-out (KO) mice and wild-type littermates were incubated under basal or hypoxic conditions. While hypoxia increased glucose transport (P<0.001) in wild-type mice, this effect was attenuated in AMPKγ3 KO mice (45% reduction P<0.01). The role of Ca2+-mediated signaling was tested using the Ca2+/calmodulin competitive inhibitor, KN-93. Hypoxia-mediated glucose transport in AMPKγ3 KO and wild-type mice was reduced in the presence of KN-93 (P<0.05). To further explore underlying signaling mechanisms, phosphorylation of AMPK, ACC and AS160 was determined under basal and hypoxic conditions, in the absence or presence of KN-93. Basal and hypoxia-mediated AMPK and ACC phosphorylation was comparable between AMPKγ3 KO and wild-type mice and these responses were unaltered by KN-93. Hypoxia also increased AS160 phosphorylation in AMPKγ3 KO and wild-type mice (P<0.001). KN-93 exposure prevented the hypoxia-mediated increase in AS160 phosphorylation in AMPKγ3 KO mice, but not in wild-type mice. Taken together, we provide direct evidence for a role of the AMPKγ3 isoform in hypoxia-mediated glucose transport in glycolytic muscle. Moreover, hypoxia-mediated AS160 phosphorylation was uncoupled from glucose transport in AMPKγ3 KO mice, indicating AS160-independent mechanisms contribute to glucose transport in skeletal muscle.
- Signal Transduction
- Glucose Metabolism
- Copyright © 2009, American Journal of Physiology - Endocrinology and Metabolism