title: N-Glycosylation modulates the membrane sub-domain distribution and activity of glucose transporter 2 in pancreatic beta cells.
abstract: The glucose transporter isoform, GLUT2, -mediated glucose sensing is essential for maintaining normal glucose-stimulated insulin secretion in pancreatic beta cells. We previously reported that GnT-IVa glycosyltransferase is required for the production of an N-glycan structure that acts as a ligand for galectins to form the glycan-galectin lattice that maintains the stable cell surface expression of GLUT2, and cellular glucose transport activity, although the functional relevance of the N-glycosylation of GLUT2 to its membrane sub-domain distribution is not fully understood. In the present study, we demonstrated that disruption of the GLUT2 N-glycan-galectin lattice by the genetic inactivation of GnT-IVa, or by treatment of pancreatic beta cells with competitive glycan mimetics, induced the re-distribution of GLUT2 into the lipid-raft microdomain. This subsequently resulted in the binding of Stomatin to GLUT2 and an attenuation of cellular glucose transport activity. Moreover, disruption of the lipid-raft microdomain by treatment with methyl-β-cyclodextrin caused the GLUT2 to be released from lipid-rafts and reactivation of the cellular glucose transport activity in GnT-IVa deficient beta cells. These results indicate that the membrane sub-domain distribution of GLUT2 is associated with the glucose transport activity of beta cells, in which the GnT-IVa-dependent formation of the N-glycan-galectin lattice plays an important role. This provides a novel pathophysiological insight into the mechanism of beta cell failure in the pathogenesis of type 2 diabetes.
authors.affiliation: Disease Glycomics Team, Systems Glycobiology Research Group, Chemical Biology Department, RIKEN-MAX Planck Joint Research Center, RIKEN Global Research Cluster, Wako, Saitama 351-0198, Japan. kohtsubo@sanken.osaka-u.ac.jp
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Ohtsubo
authors.forename: Shinji
authors.initials: S
authors.lastname: Takamatsu
authors.forename: Congxiao
authors.initials: C
authors.lastname: Gao
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Korekane
authors.forename: Tsutomu M
authors.initials: TM
authors.lastname: Kurosawa
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Taniguchi
mesh_terms: D000818:Animals; D001692:Biological Transport; D001798:Blood Proteins / Q000378:metabolism; D037161:Galectins / Q000378:metabolism; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D051273:Glucose Transporter Type 2 / Q000378:metabolism*; D006031:Glycosylation; D047468:Immunoprecipitation; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D021962:Membrane Microdomains / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics / Q000378:metabolism; D011134:Polysaccharides / Q000378:metabolism; D061251:Primary Cell Culture; D011485:Protein Binding; D047392:beta-Cyclodextrins / Q000494:pharmacology
chemical_list: D001798:Blood Proteins; C488964:Stom protein, mouse; D037161:Galectins; D051273:Glucose Transporter Type 2; D008565:Membrane Proteins; D011134:Polysaccharides; C495682:Slc2a2 protein, mouse; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D017351:N-Acetylglucosaminyltransferases; C038111:alpha-1,3-mannosylglycoprotein beta-1,4-N-acetylglucosaminyltransferase; D005947:Glucose