A myosin II ATPase inhibitor reduces force production, glucose transport, and phosphorylation of AMPK and TBC1D1 in electrically stimulated rat skeletal muscle.
Contraction-stimulated glucose transport by skeletal muscle appears to be caused by the cumulative effects of multiple inputs [potentially including AMP-activated protein kinase (AMPK), Ca(2+) flux, and force production], making it challenging to isolate the roles of these putative regulatory factors. To distinguish the effects of force production from the direct consequences of Ca(2+) flux, the predominantly type II rat epitrochlearis muscle was incubated without (vehicle) or with N-benzyl-p-toluenesulfonamide (BTS), a highly specific myosin II ATPase inhibitor that prevents force production by electrically stimulated (ES) type II fibers without altering cytosolic Ca(2+). In ES muscles, BTS vs. vehicle had an 84% reduction in force production and a 57% decrement in contraction-stimulated 3-O-methylglucose transport (3MGT). BTS did not alter the ES increase in phosphorylation of CaMKII (indicative of cytosolic Ca(2+)) or the amount of glycogen depletion. ES caused significant reductions in ATP (48%) and phosphocreatine (67%) concentrations for vehicle-treated muscles. For BTS-treated muscles, ES did not reduce ATP and caused only a 42% decrease in phosphocreatine. There was an ES increase in phosphorylation of AMPK, acetyl-CoA carboxylase (an AMPK substrate), and TBC1D1 for vehicle-treated muscles but not for BTS-treated muscles. These results point toward an essential role for tension-related events, including AMPK activation, in the 57% contraction-stimulated increase in 3MGT that was inhibited by BTS and further suggest a possible role for TBC1D1 phosphorylation. Non-tension-related events (e.g., increased cytosolic Ca(2+) rather than increased AMPK and TBC1D1 phosphorylation) are implicated in the contraction-stimulated increase in 3MGT that persisted in the presence of BTS.
Blair
David R
DR
University of Michigan, Division of Kinesiology, Ann Arbor, MI 48109-2214, USA.
Funai
Katsuhiko
K
Schweitzer
George G
GG
Cartee
Gregory D
GD
D019325:3-O-Methylglucose / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000263:Adenylate Kinase / Q000378:metabolism*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006003:Glycogen / Q000378:metabolism; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology; D015151:Immunoblotting; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D009218:Myosins / Q000037:antagonists & inhibitors; D010725:Phosphocreatine / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012265:Ribonucleotides / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology*; D014050:Toluene / Q000031:analogs & derivatives* / Q000494:pharmacology
D004791:Enzyme Inhibitors; D007004:Hypoglycemic Agents; C444880:N-benzyl-p-toluene sulfonamide; D011506:Proteins; D012265:Ribonucleotides; D013449:Sulfonamides; C540572:TBC1D1 protein, rat; D010725:Phosphocreatine; D019325:3-O-Methylglucose; D000620:Aminoimidazole Carboxamide; D014050:Toluene; D000255:Adenosine Triphosphate; D006003:Glycogen; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D038362:Glycogen Synthase Kinase 3; D000263:Adenylate Kinase; D009218:Myosins; C031143:AICA ribonucleotide