The hypothesis of the present study was that exposure of differentiated muscle cells to AMPK agonists would increase the mRNA content of the muscle-specific ubiquitin ligases MAFbx and MuRF1. C₂C₁₂ cells were incubated with incremental doses of AICAR or metformin for 24 hours. Both MAFbx and MuRF1 mRNA increased dose-dependently in response to these treatments. AICAR, metformin, or 2-deoxy-D-glucose produced time-dependent alterations in ubiquitin ligase expression, typified by a biphasic pattern marked by an acute repression followed by a sustained induction. AMPK-activating treatments in conjunction with dexamethasone produced a pronounced synergistic effect on ligase mRNA expression at later time points. This response occurred in the absence of a dexamethasone-dependent increase in AMPK expression or activity, as determined by phosphorylation and expression of AMPK and its downstream target ACC. These responses elicited by AMPK activation singly or in combination with dexamethasone did not extend to the mRNA expression of the UBR box E3s UBR1/E3I and UBR2/E3II. Treatment with the AMPK inhibitor Compound C prevented increases in MAFbx and MuRF1 mRNA in response to serum deprivation as well as AICAR and dexamethasone treatment individually or jointly. Stimulation of AMPK activity in vivo via AICAR injection increased both MAFbx and MuRF1 mRNA in murine skeletal muscle. These data suggest activation of AMPK in skeletal muscle results in a specific upregulation of MAFbx and MuRF1 - responses which are reminiscent of the proposed atrophic transcriptional program. Therefore AMPK may be a critical component of the intercalated network of signaling pathways governing skeletal muscle atrophy.