title: Possible CaMKK-dependent regulation of AMPK phosphorylation and glucose uptake at the onset of mild tetanic skeletal muscle contraction.
abstract: 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-beta-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.
authors.affiliation: Department of Human Physiology, Copenhagen Muscle Research Centre, Institute of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Jensen
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Rose
authors.forename: Sebastian B
authors.initials: SB
authors.lastname: Jørgensen
authors.forename: Nina
authors.initials: N
authors.lastname: Brandt
authors.forename: Peter
authors.initials: P
authors.lastname: Schjerling
authors.forename: Jørgen F P
authors.initials: JF
authors.lastname: Wojtaszewski
authors.forename: Erik A
authors.initials: EA
authors.lastname: Richter
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology; D001596:Benzylamines / Q000494:pharmacology; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005947:Glucose / Q000378:metabolism*; D007546:Isoquinolines / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D018482:Muscle, Skeletal / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D053644:Naphthalimides / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012265:Ribonucleotides / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D000096926:Benzenesulfonamides
chemical_list: D000091162:AMP-Activated Protein Kinase Kinases; D000620:Aminoimidazole Carboxamide; D001562:Benzimidazoles; D001596:Benzylamines; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D005947:Glucose; D007546:Isoquinolines; D053644:Naphthalimides; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D012265:Ribonucleotides; D013449:Sulfonamides; C458525:STO 609; C072105:KN 93; D000096926:Benzenesulfonamides; C031143:AICA ribonucleotide