title: Rab11 is associated with GLUT4-containing vesicles and redistributes in response to insulin.
abstract: OBJECTIVE
  To identify a GTPase of 24,000 M(r) which we recently found to co-localize with GLUT4 in cardiac muscle.
  
  
  METHODS
  A 24,000 M(r)-GTP-binding fraction was purified from pig heart by a three-step chromatographic procedure, followed by two-dimensional electrophoresis and electrospray ionization-mass spectrometry. Subcellular distribution of the GTPase was assessed by western blotting. Co-localization with GLUT4 was assessed by continuous sucrose density gradient fractionation and immunoadsorption of GLUT4-containing vesicles.
  
  
  RESULTS
  The Rab11 protein was identified as a major component of the GTP-binding fraction and its expression in rat cardiac muscle was confirmed. In vivo insulin treatment resulted in the recruitment of Rab11 from the microsomal fraction to the plasma membrane. Subcellular fractionation indicated two immunoreactive GLUT4 pools. Most of the intracellular pool of Rab11 overlapped with the high-density GLUT4 pool and most of the transferrin receptor pool. The Rab11 protein also co-sedimented with the low-density, non-endosomal GLUT4 pool and substantially increased in this fraction after insulin treatment. It was specifically present in GLUT4-containing vesicles and insulin increased its abundance in these vesicles 2.2-fold relative to the amount of GLUT4. These vesicles also containend Rab4 and Akt-2, the latter being only associated after insulin stimulation. Insulin was unable to alter the cellular localization of Rab11 in insulin-resistant obese Zucker rats.
  
  
  CONCLUSIONS
  These results support the hypothesis that at least two GTPases of the Rab family participate in GLUT4-vesicle trafficking. We suggest that Rab11 is involved in the endosomal recycling, sorting and exocytotic movement of the glucose transporter.
authors.affiliation: Molecular Cardiology, Diabetes Research Institute, Düsseldorf, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Kessler
authors.forename: E
authors.initials: E
authors.lastname: Tomas
authors.forename: D
authors.initials: D
authors.lastname: Immler
authors.forename: H E
authors.initials: HE
authors.lastname: Meyer
authors.forename: A
authors.initials: A
authors.lastname: Zorzano
authors.forename: J
authors.initials: J
authors.lastname: Eckel
mesh_terms: D000818:Animals; D002458:Cell Fractionation; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D051275:Glucose Transporter Type 4; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006352:Heart Ventricles; D007328:Insulin / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000378:metabolism; D008297:Male; D008861:Microsomes / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D009206:Myocardium / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D011924:Rats, Zucker; D021241:Spectrometry, Mass, Electrospray Ionization; D013552:Swine; D020691:rab GTP-Binding Proteins / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D000099193:rab11 GTP-Binding Proteins
chemical_list: D051275:Glucose Transporter Type 4; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C495694:Slc2a4 protein, rat