Possible CaMKK-dependent regulation of AMPK phosphorylation and glucose uptake at the onset of mild tetanic skeletal muscle contraction

• Published in: American journal of physiology: endocrinology and metabolism Vol. 292; no. 5; pp. E1308 - E1317
• Main Authors: Jensen, Thomas E, Rose, Adam J, Jorgensen, Sebastian B, Brandt, Nina, Schjerling, Peter, Wojtaszewski, Jorgen F. P, Richter, Erik A
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.05.2007
• Subjects: Aminoimidazole Carboxamide - analogs & derivatives; Aminoimidazole Carboxamide - pharmacology; Animals; Benzimidazoles - pharmacology; Benzylamines - pharmacology; Biochemistry; Calcium-Calmodulin-Dependent Protein Kinase Kinase; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Enzyme Activation - drug effects; Female; Glucose; Glucose - metabolism; Isoquinolines - pharmacology; Kinases; Mice; Mice, Inbred C57BL; Mice, Transgenic; Muscle Contraction - drug effects; Muscle Contraction - physiology; Muscle, Skeletal - enzymology; Muscle, Skeletal - metabolism; Muscle, Skeletal - physiology; Musculoskeletal system; Naphthalimides - pharmacology; Phosphorus; Phosphorylation - drug effects; Protein Kinase Inhibitors - pharmacology; Protein Kinases - metabolism; Protein-Serine-Threonine Kinases - metabolism; Proteins; Ribonucleotides - pharmacology; Sulfonamides - pharmacology
• ISSN: 0193-1849; 1522-1555
• DOI: 10.1152/ajpendo.00456.2006

1 Department of Human Physiology, Copenhagen Muscle Research Centre, Institute of Exercise and Sport Sciences, University of Copenhagen, Copenhagen; 2 Department of Molecular Muscle Biology, Copenhagen Muscle Research Centre, Rigshospitalet, Copenhagen; and 3 Department of Medical Biochemistry and Genetics, Medical Muscle Research Cluster, Molecular Muscle Biology, University of Copenhagen, Copenhagen, Denmark Submitted 29 August 2006 ; accepted in final form 8 January 2007 The Ca 2+ /calmodulin (CaM) competitive inhibitor KN-93 has previously been used to evaluate 5'-AMP-activated protein kinase (AMPK)-independent Ca 2+ -signaling to contraction-stimulated glucose uptake in muscle during intense electrical stimulation ex vivo. With the use of low-intensity tetanic contraction of mouse soleus and extensor digitorum longus (EDL) muscles ex vivo, this study demonstrates that KN-93 can potently inhibit AMPK phosphorylation and activity after 2 min but not 10 min of contraction while strongly inhibiting contraction-stimulated 2-deoxyglucose uptake at both the 2- and 10-min time points. These data suggest inhibition of Ca 2+ /CaM-dependent signaling events upstream of AMPK, the most likely candidate being the novel AMPK kinase CaM-dependent protein kinase kinase (CaMKK). CaMKK protein expression was detected in mouse skeletal muscle. Similar to KN-93, the CaMKK inhibitor STO-609 strongly reduced AMPK phosphorylation and activity at 2 min and less potently at 10 min. Pretreatment with STO-609 inhibited contraction-stimulated glucose uptake at 2 min in soleus, but not EDL, and in both muscles after 10 min. Neither KN-93 nor STO-609 inhibited 5-aminoimidazole-4-carboxamide-1- -4-ribofuranoside-stimulated glucose uptake, AMPK phosphorylation, or recombinant LKB1 activity, suggestive of an LKB1-independent effect. Finally, neither KN-93 nor STO-609 had effects on the reductions in glucose uptake seen in mice overexpressing a kinase-dead AMPK construct, indicating that the effects of KN-93 and STO-609 on glucose uptake require inhibition of AMPK activity. We propose that CaMKKs act in mouse skeletal muscle regulating AMPK phosphorylation and glucose uptake at the onset of mild tetanic contraction and that an intensity- and/or time-dependent switch occurs in the relative importance of AMPKKs during contraction. KN-93; STO-609; calmodulin kinase kinase Address for reprint requests and other correspondence: E. A. Richter, Dept. of Human Physiology, Institute of Exercise and Sport Sciences, Copenhagen Muscle Research Centre, Univ. of Copenhagen, Universitetsparken 13, Copenhagen 2100, Denmark (e-mail: ERichter{at}ifi.ku.dk )