title: Electrical stimuli release ATP to increase GLUT4 translocation and glucose uptake via PI3Kγ-Akt-AS160 in skeletal muscle cells.
abstract: Skeletal muscle glucose uptake in response to exercise is preserved in insulin-resistant conditions, but the signals involved are debated. ATP is released from skeletal muscle by contractile activity and can autocrinely signal through purinergic receptors, and we hypothesized it may influence glucose uptake. Electrical stimulation, ATP, and insulin each increased fluorescent 2-NBD-Glucose (2-NBDG) uptake in primary myotubes, but only electrical stimulation and ATP-dependent 2-NBDG uptake were inhibited by adenosine-phosphate phosphatase and by purinergic receptor blockade (suramin). Electrical stimulation transiently elevated extracellular ATP and caused Akt phosphorylation that was additive to insulin and inhibited by suramin. Exogenous ATP transiently activated Akt and, inhibiting phosphatidylinositol 3-kinase (PI3K) or Akt as well as dominant-negative Akt mutant, reduced ATP-dependent 2-NBDG uptake and Akt phosphorylation. ATP-dependent 2-NBDG uptake was also inhibited by the G protein βγ subunit-interacting peptide βark-ct and by the phosphatidylinositol 3-kinase-γ (PI3Kγ) inhibitor AS605240. ATP caused translocation of GLUT4myc-eGFP to the cell surface, mechanistically mediated by increased exocytosis involving AS160/Rab8A reduced by dominant-negative Akt or PI3Kγ kinase-dead mutants, and potentiated by myristoylated PI3Kγ. ATP stimulated 2-NBDG uptake in normal and insulin-resistant adult muscle fibers, resembling the reported effect of exercise. Hence, the ATP-induced pathway may be tapped to bypass insulin resistance.
authors.affiliation: Center for Molecular Studies of the Cell, Biomedical Sciences Institute, Universidad de Chile, Santiago, Chile.
authors.forename: Cesar
authors.initials: C
authors.lastname: Osorio-Fuentealba
authors.forename: Ariel E
authors.initials: AE
authors.lastname: Contreras-Ferrat
authors.forename: Francisco
authors.initials: F
authors.lastname: Altamirano
authors.forename: Alejandra
authors.initials: A
authors.lastname: Espinosa
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.forename: Wenyan
authors.initials: W
authors.lastname: Niu
authors.forename: Sergio
authors.initials: S
authors.lastname: Lavandero
authors.forename: Amira
authors.initials: A
authors.lastname: Klip
authors.forename: Enrique
authors.initials: E
authors.lastname: Jaimovich
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D002478:Cells, Cultured; D058544:Class Ib Phosphatidylinositol 3-Kinase / Q000737:chemistry / Q000378:metabolism*; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020690:GTPase-Activating Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018482:Muscle, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D050505:Mutant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D004791:Enzyme Inhibitors; D020690:GTPase-Activating Proteins; D051275:Glucose Transporter Type 4; D050505:Mutant Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011993:Recombinant Fusion Proteins; C518767:TBC1D4 protein, human; D000255:Adenosine Triphosphate; D058544:Class Ib Phosphatidylinositol 3-Kinase; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose