title: Disruption of cortical actin in skeletal muscle demonstrates an essential role of the cytoskeleton in glucose transporter 4 translocation in insulin-sensitive tissues.
abstract: Cell culture work suggests that signaling to polymerize cortical filamentous actin (F-actin) represents a required pathway for the optimal redistribution of the insulin-responsive glucose transporter, GLUT4, to the plasma membrane. Recent in vitro study further suggests that the actin-regulatory neural Wiskott-Aldrich syndrome protein (N-WASP) mediates the effect of insulin on the actin filament network. Here we tested whether similar cytoskeletal mechanics are essential for insulin-regulated glucose transport in isolated rat epitrochlearis skeletal muscle. Microscopic analysis revealed that cortical F-actin is markedly diminished in muscle exposed to latrunculin B. Depolymerization of cortical F-actin with latrunculin B caused a time- and concentration-dependent decline in 2-deoxyglucose transport. The loss of cortical F-actin and glucose transport was paralleled by a decline in insulin-stimulated GLUT4 translocation, as assessed by photolabeling of cell surface GLUT4 with Bio-LC-ATB-BMPA. Although latrunculin B impaired insulin-stimulated GLUT4 translocation and glucose transport, activation of phosphatidylinositol 3-kinase and Akt by insulin was not rendered ineffective. In contrast, the ability of insulin to elicit the cortical F-actin localization of N-WASP was abrogated. These data provide the first evidence that actin cytoskeletal mechanics are an essential feature of the glucose transport process in intact skeletal muscle. Furthermore, these findings support a distal actin-based role for N-WASP in insulin action in vivo.
authors.affiliation: Eli Lilly and Company, Indianapolis, Indiana 46285, USA. brozinick_joseph_t@lilly.com
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Brozinick
authors.forename: Eric D
authors.initials: ED
authors.lastname: Hawkins
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Strawbridge
authors.forename: Jeffrey S
authors.initials: JS
authors.lastname: Elmendorf
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry*; D003599:Cytoskeleton / Q000378:metabolism*; D003847:Deoxyglucose / Q000737:chemistry / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D008027:Light; D008297:Male; D018613:Microscopy, Confocal; D009004:Monosaccharide Transport Proteins / Q000378:metabolism / Q000502:physiology*; D009124:Muscle Proteins / Q000378:metabolism / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021381:Protein Transport; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017208:Rats, Wistar; D013844:Thiazoles / Q000737:chemistry*; D053778:Thiazolidines; D013997:Time Factors; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D003847:Deoxyglucose; D005947:Glucose; D051275:Glucose Transporter Type 4; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D013844:Thiazoles; D053778:Thiazolidines; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; C526296:Irs1 protein, rat; C495694:Slc2a4 protein, rat; C495770:Wasl protein, rat; C494920:Akt1 protein, rat; C037068:latrunculin B