title: β(2)-Adrenoceptors increase translocation of GLUT4 via GPCR kinase sites in the receptor C-terminal tail.
abstract: OBJECTIVE
  β-Adrenoceptor stimulation induces glucose uptake in several insulin-sensitive tissues by poorly understood mechanisms.
  
  
  METHODS
  We used a model system in CHO-K1 cells expressing the human β(2)-adrenoceptor and glucose transporter 4 (GLUT4) to investigate the signalling mechanisms involved.
  
  
  RESULTS
  In CHO-K1 cells, there was no response to β-adrenoceptor agonists. The introduction of β(2)-adrenoceptors and GLUT4 into these cells caused increased glucose uptake in response to β-adrenoceptor agonists. GLUT4 translocation occurred in response to insulin and β(2)-adrenoceptor stimulation, although the key insulin signalling intermediate PKB was not phosphorylated in response to β(2)-adrenoceptor stimulation. Truncation of the C-terminus of the β(2)-adrenoceptor at position 349 to remove known phosphorylation sites for GPCR kinases (GRKs) or at position 344 to remove an additional PKA site together with the GRK phosphorylation sites did not significantly affect cAMP accumulation but decreased β(2)-adrenoceptor-stimulated glucose uptake. Furthermore, inhibition of GRK by transfection of the βARKct construct inhibited β(2)-adrenoceptor-mediated glucose uptake and GLUT4 translocation, and overexpression of a kinase-dead GRK2 mutant (GRK2 K220R) also inhibited GLUT4 translocation. Introducing β(2)-adrenoceptors lacking phosphorylation sites for GRK or PKA demonstrated that the GRK sites, but not the PKA sites, were necessary for GLUT4 translocation.
  
  
  CONCLUSIONS
  Glucose uptake in response to activation of β(2)-adrenoceptors involves translocation of GLUT4 in this model system. The mechanism is dependent on the C-terminus of the β(2)-adrenoceptor, requires GRK phosphorylation sites, and involves a signalling pathway distinct from that stimulated by insulin.
authors: Department of Physiology, The Wenner-Gren Institute, Arrhenius Laboratories F3, Stockholm University, Stockholm, Sweden.
authors: Nodi
authors: N
authors: Dehvari
authors: Dana S
authors: DS
authors: Hutchinson
authors: Julia
authors: J
authors: Nevzorova
authors: Olof S
authors: OS
authors: Dallner
authors: Masaaki
authors: M
authors: Sato
authors: Martina
authors: M
authors: Kocan
authors: Jon
authors: J
authors: Merlin
authors: Bronwyn A
authors: BA
authors: Evans
authors: Roger J
authors: RJ
authors: Summers
authors: Tore
authors: T
authors: Bengtsson
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D000242:Cyclic AMP / Q000378:metabolism; D054768:G-Protein-Coupled Receptor Kinases / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D037342:Pertussis Toxin / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000318:Adrenergic beta-Agonists; D051275:Glucose Transporter Type 4; D007328:Insulin; D010455:Peptides; D018343:Receptors, Adrenergic, beta-2; D011994:Recombinant Proteins; C495692:SLC2A4 protein, human; C445259:beta-adrenergic receptor kinase inhibitory peptide; D000242:Cyclic AMP; D037342:Pertussis Toxin; D011494:Protein Kinases; D054768:G-Protein-Coupled Receptor Kinases; D005947:Glucose