Insulin- and contraction-stimulated translocation of GTP-binding proteins and GLUT4 protein in skeletal muscle.
Low molecular weight GTP-binding proteins and GLUT4 protein were isolated in purified plasma membrane and low density microsome fractions from rat skeletal muscle. GTP-binding proteins were detected via the ability of these proteins to bind [32P]GTP subsequent to Western blotting. GLUT4 protein was detected via the anti-GLUT4 antibody F349 subsequent to Western blotting. The possible involvement of GTP-binding proteins in the regulation of GLUT4 protein movement was investigated by examining the subcellular distribution of GTP-binding proteins and GLUT4 protein under basal conditions and following stimulation by insulin or muscle contraction. Insulin stimulation caused a 111 +/- 34.8% increase in the plasma membrane content of GTP-binding proteins which was paralleled by a 74 +/- 19.1% increase in the plasma membrane content of GLUT4 protein. The insulin-stimulated increase in plasma membrane GTP-binding proteins and GLUT4 protein occurred coincident with 27 +/- 4.6 and 33 +/- 7.4% decreases, respectively, in the low density microsome content of these proteins. In addition, muscle contraction significantly increased the plasma membrane content of GTP-binding proteins (63 +/- 18.1%) and GLUT4 protein (67 +/- 22.2%). However, with muscle contraction the concentrations of GTP-binding proteins and GLUT4 protein were not altered in low density microsome fractions. The similar patterns with which the GTP-binding proteins and GLUT4 protein responded to stimulation by insulin and muscle contraction suggests a possible, but yet unidentified functional relationship between these proteins.
Department of Kinesiology, University of Texas, Austin 78712.
G J
GJ
Etgen
A R
AR
Memon
G A
GA
Thompson
J L
JL
Ivy
D000818:Animals; D001345:Autoradiography; D002250:Carbon Radioisotopes; D002462:Cell Membrane / Q000378:metabolism; D003847:Deoxyglucose / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006614:Hindlimb; D007328:Insulin / Q000494:pharmacology*; D008353:Mannitol / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000302:isolation & purification / Q000378:metabolism*; D009119:Muscle Contraction / Q000502:physiology*; D009124:Muscle Proteins; D009132:Muscles / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D010477:Perfusion; D010761:Phosphorus Radioisotopes; D051381:Rats; D011924:Rats, Zucker; D012584:Sciatic Nerve / Q000502:physiology; D014316:Tritium
D002250:Carbon Radioisotopes; D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D010761:Phosphorus Radioisotopes; C495694:Slc2a4 protein, rat; D014316:Tritium; D008353:Mannitol; D006160:Guanosine Triphosphate; D003847:Deoxyglucose; D019204:GTP-Binding Proteins; D005947:Glucose